JP2009302021A - Nonaqueous electrolyte composition and nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte composition which is effective on bulging control of a battery in initial charging and discharging and storage at high temperature, and a nonaqueous electrolyte secondary battery using the nonaqueous electrolyte composition. <P>SOLUTION: The nonaqueous electrolyte composition contains an electrolyte including a cyclic carbonate shown by a general formula (1) and halogenated cyclic carbonate selected from general formulas (2), (3), and (4), and the nonaqueous electrolyte secondary battery includes the nonaqueous electrolyte composition. In the general formula (1), R1 is C<SB>w</SB>H<SB>2w+1</SB>(0≤w≤4), R2 is C<SB>x</SB>H<SB>2x+1</SB>(0≤x≤4), R3 is C<SB>y</SB>H<SB>2y+1</SB>(0≤y≤4), and R4 is C<SB>z</SB>H<SB>2z+1</SB>(0≤z≤4), and 2≤w+x+y+z≤6. R5-R22 are respectively independent hydrogen atoms, halogen atoms, or alkyl groups, and a compound expressed by the general formula (2), (3), or (4) has at least one halogen atom. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte composition and a nonaqueous electrolyte secondary battery using the same, which can suppress expansion during initial charge and storage at high temperature.

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.
Since lithium ion secondary batteries are often used in portable devices, it is necessary to have a sufficient discharge capacity even in a low temperature environment such as outdoors in winter.
Patent Document 1 describes a non-aqueous electrolyte secondary battery using a solvent containing a halogen-substituted derivative of at least one hydrocarbon as an organic solvent, for example, carbon tetrachloride, dichloroethane, and ethylene carbonate or propylene carbonate. It is described that charge / discharge cycle characteristics and storage characteristics are improved.
In Patent Document 2, the solvent of the non-aqueous electrolyte is mainly composed of fluorinated carbonate and chain carbonate, and the volume ratio (fluorinated carbonate: chain carbonate) is in the range of 5:95 to 90:10. And a lithium-ion secondary battery with improved safety against battery destructive testing.
In Patent Document 3, an electrolyte including fluoroethylene carbonate, propylene carbonate, and ethylene carbonate is achieved by a secondary battery including a chlorinated electrolyte solvent while maintaining desirable characteristics that minimize capacity loss and electrolyte decomposition by an electrolyte including fluoroethylene carbonate, propylene carbonate, and ethylene carbonate. There is a description of improving the battery efficiency.
Patent Document 4 discloses an electrochemical system comprising trans-4,5-dialkyl-1,3-dioxolan-2-one; and a lithium salt, in which two alkyl groups independently have 1 to 2 carbons. There is a description that it is a non-aqueous electrolyte for use and has high conductivity at low temperatures and exhibits low irreversibility over a wide range of graphite carbon anodes.
Since the electrolytic solution whose main component of the electrolytic solution solvent is ethylene carbonate has a high melting point of 37 ° C., there is a problem that the electrical conductivity is lowered and the discharge capacity is lowered at a low temperature. In addition to ethylene carbonate, which is a cyclic carbonate, the electrolyte solvent also contains chain carbonates such as diethyl carbonate having a melting point of -43 ° C. The decrease in discharge capacity at low temperatures was inevitable.
On the other hand, since propylene carbonate which is a solvent having a low melting point of −49 ° C. is a cyclic carbonate, it can be easily mixed with ethylene carbonate and the discharge capacity at low temperature can be improved. However, when propylene carbonate is mixed, there is a problem that the initial charge and discharge efficiency is lowered in the battery using graphite as the negative electrode active material. This is thought to be because the propylene carbonate molecules coordinated to the lithium ions are inserted together with the lithium ions between the graphite layers and decompose in the graphite, thereby destroying the crystal structure of the graphite. The insertion of propylene carbonate can be prevented by applying amorphous carbon to the graphite negative electrode by CVD, but there is a problem that the capacity must be sacrificed.
In laminated batteries, laminated polymer batteries are also widely used because the deformation of the laminated battery can be suppressed by swelling the electrolyte in the polymer. However, since the laminate battery has a soft exterior, there is also a problem that the battery tends to swell due to gas generated inside the battery during high temperature storage.

JP-A-3-1555061 JP-A-10-116630 JP 2001-501355 A JP 2002-528882 A

  The present invention has been made in view of such problems, and the purpose thereof is a non-aqueous electrolyte that can achieve both improvement in low-temperature discharge capacity and maintenance of initial charge / discharge efficiency and is effective in suppressing battery swelling during high-temperature storage. The object is to provide a composition and a non-aqueous electrolyte secondary battery using the composition.

In the present invention, by adding two kinds of specific compounds to the electrolyte simultaneously, it is possible to achieve both improvement in initial low temperature discharge capacity and maintenance of initial charge / discharge efficiency, and also effective in suppressing battery swelling during high temperature storage. I found out.
That is, the present invention provides the following non-aqueous electrolyte composition and a non-aqueous electrolyte secondary battery using the same.
[1] An electrolyte salt, a cyclic carbonate represented by the following formula (1), and a halogenated cyclic carbonate represented by at least one selected from the following formulas (2), (3) and (4) A non-aqueous electrolyte composition containing an electrolyte solution.

[In the formula (1), R1 _{is, C w H 2w + 1 (} 0 ≦ w ≦ 4), R2 is _{C x H 2x + 1 (0} ≦ x ≦ 4), R3 _{is, C y H 2y + 1 (} 0 ≦ y ≦ 4) , R4 is C _z H _{2z + 1} (0 ≦ z ≦ 4), and 2 ≦ w + x + y + z ≦ 6.
In formulas (2), (3), and (4), R5 to R22 are each independently a hydrogen atom, a halogen atom, or an alkyl group, and are represented by formula (2), (3), or (4). The compound obtained has at least one halogen atom. ]
[2] A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte composition according to [1] together with a positive electrode and a negative electrode.

  According to the secondary battery of the present invention, the cyclic carbonate represented by the formula (1) (hereinafter also referred to as cyclic carbonate (1). The same applies to the halogenated cyclic carbonate) and the formulas (2) to (2) By using the non-aqueous electrolyte composition containing the electrolytic solution containing the halogenated cyclic carbonate represented by (4), it is possible to achieve both improvement in low-temperature discharge capacity and maintenance of initial charge / discharge efficiency, and during high-temperature storage. A secondary battery effective in suppressing swelling can be provided.

Hereinafter, the nonaqueous electrolyte composition of the present invention will be described in detail. In the present specification, “%” means mass% unless otherwise specified.
The non-aqueous electrolyte composition of the present invention does not contain water or is substantially free of water. This non-aqueous electrolyte composition contains an electrolytic solution containing an electrolyte salt, a cyclic carbonate (1), and halogenated cyclic carbonates (2) to (4).
Since cyclic carbonate (1) has a larger molecule than propylene carbonate, it is less likely to be inserted into graphite and more difficult to decompose than propylene carbonate. Further, the melting point of the cyclic carbonate (1) is considered to be that, for example, butylene carbonate is -55 ° C. and sufficiently lower than ethylene carbonate, and the discharge capacity at low temperature is improved. Furthermore, the cyclic carbonate (1) has an advantage that the swelling during high temperature storage is smaller than that of ethylene carbonate.

In the formula (1), R1 is C _w H _{2w + 1} (0 ≦ w ≦ 4), R2 is C _x H _{2x + 1} (0 ≦ x ≦ 4), R3 is C _y H _{2y + 1} (0 ≦ y ≦ 4), R4 is C _z H _{2z + 1} (0 ≦ z ≦ 4), and 2 ≦ w + x + y + z ≦ 6.
Specific examples of the cyclic carbonate (1) include butylene carbonate [Formula (1-1)], 4,5-dimethyl-1,3-dioxolan-2-one [Formula (1-2)] having the following structure, tert -Butylethylene carbonate [Formula (1-3)] is mentioned, but the present invention is not limited to the above compound, and propylethylene carbonate and the like can also be used.

In formulas (2), (3), and (4), R5 to R22 are each independently a hydrogen atom, a halogen atom, or an alkyl group, and are represented by formulas (2), (3), and (4). The compound has at least one halogen atom. In the formulas (2), (3), and (4), the formula (2) is preferable, and R5-R8 each independently represents a hydrogen atom, a halogen atom (preferably chlorine, fluorine, etc.), or an alkyl group (preferably methyl). The compound represented by the formula (2) has at least one halogen atom, preferably 1 to 2 halogen atoms.
As the halogenated cyclic carbonate (2), 4-fluoro-1,3-dioxolan-2-one (fluoroethylene carbonate) [formula (2-1)], 4,5-difluoro-fluoro-1,3-dioxolane Fluorinated cyclic carbonates such as 2-one (difluoroethylene carbonate) [formula (2-2)], 4-chloro-1,3-dioxolan-2-one (chloroethylene carbonate) [formula (2-3)] And chlorinated cyclic carbonates. Of these, fluoroethylene carbonate is preferred.

The content of the cyclic carbonate (1) in the electrolytic solution is preferably 2 to 10%, more preferably 3 to 8% on the basis of the electrolytic solution, and the halogenated cyclic carbonate (2) to 2% in the electrolytic solution. The content of (4) is preferably 0.5 to 3%, more preferably 0.7 to 1.5%, based on the electrolyte solution.
The cyclic carbonate (1) and the halogenated cyclic carbonates (2) to (4) may be used alone or in combination of two or more.
If it is in the said range, since it is effective for the said two effects of this invention to be exhibited, it is preferable.

  The nonaqueous electrolyte composition in the present invention further contains a solvent other than the above and an electrolyte salt.

(Solvents other than the above)
The solvent other than the above used in the electrolytic solution (hereinafter also referred to as a solvent) 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.

  Examples of the high dielectric constant solvent include cyclic carbonates such as ethylene carbonate and propylene carbonate, lactones such as γ-butyrolactone and γ-valerolactone, lactams such as N-methyl-2-pyrrolidone, and N-methyl-2-oxazolidinone. And a sulfone compound such as tetramethylene sulfone. Of these, cyclic carbonates are preferable, and ethylene carbonate is particularly preferable. The content of the high dielectric constant solvent in the electrolytic solution is preferably in the range of 15% to 50%. 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 non-aqueous electrolyte composition of the present invention can contain a polymer compound that swells with an electrolytic solution and serves as a holding body that holds the electrolytic solution. Thereby, the electrolytic solution is held in the polymer compound, and the electrolytic solution and the polymer compound are integrated to form a gel electrolyte. The non-aqueous electrolyte composition in the non-aqueous electrolyte secondary battery of the present invention can further suppress swelling when stored at a high temperature when a gel electrolyte is formed.

  In the nonaqueous electrolyte composition of the present invention, when a polymer compound is added to the electrolyte solution, the content of the polymer compound in the electrolyte solution is 0.1% by mass or more and 10% by mass or less with respect to the electrolyte solution. It is preferable to be within the range. It is because the said effect will be acquired if it is the said range. Moreover, when apply | coating and using a high molecular compound on both surfaces of a separator, it is preferable to make mass ratio of electrolyte solution and a high molecular compound into the range of 50: 1-10: 1. It is because the higher said effect is acquired by setting it as this range.

  As the polymer compound, polyvinylidene fluoride represented by the following formula (5) or a copolymer thereof can be used. The copolymer of polyvinylidene fluoride is a copolymer of vinylidene fluoride and other monomers, such as a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of chlorotrifluoroethylene, etc. Can be mentioned.

  In said Formula (5), u is an integer of 100-10000.

  Examples of the polymer compound include the above-mentioned polyvinylidene fluoride and copolymers thereof, and ether-based polymer compounds such as polyvinyl formal, polyethylene oxide, and a crosslinked product containing polyethylene oxide represented by the following formula (6), Examples thereof include ester polymer compounds such as polymethacrylate and acrylate polymer compounds shown in (7). A high molecular compound may be used individually by 1 type, and multiple types may be mixed and used for it.

In the above formulas (6) to (7), s and t are each an integer of 100 to 10000, R is C _x H _{2x + 1} O _y (x is 1 to 8, y is 0 to 4. O is present. In this case, R has an ether structure).
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.

  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.

(Positive electrode)
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 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 23B includes, for example, any one or a plurality 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 (Lix (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.

In the non-aqueous electrolyte secondary battery of the present invention, the thickness of one side of the positive electrode active material layer 23B is preferably 40 μm or more and 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. In addition, the positive electrode active material layer 23B is preferably applied and dried so as to be 14 to 30 mg / cm ² per side.

(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, and the negative electrode active material layer 24B and the positive electrode active material layer 23B face each other. Are arranged as follows. 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.

In the non-aqueous electrolyte secondary battery of the present invention, the thickness per one side of the negative electrode active material layer 24B is preferably 40 μm or more and 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. The negative electrode active material layer 24B is preferably applied and dried to 7 to 15 mg / cm ² per side.

(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 synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a porous 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.

(Exterior material)
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.

(Production method)
For example, when a polymer compound is used, 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.
In the above embodiment, the laminated battery is exemplified as the shape of the battery, but it goes without saying that the present invention is not limited to the above. That is, the present invention can be applied to a cylindrical battery, a square battery, and the like.

  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, the case where an electrolytic solution is used as the electrolyte is described, and further, the case where a gel electrolyte in which the electrolytic solution is held in a polymer compound is also described, but other electrolytes are used. 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, a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium has been described. However, the present invention uses a lithium metal as the negative electrode active material, The charge capacity of a so-called lithium metal secondary battery whose capacity is expressed by a capacity component due to precipitation and dissolution of lithium, or a negative electrode material capable of inserting and extracting lithium is 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. .

<Example 1>
First, 94 parts by mass of lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of graphite as a conductive material, and 3 parts by mass 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 mass of graphite as a negative electrode active material and 3 parts by mass 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 electrolyte was ethylene carbonate / cyclic carbonate (1) butylene carbonate / diethyl carbonate / lithium hexafluorophosphate / halogenated cyclic carbonate (2) fluoroethylene carbonate = 30/4/51/14/1 ratio (mass Ratio).
This positive electrode and negative electrode are laminated and wound through a separator made of a microporous polyethylene film having a thickness of 9 μm, and put into a bag made of an aluminum laminate film. After injecting 2 g of the electrolyte into the bag, the bag is heat-sealed to produce a laminated battery. The capacity of this battery is 800 mAh.

<Example 2-4>
A laminate type battery was prepared in the same manner as in Example 1, but the compounds shown in Table 1 were used as the cyclic carbonate (1). The capacity of this battery is 800 mAh.

<Examples 5 and 6>
A laminate type battery was prepared in the same manner as in Example 1, but the compounds shown in Table 1 were used as the halogenated cyclic carbonate (2). The capacity of this battery is 800 mAh.

<Example 7>
A laminate type battery was prepared in the same manner as in Example 1, but the amount shown in Table 1 was used as the addition amount of the cyclic carbonate (1). The capacity of this battery is 800 mAh.

<Example 8>
A laminate type battery was prepared in the same manner as in Example 1, but the amounts shown in Table 1 were used as the addition amounts of cyclic carbonate (1) and cyclic carbonate (2). The capacity of this battery is 800 mAh.

<Comparative Example 1>
A laminate type battery was prepared in the same manner as in Example 1, but neither cyclic carbonate (1) nor halogenated cyclic carbonate (2) was mixed, and the amount of ethylene carbonate was increased accordingly. The capacity of this battery is 800 mAh.

<Comparative Example 2>
A laminate type battery was prepared in the same manner as in Example 1, but the cyclic carbonate (1) was not mixed and the amount of ethylene carbonate was increased accordingly. The capacity of this battery is 800 mAh.

<Comparative Example 3>
A laminate type battery was prepared in the same manner as in Example 1, but the halogenated cyclic carbonate (2) was not mixed, and the amount of ethylene carbonate was increased accordingly. The capacity of this battery is 800 mAh.

<Comparative example 4>
A laminate type battery was prepared in the same manner as in Example 1, but propylene carbonate having 4 carbon atoms was mixed in place of the cyclic carbonate (1). The capacity of this battery is 800 mAh.

<Example 9>
A laminate type battery was prepared in the same manner as in Example 1, but a separator having a thickness of 7 μm and a coating of 2 μm of polyvinylidene fluoride on both sides was used. The capacity of this battery is 800 mAh.

<Example 10-12>
A laminate type battery was prepared in the same manner as in Example 9, but the compounds shown in Table 1 were used as the cyclic carbonate (1). The capacity of this battery is 800 mAh.

<Examples 13 and 14>
A laminate type battery was prepared in the same manner as in Example 9, but the compounds shown in Table 1 were used as the halogenated cyclic carbonate (2). The capacity of this battery is 800 mAh.

<Comparative Example 5>
A laminate type battery was prepared in the same manner as in Example 9, but neither cyclic carbonate (1) nor halogenated cyclic carbonate (2) was mixed, and the amount of ethylene carbonate was increased accordingly. The capacity of this battery is 800 mAh.

<Comparative Example 6>
A laminate type battery was prepared in the same manner as in Example 9, but the cyclic carbonate (1) was not mixed and the amount of ethylene carbonate was increased accordingly. The capacity of this battery is 800 mAh.

<Comparative Example 7>
A laminate type battery was prepared in the same manner as in Example 9, but the halogenated cyclic carbonate (2) was not mixed and the amount of ethylene carbonate was increased accordingly. The capacity of this battery is 800 mAh.

<Comparative Example 8>
A laminate type battery was prepared in the same manner as in Example 9, but propylene carbonate having 4 carbon atoms was mixed in place of the cyclic carbonate (1). The capacity of this battery is 800 mAh.

<Example 15>
A laminate type battery was prepared in the same manner as in Example 9, but the amount shown in Table 1 was used as the addition amount of the cyclic carbonate (1). The capacity of this battery is 800 mAh.

<Example 16>
A laminate type battery was prepared in the same manner as in Example 9, but the amounts shown in Table 1 were used as the addition amounts of cyclic carbonate (1) and cyclic carbonate (2). The capacity of this battery is 800 mAh.

The performance of the battery was evaluated as follows.
Table 1 shows the initial charge / discharge efficiency when the battery was charged for 4 hours at 800 mA in a 23 ° C. environment with 4.2 V as the upper limit and then discharged at a constant current of 160 mA with 3 V as the lower limit. Moreover, after charging for 3 hours with 4.2 V as the upper limit at 800 mA in a 23 ° C. environment, the ratio of the discharge capacity when discharging at a constant current of −20 ° C. and 23 ° C. with 3 V as the lower limit at 400 mA is −20 ° C./23° C. It shows in Table 1 as a maintenance rate (%). Further, Table 1 shows changes in battery thickness when swollen at 85 ° C. for 4 hours after charging for 3 hours at 800 mA in a 23 ° C. environment with 4.2 V as the upper limit. The swelling (%) is a value calculated using the battery thickness before charging as the denominator and the thickness increased after storage as the numerator.

From Table 1, the following can be understood.
In Examples, Comparative Examples 1 and 5 in which the cyclic carbonate (1) and the halogenated cyclic carbonate (2) are not used by using the cyclic carbonate (1) and the halogenated cyclic carbonate (2) within the scope of the present invention in combination. Compared with Comparative Examples 2 and 6 in which the cyclic carbonate (2) is used but the cyclic carbonate (1) is not used, the maintenance rate of −20 ° C./23° C. is improved. Further, in the examples, the swelling during storage at 85 ° C. and the maintenance rate of −20 ° C./23° C. are improved as compared with Comparative Examples 2 and 6. In the examples, the cyclic carbonate (1) is used in combination with the cyclic carbonate (1) within the scope of the present invention and the halogenated cyclic carbonate (2), but the comparative example does not use the halogenated cyclic carbonate (2). 3, 7 and the halogenated cyclic carbonate (2) are used, but the initial charge / discharge efficiency is improved as compared with Comparative Examples 4 and 8, which are not the cyclic carbonate (1) of the present application even if the cyclic carbonate is used. .
In the examples, when a polymer compound is used, the swelling particularly at high temperature storage is further improved.

  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 (7)

An electrolytic solution comprising an electrolyte salt, a cyclic carbonate represented by the following formula (1), and a halogenated cyclic carbonate represented by at least one selected from the following formulas (2), (3) and (4) A non-aqueous electrolyte composition comprising:

[In the formula (1), R1 _{is, C w H 2w + 1 (} 0 ≦ w ≦ 4), R2 is _{C x H 2x + 1 (0} ≦ x ≦ 4), R3 _{is, C y H 2y + 1 (} 0 ≦ y ≦ 4) , R4 is C _z H _{2z + 1} (0 ≦ z ≦ 4), and 2 ≦ w + x + y + z ≦ 6.
In formulas (2), (3), and (4), R5 to R22 are each independently a hydrogen atom, a halogen atom, or an alkyl group, and are represented by formula (2), (3), or (4). The compound obtained has at least one halogen atom. ]   The non-aqueous electrolyte composition according to claim 1, wherein the cyclic carbonate represented by the formula (1) is butylene carbonate.   The non-aqueous electrolyte composition according to claim 1, wherein the halogenated cyclic carbonate represented by the formula (2) is fluoroethylene carbonate.   The nonaqueous electrolyte composition according to claim 1, comprising a polymer compound.   The non-aqueous electrolyte composition according to claim 4, wherein the polymer compound is polyvinylidene fluoride.   A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte composition according to claim 1 together with a positive electrode and a negative electrode.   The nonaqueous electrolyte secondary battery according to claim 6 accommodated in an exterior member made of a laminate film.

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