JP5863631B2 - Method for producing non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method for manufacturing a nonaqueous electrolyte secondary battery.

  Since commercialization in 1991, lithium-ion batteries have steadily expanded the market as secondary batteries for portable devices such as mobile phones and game machines, and have become one of the most important secondary batteries. In recent years, a wide range of practical applications have been studied as power sources for power storage systems combined with solar cells, wind power generation, smart grids, etc., and power sources for electric vehicles, and the market is steadily expanding.

  As described above, the lithium-ion battery whose market is expanding has various demands depending on its application. Especially in mobile devices such as mobile phones and portable game machines, as a result of the advancement of high performance and multiple functions, power consumption has increased and there has been a strong demand for higher charge / discharge capacity of lithium ion batteries. It has been.

  In order to meet such demands, development of lithium ion batteries using silicon (Si) as a negative electrode material has been actively promoted. Si has a theoretical capacity of 4200 Ah / kg, which is 10 times or more that of the currently mainstream carbon (C) negative electrode material, and a significant improvement in capacity can be expected. It has been confirmed that when Si is actually used as the negative electrode material, at least the initial charge / discharge capacity is greatly improved. However, Si as a negative electrode material has a problem that the volume expands to 4 times or more during charging. By this charge and discharge, Si repeatedly expands and contracts, pulverizes and electrical coupling is broken, and the initial capacity is rapidly reduced. In order to solve this problem, attempts have been made to pulverize Si crystals (Non-patent Document 1) and attempts have been made to add various additives such as fluoroethylene carbonate (FEC) and vinylene carbonate (VC) to the electrolyte. (Patent Document 1).

JP 2008-210618A

Proceedings of the 50th Battery Conference, p.60 (2009)

  However, although the charge and discharge cycle characteristics of the lithium ion battery are improved to some extent by the pulverization of the Si crystal described in Non-Patent Document 1 and the addition of the additive described in Patent Document 1, sufficient performance is still obtained. Absent.

  The present invention has been made to solve the above problems, and provides a non-aqueous electrolyte secondary battery having a high capacity and excellent charge / discharge cycle characteristics.

  A method for producing a non-aqueous electrolyte secondary battery according to the present invention is a method for producing a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, wherein lithium is formed on the positive electrode and the negative electrode current collector. A battery assembly step of inserting a negative electrode in which a negative electrode mixture layer containing a material capable of alloying is formed, into a package body so as to face each other through a separator, and a cyclic carbonate substituted with halogen in the package body A primary charging / discharging step of injecting a first electrolytic solution containing 1 to 9 times and charging and discharging a cyclic carbonate having a carbon-carbon unsaturated bond in the outer package. And a secondary charging / discharging step of charging / discharging by injecting the electrolyte solution 2.

  According to the present invention, a non-aqueous electrolyte secondary battery having a high capacity and excellent charge / discharge cycle characteristics can be provided.

FIG. 1A is a plan view showing an example of a nonaqueous electrolyte secondary battery according to the present invention, and FIG. 1B is a cross-sectional view of FIG. 1A. FIG. 2 is a perspective view of the nonaqueous electrolyte secondary battery shown in FIGS. 1A and 1B. FIG. 3 is a plan view showing another example of the nonaqueous electrolyte secondary battery according to the present invention.

  The method for producing a non-aqueous electrolyte secondary battery of the present invention is a method for producing a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator, and lithium and an alloy are formed on the positive electrode and the negative electrode current collector. A battery assembly step of inserting a negative electrode formed with a negative electrode mixture layer containing a material that can be made into an exterior body with a separator interposed therebetween, and a halogen-substituted cyclic carbonate in the exterior body A first charging / discharging step of injecting the first electrolytic solution containing and charging / discharging at a frequency of 1 to 9 times, and a second containing a cyclic carbonate having a carbon-carbon unsaturated bond in the outer package. And a secondary charging / discharging step of charging / discharging by injecting the electrolyte solution.

  By performing the primary charge / discharge step and the secondary charge / discharge step, a nonaqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics can be provided even when a material capable of being alloyed with lithium is used as the negative electrode active material. In addition, by using a material that can be alloyed with lithium as the negative electrode active material, a high-capacity nonaqueous electrolyte secondary battery can be provided.

  Hereinafter, the nonaqueous electrolyte secondary battery according to the present invention and the manufacturing method thereof will be described more specifically.

(Method for producing non-aqueous electrolyte secondary battery)
First, the manufacturing method of the nonaqueous electrolyte secondary battery of this invention is demonstrated.

  A non-aqueous electrolyte secondary battery manufacturing method of the present invention is a method of manufacturing a non-aqueous electrolyte secondary battery according to the present invention described later, and can be alloyed with lithium on a positive electrode and a negative electrode current collector. A battery assembly step of inserting a negative electrode in which a negative electrode mixture layer containing a material is formed into an exterior body so as to face each other with a separator interposed therebetween; and a first structure including a halogen-substituted cyclic carbonate in the exterior body A primary charging / discharging process in which the electrolytic solution is charged and discharged at a frequency of 1 to 9 times, and a second electrolytic solution containing a cyclic carbonate having a carbon-carbon unsaturated bond in the outer package. And a secondary charge / discharge step of charging and discharging by injecting.

  By performing the primary charge / discharge step and the secondary charge / discharge step, a nonaqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics can be provided even when a material capable of being alloyed with lithium is used as the negative electrode active material. This is because the negative electrode active material reacts with the halogen-substituted cyclic carbonate in the primary charge / discharge step to form an oxide film on the surface of the negative electrode active material. Since the cyclic carbonate having a saturated bond is decomposed and an organic film is further formed on the surface of the negative electrode active material on which the oxide film is formed, the organic film functions as a protective film for the oxide film and stably functions as the negative electrode. It becomes possible to cover the active material, and the reaction between the negative electrode active material and the non-aqueous electrolyte is suppressed. As a result, the high-resistance reaction product generated by the reaction between the negative electrode active material and the non-aqueous electrolyte is reduced, and charge and discharge are reduced. It is thought that the cycle characteristics are improved.

  The battery assembly process is not particularly limited, and may be performed by a normal battery assembly process. However, the negative electrode used is a negative electrode in which a negative electrode mixture layer containing a material that can be alloyed with lithium is formed on a negative electrode current collector. Thereby, a high capacity non-aqueous electrolyte secondary battery can be provided.

  As said 1st electrolyte solution used at the said primary charging / discharging process, the non-aqueous electrolyte solution containing the halogen-substituted cyclic carbonate is used. By injecting the first electrolyte solution into the outer package and performing charge / discharge at a frequency of 1 to 9 times, an oxide film is formed on the surface of the negative electrode active material, and the nonaqueous electrolyte and the negative electrode Reaction with the active material can be suppressed.

  Moreover, as said halogen-substituted cyclic carbonate, the compound represented by following General formula (1) can be used.

In the general formula (1), R ¹ , R ² , R ³ and R ⁴ represent hydrogen, a halogen element or an alkyl group having 1 to 10 carbon atoms, and a part or all of the hydrogen of the alkyl group is halogen. may be substituted with an element, at least one of R ^1, R ^2, R ³ and R ⁴ are halogen, R ^1, R ^2, R ³ and R ⁴ are different from each Two or more may be the same. When R ¹ , R ² , R ³ and R ⁴ are alkyl groups, the smaller the number of carbon atoms, the better. As the halogen element, fluorine is particularly preferable.

  Among the cyclic carbonates substituted with such a halogen element, 4-fluoro-1,3-dioxolan-2-one (FEC) is particularly preferable.

  The first electrolytic solution is obtained by adding a halogen-substituted cyclic carbonate to a nonaqueous electrolytic solution in which a lithium salt is dissolved in an organic solvent. The addition amount of the halogen-substituted cyclic carbonate in the first electrolytic solution may be 0.3 volume% or more and 30 volume% or less with respect to the total volume of the first electrolytic solution.

Examples of the first lithium salt used in the non-aqueous electrolyte solution of the electrolyte solution, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6 inorganic lithium salts such _{as, LiCF 3 SO 3, LiCF 3} CO 2, Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (2 ≦ n ≦ 7), LiN (RfOSO ₂ ) ₂ [wherein Rf is a fluoroalkyl group] or an organic lithium salt can be used.

  The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 to 1.5 mol / L, and more preferably 0.9 to 1.25 mol / L.

  Examples of the organic solvent used in the non-aqueous electrolyte include cyclic carbonates such as ethylene carbonate and propylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; Cyclic esters such as butyrolactone; chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; acetonitrile, propionitrile, methoxy Nitriles such as propionitrile; sulfites such as ethylene glycol sulfite and the like can be mentioned, and these can be used in combination of two or more.

  The amount of the first electrolytic solution injected into the exterior body is not particularly limited, and may be an amount that the entire electrode group in the exterior body is immersed.

  As said 2nd electrolyte solution used at the said secondary charging / discharging process, the non-aqueous electrolyte solution containing the cyclic carbonate which has a carbon-carbon unsaturated bond is used. After the primary charge / discharge step, by further injecting the second electrolyte solution into the outer package and performing charge / discharge, an organic film is further formed on the surface of the oxide film of the negative electrode active material, Since the organic coating functions as a protective film for the oxide coating, the reaction between the non-aqueous electrolyte and the negative electrode active material can be stably suppressed. Therefore, it is considered that the charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery are improved.

  Moreover, as a cyclic carbonate which has the said carbon-carbon unsaturated bond, vinylene carbonate (VC) etc. can be used, for example.

  The second electrolytic solution is obtained by adding a cyclic carbonate having a carbon-carbon unsaturated bond to a nonaqueous electrolytic solution in which a lithium salt is dissolved in an organic solvent. The addition amount of the cyclic carbonate having a carbon-carbon unsaturated bond in the second electrolytic solution may be 10% by volume or more and 60% by volume or less with respect to the total volume of the second electrolytic solution.

  As the nonaqueous electrolytic solution used for the second electrolytic solution, the same nonaqueous electrolytic solution used for the first electrolytic solution can be used. The amount of the second electrolytic solution injected into the outer package is not particularly limited, and the carbon-carbon unsaturated bond in the nonaqueous electrolytic solution in the outer package after the second electrolytic solution is injected. What is necessary is just to set it as the quantity from which content of the cyclic carbonate to have will be 0.1 volume% or more and 10 volume% or less with respect to the whole volume of a non-aqueous electrolyte.

  The number of times of charging / discharging in the secondary charging / discharging step is not particularly limited, and may be performed once or more in consideration of production efficiency.

  Since the non-aqueous electrolyte after the secondary charge / discharge step can be used as it is as the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery according to the present invention, the exterior body is completely sealed after the secondary charge / discharge step. Thus, the nonaqueous electrolyte secondary battery according to the present invention can be manufactured.

(Non-aqueous electrolyte secondary battery)
Next, the nonaqueous electrolyte secondary battery according to the present invention will be described. The nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator.

[Negative electrode]
For the negative electrode, for example, a negative electrode active material, a binder, and a negative electrode mixture layer containing a conductive auxiliary agent as required are formed on one or both sides of a current collector, or a negative electrode active material What formed by the vacuum film-forming etc. directly on the single side | surface or both surfaces of a collector can be used.

<Negative electrode active material>
As the negative electrode active material, a material that can be alloyed with lithium (Li) is used. Examples of materials that can be alloyed with Li include simple elements that can be alloyed with Li, such as Ag, Au, Zn, Cd, Al, Ga, In, Tl, Ge, Pb, Si, Sn, Sb, and Bi. And alloys of these elements can be used. As the elemental element that can be alloyed with Li, Si and Sn are particularly preferable because they have a large storage amount of Li.

In addition, as a material that can be alloyed with Li, a material containing Si as a constituent element can be used. The material containing Si as a constituent element is particularly preferable since it has a large amount of occlusion of Li and has no environmental problems. Examples of the material containing Si as a constituent element include materials of Si and alloys of elements other than Si such as Co, Ni, Ti, Fe, and Mn, and materials such as Si oxides. A material containing Si and oxygen (O) represented by the formula SiO _x (where 0.5 ≦ x ≦ 1.5) as constituent elements is preferably used. The alloy of Si and an element other than Si may be a single solid solution or an alloy composed of a plurality of phases of a single Si phase and a Si alloy phase.

Further, the SiO _x is not limited to the Si oxide, and may contain a Si microcrystalline phase or an amorphous phase. In this case, the atomic ratio of Si and O is determined by the Si microcrystalline phase. Alternatively, the ratio includes amorphous phase Si. In other words, the material expressed by SiO _x, for example, a SiO ₂ matrix of amorphous, Si (e.g., microcrystalline Si) is include the dispersed structure, the SiO ₂ in the amorphous In addition, it is only necessary that the atomic ratio x satisfies 0.5 ≦ x ≦ 1.5 by adding Si dispersed therein. For example, in the case of a material in which Si is dispersed in an amorphous SiO ₂ matrix and the material has a molar ratio of SiO ₂ and Si of 1: 1, x = 1, so in the present invention, it is expressed as SiO. The In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si Can be confirmed.

The average particle diameter of the SiO _x is preferably about 0.5 to 10 μm as the average particle diameter D50 in order to enhance the effect of compounding with the carbon material described later and prevent miniaturization during charge and discharge. Used. Here, D50 means the value of the particle diameter at a volume-based integrated fraction of 50%. As a method for measuring the particle diameter, for example, a laser diffraction / scattering method or the like can be used. The laser diffraction / scattering method is a particle diameter distribution measuring method using a scattering intensity distribution detected by irradiating a measurement target substance dispersed in a liquid phase such as water with laser light. As a particle size distribution measuring apparatus using a laser diffraction / scattering method, for example, “Microtrac HRA” manufactured by Nikkiso Co., Ltd. can be used.

If the crystallite diameter of the SiO _x Si (microcrystalline Si) itself is too large, the Si particles themselves or the surrounding matrix (SiO ₂ or the like) may expand or contract as the battery is repeatedly charged and discharged. It will not endure the stress and will crack, causing the charge / discharge cycle characteristics of the battery to deteriorate. Therefore, in the SiO _x Si, the crystallite diameter determined by using the Scherrer equation from the half width of the (220) plane of Si obtained by the X-ray diffraction method is preferably 50 nm or less, and 40 nm or less. It is more preferable that it is 20 nm or less.

Since the above SiO _x has poor conductivity, when it is used as a negative electrode active material, a conductive material (conductive aid) is used from the viewpoint of ensuring good battery characteristics, and excellent conductivity is provided in the negative electrode. A network needs to be formed. Therefore, when using the SiO _x as the negative electrode active material, the SiO _x is a composite obtained by combining with a conductive material such as a carbon material, or the both are mixed to form the SiO _x and the conductive material. It is preferable to use a mixture of When the SiO _x and the conductive material are combined, a conductive network in the negative electrode is formed better than when a mixture obtained by simply mixing the two is used, and the load characteristics of the battery can be improved. .

Examples of the composite of SiO _x and a conductive material include a composite in which the surface of SiO _x particles is coated with a conductive material (preferably a carbon material), and SiO _x together with a conductive material (preferably a carbon material). The granulated body etc. which were granulated are mentioned.

Examples of the conductive material include graphite, low crystalline carbon, carbon nanotube, vapor grown carbon fiber, and the like, and in particular, fibrous or coiled carbon material, carbon black (acetylene black, ketjen black) At least one material selected from the group consisting of artificial graphite, graphitizable carbon, and non-graphitizable carbon is preferable. The fibrous or coiled carbon material is preferable in that it easily forms a conductive network and has a large surface area. The carbon black (including acetylene black and ketjen black), graphitizable carbon, and non-graphitizable carbon have high electrical conductivity and high liquid retention, and the SiO _x particles expand and Even if it shrinks, it is preferable in that it has the property of easily maintaining contact with the particles.

As the conductive material, it may be used in combination graphitic carbon material for use with SiO _x as the negative electrode active material. Graphite carbon materials, like carbon black, have high electrical conductivity and high liquid retention, and even when SiO _x particles expand or contract, they maintain contact with the particles. Since it has an easy property, it can be preferably used for forming a complex with SiO _x .

<Binder>
Examples of the binder used in the negative electrode mixture layer include starch, polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, and other polysaccharides and modified products thereof; polyvinyl chloride, Thermoplastic resins such as polyvinylpyrrolidone (PVP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polyamideimide, polyamide, etc .; modified products thereof; polyimide; ethylene-propylene-diene terpolymer ( EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), butadiene rubber, polybutadiene, fluororubber, polyethylene oxide, etc. Modified product of al; and the like, to these may be used alone or in combination of two or more.

  A conductive material may be further added to the negative electrode mixture layer as a conductive additive. The conductive material is not particularly limited as long as it does not cause a chemical change in the nonaqueous electrolyte secondary battery. For example, graphite (graphitic carbon material) such as natural graphite (flaky graphite, etc.), artificial graphite, etc. ); Carbon black such as acetylene black, ketjen black (trade name), channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber, metal fiber; aluminum powder, nickel powder, copper powder, silver powder Metal powders such as carbon fluoride; zinc oxide; conductive whiskers made of potassium titanate, etc .; conductive metal oxides such as titanium oxide; polyphenylene derivatives (described in JP-A-59-20971), etc. Organic conductive materials; and the like. These may be used alone or in combination of two or more. Among these, highly conductive graphite and carbon black excellent in liquid absorption are preferable, and ketjen black and acetylene black are more preferable. Further, the form of the conductive auxiliary agent is not limited to primary particles, and secondary aggregates and aggregated forms such as chain structures can also be used. Such an assembly is easier to handle and has better productivity.

<Current collector>
As the current collector used for the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal, or the like can be used. Usually, a copper foil is used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is 5 μm in order to ensure mechanical strength. Is desirable.

<Method for producing negative electrode>
The negative electrode is, for example, a paste or slurry in which the above-described negative electrode active material and binder and, if necessary, a conductive assistant are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water. A negative electrode mixture-containing composition can be prepared, applied to one or both sides of a current collector, dried, and then subjected to a calendering process as necessary. In addition, for example, in the case of using a single element that can be alloyed with Li as the negative electrode active material, the negative electrode is formed by depositing these elements on one side or both sides of the current collector by a vacuum film forming method such as sputtering or vapor deposition. Thus, a negative electrode active material layer may be formed. The manufacturing method of a negative electrode is not necessarily restricted to said manufacturing method, It can also manufacture with another manufacturing method.

<Negative electrode mixture layer>
When forming the said negative mix layer by the said coating method, it is preferable that the total amount of a negative electrode active material shall be 80-99 mass%, and the quantity of a binder shall be 1-20 mass%. In addition, when a conductive material is separately used as a conductive auxiliary agent, these conductive materials in the negative electrode mixture layer are used in such a range that the total amount of the negative electrode active material and the binder amount satisfy the above-described preferable values. It is preferable. The thickness of the negative electrode mixture layer is preferably 50 to 400 μm, for example. By setting the thickness of the negative electrode mixture layer in the above range and increasing the thickness as much as possible, the capacity of the nonaqueous electrolyte secondary battery can be increased.

<Negative electrode active material layer>
Moreover, when forming the said negative electrode active material layer by the said vacuum film-forming method, it is preferable that the thickness of a negative electrode active material layer shall be 100 nm or less per single side | surface.

[Positive electrode]
As the positive electrode, for example, one having a structure in which a positive electrode mixture layer containing a positive electrode active material, a conductive additive, a binder and the like is provided on one side or both sides of a current collector can be used.

<Positive electrode active material>
The positive electrode active material used for the positive electrode is not particularly limited, and a generally usable active material such as a lithium-containing transition metal oxide may be used. Specific examples of the lithium-containing transition metal oxide include, for example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , and Li _x Co _y M _1-y O _2. , etc. _{Li x Ni 1-y M y} O 2, Li x Mn y Ni z Co 1-yz O 2, Li x Mn 2 O 4, Li x Mn 2-y M y O 4 are exemplified. However, in each structural formula above, M is at least one metal element selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, Al, Ti, Ge, and Cr, and 0 ≦ x ≦ 1.1, 0 <y <1.0, 2.0 <z <1.0.

<Binder>
As the binder used for the positive electrode, any of a thermoplastic resin and a thermosetting resin can be used as long as it is chemically stable in the battery. For example, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), styrene-butadiene rubber (SBR), tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoro Ethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), propylene- Tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, Len - methyl acrylate copolymer, ethylene - one or more Na ion crosslinked body and the like of the methyl methacrylate copolymer and their copolymers can be used.

<Conductive aid>
As a conductive support agent used for the said positive electrode, what is chemically stable should just be in a battery. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black (trade name), channel black, furnace black, lamp black and thermal black; conductive fiber such as carbon fiber and metal fiber; aluminum Metal powders such as powders; Fluorinated carbon; Zinc oxide; Conductive whiskers made of potassium titanate; Conductive metal oxides such as titanium oxide; Organic conductive materials such as polyphenylene derivatives, etc. You may use independently and may use 2 or more types together. Among these, highly conductive graphite and carbon black excellent in liquid absorption are preferable. Further, the form of the conductive auxiliary agent is not limited to primary particles, and secondary aggregates and aggregated forms such as chain structures can also be used. Such an assembly is easier to handle and has better productivity.

<Current collector>
The current collector used for the positive electrode can be the same as that used for the positive electrode of a conventionally known lithium ion secondary battery. For example, an aluminum foil having a thickness of 10 to 30 μm is preferable. .

<Method for producing positive electrode>
The positive electrode is prepared, for example, as a paste-like or slurry-like positive electrode mixture-containing composition in which the above-described positive electrode active material, conductive additive and binder are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP). And after apply | coating this to the single side | surface or both surfaces of a collector and drying, it can manufacture through the process of giving a calendar process as needed. The manufacturing method of a positive electrode is not necessarily restricted to said method, It can also manufacture with another manufacturing method.

<Positive electrode mixture layer>
In the positive electrode mixture layer, it is preferable that the total amount of the positive electrode active material is 92 to 95% by mass, the amount of the conductive additive is 3 to 6% by mass, and the amount of the binder is 3 to 6% by mass. The thickness of the positive electrode mixture layer is preferably 70 to 300 μm per one side of the current collector after the calendar treatment. By setting the thickness of the positive electrode mixture layer in the above range and making it as thick as possible, the capacity of the nonaqueous electrolyte secondary battery can be increased.

[Non-aqueous electrolyte]
As said non-aqueous electrolyte, as above-mentioned, the non-aqueous electrolyte after the secondary charging / discharging process of this invention can be used as it is.

[Separator]
The separator preferably has a property of blocking its pores (that is, a shutdown function) at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower). A separator used in a normal lithium ion secondary battery or the like, for example, a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous film constituting the separator may be, for example, one using only PE or one using PP, or a laminate of a PE microporous film and a PP microporous film. There may be.

[Battery form]
Examples of the form of the non-aqueous electrolyte secondary battery according to the present invention include a cylindrical shape (a square cylindrical shape, a cylindrical shape, etc.) using a steel can, an aluminum can, or the like as an exterior body. Moreover, it can also be set as the soft package battery which used the laminated film which vapor-deposited the metal as an exterior body.

  1A is a plan view showing an example of a nonaqueous electrolyte secondary battery according to the present invention, and FIG. 1B is a cross-sectional view of FIG. 1A. FIG. 2 is a perspective view of the nonaqueous electrolyte secondary battery shown in FIGS. 1A and 1B.

  As shown in FIG. 1B, the positive electrode 1 and the negative electrode 2 are spirally wound through a separator 3 and then pressed so as to be flattened to form a flat wound electrode body 6 as a rectangular tube-shaped exterior. The can 4 is accommodated together with a non-aqueous electrolyte. However, in FIG. 1B, in order to avoid complication, the metal foil, the non-aqueous electrolyte, and the like used as the current collector used in the production of the positive electrode 1 and the negative electrode 2 are not shown, and the winding electrode body 6 The inner peripheral portion is not cross-sectional.

  The outer can 4 is made of an aluminum alloy and constitutes an outer casing of the battery. The outer can 4 also serves as a positive electrode terminal. And the insulator 5 which consists of PE sheets is arrange | positioned in the bottom part of the armored can 4, From the wound electrode body 6 which consists of the positive electrode 1, the negative electrode 2, and the separator 3, it connects to each one end of the positive electrode 1 and the negative electrode 2 The positive electrode lead body 7 and the negative electrode lead body 8 thus drawn are drawn out. A stainless steel terminal 11 is attached to a sealing lid plate 9 made of aluminum alloy for sealing the opening of the outer can 4 via a PP insulating packing 10. An insulator 12 is attached to the terminal 11. A stainless steel lead plate 13 is attached via

  And this cover plate 9 is inserted in the opening part of the armored can 4, and the opening part of the armored can 4 is sealed by welding the junction part of both, and the inside of a battery is sealed. In the battery shown in FIGS. 1A and 1B, a non-aqueous electrolyte inlet 14 is provided in the lid plate 9, and a sealing member is inserted into the non-aqueous electrolyte inlet 14, for example, with a laser. The battery is hermetically sealed by welding or the like, so that the battery is sealed. Therefore, in the batteries of FIGS. 1A, 1B and 2, the non-aqueous electrolyte inlet 14 is actually a non-aqueous electrolyte inlet and a sealing member. An electrolyte inlet 14 is shown. Further, the lid plate 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the temperature of the battery rises.

  In the battery, by directly welding the positive electrode lead body 7 to the lid plate 9, the outer can 4 and the lid plate 9 function as a positive electrode terminal, and the negative electrode lead body 8 is welded to the lead plate 13. The terminal 11 functions as a negative electrode terminal by connecting the negative electrode lead body 8 and the terminal 11 to each other. However, depending on the material of the outer can 4, the sign may be reversed.

  FIG. 3 is a plan view showing another example of the nonaqueous electrolyte secondary battery according to the present invention. In FIG. 3, a nonaqueous electrolyte secondary battery 20 according to the present invention has a positive electrode, a negative electrode, and a nonaqueous electrolyte accommodated in an outer package 21 made of an aluminum laminate film that is rectangular in plan view. The positive external terminal 22 and the negative external terminal 23 are drawn from the same side of the exterior body 21.

  Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples.

Example 1
<Preparation of positive electrode>
First, LiNi _0.6 Co _0.2 Mn _0.2 O _{2 as} a positive electrode active material: 88 parts by mass, artificial graphite as a conductive auxiliary agent: 1 part by mass and Ketjen black: 1 part by mass, PVDF as a binder: 10 parts by mass Were mixed so as to be uniform using NMP as a solvent to prepare a positive electrode mixture-containing paste. Next, the positive electrode mixture-containing paste is applied to one side of an aluminum foil having a thickness of 15 μm while adjusting the thickness, dried, and then subjected to a calendering process so that the total thickness of the positive electrode becomes 17 μm. The thickness of the positive electrode mixture layer was adjusted and punched to a diameter of 13 mm to produce a positive electrode.

<Production of negative electrode>
A Si thin film was formed on a copper foil having a thickness of 8 μm by a high frequency magnetron sputtering method. The thickness of the Si thin film was 100 nm. The copper foil on which this Si thin film was formed was punched out to a diameter of 14 mm to produce a negative electrode.

<Preparation of the 1st electrolyte solution for primary charging / discharging processes>
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ as a lithium salt at a concentration of 1 mol / L in a mixture of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1. 4-Fluoro-1,3-dioxolan-2-one (FEC) is mixed with this non-aqueous electrolyte so that the volume ratio of non-aqueous electrolyte: FEC = 9: 1. Prepared.

<Temporary assembly of model cell: Primary injection>
The positive electrode and the negative electrode were laminated through a separator made of a microporous polyethylene film having a thickness of 16 μm and a porosity of 50% to produce a laminated electrode body, and this laminated electrode body was housed in an exterior body. Thereafter, the first electrolytic solution was primarily injected into the outer package to produce a model cell. “HS flat cell” manufactured by Hosen Co., Ltd. was used for the exterior body.

<Primary charge / discharge process: Surface oxidation treatment>
The model cell is charged at a constant current of 0.25 mA / cm ² until the battery voltage reaches 4.2 V, and then charged at a constant voltage of 4.2 V until the current value reaches 0.025 mA / cm ^2. Then, constant current discharge (discharge end voltage: 2.7 V) was performed at 0.25 mA / cm ² . This was regarded as one cycle, and charging / discharging was performed only for one cycle.

<Preparation of second electrolytic solution for secondary charge / discharge process>
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ as a lithium salt at a concentration of 1 mol / L in a mixture of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1. Vinylene carbonate (VC) was further mixed with this non-aqueous electrolyte so that the volume ratio was non-aqueous electrolyte: VC = 1: 1, thereby preparing a second electrolyte.

<Assembly of model cell: Secondary injection>
The model cell in which the primary charge / discharge process has been completed is opened, and the second electrolytic solution is secondarily injected into the outer package so that the volume ratio of the nonaqueous electrolytic solution and VC in the model cell is non- A test cell was prepared by adjusting the water electrolyte: VC = 9: 1.

(Example 2)
A test model cell was produced in the same manner as in Example 1 except that the number of charge / discharge cycles in the primary charge / discharge process was set to 5 cycles.

(Example 3)
A test model cell was produced in the same manner as in Example 1 except that the number of times of charge / discharge in the primary charge / discharge process was set to 7 cycles.

Example 4
A test model cell was produced in the same manner as in Example 1 except that the number of times of charge / discharge in the primary charge / discharge process was set to 9 cycles.

(Example 5)
<Preparation of positive electrode>
First, LiNi _0.6 Co _0.2 Mn _0.2 O _{2 as} a positive electrode active material: 88 parts by mass, artificial graphite as a conductive auxiliary agent: 1 part by mass and Ketjen black: 1 part by mass, PVDF as a binder: 10 parts by mass Were mixed so as to be uniform using NMP as a solvent to prepare a positive electrode mixture-containing paste. Next, the positive electrode mixture-containing paste is applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm while adjusting the thickness, dried, and then subjected to a calendering process so that the total thickness of the positive electrode is The thickness of the positive electrode mixture layer was adjusted to 197 μm, and an aluminum lead body was welded to the exposed portion of the aluminum foil to produce a belt-like positive electrode having a length of 375 mm and a width of 43 mm.

<Production of negative electrode>
First, a mixed gas of 25 ° C. composed of methane and nitrogen gas is brought into contact with SiO particles heated to about 1000 ° C. in a boiling bed reactor, and a coating layer of a carbon material is formed on the surface of the SiO particles by vapor deposition. A formed composite of SiO and carbon material (D50 of SiO: 1 μm, ratio of SiO: 70 mass%, Si crystallite diameter in SiO: 40 nm) was obtained. A mixture of the composite of SiO and carbon material thus obtained and graphite having a D50 of 20 μm mixed at a mass ratio of 30:70: 98 parts by mass, and the viscosity is adjusted to the range of 1500 to 5000 mPa · s. CMC aqueous solution (concentration: 1% by mass): 1 part by mass and SBR: 1 part by mass were mixed to prepare an aqueous negative electrode mixture-containing paste.

  Next, the negative electrode mixture-containing paste is applied to both sides of a current collector made of a copper foil having a thickness of 8 μm while adjusting the thickness, dried, and then subjected to a calendering treatment to obtain a total thickness of the negative electrode. The thickness of the negative electrode mixture layer was adjusted so as to be 98 μm, and a copper lead body plated with nickel on one side was welded to the exposed portion of the copper foil to produce a strip-shaped negative electrode having a length of 380 mm and a width of 44 mm did.

<Preparation of the 1st electrolyte solution for primary charging / discharging processes>
In the same manner as in Example 1, a first electrolytic solution was prepared.

<Temporary assembly of non-aqueous electrolyte secondary battery: Primary injection>
The positive electrode and the negative electrode are wound through a separator made of a microporous polyethylene film having a thickness of 16 μm and a porosity of 50% to produce a wound electrode body, and this wound electrode body is housed in an exterior body did. Then, the said 1st electrolyte solution was first poured into the said exterior body, and it sealed, and produced the nonaqueous electrolyte secondary battery. A 463450 square battery can was used as the outer package.

<Primary charge / discharge process: Surface oxidation treatment>
The non-aqueous electrolyte secondary battery is charged at a constant current of 1 C until the battery voltage reaches 4.2 V, and then at the constant voltage of 4.2 V until the total charge time from the start of the first charge reaches 3 hours. After charging, constant current discharge (discharge end voltage: 2.7 V) was performed at 1C. This was regarded as one cycle, and charging / discharging was performed only for one cycle.

<Preparation of second electrolytic solution for secondary charge / discharge process>
In the same manner as in Example 1, a second electrolytic solution was prepared.

<Assembly of nonaqueous electrolyte secondary battery: Secondary injection>
The nonaqueous electrolyte secondary battery that has undergone the primary charge / discharge process is opened, and the second electrolytic solution is secondarily injected into the exterior body, and the nonaqueous electrolyte solution in the nonaqueous electrolyte secondary battery is A non-aqueous electrolyte secondary battery for testing was prepared by adjusting the volume ratio with VC to be non-aqueous electrolyte: VC = 9: 1.

(Comparative Example 1)
<Preparation of positive electrode and negative electrode>
In the same manner as in Example 1, a positive electrode and a negative electrode were produced.

<Preparation of non-aqueous electrolyte>
LiPF ₆ as a lithium salt was dissolved at a concentration of 1 mol / L in a mixture of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1 to prepare a mixed solution. Vinylene carbonate (VC) was further mixed with this mixed solution so that the mixed solution: VC = 9: 1 by volume ratio to prepare a nonaqueous electrolytic solution.

<Assembly of model cell>
The positive electrode and the negative electrode were laminated through a separator made of a microporous polyethylene film having a thickness of 16 μm and a porosity of 50% to produce a laminated electrode body, and this laminated electrode body was housed in an exterior body. Thereafter, the nonaqueous electrolyte solution was injected into the outer package to prepare a test model cell. “HS flat cell” manufactured by Hosen Co., Ltd. was used for the exterior body.

(Comparative Example 2)
<Preparation of positive electrode and negative electrode>
In the same manner as in Example 1, a positive electrode and a negative electrode were produced.

<Preparation of non-aqueous electrolyte>
LiPF ₆ as a lithium salt was dissolved at a concentration of 1 mol / L in a mixture of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1 to prepare a mixed solution. Further, vinylene carbonate (VC) and 4-fluoro-1,3-dioxolan-2-one (FEC) are mixed with this mixed solution so that the mixed solution: VC: FEC = 8: 1: 1. A non-aqueous electrolyte was prepared.

  A test model cell was produced in the same manner as in Comparative Example 1 except that the positive electrode, the negative electrode, and the non-aqueous electrolyte were used.

(Comparative Example 3)
A test model cell was produced in the same manner as in Example 1 except that the number of charge / discharge cycles in the primary charge / discharge process was set to 10 cycles.

(Comparative Example 4)
In the same manner as in Example 5, a positive electrode and a negative electrode were produced. Further, a nonaqueous electrolytic solution was prepared in the same manner as in Comparative Example 1.

<Assembly of non-aqueous electrolyte secondary battery>
The positive electrode and the negative electrode are wound through a separator made of a microporous polyethylene film having a thickness of 16 μm and a porosity of 50% to produce a wound electrode body, and this wound electrode body is housed in an exterior body did. Thereafter, the nonaqueous electrolyte solution was poured into the outer package and sealed to prepare a test nonaqueous electrolyte secondary battery. A 463450 square battery can was used as the outer package.

Next, the test model cells of Examples 1 to 4 and Comparative Examples 1 to 3 were charged with a constant current of 0.25 mA / cm ² until the battery voltage reached 4.2 V, and then the constant voltage of 4.2 V was set. after the current value was charged to a 0.025 mA / cm ² at a voltage, 0.25 mA / cm ² with a constant current discharge (discharge end voltage: 2.7V) was performed to measure the discharge capacity. With this as one cycle, 500 cycles of charge and discharge were performed, and the discharge capacity at the 500th cycle was measured. The charging / discharging of the said 1st cycle with respect to the model cell for a test of Examples 1-4 corresponds to the secondary charging / discharging process of this invention.

  In addition, the test non-aqueous electrolyte secondary batteries of Example 5 and Comparative Example 4 were charged at a constant current of 1 C until the battery voltage reached 4.2 V, and then the first charge was started at a constant voltage of 4.2 V. The battery was charged until the total charge time from 3 hours reached 3 hours, then a constant current discharge (discharge end voltage: 2.7 V) was performed at 1 C, and the discharge capacity was measured. With this as one cycle, 500 cycles of charge and discharge were performed, and the discharge capacity at the 500th cycle was measured. The first cycle charge / discharge of the test nonaqueous electrolyte secondary battery of Example 5 corresponds to the secondary charge / discharge step of the present invention.

  From the discharge capacity in the charge / discharge, the capacity retention rate was calculated by the following formula. The results are shown in Table 1.

  Capacity maintenance ratio (%) = (discharge capacity at 500th cycle / discharge capacity at the first cycle) × 100

  From Table 1, it can be seen that the batteries of Examples 1 to 5 of the present invention have a higher capacity retention rate than the batteries of Comparative Examples 1 to 4. In Comparative Examples 1, 2, and 4, since the primary charge / discharge process was not performed, an oxide film was not formed on the surface of the negative electrode active material, the reaction between the negative electrode active material and the nonaqueous electrolyte progressed, and the negative electrode active material and the nonaqueous solution It is considered that the high-resistance reaction product generated by the reaction with the electrolyte increased, and the charge / discharge cycle characteristics deteriorated. In Comparative Example 3, since the number of times of charge / discharge in the primary charge / discharge process exceeded 9, the oxide film once formed on the surface of the negative electrode active material was altered in the primary charge / discharge process to become a high-resistance film. It is considered that the discharge cycle characteristics have deteriorated.

<Confirmation of oxide film on the surface of the negative electrode active material>
In Example 1 and Comparative Example 3, each model cell subjected to the primary charge / discharge process was disassembled, and the negative electrode was taken out. Moreover, after charging / discharging the test model cell of the comparative example 1 and the comparative example 2 on the same charging / discharging conditions as the above-mentioned, each test model cell was decomposed | disassembled and the negative electrode was taken out.

  Next, after the taken-out negative electrode was washed with diethyl carbonate and vacuum-dried, the negative electrode mixture layer was subjected to XPS analysis. The entire process from taking out the negative electrode to XPS analysis was performed in an argon dry box.

From 2P spectrum of silicon (Si) by the XPS analysis, SiO ₂ spectral strength of the surface of the negative electrode mixture layer of Example 1, and SiO ₂ spectral strength of the surface of the negative electrode mixture layer of the Comparative Examples 1, 2 and 3 In comparison, it was found to be large. Therefore, the surface of the negative electrode mixture layer in Example 1, it was found that as compared with the surface of the negative electrode mixture layer of the Comparative Examples 1 to 3, the thick SiO ₂ layer (oxide film) is formed .

<Confirmation of organic coating on the surface of the negative electrode active material>
After charging and discharging the test model cell of Example 1 and Comparative Examples 1 to 3 under the above-described conditions, the test model cell was disassembled in the same manner as described above, the negative electrode was taken out, and XPS analysis was performed. It was.

  From the 1S spectrum of carbon (C) by the above XPS analysis, the various organic matter spectral intensities on the surface of the negative electrode mixture layer of Example 1 are the various organic matter spectral intensities on the surfaces of the negative electrode mixture layers of Comparative Examples 1, 2, and 3. In comparison, it was found to be large. From this, it turned out that the thick organic film is formed in the surface of the negative mix layer of Example 1 compared with the surface of the negative mix layer of Comparative Examples 1-3.

  Since the non-aqueous electrolyte secondary battery of the present invention has excellent charge / discharge cycle characteristics, it has been conventionally known to take advantage of this characteristic, including power supplies for small and multifunctional portable devices. It can be preferably used for various applications to which a nonaqueous electrolyte secondary battery is applied.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Exterior can 5 Insulator 6 Winding electrode body 7 Positive electrode lead body 8 Negative electrode lead body 9 Cover plate 10 Insulation packing 11 Terminal 12 Insulator 13 Lead plate 14 Nonaqueous electrolyte injection port 15 Cleavage vent 20 Nonaqueous electrolyte secondary battery 21 Exterior body 22 Positive electrode external terminal 23 Negative electrode external terminal

Claims (7)

A method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator,
A battery assembly process in which a positive electrode and a negative electrode in which a negative electrode mixture layer containing a material that can be alloyed with lithium is formed on the negative electrode current collector are opposed to each other with a separator interposed therebetween, and
A primary charging / discharging step of charging and discharging at a frequency of 1 to 9 times by injecting a first electrolytic solution containing a halogen-substituted cyclic carbonate into the exterior body;
A secondary charging / discharging step of charging and discharging by injecting a second electrolytic solution containing a cyclic carbonate having a carbon-carbon unsaturated bond into the outer package, and comprising a non-aqueous electrolyte secondary Battery manufacturing method.   The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the halogen-substituted cyclic carbonate contains fluorine as a halogen element.   The method for producing a nonaqueous electrolyte secondary battery according to claim 2, wherein the halogen-substituted cyclic carbonate is 4-fluoro-1,3-dioxolan-2-one.   The method for producing a nonaqueous electrolyte secondary battery according to claim 1, wherein the cyclic carbonate having a carbon-carbon unsaturated bond is vinylene carbonate.   The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the material that can be alloyed with lithium is a material containing silicon as a constituent element. The material containing silicon as a constituent element is a material represented by a general composition formula SiO _x ,
The method for producing a nonaqueous electrolyte secondary battery according to claim 5, wherein x in the general composition formula is 0.5 ≦ x ≦ 1.5.   The method for producing a nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode mixture layer further contains a carbon material.

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