JP2013191485A - Nonaqueous secondary battery - Google Patents

Abstract

In a non-aqueous secondary battery in which a power generation element is housed in a flexible exterior sheet, the possibility of thermal runaway during heating is reduced without increasing the battery thickness.
Power generation in which a sheet-like positive electrode 12p is inserted in a valley fold portion on one side of a strip-shaped separator 11 folded in a zigzag shape, and a sheet-like negative electrode 12n is inserted in a valley fold portion on the other side The element 5 is accommodated in the exterior sheet 2 having flexibility. The separator has a porous layer 11a made of a heat-meltable resin, and an insulating layer 11b containing insulating inorganic particles formed on one surface of the porous layer. At both ends 17 in the width direction of the separator, the porous layers facing each other are thermally welded.
[Selection] Figure 3

Description

  The present invention relates to a non-aqueous secondary battery. In particular, the present invention relates to a thin non-aqueous secondary battery that hardly causes thermal runaway during heating.

  In recent years, with the development of portable electronic devices such as mobile phones and notebook computers, and the practical application of electric vehicles, the demand for electrochemical elements such as high-energy density non-aqueous secondary batteries has increased rapidly. Currently, non-aqueous secondary batteries that can meet these requirements include, for example, a positive electrode using a lithium composite oxide that can be doped and dedoped with lithium ions, a material that can be doped and dedoped with lithium ions, and lithium metal. It is comprised using the used negative electrode and the nonaqueous electrolyte solution which melt | dissolved electrolyte salt in the organic solvent.

  In the non-aqueous secondary battery, with the recent thinning of portable electronic devices, there is an increasing demand for a laminated non-aqueous secondary battery having a thin plate shape in which a power generation element is packaged with a flexible laminate sheet. This is because there is an advantage that the battery can be made thinner and larger than a conventional battery packaged with a rectangular aluminum can.

  At present, a winding structure used for a cylindrical or prismatic battery is well known as the most commonly used power generation element structure. The power generation element of this winding structure is manufactured by superposing and winding a belt-like positive electrode and a belt-like negative electrode with a belt-like separator interposed therebetween. This winding structure has a problem that the mixture layer applied to the current collector is peeled off because the curvature of the positive electrode and the negative electrode is large at the center of the winding. This not only adversely affects the battery capacity, but also facilitates the deposition of lithium metal at the part where the electrode is peeled off, which is an important problem in terms of safety.

  In order to solve these problems, power generation elements having various structures have been proposed. As one of the effective elements, a plurality of sheet-like positive electrodes and a plurality of negative electrodes separated into a predetermined shape are laminated via separators. There is a laminated structure. In this laminated structure, a power generation element is proposed in which a strip-shaped separator is bent in a zigzag shape, a positive electrode is inserted into a valley fold portion on one side of the separator, and a negative electrode is inserted into a valley fold portion on the other side ( Patent Document 1). In addition to being excellent in manufacturing efficiency, this laminated structure has an advantage that it is easy to reduce the thickness because the electrode is not bent.

  However, in the non-aqueous secondary battery including the power generation element having the above laminated structure including the strip-shaped separator bent in a zigzag shape, the separator is thermally contracted when heated, and the positive electrode active material and the negative electrode active material are short-circuited. However, there is a problem of causing a thermal runaway.

  In order to solve this problem, a technique for suppressing thermal shrinkage of a separator by applying and forming a composition layer containing inorganic particles on one surface of a porous substrate is known. For example, Patent Document 2 describes a separator using boehmite as the inorganic particles. However, even when such a heat-resistant separator is used, depending on the heating temperature and the tension remaining in the separator, the separator may curl due to the difference in shrinkage between the front and back, leading to thermal runaway. .

  Patent Document 3 discloses that in a power generation element having a winding structure, a separator is fixed to a part of a positive electrode or a negative electrode with an adhesive tape based on a material having a melting point of 140 ° C. or higher. A technique for preventing a short circuit due to heat shrinkage is described. However, when this technology is applied to a laminate-type non-aqueous secondary battery, the thickness of the adhesive tape increases the battery thickness, and the problem of poor appearance tends to occur. This problem is particularly noticeable in a thin laminated non-aqueous secondary battery having a flat and wide plane.

JP 2002-157990 A JP 2011-228188 A JP 2003-168411 A

  The present invention solves the above-described conventional problems, and in a nonaqueous secondary battery in which a power generation element is housed in a flexible exterior sheet, thermal runaway occurs during heating without increasing the battery thickness. The aim is to reduce the possibility of happening.

  The non-aqueous secondary battery of the present invention includes a strip-shaped separator folded in a zigzag shape, a sheet-like positive electrode inserted into a valley fold portion on one side of the separator, and a valley fold on the other side of the separator. A power generation element having a sheet-like negative electrode inserted into the portion, and a flexible exterior sheet for housing the power generation element. The separator has a porous layer made of a heat-meltable resin, and an insulating layer formed on one side of the porous layer and containing insulating inorganic particles. The porous layers facing each other are thermally welded at both ends in the width direction of the strip-shaped separator.

  According to the present invention, in a non-aqueous secondary battery covered with a flexible outer sheet, the possibility of thermal runaway during heating can be reduced without increasing the battery thickness.

FIG. 1A is a plan view of a nonaqueous secondary battery according to an embodiment of the present invention, and FIG. 1B is a side view thereof. FIG. 2 is an exploded view conceptually showing the laminated structure of the power generation elements constituting the nonaqueous secondary battery of the present invention. FIG. 3A is a plan view showing the external appearance of the power generating element constituting the nonaqueous secondary battery of the present invention, and FIG. 3B is a perspective plan view showing the internal structure thereof. FIG. 4 is a plan view showing an external appearance of a power generation element constituting the nonaqueous secondary battery according to Comparative Example 3. FIG. 5 is a plan view showing the thickness measurement position of the nonaqueous secondary battery in the example.

  In the non-aqueous secondary battery of the present invention, the inorganic particles are preferably boehmite. Thereby, the thermal contraction at the time of the heating of a separator can be made small.

  The negative electrode is made of a carbon material capable of inserting and extracting lithium ions and a material containing Si and O (provided that the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5). It is preferable to include as a substance. Thereby, a high capacity | capacitance non-aqueous secondary battery is realizable.

  It is preferable that the positive electrode is disposed on the side of the separator where the insulating layer is formed. Thereby, a safer battery for the heating test can be obtained.

  Below, this invention is demonstrated in detail, showing suitable embodiment. However, it goes without saying that the present invention is not limited to the following embodiments. For convenience of explanation, the drawings referred to in the following description show only the main members necessary for explaining the present invention in a simplified manner among the constituent members of the embodiment of the present invention. Therefore, the present invention can include arbitrary components not shown in the following drawings. In addition, the dimensions of the members in the following drawings do not faithfully represent the actual dimensions of the constituent members and the dimensional ratios of the members.

(Schematic configuration of non-aqueous secondary battery)
FIG. 1A is a plan view of a non-aqueous secondary battery (hereinafter simply referred to as “battery”) 1 according to an embodiment of the present invention, and FIG. 1B is a side view thereof. A power generation element 5 is enclosed in an exterior sheet 2 having a substantially rectangular plan view. The exterior sheet 2 is a flexible multilayer sheet in which a heat-fusible resin layer (for example, a modified polyolefin layer) is laminated on the surface of the base layer made of aluminum or the like on the side facing the power generation element 5. The exterior sheet 2 is folded in half at one side (one short side in this example) 2r so as to sandwich the power generation element 5, and a seal region (region with dots in FIG. 1A) 3 along the three sides excluding the side 2r. It is sealed by a heat sealing method or the like.

  The power generation element 5 has a thin plate shape, and preferably has a substantially rectangular shape in plan view. The power generation element 5 includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte. The positive electrode is a sheet-like material in which a positive electrode mixture layer is formed in a predetermined region on at least one side of a positive electrode current collector (for example, an aluminum foil). The positive electrode mixture layer can be formed by mixing a positive electrode active material, a conductive additive and a binder in an organic solvent, and coating, drying and rolling the composition on a positive electrode current collector. The negative electrode is a sheet-like material in which a negative electrode mixture layer is formed in a predetermined region of at least one surface of a negative electrode current collector (for example, copper foil). The negative electrode mixture layer can be formed by applying, drying and rolling a negative electrode current collector on a negative electrode current collector, a composition in which a negative electrode active material mainly containing a carbon material, a binder, and optionally a conductive additive are mixed. A sheet-like separator is disposed between the positive electrode and the negative electrode.

  In FIG. 1A, a positive electrode lead 5p and a negative electrode lead that are electrically connected from one side (in this example, the other short side) 2f of the exterior sheet 2 to the positive electrode current collector and the negative electrode current collector that constitute the power generation element 5, respectively. 5n is derived.

  As shown in FIG. 2, the power generation element 5 folds the strip-shaped separator 11 in a zigzag manner by alternately repeating a mountain fold and a valley fold at regular intervals. The positive electrode 12p is inserted into the folded portion, and the negative electrode 12n is inserted into each valley folded portion from the other surface side. 11a is a porous layer made of a heat-meltable resin as a base material layer of the separator 11, and 11b is an insulating layer containing insulating inorganic particles formed on one surface of the porous layer 11a. 13p is a positive electrode current collector, and 14p is a positive electrode mixture layer formed on both surfaces of the positive electrode current collector 13p. Further, 13n is a negative electrode current collector, and 14n is a negative electrode mixture layer formed on both surfaces of the negative electrode current collector 13n. In this example, the positive electrode 12p is disposed on the side of the separator 11 where the insulating layer 11b is formed, and the negative electrode 12n is disposed on the side where the insulating layer 11b is not formed (on the porous layer 11a side).

  FIG. 3A is a plan view showing the appearance of the power generation element 5. Reference numeral 15 denotes an adhesive tape including a resin base material layer such as polypropylene, and fixes one end (termination) in the longitudinal direction of the strip-shaped separator 11. A positive electrode current collector 13p and a negative electrode current collector 13n constituting the positive electrode 12p and the negative electrode 12n respectively protrude from one side of the power generation element 5. A plurality of positive electrode current collectors 13p are bundled and electrically connected to the positive electrode lead 5p, and a plurality of negative electrode current collectors 13n are bundled and electrically connected to the negative electrode lead 5n. A film 16 made of a heat-fusible resin (for example, modified polyolefin (polypropylene, etc.)) is attached to the positive electrode lead 5p and the negative electrode lead 5n. The attachment position of the film 16 corresponds to the seal region 3 in FIG. 1A. Since the film 16 improves the adhesion between the leads 5p and 5n and the exterior sheet 2, it is advantageous for improving the sealing performance of the seal region 3.

  FIG. 3B is a perspective plan view showing the internal structure of the power generation element 5. Of the positive electrode 12p and the negative electrode 12n, a portion (generally referred to as an “ear portion”) excluding a portion of the positive electrode current collector 13p and the negative electrode current collector 13n protruding to connect the positive electrode lead 5p and the negative electrode lead 5n (generally, All of the planar view shapes (called “electrode portions”) are substantially rectangular. In the width direction of the strip-shaped separator 11 (left-right direction in FIG. 3B), the size of the electrode portion of the negative electrode 12n is slightly larger than the size of the electrode portion of the positive electrode 12p, and the width of the separator 11 is further larger than the size of the electrode portion of the negative electrode 12n. large. Reference numeral 17 denotes a heat welding portion formed on the separator 11 by a heat seal method or the like. The heat welding part 17 is formed slightly outside the negative electrode 12n (excluding the ear part) in the width direction of the separator 11 so as not to overlap the electrode part of the negative electrode 12n.

  The heat welding part 17 sandwiches the positive electrode 12p and the negative electrode 12n from both sides of the separator 11 bent in a zigzag shape as described in FIG. 2, and then the width direction of the separator 11 (direction perpendicular to the paper surface of FIG. 2). It is formed by locally heating the both end portions in the thickness direction (vertical direction in FIG. 2). As described above, in the separator 11, the insulating layer 11 b including insulating inorganic particles is formed on one surface of the porous layer 11 a made of a heat-meltable resin. Accordingly, the porous layers 11a facing each other (that is, the surface on which the insulating layer 11b is not formed) of the separator 11 bent in a zigzag shape are joined to each other by thermal welding at the thermal welding portion 17. 11, the insulating layers 11b facing each other are not thermally welded. Moreover, the part which opposes across the ear | edge part (negative electrode collector 13n) of the negative electrode 12n among the porous layers 11a is not heat-welded.

  Although there is no restriction | limiting in particular in the manufacturing method of the battery 1 (refer FIG. 1A and FIG. 1B) using the electric power generation element 5 comprised as mentioned above, For example, it can manufacture with the following method.

  First, the power generating element 5 is led out of the positive electrode lead 5p and the negative electrode lead 5n, wrapped with a flexible outer sheet 2, and the outer sheet 2 is sealed in a bag shape except for an opening for liquid injection. Create a pre-injection battery.

  Next, a non-aqueous electrolyte solution is injected from the injection opening of the bag-shaped exterior sheet 2, and the opening is thermally welded by a heat seal method or the like.

  Next, the power generation element 5 is initially charged to a predetermined voltage. Gas (initial gas) is generated in the exterior sheet 2 by the first charge.

  Next, the power generating element 5 housed in the exterior sheet 2 is stored (aged) in an atmosphere of 20 ° C. or higher and 80 ° C. or lower for several hours.

  Next, a hole is formed in the exterior sheet 2 to remove the gas in the exterior sheet 2 and the power generation element 5 is sealed in the exterior sheet 2 (degas sealing). In order to form a hole for degassing, the bag-shaped exterior sheet 2 may be formed larger in advance than the power generation element 5 and a portion including the hole of the exterior sheet 2 may be cut off and sealed.

  Then, the secondary chemical conversion process which fully charges to the planned battery voltage is implemented, and the battery 1 of the present invention can be obtained.

  In the separator 11 of the power generating element 5 constituting the battery 1 of the present invention, an insulating layer 11b containing insulating inorganic particles is formed on one surface of a porous layer 11a made of a heat-meltable resin. Therefore, thermal contraction of the separator 11 during heating is suppressed. Furthermore, the strip-shaped separator 11 is bent in a zigzag shape, and the porous layers facing each other are heat-welded at both end portions in the width direction. Accordingly, curling due to the difference in thermal shrinkage between the porous layer 11a and the insulating layer 11b is unlikely to occur during heating. As a result, the occurrence of the problem that the positive electrode active material and the negative electrode active material are short-circuited during heating to cause thermal runaway is suppressed. Further, unlike the above-described Patent Document 3, it is not necessary to use an adhesive tape to prevent the thermal contraction of the separator 11, so that the problem of poor thickness and poor appearance does not occur. Therefore, the battery 1 of the present invention can be suitably used as a laminated non-aqueous secondary battery having a flat plate and a wide flat surface.

  In the battery 1 described above, one exterior sheet 2 is folded in two at the side 2r and sealed by the sealing region 3 along the remaining three sides, but the present invention is not limited to this. The side where the exterior sheet 2 is folded in half may be a side other than the side 2r. Alternatively, two rectangular exterior sheets 2 having substantially the same size may be overlapped with the power generation element 5 interposed therebetween, and the two exterior sheets 2 may be sealed with seal regions along the four sides.

(Detailed configuration of non-aqueous secondary battery)
The non-aqueous secondary battery to which the present invention is applied is not particularly limited. For example, the present invention can be applied to non-aqueous secondary batteries having various configurations and structures that have been conventionally known.

  The detailed configuration of a typical nonaqueous secondary battery to which the present invention can be applied will be described below. However, it goes without saying that the present invention is applicable to non-aqueous secondary batteries other than the following non-aqueous secondary batteries.

<Positive electrode>
For the positive electrode of the power generation element 5, for example, a positive electrode mixture layer made of a positive electrode active material, a binder, and a positive electrode mixture containing a conductive auxiliary agent as necessary is provided on one or both sides of the positive electrode current collector. The thing of the structure which has can be used.

Examples of the positive electrode active material include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , Li _x Co _y M _1-y O ₂ , Li _x Ni _{1- y} M _y O _2, in _{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 ( structural formulas of the, M is, Mg, Mn , Fe, Co, Ni, Cu, Zn, Al, Ti, Ge and Cr, at least one metal element selected from the group consisting of 0 ≦ x ≦ 1.1, 0 <y <1.0, 2 And lithium-containing composite oxides such as 0.0 <z <1.0. These positive electrode active materials may use only 1 type and may use 2 or more types together.

  As the binder contained in the positive electrode mixture, any thermoplastic resin or thermosetting resin can be used as long as it is chemically stable in the non-aqueous secondary battery. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), PVDF, polyhexafluoropropylene (PHFP), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer ( FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer ( ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene -Chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, or ethylene-acrylic acid Copolymers, ethylene-methacrylic acid copolymers, ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, and Na ion cross-linked products of these copolymers, and the like are used alone. You may use, and may use 2 or more types together. Among these, in consideration of the stability in the non-aqueous secondary battery and the characteristics of the non-aqueous secondary battery, fluorine resins such as PVDF, PTFE, and PHFP are preferable. A copolymer formed by may be used.

  The amount of the binder in the positive electrode mixture layer is preferably as small as possible so that the positive electrode active material and the conductive additive can be stably bound. For example, the amount is 0.03 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. It is preferable.

  The conductive auxiliary agent contained in the positive electrode mixture may be any one that is chemically stable in the non-aqueous secondary battery. For example, graphite such as natural graphite and artificial graphite, acetylene black, ketjen black (trade name), carbon black such as channel black, furnace black, lamp black and thermal black; conductive fiber such as carbon fiber and metal fiber; aluminum Metallic 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; One species may be used alone, or two or more species may be used in combination. 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.

  The amount of the conductive auxiliary in the positive electrode mixture layer is sufficient if the conductivity and liquid absorbency can be secured satisfactorily. For example, the amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  For the positive electrode, for example, a positive electrode active material, a binder, and a conductive additive are dispersed in a solvent to prepare a paste-like or slurry-like positive electrode mixture-containing composition (note that the binder is dissolved in the solvent). The positive electrode mixture-containing composition may be applied to one or both surfaces of the positive electrode current collector, dried, and further subjected to press treatment as necessary to adjust the thickness and density of the positive electrode mixture layer. It can be manufactured through a process. The positive electrode is not limited to the one obtained by the above production method, and may be produced by another method.

  The material of the positive electrode current collector is not particularly limited as long as it is an electron conductor that is chemically stable in the non-aqueous secondary battery. For example, in addition to aluminum or aluminum alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., aluminum, aluminum alloy, or a composite material in which a carbon layer or a titanium layer is formed on the surface of stainless steel is used. it can. Among these, aluminum or an aluminum alloy is particularly preferable because it is lightweight and has high electron conductivity. For the positive electrode current collector, for example, a foil, a film, a sheet, a net, a punching sheet, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above materials is used. Further, the surface of the positive electrode current collector can be roughened by surface treatment. Although the thickness of a positive electrode electrical power collector is not specifically limited, Usually, it is 1-500 micrometers.

  In order to apply the positive electrode mixture-containing composition to the surface of such a positive electrode current collector, for example, a substrate lifting method using a doctor blade; a coater method using a die coater, comma coater, knife coater, etc .; screen printing, letterpress Printing methods such as printing can be adopted.

The thickness of the positive electrode mixture layer formed as described above is preferably 15 to 200 μm per one surface of the positive electrode current collector. Further, the density of the positive electrode mixture layer is preferably 3.2 g / cm ³ or more, and more preferably 3.4 g / cm ³ or more. When the positive electrode has such a high-density positive electrode mixture layer, the power generation element can have a higher capacity. However, if the density of the positive electrode mixture layer is too large, the porosity is decreased and the permeability of the electrolytic solution may be lowered. Therefore, the density of the positive electrode mixture layer is 4.1 g / cm ³ or less. It is preferable that For example, after the positive electrode mixture layer is formed, the positive electrode mixture layer having the above density can be formed by, for example, a press treatment of roll pressing at a linear pressure of about 1 to 100 kN / cm.

  In addition, the density of the positive mix layer as used in this specification is a value measured by the following method. The positive electrode is cut into a predetermined area, its mass is measured using an electronic balance with a minimum scale of 0.1 mg, and the mass of the positive electrode current collector is subtracted to calculate the mass of the positive electrode mixture layer. On the other hand, the total thickness of the positive electrode was measured at 10 points with a micrometer having a minimum scale of 1 μm, and the volume of the positive electrode mixture layer was determined from the average value obtained by subtracting the thickness of the positive electrode current collector from these measured values and the area. calculate. Then, the density of the positive electrode mixture layer is calculated by dividing the mass of the positive electrode mixture layer by the volume.

<Negative electrode>
As the negative electrode of the power generation element 5, a structure having a negative electrode mixture layer containing a negative electrode active material, a binder and the like on one side or both sides of the negative electrode current collector can be used.

  Examples of the negative electrode active material include graphite (natural graphite; artificial graphite obtained by graphitizing easily graphitized carbon such as pyrolytic carbons, MCMB, and carbon fiber at 2800 ° C. or more), pyrolytic carbons, cokes, and glass. Carbon materials that can occlude and desorb lithium ions, such as carbon-like carbons, organic polymer compound fired bodies, mesocarbon microbeads, carbon fibers, and activated carbon; elements that can be alloyed with lithium (Si, Sn, Ge, Bi, Sb, In, etc.), materials containing these elements (alloys, oxides, etc.); lithium and lithium alloys (lithium / aluminum, etc.), etc. can be used.

  Among these, graphite, elements that can be alloyed with lithium, or materials containing these elements are preferable in that a battery having a higher capacity can be formed.

As a material containing an element that can be alloyed with lithium, a material containing Si and O as constituent elements (provided that the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5. The material is particularly preferably “SiO _x ”.

The SiO _x may contain Si microcrystal or amorphous phase. In this case, the atomic ratio of Si and O is a ratio including Si microcrystal or amorphous phase Si. That is, the SiO _x, Si (e.g., microcrystalline Si) in the SiO ₂ matrix of amorphous include the dispersed structure, the SiO ₂ of the amorphous, dispersed therein In combination with Si, the atomic ratio x may satisfy 0.5 ≦ x ≦ 1.5. For example, in a structure in which Si is dispersed in an amorphous SiO ₂ matrix and a material having a molar ratio of SiO ₂ to Si of 1: 1, x = 1, so the structural formula is represented by SiO. . 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.

In addition, since SiO _x has low conductivity, for example, the surface of SiO _x may be used by being coated with carbon, whereby a conductive network in the negative electrode can be formed better.

As the carbon for coating the surface of SiO _x , for example, low crystalline carbon, carbon nanotube, vapor grown carbon fiber, or the like can be used.

Incidentally, the hydrocarbon gas is heated in the gas phase, the carbon generated by thermal decomposition of hydrocarbon gas, a method of depositing on the surface of the SiO _x particulate [vapor deposition (CVD) method], SiO _x When the surface of carbon is coated with carbon, the hydrocarbon-based gas spreads to every corner of the SiO _x particle, and a thin and uniform film (carbon coating layer) containing conductive carbon is present in the particle surface and in the pores of the surface. ) Can be imparted with good uniformity to the SiO _x particles with a small amount of carbon.

  As the liquid source of the hydrocarbon gas used in the CVD method, toluene, benzene, xylene, mesitylene and the like can be used, but toluene that is easy to handle is particularly preferable. A hydrocarbon-based gas can be obtained by vaporizing them (for example, bubbling with nitrogen gas). Moreover, methane gas, ethylene gas, acetylene gas, etc. can also be used.

As processing temperature of CVD method, it is preferable that it is 600-1200 degreeC, for example. Further, SiO _x subjected to CVD method is preferably granulated material was granulated by a known method (composite particles).

When the surface of SiO _x is coated with carbon, the amount of carbon is preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to SiO _x : 100 parts by mass, and 95 The amount is preferably at most part by mass, more preferably at most 90 parts by mass.

Since SiO _x has a large volume change due to charge / discharge of the battery, in a battery using a negative electrode having a negative electrode mixture layer using only this as a negative electrode active material, deterioration due to expansion / contraction of the negative electrode accompanying charge / discharge occurs. Cheap. In order to avoid such problems, it is preferable to use SiO _x and graphite in combination with the negative electrode active material. This makes it possible to maintain high charge / discharge cycle characteristics by suppressing expansion and contraction of the negative electrode accompanying charge / discharge of the battery while increasing the capacity by using SiO _x .

When SiO _x and graphite are used in combination in the negative electrode active material, the proportion of SiO _{x in} the total amount of the negative electrode active material is 0.5 mass% or more from the viewpoint of ensuring a high capacity increase effect by using SiO _x. In view of suppressing expansion and contraction of the negative electrode due to SiO _x , the content is preferably 10% by mass or less.

  Examples of the binder contained in the negative electrode mixture layer include fluorine resins such as PVDF, PTFE, and PHFP; synthetic rubbers such as styrene butadiene rubber (SBR) and nitrile rubber (NBR) and natural rubbers; carboxymethyl cellulose (CMC) ), Celluloses such as methyl cellulose (MC), hydroxyethyl cellulose (HEC); ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer And acrylic resins such as cross-linked products of these copolymers; amides such as polyamide, polyamideimide, poly N vinylacetamide; polyimide; polyacrylic acid; polyacrylic acid sulfonic acid; polysaccharides such as chitansan gum and guar gum; It is done.

  In addition, the negative electrode mixture layer may contain the conductive aid exemplified above as usable in the positive electrode mixture layer, if necessary.

  The material of the negative electrode current collector is not particularly limited as long as it is an electron conductor that is chemically stable in the constructed battery. For example, in addition to copper or copper alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., a composite material in which a carbon layer or a titanium layer is formed on the surface of copper, copper alloy, or stainless steel can be used. . Among these, copper or a copper alloy is particularly preferable because it is not alloyed with lithium and has high electron conductivity. As the negative electrode current collector, for example, a foil, a film, a sheet, a net, a punching sheet, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above materials can be used. In addition, the surface of the negative electrode current collector can be roughened by surface treatment. Although the thickness of a negative electrode collector is not specifically limited, Usually, it is 1-500 micrometers.

The negative electrode is, for example, a paste-like or slurry-like negative electrode mixture-containing composition (binder) in which a negative electrode active material and a binder, and further, if necessary, a negative electrode mixture containing a conductive additive are dispersed in a solvent. May be dissolved in a solvent) on one or both sides of the negative electrode current collector and dried to form a negative electrode mixture layer, and if necessary, press treatment is performed to obtain the thickness of the negative electrode mixture layer. Or by adjusting the density. The negative electrode is not limited to the one obtained by the above production method, and may be one produced by another method. The thickness of the negative electrode mixture layer is preferably 10 to 300 μm per side of the negative electrode current collector. Moreover, it is preferable that the density of the negative mix layer measured by the same method as the density of a positive mix layer is 1.0-2.2 g / cm < ³ >, for example.

<Separator>
The separator preferably includes a porous film made of a polyolefin such as polyethylene, polypropylene, or ethylene-propylene copolymer; a polyester such as polyethylene terephthalate or copolymer polyester; The porous membrane preferably has a property (that is, a shutdown function) in which the pores are closed at 100 to 140 ° C. Therefore, the porous film has a melting point, that is, a thermoplastic resin having a melting temperature of 100 to 140 ° C. as a component measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121. More preferably, it is a single layer porous membrane mainly composed of polyethylene or a laminated porous membrane comprising a porous membrane such as a laminated porous membrane in which 2 to 5 layers of polyethylene and polypropylene are laminated. Preferably there is. When a resin having a melting point higher than that of polyethylene such as polyethylene and polypropylene is used by mixing or laminating, it is desirable that polyethylene is 30% by mass or more, and 50% by mass or more as a resin constituting the porous membrane. More desirable.

  As such a resin porous membrane, for example, a porous membrane composed of the above-mentioned exemplified thermoplastic resin used in a conventionally known non-aqueous electrolyte secondary battery or the like, that is, a solvent extraction method, An ion-permeable porous membrane produced by a dry or wet stretching method can be used.

  The average pore diameter of the porous membrane is preferably 0.01 μm or more, more preferably 0.05 μm or more, preferably 1 μm or less, more preferably 0.5 μm or less.

As a characteristic of the porous membrane, a Gurley value expressed by the number of seconds that 100 ml of air permeates through the membrane under a pressure of 0.879 g / mm ² is 10 to 500 sec. It is desirable. If the air permeability is too high, the ion permeability is reduced, whereas if it is too low, the strength of the porous membrane may be reduced. Further, the strength of the porous membrane is desirably 50 g or more in terms of piercing strength using a needle having a diameter of 1 mm.

  An insulating layer containing insulating inorganic particles is formed on one surface of the porous film.

  Insulating inorganic particles have an effect of suppressing the occurrence of a short circuit due to lithium dendrite by, for example, filling a void formed in the porous film in the separator. The inorganic particles have electrical insulating properties, are electrochemically stable, and are stable to an electrolyte solution described later and a solvent used in a liquid composition used in the production of a separator, and are electrolyzed at a high temperature. If it does not melt | dissolve in a liquid, there will be no restriction | limiting in particular. The “high temperature state” as used in the present specification is specifically a temperature of 150 ° C. or higher, and may be any stable particle that does not undergo deformation and chemical composition change in the electrolyte at such a temperature. In addition, the term “electrochemically stable” as used in the present specification means that no chemical change occurs during charging / discharging of the battery.

Specific examples of such inorganic particles include, for example, oxide fine particles such as iron oxide, SiO ₂ , Al ₂ O ₃ , TiO ₂ , BaTiO ₂ , and ZrO; nitride fine particles such as aluminum nitride and silicon nitride; Slightly soluble ionic crystal particles such as calcium, barium fluoride, and barium sulfate; Covalent crystal particles such as silicon and diamond; Clay particles such as talc and montmorillonite; Boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, Examples thereof include substances derived from mineral resources such as sericite and bentonite or artificial products thereof. Further, the surface of the conductive fine particles such as metal fine particles; oxide fine particles such as SnO ₂ and tin-indium oxide (ITO); carbonaceous fine particles such as carbon black and graphite; Fine particles imparted with electrical insulation properties by surface treatment with the above-described materials constituting the electrically insulating inorganic particles) may be used. These inorganic particles may be used alone or in combination of two or more.

The form of the inorganic particles may be any form such as a spherical shape, a substantially spherical shape, or a plate shape, but preferably includes a plate-like particle. Examples of the plate-like particles include various commercially available products, such as “Sun Lovely” (SiO ₂ ) manufactured by Asahi Glass S-Tech, pulverized product (TiO ₂ ) of “NST-B1” manufactured by Ishihara Sangyo Co., Ltd. Plate-like barium sulfate “H series”, “HL series”, Hayashi Kasei “micron white” (talc), Hayashi Kasei “bengel” (bentonite), Kawai lime “BMM” and “BMT” (Boehmite), “Cerasure BMT-B” [Alumina (Al ₂ O ₃ )] manufactured by Kawai Lime Co., Ltd., “Seraph” (alumina) manufactured by Kinsei Matec Co., Ltd. ) Etc. are available. In addition, SiO ₂ , Al ₂ O ₃ , ZrO, and CeO ₂ can be produced by the method disclosed in Japanese Patent Laid-Open No. 2003-206475.

  In the case where the inorganic particles are plate-like, the occurrence of short-circuiting can be suppressed more satisfactorily by orienting the inorganic particles in the separator so that the flat plate surface is substantially parallel to the surface of the separator. This is because the inorganic particles are oriented as described above so that the inorganic particles overlap with each other on a part of the flat plate surface. Therefore, the gap (through hole) from one surface of the separator to the other surface is a straight line. It is thought that it is formed in a bent shape, and this can prevent the lithium dendrite from penetrating the separator, so that the occurrence of a short circuit is presumed to be better suppressed.

  As a form when the inorganic particles are plate-like particles, for example, the aspect ratio (maximum length in the plate-like particles / thickness of the plate-like particles) is 5 or more, more preferably 10 or more, and 100 Below, it is desirable that it is 50 or less. Further, the average value of the ratio of the length in the major axis direction to the length in the minor axis direction (length in the major axis direction / length in the minor axis direction) of the flat plate surface of the grains is preferably 3 or less, more preferably 2 or less. . When the plate-like inorganic particles have the above-mentioned aspect ratio and the average value of the ratio of the long-axis direction length to the short-axis direction length of the flat plate surface, the above-described short-circuit prevention action is more effectively exhibited. .

  The average value of the ratio of the length in the long axis direction to the length in the short axis direction of the flat plate surface in the case where the inorganic particles are plate-like is obtained by, for example, performing image analysis on an image taken with a scanning electron microscope (SEM). Can be sought. Furthermore, the above aspect ratio in the case where the inorganic particles are plate-like can also be obtained by image analysis of an image taken by SEM.

  Moreover, the particle | grains containing 2 or more types of materials (inorganic material) which comprise the various inorganic particles of the said illustration may be sufficient as an inorganic particle.

  In the separator of the present invention, the hydrophobicity of the separator can be controlled by inorganic particles or a binder described later to obtain a specific water content. In order to control the hydrophobicity of the separator by the inorganic particles, it is preferable to use the surface of the inorganic particles exemplified above by applying a hydrophobic treatment. On the other hand, when the hydrophobicity of the separator is controlled by a binder, the inorganic particles illustrated above that have not been subjected to surface hydrophobization treatment may be used as the inorganic particles, but the surface of the inorganic particles illustrated above may be hydrophobized. It is more preferable to use a material that has been treated.

  The method for hydrophobizing the surface of the inorganic particles is, for example, at least one selected from the group consisting of silazane, silane coupling agent, silicone oil, titanate coupling agent, aluminate coupling agent, and zirconate coupling agent. A method of performing a surface treatment of inorganic particles using a seed surface modifier can be used. These surface modifiers are known as surface modifiers for the hydrophobic treatment of toner. For example, in the presence of water, the surface of inorganic particles may be hydrolyzed by hydrolysis of alkoxy groups of the surface modifier. By being covalently bonded to the hydroxyl group, it has an action of reducing the hydrophilicity of the surface of the inorganic particles, that is, an action of making it hydrophobic.

  The surface modifier should be selected appropriately for the functional group (side chain functional group) contained in the molecule according to the type of inorganic particles to be treated and the system (solvent used, etc.) to be hydrophobized. Is preferred. Specifically, a surface modifier having a functional group such as an amino group, an epoxy group, a vinyl group, a sulfide group, a chloro group, a fluoro group, a phenyl group, a phenoxy group, an alkyl group, or an alkoxy group can be used. In the case of an alkyl group, the number of carbon atoms is preferably selected between 1 (methyl group) and 10 (decyl group).

  Hydrophobic treatment with the above surface modifier is a dry method in which inorganic particles that are forcibly agitated are sprayed with dry air or nitrogen gas in a state where the surface modifier is directly or diluted with a solvent; It can be carried out by a wet method in which inorganic particles are dispersed in water, and when the slurry is in a slurry state, the surface modifier is added directly or in the form of a solution diluted in a solvent, followed by settling and separation followed by drying.

  In the case of a wet method, it is preferable to adjust the pH in the system to 3 to 4, for example. In the case of the wet method, the inorganic particles and the surface modifier may be added to the slurry to add a binder and other materials, and the separator may be made simultaneously with the hydrophobic treatment of the inorganic particles. . Furthermore, in order to increase the reactivity between the inorganic particles and the surface modifier, an activation treatment of the inorganic particles may be performed.

  The amount of the surface modifier used is preferably 0.2 to 2% by mass with respect to the total mass of the surface modifier and the inorganic particles, for example.

  Further, in either case of the dry method or the wet method, drying is preferably performed, and the drying is more preferably performed in an inert atmosphere or under reduced pressure. In addition, among the dry methods and wet methods described above, the drying temperature may be set to be equal to or lower than the heat resistant temperature of the inorganic particles after the treatment when only the surface of the inorganic particles is hydrophobized. When the hydrophobic treatment of the inorganic particles is performed simultaneously with the formation of the separator, it is preferable that the temperature is not higher than the heat resistance temperature of each constituent material of the separator.

  Moreover, when using specific inorganic particles, such as a silica, an alumina, and a boehmite, the surface can be hydrophobized by heat processing. In these inorganic particles, for example, the surface adsorbed water is removed by heat treatment (baking) at 300 to 1000 ° C., more preferably 500 to 1000 ° C., and the hydroxyl groups present on the surface are dehydrated and condensed to increase the hydrophobicity. be able to.

  Further, the inorganic particles whose surfaces have been hydrophobized by the above heat treatment may be further hydrophobized by the above method using a surface modifier. In this case, for example, it is also possible to employ a spray method in which the inorganic particles immediately after being taken out from the furnace for heat treatment are sprayed directly or in the state of a solution diluted with a solvent.

  As the size of the inorganic particles, the particle size at the time of drying may be smaller than the thickness of the porous membrane, but the average particle size is smaller than the thickness of the porous membrane and larger than 1/100 of the thickness of the porous membrane. Specifically, it is desirable that the average particle diameter is 0.01 μm or more, more preferably 0.1 μm or more. By setting the average particle diameter of the inorganic particles to the above specific value, the gap between the particles can be increased to some extent, the ion conduction path in the separator can be shortened, and the battery characteristics can be improved. In addition, if the inorganic particles are too large, the gap between the particles becomes too large, and the effect of preventing a short circuit due to the generation of lithium dendrite may be reduced, so the average particle size is 10 μm or less. Is preferably 5 μm or less.

  Here, the average particle diameter of the inorganic particles is a number average particle diameter measured by dispersing in a medium (for example, water) using a laser scattering particle size distribution meter (“LA-920” manufactured by HORIBA).

  The content of the inorganic particles in the separator of the present invention is 20% by volume or more, more preferably 40% by volume or more, and 70% by volume or less, more preferably 60% by volume or less, in the total volume of the constituent components of the separator. It is desirable to be.

  A binder is used to bind the porous membrane and the inorganic particles.

  Any binder may be used as long as it is electrochemically stable and stable with respect to the electrolytic solution, and can adhere well to the porous membrane and inorganic particles. For example, the structural unit derived from vinyl acetate is 20 to 35 mol. % Ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer such as ethylene-ethyl acrylate copolymer, cross-linked polyacrylate, fluorinated rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) ), Hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyurethane, epoxy resin and the like. These may be used alone or in combination of two or more. It doesn't matter. In addition, when using these binders, it can be used with the form of the emulsion dissolved or disperse | distributed to the solvent of the liquid composition for separator formation.

<Nonaqueous electrolyte>
As the non-aqueous electrolyte, a solution (non-aqueous electrolyte solution) in which an electrolyte salt is dissolved in an organic solvent can be used. Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, and 1,2-dimethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, 3 Non-prototypes such as methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propane sultone Sex organic solvents may be used alone or in combination. Also, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can be used. Among these, a mixed solvent of EC, MEC, and DEC is preferable, and in this case, it is more preferable that DEC is included in an amount of 15% by volume to 80% by volume with respect to the total volume of the mixed solvent. This is because such a mixed solvent can enhance the stability of the solvent during high-voltage charging while maintaining the low temperature characteristics and charge / discharge cycle characteristics of the battery high.

As the electrolyte salt related to the non-aqueous electrolyte, a salt of a fluorine-containing compound such as lithium perchlorate, lithium organic boron, trifluoromethanesulfonate, imide salt, or the like is preferably used. Specific examples of the electrolyte salt, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 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 (n ≧ 2), LiN (Rf ₃ OSO ₂ ) ₂ , Rf represents a fluoroalkyl group. These may be used alone or in combination of two or more thereof. Among these, LiPF ₆ and LiBF ₄ are more preferable because of good charge / discharge characteristics. This is because these fluorine-containing organic lithium salts have a large anionic property and are easily ion-separated, so that they are easily dissolved in the solvent. The concentration of the electrolyte salt in the solvent is not particularly limited, but is usually 0.5 to 1.7 mol / L.

  In addition, for the purpose of improving the safety, charge / discharge cycleability, and high-temperature storage properties of the nonaqueous electrolyte, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, Additives such as fluoroethylene carbonate, difluoroethylene carbonate, t-butylbenzene, triethyl phosphate, and triethylphosphonoacetate can be appropriately added.

  For example, when vinylene carbonate is contained in the nonaqueous electrolyte, the content of vinylene carbonate in the nonaqueous electrolyte used in the battery is preferably 0.01 to 5% by mass. When fluoroethylene carbonate is contained, the content of fluoroethylene carbonate in the non-aqueous electrolyte used in the battery is preferably 0.01 to 5% by mass.

<Exterior sheet>
As a flexible exterior sheet used for the exterior, a general aluminum laminate that is commonly used for non-aqueous secondary batteries, in which a polypropylene layer on the inside, a polyester layer, and a nylon layer on the outside are laminated and integrated with an aluminum foil at the center. A sheet can be used.

  The power generation element of the present invention including the positive electrode, the negative electrode, and the separator has a laminated structure in which the positive electrode and the negative electrode are stacked via a strip-shaped separator bent in a zigzag shape as described in FIG. have.

  The non-aqueous secondary battery of the present invention is used for power supplies of various electronic devices such as portable electronic devices such as mobile phones and notebook computers, and is used for power tools, automobiles, bicycles, power storage, etc. where safety is important. It can also be applied to other uses.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

Example 1
<Preparation of positive electrode>
94 parts by mass of a positive electrode active material represented by LiCoO ₂ , 4 parts by mass (as a solid content) of PVDF (10% NMP solution) as a binder, 1 part by mass of artificial graphite as a conductive additive, and Ketjen Black One part by mass was kneaded using a planetary mixer, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing composition.

  After applying the positive electrode mixture-containing composition to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, vacuum drying is performed at 120 ° C. for 12 hours to form a positive electrode mixture layer on both surfaces of the aluminum foil. Formed. Then, the press process was performed and the thickness and density of the positive mix layer were adjusted. The resulting positive electrode was cut out to a predetermined size using a Thomson blade to obtain a positive electrode.

<Production of negative electrode>
To 97.5 parts by mass of natural graphite having a number average particle size of 10 μm as a negative electrode active material, 1.5 parts by mass of styrene butadiene rubber as a binder, and 1 part by mass of carboxymethyl cellulose as a thickener, Were added and mixed to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste was applied to both sides of a copper foil having a thickness of 8 μm, and then vacuum-dried at 120 ° C. for 12 hours to form negative electrode mixture layers on both sides of the copper foil. Then, the press process was performed and the thickness and density of the negative mix layer were adjusted. The produced negative electrode was cut out to a predetermined size using a Thomson blade to obtain a negative electrode.

<Preparation of electrolyte>
LiPF ₆ was dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 2: 3: 1, and 2.5% by mass of vinylene carbonate was added. Prepared.

<Create separator>
The surface of plate boehmite (average particle diameter: 1 μm, aspect ratio: 10) was treated with methyltriethoxysilane [“SZ6072 (trade name)” manufactured by Toray Dow Corning Co., Ltd.], which is a surface treatment agent, in the following method. The fine particles hydrophobized with 1 were used as inorganic particles. 10 g of the surface treatment agent was added dropwise to 1000 g of pH 4 water, followed by stirring for 1 hour. To this surface treatment solution, a slurry of 1000 g of plate boehmite and 1000 g of water was added with stirring, then stirred for 60 minutes, and then allowed to stand to precipitate and separate the fine particles, and dried under reduced pressure at 120 ° C. for 15 hours. As a result, inorganic particles having a hydrophobic surface were obtained.

  Add 1000 g of water to 1000 g of the above inorganic particles to form a slurry, and add 600 g of SBR latex (solid content ratio: 3% by mass), which is a binder comprising an emulsion containing a surfactant, and stir with a three-one motor for 1 hour. Dispersed into a uniform slurry. This slurry was applied to one side of a strip-shaped porous film made of polyethylene having a thickness of 12 μm and dried under reduced pressure at 60 ° C. for 15 hours. The insulating layer containing inorganic particles had a thickness of 4 μm and a total thickness of 16 μm. A separator (porosity: 43%) was obtained.

<Battery assembly>
The belt-like separator was folded in a zigzag shape by repeatedly performing valley folding and mountain folding at a constant pitch. FIG. 2 has seven positive electrodes and eight negative electrodes, with the positive electrode inserted into each valley fold on the insulating layer side and the negative electrode inserted into each valley fold on the porous membrane side. A laminated electrode body having the laminated structure shown was obtained. In the width direction of the separator, the protruding length L (see FIG. 3B) of the separator from the edge of the electrode portion of the negative electrode was 1.5 mm. As shown in FIG. 3A, the end of the separator 11 in the longitudinal direction was fixed with an insulating tape 15 made of polypropylene. An aluminum positive electrode lead 5 p was welded to the positive electrode current collector 13 p protruding from the separator 11. A negative electrode lead 5n made of nickel was welded to the negative electrode current collector 13n protruding from the separator 11. The positive electrode lead 5p and the negative electrode lead 5n were provided with a propylene resin film 16 for improving the heat-weldability.

  Next, both end portions in the width direction of the separator 11 were heated using a heat sealer to form a heat welded portion 17. The width (refer to FIG. 3B) W (refer to FIG. 3B) of the heat welded portion 17 (the dimension of the heat welded portion 17 along the width direction of the separator 11) was 0.75 mm. Thereby, in the heat welding part 17, the mutually opposite porous layers of the separator 11 were heat welded. The mutually opposing insulating layers of the separator 11 were not thermally welded. Thus, the power generation element 5 of Example 1 was obtained.

  A recess having a size that can accommodate the power generating element 5 was formed on a flexible exterior sheet (aluminum laminate sheet) having a thickness of 114 μm and using an aluminum foil as a base layer. The power generation element 5 was stored in the hollow of the exterior sheet. The exterior sheet was folded in two along the side of the power generation element 5 opposite to the side where the positive electrode lead 5p and the negative electrode lead 5n were provided. Two sides of the rectangular exterior sheet that were overlapped with the power generation element 5 sandwiched by folding were heat-sealed with a heat sealer to form a bag, and a pre-injection battery was obtained. The battery before injection was vacuum dried at 60 ° C. for 12 hours. Thereafter, a nonaqueous electrolytic solution was poured into the exterior sheet from the opening of the bag-shaped exterior sheet, and the opening was immediately heat-sealed with a heat sealer. Thus, a battery in which the power generation element 5 was sealed with the exterior sheet was obtained.

(Example 2)
<Preparation of positive electrode>
A positive electrode was produced in the same manner as in Example 1.

<Production of negative electrode>
The composite particles of SiO (average particle size 5.0 μm) were heated to about 1000 ° C. in a boiling bed reactor, and the heated particles were contacted with a mixed gas of 25 ° C. composed of ethylene and nitrogen gas, and 60 ° C. at 60 ° C. CVD treatment was performed for a minute. In this way, carbon (hereinafter referred to as “CVD carbon”) generated by thermal decomposition of the mixed gas was deposited on the composite particles to form a coating layer, thereby obtaining a negative electrode material (carbon-coated SiO).

  When the composition of the negative electrode material was calculated from the mass change before and after the formation of the coating layer, it was SiO: CVD carbon = 80: 20 (mass ratio).

  The negative electrode active material was changed to a mixture of 48.0 parts by mass of natural graphite having a number average particle diameter of 10 μm, 49.0 parts by mass of artificial graphite having a number average particle diameter of 15 μm, and 3 parts by mass of the carbon-coated SiO 2. Produced a negative electrode in the same manner as in Example 1.

<Preparation of electrolyte>
LiPF ₆ is dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 2: 3: 1, and 2.5% by mass of vinylene carbonate and 1.0% by mass of fluoroethylene carbonate. % Was added to prepare an electrolytic solution.

<Create separator>
A separator was produced in the same manner as in Example 1.

<Battery assembly>
A battery was produced in the same manner as in Example 1.

(Comparative Example 1)
A battery was produced in the same manner as in Example 1 except that the heat welding treatment for forming the heat welding portion 17 was not performed in the production process of the power generation element 5.

(Comparative Example 2)
A battery was produced in the same manner as in Example 2 except that the heat welding treatment for forming the heat welding part 17 was not performed in the production process of the power generation element 5.

(Comparative Example 3)
In the manufacturing process of the power generation element 5, the heat welding process for forming the heat welding portion 17 is not performed, and as shown in FIG. 4, along the side opposite to the positive electrode lead 5p and the negative electrode lead 5n of the power generation element 5. The heat-resistant adhesive tape 18 was attached so as to span between the front and back surfaces of the power generation element 5. A battery was fabricated in the same manner as in Example 1 except for the above.

(Evaluation)
The following evaluation was performed on the non-aqueous secondary batteries of Examples 1 and 2 and Comparative Examples 1, 2 and 3 described above.

<Heating test>
The battery was first charged with a constant current at a maximum current of 2200 mA and an upper limit voltage of 4.2 V, and then charged at a constant voltage of 4.2 V until the charging current reached 110 mA. Thereafter, a thermocouple is attached to the surface of the battery, suspended in a thermostat, the ambient temperature is raised from 23 ° C. to 130 ° C. at a rate of temperature increase of 5 ° C. ± 2 ° C./min, and maintained at 130 ° C. for 1 hour. The maximum temperature reached was measured. For each of Examples 1 and 2 and Comparative Examples 1, 2, and 3, measurements were made on 10 batteries.

<Battery thickness measurement>
The battery thickness was measured with a micrometer at six points P1 to P6 shown in FIG. The points P1 to P6 are all located in a region where the positive electrode 12p and the negative electrode 12n are stacked. The point P2 is located on the adhesive tape 15 (see FIG. 3A) that fixes the end of the separator 11, and the point P6 is located on the heat-resistant adhesive tape 18 (see FIG. 4) in Comparative Example 3.

<Result>
Table 1 shows the measurement results of the maximum temperature achieved in the heating test for Examples 1 and 2 and Comparative Examples 1, 2 and 3.

  As shown in Table 1, in Examples 1 and 2, the maximum reached temperature of 10 batteries was 130 ° C., which is the same as the ambient temperature, and the batteries did not generate heat. In contrast, in Comparative Example 1, one out of ten batteries, in Comparative Example 2, two out of ten batteries, and in Comparative Example 3, one out of ten batteries had a maximum temperature of 200 ° C. It generated more heat. This is because, in Examples 1 and 2, both ends in the width direction of the separator were thermally welded, so that the thermal contraction and curling of the separator were suppressed when heated to 130 ° C., and thermal runaway due to internal short circuit did not occur. it is conceivable that.

  As for the battery thickness, Comparative Example 3 showed a significantly larger value than that of Examples 1 and 2 at measurement point P6. In Comparative Example 3, since the heat-resistant adhesive tape 18 was attached to the bottom of the power generation element, the battery was thickened by an amount substantially corresponding to the thickness of the heat-resistant adhesive tape 18.

  From these facts, it was confirmed that according to the present invention, it is possible to produce a thin battery while maintaining safety.

  The application field of the present invention is not particularly limited, and can be widely used for laminated non-aqueous secondary batteries. In particular, it can be preferably used for a secondary battery having a large area when viewed in plan and thin.

DESCRIPTION OF SYMBOLS 1 Nonaqueous secondary battery 2 Exterior sheet 3 Sealing area 5 Power generation element 5p Positive electrode lead 5n Negative electrode lead 11 Separator 11a Porous layer 11b Insulating layer 12p Positive electrode 12n Negative electrode 17

Claims (4)

A strip-like separator folded in a zigzag shape, a sheet-like positive electrode inserted into a valley fold portion on one side of the separator, and a sheet-like negative electrode inserted into a valley fold portion on the other side of the separator A power generation element having
A non-aqueous secondary battery comprising a flexible exterior sheet that houses the power generation element,
The separator has a porous layer made of a heat-meltable resin, and an insulating layer formed on one side of the porous layer and containing insulating inorganic particles.
The nonaqueous secondary battery, wherein the porous layers facing each other are heat-welded at both ends in the width direction of the strip-shaped separator.   The non-aqueous secondary battery according to claim 1, wherein the inorganic particles are boehmite.   The negative electrode is made of a carbon material capable of inserting and extracting lithium ions and a material containing Si and O (provided that the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5). The nonaqueous secondary battery according to claim 1, which is contained as a substance.   The nonaqueous secondary battery according to claim 1, wherein the positive electrode is disposed on a side of the separator on which the insulating layer is formed.

Images