JP2015069957A - Separator for lithium ion secondary battery and method for manufacturing the same, and lithium ion secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a lithium ion secondary battery including an electrode and a separator integrated therein and having favorable load characteristics; a method for manufacturing the lithium ion secondary battery; a separator capable of constituting the lithium ion secondary battery; and a method for manufacturing the separator.SOLUTION: In a separator of the present invention, an adhesive including a fibrous portion attaches on one side or both sides of a porous base material, the basis weight of the adhesive per one side of the porous base material is 44-2,700 mg/m, and the difference between the air permeability of the porous base material and the air permeability of the separator is 50 sec/100 mL or less. In a lithium ion secondary battery of the present invention, a separator and at least one of a positive electrode and a negative electrode are integrated by an adhesive including a fibrous portion, and the basis weight of the adhesive is 44-2,700 mg/m. The separator of the present invention can be manufactured by a method including a step in which an adhesive is attached on one side or both sides of a porous base material by an electrospinning method or a melt blow method.

Description

  The present invention relates to a lithium ion secondary battery having a good load characteristic in which an electrode and a separator are integrated, a manufacturing method thereof, a separator capable of constituting the lithium ion secondary battery, and a manufacturing method thereof. is there.

  Lithium ion secondary batteries are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density.

  By the way, there are lithium ion secondary batteries in which an electrode and a separator are integrated for various reasons (for example, Patent Documents 1 to 5).

Japanese Patent Laid-Open No. 10-189054 JP 2002-15773 A JP 2006-289985 A JP 2011-23186 A JP 2011-54502 A

  In recent years, an attempt has been made to use a lithium ion secondary battery as a power source other than the power source of a portable device. Specifically, lithium-ion secondary batteries have come to be used for power supplies for automobiles and motorcycles, and for mobile objects such as robots, etc., but with a large current value required for such applications. It is required to have an excellent load characteristic so that a sufficient capacity can be drawn even after charging and discharging.

  However, in a lithium ion secondary battery in which an electrode and a separator are integrated, load characteristics are likely to be lower than in a battery in which these are not integrated, and there is room for improvement in this respect.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lithium ion secondary battery having a good load characteristic, in which an electrode and a separator are integrated, a manufacturing method thereof, and the lithium ion It is providing the separator which can comprise a secondary battery, and its manufacturing method.

The lithium ion secondary battery separator of the present invention that has achieved the above object is a separator used for a lithium ion secondary battery in which an electrode and a separator are integrated, and is one or both sides of a porous substrate. An adhesive containing a fibrous portion is attached to the adhesive, and the basis weight of the adhesive per one side of the porous substrate is 44 to 2700 mg / m ^2, which is expressed by the Gurley value of the porous substrate. The difference between the air permeability and the air permeability represented by the Gurley value of the separator is 50 sec / 100 ml or less.

  The separator for a lithium ion secondary battery of the present invention has a step of attaching an adhesive containing a fibrous portion to one side or both sides of a porous substrate by an electrospinning method or a melt blow method. It can manufacture with the manufacturing method of the separator for batteries.

The lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, and at least one of the positive electrode and the negative electrode and the separator include a fibrous portion. It is integrated with an agent, and the basis weight of the adhesive present on the adhesive surface between at least one of the positive electrode and the negative electrode and the separator is 44 to 2700 mg / m ^2. .

  The lithium ion secondary battery of the present invention can be manufactured by the following manufacturing method (1) or (2).

(1) Adhesive which uses the separator for lithium ion secondary batteries of the present invention and has the separator for lithium ion secondary batteries and at least one of the positive electrode and the negative electrode in the separator for lithium ion secondary batteries The manufacturing method of the lithium ion secondary battery which has the process of adhere | attaching and integrating by.

(2) A step of attaching an adhesive containing a fibrous portion to the surface of at least one of the positive electrode and the negative electrode by an electrospinning method or a melt blow method, and the electrode and the separator having the adhesive, A method of manufacturing a lithium ion secondary battery, comprising the steps of bonding and integrating with the adhesive.

  According to the present invention, a lithium ion secondary battery in which an electrode and a separator are integrated and load characteristics are good, and a manufacturing method thereof, and a separator that can constitute the lithium ion secondary battery and a manufacturing method thereof are provided. Can be provided.

It is a scanning electron micrograph showing an example of the separator for lithium ion secondary batteries of this invention. It is a schematic diagram for demonstrating the structure of the laminated electrode body of the form folded in spelling. It is a top view which represents typically an example of the lithium ion secondary battery of this invention. FIG. 4 is a sectional view taken along line AA in FIG. 3.

  The separator for a lithium ion secondary battery of the present invention (hereinafter sometimes simply referred to as “separator”) is one in which an adhesive containing a fibrous portion is attached to one side or both sides of a porous substrate. .

  In the technology of integrating the electrode and separator with an adhesive or the like, an adhesive layer is formed on the surface of the electrode or separator, and the electrode and separator are overlapped via this adhesive layer, and heated or pressed as necessary. In general, the two are integrated.

  In many cases, the adhesive layer formed on the surface of the electrode or the separator is, for example, a relatively thick and highly uniform film-like layer in order to improve the adhesion between them. However, since the adhesive layer itself has no ion permeability or extremely low ion permeability, it is interposed between the electrode and the separator, so that the lithium ion between the electrodes during the charge / discharge reaction of the battery can be prevented. Movement is hindered.

  Therefore, conventionally, pores are usually formed by including an inorganic filler or the like in the adhesive layer so that lithium ions can move within the adhesive layer. However, in such a method, since a part of the adhesive fills the hole of the separator, there is not much problem when charging / discharging at a light load with a relatively small current value, but the current value is large. When charging / discharging with a heavy load, the capacity inherent in the battery cannot be sufficiently extracted.

  Therefore, in the present invention, by adopting a specific method, it is difficult to inhibit the movement of lithium ions, and the electrode and the separator can be satisfactorily bonded, so that the separator can have an adhesive, A separator capable of forming a lithium ion secondary battery with good load characteristics can be provided.

  FIG. 1 shows a scanning electron microscope (SEM) photograph of an example of a separator for a lithium ion secondary battery of the present invention (a separator used in the lithium ion secondary battery of Example 4 described later). In the figure, the adhesive including the fibrous portion on the near side is an adhesive, and the back side is a porous substrate.

In the separator of the present invention, the basis weight of the adhesive per one side of the porous substrate is 44 mg / m ² or more, and preferably 50 mg / m ² or more. In the separator of the present invention, even if the amount of the adhesive to be integrated with the electrode is reduced in this way, the adhesive strength sufficient to bond with the electrode is ensured by adopting a form including a fibrous portion. can do. Therefore, according to the separator of the present invention, when a lithium ion secondary battery is manufactured using the separator, the electrode body including the electrode and the separator is formed, or the electrode body is inserted into the exterior body. In addition, since the positional deviation between the electrode and the separator in the electrode body can be satisfactorily prevented, the productivity of the lithium ion secondary battery can be increased, and further, the positional deviation between the electrode and the separator can be prevented in the battery, Battery reliability can also be increased.

Further, in the separator of the present invention, the basis weight of the adhesive per side of the porous substrate is more preferably 230 mg / ^{m 2} or more, more preferably 250 mg / ^{m 2} or more. In the lithium ion secondary battery, when the internal temperature rises due to some trouble, there is a possibility that the separator contracts and a short circuit occurs in which the positive electrode and the negative electrode are in direct contact. However, if the basis weight of the adhesive is a separator having the above value, the adhesive force between the electrode and the separator increases, so even if the temperature of the separator (its porous substrate) shrinks, it is integrated with the electrode. Therefore, the shrinkage can be satisfactorily suppressed. Therefore, if the basis weight of the adhesive is the separator having the above value, a lithium ion secondary battery with higher safety can be configured.

On the other hand, in the separator of the present invention, the basis weight of the adhesive per side of the porous substrate is preferably at 2700 mg / ^{m 2} or less, more preferably 2500 mg / ^{m 2} or less, 2000 mg / ^{m 2} or less More preferably. By restricting the basis weight of the adhesive as described above, the number of pores of the separator filled with the adhesive can be reduced, and the ion permeability of the separator can be ensured well. It can be set as the separator which can comprise a battery.

  That is, in the separator of the present invention, the air permeability represented by the Gurley value of the porous base material is the separator having the above-described structure with respect to the adhesive and the basis weight of the adhesive satisfying the above value. And the air permeability represented by the Gurley value of the separator after the adhesive is present can be 50 sec / 100 ml or less, preferably 30 sec / 100 ml or less. As described above, in the separator of the present invention, even after the adhesive is present, it is possible to suppress an increase in air permeability from the state of only the porous substrate and maintain high ion permeability. Therefore, according to the separator of this invention, the lithium ion secondary battery which has the outstanding load characteristic can be comprised.

  Note that the air permeability of the separator is preferably 50 to 400 sec / 100 ml.

  The air permeability of the porous substrate and the separator referred to in this specification means the air permeability required by a method based on JIS P 8117.

  When the separator of the present invention is adhered to only one of the positive electrode and the negative electrode in a lithium ion secondary battery, it is sufficient that the separator has an adhesive only on one side of the porous substrate. When adhering to both the negative electrode and the negative electrode, it is sufficient that an adhesive is provided on both surfaces of the porous substrate.

  The average diameter of the fibrous portion in the adhesive is preferably 5 μm or less, and more preferably 1 μm or less. When the diameter of the fibrous portion in the adhesive is so small, it is possible to reduce the number of pores of the separator filled with the adhesive, and it is possible to configure a lithium ion secondary battery having more excellent load characteristics. In addition, although there is no restriction | limiting in particular about the lower limit of the diameter of the fibrous part in an adhesive agent, the average diameter which can be formed when the electrospinning method (after-mentioned) which is a method which can make a fiber diameter thinner is employ | adopted, It is 50 nm or more.

  The average diameter of the fibrous part of the adhesive referred to in this specification is obtained by taking five photographs at a magnification of 10,000 times using an SEM, and randomly selecting 25 fibers from among them. It is a value obtained by taking a value.

  The adhesive only needs to include a fibrous portion. For example, as shown in the SEM photograph of FIG. 1, the adhesive may partially include a bead-like (lumped) portion. Absent.

  For the porous substrate according to the separator of the present invention, for example, a porous film made of a thermoplastic resin is preferably used. When such a porous base material is used, when the inside of the battery becomes high temperature, the thermoplastic resin melts to suppress ionic conduction in the separator and to suppress the progress of the electrochemical reaction. Can be secured.

  As the thermoplastic resin constituting the porous substrate, for example, polyolefin [polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, etc.] is preferable. Moreover, as melting | fusing point of a thermoplastic resin, the thing of 80-150 degreeC is preferable with the melting temperature measured using a differential scanning calorimeter (DSC) according to the prescription | regulation of JISK7121.

  The porous film made of the thermoplastic resin as described above includes, for example, a porous film made of the above-described exemplary thermoplastic resin used in a known lithium ion secondary battery, that is, a solvent extraction method, An ion-permeable porous membrane (microporous membrane) produced by a dry or wet stretching method, a porous membrane in which thermoplastic resin fine particles are aggregated, or the like can be used.

  The porous substrate may have a single-layer structure, for example, a two-layer or three-layer structure having a layer composed of a microporous film composed of PE and a layer composed of a microporous film composed of PP. It may be a multilayer structure such as a structure.

  Further, a porous layer (I) comprising a microporous film made of a thermoplastic resin (a microporous film having a single layer structure or a microporous film having a multilayer structure) and a porous material containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher A multilayer porous membrane having the layer (II) may be used for the porous substrate. If a separator using such a multilayer porous membrane as a porous substrate is used, the shrinkage of the separator is suppressed even when the temperature inside the lithium ion secondary battery having the separator increases, and the contact between the positive electrode and the negative electrode is reduced. Therefore, a lithium ion secondary battery with higher safety can be obtained.

  As used herein, “heat-resistant temperature is 150 ° C. or higher” means that deformation such as softening is not observed at least at 150 ° C.

  In addition, since the porous layer (II) containing an inorganic filler tends to have relatively large voids, a method of applying a liquid composition (adhesive solution or adhesive dispersion) containing an adhesive to the surface thereof If the adhesive is made to adhere by the above, the composition penetrates into the porous layer (II), and there is a possibility that sufficient adhesive force cannot be secured. However, when attaching an adhesive containing a fibrous portion by the production method of the present invention to be described later, the amount of the adhesive that penetrates into the porous layer (II) can be extremely reduced. It can be set as the separator which has high adhesive force.

  In the porous substrate composed of the multilayer porous layer, the inorganic filler having a heat resistant temperature of 150 ° C. or higher contained in the porous layer (II) is preferably boehmite, alumina, silica, etc., and one of these or Two or more types can be used.

  The porous layer (II) binds the inorganic fillers to each other, or bonds the porous layer (II) and the porous layer (I) made of a thermoplastic resin microporous film. It is preferable to contain a binder for this purpose. The binder includes an ethylene-vinyl acetate copolymer (EVA, having a structural unit derived from vinyl acetate of 20 to 35 mol%), an ethylene-acrylic acid copolymer such as an ethylene-ethyl acrylate copolymer, and a fluorine-based rubber. Styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, epoxy resin, etc. Are preferred, and one or more of these can be used.

  In a porous substrate (a porous substrate made of a microporous film made of a thermoplastic resin or a porous substrate made of the multilayer porous film), the volume content of the thermoplastic resin is a porous substrate. It is preferable that it is 70-100 volume% in the whole volume (total volume except a void | hole part) of the structural component of.

  In the case of a porous substrate composed of the multilayer porous film, the content of the inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (II) is the total volume of the constituent components of the porous substrate (empty The total volume excluding the hole portion) is preferably 50% by volume or more, more preferably 70% by volume or more, still more preferably 80% by volume or more, and particularly preferably 90% by volume or more. Moreover, it is preferable that it is 99 volume% or less.

  Moreover, it is preferable that the average hole diameter of a porous base material is 0.01-0.5 micrometer. Furthermore, the porosity of the porous substrate is preferably 30 to 70%. Moreover, it is preferable that the thickness of a porous base material is 10-25 micrometers. And in the case of the porous base material which consists of the said multilayer porous membrane, it is preferable that the thickness of porous layer (II) is 3-8 micrometers.

  The porous substrate composed of the multilayer porous membrane is prepared, for example, by preparing a composition in which the constituent components of the porous layer (II) are dispersed in water or an organic solvent, and this is used as the heat for forming the porous layer (I). It can be manufactured through a step of applying to a microporous film made of a plastic resin and drying. The microporous film made of thermoplastic resin may be subjected to surface treatment such as corona discharge treatment as necessary.

  The air permeability of the porous substrate (a porous substrate made of a thermoplastic resin microporous film or a porous substrate made of the multilayer porous film) is preferably 50 to 400 sec / 100 ml.

  Examples of the adhesive in the separator of the present invention include polyethylene oxide (PEO), polypropylene oxide (PPO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). , Polymethacrylate (PMA), polymethyl methacrylate (PMMA), polyurethane, polytetrafluoroethylene (PTFE), polyvinyl acetate, polyimide (PI), polyamide (PA), polyvinyl chloride (PVC), polyether nitrile (PEN) ), Polyvinyl alcohol, PE, PP and the like, and rubber materials such as styrene butadiene rubber (SBR) and acrylic rubber can also be used. Moreover, it is also possible to use each copolymer.

  The separator of this invention can be manufactured with the manufacturing method of this invention which has the process of making the adhesive agent containing a fibrous part adhere to the single side | surface or both surfaces of a porous base material by the electrospinning method or the meltblowing method.

  If the electrospinning method or the melt-blow method is used, the adhesive can be directly attached to the surface of the porous substrate in the form of fine fibers, so even if the basis weight is reduced as described above, the surface of the porous substrate It is possible to adhere the adhesive with high uniformity throughout.

  In the case of electrospinning, an adhesive solution can be used. Solvents used for the adhesive solution include water; organic solvents such as acetone, methyl ethyl ketone (MEK), ethyl acetate, cyclohexanone, N-methyl-2-pyrrolidone (NMP), toluene, ethanol, methanol, etc. A solvent can be used. Further, the adhesive resin may be heat-melted without using a solvent.

  In order to form the adhesive in a form including a fibrous portion by electrospinning, the adhesive solution is directed from the spinneret to which a voltage of about 10 to 30 kV is applied to the surface of the porous substrate according to a conventional method. It may be discharged and then dried as necessary.

  The concentration of the adhesive solution (adhesive concentration) used in the electrospinning method is preferably 10% by mass or more.

  Further, in order to form the adhesive in a form including a fibrous portion by the melt spinning method, the adhesive melted under the heating conditions selected according to the type of the adhesive to be used is perforated from the spinneret according to a conventional method. What is necessary is just to discharge toward the surface of a quality base material.

  In the case of the electrospinning method, the diameter of the fibrous part is controlled by adjusting the concentration of the adhesive solution and the spinning speed (discharge speed from the spinneret), or the ratio of the fibrous part (in other words, , The ratio of the portion having a shape other than the fibrous shape such as a bead shape) can be controlled. In the case of the melt blow method, the diameter of the fibrous portion can be controlled or the proportion of the fibrous portion can be controlled by adjusting the melt viscosity, spinning speed, etc. of the adhesive.

  The separator obtained by attaching an adhesive containing a fibrous portion to the surface of the porous substrate may be subsequently used for the production of a lithium ion secondary battery, and after being wound up in a roll shape, etc. You may use for manufacture of a lithium ion secondary battery. In addition, when winding up a separator in roll shape, it is preferable to wind up, after bonding a release film (release paper) to the surface to which the adhesive agent of the separator was adhered.

The lithium ion secondary battery of the present invention has a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and at least one of the positive electrode and the negative electrode and the separator are integrated by an adhesive including a fibrous portion. and has a basis weight of adhesive present on the adhesive surface between the at least one and the separator of the positive electrode and the negative electrode is of 44 mg / ^{m 2} or more 2700 mg / ^{m 2} or less.

The lithium ion secondary battery of the present invention can be formed by using the separator of the present invention and integrating the separator with at least one of the positive electrode and the negative electrode with an adhesive that the separator has. In addition, the adhesive (including the positive electrode and / or the negative electrode) having an adhesive containing a fibrous portion on one side or both sides with a basis weight of 44 mg / m ² or more and 2500 mg / m ² or less per side is not attached. The lithium ion secondary battery of the present invention can also be formed by using a separator.

The basis weight of the adhesive existing between the separator and the electrode integrated with the separator is 44 mg / m ² or more, and preferably 50 mg / m ² or more. As described above with respect to the basis weight of the adhesive in the separator, in the battery of the present invention, even when such a small amount of adhesive is used, it is possible to include a fibrous portion so that the battery can be manufactured. The positional deviation between the electrode and the separator can be prevented to increase the productivity, and the positional deviation between the electrode and the separator can be prevented even in the battery, so that the reliability of the battery can be enhanced.

Also, the basis weight of the adhesive present between the separator and electrode are integrated with this, more preferably 230 mg / m ² or more, more preferably 250 mg / m ² or more. In this case, as described above with respect to the basis weight of the adhesive in the separator, when the inside of the battery becomes high temperature, the short circuit due to the contact between the positive electrode and the negative electrode, which may be caused by the shrinkage of the separator, is improved. It can be suppressed, and a battery with higher safety can be obtained.

Further, a separator, the basis weight of the adhesive present between the electrodes that are integral with it, is preferably 2700 mg / ^{m 2} or less, more preferably 2500 mg / ^{m 2} or less, 2000 mg / m More preferably, it is ² or less. By limiting the basis weight of the adhesive as described above, the number of separator holes and electrode holes that are filled with the adhesive can be reduced, and the ion permeability to these interiors can be secured well, so an excellent load It can be set as the lithium ion secondary battery which has a characteristic.

  For the positive electrode according to the lithium ion secondary battery of the present invention, for example, a positive electrode mixture layer containing a positive electrode active material, a conductive additive and a binder is used on one or both sides of the current collector. .

As the positive electrode active material, a conventionally known positive electrode active material for a lithium ion secondary battery, for example, an active material capable of inserting and extracting lithium ions is used. As a specific example of such a positive electrode active material, for example, a layered structure represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, etc.) Lithium-containing transition metal oxide, LiMn ₂ O ₄ and spinel-structured lithium manganese oxide obtained by substituting some of its elements with other elements, LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.) Type compounds. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO ₂ and LiNi _1-x Co _xy Al _y O ₂ (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0. 2) and other oxides containing at least Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiNi _{3 / 5} Mn _1/5 Co _1/5 O ₂ etc.).

  Examples of the conductive additive related to the positive electrode mixture layer include graphite (graphite carbon material) such as natural graphite (flaky graphite, etc.) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black. And carbon materials such as carbon black, carbon black, and the like. In addition, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), SBR, carboxymethylcellulose (CMC), or the like can be used for the binder related to the positive electrode mixture layer.

  As the positive electrode, for example, a paste-like or slurry-like positive electrode mixture-containing composition in which a positive electrode active material, a conductive auxiliary agent, and a binder are dispersed in a solvent such as NMP is prepared (however, the binder is dissolved in the solvent). It may be manufactured through a step of applying a calender treatment as necessary after applying it to one or both sides of the current collector and drying it. However, the positive electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.

  Moreover, you may form the current collection tab for electrically connecting with the other member in a lithium ion secondary battery as needed in a positive electrode according to a conventional method.

  The thickness of the positive electrode mixture layer is preferably, for example, 10 to 100 μm per one side of the current collector. Moreover, as a composition of a positive mix layer, it is preferable that the quantity of a positive electrode active material is 60-95 mass%, for example, it is preferable that the quantity of a binder is 1-15 mass%, and the quantity of a conductive support agent. Is preferably 3 to 20% by mass.

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

  The negative electrode according to the lithium ion secondary battery of the present invention has, for example, a negative electrode active material, a binder, and, if necessary, a negative electrode mixture layer containing a conductive auxiliary agent on one or both sides of the current collector. A structure is used.

  Examples of the negative electrode active material include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by calcining pitch; furfuryl alcohol resin ( Carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of PFA), polyparaphenylene (PPP), and phenol resins. In addition to the carbon material, lithium or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include lithium alloys such as Li—Al, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used.

  As the binder and the conductive auxiliary agent related to the negative electrode mixture layer, the same materials as those exemplified above as the binder and the conductive auxiliary agent related to the positive electrode mixture layer can be used.

  The negative electrode is prepared, for example, by preparing a paste-like or slurry-like negative electrode mixture-containing composition in which a negative electrode active material and a binder and, if necessary, a conductive additive are dispersed in a solvent such as NMP or water (however, The binder may be dissolved in a solvent), and this is applied to one or both sides of the current collector, dried, and then subjected to a calendering process as necessary. However, the negative electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.

  Moreover, you may form the current collection tab for electrically connecting with the other member in a lithium ion secondary battery as needed in a negative electrode according to a conventional method.

  The thickness of the negative electrode mixture layer is preferably 10 to 100 μm per side of the current collector per side of the current collector. Moreover, as a composition of a negative mix layer, it is preferable that the quantity of a negative electrode active material is 80-95 mass%, for example, it is preferable that the quantity of a binder is 1-20 mass%, and uses a conductive support agent. When it does, it is preferable that the quantity is 1-10 mass%.

  As the current collector 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, but a copper foil is usually 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 preferably 5 μm.

For the non-aqueous electrolyte according to the lithium ion secondary battery of the present invention, for example, a solution (non-aqueous electrolyte) in which a lithium salt is dissolved in an organic solvent can be used. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and hardly causes side reactions such as decomposition in a voltage range used as a battery. For example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ and other inorganic lithium salts, 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 (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group] and the like can be used. .

  The organic solvent used for the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; dimethoxyethane; Chain ethers such as diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile; ethylene Sulfites such as glycol sulfite; and the like. These may be used in combination of two or more. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate. In addition, for the purpose of improving safety such as improvement of charge / discharge cycle characteristics, high-temperature storage properties and prevention of overcharge, these non-aqueous electrolytes may be used in acid anhydrides, sulfonic acid esters, dinitriles, vinylene carbonates, 1,3- Additives (including these derivatives) such as propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, and t-butylbenzene may be added as appropriate.

  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.

  Moreover, you may use for the lithium ion secondary battery of this invention what added gelling agents, such as a well-known polymer, to the said nonaqueous electrolyte solution, and was made into the gel form (gel electrolyte).

The lithium ion secondary battery of the present invention is the production method of the above (1) or (2), that is,
(1) Adhesive which uses the separator for lithium ion secondary batteries of the present invention and has the separator for lithium ion secondary batteries and at least one of the positive electrode and the negative electrode in the separator for lithium ion secondary batteries A method of manufacturing a lithium ion secondary battery having a step of bonding and integrating with each other;
(2) A step of attaching an adhesive containing a fibrous portion to the surface of at least one of the positive electrode and the negative electrode by an electrospinning method or a melt blow method, and the electrode and the separator having the adhesive, A method for producing a lithium ion secondary battery comprising the steps of bonding and integrating with the adhesive;
Can be manufactured by.

  When producing a lithium ion secondary battery by the production method of (2), the separator is the same as the porous substrate according to the separator of the present invention (from a microporous membrane made of a thermoplastic resin, the multilayer porous membrane). Or a porous substrate that can be used.

  In the production method (2), an adhesive containing a fibrous portion is adhered to the surface of at least one of the positive electrode and the negative electrode by an electrospinning method or a melt blow method. This can be carried out in the same manner as described above for the manufacturing method of the separator of the invention (that is, “porous substrate” in the above description can be read as “electrode (positive electrode or negative electrode)”). Just fine).

  Usually, a positive electrode mixture layer is present on the surface of the positive electrode, and a negative electrode mixture layer is present on the surface of the negative electrode. These mixture layers are porous groups composed of the multilayer porous film described above. Similar to the porous layer (II) of the material, the porosity is relatively large, so the adhesive is applied by applying a liquid composition (adhesive solution or adhesive dispersion) containing an adhesive to the surface. When it is going to adhere, there exists a possibility that the said composition may permeate the inside of a mixture layer, and sufficient adhesive force cannot be ensured. However, in the case of attaching an adhesive containing a fibrous portion by an electrospinning method or a melt blow method, the amount of the adhesive that penetrates into the mixture layer as described above can be extremely reduced. Good adhesion can be achieved between the two.

  In both the manufacturing method of (1) and the manufacturing method of (2), in manufacturing the lithium ion secondary battery of the present invention, the positive electrode and the negative electrode are, for example, via the separator of the present invention. As a laminated body (laminated electrode body) configured by overlapping them, and a wound body (wound electrode body) obtained by winding this laminated body in a spiral shape, it is used in the lithium ion secondary battery of the present invention.

  In the case of a laminated electrode body, a method of laminating a plurality of positive electrodes and a plurality of negative electrodes via a plurality of separators can be employed. In addition to this, a plurality of positive electrodes are arranged at regular intervals on one side of a strip-shaped separator (lower separator), and a separator (upper separator) cut according to the shape of each positive electrode is formed on each positive electrode. Put the positive electrode on the lower separator after wrapping each positive electrode in the bag part by heat sealing the peripheral part of the upper separator (peripheral part of the part where the current collector tab of the positive electrode is not pulled out) It is also possible to form a laminated electrode body by arranging the negative electrode between the locations where the positive electrode is included in the bag-shaped part of the folded separator, or at the outermost part in the folded separator at the part not facing it can.

  In addition, a strip separator is used for the lower separator, and a strip separator is also used for the upper separator. A plurality of positive electrodes are arranged on one side of the lower separator at regular intervals. Put each of the separators in a bag shape by heat-sealing the lower separator and the upper separator in the vicinity of the peripheral edge of each positive electrode (near the peripheral edge of the portion where the current collecting tab of the positive electrode is not drawn). After the positive electrode is wrapped, the lower separator and the upper separator are not facing the positive electrode and are folded in a zigzag manner, and the negative electrode is formed between the portions of the folded separator containing the positive electrode in a bag-like part or at the outermost part. A laminated electrode body can also be formed by arranging the electrodes.

  FIG. 2 is a schematic diagram for explaining the structure of the laminated electrode body in a form folded in a zigzag manner. FIG. 2 is a cross-sectional view of the laminated electrode body, and shows a state where the folded portions are slightly opened to facilitate the understanding of the structure. In an actual laminated electrode body, electrodes (and separators) to be laminated are shown. They are stacked with no gaps. In FIG. 2, the separator is represented by a line in order to avoid the complexity of the drawing. Furthermore, the laminated electrode body shown in FIG. 2 is the one before the separator and the electrode are integrated.

  In the laminated electrode body shown in FIG. 2, each positive electrode 20 is included in a bag-like portion 10 a of the separator 10. And the separator 10 which included the positive electrode 20 in the bag-shaped part 10a is folded by the part (non-bag-shaped part) 10b which does not include the positive electrode 20 in zigzag folding. And the negative electrode 30 is arrange | positioned between the bag-shaped parts 10a (location which included the positive electrode 20) of the folded separator 10, and both outermost parts.

  The step of integrating the separator and at least one of the positive electrode and the negative electrode may be provided after the formation of the electrode body (laminated electrode body or wound electrode body) as described above. For example, in the case of a wound electrode body Alternatively, the positive electrode and the negative electrode may be provided via a separator and then wound in a spiral shape. In the case of a laminated electrode body folded in a zigzag manner, for example, when forming a bag-shaped portion for enclosing the positive electrode in the separator, the separator and the positive electrode may be integrated at the same time, Moreover, you may integrate the negative electrode and separator which were accumulated after that as needed.

  In the case of a laminated electrode body folded in a zigzag manner, at least one of the positive electrode and the negative electrode and the separator are integrated (particularly, both the positive electrode and the negative electrode and the separator are integrated), so that lithium ions The effect of preventing the displacement between the electrode and the separator in the subsequent manufacturing process of the secondary battery becomes more remarkable.

  The integration of the separator and the positive electrode or the negative electrode is preferably performed by press treatment. The pressure at the time of pressing is not particularly limited as long as the adhesion can be satisfactorily performed, but for example, it is preferably 0.1 MPa or more. Moreover, you may heat as needed at the time of a press process. In that case, the heating temperature varies depending on the type of adhesive to be used, but is preferably a temperature at which the constituent resin of the separator does not melt, specifically 60 ° C. or higher, preferably 80 ° C. or higher. More preferably, it is preferably 120 ° C. or lower, but from the viewpoint of better suppressing the shrinkage of the porous substrate due to heating, it is particularly preferably 100 ° C. or lower.

  A lithium ion secondary battery is assembled using the electrode body obtained through the integration process of the separator and the positive electrode or the negative electrode. With respect to the process, it is sufficient to follow a conventional method. Specifically, for example, the electrode body is inserted into the exterior body, and the current collector tab of the electrode body and the terminal in the battery are connected by welding or the like. After the water electrolyte is introduced, the outer package is sealed to obtain a lithium ion secondary battery.

  Further, for example, in the case of a lithium ion secondary battery having a laminate film (metal laminate film) described later as an exterior body, an integration step of the separator and the positive electrode or the negative electrode may be provided after the battery assembly step. . That is, after assembling the battery using the electrode body before integrating the separator and the positive electrode or the negative electrode, the separator may be integrated with the positive electrode or the negative electrode by performing a press treatment under the above conditions.

  Examples of the form of the lithium ion battery of the present invention include a cylindrical shape (such as a rectangular tube shape or a cylindrical shape) using a steel can or an aluminum can as an exterior can. In addition, the lithium ion secondary battery of the present invention can be a soft package battery using a laminate film deposited with a metal as an outer package.

  The lithium ion secondary battery of the present invention has excellent load characteristics, and can be charged and discharged with a relatively large current, such as a power source for automobiles and motorcycles, and a power source for moving bodies such as robots. It can be preferably used for various applications to which a conventionally known lithium ion secondary battery is applied, including required applications.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of separator>
By using an electrospinning method in which PVDF (molecular weight 250,000) is dissolved in dimethylformamide (DMF) at a concentration of 15% by mass and discharged from a nozzle (nozzle diameter: 0.7 mm) to which a voltage of 10 kV is applied, A belt-like separator was prepared by attaching an adhesive containing a fibrous portion to both sides of a PE microporous membrane (thickness 16 μm, porosity 45%, air permeability 250 sec / ml), which is a porous substrate. The distance between the nozzle and the PE microporous membrane was 165 mm. The basis weight of PVDF in the obtained separator was 98 mg / m ² per side, the air permeability was 251 sec / 100 ml, and the difference from the air permeability of the porous substrate was 1 sec / 100 ml. The average diameter of the fibrous portion of the adhesive in the separator was 510 nm.

<Preparation of positive electrode>
LiCoO _{2 as} positive electrode active material: 100 parts by mass, NMP solution containing PVDF as binder at a concentration of 10% by mass: 20 parts by mass, artificial graphite as conductive aid: 1 part by mass and Ketjen Black: 1 The slurry was mixed with a mass part using a planetary mixer, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing slurry.

  The positive electrode mixture-containing slurry is applied to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, and then vacuum-dried at 120 ° C. for 12 hours to form a positive electrode mixture layer on both surfaces of the aluminum foil. Formed. When the positive electrode mixture layer was formed, a part of the aluminum foil was left to be an exposed portion. Thereafter, calendering is performed to adjust the thickness and density of the positive electrode mixture layer, and then the exposed portion of the current collector is included, and the positive electrode mixture layer is cut into a shape of 65 mm × 110 mm, and the positive electrode is removed. Obtained.

<Production of negative electrode>
Water is added to 97.5 parts by mass of natural graphite having a number average particle diameter of 10 μm as a negative electrode active material, 1.5 parts by mass of SBR as a binder, and 1 part by mass of CMC as a thickener. 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. When the negative electrode mixture layer was formed, a part of the copper foil was left to be an exposed portion. Then, after adjusting the thickness and density of the negative electrode mixture layer by calendering, the portion including the exposed portion of the current collector and forming the negative electrode mixture layer was cut into a 67 mm × 112 mm shape, A negative electrode was obtained.

<Formation of laminated electrode body>
Place where the positive electrodes are arranged at intervals of 2 mm on the strip separator (lower separator), the strip separator (upper separator) is stacked on each positive electrode, and the positive electrode is disposed below the upper separator The negative electrode was placed on the substrate, folded in a zigzag shape, and the separator was cut at a predetermined location to obtain a laminated electrode body having six positive electrodes and seven negative electrodes.

<Battery assembly>
The laminated electrode body is sandwiched between two aluminum laminate films (115 × 70 mm), three sides of both laminated films placed above and below the laminated electrode body are heat-sealed, and vacuum-dried at 60 ° C. for one day. After that, LiPF ₆ was dissolved at a concentration of 1.2 mol / l in a non-aqueous electrolyte (a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7) from the remaining one side of both laminate films. Solution).

Next, the laminated electrode body was pressed from the outside of both laminated films (pressure 25 kgf / cm ² , temperature 100 ° C., pressing time 3 minutes), and the electrode and the separator were integrated. Thereafter, the remaining one side of both laminate films was vacuum-sealed to obtain a lithium ion secondary battery having the structure shown in FIG. 4 with the appearance shown in FIG.

  Here, FIG. 3 and FIG. 4 will be described. FIG. 3 is a plan view schematically showing a lithium ion secondary battery, and FIG. 4 is a cross-sectional view taken along line AA of FIG. The lithium ion secondary battery 100 has a positive electrode 20, a negative electrode 30, and a separator 10 in a laminate film outer package 200 composed of two laminate films, and a laminated electrode body having a structure folded in a zigzag manner, An electrolyte solution (not shown) is accommodated, and the laminate film outer package 200 is sealed by heat-sealing the upper and lower laminate films at the outer peripheral portion thereof. In FIG. 4, the layers constituting the laminate film outer package 200 and the layers of the positive electrode 20 and the negative electrode 30 are not shown separately in order to prevent the drawing from becoming complicated.

  Each positive electrode 20 is connected to a positive electrode external terminal 21 by a current collecting tab in the battery 100, and each negative electrode 30 is also connected to a negative electrode external terminal 31 by a current collecting tab in the battery 100. doing. The positive electrode external terminal 21 and the negative electrode external terminal 31 are drawn out to the outside of the laminate film exterior body 200 so that they can be connected to an external device or the like.

Comparative Example 1
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the PE microporous membrane used in the production of the separator in Example 1 was used as a separator without attaching an adhesive to the surface.

Examples 2 to 6 and Comparative Example 2
A separator was prepared in the same manner as in Example 1 except that the basis weight per side of PVDF as an adhesive was changed as shown in Table 1, and lithium ions were obtained in the same manner as in Example 1 except that these separators were used. A secondary battery was produced.

  About the lithium ion secondary battery of Examples 1-6 and Comparative Examples 1 and 2, discharge capacity was measured with the following method.

  About each lithium ion secondary battery of an Example and a comparative example, it carries out constant current charge to 4.2V with the electric current value of 0.2C, and then it is constant voltage until the electric current value becomes 0.05C with the voltage of 4.2V. After charging, discharging was performed at a current value of 0.2 C until the voltage became 2.5 V, and a discharge capacity (0.2 C discharge capacity) was obtained.

  For each battery after measuring the 0.2C discharge capacity, perform constant current charging and constant voltage charging under the same conditions as when measuring the 0.2C discharge capacity, and then discharge until the voltage reaches 2.5V at a current value of 4C. The discharge capacity (4C discharge capacity) was determined.

  The 0.2 C discharge capacity and the 4 C discharge capacity obtained for each battery are expressed as relative values when the 0.2 C discharge capacity in the battery of Comparative Example 1 (battery using a separator having no adhesive) is 100. Compared.

  In addition, the lithium ion secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2 were subjected to constant current charging and constant voltage charging under the same conditions as when measuring the discharge capacity, and then a predetermined temperature (130 ° C. and 150 ° C.). Safety was evaluated by the presence or absence of thermal runaway when stored in an oven adjusted for 3 hours.

  The structure of the separator used for the lithium ion secondary battery of Examples 1-6 and Comparative Examples 1 and 2 is shown in Table 1, the measurement result of 0.2 C discharge capacity and 4 C discharge capacity of these batteries, and safety evaluation The results are shown in Table 2.

  In Table 1, “difference in air permeability” means the difference between the air permeability of the separator and the air permeability of the porous substrate (the same applies to Tables 3 and 5 below). In Table 1, “Adhesive weight” means the weight per one side of the porous substrate of the adhesive including the fibrous portion (the same applies to Tables 3 and 5 described later). ).

  In the “safety evaluation” in Table 2, “◯” indicates a battery in which thermal runaway did not occur in the above test, and “x” indicates a battery in which thermal runaway occurred (see Tables 4, 6 and 6 below). 8 is the same).

  As shown in Table 1 and Table 2, an example using a separator in which an adhesive containing a fibrous portion was present on the surface with an appropriate basis weight and the difference in air permeability from the porous substrate was an appropriate value. The lithium ion secondary batteries 1 to 6 had a large 4C discharge capacity and had excellent load characteristics.

  On the other hand, the battery of Comparative Example 2 using a separator in which the basis weight of the adhesive including the fibrous portion is too large and the difference in air permeability with the porous base material is too large is 4C compared to the battery of the example. The discharge capacity was small and the load characteristics were inferior.

  In addition, in the lithium ion secondary batteries of Examples 1 to 6, the positive electrode, the negative electrode, and the separator are satisfactorily integrated by the adhesive that the separator has, and it is difficult for the positive electrode, the negative electrode, and the separator to be misaligned in the battery. Had high reliability. Furthermore, the lithium ion secondary batteries of Examples 2 to 6 using the separator having a more suitable basis weight of the adhesive including the fibrous portion can be heated even if stored in a high temperature environment such as 150 ° C. for 3 hours. There was no runaway and the safety was higher.

Example 7
PE, which is a porous substrate, is obtained by an electrospinning method in which a solution obtained by dissolving PVDF-HFP in acetone at a concentration of 10% by mass is discharged from a nozzle (nozzle diameter: 0.7 mm) to which a voltage of 10 kV is applied. A strip separator was prepared by attaching an adhesive containing a fibrous portion to both surfaces of a microporous membrane (thickness 16 μm, porosity 45%, air permeability 250 sec / ml). The distance between the nozzle and the PE microporous membrane was 165 mm. The basis weight of PVDF-HFP in the obtained separator was 89 mg / m ² per side, the air permeability was 251 sec / 100 ml, and the difference from the air permeability of the porous substrate was 1 sec / 100 ml. Moreover, the average diameter of the fibrous portion of the adhesive in the separator was 310 nm.

  And the lithium ion secondary battery was produced like Example 1 except having used the above-mentioned separator.

Examples 8-12 and Comparative Example 3
A separator was prepared in the same manner as in Example 7 except that the basis weight per side of PVDF-HFP as an adhesive was changed as shown in Table 3, and the same procedure as in Example 7 was performed except that these separators were used. A lithium ion secondary battery was produced.

  About each lithium ion secondary battery of Examples 7-12 and the comparative example 3, by the same method as the battery of Example 1, the measurement of 0.2C discharge capacity and 4C discharge capacity, and safety evaluation were performed. The 0.2C discharge capacity and 4C discharge capacity of each battery are expressed as relative values when the 0.2C discharge capacity in the battery of Comparative Example 1 (battery using a separator having no adhesive) is set to 100. Compared.

  The structures of the separators used in the lithium ion secondary batteries of Examples 7 to 12 and Comparative Example 3 are shown in Table 3, and the measurement results of 0.2C discharge capacity and 4C discharge capacity of these batteries, and the safety evaluation results are shown. Table 4 shows. Table 3 also shows the configuration of the separator relating to the battery of Comparative Example 1, and Table 4 also shows the measurement results of the 0.2C discharge capacity and 4C discharge capacity of the battery of Comparative Example 1 and the safety evaluation results. To do.

  As shown in Table 3 and Table 4, an example using a separator in which an adhesive containing a fibrous portion was present on the surface with an appropriate basis weight and the difference in air permeability from the porous substrate was an appropriate value. The 7-12 lithium ion secondary batteries had a large 4C discharge capacity and had excellent load characteristics.

  On the other hand, the battery of Comparative Example 3 using a separator in which the basis weight of the adhesive including the fibrous portion is too large and the difference in air permeability with the porous base material is too large is 4C than the battery of the example. The discharge capacity was small and the load characteristics were inferior.

  In addition, in the lithium ion secondary batteries of Examples 7 to 12, the positive electrode, the negative electrode, and the separator are satisfactorily integrated by the adhesive that the separator has, and it is difficult for the positive electrode, the negative electrode, and the separator to be misaligned in the battery. Had high reliability. Further, the lithium ion secondary batteries of Examples 8 to 12 using the separator having a more suitable basis weight of the adhesive including the fibrous portion can be heated even if stored in a high temperature environment such as 150 ° C. for 3 hours. There was no runaway and the safety was higher.

Example 13
Add 5 kg of ion-exchanged water and 0.5 kg of a dispersant (aqueous polycarboxylic acid ammonium salt, solid content concentration 40 mass%) to 5 kg of boehmite with an average particle diameter D of _50% of 1 μm. Dispersion was prepared by crushing for 10 hours with a ball mill at times / minute. The treated dispersion was vacuum-dried at 120 ° C. and observed with a scanning electron microscope (SEM). As a result, the boehmite was almost plate-shaped.

  To 500 g of the above dispersion, 0.5 g of xanthan gum as a thickener and 17 g of a resin binder dispersion (modified polybutyl acrylate, solid content 45% by mass) as a binder are added and stirred with a three-one motor for 3 hours to form a uniform slurry. [Slurry for forming porous layer (II), solid content ratio: 50% by mass] was prepared.

PE microporous separator for non-aqueous secondary battery [Porous layer (I): Thickness 12 μm, porosity 40%, average pore diameter 0.08 μm, PE melting point 135 ° C.] corona discharge treatment (discharge amount) 40 W · min / m ² ), a porous layer (II) forming slurry is applied to the treated surface by a micro gravure coater, and dried to form a porous layer (II) having a thickness of 4 μm. A porous membrane was obtained. The mass per unit area of the porous layer (II) in this multilayer porous membrane is 5.5 g / m ² , the boehmite volume content is 95% by volume, and the porosity is 45%. The degree was 259 sec / 100 ml.

A separator was produced in the same manner as in Example 1 except that the porous substrate was changed to the multilayer porous film. The basis weight of PVDF in the obtained separator was 108 mg / m ² per side, the air permeability was 261 sec / 100 ml, and the difference from the air permeability of the porous substrate was 2 sec / 100 ml. The average diameter of the fibrous portion of the adhesive in the separator was 510 nm.

  And the maintenance battery was produced in lithium ion like Example 1 except having used the above-mentioned separator. In forming the laminated electrode body, the separator was disposed so that the porous layer (II) of the multilayer porous membrane as the porous substrate was on the positive electrode side.

Comparative Example 4
A lithium ion secondary battery was produced in the same manner as in Example 13 except that the multilayer porous membrane used in the production of the separator in Example 13 was used as a separator without attaching an adhesive to the surface.

Examples 14 to 18 and Comparative Example 5
A separator was produced in the same manner as in Example 13 except that the basis weight per side of PVDF as an adhesive was changed as shown in Table 5, and lithium ions were obtained in the same manner as in Example 13 except that these separators were used. A secondary battery was produced.

  For each of the lithium ion secondary batteries of Examples 13 to 18 and Comparative Examples 4 and 5, measurement of 0.2C discharge capacity and 4C discharge capacity and safety evaluation were performed in the same manner as the battery of Example 1. It was. The 0.2C discharge capacity and 4C discharge capacity of each battery are expressed as relative values when the 0.2C discharge capacity in the battery of Comparative Example 4 (battery using a separator having no adhesive) is set to 100. Compared.

  The structures of the separators used in the lithium ion secondary batteries of Examples 13 to 18 and Comparative Examples 4 and 5 are shown in Table 5. The measurement results of 0.2C discharge capacity and 4C discharge capacity of these batteries, and safety evaluation The results are shown in Table 6.

  As shown in Table 5 and Table 6, an example using a separator in which an adhesive containing a fibrous portion was present on the surface with an appropriate basis weight and the difference in air permeability with the porous substrate was an appropriate value The 13-18 lithium ion secondary batteries had a large 4C discharge capacity and excellent load characteristics.

  On the other hand, the battery of Comparative Example 5 using a separator in which the basis weight of the adhesive including the fibrous portion is too large and the difference in air permeability with the porous substrate is too large is 4C than the battery of the example. The discharge capacity was small and the load characteristics were inferior.

  In the lithium ion secondary batteries of Examples 13 to 18, the positive electrode, the negative electrode, and the separator are satisfactorily integrated by the adhesive that the separator has, and it is difficult for the positive electrode, the negative electrode, and the separator to be misaligned in the battery. Had high reliability. Furthermore, the lithium ion secondary batteries of Examples 14 to 18 using separators having a more suitable basis weight of the adhesive including the fibrous portion were heated even when stored in a high temperature environment such as 150 ° C. for 3 hours. There was no runaway and the safety was higher.

Example 19
By using an electrospinning method in which PVDF (molecular weight 250,000) is dissolved in dimethylformamide (DMF) at a concentration of 15% by mass and discharged from a nozzle (nozzle diameter: 0.7 mm) to which a voltage of 10 kV is applied, An adhesive containing a fibrous portion was attached to both surfaces of the same positive electrode as that prepared in Example 1. The distance between the nozzle and the positive electrode was 165 mm. The basis weight of PVDF in the obtained positive electrode was 79 mg / m ² per side.

Moreover, the adhesive agent containing a fibrous part was made to adhere to both surfaces of the same negative electrode as what was produced in Example 1 similarly to the said positive electrode. The basis weight of PVDF in the obtained negative electrode was 100 mg / m ² per side.

  For the production of a separator in Example 1, using the positive electrode having an adhesive containing a fibrous part attached on both sides and the negative electrode having an adhesive containing a fibrous part attached on both sides A lithium ion secondary battery was produced in the same manner as in Example 1 except that the same PE microporous membrane as that used was used for the separator as it was.

Examples 20 to 24 and Comparative Example 6
Except for changing the basis weight per one side as shown in Table 7, the adhesive containing the fibrous portion was attached to both sides of the positive electrode and the negative electrode in the same manner as in Example 19, except that these positive electrode and negative electrode were used. A lithium ion secondary battery was produced in the same manner as in Example 19.

  About each lithium ion secondary battery of Examples 19-24 and the comparative example 6, the measurement of 0.2C discharge capacity and 4C discharge capacity and the safety | security evaluation were performed by the same method as the battery of Example 1, etc. The 0.2 C discharge capacity and 4 C discharge capacity of each battery are relative values when the 0.2 C discharge capacity in the battery of Comparative Example 1 (battery using a positive electrode and a negative electrode without an adhesive) is 100. Expressed and compared.

  Table 7 shows the basis weight per one side of the adhesives including the fibrous portions in the positive electrode and the negative electrode used in the lithium ion secondary batteries of Examples 19 to 24 and Comparative Example 6, and 0.2C discharge of these batteries. Table 8 shows the measurement results of the capacity and the 4C discharge capacity, and the safety evaluation results. In Table 8, the measurement results of the 0.2C discharge capacity and 4C discharge capacity of the battery of Comparative Example 1 and the safety evaluation results are also shown.

  In Table 7, “Adhesive weight” means the weight per one side of the positive electrode or negative electrode of the adhesive containing the fibrous portion.

  As shown in Table 7 and Table 8, the lithium ion secondary batteries of Examples 7 to 12 using the positive electrode and the negative electrode in which the adhesive containing the fibrous portion was present on the surface with proper weight were used with a 4C discharge capacity. It was large and had excellent load characteristics.

  On the other hand, the battery of Comparative Example 6 using the positive electrode and the negative electrode, which have a too large basis weight of the adhesive including the fibrous portion, had a 4C discharge capacity smaller than the battery of the example and inferior load characteristics.

  In addition, in the lithium ion secondary batteries of Examples 19 to 24, the positive electrode, the negative electrode, and the separator are well integrated by the adhesive of the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the separator are misaligned in the battery. It was hard to occur and had high reliability. Furthermore, the lithium ion secondary batteries of Examples 20 to 24 using the positive electrode and the negative electrode having a more suitable value of the adhesive weight including the fibrous part are stored in a high temperature environment such as 150 ° C. for 3 hours. However, no thermal runaway occurred and the safety was higher.

10 Separator 10a Separator bag-shaped portion 20 Positive electrode 30 Negative electrode 100 Lithium ion secondary battery

Claims (9)

A separator used in a lithium ion secondary battery in which an electrode and a separator are integrated,
An adhesive containing a fibrous part is attached to one or both sides of the porous substrate,
The basis weight of the adhesive per side of the porous substrate is 44 to 2700 mg / m ² ;
The difference between the air permeability represented by the Gurley value of the porous substrate and the air permeability represented by the Gurley value of the separator is 50 sec / 100 ml or less. Separator.   The separator for a lithium ion secondary battery according to claim 1, wherein an average diameter of the fibrous portion of the adhesive is 5 μm or less.   3. The separator for a lithium ion secondary battery according to claim 1, wherein the adhesive is polyvinylidene fluoride or a vinylidene fluoride-hexafluoropropylene copolymer.   The porous substrate is a multilayer porous film having a porous layer (I) composed of a microporous film made of a thermoplastic resin and a porous layer (II) containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher. The separator for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the adhesive is attached to the surface of the porous layer (II). A lithium ion secondary battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte,
At least one of the positive electrode and the negative electrode and the separator are integrated by an adhesive including a fibrous portion,
The lithium ion secondary battery, wherein a basis weight of the adhesive existing on an adhesive surface between at least one of the positive electrode and the negative electrode and the separator is 44 to 2700 mg / m ² .   The lithium ion secondary battery according to claim 4, wherein the adhesive is polyvinylidene fluoride or a vinylidene fluoride-hexafluoropropylene copolymer. A method for producing a separator for a lithium ion secondary battery according to any one of claims 1 to 3,
The manufacturing method of the separator for lithium ion secondary batteries which has the process of making the adhesive agent containing a fibrous part adhere to the single side | surface or both surfaces of a porous base material by the electrospinning method or the melt blow method. It is a manufacturing method of the lithium ion secondary battery according to claim 5 or 6,
The lithium ion secondary battery separator according to any one of claims 1 to 3, wherein the lithium ion secondary battery separator and at least one of a positive electrode and a negative electrode are used for the lithium ion secondary battery. A method for producing a lithium ion secondary battery, comprising a step of bonding and integrating with an adhesive of a separator. It is a manufacturing method of the lithium ion secondary battery according to claim 5 or 6,
Attaching an adhesive containing a fibrous portion to the surface of at least one of the positive electrode and the negative electrode by an electrospinning method or a melt-blowing method;
A method for producing a lithium ion secondary battery, comprising: a step of bonding and integrating the electrode having the adhesive and the separator with the adhesive.