JP6936419B2 - Electrodes for lithium-ion secondary batteries and lithium-ion secondary batteries - Google Patents

Description

The present invention relates to an electrode for a lithium ion secondary battery having an insulating layer arranged adjacent to the end portion of the electrode active material layer and arranged so as to cover the end portion, and a lithium ion secondary battery.

Lithium-ion secondary batteries are used as large-scale stationary power sources for power storage, power sources for electric vehicles, etc., and in recent years, research on miniaturization and thinning of batteries has been progressing. A lithium ion secondary battery generally includes both electrodes having an electrode active material layer formed on the surface of a metal foil and a separator arranged between the electrodes. The separator plays a role of preventing a short circuit between both electrodes and holding an electrolytic solution.

In a lithium ion secondary battery, the occurrence rate of short circuits is particularly high near the end of the active material layer on the current collector. On the other hand, in order to more reliably prevent a short circuit between both electrodes, a non-aqueous secondary battery in which a portion having a high occurrence rate of the short circuit is coated with an insulating tape is known as a prior art (for example, Patent Document). 1). In the non-aqueous secondary battery described in Patent Document 1, an insulating tape is attached to the boundary portion between the exposed portion of the current collector and the coating portion of the positive electrode mixture layer to prevent an internal short circuit.

JP-A-2009-134915

The electrode for a lithium ion secondary battery may have burrs at its end due to, for example, cutting during manufacturing. However, in the case of a laminated battery, if there is a burr at the end of the electrode, the burr of the electrode may break through the insulating tape provided on the electrode facing the electrode, causing a short circuit between the two electrodes.

Therefore, it is an object of the present invention to provide an electrode for a lithium ion secondary battery capable of reliably preventing a short circuit between both electrodes even if the electrode has burrs, and a lithium ion secondary battery provided with the electrode. ..

As a result of diligent studies, the present inventor has determined that the insulating layer arranged adjacent to the end portion of the electrode active material layer and covering the end portion has a predetermined tensile elastic modulus and elongation at break. We have found that the problem can be solved and completed the following invention. The gist of the present invention is the following [1] to [11].
[1] A current collector and an electrode active material layer and an insulating layer provided on the surface of the current collector are provided.
An electrode for a lithium ion secondary battery in which the insulating layer is provided so as to be adjacent to and cover the end of the electrode active material layer.
The insulating layer is lithium having a tensile elastic modulus of 2.0 to 7.0 GPa measured according to JIS K 7161 and a breaking elongation of 15% or more measured according to JIS K 7161. Electrode for ion secondary battery.
[2] The electrode for a lithium ion secondary battery according to the above [1], wherein the insulating layer contains a polyimide resin.
[3] The electrode for a lithium ion secondary battery according to the above [2], wherein the insulating layer further contains a fluororesin.
[4] The lithium ion secondary battery according to the above [2] or [3], wherein the content of the polyimide resin in the insulating layer is 45% by mass or more and 100% by mass or less based on the total amount of the insulating layer. electrode.
[5] The item according to any one of [1] to [4] above, wherein the insulating layer is an insulating coating layer coated on the surface of the current collector and the end portion of the electrode active material layer. Electrode for lithium ion secondary battery.
[6] The electrode for a lithium ion secondary battery according to any one of the above [1] to [5], wherein the current collector is formed of any one selected from aluminum and stainless steel.
[7] The electrode for a lithium ion secondary battery according to any one of the above [1] to [6], wherein the adhesion strength between the insulating layer and the current collector is 200 N / m or more.
[8] The electrode for a lithium ion secondary battery according to any one of the above [1] to [7], wherein the electrode active material layer is a positive electrode active material layer.
[9] A lithium ion secondary battery comprising the electrode for the lithium ion secondary battery according to any one of the above [1] to [8].
[10] A negative electrode and a positive electrode are provided.
The lithium ion secondary battery according to the above [9], wherein the positive electrode is an electrode for the lithium ion secondary battery.
[11] The positive electrode and the negative electrode are alternately arranged so that a plurality of layers are provided, and the ends of the current collectors of the positive electrodes constituting each layer are collectively connected to the positive electrode terminal and constitute each layer. A lithium-ion secondary battery in which the ends of the current collectors of each of the negative electrodes are grouped together and connected to the negative electrode terminals.
At least one of the positive electrode and the negative electrode is composed of the electrode for a lithium ion secondary battery.
The lithium ion secondary battery according to claim 9 or 10, wherein the insulating layer is arranged so as to be adjacent to the end portion of the electrode active material layer on the bundled end side of the current collector.

According to the present invention, it is possible to provide an electrode for a lithium ion secondary battery capable of reliably preventing a short circuit between both electrodes even if there is a burr at the end of the electrode, and a lithium ion secondary battery provided with the electrode. ..

FIG. 1A is a schematic cross-sectional view of an electrode for a lithium ion secondary battery according to an embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view of the electrode for a lithium ion secondary battery according to an embodiment of the present invention. It is a schematic plan view. It is a figure which shows an example of the die head used for coating the raw material for an insulating layer. It is a figure for demonstrating the application of the raw material for an insulating layer. It is a figure for demonstrating division of the current collector which formed the electrode active material layer and the insulating layer. It is schematic cross-sectional view of the modification of the electrode for a lithium ion secondary battery in one Embodiment of this invention. It is schematic cross-sectional view of the modification of the electrode for a lithium ion secondary battery in one Embodiment of this invention. It is the schematic sectional drawing of the lithium ion secondary battery in one Embodiment of this invention. It is schematic cross-sectional view of the modification of the lithium ion secondary battery in one Embodiment of this invention. It is a figure for demonstrating the apparatus used for the short circuit test of an Example.

[Electrodes for lithium-ion secondary batteries]
Hereinafter, the electrode for a lithium ion secondary battery according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of an electrode for a lithium ion secondary battery according to an embodiment of the present invention.
As shown in FIG. 1, the electrode 10 for a lithium ion secondary battery according to the embodiment of the present invention includes a current collector 20, an electrode active material layer 30 and an insulating layer provided on the surfaces of both sides of the current collector 20. 40 and. Each insulating layer 40 is arranged so as to be adjacent to the end portion 31 of the electrode active material layer 30 and to cover the end portion 31 thereof. As a result, the insulating layer 40 is provided so as to straddle the surface of the electrode active material layer 30 and the surface of the current collector 20 in which the electrode active material layer 30 is not provided. Further, the insulating layer 40 is provided so as to cover only the end portion of the electrode active material layer 30, and the portion other than the end portion does not have to be covered by the insulating layer 40.

In the present invention, the insulating layer 40 has a tensile elastic modulus of 2.0 to 7.0 GPa measured according to JIS K 7161 and a breaking elongation of 15% or more measured according to JIS K 7161. Is.
In the present invention, by covering the electrode active material layer 30 with an insulating layer 40 having a predetermined tensile elastic modulus and a predetermined elongation at break, even if there is a burr at the end of another electrode facing the electrode 10, the burr is the burr. Is less likely to break through the insulating layer 40. Therefore, it is possible to prevent a short circuit between the two electrodes due to electrode burrs.

(Insulation layer)
The insulating layer 40 is a layer provided for surely preventing a short circuit between the positive electrode and the negative electrode. As described above, the insulating layer 40 is arranged so as to be adjacent to the end portion 31 of the electrode active material layer 30 and to cover the end portion 31 thereof. As a result, if there are burrs on the opposing electrodes, the burrs will come into contact with the insulating layer 40. Then, since the burr is less likely to penetrate the insulating layer 40, a short circuit due to the burr of the electrode can be reliably prevented.

The insulating layer 40 has a tensile elastic modulus of 2.0 to 7.0 GPa measured according to JIS K 7161 and a breaking elongation of 15% or more measured according to JIS K 7161. If the tensile elastic modulus of the insulating layer 40 is less than 2.0 GPa, or greater than 7.0 GPa, or the elongation at break is less than 15%, the strength and flexibility of the insulating layer 40 are insufficient, and the opposing electrodes have insufficient strength and flexibility. The insulating layer 40 is pierced by the burrs, and a short circuit due to the burrs is likely to occur. In addition, the adhesion strength tends to decrease.

From the viewpoint of more reliably preventing the occurrence of a short circuit, the tensile elastic modulus is preferably 2.5 GPa or more, more preferably 3.0 GPa or more, and it is easy to set the breaking elongation and the adhesion strength with the current collector to a certain value or more. From this point of view, the tensile elastic modulus is preferably 6.7 GPa or less, more preferably 6.2 GPa or less.
From the viewpoint of more reliably preventing the occurrence of a short circuit and facilitating the enhancement of the adhesion strength to the current collector, the breaking elongation is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more. Further, from the viewpoint of facilitating the tensile elastic modulus within a predetermined range, 200% or less is preferable, 150% or less is more preferable, and 120% or less is further preferable.

The tensile elastic modulus and the elongation at break of the insulating layer formed on the current collector can be measured, for example, by removing the current collector by chemical etching. For chemical etching, for example, an etching solution such as a ferric chloride aqueous solution, a cupric chloride aqueous solution, or a hydrogen peroxide solution / dilute sulfuric acid solution can be used.

The adhesion strength between the insulating layer 40 and the current collector 20 is preferably 200 N / m or more. When the adhesion strength is 200 N / m or more, it is possible to prevent the insulating layer 40 from peeling off and improve the reliability of the insulating layer 40. In addition, it is possible to more reliably prevent the occurrence of a short circuit due to electrode burrs. From these viewpoints, the adhesion strength is more preferably 300 N / m or more, further preferably 430 N / m or more. Further, the adhesion strength may be high as long as it is high, but practically, it may be, for example, 2000 N / m or less, or 1200 N / m or less.

The insulating layer 40 in the present invention is preferably made of a resin. That is, the insulating layer 40 is preferably an insulating resin layer. Since the insulating layer 40 is made of resin, it becomes easy to adjust the breaking elongation, tensile elastic modulus, and adhesion strength of the insulating layer 40 within a predetermined range while ensuring the insulating property of the insulating layer.
The resin constituting the insulating layer 40 is not particularly limited as long as the above-mentioned breaking elongation and tensile elasticity can be adjusted within a predetermined range while ensuring the insulating property, but is not particularly limited, but is a fluororesin, a polyimide resin, and a polymethyl acrylate (PMA). ), Polymethylmethacrylate (PMMA) and other acrylic resins, polyvinyl acetate, polyamide (PA), polyvinyl chloride (PVC), polyether nitrile (PEN), polyethylene (PE), polypropylene (PP), polyacrylonitrile (PAN). ), Acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), poly (meth) acrylic acid, carboxymethyl cellulose (CMC), hydroxyethyl cellulose, polyvinyl alcohol and the like. These binders may be used alone or in combination of two or more. Further, carboxymethyl cellulose and the like may be used in the form of a salt such as a sodium salt.

The resin constituting the insulating layer is preferably a polyimide resin from the viewpoint of facilitating the elongation at break and the tensile elastic modulus within a desired range. Further, the adhesion strength can be easily improved by using the polyimide resin.
The polyimide-based resin is a polymer containing an imide bond in a repeating unit, and may be a polyimide, a polyamide-imide having an imide bond and an amide bond, a polyetherimide having an imide bond and an ether bond, and the like. May be good. Of these, polyamideimide and polyetherimide are preferable.
Further, the polyimide-based resin is preferably an aromatic polyimide-based resin having an aromatic ring directly bonded by an imide bond. By using the aromatic polyimide-based resin, the tensile elastic modulus and the elongation at break of the insulating layer can be easily adjusted within the above-mentioned predetermined ranges.
The polyimide resin may be used by appropriately selecting the molecular weight and the type of resin so that the tensile elastic modulus and the elongation at break of the insulating layer are within a desired range. For example, it can be improved by introducing rigid molecules into the molecular skeleton in order to improve the elastic modulus of the insulating layer. In order not to improve the elastic modulus too much, it is effective to introduce an ether skeleton capable of rotational movement, an isopropylidene skeleton, an aliphatic chain, and a benzophenone or a sulfonyl group having a twisted skeleton having a large free volume between molecules. be. In order to improve the elongation at break, it is necessary to improve the entanglement of the molecular chains, and the number average molecular weight (Mn) is preferably 5000 or more, more preferably 10000 or more. The upper limit of the number average molecular weight (Mn) is not particularly limited and may be, for example, 500,000 or less, but may be 100,000 or less. The weight average molecular weight can be measured in terms of polystyrene using, for example, gel permeation chromatography (GPC). In order not to improve the elastic modulus too much, a rigid molecule may be introduced into the molecular skeleton in the same manner as the means for improving the elastic modulus.
Commercially available products can also be used as the polyimide resin, and examples thereof include "Vilomax" manufactured by Toyobo Co., Ltd. as a polyamide-imide and "ULTEM" manufactured by SABIC as a polyetherimide.
The polyimide resin may be used alone or in combination of two or more.

When a polyimide resin is used, the entire amount of the resin component constituting the insulating layer may be composed of the polyimide resin, but both the polyimide resin and other resin components may be used. By using another resin component, it becomes easy to impart various functions to the insulating layer, and for example, it becomes easy to increase the above-mentioned breaking elongation while maintaining the tensile elastic modulus within a predetermined range.
Whether or not the insulating layer contains a polyimide resin can be determined by measuring the infrared absorption spectrum on the surface of the insulating layer, as shown in Examples described later.

The content of the polyimide resin in the insulating layer is preferably 30% by mass or more based on the total amount of the insulating layer. When it is set to 30% by mass or more, the tensile elastic modulus and the elongation at break can be easily adjusted within the above-mentioned predetermined ranges. The content of the polyimide resin is more preferably 45% by mass or more, further preferably 50% by mass or more.
The content of the polyimide resin in the insulating layer may be 100% by mass or less, but when a resin other than the polyimide resin is contained, the effect of containing the resin other than the polyimide resin is exhibited. In addition, 90% by mass or less is preferable, 75% by mass or less is preferable, and 60% by mass or less is more preferable.

When a polyimide resin and a resin other than the polyimide resin are used in combination as the resin constituting the insulating layer, the resin other than the polyimide resin is preferably a fluororesin. By using the fluororesin, it becomes easy to improve the breaking elongation and the adhesion strength to the current collector and the electrode active material layer while ensuring the insulating property of the insulating layer. From these viewpoints, when the insulating layer contains a fluororesin, the content of the fluororesin is preferably 10% by mass or more based on the total amount of the insulating layer. When it is set to 10% by mass or more, it becomes easy to improve the elongation at break while maintaining the tensile elastic modulus and the adhesion strength to the current collector and the electrode active material layer within a desired range. From these viewpoints, the content of the fluororesin is more preferably 25% by mass or more, further preferably 40% by mass or more.
The content of the fluororesin in the insulating layer is preferably 70% by mass or less, more preferably 55% by mass or less, from the viewpoint of tensile elastic modulus, elongation at break, and adhesion strength to the current collector and the electrode active material layer.

As the fluororesin used in the insulating layer, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), fluorinated polyimide and the like can be used. Of these, polyvinylidene fluoride (PVdF) is preferable. The fluororesin may be used alone or in combination of two or more.

The insulating layer is a layer formed by forming a film-like resin component, and may be composed of the resin component alone, or may be appropriately blended with additional components as long as the effects of the present invention are exhibited. The content of the resin component in the insulating layer is, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more based on the total amount of the insulating layer.

Examples of the additive component used in the insulating layer include a filler. Further, as the additive component, in addition to the filler, a known additive that can be used in combination with a resin component such as a polyimide resin may be used.
The filler is not particularly limited as long as it is an insulating filler having an insulating property, but silicon dioxide, silicon nitride, alumina, boehmite, titania, zirconia, boron nitride, zinc oxide, tin dioxide, niobium oxide (Nb ₂ O ₅ ), Examples thereof include inorganic particles composed of inorganic compounds such as tantalum oxide (Ta ₂ O ₅ ), potassium fluoride, lithium fluoride, clay, zeolite, and calcium carbonate. The inorganic particles may be particles composed of known composite oxides such as niobium-tantalum composite oxide and magnesium-tantalum composite oxide. Further, the filler may be organic particles.

The insulating layer 40 is preferably an insulating coating layer coated on the surface of the current collector 20 and the end portion of the electrode active material layer 30. As will be described later, the insulating coating layer is formed by applying a liquid or fluid insulating layer raw material to a current collector and solidifying or curing the insulating layer raw material to form the surface of the current collector 20 and the current collector 20. The end portion of the electrode active material layer 30 is coated. Therefore, the insulating layer 40 is not attached to the current collector by an adhesive tape such as an insulating tape, and the thickness of the insulating layer 40 can be reduced. In addition, the adhesion strength to the current collector 20 and the electrode active material layer 30 can be easily increased.

The thickness of the insulating layer 40 is preferably 1 to 100 μm. By setting the thickness of the insulating layer 40 to 1 μm or more, it becomes easy to obtain the short circuit suppressing effect. Further, when the thickness is 100 μm or less, it is possible to prevent the lithium ion secondary battery from partially swelling due to the thickening of the end portion of the electrode. From these viewpoints, the thickness of the insulating layer 40 is more preferably 2 to 50 μm.
The thickness of the insulating layer 40 is an average value of the thickness of the insulating layer portion on the current collector 20 (see reference numeral d in FIG. 1) that is not in contact with the active material layer 30 of the insulating layer 40. Further, an electrode cross section is prepared by a CP (Cross-section Polisher) method, a microtome, or a FIB (Focused Ion Beam) method, and the thickness of the insulating layer 40 is measured using a scanning electron microscope (FE-SEM) or the like. ..

Battery safety if the stacking positions of the opposing electrodes deviate from the assumption during stacking and the burrs do not overlap the insulating layer 40, or if the burrs move due to an unexpected external force in the stacked state and the insulating layer 40 is pierced. Leads to a decline in. In order to prevent such a situation and ensure the safety of the battery, the length of the insulating layer 40 in the electrode 10 for the lithium ion secondary battery in the longitudinal direction (see reference numeral L in FIG. 1) is the height of the electrode active material layer 30. (See reference numeral h in FIG. 1A) is preferably twice or more, and more preferably five times or more. On the other hand, the upper limit of the length of the lithium ion secondary battery electrode 10 of the insulating layer 40 in the longitudinal direction is not particularly limited, but in order to secure the effective area of the electrodes and ensure the ionic conductivity between the electrodes. It is preferable that the length of the insulating layer 40 in the electrode 10 for a lithium ion secondary battery in the longitudinal direction is not too wide. As an example, the length of the insulating layer of the lithium ion secondary battery electrode 10 in the longitudinal direction is 3 mm or more and 10 mm or less. In FIG. 1, the x direction is the longitudinal direction of the lithium ion secondary battery electrode 10, the y direction is the width direction of the lithium ion secondary battery electrode 10, and the z direction is the lithium ion secondary battery electrode. 10 is the thickness direction. The x, y, and z directions are perpendicular to each other.

The electrode 10 for a lithium ion secondary battery provided with the insulating layer 40 may be a positive electrode or a negative electrode, but is preferably a positive electrode. Since the electrode area of the negative electrode is usually larger than the electrode area of the positive electrode, a short circuit is likely to occur when the burr of the negative electrode comes into contact with the current collector of the positive electrode. Therefore, by providing the insulating layer 40 on the positive electrode, a short circuit can be effectively prevented.

(Current collector)
Examples of the material constituting the current collector 20 include conductive metals such as copper, aluminum, titanium, nickel, and stainless steel. Among these, when the current collector 20 is a positive current collector, aluminum, titanium, nickel and stainless steel are preferable, stainless steel and aluminum are more preferable, and aluminum is further preferable. When the current collector is made of stainless steel or aluminum, particularly aluminum, for example, when a polyimide resin is used for the insulating layer, the adhesion strength can be easily improved. When the current collector 20 is a negative electrode current collector, copper, titanium, nickel and stainless steel are preferable, and copper is more preferable.
As described above, the electrode 10 for the lithium ion secondary battery is preferably a positive electrode, and the current collector 20 is also preferably a positive electrode current collector. Therefore, the current collector 20 is preferably formed of a material selected from aluminum, titanium, nickel and stainless steel, more preferably formed of a material selected from stainless steel and aluminum, and is formed of aluminum. Is even more preferable.
The current collector 20 is generally made of a metal foil, and its thickness is not particularly limited, but is preferably 1 to 50 μm, more preferably 5 to 20 μm. When the thickness of the current collector 20 is 1 to 50 μm, the current collector 20 can be easily handled and a decrease in energy density can be suppressed.

(Electrode active material layer)
The electrode active material layer 30 typically contains an electrode active material and an electrode binder. When the electrode is a positive electrode, the electrode active material layer becomes a positive electrode active material layer, and the electrode active material becomes a positive electrode active material. On the other hand, when the electrode is a negative electrode, the electrode active material layer becomes a negative electrode active material layer, and the electrode active material becomes a negative electrode active material.
In a lithium ion secondary battery, a larger amount of negative electrode active material of a negative electrode that accepts lithium is usually mounted than that of a positive electrode active material of a positive electrode that holds lithium. That is, a negative electrode is used in which the amount of the negative electrode active material is larger than the amount of the positive electrode active material of the positive electrode. This is to prevent the negative electrode from accepting lithium ions during charging and depositing lithium metal on the negative electrode. Therefore, it is preferable that the positive electrode and the negative electrode facing each other are configured so that the amount of the negative electrode active material is larger than the amount of the positive electrode active material. For the same reason, it is preferable to design the negative electrode to have a larger area of the positive electrode and the negative electrode facing each other than the positive electrode. This is to maintain a state in which the amount of the negative electrode active material is always large even when the position is displaced. Then, by forming an insulating layer at the boundary between the region of the positive electrode active material layer having a smaller area than the negative electrode active material layer and the region where the positive electrode active material layer is not formed, the current is collected by the electrodes facing the burrs. It is possible to more reliably prevent an internal short circuit that occurs when it comes into contact with the body. Therefore, the electrode on which the insulating layer 40 is provided is preferably a positive electrode as described above, the active material layer 30 is preferably a positive electrode active material layer, and the electrode active material is preferably a positive electrode active material.

The thickness of the electrode active material layer 30 is not particularly limited, but is preferably 10 to 100 μm, more preferably 20 to 80 μm per one side of the current collector. The thickness of the electrode active material layer 30 is measured by a known method such as observing the cross-sectioned measurement sample with SEM.

<Positive electrode active material>
Examples of the positive electrode active material used for the positive electrode active material layer include a lithium metallic acid compound. Examples of the lithium metal acid compound include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and the like. Further, as the positive electrode active material, olivine-type lithium iron phosphate (LiFePO ₄ ) or the like may be used. Further, as the positive electrode active material, a material using a plurality of metals other than lithium may be used, and NCM (nickel cobalt manganese) oxide, NCA (nickel cobalt aluminum) oxide, etc., which are called ternary oxides, may be used. You may use it. As the positive electrode active material, these substances may be used alone or in combination of two or more.

<Negative electrode active material>
Examples of the negative electrode active material used for the negative electrode active material layer include carbon materials such as graphite and hard carbon, composites of tin compounds, silicon and carbon, lithium and the like. Among these, carbon materials are preferable, and graphite is preferable. More preferred. As the negative electrode active material, the above substances may be used alone or in combination of two or more.

The average particle size of the electrode active material is not particularly limited, but is preferably 0.5 to 50 μm, more preferably 1 to 30 μm, and even more preferably 5 to 25 μm. The average particle size means the particle size (D50) when the volume integration is 50% in the particle size distribution of the electrode active material obtained by the laser diffraction / scattering method.

The content of the electrode active material in the electrode active material layer 30 is preferably 60 to 99% by mass, more preferably 80 to 99% by mass, still more preferably 90 to 98% by mass, based on the total amount of the electrode active material layer.

<Binder for electrodes>
Specific examples of the binder for the electrode include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), fluororesin such as polytetrafluoroethylene (PTFE), and polymethyl acrylate (PMA). , Polymethylmethacrylate (PMMA) and other acrylic resins, polyvinylidene acetate, polyimide (PI), polyamideimide, polyetherimide and other polyimide resins, polyamide (PA), polyvinylidene chloride (PVC), polyethernitrile (PEN) ), Polyethylene (PE), Polypropylene (PP), Polyacrylonitrile (PAN), Acrylonitrile-butadiene rubber, styrene butadiene rubber (SBR), poly (meth) acrylic acid, carboxymethyl cellulose (CMC), hydroxyethyl cellulose, polyvinyl alcohol, etc. Can be mentioned. These binders may be used alone or in combination of two or more. Further, carboxymethyl cellulose and the like may be used in the form of a salt such as a sodium salt.

The content of the binder for the electrode in the electrode active material layer 30 is preferably 0.5 to 20% by mass, more preferably 1.0 to 10% by mass, based on the total amount of the electrode active material layer.

At least one kind of electrode binder contained in the electrode active material layer 30 is at least one of the resins contained in the insulating layer 40 provided adjacent to the end portion of the electrode active material layer 30 and covering the end portion. It is preferably the same substance as the seed. As a result, the adhesion strength between the insulating layer 40 and the electrode active material layer 30 can be increased, and the reliability of the insulating layer 40 can be increased. For example, when the insulating layer 40 contains polyamide-imide, it is preferable that the electrode active material layer 30 also contains polyamide-imide. Further, when the insulating layer 40 contains the polyetherimide, it is preferable that the electrode active material layer 30 also contains the polyetherimide.

<Conductive aid>
The electrode active material layer 30 may further contain a conductive auxiliary agent, and the positive electrode active material layer preferably contains a conductive auxiliary agent. As the conductive auxiliary agent, a material having higher conductivity than the above-mentioned electrode active material is used, and specific examples thereof include carbon materials such as Ketjen black, acetylene black (AB), carbon nanotubes, and rod-shaped carbon. The conductive auxiliary agent may be used alone or in combination of two or more. When the conductive auxiliary material is contained in the electrode active material layer 30, the content of the conductive auxiliary agent is preferably 0.5 to 15% by mass based on the total amount of the electrode active material layer, and is preferably 1 to 10% by mass. Is more preferable. When the content of the conductive auxiliary agent is 0.5 to 15% by mass, it is possible to suppress an increase in electrical resistance and a decrease in output performance, and the conductive auxiliary agent absorbs the binder to cause powder falling. Can be suppressed.

The electrode active material layer 30 may contain an optional component other than the electrode active material, the conductive auxiliary agent, and the binder for the electrode as long as the effect of the present invention is not impaired. However, the total content of the electrode active material, the conductive auxiliary agent, and the binder for the electrode is preferably 90% by mass or more, and more preferably 95% by mass or more, based on the total mass of the electrode active material layer. ..

[Manufacturing method of electrodes for lithium-ion secondary batteries]
The electrode for a lithium ion secondary battery according to an embodiment of the present invention can be manufactured, for example, by the following manufacturing method. First, the composition for the electrode active material layer is applied onto the current collector to form the electrode active material layer on the current collector (electrode active material layer forming step). After that, the coated raw material for the insulating layer is applied so as to be adjacent to the end portion of the electrode active material layer and to cover the end portion to form the insulating layer (insulation layer forming step). Hereinafter, each step will be described in more detail.

(Electrode active material layer forming process)
In the electrode active material layer forming step, first, a composition for an electrode active material layer containing an electrode active material, an electrode binder, and a solvent is prepared. Examples of the solvent used in the composition for the electrode active material layer include cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, isopropyl alcohol, N-methylpyrrolidone (NMP), ethanol, water and the like. The composition for the electrode active material layer may contain other components such as a conductive additive to be blended if necessary. Details of the electrode active material, the binder for the electrode, and the like are as described above. The composition for the electrode active material layer is usually in the state of a slurry.

The electrode active material layer can be formed, for example, by applying the composition for an electrode active material layer on a current collector and drying it by a known coating method. Examples of the method of applying the composition for the electrode active material layer on the current collector sheet include a die coating method, a slit coating method, a comma coating method, a lip coating method, a dip coating method, a spray coating method, and a roll coating method. Examples include the method, the doctor blade method, the bar coating method, the gravure coating method, and the screen printing method.
The drying temperature at the time of drying the composition for the electrode active material layer applied on the current collector is not particularly limited as long as the solvent can be removed, but is, for example, 40 to 120 ° C., preferably 50 to 90 ° C. .. The drying time is not particularly limited, but is, for example, 30 seconds to 10 minutes.

(Insulation layer forming process)
Next, a raw material for an insulating layer for forming an insulating layer is applied. The raw material for the insulating layer contains a resin component for forming the insulating layer. The raw material for the insulating layer may be liquid or fluid when applied to the current collector, and may be composed of a single resin component, but is preferably used for diluting the resin component in addition to the resin component. Contains solvent. Further, the resin component may be a resin precursor that becomes a resin constituting the insulating layer by applying the raw material for the insulating layer to the current collector and curing after the application. Curing may be performed, for example, by heating during drying after application.
Specific examples of the solvent in the raw material for the insulating layer include one or more selected from N-methylpyrrolidone, N-ethylpyrrolidone, dimethylacetamide, and dimethylformamide. In addition, the raw material for the insulating layer may contain other additive components to be blended as needed. Details of the resin component and the additive component are as described above.
The solid content concentration of the raw material for the insulating layer is not particularly limited, but is, for example, about 5 to 50% by mass, preferably about 10 to 30% by mass.

The insulating layer may be formed by a known method using a raw material for an insulating layer. For example, the raw material for an insulating layer may be applied to the vicinity of the end of the electrode active material layer of the current collector and appropriately dried. Can be formed by. The method of applying the raw material for the insulating layer on the current collector is, for example, the die coating method, the slit coating method, the comma coating method, the lip coating method, the dip coating method, the spray coating method, the roll coating method, the doctor blade method, and the bar. Examples include a coating method, a gravure coating method, and a screen printing method. Among these coating methods, the die coating method is preferable from the viewpoint that the raw material for the insulating layer can be accurately applied to the vicinity of the end portion of the electrode active material layer.
The drying temperature at the time of drying the current collector coated with the raw material for the insulating layer is, for example, 40 to 150 ° C., preferably 60 to 130 ° C. The drying time is not particularly limited, but is, for example, 30 seconds to 10 minutes. The solvent of the applied raw material for the insulating layer may be removed by drying.

Hereinafter, the method of applying the raw material for the insulating layer will be described in detail with reference to FIGS. 2 and 3 by taking the die coating method as an example.
FIG. 2 is a diagram showing an example of a die head used for coating a raw material for an insulating layer. As shown in FIG. 2, the die head 60 is provided with two discharge ports 61 and 62. The positions of the two discharge ports 61 and 62 correspond to the positions near the ends of the electrode active material layer 130, respectively.
As shown in FIG. 3, the current collector 120 on which the electrode active material layer 130 is formed moves in the direction of the arrow 121, and the moving current collector 120 is insulated from the die head 60. Apply the layering material. The raw material for the insulating layer is applied near the end of the electrode active material layer 130.
The current collector 120 coated with the raw material for the insulating layer is passed through a dryer (not shown) as needed, whereby the raw material for the insulating layer coated on the current collector 120 is dried. And the insulating layer 140 is formed.
In this method, the raw material for the insulating layer is applied near the end of the electrode active material layer 130 so that the insulating layer 140 is adjacent to the end 131 of the electrode active material layer 130 and covers the end 131. Is formed in.
After forming the insulating layer 140, the insulating layer 140 may be formed on the surface opposite to the current collector 120 in the same manner.

(Pressure press process)
The current collector 120 on which the electrode active material layer 130 and the insulating layer 140 are formed is preferably pressure-pressed. The pressure press may be performed by a roll press or the like. The pressure of the pressure press is not particularly limited as long as the desired electrode density can be achieved and wrinkles or the like do not occur in the current collector 120. In the case of a roll press, for example, the pressure of the pressure press is a linear pressure, preferably 100 to 2000 kN / m, and more preferably 200 to 1000 kN / m.

(Division process)
As shown in FIG. 4, for example, the current collector 120 in which the electrode active material layer 130 and the insulating layer 140 are formed is cut along the dotted line 150 and divided into a plurality of electrodes for a lithium ion secondary battery. As a result, the electrode 10 for a lithium ion secondary battery according to the embodiment of the present invention shown in FIG. 1 can be manufactured.

The electrode 10 for a lithium ion secondary battery according to the above embodiment of the present invention can be deformed as follows.
(Modification example 1)
The electrode 10 for a lithium ion secondary battery according to the above embodiment of the present invention has an electrode active material layer 30 and an insulating layer 40 formed on both surfaces of the current collector 20. However, as in the lithium ion secondary battery electrode 10A shown in FIG. 5, the electrode active material layer 30 and the insulating layer 40 may be formed only on one surface of the current collector 20.

(Modification 2)
In the above example of the method for manufacturing an electrode for a lithium ion secondary battery according to an embodiment of the present invention, when the electrode for a lithium ion secondary battery according to the embodiment of the present invention is manufactured, the composition for an electrode active material layer and insulation are used. The layering material was applied separately. However, the composition for the electrode active material layer and the raw material for the insulating layer may be applied at the same time.

(Modification example 3)
In the electrode for a lithium ion secondary battery according to the embodiment of the present invention, the insulating layer 40 is formed so as to cover the end portion 31 of the electrode active material layer 30 but not the entire surface. However, as in the lithium ion secondary battery electrode 10B shown in FIG. 6, the insulating layer 40B may be formed so as to cover not only the end portion 31 of the electrode active material layer 30 but also the entire surface. Further, also in this case, as in the above-mentioned modification 1, the electrode active material layer and the insulating layer may be formed only on one surface of the current collector.

The electrode for a lithium ion secondary battery and a modification thereof in one embodiment of the present invention are only one embodiment of the electrode for a lithium ion secondary battery of the present invention. Therefore, the electrode for a lithium ion secondary battery and a modification thereof in one embodiment of the present invention do not limit the electrode for a lithium ion secondary battery of the present invention.

[Lithium secondary ion battery]
The lithium secondary ion battery of the present invention includes the above-mentioned electrode for the lithium ion secondary battery. Further, it is preferable that the lithium secondary ion battery includes a negative electrode and a positive electrode, and at least the positive electrode is an electrode for a lithium ion secondary battery. Hereinafter, the lithium ion secondary battery according to the embodiment of the present invention will be described with reference to FIG. 7.
FIG. 7 is a schematic cross-sectional view of the lithium ion secondary battery according to the embodiment of the present invention. As shown in FIG. 7, the lithium ion secondary battery 1 according to the embodiment of the present invention includes the lithium ion secondary battery electrode 10 according to the embodiment of the present invention as a positive electrode and a negative electrode.

In the lithium ion secondary battery 1 according to the embodiment of the present invention, the electrode 10 for the lithium ion secondary battery as the positive electrode 10X and the electrode 10 for the lithium ion secondary battery as the negative electrode 10Y are each provided with a plurality of layers. Are arranged alternately in. Then, the ends of the current collectors 20 of each of the electrodes 10 for the lithium ion secondary battery 10 as the positive electrode 10X constituting each layer are collectively connected to the positive electrode terminal 2, and the lithium ion 2 as the negative electrode 10Y constituting each layer. The ends of the current collectors 20 of each of the electrodes 10 for the next battery are grouped together and connected to the negative electrode terminal 3. Further, the insulating layer 40 is arranged so as to be adjacent to the end portion of the electrode active material layer 30 on the bundled end portion side of the current collector 120. As a result, even if the lithium ion secondary battery electrode 10 has burrs, a short circuit between the positive electrode and the negative electrode can be more reliably prevented. In the lithium ion secondary battery, members constituting the lithium ion secondary battery such as the positive electrode 10X and the negative electrode 10Y are housed in the housings 6 and 7. The housings 6 and 7 may be square, cylindrical, laminated or the like.

The lithium ion secondary battery 1 in one embodiment of the present invention preferably further includes a separator 8 arranged between the positive electrode 10X and the negative electrode 10Y. By providing the separator 8, a short circuit between the positive electrode 10X and the negative electrode 10Y is more effectively prevented. Further, the separator 8 may hold the electrolyte 9 described later. The insulating layer 40 provided on the positive electrode 10X or the negative electrode 10Y may or may not be in contact with the separator, but is preferably in contact with the separator.

Examples of the separator 8 include a porous polymer film, a non-woven fabric, and glass fiber, and among these, a porous polymer film is preferable. Examples of the porous polymer film include an olefin-based porous film. The separator 8 may be heated by heat generated when the lithium ion secondary battery is driven and may undergo heat shrinkage or the like. Even during such heat shrinkage, the provision of the insulating layer makes it easier to suppress a short circuit.

The lithium ion secondary battery of the present invention comprises an electrolyte 9. The electrolyte is not particularly limited, and a known electrolyte 9 used in the lithium ion secondary battery 1 may be used. As the electrolyte 9, for example, an electrolytic solution is used. The electrolyte 9 is filled in the housings 6 and 7, for example, after the laminated electrodes 10 are housed in the housings 6 and 7.

Examples of the electrolytic solution include an organic solvent and an electrolytic solution containing an electrolyte salt. Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-. Polar solvents such as dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and methylacetamide, or mixtures of two or more of these solvents can be mentioned.
Electrolyte salts include LiClO ₄ , LiPF ₆ , LiBF ₄ , _{LiAsF 6} , LiSbF ₆ , LiCF ₃ CO ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ). _{Examples include lithium-containing salts such as 2} and LiN (COCF ₂ CF ₃ ) ₂ , lithium bisoxalate boronate (LiB (C ₂ O ₄ ) ₂ ), and lithium organic acid salt-boron trifluoride complex, LiBH. _{Complexes such as 4 and the} like Complexes such as hydrides can be mentioned. These salts or complexes may be used alone or in admixture of two or more.
Further, the electrolyte 9 may be a gel-like electrolyte in which the above-mentioned electrolytic solution further contains a polymer compound. Examples of the polymer compound include a fluoropolymer such as polyvinylidene fluoride and a polyacrylic polymer such as methyl poly (meth) acrylate. The gel electrolyte may be used as a separator.

The lithium ion secondary battery according to the above embodiment of the present invention can be modified as follows.
(Modification example 1)
The lithium ion secondary battery according to the above embodiment of the present invention is provided with an active material layer and an insulating layer on both sides of a current collector as a positive electrode and a negative electrode. The electrode 10 for a lithium ion secondary battery according to the embodiment of the present invention. However, the lithium ion secondary battery electrode 10A of the first modification of the present invention may be provided as the positive electrode and the negative electrode. That is, at least a part of the positive electrode and the negative electrode may be the electrode 10A for a lithium ion secondary battery having an active material layer and an insulating layer on only one side of the current collector. Further, as the positive electrode and the negative electrode, the electrode 10B for the lithium ion secondary battery of the modification 3 of the present invention may be provided.

(Modification 2)
The lithium ion secondary battery according to the embodiment of the present invention includes the electrode 10 for the lithium ion secondary battery according to the embodiment of the present invention as the positive electrode and the negative electrode, but the present invention is used as one of the positive electrode and the negative electrode. The electrode 10 for the lithium ion secondary battery according to the embodiment of the present invention may be provided. Further, as either the positive electrode or the negative electrode, the electrode 10A for the lithium ion secondary battery of one embodiment of the modified example 10A of the present invention or the lithium ion secondary battery of the modified example 10B of the present invention is used. The electrode 10B may be provided.
As described above, since the electrode area of the positive electrode is usually smaller than that of the negative electrode, the insulating layer 40 can be more reliably prevented from internal short circuit by providing the insulating layer 40 on the positive electrode than on the negative electrode. Therefore, in the lithium ion secondary battery according to the embodiment of the present invention, it is preferable that at least the positive electrode is the electrode 10 (or 10A or 10B) for the lithium ion secondary battery of the present invention described above.
For example, as in the lithium ion secondary battery 1A shown in FIG. 8, the electrode 10 for the lithium ion secondary battery according to the embodiment of the present invention is used only for the positive electrode 10X, and the negative electrode 10Y is not formed with an insulating layer. Electrode 10C may be used. In this case, even if there are burrs on the positive electrode, the negative electrode active material layer suppresses the burrs on the positive electrode from coming into direct contact with the current collector on the negative electrode, so that a short circuit is unlikely to occur.

The lithium ion secondary battery and its modifications according to the embodiment of the present invention are only one embodiment of the lithium ion secondary battery of the present invention. Therefore, the lithium ion secondary battery and its modifications in one embodiment of the present invention do not limit the lithium ion secondary battery of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The physical properties of the obtained electrode for a lithium ion secondary battery were measured and the performance was evaluated by the following method.
(Tensile modulus and elongation at break)
The current collector was removed from the positive electrode having an insulating layer by chemical etching to obtain an insulating layer for measurement. With respect to this insulating layer, the elastic modulus immediately after the start of tension was defined as the tensile elastic modulus, and the elongation at break was measured as the fracture elongation by a method according to JIS K 7161. A hydrogen peroxide solution / dilute sulfuric acid solution was used for chemical etching.

(Thickness of insulation layer)
The cross section of the insulating layer formed on the aluminum foil was exposed by the ion milling method. Next, the cross section of the exposed insulating layer was observed using an FE-SEM (field emission scanning electron microscope) at a magnification at which the entire insulating layer could be observed, and an image of the insulating layer was obtained. The thickness of the insulating layer was measured from the obtained SEM image, and the average value was taken as the thickness of the insulating layer.

(Adhesion strength of the insulating layer to the positive electrode current collector)
A strip-shaped sample having a width of 5 mm was cut out from the portion of the current collector on which the insulating layer was formed. A strong adhesive tape was attached to the insulating layer of the strip-shaped sample using a roller. Then, a strip-shaped sample to which the strong adhesive tape was attached was subjected to a peeling test in the 180 ° direction at a peeling test speed of 10 mm / sec at room temperature (25 ° C.) using an autograph. In the peeling test, the strong adhesive tape was peeled from the current collector between the insulating layer and the current collector.

(Presence / absence of polyimide resin)
The insulating layer contains a polyimide resin by measuring the infrared absorption spectrum on the surface of the insulating layer by the ATR reflection method using a Fourier transform infrared spectrophotometer (“FT / IR620” manufactured by Nippon Spectroscopy Co., Ltd.). It was determined whether or not. As a specific discrimination method, ^{the absorption bands of 1720 cm -1} (C = 0 expansion / contraction vibration), 1380 cm ^-1 (CN expansion / contraction), and 1300 to 1100 cm ^-1 (absorption band belonging to the CO bond) are all satisfied. The one was a polyimide resin.

(Short circuit test)
A short circuit test was performed using the test apparatus shown in FIG. The test device includes a pressing jig 81 and a receiving plate 82. As shown in FIG. 9, a positive electrode 75, a nickel piece 73, a separator 72, and a negative electrode 71 having negative electrode active material layers formed on both sides thereof were arranged in this order on the receiving plate 82. The positive electrode 75 and the negative electrode 71 were produced in each Example and Comparative Example. Therefore, the positive electrode 75 had an insulating layer 74 formed on one surface (upper surface) of the positive electrode current collector. A polyethylene porous film was used as the separator 72. As the nickel small piece 73, the nickel small piece used in the test of forced internal short circuit of JIS C 8714: 2007 was used. The pressing jig 81 is a jig that applies pressure in a direction in which the negative electrode 71 and the positive electrode 75 approach each other.
When the pressing jig 81 is lowered to increase the pressure for pressing the negative electrode 71 against the positive electrode 75, the nickel small pieces 73 penetrate the separator 72 and the insulating layer 74 to cause conduction (short circuit). In the short-circuit test, a voltage of 2 V is applied between the negative electrode 71 and the positive electrode 75, and the resistance value between the positive electrode 75 and the negative electrode 71 is measured while lowering the pressing jig 81, and the resistance value becomes 10 Ω or less. At that time, it was judged that the conductor was conducting. Twenty or more samples were evaluated as follows based on the probability that they did not conduct when pressurized with 30 N.
A: 95% or more B: 80% or more and less than 95% C: less than 80%

[Example 1]
(Preparation of negative electrode)
100 parts by mass of graphite (average particle diameter 10 μm) as the negative electrode active material, 1.5 parts by mass of sodium salt of carboxymethyl cellulose (CMC) and 1.5 parts by mass of styrene butadiene rubber (SBR) as the binder for the negative electrode, and as a solvent. It was mixed with water to obtain a slurry for a negative electrode active material layer adjusted to have a solid content of 50% by mass. This slurry for the negative electrode active material layer was applied to both sides of a copper foil having a thickness of 12 μm as a negative electrode current collector and vacuum dried at 100 ° C. After that, the negative electrode current collector coated with the slurry for the negative electrode active material layer on both sides is pressure-pressed by a roller at a linear pressure of 300 kN / m, and further punched into an electrode size of 110 mm × 210 mm square, and the negative electrode active material is punched on both sides. A negative electrode having a layer was used. Of the dimensions, the area to which the negative electrode active material was applied was 110 mm × 190 mm. The thickness of the negative electrode active material layer formed on both sides was 50 μm per side. Moreover, no insulating layer was formed on the negative electrode.

(Formation of insulating layer)
NMP solution of polyamide-imide (trade name "Vilomax HR-11NN", manufactured by Toyobo Co., Ltd., solid content concentration 15% by mass, number average) as a raw material for an insulating layer on an aluminum foil with a thickness of 15 μm as a positive electrode current collector. Molecular weight: 15000) was applied. Then, the coating film was dried at 120 ° C. for 10 minutes to form an insulating layer on the aluminum foil. Then, the aluminum foil on which the insulating layer was formed was pressure-pressed by a roller at a linear pressure of 400 kN / m, and further punched into an electrode size of 100 mm × 200 mm square to obtain a positive electrode having an insulating layer. The thickness of the insulating layer was 5 μm. Using the positive electrode having this insulating layer, the adhesion strength was measured and a short circuit test was performed to evaluate the performance of the insulating layer. Further, the insulating layer was peeled off, the tensile elastic modulus and the elongation at break of the peeled insulating layer were measured, and the presence or absence of the polyimide resin was also determined.

[Example 2]
Example 1 and Example 1 except that an NMP solution of polyamide-imide (trade name "Vilomax HR-16NN", manufactured by Toyobo Co., Ltd., solid content concentration 14% by mass, number average molecular weight: 30,000) was used as a raw material for an insulating layer. It was carried out in the same manner.

[Example 3]
As a raw material for the insulating layer, pellets of polyetherimide (trade name "ULTEM", manufactured by SABIC) were dissolved in NMP to obtain a varnish having a solid content concentration of 15% by mass. After that, it was carried out in the same manner as in Example 1.

[Example 4]
NMP solution of polyamide-imide (trade name "Vilomax HR-16NN", manufactured by Toyo Boseki Co., Ltd., solid content concentration 14% by mass, number average molecular weight: 30,000) and polyvinylidene fluoride (PVdF) NMP as raw materials for the insulating layer. The ratio of polyamide-imide and PVdF to the solution (trade name "Kureha KF Polymer L # 1120", manufactured by Kureha Battery Materials Japan Co., Ltd., solid content concentration 12% by mass) is 50:50 (mass). The same procedure as in Example 1 was carried out except that the mixture obtained by mixing was used so as to have a ratio of).

[Example 5]
NMP solution of polyamide-imide (trade name "Vilomax HR-11NN", manufactured by Toyo Boseki Co., Ltd., solid content concentration 15% by mass, number average molecular weight: 15000) and polyvinylidene fluoride (PVdF) NMP as raw materials for the insulating layer. The ratio of polyamide-imide and PVdF to the solution (trade name "Kureha KF Polymer L # 1120", manufactured by Kureha Battery Materials Japan Co., Ltd., solid content concentration 12% by mass) is 50:50 (mass). The same procedure as in Example 1 was carried out except that the mixture obtained by mixing was used so as to have a ratio of).

[Example 6]
NMP solution of polyamide-imide (trade name "Vilomax HR-16NN", manufactured by Toyo Boseki Co., Ltd., solid content concentration 14% by mass, number average molecular weight: 30,000) and polyvinylidene fluoride (PVdF) NMP as raw materials for the insulating layer. The ratio of polyamide-imide and PVdF to the solution (trade name "Kureha KF Polymer L # 1120", manufactured by Kureha Battery Materials Japan Co., Ltd., solid content concentration 12% by mass) is 65:35 (mass). The same procedure as in Example 1 was carried out except that the mixture obtained by mixing was used so as to have a ratio of).

[Example 7]
NMP solution of polyamide-imide (trade name "Vilomax HR-11NN", manufactured by Toyo Boseki Co., Ltd., solid content concentration 15% by mass, number average molecular weight: 15000) and polyvinylidene fluoride (PVdF) NMP as raw materials for the insulating layer. The ratio of polyamide-imide and PVdF to the solution (trade name "Kureha KF Polymer L # 1120", manufactured by Kureha Battery Materials Japan Co., Ltd., solid content concentration 12% by mass) is 65:35 (mass). The same procedure as in Example 1 was carried out except that the mixture obtained by mixing was used so as to have a ratio of).

[Comparative Example 1]
Same as Example 1 except that an NMP solution of a polyimide resin (polyamideimide) (trade name "Vilomax HR-17NN", manufactured by Toyobo Co., Ltd., solid content concentration 35% by mass) was used as a raw material for an insulating layer. It was carried out in.

[Comparative Example 2]
A polyamic acid solution (trade name "Yupia U-Varnish S", manufactured by Ube Industries, Ltd.), which is a precursor of polyimide, is used as a raw material for the insulating layer, dried at 120 ° C. for 10 minutes, and then vacuumed at 300 ° C. for 30 minutes. It was carried out in the same manner as in Example 1 except that the hardening treatment was carried out in.

[Comparative Example 3]
Except for using an NMP solution of polyvinylidene fluoride (PVdF) (trade name "Kureha KF Polymer L # 1120", manufactured by Kureha Battery Materials Japan Co., Ltd., solid content concentration 12% by mass) as a raw material for an insulating layer. Was carried out in the same manner as in Example 1.

※表１の樹脂１、２欄に示した質量％は、絶縁層全量基準の各樹脂の含有量を示す。The measurement results and evaluation results are shown in Table 1 below.

* The mass% shown in columns 1 and 2 of the resin in Table 1 indicates the content of each resin based on the total amount of the insulating layer.

As shown in Examples and Comparative Examples, short-circuiting could be reliably prevented by adjusting the tensile elastic modulus and the elongation at break of the insulating layer within a predetermined range.

1,1A lithium ion secondary battery 2 positive electrode terminal 3 negative electrode terminal 6,7 housing 8 separator 9 electrolyte 10, 10A, 10B, 10C electrode for lithium ion secondary battery 10X positive electrode 10Y negative electrode 20,120 current collector 30,130 Electrode active material layer 31,131 Ends 40,40B, 140 Insulation layer 50,60 Die head 51,61,62 Discharge port 71 Negative electrode 72 Separator 73 Nickel small piece 74 Insulation layer 75 Positive electrode 81 Pressing jig 82 Receiving plate

Claims (11)

A current collector and an electrode active material layer and an insulating layer provided on the surface of the current collector are provided.
An electrode for a lithium ion secondary battery in which the insulating layer is provided so as to be adjacent to and cover the end of the electrode active material layer.
The insulating layer is lithium having a tensile elastic modulus of 2.0 to 7.0 GPa measured according to JIS K 7161 and a breaking elongation of 15% or more measured according to JIS K 7161. Electrode for ion secondary battery. The electrode for a lithium ion secondary battery according to claim 1, wherein the insulating layer contains a polyimide resin. The electrode for a lithium ion secondary battery according to claim 2, wherein the insulating layer further contains a fluororesin. The electrode for a lithium ion secondary battery according to claim 2 or 3, wherein the content of the polyimide resin in the insulating layer is 45% by mass or more and 100% by mass or less based on the total amount of the insulating layer. The lithium ion secondary battery according to any one of claims 1 to 4, wherein the insulating layer is an insulating coating layer coated on the surface of the current collector and the end portion of the electrode active material layer. electrode. The electrode for a lithium ion secondary battery according to any one of claims 1 to 5, wherein the current collector is formed of any one selected from aluminum and stainless steel. The electrode for a lithium ion secondary battery according to any one of claims 1 to 6, wherein the adhesion strength between the insulating layer and the current collector is 200 N / m or more. The electrode for a lithium ion secondary battery according to any one of claims 1 to 7, wherein the electrode active material layer is a positive electrode active material layer. A lithium ion secondary battery comprising the electrode for a lithium ion secondary battery according to any one of claims 1 to 8. It has a negative electrode and a positive electrode,
The lithium ion secondary battery according to claim 9, wherein the positive electrode is an electrode for the lithium ion secondary battery. The positive electrode and the negative electrode are alternately arranged so that a plurality of layers are provided, and the ends of the current collectors of the positive electrodes constituting each layer are collectively connected to the positive electrode terminal, and each of the negative electrodes constituting each layer is connected. A lithium-ion secondary battery in which the ends of the current collector are grouped together and connected to the negative electrode terminal.
At least one of the positive electrode and the negative electrode is composed of the electrode for a lithium ion secondary battery.
The lithium ion secondary battery according to claim 9 or 10, wherein the insulating layer is arranged so as to be adjacent to the end portion of the electrode active material layer on the bundled end side of the current collector.

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