WO2019188550A1

WO2019188550A1 - Composition for forming undercoat layer of energy storage device

Info

Publication number: WO2019188550A1
Application number: PCT/JP2019/011347
Authority: WO
Inventors: 辰也畑中; 康志境田
Original assignee: 日産化学株式会社
Priority date: 2018-03-29
Filing date: 2019-03-19
Publication date: 2019-10-03
Also published as: TW202005150A; JPWO2019188550A1

Abstract

Provided is a composition for forming an undercoat layer of an energy storage device, the composition comprising carbon nanotubes, a carbon nanotube dispersant, and a solvent, and the carbon nanotubes each having a constricted portion. This composition makes it possible to provide an undercoat layer that exhibits the effects of reducing resistance and suppressing an increase in resistance.

Description

Composition for forming undercoat layer of energy storage device

The present invention relates to a composition for forming an undercoat layer of an energy storage device.

In recent years, development of high-performance batteries has been actively promoted in response to demands for reducing the size and weight of mobile electronic devices such as smartphones, digital cameras, and portable game machines, and secondary batteries that can be used repeatedly by charging. Demand is growing significantly.
Among them, a lithium ion secondary battery is a secondary battery that has been developed most vigorously at present because it has a high energy density and a high voltage and has no memory effect during charging and discharging.
In addition, the development of electric vehicles has been actively promoted due to recent efforts to deal with environmental problems, and higher performance has been demanded for secondary batteries as a power source.

By the way, a lithium ion secondary battery contains a positive electrode and a negative electrode capable of occluding and releasing lithium, and a separator interposed therebetween in a container, and an electrolyte solution (liquid in the case of a lithium ion polymer secondary battery) therein. It has a structure filled with a gel-like or all solid electrolyte instead of the electrolyte.
For the positive and negative electrodes, an active material capable of occluding and releasing lithium, a conductive material mainly composed of a carbon material, and a composition containing a polymer binder are generally applied on a current collector such as a copper foil or an aluminum foil. It is manufactured by doing. This binder is used to bond an active material and a conductive material, and further to the metal foil, and is a fluorine-based resin soluble in N-methylpyrrolidone (NMP) such as polyvinylidene fluoride (PVdF) or an olefin-based heavy polymer. Combined aqueous dispersions are commercially available.

However, the adhesive strength of the binder to the current collector is not sufficient, and a part of the active material or conductive material is peeled off from the current collector during the manufacturing process such as the electrode cutting process or the winding process. , Causing a short circuit and variation in battery capacity.
In addition, the contact resistance between the electrode mixture layer and the current collector increases due to the volume change of the electrode mixture due to the swelling of the binder due to the electrolytic solution and the volume change due to the lithium occlusion and release of the active material after long-term use. Or a part of the active material or the conductive material is peeled off from the current collector or dropped off, and there is a problem that the battery capacity is deteriorated, and further, there is a problem in terms of safety.

As an attempt to solve the above problems, as a technique for increasing the adhesion between the current collector and the electrode mixture layer and reducing the resistance by reducing the contact resistance, the current collector and the electrode mixture layer A method of interposing a conductive undercoat layer between them has been developed.
For example, Patent Document 1 discloses a technique in which a conductive layer containing carbon as a conductive filler is used as an undercoat layer and disposed between a current collector and an electrode mixture layer, and the undercoat layer is provided. By using the composite current collector, it is possible to reduce the contact resistance between the current collector and the electrode mixture layer, and also to suppress the decrease in capacity at the time of high-speed discharge, and to further suppress the deterioration of the battery, Also, Patent Document 2 and Patent Document 3 disclose similar techniques.
Further, Patent Document 4 and Patent Document 5 disclose an undercoat layer using carbon nanotubes (hereinafter also abbreviated as CNT) as a conductive filler.

By the way, the undercoat is expected not only to lower the resistance of the battery but also to suppress the increase in resistance, but depending on the conductive carbon material used, the resistance of the battery is increased and the resistance increase is accelerated. There is a case to let you.
In this regard, it is not clear what conductive carbon material is used to reduce the resistance of the battery and suppress the increase in resistance.

Japanese Patent Laid-Open No. 9-097625 JP 2000-011991 JP-A-11-149916 International Publication No. 2014/042080 International Publication No. 2015/029949

This invention is made in view of such a situation, and provides the composition for undercoat layer formation of the energy storage device which can provide the undercoat layer which exhibits a low resistance effect and a resistance raise inhibitory effect. With the goal.

As a result of intensive studies to achieve the above object, the present inventors have reduced the resistance by using carbon nanotubes (CNT) having a specific structure and physical properties in the composition for forming an undercoat layer. The present invention was completed by finding that a composition capable of providing an undercoat layer exhibiting the effect and the resistance increase suppressing effect was obtained.

That is, the present invention
1. A composition for forming an undercoat layer of an energy storage device, comprising a carbon nanotube, a carbon nanotube dispersant, and a solvent, wherein the carbon nanotube has a constricted portion;
2. The composition for forming an undercoat layer of an energy storage device according to 1, wherein a geometric average diameter (M _D ) of the outer diameter (D) of the carbon nanotube is 5 to 30 nm,
3. The composition for forming an undercoat layer of one or two energy storage devices, wherein the carbon nanotube dispersant contains a vinyl polymer or triarylamine hyperbranched polymer containing an oxazoline group in a side chain;
4). An undercoat layer obtained from the composition for forming an undercoat layer of any one of 1-3 energy storage devices;
5. 4 undercoat layers having a basis weight of 1000 mg / m ² or less,
6). An undercoat layer of 5 having a basis weight of 500 mg / m ² or less,
7. 6 undercoat layers having a basis weight of 300 mg / m ² or less,
8). 7 undercoat layers having a basis weight of 200 mg / m ² or less,
9. A composite current collector for an electrode of an energy storage device, comprising an undercoat layer according to any one of 4 to 8,
10. An electrode for an energy storage device comprising a composite current collector for an electrode of 9 energy storage devices;
11. An energy storage device comprising 10 energy storage device electrodes,
12 Eleven energy storage devices that are lithium ion secondary batteries are provided.

The composition for forming an undercoat layer of the energy storage device of the present invention is suitable as a composition for forming an undercoat layer that joins the current collector and the active material constituting the electrode of the energy storage device, By forming an undercoat layer on the current collector using the composition, the resistance of the energy storage device can be reduced and an increase in resistance can be suppressed.

It is a schematic cross section which shows the parallel part and constriction part of the carbon nanotube used by this invention.

Hereinafter, the present invention will be described in more detail.
The composition for forming an undercoat layer of an energy storage device according to the present invention (hereinafter simply referred to as a composition) includes CNTs having a specific structure and physical property values, a CNT dispersant, and a solvent.

As the CNT, it is preferable to use a CNT that is easy to disperse in the dispersion liquid in order to exert an effect of lowering the battery resistance when the dispersion liquid is used as an undercoat layer. Such CNTs preferably have many crystal discontinuities that can be easily cut with small energy.
From such a viewpoint, the CNT used in the composition of the present invention preferably has a constricted portion. The CNT having a constricted portion is a CNT wall having a constricted portion having a tube outer diameter of 90% or less of the parallel portion and the tube outer diameter of the parallel portion.
Since this constricted part is a part created by changing the growth direction of CNTs, it has a discontinuous crystal part and becomes an easily breakable part that can be easily cut with a small mechanical energy.

FIG. 1 shows a schematic cross-sectional view of a CNT having a parallel portion 1 and a constricted portion 3.
As shown in FIG. 1, the parallel part 1 is a part where the wall can be recognized as two parallel straight lines or two parallel curves. In this parallel part 1, the distance between the outer walls of the parallel line in the normal direction is the tube outer diameter 2 of the parallel part 1.
On the other hand, the constricted portion 3 is a portion where both ends thereof are connected to the parallel portion 1 and the distance between the walls is closer than that of the parallel portion 1, more specifically, the tube outer diameter 2 of the parallel portion 1 is increased. On the other hand, it is a portion having a tube outer diameter 4 of 90% or less. The tube outer diameter 4 of the constricted portion 3 is the distance between the outer walls of the constricted portion 3 where the wall constituting the outer wall is closest. As shown in FIG. 1, many of the constricted portions 3 have portions where crystals are discontinuous.
The shape of the CNT wall and the outer diameter of the tube can be observed with a transmission electron microscope or the like. Specifically, it is possible to prepare a 0.5% dispersion of CNT, dry the dispersion on a sample stage, and confirm the constricted portion by an image taken at 50,000 times with a transmission electron microscope. it can.
For the CNT, a 0.1% dispersion of CNT was prepared, the dispersion was placed on a sample stage and dried, and an image taken at 20,000 times with a transmission electron microscope was divided into 100 nm square sections, and 100 nm When 300 sections with CNT occupying 10% to 80% in all four sections are selected, the total number of easily breakable portions depends on the ratio of the section with at least one constricted portion in one section to 300 sections. The ratio (the ratio of the presence of easily breakable parts) is determined. When the area occupied by CNTs in the compartment is less than 10%, measurement is difficult because the amount of CNTs is too small. In addition, when the area occupied by the CNTs in the section exceeds 80%, the CNTs occupy in the sections increase so that the CNTs overlap, making it difficult to distinguish between the parallel part and the constricted part, and accurate measurement is difficult. Become.
In the CNT used in the present invention, the existence ratio of easily breakable portions is 60% or more. When the proportion of easily breakable portions is less than 60%, CNT is difficult to disperse, and when excessive mechanical energy is applied to disperse, it leads to the destruction of the crystal structure of the graphite surface, which is a characteristic of CNT. Characteristics such as electrical conductivity are reduced. In order to obtain higher dispersibility, the presence ratio of easily breakable portions is preferably 70% or more.

The CNT used in the present invention is not particularly limited as long as it has a constricted portion, but the geometric average diameter (M _D ) of the outer diameter of the tube is preferably 5 to 30 nm.
When the average diameter of the tube outer diameter exceeds 30 nm, when used as a conductive material, the number of fibers per unit mass decreases, and there is a possibility that sufficient conductivity cannot be obtained. In addition, when the average diameter of the tube outer diameter is less than 5 nm, it is difficult to sufficiently disperse the carbon nanotubes, and as a result, the characteristics may be deteriorated. From the balance of dispersibility and characteristics, the geometrical average diameter of the tube outer diameter is more preferably 10 to 25 nm, and even more preferably 19 to 22 nm.

In addition, the conductivity of the CNT is preferably 50 S / cm or less, more preferably 45 S / cm or less, and even more preferably 35 S / cm or less, from the viewpoint of reducing the resistance of the device and exhibiting a resistance increase suppressing effect. is there. Although a minimum in particular is not restrict | limited, From a viewpoint of making the electroconductivity of an undercoat layer high, Preferably it is 5 S / cm or more, More preferably, it is 10 S / cm or more.
Furthermore, the density of the CNT is preferably 1.15 g / cm ³ or more, more preferably 1.3 g / cm ³ or more, from the viewpoint of reducing the resistance of the device and exhibiting the resistance increase suppressing effect. The upper limit is not particularly limited, but is preferably 2.0 g / cm ³ or less, more preferably 1.6 g / cm ³ or less.
The density (g / cm ³ ) of the CNT means a bulk density measured when a pressure of 20 kN / cm ² is applied to the powder (when 20 kN / cm ^{2 is} applied).
The conductivity and density of the CNT can be measured by a known powder resistance measurement system (for example, MCP-PD51 type and resistivity meter Loresta GP manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

Further, the G / D band ratio is preferably 0.680 to 2.900, and is preferably 0.690 or more and 0.710 or more in consideration of enhancing the effect of reducing the resistance and increasing the resistance of the obtained device. Is more preferable, 0.800 or more is still more preferable, and 0.900 or more is further preferable. The upper limit of the G / D band ratio is 2.900 or less, preferably 2.500 or less, more preferably 2.000 or less, and even more preferably 1.500 or less.
Note that the G / D band ratio of CNT is a parameter serving as an index of the crystallinity and the amount of defects of the CNT used, and can be obtained by Raman spectroscopic measurement.
More specifically, the G ⁺ band which is the Raman shift having the greatest intensity between 1590 and 1605 cm ⁻¹ from the Raman spectroscopic measurement, the G ⁻ band which is the Raman shift having the greatest intensity between 1580 and 1565 cm ⁻¹ , and 1330 Each peak intensity of the D band, which is a Raman shift with the largest peak intensity between ˜1310 cm ⁻¹ , is obtained and expressed by the ratio (G ⁺ + G ⁻ ) / D. The baseline for calculating each peak intensity is 1700 to 1150 cm ⁻¹ .

In the present invention, the standard deviation of the carbon content of the CNT is not particularly limited, but if the standard deviation is 1.00 or more, the effect of reducing the resistance of the obtained device is increased, and the resistance The rise can be efficiently suppressed. In consideration of further enhancing these effects, the standard deviation is preferably 1.50 or more, and more preferably 2.00 or more.
Further, in consideration of further increasing the resistance reduction effect and the resistance increase suppressing effect, it is preferable to use CNT having an average value of carbon content (n = 3) determined by elemental analysis of 94% by mass or more, It is more preferable to use CNTs having the same average value of 95% by mass or more, and it is even more preferable to use CNTs having the same average value of 96% by mass or more.
In addition, the standard deviation of the carbon content is the carbon content obtained from the measurement result of 3 times (n = 3) when quantitative analysis of 1 mg of CNT (error: within ± 10 mass%) by elemental analysis. Standard deviation.

In the present invention, the CNT includes the temperature at the inflection point of the first exothermic peak in differential thermal analysis (T _DTA ) and the crystallite size (L _C (002)) of the carbon nanotube (002) plane in X-ray diffraction. The product of the ratio T _DTA / L _C (002) of the tube and the geometric standard deviation (σ _D ) of the tube outer diameter distribution ((T _DTA / L _C (002)) × σ _D ) is preferably 22 or less. .
Further, the water vapor adsorption amount of the CNT is preferably 0.6 to 4.5 mg / g. When the water vapor adsorption amount is less than 0.6 mg / g, the familiarity with the aqueous solvent becomes worse, the surface functional group amount of the CNT is small, the active point with the dispersing agent and the active material is reduced, and there is a possibility of leading to poor dispersion. There is. When the water vapor adsorption amount exceeds 4.5 mg / g, the total amount of Al and Mg contained in the CNT also increases, the purity of the CNT is low, and the excellent characteristics may be hindered. From the balance between dispersibility and characteristics, the water vapor adsorption amount of CNT is more preferably 1 to 4 mg / g.

Specific examples of CNTs usable in the present invention include TCs such as TC-2010, TC-2020, TC-3210L, and TC-1210LN, which are CNTs having a constricted structure disclosed in International Publication No. 2016/076393. Series [manufactured by Toda Kogyo Co., Ltd.] and the like can be mentioned, but are not limited thereto.
In the composition of the present invention, the CNT having the constricted part can be used in combination with other CNTs or conductive materials other than CNT, but the CNT having the constricted part is used alone. Is preferred.

The dispersant can be appropriately selected from those conventionally used as a dispersant for conductive carbon materials such as CNTs. For example, carboxymethylcellulose (CMC), polyvinylpyrrolidone (PVP), acrylic resin emulsion, water-soluble Acrylic polymer, styrene emulsion, silicone emulsion, acrylic silicone emulsion, fluororesin emulsion, EVA emulsion, vinyl acetate emulsion, vinyl chloride emulsion, urethane resin emulsion, triarylamine hyperbranched polymer described in International Publication No. 2014/04280 And polymers having an oxazoline group in the side chain described in International Publication No. 2015/029949. In the present invention, the side chain described in International Publication No. 2015/029949 is included in the side chain. Dispersing agents and comprising a polymer having a Kisazorin group, it is preferable to use a dispersant comprising a triarylamine hyperbranched polymer of WO 2014/04280 Patent forth.

A polymer having an oxazoline group in the side chain (hereinafter referred to as oxazoline polymer) is obtained by radical polymerization of an oxazoline monomer having a polymerizable carbon-carbon double bond-containing group at the 2-position as shown in Formula (1). Preferred is a vinyl polymer having a repeating unit bonded to the polymer main chain or spacer group at the 2-position of the oxazoline ring and having an oxazoline group in the side chain.

X represents a polymerizable carbon-carbon double bond-containing group, and R ¹ to R ⁴ are independently of each other a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or a 6 to 20 carbon atoms. An aryl group or an aralkyl group having 7 to 20 carbon atoms is represented.
The polymerizable carbon-carbon double bond-containing group of the oxazoline monomer is not particularly limited as long as it contains a polymerizable carbon-carbon double bond, but a chain containing a polymerizable carbon-carbon double bond. And a hydrocarbon group having 2 to 8 carbon atoms such as vinyl group, allyl group and isopropenyl group is preferable.
Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The alkyl group having 1 to 5 carbon atoms may be linear, branched or cyclic, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group. Tert-butyl group, n-pentyl group, cyclohexyl group and the like.
Specific examples of the aryl group having 6 to 20 carbon atoms include phenyl group, xylyl group, tolyl group, biphenylyl group, naphthyl group and the like.
Specific examples of the aralkyl group having 7 to 20 carbon atoms include benzyl group, phenylethyl group, phenylcyclohexyl group and the like.

Specific examples of the oxazoline monomer having a polymerizable carbon-carbon double bond-containing group at the 2-position represented by the formula (1) include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-4-propyl-2-oxazoline, 2-vinyl-4-butyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2- Vinyl-5-ethyl-2-oxazoline, 2-vinyl-5-propyl-2-oxazoline, 2-vinyl-5-butyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4- Methyl-2-oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl-4-propyl-2-oxazoline, 2- Sopropenyl-4-butyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-5-propyl-2-oxazoline, 2 -Isopropenyl-5-butyl-2-oxazoline and the like can be mentioned, but 2-isopropenyl-2-oxazoline is preferable from the viewpoint of availability.

In consideration of preparing the composition using an aqueous solvent, the oxazoline polymer is also preferably water-soluble.
Such a water-soluble oxazoline polymer may be a homopolymer of the oxazoline monomer represented by the above formula (1), but has a oxazoline monomer and a hydrophilic functional group in order to further enhance the solubility in water (meta ) It is preferable to be obtained by radical polymerization of at least two monomers with an acrylate monomer.

Specific examples of the (meth) acrylic monomer having a hydrophilic functional group include (meth) acrylic acid, 2-hydroxyethyl acrylate, methoxypolyethylene glycol acrylate, monoesterified product of acrylic acid and polyethylene glycol, acrylic acid 2-aminoethyl and its salt, 2-hydroxyethyl methacrylate, methoxypolyethylene glycol methacrylate, monoesterified product of methacrylic acid and polyethylene glycol, 2-aminoethyl methacrylate and its salt, sodium (meth) acrylate, ( Ammonium methacrylate, (meth) acrylonitrile, (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, sodium styrenesulfonate, etc. The like, which may be used singly or may be used in combination of two or more. Among these, (meth) acrylic acid methoxypolyethylene glycol and monoesterified products of (meth) acrylic acid and polyethylene glycol are preferable.

Moreover, in the range which does not have a bad influence on the CNT dispersibility of an oxazoline polymer, other monomers other than the said oxazoline monomer and the (meth) acrylic-type monomer which has a hydrophilic functional group can be used together.
Specific examples of other monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, (meth) acrylic. (Meth) acrylic acid ester monomers such as perfluoroethyl acid and phenyl (meth) acrylate; α-olefin monomers such as ethylene, propylene, butene and pentene; haloolefins such as vinyl chloride, vinylidene chloride and vinyl fluoride Monomers: Styrene monomers such as styrene and α-methyl styrene; Vinyl ester monomers such as vinyl acetate and vinyl propionate; Vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether, and the like. But two or more A combination of the above may also be used.

In the monomer component used in the production of the oxazoline polymer used in the present invention, the content of the oxazoline monomer is preferably 10% by mass or more, more preferably 20% by mass or more from the viewpoint of further increasing the CNT dispersibility of the obtained oxazoline polymer. Preferably, 30% by mass or more is even more preferable. In addition, the upper limit of the content rate of the oxazoline monomer in a monomer component is 100 mass%, and the homopolymer of an oxazoline monomer is obtained in this case.
On the other hand, the content of the (meth) acrylic monomer having a hydrophilic functional group in the monomer component is preferably 10% by mass or more, more preferably 20% by mass or more from the viewpoint of further increasing the water solubility of the obtained oxazoline polymer. 30% by mass or more is even more preferable.
In addition, as described above, the content of other monomers in the monomer component is a range that does not affect the CNT dispersibility of the obtained oxazoline polymer, and since it varies depending on the type, it cannot be determined unconditionally. What is necessary is just to set suitably in the range of 5-95 mass%, Preferably it is 10-90 mass%.

The average molecular weight of the oxazoline polymer is not particularly limited, but the weight average molecular weight is preferably 1,000 to 2,000,000, and more preferably 2,000 to 1,000,000. The weight average molecular weight is a polystyrene conversion value determined by gel permeation chromatography.

The oxazoline polymer that can be used in the present invention can be synthesized by a conventional radical polymerization of the above-mentioned monomers, but can also be obtained as a commercial product, and as such a commercial product, for example, Epocross WS-300 (Manufactured by Nippon Shokubai Co., Ltd., solid content concentration 10% by mass, aqueous solution), Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd., solid content concentration 25% by mass, aqueous solution), Epocross WS-500 (manufactured by Nippon Shokubai Co., Ltd.) Manufactured, solid content concentration 39% by mass, water / 1-methoxy-2-propanol solution), Poly (2-ethyl-2-oxazoline) (Aldrich), Poly (2-ethyl-2-oxazoline) (AlfaAesar), Poly (2-ethyl-2-oxazole) (VWR International, LLC) etc. Is mentioned.
In addition, when it is marketed as a solution, it may be used as it is, or it may be used after substituting with the target solvent.

Further, hyperbranched polymers obtained by condensation polymerization of triarylamines and aldehydes and / or ketones represented by the following formulas (2) and (3) under acidic conditions are also preferably used.

In the above formulas (2) and (3), Ar ¹ to Ar ³ each independently represents any divalent organic group represented by formulas (4) to (8). The substituted or unsubstituted phenylene group represented by (4) is preferred.

In the formulas (2) and (3), Z ¹ and Z ² are each independently a hydrogen atom, an alkyl group which may have a branched structure having 1 to 5 carbon atoms, or the formula (9) (1) represents any monovalent organic group represented by (12) (provided that Z ¹ and Z ² do not simultaneously become the above alkyl group), but Z ¹ and Z ² are each independently A hydrogen atom, a 2- or 3-thienyl group, or a group represented by the formula (9) is preferable, and in particular, ^one of Z ¹ and Z ² is a hydrogen atom, and the other is a hydrogen atom, 2- or More preferred is a 3-thienyl group, a group represented by the formula (9), particularly those in which R ¹⁴¹ is a phenyl group, or R ¹⁴¹ is a methoxy group.
When R ¹⁴¹ is a phenyl group, an acidic group may be introduced onto the phenyl group when a method for introducing an acidic group after polymer production is used in the acidic group introduction method described later.
Examples of the alkyl group which may have a branched structure having 1 to 5 carbon atoms include those similar to those exemplified above.

In the above formulas (3) to (8), R ¹⁰¹ to R ¹³⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group which may have a branched structure having 1 to 5 carbon atoms, or a carbon number of 1 Represents an alkoxy group which may have a branched structure of 1 to 5, a carboxyl group, a sulfo group, a phosphoric acid group, a phosphonic acid group or a salt thereof;

Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group which may have a branched structure having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n -Pentyl group and the like.
Examples of the alkoxy group which may have a branched structure having 1 to 5 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, Examples thereof include an n-pentoxy group.
As salts of carboxyl group, sulfo group, phosphoric acid group and phosphonic acid group, alkali metal salts such as sodium and potassium; Group 2 metal salts such as magnesium and calcium; ammonium salts; propylamine, dimethylamine, triethylamine, ethylenediamine, etc. Aliphatic amine salts; alicyclic amine salts such as imidazoline, piperazine and morpholine; aromatic amine salts such as aniline and diphenylamine; and pyridinium salts.

In the above formulas (9) to (12), R ¹³⁹ to R ¹⁶² are each independently a hydrogen atom, a halogen atom, an alkyl group which may have a branched structure having 1 to 5 carbon atoms, or a carbon number of 1 Haloalkyl group, phenyl group, OR ¹⁶³ , COR ¹⁶³ , NR ¹⁶³ R ¹⁶⁴ , COOR ¹⁶⁵ , which may have a branched structure of ˜5 (in these formulas, R ¹⁶³ and R ¹⁶⁴ are each independently hydrogen Represents an atom, an alkyl group which may have a branched structure having 1 to 5 carbon atoms, a haloalkyl group which may have a branched structure having 1 to 5 carbon atoms, or a phenyl group, and R ¹⁶⁵ represents the number of carbon atoms Represents an alkyl group which may have a branched structure of 1 to 5, a haloalkyl group which may have a branched structure of 1 to 5 carbon atoms, or a phenyl group.), Or a carboxyl group, a sulfo group, a phosphorus group Acid groups, phosphonic acid groups or their Represents salt.

Here, the haloalkyl group which may have a branched structure having 1 to 5 carbon atoms includes difluoromethyl group, trifluoromethyl group, bromodifluoromethyl group, 2-chloroethyl group, 2-bromoethyl group, 1,1 -Difluoroethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 2-chloro-1,1,2-trifluoroethyl group, pentafluoroethyl group, 3 -Bromopropyl group, 2,2,3,3-tetrafluoropropyl group, 1,1,2,3,3,3-hexafluoropropyl group, 1,1,1,3,3,3-hexafluoropropane Examples include -2-yl group, 3-bromo-2-methylpropyl group, 4-bromobutyl group, perfluoropentyl group and the like.
Examples of the halogen atom and the alkyl group which may have a branched structure having 1 to 5 carbon atoms include the same groups as those exemplified in the above formulas (3) to (8).

In particular, in consideration of further improving the adhesion to the current collector, the hyperbranched polymer has a carboxyl group, in at least one aromatic ring of the repeating unit represented by the formula (2) or (3), Those having at least one acidic group selected from a sulfo group, a phosphoric acid group, a phosphonic acid group, and salts thereof are preferable, and those having a sulfo group or a salt thereof are more preferable.

Examples of the aldehyde compound used for the production of the hyperbranched polymer include formaldehyde, paraformaldehyde, acetaldehyde, propylaldehyde, butyraldehyde, isobutyraldehyde, valeraldehyde, capronaldehyde, 2-methylbutyraldehyde, hexylaldehyde, undecylaldehyde, 7 -Saturated aliphatic aldehydes such as methoxy-3,7-dimethyloctylaldehyde, cyclohexanecarboxaldehyde, 3-methyl-2-butyraldehyde, glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, adipine aldehyde; acrolein, methacrolein Unsaturated aldehydes such as: furfural, pyridine aldehyde, heterocyclic aldehydes such as thiophene aldehyde Benzaldehyde, tolylaldehyde, trifluoromethylbenzaldehyde, phenylbenzaldehyde, salicylaldehyde, anisaldehyde, acetoxybenzaldehyde, terephthalaldehyde, acetylbenzaldehyde, formylbenzoic acid, methyl formylbenzoate, aminobenzaldehyde, N, N-dimethylaminobenzaldehyde, N , N-diphenylaminobenzaldehyde, naphthyl aldehyde, anthryl aldehyde, aromatic aldehydes such as phenanthryl aldehyde, aralkyl aldehydes such as phenylacetaldehyde, 3-phenylpropionaldehyde, and the like. Is preferably used.

Examples of the ketone compound used in the production of the hyperbranched polymer include alkyl aryl ketones and diaryl ketones, such as acetophenone, propiophenone, diphenyl ketone, phenyl naphthyl ketone, dinaphthyl ketone, phenyl tolyl ketone, and ditolyl ketone. Etc.

As shown in the following scheme 1, the hyperbranched polymer used in the present invention includes, for example, a triarylamine compound that can give the above-described triarylamine skeleton as represented by the following formula (A), and the following formula, for example: It can be obtained by condensation polymerization of an aldehyde compound and / or a ketone compound as shown in (B) in the presence of an acid catalyst.
When a bifunctional compound (C) such as phthalaldehyde such as terephthalaldehyde is used as the aldehyde compound, not only the reaction shown in Scheme 1 but also the reaction shown in Scheme 2 below occurs. In some cases, a hyperbranched polymer having a crosslinked structure in which two functional groups contribute to the condensation reaction may be obtained.

(In the formula, Ar ¹ to Ar ³ and Z ¹ to Z ² represent the same meaning as described above.)

(In the formula, Ar ¹ to Ar ³ and R ¹⁰¹ to R ¹⁰⁴ have the same meaning as described above.)

In the condensation polymerization reaction, an aldehyde compound and / or a ketone compound can be used at a ratio of 0.1 to 10 equivalents with respect to 1 equivalent of the aryl group of the triarylamine compound.
Examples of the acid catalyst include mineral acids such as sulfuric acid, phosphoric acid and perchloric acid; organic sulfonic acids such as p-toluenesulfonic acid and p-toluenesulfonic acid monohydrate; carboxylic acids such as formic acid and oxalic acid. Etc. can be used.
The amount of the acid catalyst used is variously selected depending on the type thereof, but is usually 0.001 to 10,000 parts by mass, preferably 0.01 to 1,000 parts by mass with respect to 100 parts by mass of the triarylamines. More preferably, it is 0.1 to 100 parts by mass.

Although the above condensation reaction can be carried out without a solvent, it is usually carried out using a solvent. Any solvent that does not inhibit the reaction can be used. For example, cyclic ethers such as tetrahydrofuran and 1,4-dioxane; N, N-dimethylformamide (DMF), N, N-dimethylacetamide ( DMAc), amides such as N-methyl-2-pyrrolidone (NMP); ketones such as methyl isobutyl ketone and cyclohexanone; halogenated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane and chlorobenzene; benzene, Examples thereof include aromatic hydrocarbons such as toluene and xylene, and cyclic ethers are particularly preferable. These solvents can be used alone or in combination of two or more.
In addition, if the acid catalyst used is a liquid such as formic acid, the acid catalyst can also serve as a solvent.

The reaction temperature during the condensation is usually 40 to 200 ° C. The reaction time is variously selected depending on the reaction temperature, but is usually about 30 minutes to 50 hours.

When introducing an acidic group into a highly branched polymer, it is introduced in advance on the aromatic ring of the above-mentioned triarylamine compound, aldehyde compound or ketone compound, which is the polymer raw material, and is introduced by a method for producing a highly branched polymer using this. However, the obtained hyperbranched polymer may be introduced by a method of treating with a reagent capable of introducing an acidic group on the aromatic ring, but the latter method may be used in consideration of the ease of production. preferable.
In the latter method, the method for introducing the acidic group onto the aromatic ring is not particularly limited, and may be appropriately selected from conventionally known various methods according to the type of the acidic group.
For example, when a sulfo group is introduced, a technique of sulfonation using an excessive amount of sulfuric acid can be used.

The average molecular weight of the hyperbranched polymer is not particularly limited, but the weight average molecular weight is preferably 1,000 to 2,000,000, and more preferably 2,000 to 1,000,000.
Specific examples of the hyperbranched polymer include, but are not limited to, those represented by the following formula.

In the present invention, the mixing ratio of the CNT and the dispersant can be about 1,000: 1 to 1: 100 by mass ratio.
Further, the concentration of the dispersant in the composition is not particularly limited as long as it is a concentration capable of dispersing CNTs in a solvent, but is preferably about 0.001 to 30% by mass in the composition, More preferably, it is about 0.002 to 20% by mass.
Furthermore, the concentration of CNT in the composition varies in the amount of the target undercoat layer and the required mechanical, electrical, and thermal characteristics, and at least a part of the CNT is present. Although it is arbitrary as long as it can be isolated and dispersed to produce an undercoat layer within a practical weight range, it is preferably about 0.0001 to 30% by mass in the composition, and about 0.001 to 20% by mass. More preferably, it is more preferably about 0.001 to 10% by mass.

The solvent is not particularly limited as long as it is conventionally used for the preparation of a conductive composition. For example, water; ethers such as tetrahydrofuran (THF), diethyl ether, 1,2-dimethoxyethane (DME); Halogenated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane; N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), etc. Amides; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; Alcohols such as methanol, ethanol, isopropanol, n-butanol, t-butanol, n-propanol; n-heptane, n-hexane, cyclohexane, etc. Aliphatic hydrocarbons; benzene, torr Aromatic solvents such as ethylene, xylene and ethylbenzene; glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and propylene glycol monomethyl ether; and organic solvents such as glycols such as ethylene glycol and propylene glycol . These solvent can be used individually by 1 type or in mixture of 2 or more types.
In particular, water, NMP, DMF, THF, methanol, ethanol, n-propanol, isopropanol, n-butanol, and t-butanol are preferable because the ratio of isolated dispersion of CNT can be improved. From the viewpoint of improving coatability, it is preferable to include methanol, ethanol, n-propanol, isopropanol, n-butanol, and t-butanol. Moreover, it is preferable that water is included from the point that cost can be reduced. These solvents can be used singly or in combination of two or more for the purpose of increasing the ratio of isolated dispersion, increasing coatability, and reducing cost. When a mixed solvent of water and alcohols is used, the mixing ratio is not particularly limited, but water: alcohols = 1: 1 to 10: 1 are preferable in terms of mass ratio.

In the composition of the present invention, a polymer serving as a matrix may be added. Examples of the matrix polymer include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer [P (VDF-HFP)], Fluorine resins such as vinylidene fluoride-trichloroethylene copolymer [P (VDF-CTFE)]; polyvinylpyrrolidone, ethylene-propylene-diene terpolymer, PE (polyethylene), PP (polypropylene), Polyolefin resins such as EVA (ethylene-vinyl acetate copolymer), EEA (ethylene-ethyl acrylate copolymer); PS (polystyrene), HIPS (high impact polystyrene), AS (acrylonitrile-styrene copolymer), ABS (Acryroni Ryl-butadiene-styrene copolymer), MS (methyl methacrylate-styrene copolymer), polystyrene resins such as styrene-butadiene rubber; polycarbonate resin; vinyl chloride resin; polyamide resin; polyimide resin; (Meth) acrylic resins such as PMMA (polymethyl methacrylate); PET (polyethylene terephthalate), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, PLA (polylactic acid), poly-3-hydroxybutyric acid, polycaprolactone, poly Polyethylene resins such as butylene succinate and polyethylene succinate / adipate; polyphenylene ether resin; modified polyphenylene ether resin; polyacetal resin; polysulfone resin; Polysulfuric resin; Polyvinyl alcohol resin; Polyglycolic acid; Modified starch; Cellulose acetate, carboxymethyl cellulose, cellulose triacetate; Chitin, chitosan; Thermoplastic resin such as lignin; Emeraldine base that is polyaniline and its half-oxidized; Polythiophene; Polypyrrole; polyphenylene vinylene; polyphenylene; conductive polymer such as polyacetylene; and epoxy resin; urethane acrylate; phenol resin; melamine resin; urea resin; thermosetting resin such as alkyd resin; In the conductive carbon material dispersion of the present invention, it is preferable to use water as a solvent, so that the matrix polymer is also water-soluble, such as sodium polyacrylate, carboxymethyl. Examples include sodium cellulose cellulose, water-soluble cellulose ether, sodium alginate, polyvinyl alcohol, polystyrene sulfonic acid, polyethylene glycol and the like, and particularly, sodium polyacrylate and sodium carboxymethyl cellulose are preferable.

The matrix polymer can also be obtained as a commercial product. Examples of such a commercial product include sodium polyacrylate (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization 2,700 to 7,500), carboxy Sodium methylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.), sodium alginate (manufactured by Kanto Chemical Co., Ltd., deer grade 1), Metrol's SH series (hydroxypropylmethylcellulose, Shin-Etsu Chemical Co., Ltd.), Metrolose SE series (hydroxyl) Ethyl methyl cellulose, manufactured by Shin-Etsu Chemical Co., Ltd.), JC-25 (completely saponified polyvinyl alcohol, manufactured by Nippon Vineyard Poval Co., Ltd.), JM-17 (intermediate saponified polyvinyl alcohol, Nippon Vinegared / Poval) Manufactured by Co., Ltd.), JP-03 (partially saponified polyvinyl alcohol, Nippon Vinegar Poval) Ltd.), polystyrene sulfonic acid (Aldrich Corp., solid concentration 18 wt%, aqueous solution), and the like.
The content of the matrix polymer is not particularly limited, but is preferably about 0.0001 to 99% by mass, more preferably about 0.001 to 90% by mass in the composition.

The composition of the present invention may contain a crosslinking agent that causes a crosslinking reaction with the dispersant to be used or a crosslinking agent that self-crosslinks. These crosslinking agents are preferably dissolved in the solvent used.
The crosslinking agent for the oxazoline polymer is particularly limited as long as it is a compound having two or more functional groups having reactivity with an oxazoline group such as a carboxyl group, a hydroxyl group, a thiol group, an amino group, a sulfinic acid group, and an epoxy group. Although not intended, compounds having two or more carboxyl groups are preferred. In addition, a compound having a functional group that causes a crosslinking reaction by heating during thin film formation or in the presence of an acid catalyst, such as a sodium salt, potassium salt, lithium salt, or ammonium salt of a carboxylic acid is also crosslinked. It can be used as an agent.
Specific examples of compounds that undergo a crosslinking reaction with an oxazoline group include metal salts of synthetic polymers such as polyacrylic acid and copolymers thereof and natural polymers such as carboxymethylcellulose and alginic acid that exhibit crosslinking reactivity in the presence of an acid catalyst. And ammonium salts of the above synthetic polymers and natural polymers that exhibit crosslinking reactivity by heating, especially sodium polyacrylate that exhibits crosslinking reactivity in the presence of an acid catalyst or under heating conditions, Preference is given to lithium polyacrylate, ammonium polyacrylate, sodium carboxymethylcellulose, lithium carboxymethylcellulose, carboxymethylcellulose ammonium and the like.

Such a compound that causes a crosslinking reaction with an oxazoline group can also be obtained as a commercial product. Examples of such a commercial product include sodium polyacrylate (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization of 2, 700-7,500), sodium carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.), sodium alginate (manufactured by Kanto Chemical Co., Ltd., deer grade 1), Aron A-30 (ammonium polyacrylate, Toagosei Co., Ltd.) ), Solid concentration 32% by mass, aqueous solution), DN-800H (carboxymethylcellulose ammonium, manufactured by Daicel Finechem Co., Ltd.), ammonium alginate (produced by Kimika Co., Ltd.), and the like.

Examples of the crosslinking agent for the triarylamine-based hyperbranched polymer include melamine-based, substituted urea-based, or their polymer-based crosslinking agents. These crosslinking agents may be used alone or in combination of two or more. Can be used. Preferably, the cross-linking agent has at least two cross-linking substituents, such as CYMEL (registered trademark), methoxymethylated glycoluril, butoxymethylated glycoluril, methylolated glycoluril, methoxymethylated melamine, butoxymethyl. Melamine, methylolated melamine, methoxymethylated benzoguanamine, butoxymethylated benzoguanamine, methylolated benzoguanamine, methoxymethylated urea, butoxymethylated urea, methylolated urea, methoxymethylated thiourea, methoxymethylated thiourea, methylolated thio Examples include compounds such as urea, and condensates of these compounds.

Examples of the crosslinking agent that self-crosslinks include, for example, an aldehyde group, an epoxy group, a vinyl group, an isocyanate group, an alkoxy group, a carboxyl group, an aldehyde group, an amino group, an isocyanate group, an epoxy group, and an amino group. Compounds having crosslinkable functional groups that react with each other in the same molecule, such as isocyanate groups and aldehyde groups, hydroxyl groups that react with the same crosslinkable functional groups (dehydration condensation), mercapto groups (disulfide bonds), Examples thereof include compounds having an ester group (Claisen condensation), a silanol group (dehydration condensation), a vinyl group, an acrylic group, and the like.
Specific examples of the crosslinking agent that self-crosslinks include polyfunctional acrylate, tetraalkoxysilane, a monomer having a blocked isocyanate group, a hydroxyl group, a carboxylic acid, and an amino group that exhibit crosslinking reactivity in the presence of an acid catalyst. The block copolymer of the monomer which has is mentioned.

Such a self-crosslinking crosslinking agent can also be obtained as a commercial product. Examples of such a commercial product include A-9300 (ethoxylated isocyanuric acid triacrylate, Shin-Nakamura Chemical ( ), A-GLY-9E (Ethoxylatedｉｎglycerine triacrylate (EO9 mol), Shin-Nakamura Chemical Co., Ltd.), A-TMMT (pentaerythritol tetraacrylate, Shin-Nakamura Chemical Co., Ltd.), tetraalkoxysilane In the case of tetramethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.), tetraethoxysilane (manufactured by Toyoko Chemical Co., Ltd.), and polymers having a blocked isocyanate group, Elastron series E-37, H-3, H38, BAP, NEW BAP-15, C-52, F-2 9, W-11P, MF-9, MF-25K (Daiichi Kogyo Seiyaku Co., Ltd.).

The amount of these crosslinking agents to be added varies depending on the solvent used, the substrate used, the required viscosity, the required film shape, etc., but is 0.001 to 80% by mass, preferably 0.8%, based on the dispersant. The amount is from 01 to 50% by mass, more preferably from 0.05 to 40% by mass. These cross-linking agents may cause a cross-linking reaction by self-condensation, but they cause a cross-linking reaction with the dispersant. If a cross-linkable substituent is present in the dispersant, the cross-linking reaction is caused by those cross-linkable substituents. Promoted.
In the present invention, as a catalyst for accelerating the crosslinking reaction, p-toluenesulfonic acid, trifluoromethanesulfonic acid, pyridinium p-toluenesulfonic acid, salicylic acid, sulfosalicylic acid, citric acid, benzoic acid, hydroxybenzoic acid, naphthalenecarboxylic acid And / or thermal acid generators such as 2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyl tosylate, and organic sulfonic acid alkyl ester can be added. .
The addition amount of the catalyst is 0.0001 to 20% by mass, preferably 0.0005 to 10% by mass, and more preferably 0.001 to 3% by mass with respect to the CNT dispersant.

The method for preparing the composition of the present invention is not particularly limited, and a dispersion is prepared by mixing CNT, a dispersant and a solvent, and a matrix polymer, a crosslinking agent, and the like used as necessary in an arbitrary order. do it.
At this time, it is preferable to disperse the mixture, and this treatment can further improve the CNT dispersion ratio. Examples of the dispersion treatment include mechanical treatment, wet treatment using a ball mill, bead mill, jet mill, and the like, and ultrasonic treatment using a bath-type or probe-type sonicator. In particular, wet treatment using a jet mill. Or sonication is preferred.
The time for the dispersion treatment is arbitrary, but is preferably about 1 minute to 10 hours, and more preferably about 5 minutes to 5 hours. At this time, heat treatment may be performed as necessary.
In addition, when using arbitrary components, such as a matrix polymer, you may add these, after preparing the mixture which consists of CNT, a dispersing agent, and a solvent.

In the present invention, the solid content concentration of the composition is not particularly limited, but considering the formation of the undercoat layer with a desired basis weight and film thickness, it is preferably 20% by mass or less, and 15% by mass. The following is more preferable, and 10 mass% or less is still more preferable.
Moreover, the minimum is arbitrary, but 0.1 mass% or more is preferable from a practical viewpoint, 0.5 mass% or more is more preferable, and 1 mass% or more is still more preferable.
In addition, solid content is the total amount of components other than the solvent which comprises a composition.

An undercoat foil can be produced by applying the composition described above to at least one surface of a current collector and then naturally or heat drying it to form an undercoat layer.
The thickness of the undercoat layer is preferably 1 nm to 10 μm, more preferably 1 nm to 1 μm, and even more preferably 1 to 500 nm in consideration of reducing the internal resistance of the resulting device.
The film thickness of the undercoat layer is, for example, by cutting out a test piece of an appropriate size from the undercoat foil, exposing the cross section by a technique such as tearing it by hand, and by microscopic observation such as a scanning electron microscope (SEM), It can obtain | require from the part which the undercoat layer exposed in the cross-sectional part.

Basis weight of the undercoat layer per one surface of the current collector is not particularly limited as long as it satisfies the above thickness is preferably 1000 mg / m ² or less, more preferably 500mg / m ^2, 300mg / m ² or less is more preferable, and 200 mg / m ² or less is more preferable.
On the other hand, in order to ensure the function of the undercoat layer and to obtain a battery having excellent characteristics with good reproducibility, the basis weight of the undercoat layer per side of the current collector is preferably 1 mg / m ² or more, more preferably 5 mg / m ^2. m ² or more, more preferably 10 mg / m ² or more, and further preferably 15 mg / m ² or more.

The basis weight of the undercoat layer is the ratio of the mass (mg) of the undercoat layer to the area (m ² ) of the undercoat layer. When the undercoat layer is formed in a pattern, the area is an undercoat layer. The area is only the coat layer, and does not include the area of the current collector exposed between the undercoat layers formed in a pattern.
The mass of the undercoat layer is obtained by, for example, cutting a test piece of an appropriate size from the undercoat foil, measuring its mass W0, and then peeling off the undercoat layer from the undercoat foil and peeling off the undercoat layer. The mass W1 is measured and calculated from the difference (W0-W1), or the mass W2 of the current collector is measured in advance, and then the mass W3 of the undercoat foil on which the undercoat layer is formed is measured. The difference (W3−W2) can be calculated.
Examples of the method for removing the undercoat layer include a method of immersing the undercoat layer in a solvent in which the undercoat layer dissolves or swells, and wiping the undercoat layer with a cloth or the like.

The basis weight and the film thickness can be adjusted by a known method. For example, when the undercoat layer is formed by coating, the solid content concentration of the coating liquid for forming the undercoat layer (undercoat layer forming composition), the number of times of coating, the coating liquid inlet of the coating machine It can be adjusted by changing the clearance.
In order to increase the weight per unit area and the film thickness, the solid content concentration is increased, the number of coatings is increased, and the clearance is increased. When it is desired to reduce the weight per unit area and the film thickness, the solid content concentration is lowered, the number of coatings is reduced, or the clearance is reduced.

The ratio of the surface roughness Ra of the undercoat layer to the equivalent film thickness is preferably 50% or more, and is preferably 55% or more in consideration of lowering the resistance of the device to be obtained and further enhancing the resistance increase suppressing effect. Although the upper limit of the said ratio is not specifically limited, 1,000% or less is preferable and 500% or less is more preferable.
Further, the surface roughness Ra of the undercoat layer is not particularly limited as long as the above ratio is satisfied, but is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. Further, the upper limit is not particularly limited as long as it is within the range of the film thickness, but is preferably 1,000 nm or less, and more preferably 500 nm or less.
The surface roughness Ra is an average value (arithmetic value) obtained by measuring any three points in a predetermined region, for example, a region of 30 μm × 30 μm, using an atomic force microscope for the produced undercoat layer. Average roughness).
On the other hand, the equivalent film thickness of the undercoat layer is a value calculated from the basis weight of the undercoat layer when the density of the undercoat layer is 1 g / cm ³ .

As the current collector, those conventionally used as current collectors for electrodes for energy storage devices can be used. For example, copper, aluminum, titanium, stainless steel, nickel, gold, silver and alloys thereof, carbon materials, metal oxides, conductive polymers, etc. can be used, but welding such as ultrasonic welding is applied. When producing an electrode structure, it is preferable to use a metal foil made of copper, aluminum, titanium, stainless steel, or an alloy thereof.
The thickness of the current collector is not particularly limited, but is preferably 1 to 100 μm in the present invention.

Examples of the method for applying the composition include spin coating, dip coating, flow coating, ink jet, casting, spray coating, bar coating, gravure coating, slit coating, roll coating, and flexographic printing. Method, transfer printing method, brush coating, blade coating method, air knife coating method, die coating method, etc., but from the point of work efficiency etc., inkjet method, casting method, dip coating method, bar coating method, blade coating method A roll coating method, a gravure coating method, a flexographic printing method, a spray coating method, and a die coating method are suitable.
The temperature for drying by heating is also arbitrary, but is preferably about 50 to 200 ° C, more preferably about 80 to 150 ° C.

The electrode for energy storage devices of the present invention can be produced by forming an electrode mixture layer on the undercoat layer.
Examples of the energy storage device in the present invention include various energy storage devices such as an electric double layer capacitor, a lithium secondary battery, a lithium ion secondary battery, a proton polymer battery, a nickel hydrogen battery, an aluminum solid capacitor, an electrolytic capacitor, and a lead storage battery. In particular, the undercoat foil of the present invention can be suitably used for electric double layer capacitors and lithium ion secondary batteries.
Here, as an active material, the various active materials conventionally used for the electrode for energy storage devices can be used.
For example, in the case of a lithium secondary battery or a lithium ion secondary battery, a chalcogen compound capable of adsorbing / leaving lithium ions or a lithium ion-containing chalcogen compound, a polyanion compound, a simple substance of sulfur and a compound thereof may be used as a positive electrode active material. it can.
Examples of the chalcogen compound that can adsorb and desorb lithium ions include FeS ₂ , TiS ₂ , MoS ₂ , V ₂ O ₆ , V ₆ O ₁₃ , and MnO ₂ .
Examples of the lithium ion-containing chalcogen compound include LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiMo ₂ O ₄ , LiV ₃ O ₈ , LiNiO ₂ , Li _x Ni _y M _1-y O ₂ (where M is Co Represents at least one metal element selected from Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05 ≦ x ≦ 1.10, 0.5 ≦ y ≦ 1.0) Etc.
Examples of the polyanionic compound include LiFePO ₄ .
Examples of the sulfur compound include Li ₂ S and rubeanic acid.

On the other hand, as the negative electrode active material constituting the negative electrode, at least one element selected from alkali metals, alkali alloys, and elements of Groups 4 to 15 of the periodic table that occlude / release lithium ions, oxides, sulfides, nitrides Or a carbon material capable of reversibly occluding and releasing lithium ions can be used.
Examples of the alkali metal include Li, Na, and K. Examples of the alkali metal alloy include Li—Al, Li—Mg, Li—Al—Ni, Na—Hg, and Na—Zn.
Examples of the simple substance of at least one element selected from Group 4 to 15 elements of the periodic table that store and release lithium ions include silicon, tin, aluminum, zinc, and arsenic.
Similarly, examples of the oxide include tin silicon oxide (SnSiO ₃ ), lithium bismuth oxide (Li ₃ BiO ₄ ), lithium zinc oxide (Li ₂ ZnO ₂ ), lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ), and oxidation. Examples include titanium.
Similarly, examples of the sulfide include lithium iron sulfide (Li _x FeS ₂ (0 ≦ x ≦ 3)) and lithium copper sulfide (Li _x CuS (0 ≦ x ≦ 3)).
Similarly as the nitrides, lithium-containing transition metal nitrides and the like, _{_{specifically, Li x M y N (M}} = Co, Ni, Cu, 0 ≦ x ≦ 3,0 ≦ y ≦ 0.5), Examples thereof include lithium iron nitride (Li ₃ FeN ₄ ).
Examples of the carbon material capable of reversibly occluding and releasing lithium ions include graphite, carbon black, coke, glassy carbon, carbon fiber, carbon nanotube, and a sintered body thereof.

In the case of an electric double layer capacitor, a carbonaceous material can be used as an active material.
Examples of the carbonaceous material include activated carbon and the like, for example, activated carbon obtained by carbonizing a phenol resin and then activating treatment.

The electrode mixture layer is formed by applying an active material described above, an electrode slurry prepared by combining the binder polymer described below and a solvent as necessary, onto the undercoat layer, and then naturally or by heating and drying. can do.

The binder polymer can be appropriately selected from known materials and used, for example, polyvinylidene fluoride (PVdF), polyvinylpyrrolidone, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride- Hexafluoropropylene copolymer [P (VDF-HFP)], vinylidene fluoride-trichloroethylene copolymer [P (VDF-CTFE)], polyvinyl alcohol, polyimide, ethylene-propylene-diene ternary copolymer Examples thereof include conductive polymers such as coalescence, styrene-butadiene rubber, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and polyaniline.
The added amount of the binder polymer is preferably 0.1 to 20 parts by mass, particularly 1 to 10 parts by mass with respect to 100 parts by mass of the active material.
Examples of the solvent include the solvents exemplified in the above solvent for the composition, and may be appropriately selected according to the type of the binder, but NMP is preferable in the case of a water-insoluble binder such as PVdF. In the case of a water-soluble binder such as PAA, water is preferable.

Note that the electrode slurry may contain a conductive material. Examples of the conductive material include carbon black, ketjen black, acetylene black, carbon whisker, carbon fiber, natural graphite, artificial graphite, titanium oxide, ruthenium oxide, aluminum, nickel and the like.

Examples of the method for applying the electrode slurry include the same method as the method for applying the composition described above.
The temperature for drying by heating is arbitrary, but is preferably about 50 to 400 ° C, more preferably about 80 to 150 ° C.

The electrode may be pressed as necessary. At this time, the press pressure is preferably 1 kN / cm or more. As the pressing method, a generally adopted method can be used, but a die pressing method and a roll pressing method are particularly preferable. The pressing pressure is not particularly limited, but is preferably 2 kN / cm or more, and more preferably 3 kN / cm or more. The upper limit of the pressing pressure is preferably about 40 kN / cm, more preferably about 30 kN / cm.

An energy storage device according to the present invention includes the above-described electrode for an energy storage device, and more specifically includes at least a pair of positive and negative electrodes, a separator interposed between these electrodes, and an electrolyte. And at least one of the positive and negative electrodes is composed of the energy storage device electrode described above.
Since this energy storage device is characterized by the use of the above-described electrode for energy storage device as an electrode, other device constituent members such as separators and electrolytes may be appropriately selected from known materials and used. it can.
Examples of the separator include a cellulose separator and a polyolefin separator.
The electrolyte may be either liquid or solid, and may be either aqueous or non-aqueous. The electrode for an energy storage device of the present invention is practically sufficient even when applied to a device using a non-aqueous electrolyte. Performance can be demonstrated.

Examples of the non-aqueous electrolyte include a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous organic solvent.
Examples of electrolyte salts include lithium salts such as lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, and lithium trifluoromethanesulfonate; tetramethylammonium hexafluorophosphate, tetraethylammonium hexafluorophosphate, tetrapropylammonium hexa Quaternary ammonium salts such as fluorophosphate, methyltriethylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, tetraethylammonium perchlorate, lithium imides such as lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide, etc. It is done.
Examples of the non-aqueous organic solvent include alkylene carbonates such as propylene carbonate, ethylene carbonate, and butylene carbonate; dialkyl carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; nitriles such as acetonitrile; and amides such as dimethylformamide. .

The form of the energy storage device is not particularly limited, and conventionally known various types of cells such as a cylindrical type, a flat wound square type, a laminated square type, a coin type, a flat wound laminated type, and a laminated laminate type are adopted. can do.
When applied to a coin type, the above-described electrode for an energy storage device of the present invention may be used by punching it into a predetermined disk shape.
For example, in a lithium ion secondary battery, one electrode is placed on a lid to which a washer and a spacer of a coin cell are welded, and a separator of the same shape impregnated with an electrolytic solution is stacked thereon. The energy storage device electrode of the present invention can be overlaid with the composite material layer facing down, a case and a gasket can be placed thereon, and sealed with a coin cell caulking machine.

When applied to the laminated laminate type, the electrode mixture layer is welded to the metal tab at the portion where the electrode mixture layer is not formed (welded part) in the electrode formed on part or the entire surface of the undercoat layer. The obtained electrode structure may be used. In the case where welding is performed at a portion where the undercoat layer is formed and the electrode mixture layer is not formed, the basis weight of the undercoat layer per surface of the current collector is preferably 0.1 g / m ² or less, more preferably 0.09 g / m ² or less, even more preferably less than 0.05 g / m ^2.
In this case, one or a plurality of electrodes constituting the electrode structure may be used, but generally a plurality of positive and negative electrodes are used.
The plurality of electrodes for forming the positive electrode are preferably alternately stacked one by one with the plurality of electrodes for forming the negative electrode, and the separator described above is interposed between the positive electrode and the negative electrode. It is preferable.
Even if the metal tab is welded at the welded portion of the outermost electrode of the plurality of electrodes, the metal tab is welded with the metal tab sandwiched between the welded portions of any two adjacent electrodes among the plurality of electrodes. Also good.

The material of the metal tab is not particularly limited as long as it is generally used for energy storage devices. For example, metal such as nickel, aluminum, titanium, copper, etc .; stainless steel, nickel alloy, aluminum alloy An alloy such as a titanium alloy or a copper alloy can be used, but in view of welding efficiency, an alloy including at least one metal selected from aluminum, copper and nickel is preferable.
The shape of the metal tab is preferably a foil shape, and the thickness is preferably about 0.05 to 1 mm.

As a welding method, a known method used for metal-to-metal welding can be used. Specific examples thereof include TIG welding, spot welding, laser welding, ultrasonic welding, and the like. It is preferable to join the metal tab.
As a technique of ultrasonic welding, for example, a plurality of electrodes are arranged between an anvil and a horn, a metal tab is arranged in a welded portion, and ultrasonic welding is applied to collect a plurality of electrodes. The technique of welding first and then welding a metal tab is mentioned.
In the present invention, in any of the methods, the metal tab and the electrode are not only welded at the welded portion, but a plurality of electrodes are also ultrasonically welded to each other.
The pressure, frequency, output, processing time, and the like during welding are not particularly limited, and may be set as appropriate in consideration of the material used, the presence or absence of the undercoat layer, the basis weight, and the like.
The electrode structure produced as described above is housed in a laminate pack, and after injecting the above-described electrolyte, heat sealing is performed to obtain a laminate cell.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example. In addition, the apparatus used for the measurement etc. is as follows.
(1) Probe-type ultrasonic irradiation device (dispersion processing)
Hielscher Ultrasonics, UIP1000
(2) Wire bar coater (undercoat layer formation)
PM-9050MC, manufactured by SMT Co., Ltd.
(3) Homo disperser (mixing of electrode slurry)
Manufactured by Primics Co., Ltd. K. Robomix (with Homodisper 2.5 type (φ32))
(4) Thin film swirl type high speed mixer (mixing of electrode slurry)
Primics Co., Ltd., filmics type 40 (5) Rotating / revolving mixer (defoaming electrode slurry)
Shintaro Awatori (ARE-310), manufactured by Shinky Corporation
(6) Roll press machine (electrode compression)
SA-602, manufactured by Takumi Giken Co., Ltd.
(7) Charge / discharge measuring device (secondary battery evaluation)
TOSCAT-3100 manufactured by Toyo System Co., Ltd.
(8) Coin cell caulking machine, made by Hosen Co., Ltd., manual coin caulking machine CR2032
(9) Transmission electron microscope (measurement of CNT diameter)
H-8000, manufactured by Hitachi, Ltd.
(10) Powder resistance measurement system Made by Mitsubishi Chemical Analytech Co., Ltd., powder resistance measurement system MCP-PD51 and resistivity meter Loresta GP
Measurement condition 4 probe probe, electrode interval: 3 mm, electrode radius: 0.7 mm, sample radius: 10 mm, applied pressure: 4 to 25 kN / cm ²
Density and conductivity measurement method Density and conductivity when 1.0 g of conductive carbon material is packed in a measurement container of a powder resistance measurement system and pressurization is started and pressure is applied under the conditions shown in Table 1. The rate was measured. Further, after obtaining an approximate line from the measured density and conductivity at each pressure by the least square method, the expected conductivity when the density was 1 g / cm ³ was calculated from the obtained approximate line.
(11) Viscometer Device: VISCOMETER TVE-22L manufactured by Toki Sangyo Co., Ltd.
(12) Raman spectroscopic measurement device: ARAMIS, manufactured by Horiba, Ltd.
Measurement conditions <br/> Laser: 633 nm
Grating: 300 Line / mm (other than NC-7000), 1200 Line / mm (NC-7000)
Measurement range: 3100 to 150 cm ^-1
Objective lens: 10x Detector: Synapse CCD detector (no sensitivity correction)
G: 1700-1450cm ^-1
D: 1450-1150cm ^-1
Baseline: 1700-1150 cm ^-1
G / D ratio measurement method Under the above-mentioned measurement conditions, using 5 mg of CNT or carbon black, the G ⁺ band: the largest Raman shift between 1590 and 1605 cm ⁻¹ , and the G ⁻ band between 1580 and 1565 cm ⁻¹ Raman shift with the highest intensity, D band: The peak intensity of the Raman shift with the highest peak intensity between 1330 and 1310 cm ⁻¹ was determined, and the (G ⁺ + G ⁻ ) / D ratio was determined. The baseline for calculating each peak intensity was 1700-1150 cm ⁻¹ .
(13) Elemental analysis device: JM10 manufactured by J Science Lab.
Measuring elements: Hydrogen, carbon, nitrogen Measuring method: Self-integrating method (using a piston pump)
Sample furnace temperature: 1000 ° C
Combustion furnace: 850 ° C
Reduction furnace: 550 ° C
Measurement sample amount: 1.0 mg (error: within ± 10% by mass)
Number of measurements: 3
(14) Atomic Force Microscope Made by Bruker AXS, Dimension Icon
Measurement conditions <br/> Probe: Single crystal Si
Spring constant: 40 N / m
Resonance frequency: 305 kHz
Scanning speed: 0.4Hz

[1] Production of undercoat liquid [Example 1-1]
4. Epocros WS-300 (made by Nippon Shokubai Co., Ltd., solid concentration 10% by weight, weight average molecular weight 1.2 × 10 ⁵ , oxazoline group amount 7.7 mmol / g) which is an aqueous solution containing an oxazoline polymer as a dispersant. 0 g, 37.15 g of pure water and 7.35 g of 2-propanol (manufactured by Junsei Chemical Co., Ltd., reagent grade), and CNT-TC-2010 (manufactured by Toda Kogyo Co., Ltd., multilayer) CNT, G / D ratio: 0.997) 0.5 g was mixed. The obtained mixture was subjected to ultrasonic treatment for 30 minutes using a probe type ultrasonic irradiation device to prepare a dispersion liquid in which CNTs were uniformly dispersed. To this, 1.2 g of Aron A-30 (Toagosei Co., Ltd., solid content concentration 31.6% by mass) which is an aqueous solution containing ammonium polyacrylate (PAA-NH ₄ ), 41.35 g of pure water, 7.44 g of 2-propanol (manufactured by Junsei Chemical Co., Ltd., reagent grade) was mixed to prepare an undercoat solution (solid content: 1.38% by mass).

[Comparative Example 1-1]
An undercoat solution was prepared in the same manner as in Example 1-1 except that CNT was changed to VGCF-X (manufactured by Showa Denko KK, multilayer CNT).

[Comparative Example 1-2]
An undercoat solution was prepared in the same manner as in Example 1-1, except that CNT was changed to C-100 (manufactured by Arkema Co., Ltd., multilayer CNT).

[Comparative Example 1-3]
An undercoat solution was prepared in the same manner as in Example 1-1 except that CNT was changed to Baytubes (multilayer CNT manufactured by BAYER).

[Comparative Example 1-4]
An undercoat solution was prepared in the same manner as in Example 1-1 except that CNT was changed to NC-7000 (multilayer CNT manufactured by Nanocyl SA).

The average diameter of each CNT used above was measured by the following procedure.
0.5 g of CNT, 42.08 g of pure water, and 7.43 g of 2-propanol (manufactured by Junsei Chemical Co., Ltd., reagent special grade) were mixed. The obtained mixture was subjected to ultrasonic treatment for 10 minutes using a probe type ultrasonic irradiation device, and the CNT powder was pulverized in a solvent to form fine particles. Although the obtained mixture was heterogeneous, it was dropped on a grid with a carbon support film and dried at room temperature for 10 minutes. This was observed with a transmission electron microscope (TEM) at an acceleration voltage of 200 kV, and four CNTs were randomly photographed at a magnification of 70,000. The diameter of the CNT was directly measured based on the photographed image. The diameter was measured at 5 points at random for each CNT, and the average value was obtained from the measured values at a total of 20 points. The results are shown in Table 1.

The density and conductivity of each CNT used above were measured with a powder resistance measurement system. The results are shown in Table 2.

The G / D ratio and dispersion viscosity of each CNT used above were measured with a Raman spectrophotometer and a viscometer. The results are shown in Table 3.

Each CNT used above was weighed in the range of 0.9 to 1.1 mg and subjected to elemental analysis three times. The carbon content, its average value (n = 3), its standard deviation (n = Table 3 shows 3).

[2] Production of electrode and secondary battery [Example 2-1]
The undercoat solution obtained in Example 1-1 was uniformly spread on a current collector aluminum foil (thickness 15 μm) with a wire bar coater (OSP13, wet film thickness 13 μm), and then dried at 150 ° C. for 30 minutes. An undercoat layer was formed to prepare an undercoat foil.
20 sheets of undercoat foil cut into 5 × 10 cm were prepared. After measuring the mass, the undercoat layer was scraped off with a paper soaked with a 1: 1 (mass ratio) mixture of 2-propanol and water. The mass of the metal foil was measured, and the basis weight of the undercoat layer calculated from the difference in mass before and after scraping was 150 mg / m ² .

31.84 g of lithium iron phosphate (LFP, manufactured by Alees) as an active material, 13.05 g of an NMP solution of polyvinylidene fluoride (PVdF) as a binder (12% by mass, Kureha Co., Ltd., KF polymer L # 1120), conductive As materials, 1.39 g of Denka black and 13.72 g of N-methylpyrrolidone (NMP) were mixed with a homodisper at 8,000 rpm for 1 minute. Next, the slurry was mixed for 60 seconds at a peripheral speed of 20 m / sec using a thin-film swirl type high-speed mixer, and further defoamed at 2,200 rpm for 30 seconds with a rotating / revolving mixer, so that the electrode slurry (solid content concentration 58 Mass%, LFP: PVdF: AB = 91.5: 4.5: 4 (mass ratio)).
The obtained electrode slurry was spread uniformly (wet film thickness 100 μm) on the previously prepared undercoat foil, dried at 80 ° C. for 30 minutes, and then at 120 ° C. for 30 minutes, and the electrode mixture layer on the undercoat layer Then, the electrode was produced by pressure bonding with a roll press.

Four disc-shaped electrodes having a diameter of 10 mm are punched from the obtained electrode, and the mass of the electrode layer (subtracting the mass of the punched electrode from the punched electrode uncoated portion to a diameter of 10 mm), and The thickness of the electrode layer (thickness of the punched electrode minus the thickness of the substrate) was measured, vacuum dried at 120 ° C. for 15 hours, and transferred to a glove box filled with argon.
A stack of 2032-type coin cell (made by Hosen Co., Ltd.) washer and spacer welded with 6 sheets of lithium foil (Honjo Chemical Co., Ltd., thickness 0.17 mm) punched out to a diameter of 14 mm. Installed on it, soaked with electrolyte (made by Kishida Chemical Co., Ltd., ethylene carbonate: diethyl carbonate = 1: 1 (volume ratio), 1 mol / L of lithium hexafluorophosphate as an electrolyte) for 24 hours or more. A separator punched to a diameter of 16 mm (Celguard # 2400, manufactured by Celgard Co., Ltd.) was stacked one by one. Further, the electrodes were stacked from the top with the surface coated with the active material facing down. After dropping one drop of the electrolyte, a case and a gasket were placed and sealed with a coin cell caulking machine. Then, it left still for 24 hours and produced the secondary battery for a test.

[Comparative Examples 2-1 to 2-4]
An undercoat foil and a test secondary battery were produced in the same manner as in Example 2-1, except that the undercoat solution obtained in Comparative Examples 1-1 to 1-4 was used.

[Comparative Example 2-5]
A test secondary battery was fabricated in the same manner as in Example 2-1, except that solid aluminum foil was used as the current collector.

For the undercoat foils produced in Example 2-1 and Comparative Examples 2-2 and 2-4, the basis weight of the undercoat foil and the surface roughness Ra were measured by the following methods, the equivalent film thickness, and the surface The ratio of the roughness Ra to the converted film thickness was calculated. The results are shown in Table 5.

[Weight per unit]
The prepared undercoat foil was cut out to 8 × 16 cm and measured for mass, then immersed in a 0.1N hydrochloric acid aqueous solution to remove only the undercoat layer, and the mass of the metal foil was measured. The basis weight per unit area was determined from the difference in mass before and after removal of the undercoat layer.
[Equivalent film thickness of undercoat layer]
From the basis weight calculated above, the equivalent film thickness was calculated by assuming the density of the undercoat layer to be 1 g / cm ³ .
[Surface roughness Ra]
Three points of the 30 μm × 30 μm region of the prepared undercoat foil were measured using an atomic force microscope, and the average surface roughness Ra (arithmetic average roughness) was determined.

The characteristics of the secondary batteries produced in Example 2-1 and Comparative Examples 2-1 to 2-5 were evaluated. For the purpose of evaluating the influence of the undercoat foil on the positive electrode on the battery, the conditions shown in Table 6 are used in the order of battery aging, DC resistance measurement, cycle characteristic evaluation, and DC resistance measurement using a charge / discharge measuring device. A charge / discharge test was conducted. The results obtained are shown in Table 7.

・ Starting condition: 2-4.5V
-Temperature: Room temperature-Discharge voltage: In Steps 2 and 4, the actual discharge capacity under each discharge condition was 100%, and the voltage at the time of 10% discharge was taken as the discharge voltage.
DC resistance measurement: DC resistance was calculated from the current value and discharge voltage under each discharge condition in Steps 2 and 4 for four test batteries, and the average value was obtained.

As shown in Table 7, in the secondary battery produced in Example 2-1, the CNT forming the undercoat layer has a constricted portion defined in the present invention, and has a predetermined diameter, conductivity, Since CNTs having a density and a G / D ratio and having a standard deviation of the carbon content obtained by elemental analysis of a predetermined value or more are used, the batteries manufactured in Comparative Examples 2-1 to 2-5 were used. In comparison, it can be seen that the direct current resistance of the battery is low and the increase in resistance after the cycle test is also suppressed.
In addition, by using the CNT described above, as shown in Table 7, in the secondary battery manufactured in Example 2-1, the surface roughness Ra of the undercoat layer was optimized. It can be seen that the direct current resistance of the battery is low and the increase in resistance after the cycle test is suppressed as compared with the battery manufactured in the comparative example.

1 Parallel part 2 Tube outer diameter of parallel part 3 Constriction part 4 Tube outer diameter of constriction part

Claims

Including carbon nanotubes, carbon nanotube dispersant, and solvent,
The composition for forming an undercoat layer of an energy storage device, wherein the carbon nanotube has a constricted portion.
The composition for forming an undercoat layer of an energy storage device according to claim 1, wherein a geometric average diameter (M D ) of the outer diameter (D) of the carbon nanotube is 5 to 30 nm.
The composition for forming an undercoat layer of an energy storage device according to claim 1 or 2, wherein the carbon nanotube dispersant contains a vinyl polymer or a triarylamine hyperbranched polymer containing an oxazoline group in a side chain.
An undercoat layer obtained from the undercoat layer forming composition for an energy storage device according to any one of claims 1 to 3.
The undercoat layer according to claim 4, wherein the basis weight is 1000 mg / m 2 or less.
The undercoat layer according to claim 5, wherein the basis weight is 500 mg / m 2 or less.
The undercoat layer according to claim 6, wherein the basis weight is 300 mg / m 2 or less.
The undercoat layer according to claim 7, wherein the basis weight is 200 mg / m 2 or less.
A composite current collector for an electrode of an energy storage device, comprising the undercoat layer according to any one of claims 4 to 8.
An electrode for an energy storage device comprising the composite current collector for an electrode of the energy storage device according to claim 9.
An energy storage device comprising the electrode for an energy storage device according to claim 10.
The energy storage device according to claim 11, wherein the energy storage device is a lithium ion secondary battery.