Carbon nanotube dispersion composition, composite slurry, electrode film, and secondary battery

Abstract

A carbon nanotube dispersion composition which contains carbon nanotubes (A), a dispersant (B), and a solvent (C), has a particle diameter D50 of 0.3-7 [mu] m at a volume accumulation of 50% as determined by laser diffraction particle size distribution measurement, and satisfies (1) and (2). (1) The dispersant (B) is a polymer having a weight average molecular weight of 5,000-360,000 and having a carboxyl group-containing structural unit, the carboxyl group-containing structural unit is derived from at least one of (meth) acrylic acid and a carboxyl group-containing (meth) acrylic acid ester, and the content of the carboxyl group-containing structural unit is 80 mass% or more based on the mass of the polymer. (2) when the particle diameter D50 of the carbon nanotube dispersion composition at a volume accumulation of 50% as determined by laser diffraction particle size distribution measurement is X [[mu] m] and the pH is Y, X and Y satisfy formula a and formula b. (formula a) Y is greater than or equal to-0.149 X + 4.545; (Formula b) Y < =-0.134 X + 5.140.

Description

Technical Field

[0001] The present disclosure relates to a carbon nanotube dispersion composition, and more particularly, to a carbon nanotube dispersion composition, a composite material slurry comprising the carbon nanotube dispersion composition and an active material, an electrode film formed from the composite material slurry, and a secondary battery comprising the electrode film. Background Art

[0002] With the popularization of electric vehicles, the miniaturization, lightness and high performance of portable devices, secondary batteries with high energy density and high capacity of the secondary batteries are sought. In this context, secondary batteries using non-aqueous electrolytes, especially lithium-ion secondary batteries, are used in a large number of devices due to their high energy density and high voltage characteristics.

[0003] The capacity of lithium-ion secondary batteries largely depends on the positive electrode active material and the negative electrode active material as main materials, and therefore various materials used for these electrode active materials are being actively studied.

[0004] However, when using practical electrode active materials, the obtained charging capacity is close to the theoretical value, and the improvement of electrode active materials is close to the limit. Under such circumstances, for negative electrode active materials, silicon-based active materials that can reversibly dope more lithium ions into existing graphite powder are expected. However, when using silicon-based active materials, there are the following problems: due to the volume change when absorbing and releasing lithium ions during charging and discharging, it is easy to cause cracks or isolation of particles, and the capacity decreases with repeated charging and discharging.

[0005] In addition, in order to improve the conductivity of the electrode, the technology of using carbon nanotubes as a conductive material is being studied. By using carbon nanotubes, it is expected that the electrode resistance can be reduced. Among them, when carbon nanotubes are used for the negative electrode, the following effects can be expected: preventing the silicon-based active material with low conductivity from being electrically isolated due to the volume change when absorbing and releasing lithium ions during charging and discharging, and improving the life of the battery.

[0006] In recent years, the mainstream method of adding carbon nanotubes to composite material slurry for secondary batteries is to use a carbon nanotube dispersion. By setting the dispersed particle size of such a carbon nanotube dispersion to an appropriate range, a conductive path can be laid between active materials storing lithium ions.

[0007] Therefore, for example, Patent Document 1 discloses a method of preparing a sodium carboxymethylcellulose aqueous dispersion of multi-walled carbon nanotubes having an average fiber outer diameter in the range of 50 nm to 110 nm, wherein the carbon nanotube dispersion is stabilized by a specific particle size distribution characteristic to improve conductivity and thus enhance cycle characteristics when a secondary battery is made.

[0008] Patent Document 2 discloses a method for providing a carbon nanotube dispersion, wherein the carbon nanotube dispersion contains 2 wt % to 15 wt % of a Brunauer-Emmett-Teller (BET) specific surface area value of 70 m 2 / g~250m 2 / g of carbon nanotube powder dispersion, and adjusted to a temperature of 25°C and a shear rate of 383s -1 The viscosity value is 2 mPa·s to 110 mPa·s, and the dispersed particle diameter d50 is 100 nm to 600 nm, and the cycle characteristics are excellent.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2016-028109

[0012] Patent Document 2: Japanese Patent Application Publication No. 2015-195143 Summary of the invention

[0013] Problems to be solved by the invention

[0014] According to these methods, localization of the conductive material in the electrode due to entanglement of carbon nanotubes can be suppressed, and the conductive path can be maintained to improve the cycle characteristics.

[0015] However, carbon nanotubes are usually formed into aggregates by winding carbon fibers with nanometer-sized outer diameters. Since it is very difficult to disintegrate and disperse the aggregates, it is difficult to obtain a carbon nanotube dispersion composition with high initial fluidity and excellent dispersion stability. In addition, when using a carbon nanotube dispersion composition with poor fluidity, in the composite material slurry obtained by further adding active substances, the diffusion of the conductive material becomes insufficient, and when forming a coating film, the internal resistance at a high rate rises, and the rate characteristics become a problem.

[0016] Therefore, the present invention provides a carbon nanotube dispersion composition having good cycle characteristics when used in a secondary battery, that is, the dispersion composition has both fluidity and storage stability within a particle size range that allows the dispersion of carbon nanotubes with excellent life performance. In addition, a secondary battery is provided that has both cycle characteristics and rate characteristics by using the carbon nanotube dispersion composition.

[0017] Furthermore, the present invention provides a secondary battery having excellent rate characteristics even when graphite powder and a silicon-based active material are used as negative electrode active materials.

[0018] Technical means of solving problems

[0019] That is, the present invention includes the following embodiments. The embodiments of the present invention are not limited to the following.

[0020] One embodiment relates to a carbon nanotube dispersion composition, characterized in that it comprises carbon nanotubes (A), a dispersant (B) and a solvent (C), wherein the particle size D at the volume accumulation of 50% obtained by laser diffraction particle size distribution measurement is 50 The carbon nanotube dispersion composition has a particle size of 0.3 μm to 7 μm, and satisfies the following (1) and (2).

[0021] (1) the dispersant (B) is a polymer having a weight average molecular weight of 5,000 or more and 360,000 or less and having a carboxyl group-containing structural unit derived from at least one of (meth)acrylic acid and a (meth)acrylate having a carboxyl group,

[0022] The content of the carboxyl group-containing structural unit is 80% by mass or more based on the mass of the polymer.

[0023] (2) When the particle size D of the carbon nanotube dispersion composition at the time of volume accumulation of 50% is obtained by laser diffraction particle size distribution measurement, 50 When ρ is X [μm] and pH is Y, X and Y satisfy the following (Formula a) and (Formula b).

[0024] (Formula a) Y≧-0.149X+4.545

[0025] (Formula b) Y ≦ -0.134X + 5.140

[0026] In the above embodiment, the carbon nanotube dispersion composition preferably further contains a basic compound (D).

[0027] Another embodiment relates to a composite material slurry, which includes the carbon nanotube dispersion composition of the embodiment and an active substance.

[0028] Another embodiment relates to an electrode membrane formed from the composite material slurry of the above embodiment.

[0029] Another embodiment relates to a secondary battery comprising a positive electrode and a negative electrode, wherein:

[0030] At least one of the positive electrode and the negative electrode includes the electrode film of the above-described embodiment.

[0031] Effects of the Invention

[0032] According to an embodiment of the present invention, in particular, in a carbon nanotube dispersion composition having a particle size distribution range that is expected to improve the life performance of a secondary battery, excellent fluidity and storage stability can be provided. In addition, a secondary battery can be provided that takes into account both cycle characteristics and rate characteristics by using the carbon nanotube dispersion composition.

[0033] Furthermore, when graphite powder and silicon-based active materials are used as negative electrode active materials, even if the active materials expand and contract during charge and discharge, the carbon nanotubes are evenly diffused in the composite slurry to fully maintain the conductive path, thereby suppressing the increase in internal resistance in the electrode and suppressing the decrease in charge and discharge capacity, thereby providing a secondary battery with excellent rate characteristics. DETAILED DESCRIPTION

[0034] Hereinafter, the dispersion composition, composite material slurry, electrode film, and secondary battery as embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and the present invention also includes embodiments implemented within the scope of the gist.

[0035] In the present specification, a numerical range defined by using “to” means a range including the numerical values ​​described before and after “to” as the lower limit and the upper limit.

[0036] In this specification, “carbon nanotube” may be referred to as “CNT”, “carbon nanotube dispersion composition” may be referred to as “dispersion composition” or “CNT dispersion composition”, and “particle size D at 50% volume accumulation based on laser diffraction particle size distribution measurement” may be referred to as “CNT”. 50 ” is called “particle size D 50 ”.

[0037] In the present specification, when expressed as “(meth)acrylic group”, “(meth)acryloyl group”, “(meth)acrylic acid”, “(meth)acrylate”, or “(meth)acryloyloxy group”, they respectively mean “acrylic group or methacrylic group”, “acryloyl group or methacryloyl group”, “acrylic acid group or methacrylic acid group”, “acrylate group or methacrylate group”, or “acryloyloxy group or methacryloyloxy group”, unless otherwise specified.

[0038] Unless otherwise specified, various components described in the present specification may be used alone or in combination of two or more.

[0039] The numerical values ​​defined in this specification are values ​​obtained by the methods disclosed in the embodiments or examples.

[0040] <1> Carbon nanotube dispersion composition

[0041] The carbon nanotube dispersion composition of this embodiment comprises carbon nanotubes (A), a dispersant (B) and a solvent (C).

[0042] Particle diameter D at volume accumulation 50% obtained by laser diffraction particle size distribution measurement 50 The carbon nanotube dispersion composition has a particle size of 0.3 μm to 7 μm, and satisfies the following (1) and (2).

[0043] (1) the dispersant (B) is a polymer having a weight average molecular weight of 5,000 or more and 360,000 or less and having a carboxyl group-containing structural unit derived from at least one of (meth)acrylic acid and a (meth)acrylate having a carboxyl group,

[0044] The content of the carboxyl group-containing structural unit is 80% by mass or more based on the mass of the polymer.

[0045] (2) When the particle size D of the carbon nanotube dispersion composition at the time of volume accumulation of 50% is obtained by laser diffraction particle size distribution measurement, 50 When ρ is X [μm] and pH is Y, X and Y satisfy the following (Formula a) and (Formula b).

[0046] (Formula a) Y≧-0.149X+4.545

[0047] (Formula b) Y ≦ -0.134X + 5.140

[0048] As described above, the present inventors have found that the preferred range of pH of the carbon nanotube dispersion composition depends on the particle size D 50 For example, the particle size D 50 The larger the value of is, the lower the pH is adjusted, thereby improving the storage stability and fluidity.

[0049] In the carbon nanotube dispersion composition of the present embodiment, the dispersed particle size is the particle size D at the time of volume accumulation 50% obtained by laser diffraction particle size distribution measurement. 50 The particle size distribution of the carbon nanotube dispersion composition is 0.3 μm to 7 μm. The carbon nanotube dispersion composition having such a particle size distribution range tends to be able to easily provide a secondary battery with excellent cycle characteristics. 50 It is preferably 0.35 μm or more, and more preferably 0.4 μm or more. 50 It is preferably 6 μm or less, more preferably 5.5 μm or less, and still more preferably 5 μm or less.

[0050] Particle size D 50 The particle size D is related to the length of the carbon nanotubes in the dispersed composition. 50The carbon nanotube dispersion composition (hereinafter also referred to as the dispersion composition) within the above range has a good dispersion state of the carbon nanotubes in the dispersion composition, excellent cycle characteristics, and is likely to extend the battery life. 50 When the above range is exceeded, there are carbon nanotubes in an aggregated state. 50 If the ratio is below the above range, a large number of finely cut conductive materials are generated, and thus it tends to be difficult to form an efficient conductive network.

[0051] The particle size D 50 The particle size distribution can be determined using a laser diffraction particle size distribution analyzer using a common dynamic light scattering method, and more specifically, can be measured by the method described in the Examples.

[0052] The pH of the carbon nanotube dispersion composition of the present embodiment is within the range of "Y" specified by (Formula a) and (Formula a). The pH may be a value measured at 25°C using, for example, a pH meter. In some embodiments, when measured at 25°C using a pH meter, the pH of the carbon nanotube dispersion composition is preferably within the range of 3.5 to 5.1, more preferably within the range of 3.8 to 5.0. If the pH is within the range, the dispersibility of the dispersant (B) can be easily improved, thereby tending to easily improve the fluidity and dispersion stability of the dispersion composition.

[0053] As described above, the carbon nanotube dispersion composition of the present embodiment is a dispersion composition adjusted to a particle size distribution range of a secondary battery with excellent cycle characteristics, and by using a dispersant (B) having a sufficient carboxyl group and adjusting the pH of the dispersion composition to a specific range, excellent fluidity and storage stability are achieved. Furthermore, when an active material is added to the dispersion composition to form a composite material slurry, the capacity retention rate can be suppressed by uniformly distributing the carbon nanotubes relative to the active material.

[0054] In order to obtain the carbon nanotube dispersion composition of the present embodiment, it is preferred to apply a pH adjustment method to satisfy the range of "Y" specified by (Formula a) and (Formula b). The pH adjustment method is not particularly limited. For example, there can be cited a method of adding a basic compound to the dispersion composition and adjusting the amount thereof added; or a method of using carbon nanotubes that exhibit acidity or alkalinity. Carbon nanotubes that exhibit acidity can be obtained, for example, by the following method: a method of introducing an acidic functional group into the carbon nanotube by acid treatment or the like. Carbon nanotubes that exhibit alkalinity can be obtained, for example, by the following method: a method of adjusting the amount of metal derived from a catalyst remaining in the carbon nanotube; a method of pretreating the carbon nanotube using a basic compound (for example, a compound containing an alkali metal or an alkaline earth metal, an amine compound, etc.).

[0055] In some embodiments, from the viewpoint of easy adjustment of pH, a method using a basic compound is preferred, and a method of adding a basic compound to the dispersion composition is more preferred. By adjusting the amount of the basic compound added, the desired pH value can be easily obtained. The details of the basic compound will be described below in the form of "basic compound (D)".

[0056] In the dispersion composition of the present embodiment, the dispersant (B) contains more than 80% by mass of the carboxyl-containing structural unit. Therefore, the pH of the solution obtained by dissolving in a solvent (e.g., water, etc.) in which the dispersant (B) can be dissolved shows acidity. More specifically, the pH value of the solution containing the dispersant (B) can be more than 2 and less than 7. COO is generated by adjusting the pH of the solution containing the dispersant (B). - The present inventors have found that in a carbon nanotube dispersion composition, the particle size D at the time of volume accumulation 50% obtained by laser diffraction particle size distribution measurement is the dispersed particle size. 50 By controlling the relationship with pH, ​​the initial viscosity of the dispersion composition can be reduced, and the fluidity and dispersion stability of the dispersion composition can be achieved at the same time.

[0057] Although not limited by theory, about the particle size D 50 The relationship with pH has a preferred range defined by the above formula (Formula a) and (Formula b), and the following reasons are considered.

[0058] First, the smaller the dispersed particle size, the faster the collision speed of particles due to Brownian motion. Therefore, it is speculated that more COO-based - In other words, for example, when a basic compound is used to adjust the pH, the smaller the dispersed particle size, the more basic compound needs to be added, and as a result, the pH tends to increase. In addition, in order to stabilize the dispersion, when the dispersed particle size is large, it is also necessary to add a COO-based - The electric repulsion of the base is above a certain level.

[0059] On the other hand, carboxyl has high affinity for carbon nanotube (Carbon Nano Tube, CNT), so dispersants containing a large amount of carboxyl are easily adsorbed by CNT. For example, if pH becomes too high due to excessive addition of alkaline compounds to the dispersion composition, the amount of carboxyl is relatively reduced, and the dispersant is worried about being separated from CNT. In particular, when the dispersed particle size is large, the mass of the CNT particles in the dispersion composition becomes large, so it is preferred that pH is set low. Considering that pH is appropriately adjusted according to the size of the dispersed particle size as described above, the adsorption of dispersant for carbon nanotubes is improved, and thus the particle repulsion based on the osmotic pressure effect can be utilized, as a result of these, storage stability and fluidity can be improved.

[0060] In addition, the carbon nanotube dispersion composition of the present embodiment does not contain an active material. In this specification, when the carbon nanotube dispersion composition further contains an active material, it is defined as a composite material slurry.

[0061] That is, the dispersion composition of the present embodiment refers to the state before the active substance is added to the dispersion composition. In these respects, the dispersion composition is different from the composite material slurry containing the active substance. That is, the dispersion composition does not substantially contain the active substance. The so-called "substantially does not contain" is a concept other than the state of intentionally adding the active substance to the dispersion composition. Specifically, relative to the gross mass of the dispersion composition, the content of the active substance can be as long as it is less than 1 mass %, less than 0.5 mass % or less than 0.1 mass %, or can be 0 mass %. The details of the active substance will be described below.

[0062] The dispersed composition of the present embodiment can be preferably used to form an electrode for a secondary battery. However, the dispersed composition of the present embodiment is not limited to the use of a secondary battery, and can also be used for storage devices other than secondary batteries, such as electrodes for electric double-layer capacitors, electrodes for non-aqueous electrolyte capacitors, etc. In addition, it can also be used for antistatic materials such as integrated circuit (IC) trays of plastic and rubber products, molded bodies of electronic parts materials, electronic parts, transparent electrodes (indium tin oxide (Indium Tin Oxide, ITO) film) substitutes, electromagnetic wave shielding materials, etc.

[0063] Hereinafter, the constituent components of the carbon nanotube dispersion composition according to the present embodiment will be described.

[0064] <Carbon nanotubes (A)>

[0065] The carbon nanotubes may be single-layer carbon nanotubes alone, multi-layer carbon nanotubes alone, or a mixture of single-layer carbon nanotubes and multi-layer carbon nanotubes. Single-layer carbon nanotubes have a structure in which one layer of graphite is wound, and multi-layer carbon nanotubes have a structure in which two or more layers of graphite are wound.

[0066] The average outer diameter of the carbon nanotubes used as raw materials is preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 40 nm or less, or more preferably 1 nm or more and 20 nm or less. If it is within these ranges, the packing density of the active material can be further increased in the electrode film. By using the carbon nanotubes in the range, a bundle comprising multiple CNTs can be formed in the dispersed composition, and a dispersed composition having the preferred average outer diameter after dispersion is obtained.

[0067] The average outer diameter of the carbon nanotubes used as a raw material is calculated by the following method.

[0068] First, the carbon nanotubes were dispersed in toluene using an ultrasonic homogenizer, and then placed on a collodion film and dried. The dried carbon nanotubes were observed and photographed using a transmission electron microscope (TEM). Next, 100 carbon nanotubes were randomly selected from the observation photos and their outer diameters were measured. Next, the average outer diameter (nm) of the raw carbon nanotubes was calculated as the number average of the outer diameters.

[0069] The average fiber length of the carbon nanotubes used as a raw material is preferably 1 μm to 50 μm, more preferably 1 μm to 20 μm. Within this range, it is easy to adjust to a preferred fiber length after dispersion.

[0070] The average fiber length of the carbon nanotubes used as raw materials can be measured as follows: the carbon nanotubes are dispersed in toluene using an ultrasonic homogenizer, and then the carbon nanotubes deposited on the mica substrate are observed by a scanning electron microscope (SEM) and image analysis is performed. The SEM image is analyzed using the image analysis software "WinROOF2015" (manufactured by Mitani Shoji), and the skeleton length is calculated as the fiber length for one carbon nanotube. The average value obtained by counting the fiber lengths of 1000 to 3000 carbon nanotubes is set as the average fiber length of the carbon nanotubes used as raw materials.

[0071] The BET specific surface area of ​​the carbon nanotubes used as a raw material measured by nitrogen adsorption is preferably 100 m 2 / g and above 1200m 2When the BET specific surface area of ​​the carbon nanotubes is within the above range, the carbon nanotubes can be easily distributed in the composite material slurry when controlled to an appropriate dispersion state, and the cycle performance can be further improved.

[0072] Regarding the carbon nanotubes used as raw materials, when the Raman spectrum is set at 1560 cm -1 ~1600cm -1 The maximum peak intensity in the range of G, 1310cm -1 ~1350cm -1 When the maximum peak intensity in the range of is D, the G / D ratio is preferably 0.5 or more and 100 or less, more preferably 0.8 or more and 50 or less, and further preferably 1 or more and 45 or less.

[0073] Among them, the specific surface area is 100m 2 / g or more and less than 700m 2 In the case of 1.5 g / g, the G / D ratio is preferably 0.8 to 8, more preferably 0.8 to 5.

[0074] The specific surface area is 700m 2 / g and above 1200m 2 When the G / D ratio is 30 or more and 100 or less, the G / D ratio is preferably 40 or more and 50 or less.

[0075] If the G / D ratio of the carbon nanotube is within the range, the crystallinity is high and good conductivity is easily obtained, so it is preferred. The reason why the preferred range is different according to the specific surface area is that when the specific surface area is small, it is mainly multilayer CNT, and the D band becomes stronger due to the influence of the terminal sp3 mixed carbon or the interlayer, so the G / D ratio range with good conductivity becomes smaller relative to the high specific surface area carbon nanotube. In the case of high specific surface area, it is mainly single-layer CNT, and the defect of sp2 carbon can be inferred by the G / D ratio. If it is within the range, there are few defects and good conductivity can be shown.

[0076] The volume resistivity of the carbon nanotubes used as the raw material is preferably 1.0×10 -3 Ω·cm or more and 3.0×10 -2 Ω·cm or less, more preferably 1.0×10 -3 Ω·cm or more and 1.0×10 -2 Ω·cm or less.

[0077] The volume resistivity of the carbon nanotubes can be measured using a powder resistivity measuring device (Mitsubishi Chemical Analytech Co., Ltd.: Loresta GP Powder Resistivity Measuring System MCP-PD-51). If the volume resistivity of the carbon nanotubes is within the above range, the electron transfer resistance between the carbon nanotubes and the active material can be reduced.

[0078] The carbon purity of the carbon nanotubes used as a raw material is represented by the content (%) of carbon atoms in the carbon nanotubes. The carbon purity is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more relative to 100% by mass of the carbon nanotubes. If the carbon purity of the carbon nanotubes is within the above range, it is possible to prevent the formation of dendrites due to impurities such as metal catalysts and the generation of short circuits and other undesirable conditions.

[0079] The amount of metal contained in the carbon nanotubes used as a raw material is preferably less than 20% by mass, more preferably less than 10% by mass, and further preferably less than 5% by mass relative to 100% by mass of the carbon nanotubes. Examples of the metal contained in the carbon nanotubes include metals or metal oxides used as catalysts when synthesizing carbon nanotubes, or metal powders mixed in due to wear of an apparatus, etc. Specifically, examples include metals such as cobalt, nickel, aluminum, magnesium, silicon dioxide, manganese, or molybdenum, alloys of these metals, metal oxides, and composite oxides of these metals.

[0080] The carbon purity and metal content in the carbon nanotubes can be determined by inductively coupled plasma (ICP) emission spectrometry.

[0081] The carbon nanotubes used as raw materials may be surface-treated carbon nanotubes, carbon nanotube derivatives to which functional groups represented by carboxyl groups are added, or carbon nanotubes containing organic compounds, metal atoms, and the like may be used.

[0082] The carbon nanotubes used as raw materials may also be carbon nanotubes that have been subjected to a pulverization treatment. The so-called pulverization treatment is a process of pulverizing carbon nanotubes substantially without the presence of a liquid substance, using a pulverizer equipped with pulverizing media such as beads or stainless steel balls, and is also called dry pulverization. The pulverization is carried out by utilizing the pulverizing force or destructive force generated by the collision of pulverizing media with each other. The pulverization mainly has the effect of reducing the secondary particles of the carbon nanotubes and can improve the dispersibility of the carbon nanotubes. As a dry pulverization device, a known method such as a dry grinder, a ball mill, a vibration mill, a bead mill, etc. can be used, and the pulverization time can be arbitrarily set according to the device.

[0083] The carbon nanotubes used as the raw material may be carbon nanotubes produced by any method. Carbon nanotubes can be produced generally by laser ablation, arc discharge, thermal chemical vapor deposition (CVD), plasma CVD, and combustion, but are not limited thereto.

[0084] <Dispersant (B)>

[0085] The carbon nanotube dispersion composition of the present embodiment contains a dispersant (B). The dispersant has a function of stabilizing the dispersion of CNTs in the dispersion composition, and other dispersants may be used in combination within a range that does not inhibit the effect.

[0086] The dispersant (B) is a polymer having a weight average molecular weight of 5,000 to 360,000 and having a carboxyl group-containing structural unit, wherein the content of the carboxyl group-containing structural unit is 80% by mass or more based on the mass of the polymer.

[0087] By using such a dispersant (B) to disperse carbon nanotubes, it is possible to easily obtain a particle size D that satisfies a specific requirement. 50 The present invention provides a carbon nanotube dispersion composition having excellent fluidity and storage stability.

[0088] The weight average molecular weight of the dispersant (B) is 5,000 or more and 360,000 or less. The weight average molecular weight of the dispersant (B) is preferably 6,000 or more, more preferably 8,000 or more. Also, it is preferably 260,000 or less, more preferably 100,000 or less.

[0089] In some embodiments, the weight average molecular weight of the dispersant (B) is preferably 9,000 or more, more preferably 10,000 or more, and even more preferably 50,000 or more. In addition, the weight average molecular weight of the dispersant (B) is preferably 90,000 or less, more preferably 80,000 or less, and even more preferably 70,000.

[0090] When the weight average molecular weight is within the above range, the adsorption property to carbon nanotubes is improved, and the stability of the dispersion can be further improved.

[0091] The dispersant (B) is a polymer having a carboxyl group-containing structural unit, and the content of the carboxyl group-containing structural unit is 80% by mass or more based on the mass of the polymer.

[0092] The presence of sufficient carboxyl groups in the molecule provides strong ionicity, thereby increasing the adsorption of carbon nanotubes and the affinity for the medium, allowing the carbon nanotubes to exist stably in the medium.

[0093] In some embodiments, the dispersant (B) is preferably a polymer of at least one of (meth)acrylic acid and (meth)acrylate having a carboxyl group. That is, the dispersant (B) is preferably a polymer containing a structural unit derived from at least one of (meth)acrylic acid and (meth)acrylate having a carboxyl group, and more preferably a polymer containing a structural unit derived from (meth)acrylic acid. When the polymer is used as the dispersant (B), the dispersibility of the carbon nanotubes is excellent, and as a battery material, the rate characteristics and cycle characteristics are easily further improved.

[0094] Furthermore, the dispersant (B) is preferably a polymer having an alkylene structure in the main chain.

[0095] In this specification, the content of each structural unit of the dispersant can be calculated based on the mass % of the precursor (monomer) used during polymerization. Therefore, the content of the structural unit containing a carboxyl group described below refers to the content of (meth) acrylic acid and / or (meth) acrylic acid ester having a carboxyl group based on the total amount of monomers used to manufacture the dispersant (polymer).

[0096] With regard to the viewpoint of having appropriate affinity with the solvent described later, when the mass of polymer (wherein, except initiator and chain-transfer agent) is set to 100 mass %, the containing ratio of carboxyl structural unit is preferably more than 90 mass %, more preferably more than 95 mass %.On the other hand, the containing ratio can also be less than 98 mass %.In one embodiment, the containing ratio can be 100 mass %.By being more than 90 mass %, it is possible to further expect the dispersion stabilization of the CNT brought by the electric repulsion of carboxyl.

[0097] In one embodiment, the dispersant (B) may contain at least one selected from the group consisting of a nitrile-containing structural unit, a hydroxyl-containing structural unit, and a heterocyclic-containing structural unit in addition to the carboxyl-containing structural unit. When the dispersant (B) contains at least one structural unit in addition to the carboxyl-containing structural unit as described above, polarization becomes stronger and the affinity of the carbon nanotubes to the medium becomes higher, which is preferred.

[0098] [Carboxyl group-containing structural unit]

[0099] The carboxyl-containing structural unit is a structural unit having a carboxyl group, and may be a structural unit having an alkylene structure substituted with a carboxyl group. The alkylene structure is preferably a linear or branched alkylene structure. The number of carboxyl groups possessed by the carboxyl-containing structural unit is preferably one or two, more preferably one.

[0100] The method of introducing a carboxyl-containing structural unit into a polymer is not particularly limited. For example, a method of preparing a polymer by polymerization of a monomer having a carboxyl group, more specifically (meth) acrylic acid or a (meth) acrylate having a carboxyl group, etc. can be cited. As another method, a method of preparing a polymer by polymerization of a monomer containing a functional group other than a carboxyl group, and then modifying the functional group to a carboxyl group can be cited. In particular, a method of preparing a polymer by polymerization of a monomer having a carboxyl group can be preferably used.

[0101] Examples of monomers having a carboxyl group include unsaturated fatty acids such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, ethylene oxide-modified succinic acid (meth)acrylate, and (meth)acrylic acid β-ethyl ester, etc. In addition, monomers having anhydride groups such as maleic anhydride, itaconic anhydride, and citraconic anhydride, and their monofunctional alcohol adducts, which are polymers of the monomers having a carboxyl group, may be cited.

[0102] "-C(=O)-OC(=O)-" (referred to as "anhydride group" in this specification), which is a group having a structure formed by dehydration condensation of two carboxyl groups, also forms a carboxyl group by hydrolysis. Therefore, in this specification, it is included in the concept of a carboxyl group. In addition, a carboxyl group-containing structural unit can also be prepared by hydrolyzing the carbamoyl group of a polymer obtained by polymerization reaction of a monomer having a carbamoyl group such as (meth)acrylamide.

[0103] The monomer having a carboxyl group as a precursor of the carboxyl group-containing structural unit is preferably an unsaturated fatty acid from the viewpoint of electrochemical stability, more preferably (meth) acrylic acid, and further preferably acrylic acid. Acrylic acid is excellent in solubility in water and dispersibility of carbon nanotubes, and as a battery material, it can further improve rate characteristics and cycle characteristics, so it is preferred.

[0104] [Structural unit containing a nitrile group]

[0105] The nitrile group-containing structural unit is a structural unit having a nitrile group, and may be a structural unit having an alkylene structure substituted with a nitrile group.

[0106] The alkylene structure is preferably a linear or branched alkylene structure. The number of nitrile groups in the nitrile group-containing structural unit is preferably one or two, more preferably one.

[0107] The method for introducing the structural unit containing a nitrile group into the dispersant is not particularly limited. In one embodiment, for example, a polymer can be prepared by a polymerization reaction of a monomer having a nitrile group.

[0108] As the monomer having a nitrile group, for example, acrylonitrile, methacrylonitrile, fumaronitrile, etc. can be cited. One of these can be used alone, or two or more can be used in combination. In the case where the monomer having a nitrile group is acrylonitrile, the bending of the copolymer becomes less, and the adjacent cyano groups are oriented to form a strongly polarized partial structure. Therefore, the intermolecular force between polymers or between polymers and carbon-based conductive materials becomes higher. From the perspective of improving the intermolecular force as described above, and the ease of obtaining raw materials and the reactivity, the monomer having a nitrile group is preferably acrylonitrile.

[0109] From the viewpoint of improving the intermolecular force, when the mass of the polymer is set to 100 mass %, the content of the structural unit containing the nitrile group is preferably 3 mass % or more, more preferably 5 mass % or more. On the other hand, it is preferably 20 mass % or less, more preferably 10 mass % or less.

[0110] By adjusting the content of the structural unit containing the nitrile group to the above range, the carbon nanotubes can be more stably present in the medium. In addition, when such a polymer is used in a secondary battery, it is preferred to prevent the dispersant from dissolving in the electrolyte in the battery and increasing the resistance of the electrolyte.

[0111] [Hydroxy-containing structural unit]

[0112] The hydroxyl-containing structural unit is a structural unit having a hydroxyl group, and may be a structural unit having an alkylene structure substituted with a hydroxyl group. The alkylene structure is preferably a linear or branched alkylene structure. The number of hydroxyl groups possessed by the hydroxyl-containing structural unit is preferably one or two, more preferably one.

[0113] The method of introducing a hydroxyl-containing structural unit into a polymer is not particularly limited. For example, a method of preparing a polymer by a polymerization reaction of a monomer having a hydroxyl group, or a method of preparing a polymer by a polymerization reaction of a monomer having a functional group other than a hydroxyl group and modifying it to a hydroxyl group can be cited. From the viewpoint of reactivity and raw material price, a reasonable method can be selected.

[0114] Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyvinylbenzene, 2-hydroxy-3-phenoxypropyl acrylate, or caprolactone adducts of these monomers (addition mole number is 1 to 5). The monomer containing a hydroxyl group is preferably a hydroxyalkyl (meth)acrylate, more preferably 2-hydroxyethyl (meth)acrylate, and still more preferably 2-hydroxyethyl acrylate.

[0115] As a method of preparing a polymer by polymerization reaction of a monomer having a functional group other than a hydroxyl group and modifying it to a hydroxyl group, for example, there is a method (saponification reaction) in which the acetyl group of polyvinyl acetate obtained by polymerizing vinyl acetate is saponified with a base such as sodium hydroxide to convert it to a hydroxyl group. The reaction rate (saponification degree) of the saponification can be arbitrarily controlled by changing the concentration of sodium hydroxide and the treatment time.

[0116] In order to improve the affinity between the carbon nanotubes and the medium, at least a part of the hydroxyl groups in the polymer may be reacted with an aldehyde compound and modified into acetal groups before use (acetalization).

[0117] The aldehyde compound used in the acetalization reaction can be, for example, a linear, branched, cyclic saturated, unsaturated or aromatic aldehyde compound having 1 to 15 carbon atoms, but is not limited to these. Specifically, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, tert-butyraldehyde, benzaldehyde and cyclohexanal can be mentioned. These aldehyde compounds can be used alone or in combination of two or more. In addition, these aldehyde compounds, in addition to formaldehyde, can also be aldehyde compounds in which one or more hydrogen atoms are substituted by halogens or the like. From the perspective of versatility, compounds such as linear, branched, cyclic saturated, unsaturated or aromatic aldehydes having 1 to 10 carbon atoms are preferred, and linear aldehyde compounds having 1 to 4 carbon atoms are more preferred. By changing the aldehyde compound used and the treatment time, the reaction rate (acetalization degree) of acetalization can be arbitrarily controlled.

[0118] From the viewpoint of enhancing polarization and improving affinity for carbon nanotubes and media and resistance to electrolyte, the content of the hydroxyl-containing structural unit is preferably 3% by mass or more, more preferably 5% by mass or more, when the mass of the polymer is 100% by mass. On the other hand, it is preferably 20% by mass or less, more preferably 10% by mass or less.

[0119] In addition, when the structural unit containing hydroxyl group is acetalized to have an acetal group, for the same reason, when the mass of the polymer is set to 100 mass %, the content of the structural unit containing the acetal group is preferably 3 mass % or more, more preferably 5 mass % or more. On the other hand, it is preferably 20 mass % or less, more preferably 10 mass % or less.

[0120] Furthermore, in the case of containing one or more selected from the group consisting of a nitrile-containing structural unit and a heterocyclic-containing structural unit, the content of the hydroxyl-containing structural unit is preferably 1% by mass or more, more preferably 3% by mass or more. On the other hand, it is preferably 10% by mass or less, more preferably 5% by mass or less. By adjusting to the above range, polarization can be enhanced and affinity for carbon nanotubes and media can be improved. In addition, it is also preferred from the viewpoint of resistance to electrolyte.

[0121] It is particularly preferred that at least one selected from the group consisting of a nitrile group-containing structural unit and a heterocyclic ring-containing structural unit is further contained because polarization becomes stronger.

[0122] [Structural unit containing a heterocyclic ring]

[0123] The heterocyclic structural unit is a structural unit having a heterocyclic ring, and may be a structural unit having an alkylene structure substituted by a substituent containing a heterocyclic ring. The alkylene structure is preferably a linear or branched alkylene structure. The heterocyclic ring contained in the heterocyclic structural unit may be a monocyclic structure or a condensed ring structure, but is preferably a monocyclic structure. In addition, the number of heterocyclic rings in the heterocyclic structural unit is preferably one or two, and more preferably one.

[0124] The heterocyclic ring contains atoms other than carbon in the atoms constituting the ring, for example, one or more nitrogen atoms, oxygen atoms, sulfur atoms, etc. As the atoms other than carbon constituting the ring, nitrogen atoms or oxygen atoms are preferred, and nitrogen atoms are more preferred. By including atoms other than carbon in the atoms constituting the ring, polarization is generated in the heterocyclic ring, which can strongly act on the carbon nanotubes.

[0125] The method for introducing a heterocyclic ring into a polymer is not particularly limited, and for example, a method for producing a polymer by a polymerization reaction of a monomer having a heterocyclic ring can be used.

[0126] As a monomer having a heterocyclic ring, an N-vinyl cyclic amide structural unit is preferred, for example, N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazine-2-one, N-vinyl-3,5-morpholinedione, etc. In particular, from the perspective of improving battery characteristics, N-vinyl-2-pyrrolidone is preferred. In addition, these can be used alone or in combination of two or more.

[0127] When the mass of the polymer is set to 100 mass%, from the viewpoint of enhancing polarization and improving the effect on carbon nanotubes as described above, the content of the heterocyclic structural unit is preferably 3 mass% or more, more preferably 5 mass% or more. On the other hand, it is preferably 20 mass% or less, more preferably 15 mass% or less.

[0128] Wherein, also contain the structural unit containing nitrile group and the structural unit containing hydroxyl group under the situation of at least any one, based on the mass of polymer, the containing ratio of the structural unit containing heterocycle is preferably more than 1 mass %, more preferably more than 3 mass %.On the other hand, preferably below 20 mass %, more preferably below 15 mass %.

[0129] In the case where at least any one of a nitrile group-containing structural unit and a hydroxyl group-containing structural unit is further contained, the polarity becomes higher and the resistance to the electrolyte solution can be improved, which is more preferable.

[0130] [Other structural units]

[0131] The polymer may also have one or more structural units selected from the group consisting of structural units containing active hydrogen groups (except carboxyl groups and hydroxyl groups), structural units containing basic groups, and structural units containing ester groups as other structural units. By selecting the structural units to contain in combination with the hydrophilicity, hydrophobicity, acidity, and alkalinity of the base material or the mixed material used as the carbon nanotube dispersion composition of this embodiment, it can be easily applied to various uses.

[0132] When the mass of the polymer is 100 mass %, the content of other structural units is preferably 20 mass % or less, more preferably 10 mass % or less, and further preferably 5 mass % or less from the viewpoint of not impairing the polarizability of the dispersant.

[0133] The active hydrogen group-containing structural unit is a structural unit having an active hydrogen group such as a primary amino group, a secondary amino group, a thiol group, etc. Here, the so-called "primary amino group" refers to -NH2 (amino group), and the so-called "secondary amino group" refers to a group formed by replacing a hydrogen atom on a primary amino group with an organic residue such as an alkyl group. However, in this specification, the primary amino group and the secondary amino group in the acid amide are not included in the active hydrogen group.

[0134] The basic group-containing structural unit is a structural unit having a basic group. Examples of the basic group include a tertiary amino group, an amide group, and the like. In addition, a structural unit having a primary amino group and a structural unit having a secondary amino group are also included in the basic group-containing structural unit. However, in the present disclosure, it is not included in the basic group-containing structural unit regarded as the active hydrogen group-containing structural unit.

[0135] The ester group-containing structural unit is a structural unit having (R 1)2C=C-CO-OR 2 In the formula, R 1 is a hydrogen atom or a methyl group, at least one of which is a hydrogen atom. 2 It is an alkyl group which may have a substituent.

[0136] Furthermore, the structural unit including the active hydrogen group or the basic group as a substituent of the alkyl group is not included in the ester group-containing structural unit regarded as the active hydrogen group-containing structural unit or the basic group-containing structural unit.

[0137] In one embodiment, the combination of structural units possessed by the polymer is preferably a structural unit containing only carboxyl groups, and one or more selected from the group consisting of a structural unit containing a carboxyl group / a structural unit containing a nitrile group, a structural unit containing a hydroxyl group, and a structural unit containing a heterocycle, and more preferably a structural unit containing only carboxyl groups, and one selected from the group consisting of a structural unit containing a carboxyl group / a structural unit containing a nitrile group, a structural unit containing a carboxyl group / a structural unit containing a nitrile group / a structural unit containing a hydroxyl group.

[0138] Among them, preferred are those having only a carboxyl group-containing structural unit or a combination of a carboxyl group-containing structural unit / a nitrile group-containing structural unit.

[0139] The method for producing the polymer is not particularly limited. For example, solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and precipitation polymerization can be cited. Among them, solution polymerization or precipitation polymerization is preferred. The polymerization reaction system can be cited, for example, ion polymerization, free radical polymerization, addition polymerization such as living free radical polymerization, etc. Among them, free radical polymerization or living free radical polymerization is preferred. In addition, free radical polymerization initiators can be cited, for example, peroxides, azo initiators, etc.

[0140] When performing radical polymerization, examples of the polymerization initiator include the following, but are not limited to these.

[0141] Organic peroxides such as di-tert-butyl peroxide, lauroyl peroxide, stearyl peroxide, benzoyl peroxide, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, dilauroyl peroxide, dicumyl peroxide, tert-butyl peroxy-2-ethyl hexanoate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, and

[0142] Common azo-based radical polymerization initiators include azobisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis(1-cyclohexanecarbonitrile), 2,2'-azobis-4-methoxy-2,4-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, and 2,2'-azobis-2-methylbutyronitrile.

[0143] These may be used alone or in combination of two or more. These radical polymerization initiators may be used in combination with an appropriate reducing agent as a redox initiator.

[0144] These polymerization initiators are usually used in an amount of 1 part by mass or less based on 100 parts by mass of the total mass of all monomers used. The amount of the polymerization initiator can be appropriately selected in consideration of the polymerization temperature and the half-life of the polymerization initiator.

[0145] In the manufacturing process of the polymer, the molecular weight of the produced polymer can be controlled by using a chain transfer agent or the like within a range that does not impair the purpose of the present invention. Examples of the chain transfer agent include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, and 3-mercapto-1,2-propylene glycol, thioglycolates such as octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene, and β-pinene.

[0146] In terms of operability and stability, 3-mercapto-1,2-propanediol, thioglycolates, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene and β-pinene are particularly preferred. When the above compounds are used, the obtained polymer has a low odor, which is also preferred in this regard. In one embodiment, as a chain transfer agent, it is preferred to use one of the above compounds alone, or to use two or more of them in combination.

[0147] The chain transfer agent can be appropriately added according to the required molecular weight. Generally speaking, it is preferably used in the range of 0.001 to 4 parts by mass relative to 100 parts by mass of the total mass of all monomers used. In one embodiment, the amount of the chain transfer agent is preferably 0.01 to 4 parts by mass, more preferably 0.1 to 2 parts by mass. By setting the chain transfer agent to the range, the molecular weight of the polymer used as a dispersant in the present embodiment can be easily adjusted to a preferred range.

[0148] In addition, other molecular weight control methods include a method of changing the polymerization method, a method of adjusting the amount of the polymerization initiator, and a method of changing the polymerization temperature, etc. These molecular weight control methods may be used alone or in combination of two or more methods.

[0149] The molecular weight can be measured, for example, by the following method using a gel permeation chromatograph (GPC) equipped with a refractive index (RI) detector and an ultraviolet (UV) detector (210 nm).

[0150] A specific example of an apparatus that can be used for the measurement is HLC-8320GPC (manufactured by Tosoh Corporation), and the measurement can be performed as follows.

[0151] ·Separation column: Connect the following in series.

[0152] TSK gel guard column (TSKgel Guardcolumn) PWXL (6.0mmI.D.×4cm)

[0153] TSK gel (TSKgel) GMPXL (7.8mmI.D.×30cm) 2 pieces

[0154] Column temperature: 40℃

[0155] ·Eluent: 0.2M phosphate buffer (pH 7.0)

[0156] Flow rate: 1.0mL / min

[0157] The sample was prepared at a concentration of 0.1% by mass in a mixed solution containing the eluent, and 0.1 mL was injected. The molecular weight was calculated using a conversion value using standard polyethylene oxide / polyethylene glycol (PEO / PEG) (Agilent Technologies).

[0158] In some embodiments, the acid value of the dispersant including the carboxyl group-containing structural unit may preferably be 400 mgKOH / g to 800 mgKOH / g, more preferably 500 mgKOH / g to 800 mgKOH / g, and even more preferably 600 mgKOH / g to 800 mgKOH / g.

[0159] When the acid value of the dispersant is within the above range, the adsorption of CNTs can be easily improved, and good solubility in the solvent that serves as the dispersion medium can be easily obtained, so there is a tendency to easily maintain a good dispersion state. The dispersion medium (solvent) contains water and may also contain other media that have an affinity with water as needed. When the acid value of the dispersant is less than 400 mgKOH / g, the COO -On the other hand, when the acid value of the dispersant exceeds 900 mgKOH / g, it may cause corrosion of the equipment used in the dispersion process.

[0160] The acid value is a value measured in accordance with Japanese Industrial Standards "K0070: 1992. Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemicals", and refers to the amount (mg) of potassium hydroxide required to completely neutralize 1 g of the resin component.

[0161] In the carbon nanotube dispersion composition, the polymer functions as a dispersant. From this viewpoint, the content of the dispersant (B) in the carbon nanotube dispersion composition is preferably determined based on the specific surface area and wettability of the carbon nanotubes.

[0162] In one embodiment, the content of the dispersant (B) is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and preferably 160 parts by mass or less, more preferably 140 parts by mass or less, and further preferably 90 parts by mass or less, relative to 100 parts by mass of carbon nanotubes.

[0163] If it is above the lower limit, the amount of dispersant becomes appropriate, further suppressing the aggregation of carbon nanotubes. By being below the upper limit, the decrease in fluidity caused by the increase in viscosity of the dispersed composition caused by the excess amount of polymer components is prevented and the deterioration of storage stability is suppressed, so it is preferred. The content of dispersant (B) has an appropriate amount corresponding to the specific surface area of ​​the carbon nanotubes. As the specific surface area increases, the amount of dispersant is preferably increased within a preferred range. For example, when the BET specific surface area of ​​the carbon nanotubes used as a raw material is 100 m 2 / g and above 1200m 2 When the carbon nanotube content is 0.1 / g or less, the content of the dispersant (B) is preferably 15 to 160 parts by mass relative to 100 parts by mass of the carbon nanotubes.

[0164] <Solvent(C)>

[0165] The dispersion composition of the present embodiment contains a solvent.

[0166] The solvent is not particularly limited, and includes water, and may further include other media having affinity with water as necessary.

[0167] Examples of other media having an affinity for water include ethanol, propanol, isopropanol, butanol, octanol, hexadecanol, acetylene alcohol, ethylene glycol monobutyl ether, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, acetylene glycol, polyoxyalkylene glycol, propylene glycol, and other glycols.

[0168] <Basic compound (D)>

[0169] About the dispersion composition of the present embodiment, in order to obtain the desired pH value, any method can be applied, and alkaline compounds can be preferably used. Therefore, in one embodiment, the dispersion composition includes alkaline compounds (D). By the dispersion composition containing alkaline compounds (D), the carboxyl group of the dispersant (B) interacts under strong polarization, generates electric repulsion, and can easily improve the fluidity and storage stability of the dispersion composition. The added alkaline compound (D) can be listed, for example: inorganic bases, inorganic metal salts, organic bases and organic alkali salts. Among these, in terms of the aspect that a small amount of addition can play an effect, it is preferably an inorganic base or inorganic metal salt with greater polarization.

[0170] The basic compound may be added during dispersion or added immediately after dispersion and then stirred thoroughly. Of these, adding the basic compound during dispersion is preferred because it can accelerate the dispersion rate of the dispersant (B).

[0171] Examples of the inorganic base and inorganic metal salt include chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, borates of alkali metals or alkaline earth metals, and ammonium hydroxide, etc. Among these, hydroxides, carbonates, and alkoxides of alkali metals or alkaline earth metals are preferred from the viewpoint of being able to easily supply cations.

[0172] Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of alkali metal carbonates include sodium carbonate, potassium carbonate, etc. Examples of alkaline earth metal hydroxides include calcium hydroxide, magnesium hydroxide, etc. Among these, it is more preferred to use at least one selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate. In addition, the metal contained in the inorganic base may also be a transition metal.

[0173] Examples of alkali metal alkoxides include lithium methoxide, lithium ethoxide, lithium n-butoxide, lithium tert-butoxide, potassium methoxide, potassium ethoxide, potassium n-butoxide, potassium tert-butoxide, sodium methoxide, sodium ethoxide, sodium n-butoxide, sodium tert-butoxide, etc. The carbon number of the alkoxide may be 5 or more. Sodium tert-butoxide is particularly preferred.

[0174] Examples of the alkoxide of an alkaline earth metal include magnesium methoxide, magnesium ethoxide, magnesium n-butoxide, magnesium tert-butoxide, etc. The alkoxide may have 5 or more carbon atoms.

[0175] Among these, more preferably lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, lithium tert-butoxide, potassium tert-butoxide, sodium tert-butoxide, and further preferably sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, and most preferably sodium hydroxide and sodium carbonate. In addition, in the present embodiment, the metal possessed by the inorganic base and the inorganic metal salt may also be a transition metal.

[0176] Examples of the organic base include primary amine compounds, secondary amine compounds, tertiary amine compounds (alkylamines, amino alcohols, etc.) having 1 to 40 carbon atoms and optionally having a substituent, organic hydroxides, and organic metal salts.

[0177] Examples of the organic base include primary alkylamines, secondary alkylamines, tertiary alkylamines having 1 to 40 carbon atoms and an optionally substituted alkyl group, and other compounds containing a basic nitrogen atom.

[0178] Examples of the primary alkylamine having 1 to 40 carbon atoms and having an optionally substituted alkyl group include propylamine, butylamine, isobutylamine, octylamine, 2-ethylhexylamine, laurylamine, stearylamine, oleylamine, 2-aminoethanol, 3-aminopropanol, 3-ethoxypropylamine, and 3-lauryloxypropylamine.

[0179] Examples of the secondary alkylamine having 1 to 40 carbon atoms and having an optionally substituted alkyl group include dibutylamine, diisobutylamine, N-methylhexylamine, dioctylamine, distearylamine, and 2-methylaminoethanol.

[0180] Examples of the tertiary alkylamine having 1 to 40 carbon atoms and having an optionally substituted alkyl group include triethylamine, tributylamine, N,N-dimethylbutylamine, N,N-diisopropylethylamine, dimethyloctylamine, tri-n-butylamine, dimethylbenzylamine, trioctylamine, dimethyldecylamine, dimethyllaurylamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, dilaurylmonomethylamine, triethanolamine, and 2-(dimethylamino)ethanol.

[0181] Among these, a primary alkylamine, a secondary alkylamine or a tertiary alkylamine having 1 to 30 carbon atoms and having an alkyl group which may be substituted is preferred, and a primary alkylamine, a secondary alkylamine or a tertiary alkylamine having 1 to 20 carbon atoms and having an alkyl group which may be substituted is more preferred.

[0182] The term "optionally substituted alkyl group" means that a hydrogen atom may be substituted, and examples of the substituent include a hydroxyl group and the like.

[0183] Other compounds containing a basic nitrogen atom include, for example, 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN), 1,4-diazabicyclo[2.2.2]octane (DABCO), imidazole, and 1-methylimidazole.

[0184] The content of the basic compound (D) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, based on the mass of the dispersion composition, and is preferably 0.40% by mass or less, more preferably 0.20% by mass or less, and further preferably 0.15% by mass or less.

[0185] If the content of the basic compound (D) is 0.01% by mass or more, there is a tendency to easily obtain the effect of storage stability. In addition, if the content of the basic compound is 0.40% by mass or less, it is possible to suppress the dispersant from detaching from the carbon nanotubes, thereby preventing the dispersion device and / or the battery from causing corrosion inside, which is therefore preferred.

[0186] <Other optional ingredients>

[0187] The carbon nanotube dispersion composition of this embodiment can be appropriately formulated with other carbon-based conductive materials such as carbon black other than carbon nanotubes (A), dispersants other than dispersant (B), binders, surfactants, other additives, etc. as needed within the scope that does not hinder the purpose of the present invention, and can be added at any time such as before, during, or after the dispersion of the dispersion composition, or when preparing the composite material slurry.

[0188] The carbon nanotube dispersion composition of the present embodiment is not particularly limited as long as the carbon nanotubes can be dispersed and stabilized. When dispersing the carbon nanotubes, a surfactant or other dispersants may be used in addition to the dispersant (B).

[0189] [Surfactant]

[0190] Surfactants are mainly classified into anionic, cationic, nonionic and amphoteric surfactants. A preferred type of dispersant can be used in a preferred amount according to the properties required for dispersion of carbon nanotubes.

[0191] When anionic surfactants are selected, their types are not particularly limited. Specifically, fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfate ester salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl aryl ether sulfates, naphthalenesulfonic acid formalin condensates, polyoxyethylene alkyl phosphoric acid sulfonates, glyceryl borate fatty acid esters and polyoxyethylene glycerol fatty acid esters can be listed, but they are not limited to these. Furthermore, specifically, sodium dodecylbenzene sulfonate, sodium laurate sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate ester salts and sodium salts of β-naphthalenesulfonic acid formalin condensates can be listed, but they are not limited to these.

[0192] In addition, as cationic surfactants, there are alkylamine salts and quaternary ammonium salts. Specifically, stearylamine acetate, trimethyl coconut oil ammonium chloride, trimethyl tallow ammonium chloride, dimethyl dioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate (lauryl pyridinium disulfate), cetyl pyridinium bromide, 4-alkyl mercaptopyridine, poly (vinyl pyridine) - dodecyl bromide and dodecyl benzyl triethyl ammonium chloride can be listed, but it is not limited to these. In addition, as amphoteric surfactants, aminocarboxylates can be listed, but it is not limited to these.

[0193] In addition, as nonionic surfactants, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and alkyl allyl ethers can be listed, but they are not limited to these. Specifically, polyoxyethylene lauryl ether, sorbitan fatty acid esters and polyoxyethylene octyl phenyl ethers can be listed, but they are not limited to these.

[0194] The selected surfactant is not limited to a single surfactant. Therefore, two or more surfactants can also be used in combination. For example, a combination of anionic surfactant and nonionic surfactant or a combination of cationic surfactant and nonionic surfactant can be used. The blending amount at this time is preferably set to a preferred blending amount relative to each surfactant component. As a combination, a combination of anionic surfactant and nonionic surfactant is preferred. The anionic surfactant is preferably a polycarboxylate. The nonionic surfactant is preferably polyoxyethylene phenyl ether.

[0195] [Other dispersants]

[0196] As the dispersant used for dispersing the carbon nanotubes, in addition to the dispersant (B), other dispersants such as a resin-type dispersant may be used.

[0197] Specific examples of the resin dispersant include fluorine-based resins, polyvinyl alcohol, polyvinyl butyral, and polyvinyl pyrrolidone. Polyvinyl alcohol and polyvinyl pyrrolidone are particularly preferred. The molecular weight of the resin dispersant is preferably 10,000 to 300,000.

[0198] [Adhesive]

[0199] The binder is a resin that can bind carbon-based conductive materials, other particles, and other substances, and is added to the dispersion after the carbon nanotubes are dispersed. That is, it has a different function from the dispersant described in this specification. As the binder, the same binder as the dispersant can be used.

[0200] When the carbon nanotube-dispersed composition is used in a secondary battery, the binder is not particularly limited as long as it is a binder generally used in secondary batteries, and can be appropriately selected depending on the purpose.

[0201] Examples of binders used in secondary batteries include: polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylate, methacrylic acid, methacrylate, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenol resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins (e.g., carboxymethylcellulose (CMC)); elastomers such as styrene butadiene rubber and fluororubber; conductive resins such as polyaniline and polyacetylene, etc.

[0202] In addition, it can also be a modified body or mixture and copolymer of these resins. Among these, when used as a binder for the positive electrode, in terms of tolerance, it is preferably a polymer or copolymer having a fluorine atom in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene, etc. In addition, when used as a binder for the negative electrode, it is preferably carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, etc. with good adhesion.

[0203] <Method for producing dispersion composition>

[0204] The method for producing a dispersed composition comprises: step I, dispersing a mixture of carbon nanotubes (A), a dispersant (B), a solvent (C), and, if necessary, a basic compound (D), and reducing the particle size D at a volume accumulation of 50% obtained by laser diffraction particle size distribution measurement to a dispersion treatment step II. 50 In the step II, the pH of the mixture is adjusted to a range of 0.3 μm to 7 μm; and in the step II, the pH of the mixture is adjusted to a range of the following (Formula a) and (Formula b). In the following (Formula a) and (Formula b), X is the particle size D at a volume accumulation of 50% obtained by laser diffraction particle size distribution measurement after the dispersion treatment. 50 [μm], Y is pH.

[0205] (Formula a) Y≧-0.149X+4.545

[0206] (Formula b) Y ≦ -0.134X + 5.140

[0207] In the production method, step I and step II may be performed continuously as separate steps, or may be performed simultaneously without distinguishing between them. For example, when a basic compound (D) is used as a method for adjusting pH, step I and step II may be performed simultaneously.

[0208] Hereinafter, a method for dispersing carbon nanotubes in a solvent as an example of a method for producing a dispersed composition is described. The dispersed composition is preferably produced by dispersing carbon nanotubes (A), dispersant (B) and solvent (C), and optionally alkaline compound (D) using a dispersing device and finely dispersing them. In addition, the dispersion treatment can arbitrarily adjust the timing of adding the materials used, and a multi-stage treatment of more than two times can be applied.

[0209] Dispersing devices include, for example, kneaders, double-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, annular bead mills, grinders, high-shear mixers, high-pressure homogenizers, ultrasonic homogenizers, etc. Among them, in order to finely disperse the carbon nanotubes in the dispersion composition to obtain preferred dispersibility, it is preferred to use a high-shear mixer, a high-pressure homogenizer, an ultrasonic homogenizer, or a combination of these. In particular, from the perspective of promoting the wetting of carbon nanotubes and decomposing coarse particles, it is preferred to use a high-shear mixer in the initial process of dispersion, and then, from the perspective of dispersing while maintaining the aspect ratio of the carbon nanotubes, it is preferred to use a high-pressure homogenizer. The pressure when using a high-pressure homogenizer is preferably 40MPa to 150MPa, and more preferably 70MPa to 150MPa.

[0210] The dispersion method using the dispersion device includes batch dispersion, through dispersion, circulation dispersion, etc., which can be any method, or two or more methods can be combined. The so-called batch dispersion is a method of dispersing using only the dispersion device body without using piping, etc. Because the operation is simple, it is preferred in the case of small-scale production. The so-called through dispersion is a dispersion method in which a tank for supplying a dispersed liquid (a mixture containing a dispersed substance and a dispersion medium and being a precursor of a dispersed composition) and a tank for receiving the dispersed liquid are included in the dispersion device body via piping, so that the dispersed liquid passes through the dispersion device body. In addition, the so-called circulation dispersion is a method of dispersing while circulating the dispersed liquid while returning the dispersed liquid that has passed through the dispersion device body to the tank for supplying the dispersed liquid.

[0211] In any method, the longer the processing time is extended, the more dispersion is performed. Therefore, it is sufficient to repeatedly pass or circulate until the target dispersion state is reached. If the size of the tank or the processing time is changed, the processing volume can be increased. Compared with the circulation dispersion, the through-type dispersion is easy to make the dispersion state uniform, so it is preferred in this respect. Compared with the through-type dispersion, the circulation dispersion is simple in operation or manufacturing equipment, so it is preferred in this respect. In the dispersion process, the crushing of the agglomerated particles, the decomposition, wetting, stabilization, etc. of the carbon nanotubes are carried out sequentially or simultaneously. The dispersion state after completion is different depending on the method of carrying out, so it is preferred to manage the dispersion state in each dispersion process by various evaluation methods.

[0212] In the dispersion composition of the present embodiment, based on 100% by mass of the dispersion composition, the content of carbon nanotubes is preferably more than 0.3% by mass, more preferably more than 0.4% by mass, and further preferably more than 0.5% by mass. In addition, preferably less than 6.0% by mass, more preferably less than 5.0% by mass. By setting the content above the lower limit, the compression brought by the carbon nanotube dispersion composition in the formulation design of the composite material slurry can be suppressed, and by setting the content below the upper limit, the fluidity or handling of the dispersion composition can be ensured, so it is preferred.

[0213] The average outer diameter of the carbon nanotubes in the carbon nanotube dispersion composition of the present embodiment is preferably 1 nm or more and 100 nm or less, more preferably 1.5 nm or more and 70 nm or less, and further preferably 2 nm or more and 50 nm or less. If it is above the lower limit, the fiber can be prevented from breaking, and the volume change accompanying the absorption and release of lithium ions relative to the active material can be followed, so it is preferred. If it is below the upper limit, the number of fibers relative to the amount added to the electrode becomes sufficient and preferred.

[0214] The average fiber length of the carbon nanotubes in the carbon nanotube dispersion composition of the present embodiment is preferably 0.3 μm or more and 50 μm or less, more preferably 0.5 μm or more and 20 μm or less. If it is above the lower limit, a conductive path between active materials can be fully formed, so it is preferred. If it is below the upper limit, the entanglement of carbon nanotubes with each other can be suppressed and generated and locally present in the electrode, preventing damage to battery performance, so it is preferred.

[0215] Regarding the average outer diameter and fiber length of the carbon nanotubes in the dispersed composition, the CNT dispersed composition was diluted with a solvent in a manner such that the CNT concentration was 0.048% by mass, and a few μL of the diluted dispersed composition was sprayed on a mica substrate, and then dried on a hot plate at 100°C to prepare a substrate for observing the CNT fiber length. In addition, the solvent used when preparing the CNT dispersed composition was used. The mica substrate can be observed by SEM and image analysis can be measured. The length of the short axis and the length of the long axis of 300 roots are measured and can be calculated based on their average value.

[0216] The dispersibility of the carbon nanotubes in the dispersion composition can be evaluated by the complex elastic modulus and phase angle obtained by dynamic viscoelasticity measurement. The complex elastic modulus represents the hardness of the dispersion composition, and there is a tendency that the better the dispersibility of the carbon nanotubes and the lower the viscosity, the smaller the complex elastic modulus. However, in the case where the fiber length of the carbon nanotubes is large, even if the carbon nanotubes are uniformly and stably decomposed in the medium, the complex elastic modulus sometimes becomes a high value because the carbon nanotubes themselves have structural viscosity. As one embodiment, the complex elastic modulus of the dispersion composition is preferably 5Pa or more at 25°C and 1Hz, more preferably 10Pa or more. In addition, it is preferably less than 300Pa, more preferably less than 60Pa.

[0217] By setting the complex elastic modulus of the dispersion composition within the above range, even a carbon-based conductive material having a long fiber length such as carbon nanotubes can be prepared as a dispersion composition of the carbon-based conductive material uniformly and well dispersed while maintaining the fiber length at a certain level or more.

[0218] In addition, phase angle refers to the phase offset of stress wave when the strain imparted to the dispersion composition is set as sine wave. If it is a pure elastic body, it becomes a sine wave of the same phase as the imparted strain, so it becomes a phase angle of 0 °. On the other hand, if it is a pure viscous body, it becomes a stress wave of 90 ° of offset. In common viscoelasticity determination sample, it becomes a sine wave greater than 0 ° and less than 90 ° of phase angle, if the dispersibility of the carbon nanotubes in the dispersion composition is good, then the phase angle is close to 90 ° as a pure viscous body.

[0219] However, similarly to the complex elastic modulus, when the carbon nanotubes themselves have structural viscosity, even when the carbon nanotubes are uniformly and stably decomposed in the medium, the phase angle sometimes becomes a low value. From this point of view, as one embodiment, the phase angle at 25°C and 1Hz obtained by the dynamic viscoelasticity measurement of the dispersed composition is preferably 3° or more, more preferably 5° or more, and further preferably 10° or more. In addition, it is preferably less than 60°, more preferably less than 50°.

[0220] By setting the phase angle of the dispersion composition within the above range, even a carbon-based conductive material having a long fiber length such as carbon nanotubes can be prepared as a dispersion composition in which the carbon-based conductive material is uniformly and well dispersed while maintaining the fiber length at a certain level or more.

[0221] By making the carbon nanotubes with large fiber length uniformly and well dispersed under the state that the length is maintained at a certain level or more, a developed conductive network is formed. Therefore, it is not only necessary that the viscosity of the carbon nanotube dispersion composition is low (apparent) and the dispersion is good, but it is important to judge the dispersion state by combining any one or both of the complex elastic modulus and the phase angle with the previous indexes such as viscosity. Among them, it is particularly important to focus on the phase angle. With regard to this viewpoint, by setting the complex elastic modulus and the phase angle to the range, a carbon nanotube dispersion composition with good conductivity and electrode strength can be easily obtained. The complex elastic modulus and the phase angle of the carbon nanotube dispersion composition can be measured by the method described in the embodiment.

[0222] The viscosity of the dispersion composition of the present embodiment was measured using a rheometer at a shear rate of 1 (s -1 ) is preferably 5 Pa·s or more, more preferably 10 Pa·s or more, and further preferably 20 Pa·s or more. In addition, it is preferably less than 60 Pa·s, and more preferably less than 40 Pa·s. In addition, when using a rheometer at a shear rate of 10 (s -1 ) is preferably 1 Pa·s or more, and preferably less than 10 Pa·s. By setting the viscosity at each shear rate within the above range, the dispersed particle size and dispersed state of the carbon nanotubes can be improved, and the electrode strength and conductivity can be improved.

[0223] The dispersed composition of the present embodiment can be made into a composite material slurry by further adding an active material, and can be used to form an electrode film.

[0224] In addition, a film formed using the dispersion composition can improve the adhesion between the electrode film and the current collector or improve the conductivity of the electrode film, and thus can also be used as a base layer in the electrode.

[0225] <2> Composite material slurry

[0226] The composite material slurry of the present embodiment can be obtained by adding an active material to a dispersion composition, and can be preferably used for a secondary battery electrode.

[0227] The dispersion composition of the present embodiment is excellent in fluidity and dispersion stability, and therefore a composite material slurry in which carbon nanotubes are uniformly dispersed can be obtained, and a conductive path can be sufficiently maintained in the formed electrode.

[0228] The active material may be a positive electrode active material or a negative electrode active material. In this specification, the positive electrode active material and the negative electrode active material are sometimes referred to as "active material". The so-called active material is a material that becomes the basis of the battery reaction. The active material is divided into a positive electrode active material and a negative electrode active material according to the electromotive force. By using the positive electrode active material, a positive electrode composite material slurry can be made, and by using the negative electrode active material, a negative electrode composite material slurry can be made.

[0229] In order to improve uniformity and processability, the composite material slurry is preferably in a slurry state.

[0230] In addition, if necessary, for the purpose of adhesion and wetting, surface activity, pH adjustment, wetting promotion, leveling, conductivity assistance, etc., other arbitrary components may be appropriately included within the scope that does not hinder the purpose of the present invention. The arbitrary components can be added at any time such as before the composite material slurry is prepared, during mixing, after mixing, or a combination of these.

[0231] A binder may be added to the dispersion composition for the purpose of further binding the active substance and the like.

[0232] As the adhesive used in the manufacture of the composite material slurry, if it is a polymer component commonly used as an adhesive for batteries, there is no particular restriction and it can be appropriately selected according to the purpose. The polyvinylidene fluoride resin that may have a substituent can be used. As other polymer components, for example, polymers or copolymers having ethylene, propylene, vinyl chloride, vinyl acetate, maleic acid, acrylic acid, acrylate, methacrylic acid, methacrylate, styrene, etc. as constituent components can be used; polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, acrylic resin, formaldehyde resin, silicone resin; elastomers such as styrene butadiene rubber and fluororubber; conductive resins such as polyaniline and polyacetylene. In addition, it can also be a modified body or mixture and copolymer of these resins, which can be used alone or in combination of two or more. These resins can also be used as thickeners.

[0233] Relative to 100 parts by mass of active material, the content of CNT in the composite material slurry is preferably more than 0.01 parts by mass, more preferably more than 0.03 parts by mass, and further preferably more than 0.05 parts by mass. In addition, preferably less than 10 parts by mass, more preferably less than 5 parts by mass, and further preferably less than 3 parts by mass. If it is below the upper limit, the filling amount of the active material in the electrode can be prevented from being reduced, and the battery low capacity can be suppressed. In addition, if it is above the lower limit, the conductivity of the electrode and the battery becomes sufficient, so it is preferred.

[0234] Relative to 100 parts by mass of active material, the content of the binder in the composite material slurry is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more. By setting it to above the lower limit, the adhesion of the conductive film can be further improved. In addition, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. By setting it to below the upper limit, the active material concentration of the conductive film can be increased, thereby further realizing high capacity.

[0235] <Positive electrode active material>

[0236] The positive electrode active material is not particularly limited. For example, in secondary battery applications, metal compounds such as metal oxides and metal sulfides that can be reversibly doped or embedded with lithium ions can be used. Examples include lithium manganese composite oxides (e.g., Li x Mn2O4 or Li x MnO2), lithium nickel composite oxides (such as Li x NiO2), lithium cobalt composite oxide (Li x CoO2), lithium nickel cobalt composite oxide (such as Li x Ni 1-y Co y O2), lithium manganese cobalt composite oxide (such as Li x Mn y Co 1-y O2), lithium nickel manganese cobalt composite oxide (such as Li x Ni y Co z Mn 1-y-z O2), spinel lithium manganese nickel composite oxide (such as Li x Mn 2-y Ni y O4) and other lithium and transition metal composite oxide powders, lithium phosphate powders with olivine structure (such as Li x FePO4、Li x Fe 1-y Mn y PO4、Li x CoPO4, etc.), manganese oxide, iron oxide, copper oxide, nickel oxide, vanadium oxide (such as V2O5, V6O 13 ), transition metal oxide powders such as titanium oxide, transition metal sulfide powders such as iron sulfate (Fe2(SO4)3), TiS2 and FeS, etc. Among them, x, y, z are quantities, 0<x<1, 0<y<1, 0<z<1, 0<y+z<1. These positive electrode active materials can also be used alone or in combination.

[0237] <Negative electrode active material>

[0238] The negative electrode active material is not particularly limited, and for example, metal Li or its alloys, tin alloys, silicon alloy negative electrodes, Li x TiO2、Li x Fe2O3、Li x Fe3O4、Li x Metal oxides such as WO2, conductive polymers such as polyacetylene and polyparaphenylene, carbonaceous powders such as artificial graphite or natural graphite of highly graphitized carbon materials, and resin calcined carbon materials. Wherein, x is the number, 0<x<1. These negative electrode active materials can also be used alone or in combination. In particular, when a silicon alloy negative electrode is used, the theoretical capacity is large, and on the other hand, the volume expansion is extremely large, so it is preferably used in combination with carbonaceous powders such as artificial graphite or natural graphite of highly graphitized carbon materials, resin calcined carbon materials, etc.

[0239] In addition, the volume change of the silicon-based active material accompanying the absorption / release of lithium ions is large, and if the conductive path formed by the carbon nanotubes adjusted to an appropriate particle size cannot be ensured, it is difficult to perform good repeated charge and discharge. However, the dispersed composition of this embodiment has excellent fluidity and dispersion stability, so even if graphite powder and silicon-based active materials are used as negative electrode active materials, the internal resistance in the electrode can be suppressed from increasing and the charge and discharge capacity can be suppressed from decreasing.

[0240] <Method for producing composite material slurry>

[0241] In the method for making composite material slurry, when adding a binder to the dispersed composition, the order of adding the binder and the active substance is not particularly limited. For example, there can be listed: a method of adding a binder to the dispersed composition, and then adding an active substance to make it; a method of adding an active substance to the dispersed composition, and then adding a binder to make it; a method of adding a binder and an active substance to the dispersed composition to make it, etc. In addition, the binder can also be added after being dissolved in advance. As a method for making composite material slurry, it is preferably a method of performing the following treatment: adding a binder to the dispersed composition, and then, further adding an active substance and stirring it. The stirring device used in the stirring is not particularly limited. The stirring device can use a disperser, a homogenizer, etc.

[0242] The nonvolatile content of the composite material slurry is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, based on the mass of the composite material slurry (100% by mass).

[0243] <3>Electrode film

[0244] The electrode film is formed by forming a composite material slurry into a film shape, and at least comprises carbon nanotubes (A), a dispersant (B) and an alkaline compound (D) as needed and an active substance. The electrode film may also further comprise any component such as a binder. The electrode film can be obtained, for example, by adding an active substance and an optional binder to the carbon nanotube dispersion composition to make a composite material slurry, and coating or applying the composite material slurry. In addition, for example, the electrode film can be formed by applying the composite material slurry to a collector and removing the volatile components.

[0245] <4> Secondary batteries

[0246] The secondary battery as one embodiment of the present invention preferably includes a positive electrode, a negative electrode and an electrolyte, and at least one selected from the group consisting of the positive electrode and the negative electrode has an electrode film formed by the composite material slurry as the present embodiment. The positive electrode and the negative electrode may also include a collector. In addition, when one of the electrode films of the positive electrode or the negative electrode is an electrode film using a dispersed composition based on the present embodiment, the electrode film of the other electrode is not particularly limited and may be a conventionally known electrode film.

[0247] In this embodiment, the structure of the secondary battery is not particularly limited. Typically, the secondary battery may include a separator as required in addition to a positive electrode, a negative electrode, and an electrolyte. The secondary battery may be in various shapes such as a paper type, a cylindrical type, a button type, and a stacked type according to the purpose of use.

[0248] <Positive or negative pole>

[0249] The positive electrode or negative electrode has an electrode film and a current collector formed by using a composite material slurry as a dispersion composition of the present embodiment. The electrode film can be formed, for example, by applying the dispersion composition on the current collector and drying it. The electrode film formed using the positive electrode composite material slurry can be used as a positive electrode. The electrode film formed using the negative electrode composite material slurry can be used as a negative electrode. In this specification, a film formed using a dispersion composition containing an active substance is sometimes referred to as an "electrode composite material layer".

[0250] The material and shape of the current collector used in the formation of the electrode film are not particularly limited, and the material and shape suitable for various secondary batteries can be appropriately selected. As the material of the current collector, conductive metals or alloys such as aluminum, copper, nickel, titanium or stainless steel can be listed. In addition, as the shape, generally speaking, a flat foil is used, and a current collector with a roughened surface, a perforated foil-shaped current collector, and a mesh-shaped current collector can also be used. The thickness of the current collector is preferably about 0.5μm to 30μm.

[0251] As the method for applying the dispersion composition on the collector, there is no particular restriction, and known methods can be used. Specifically, die coating, dip coating, roll coating, blade coating, spray coating, gravure coating, screen printing or electrostatic coating can be listed. As a drying method, placing and drying or using an air supply dryer, warm air dryer, infrared heater, far infrared heater, etc. can be listed, but it is not particularly limited to these.

[0252] After coating, the coating may be subjected to a calendering treatment using a lithographic press, a calender roll, etc. The thickness of the formed film is, for example, 1 μm or more and 500 μm or less, and preferably 10 μm or more and 300 μm or less.

[0253] <Electrolytes>

[0254] As an electrolyte, various electrolytes known in the past in which ions can move can be used. For example, LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, Li(CF3SO2)3C, LiI, LiBr, LiCl, LiAlCl, LiHF2, LiSCN or LiBPh4 (wherein Ph is phenyl) and other electrolytes containing lithium salts can be listed, but are not limited to these. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolyte.

[0255] The non-aqueous solvent is not particularly limited, and examples thereof include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octalactone; glycol dimethyl ethers (glymes) such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and cyclopentane; and nitriles such as acetonitrile. These solvents may be used alone, or two or more thereof may be mixed and used.

[0256] The secondary battery preferably has a separator. Examples of the separator include polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, and nonwoven fabrics obtained by subjecting these nonwoven fabrics to a hydrophilic treatment, but the separator is not particularly limited to these.

[0257] The embodiments of the present invention include the following. However, the present invention is not limited to the following embodiments and includes various forms.

[0258] [1] A carbon nanotube dispersion composition, characterized in that it comprises carbon nanotubes (A), a dispersant (B), a solvent (C) and a basic compound (D),

[0259] Particle diameter D at volume accumulation 50% obtained by laser diffraction particle size distribution measurement 50 0.3μm~7μm,

[0260] The carbon nanotube dispersion composition satisfies the following (1) and (2).

[0261] (1) The dispersant (B) is a polymer having a weight average molecular weight of 5,000 or more and 360,000 or less and having a structural unit containing a carboxyl group,

[0262] The content of the carboxyl group-containing structural unit is 80% by mass or more based on the mass of the polymer.

[0263] (2) When the particle size D of the carbon nanotube dispersion composition at the time of volume accumulation of 50% is obtained by laser diffraction particle size distribution measurement, 50 When ρ is X [μm] and pH is Y, X and Y satisfy the following (Formula a) and (Formula b).

[0264] (Formula a) Y≧-0.149X+4.545

[0265] (Formula b) Y ≦ -0.134X + 5.140

[0266] [2] The carbon nanotube dispersion composition according to [1], wherein the phase angle at 25°C and 1 Hz obtained by dynamic viscoelasticity measurement is 3° or more and less than 60°.

[0267] [3] The carbon nanotube dispersion composition according to [1] or [2], wherein the complex elastic modulus at 25°C and 1 Hz obtained by dynamic viscoelasticity measurement is 5 Pa or more and less than 300 Pa.

[0268] [4] The carbon nanotube dispersion composition according to any one of [1] to [3], wherein the content of the dispersant (B) is 15 to 90 parts by mass based on 100 parts by mass of the carbon nanotubes (A).

[0269] [5] The carbon nanotube dispersion composition according to any one of [1] to [4], wherein the carboxyl group-containing structural unit is a structural unit derived from (meth)acrylic acid.

[0270] [6] A composite material slurry comprising the carbon nanotube dispersion composition according to any one of [1] to [5] and an active substance.

[0271] [7] An electrode membrane formed from the composite material slurry described in [6] above.

[0272] [8] A secondary battery comprising a positive electrode and a negative electrode, wherein:

[0273] At least one of the positive electrode and the negative electrode has the electrode film according to [7] above.

[0274] The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2023-142456 filed on September 1, 2023, and all the disclosed contents are incorporated by reference in the present application.

[0275] Example

[0276] The present invention will be described in more detail below by giving examples. The present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, "parts" means "parts by mass" and "%" means "% by mass" unless otherwise specified.

[0277] <Average outer diameter of carbon nanotubes>

[0278] Measurement method: Use an ultrasonic homogenizer to disperse carbon nanotubes in toluene, then place them on a collodion film and dry them. Use a transmission electron microscope (TEM) to observe and photograph the dried carbon nanotubes. Next, select any 100 carbon nanotubes from the observation photo and measure their outer diameters. Next, calculate the average outer diameter (nm) of the raw material carbon nanotubes as the number average of the outer diameters.

[0279] <Measurement of specific surface area of ​​carbon nanotubes>

[0280] 0.03 g of CNT was weighed using an electronic balance (Sartorius, MSA225S100DI) and dried at 110° C. for 15 minutes while degassing. The BET specific surface area of ​​CNT was then measured using a fully automatic specific surface area measuring device (Mountech, HM-model 1208).

[0281] The details of the materials used in the present examples and comparative examples are as follows.

[0282] <Carbon nanotubes (A)>

[0283] TuBALL: Single-walled carbon nanotubes (manufactured by OCSiAl, average outer diameter 1.6nm, specific surface area 980m 2 / g)

[0284] 10B: JENOTUBE 10B (manufactured by JEIO, multilayer CNT, average outer diameter 10nm, specific surface area 233m 2 / g)

[0285] 6A: JENOTUBE 6A (manufactured by JEIO, multi-layer CNT, average outer diameter 6nm, specific surface area 680m 2 / g)

[0286] TNSAR: Single-layer carbon nanotubes (manufactured by Timesnano, with an average outer diameter of 1.5 nm and a specific surface area of ​​950 m 2 / g)

[0287] BT1001M: (LGC manufacturing, multi-layer CNT, average outer diameter 10nm, specific surface area 260m 2 / g)

[0288] <Basic compound (D)>

[0289] ·D-1: Na2CO3 (sodium carbonate, manufactured by Tokyo Chemical Industry, purity > 99.0%)

[0290] D-2: NaOH (sodium hydroxide, manufactured by Tokyo Chemical Industry, purity > 98.0%, granular)

[0291] D-3: KOH (potassium hydroxide, manufactured by Tokyo Chemical Industry, purity > 86.0%)

[0292] D-4: CH3COONa (sodium acetate, manufactured by Tokyo Chemical Industry, purity > 98.5%)

[0293] D-5: K2CO3 (potassium carbonate, manufactured by Tokyo Chemical Industry, purity > 99.0%)

[0294] D-6: BtONa (sodium tert-butoxide, manufactured by Tokyo Chemical Industry, purity > 98.0%)

[0295] <Manufacture of dispersant (B) etc.>

[0296] (Dispersant (B-1))

[0297] 137 parts of ion exchange water, 100 parts of acrylic acid, 0.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was removed by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-1)).

[0298] (Dispersant (B-2))

[0299] 137 parts of ion exchange water, 95 parts of acrylic acid, 5 parts of acrylonitrile, 2.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was taken out by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-2)).

[0300] (Dispersant (B-3))

[0301] 137 parts of ion exchange water, 95 parts of acrylic acid, 5 parts of 2-hydroxyethyl acrylate, 0.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, and heated to 70°C and stirred at 70°C for 300 minutes (5 hours). When the conversion rate reached 90% or more, the reaction was terminated by cooling. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over 1 hour. The generated white precipitate was taken out by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-3)).

[0302] (Dispersant (B-4))

[0303] 100 parts of methanol, 0.1 parts of diethanolamine, and 5 parts of sodium hypophosphite were placed in a reaction container including a gas introduction tube, a thermometer, a condenser, and a stirrer, and replaced with nitrogen. The reaction container was heated to 70°C, and 90 parts of acrylic acid and 10 parts of N-vinyl-2-pyrrolidone were added dropwise over 2 hours. Next, an initiator aqueous solution containing 2 parts of 2,2'-azobis-2-amidinopropane dihydrochloride (V-50 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 18 parts of ion-exchanged water was added dropwise over 1 hour and 30 minutes. After the addition was completed, the reaction was allowed to proceed for 3.5 hours, and then an aqueous solution containing 0.1 parts of V-50 and 0.9 parts of ion-exchanged water was added. Furthermore, an aqueous solution containing 0.1 parts of V-50 and 0.9 parts of ion-exchanged water was added again after 30 minutes.

[0304] After 4.5 hours from the start of polymerization, it was confirmed that the conversion rate reached 95%, and 0.5 parts of a 10% malonic acid aqueous solution was added as a pH adjuster to obtain an aqueous dispersion of the polymer. Then, the mixture was filtered and separated by reduced pressure filtration, washed with methanol, and dried under reduced pressure to completely remove the solvent to obtain a polymer (dispersant (B-4)).

[0305] (Dispersant (B-5))

[0306] 137 parts of ion exchange water, 100 parts of methacrylic acid, 0.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was removed by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-5)).

[0307] (Dispersant (B-6))

[0308] 137 parts of ion exchange water, 90 parts of acrylic acid, 5 parts of acrylonitrile, 5 parts of 2-hydroxyethyl acrylate, 2.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, and heated to 70°C and stirred at 70°C for 300 minutes (5 hours). When the conversion rate reached 90% or more, the reaction was terminated by cooling. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of a polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over 1 hour. The generated white precipitate was taken out by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-6)).

[0309] (Dispersant (B-7))

[0310] 137 parts of ion exchange water, 95 parts of acrylic acid, 5 parts of methyl acrylate, 0.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was taken out by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-7)).

[0311] (Dispersant (B-8))

[0312] 137 parts of ion exchange water, 100 parts of acrylic acid, 6.9 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 250 parts of methyl ethyl ketone and 250 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was removed by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-8)).

[0313] (Dispersant (B-9))

[0314] 137 parts of ion exchange water, 100 parts of acrylic acid, 1.25 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 250 parts of methyl ethyl ketone and 250 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was removed by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-9)).

[0315] (Dispersant (B-10))

[0316] 137 parts of ion exchange water, 80 parts of acrylic acid, 20 parts of acrylamide, 0.55 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was taken out by filtration and dried under reduced pressure to obtain a polymer (dispersant (B-10)).

[0317] (Dispersant (B'-1))

[0318] 137 parts of ion exchange water, 70 parts of acrylic acid, 30 parts of acrylonitrile, 2.8 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). When the conversion rate reached 90% or more, the reaction was terminated by cooling. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 500 parts of methyl ethyl ketone and 500 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was taken out by filtration and dried under reduced pressure to obtain a polymer (dispersant (B'-1)).

[0319] (Dispersant (B'-2))

[0320] 137 parts of ion exchange water, 100 parts of acrylic acid, 9.3 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, and heated to 70°C and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 250 parts of methyl ethyl ketone and 250 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was removed by filtration and dried under reduced pressure to obtain a polymer (dispersant (B'-2)).

[0321] (Dispersant (B'-3))

[0322] 137 parts of ion exchange water, 100 parts of acrylic acid, 0.03 parts of 3-mercapto-1,2-propanediol and 0.5 parts of V-50 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to a reaction container including a thermometer, a condenser and a stirrer, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). The reaction was terminated by cooling when the conversion rate reached 90% or more. Thereafter, unreacted raw materials were reduced by heating and reduced pressure distillation to obtain an aqueous solution of the polymer. 250 parts of methyl ethyl ketone and 250 parts of methanol were placed in a four-necked separable flask, and after rotating 1,000 times with a disperser, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The generated white precipitate was removed by filtration and dried under reduced pressure to obtain a polymer (dispersant (B'-3)).

[0323] The molecular weight of the dispersant (B) is measured using a gel permeation chromatograph (GPC) equipped with an RI detector and a UV detector (210 nm). Specifically, it is as follows.

[0324] · Device: HLC-8320GPC (manufactured by Tosoh)

[0325] ·Separation column: Connect the following in series.

[0326] TSK gel guard column (TSKgel Guardcolumn) PWXL (6.0mmI.D.×4cm)

[0327] TSK gel (TSKgel) GMPXL (7.8mmI.D.×30cm) 2 pieces

[0328] Column temperature: 40℃

[0329] ·Eluent: 0.2M phosphate buffer (pH 7.0)

[0330] Flow rate: 1.0mL / min

[0331] The sample was prepared at a concentration of 0.1% by mass in the mixed solution containing the eluent, and 0.1 mL was injected. The molecular weight was determined as a converted value using standard PEO / PEG (Agilent Technologies).

[0332] [Table 1]

[0333] Table 1

[0334]

[0335] <Preparation of dispersion composition>

[0336] (Example 1-1)

[0337] According to the materials and compositions shown in Table 2, materials were added in sequence, and a CNT dispersion composition was prepared according to the following method.

[0338] 1960.8 parts of ion exchange water, 18 parts of the dispersant (B-1) and 1.2 parts of the basic compound (D) were added to a stainless steel container, and stirred with a disperser until the mixture became uniform.

[0339] After that, 20 parts of CNT (TUBALL) were added while stirring with a disperser, and a square hole high shear screen was installed on a high shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,000 rpm until the whole became uniform and the dispersed particle size obtained by the particle size meter became 250 μm or less. At this time, the dispersed particle size confirmed by the particle size meter was 180 μm.

[0340] Next, the dispersion was supplied from the stainless steel container to a high pressure homogenizer (Star Burst Labo HJP-17007, manufactured by SUGINO MACHINE) via a pipe, and a flow-through dispersion treatment was performed until the particle size D 50 The particle size is 0.3 μm to 7 μm. The number of passes is 50, and the particle size D 50 is 1.5μm.

[0341] The dispersion treatment was carried out using a single nozzle chamber at a nozzle diameter of 0.20 mm and a pressure of 150 MPa, to obtain a carbon nanotube dispersion composition 1 having a carbon nanotube (A) content of 1.0 mass % TUBALL, a dispersant (B-1) content of 0.90 mass % and a basic compound (D) content of 0.06 mass % (Na2CO3) (D).

[0342] (Example 1-2 to Example 1-28, Example 1-31 to Example 1-33, Comparative Example 1-1 to Comparative Example 1-5)

[0343] According to the materials and composition shown in Table 2, the dispersion treatment was carried out in the same manner as in Example 1-1 until the particle size D 50 Each dispersion composition (dispersion composition 2 to dispersion composition 28, dispersion composition 31 to dispersion composition 33, and comparative dispersion composition 1 to comparative dispersion composition 5) was obtained until the particle size was 0.3 μm to 7 μm.

[0344] Regarding the dispersion conditions, the particle size D at the time point when the 20-pass dispersion treatment was performed was 50 If the particle size is 7 μm or more, perform the dispersion treatment twice more and measure again. Repeat the above operation until the particle size D 50 The number of passes was controlled until the particle size became 7 μm or less, and the particle size D was adjusted. 50 0.3μm~7μm.

[0345] (Example 1-29)

[0346] According to the composition shown in Table 2, a dispersant (B-1), an alkaline compound (D-1) and ion exchange water were placed in a glass bottle (M-225, manufactured by Kashiwa Glass Co., Ltd.), and after being fully mixed and dissolved or mixed, CNTs were added, and zirconium oxide beads (bead diameter 0.5 mmφ) were used as a medium. The glass bottle was cooled every two hours using a paint conditioner while being dispersed for a total of 8 hours to obtain a carbon nanotube dispersion composition 29. Particle size D 50 It is 3.8μm.

[0347] (Example 1-30)

[0348] According to the composition shown in Table 2, a dispersant (B-1), a conductive material and a small amount of ion exchange water were charged into a lab plastic mill (Labo Plastomill) (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.), and dispersed for 3 hours. Then, the mixture was transferred to a stainless steel container, and the remaining ion exchange water and the alkaline compound (D-1) were added. A square hole high shear screen was installed on a high shear mixer (L5M-A, manufactured by SILVERSON), and the mixture was dispersed in batches at a speed of 8,000 rpm until the whole became uniform and the dispersed particle size obtained by a particle size meter became 250 μm or less, thereby obtaining a carbon nanotube dispersed composition 30. At this time, the dispersed particle size confirmed by the particle size meter was 80 μm, and the particle size D 50 It is 6.0μm.

[0349] (Example 1-34 to Example 1-36)

[0350] According to the compositions shown in Table 2, carbon nanotube dispersion compositions 34 to 36 were obtained in the same manner as in Example 1-1.

[0351] <Measurement and evaluation of physical properties of dispersion composition>

[0352] The physical property values ​​of the dispersion composition were measured and the storage stability was evaluated by the following methods. The results are shown in Table 2.

[0353] (Particle size D of the dispersion composition 50 Determination method of

[0354] Particle size D when volume accumulation is 50% 50 The particle size distribution was measured using a laser diffraction particle size distribution analyzer (Partical LA-960V2, manufactured by HORIBA).

[0355] The operating conditions of circulation / ultrasonic waves are set to circulation speed: 3, ultrasonic intensity: 7, ultrasonic time: 1 minute, stirring speed: 1, stirring mode: continuous. In addition, ultrasonic waves are operated in the exhaust gas with an ultrasonic intensity of 7 and an ultrasonic time of 5 seconds. The refractive index of the particles of the carbon-based conductive material is set to 1.9, and the shape is set to be non-spherical. The refractive index of the solvent is set to 1.333. During the measurement, the concentration of the CNT dispersion composition is diluted in such a way that the transmittance value is within the range of 50% to 85%. The particle diameter standard is set to volume.

[0356] (pH measurement method of dispersion composition)

[0357] The pH of the sample for pH measurement was measured at a temperature of 25° C. using a table-top pH meter (Seven Compact S200 Expert Pro, manufactured by METTLER TOLEDO).

[0358] (Complex elastic modulus and phase angle of dispersion composition)

[0359] The complex elastic modulus and phase angle of the dispersed composition were determined by dynamic viscoelasticity measurement at 25°C and a frequency of 1 Hz at a strain rate ranging from 0.01% to 5%, using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific Inc.) with a cone having a diameter of 35 mm and a 2° angle.

[0360] The complex elastic modulus is preferably 5 Pa or more and less than 300 Pa, and more preferably 10 Pa or more and less than 60 Pa.

[0361] The phase angle is preferably 3° or more and less than 60°, and more preferably 10° or more.

[0362] The lower the complex elastic modulus of the dispersion composition is and the closer the phase angle of the dispersion composition is to 90°, the better the fluidity is.

[0363] Evaluation criteria for complex elastic modulus

[0364] 1: 300Pa or more but less than 5Pa

[0365] 2: 60Pa or more and less than 300Pa

[0366] 3: 10Pa or more and less than 60Pa

[0367] 4: 5Pa or more but less than 10Pa

[0368] Evaluation criteria for phase angle

[0369] 1: 10° or more and less than 60°

[0370] 2: 3° or more and less than 10°

[0371] 3: Less than 3°

[0372] (Method for evaluating storage stability of dispersion composition)

[0373] Regarding the evaluation of storage stability, the presence or absence of fluidity of the dispersed composition after being stored at 40°C was judged. The judgment method is as follows. Using a cone with a diameter of 35 mm and 2°, and using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific Co., Ltd.), at 25°C and a frequency of 1 Hz, a dynamic viscoelasticity measurement was performed with a strain rate of 0.01% to 5%, thereby evaluating the complex elastic modulus. If it is an evaluation benchmark of ◎~△, it can be practical.

[0374] Evaluation benchmark

[0375] ◎: Less than 300Pa even after one month (excellent)

[0376] ○: Reached 300 Pa after one month (good)

[0377] △: Reach 300Pa after one week (possible)

[0378] ×: Reach 300Pa after one day

[0379] [Table 2-1]

[0380] Table 2-1

[0381]

[0382] [Table 2-1A]

[0383] Table 2-1 (continued)

[0384]

[0385] [Table 2-2]

[0386] Table 2-2

[0387]

[0388] [Table 2-2A]

[0389] Table 2-2 (continued)

[0390]

[0391] <Production and evaluation of secondary batteries>

[0392] <Production of negative electrode composite slurry and negative electrode>

[0393] (Example 2-1)

[0394] After adding the dispersion composition (dispersion composition 1), thickener and water to a plastic container, stir at 2,000 rpm for 30 seconds using a rotation / revolution mixer (Defoaming Stirring Taro, ARE-310 manufactured by Thinky). Then, add artificial graphite and silicon (artificial graphite: silicon = 9:1 (mass ratio)) as negative electrode active materials, and stir at 2,000 rpm for 150 seconds using the rotation / revolution mixer. Then, add styrene butadiene rubber (SBR), and stir at 2,000 rpm for 30 seconds using the rotation / revolution mixer to obtain a negative electrode composite slurry.

[0395] In addition, regarding the active material, CNT, dispersant, thickener and SBR in the negative electrode composite material slurry, when the total of these is set to 100% by mass, they are prepared in a manner to become the preparation amount (mass %) of Table 3, and the amount of water is adjusted in a manner such that the non-volatile component of the negative electrode composite material slurry becomes 45%. The preparation amount in Table 3 represents the net content rate (non-volatile component mass %) of each component in the negative electrode composite material slurry.

[0396] After applying the obtained negative electrode composite material slurry on a copper foil with a thickness of 20 μm using an applicator, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to prepare an electrode film. After that, the electrode film was rolled using a roller press (manufactured by Thank-Metal, 3t hydraulic roller press) to obtain a negative electrode (negative electrode 1). In addition, the unit area weight of each unit of the composite material layer is 10 mg / cm 2 The density of the composite material layer after calendering is 1.6g / cm 3 .

[0397] In addition, the raw materials are as follows.

[0398] Artificial graphite: CGB-20 (manufactured by Nippon Graphite Industries), non-volatile content 100%

[0399] Silicon: Silicon monoxide (manufactured by Osaka Titanium Technologies, SILICON MONOOXIDE SiO 1.3C 5μm, non-volatile content 100%)

[0400] Thickener: CMC (carboxymethyl cellulose, #1190 (manufactured by Daicel Finechem), non-volatile matter 100%)

[0401] ·Binder: SBR (styrene butadiene rubber, TRD2001 (manufactured by JSR Corporation), non-volatile content 48%)

[0402] (Example 2-2 to Example 2-36)

[0403] Except that the dispersion composition was changed to each dispersion composition (dispersion composition 2 to dispersion composition 36) shown in Table 3 and the composition ratio was changed to that shown in Table 3, the negative electrode composite material slurry was manufactured by the same method as in Example 2-1, and negative electrodes 2 to negative electrodes 36 were obtained in the same manner.

[0404] (Comparative Example 2-1 to Comparative Example 2-5)

[0405] Except that the dispersion composition was changed to each dispersion composition shown in Table 3 (Comparative dispersion composition 1 to Comparative dispersion composition 5), a comparative negative electrode composite material slurry was prepared by the same method as in Example 2-1, and comparative negative electrodes 1 to comparative negative electrodes 5 were obtained in the same manner.

[0406] (Reference Example 2-1: Preparation of Standard Negative Electrode)

[0407] Into a 150 ml plastic container, 0.5% by mass of acetylene black (DENKA BLACK (registered trademark) HS-100, manufactured by DENKA Co., Ltd.), 1% by mass of MAC500LC (carboxymethylcellulose sodium salt Sunrose special type MAC500LC, manufactured by Nippon Paper, nonvolatile content 100%), and 98.4% by mass of water were added, and then stirred at 2,000 rpm for 30 seconds using a rotation / revolution mixer (Defoaming Stirring Taro, ARE-310 manufactured by Thinky Co., Ltd.). Furthermore, 97% by mass of artificial graphite (CGB-20, manufactured by Nippon Graphite Co., Ltd.) as an active material was added, and stirred at 2,000 rpm for 150 seconds using a rotation / revolution mixer (Defoaming Stirring Taro, ARE-310 manufactured by Thinky Co., Ltd.). Then, 3.1% by mass of SBR (styrene butadiene rubber, TRD2001, non-volatile content 48%, manufactured by JSR) was added, and the mixture was stirred at 2,000 rpm for 30 seconds using a rotation / revolution mixer (Defoaming Stirring Taro, ARE-310 manufactured by Thinky) to obtain a standard negative electrode composite slurry. The non-volatile content of the standard negative electrode composite slurry was set to 50% by mass.

[0408] The standard negative electrode composite material slurry was applied onto a copper foil with a thickness of 20 μm, which became a current collector, using an applicator, and then dried in an electric oven at 80°C ± 5°C for 25 minutes to adjust the unit area weight per unit area of ​​the electrode to 10 mg / cm 2Furthermore, the electrode composite material layer was rolled using a roller press (manufactured by Thank-Metal, 3 t hydraulic roller press) to obtain a density of 1.6 g / cm 3 The standard negative electrode.

[0409] [Table 3]

[0410] Table 3

[0411]

[0412] <Production of composite material slurry for positive electrode and positive electrode> (Example 3-1)

[0413] After adding the dispersion composition (dispersion composition 1), the thickener and water to the plastic container, the mixture was stirred at 2,000 rpm for 30 seconds using a rotation / revolution mixer (Taro Defoaming Stirring, ARE-310 manufactured by Thinky), and then lithium iron phosphate (LiFePO4, LFP) as a positive electrode active material was added, and the mixture was stirred at 2,000 rpm for 150 seconds using a rotation / revolution mixer (Taro Defoaming Stirring, ARE-310 manufactured by Thinky). Furthermore, polytetrafluoroethylene (PTFE) as a binder was added, and the mixture was stirred at 2,000 rpm for 30 seconds using a rotation / revolution mixer (Taro Defoaming Stirring, ARE-310 manufactured by Thinky) to obtain a composite material slurry for the positive electrode.

[0414] In addition, regarding the active material, CNT, dispersant, thickener and binder (PTFE) in the positive electrode composite material slurry, when the total of these non-volatile components is set to 100% by mass, the amount of water is adjusted in such a way that the non-volatile component of the positive electrode composite material slurry becomes 65%. The amount of water in Table 4 represents the net content (non-volatile component mass %) of each component in the positive electrode composite material slurry.

[0415] After applying the positive electrode composite material slurry on an aluminum foil with a thickness of 20 μm using an applicator, the electrode film was dried in an electric oven at 120°C ± 5°C for 25 minutes to produce an electrode film. After that, the electrode film was rolled using a roller press (manufactured by Thank-Metal, 3t hydraulic roller press) to obtain a positive electrode (positive electrode 1). In addition, the unit area weight of each unit of the composite material layer is 20 mg / cm 2 The density of the composite material layer after calendering is 2.1g / cc.

[0416] In addition, the raw materials are as follows.

[0417] ·LFP: Lithium iron phosphate HED (registered trademark) LFP-400 (manufactured by BASF, non-volatile components 100%)

[0418] ·Binder: PTFE (polytetrafluoroethylene, polyflon PTFED-210C (manufactured by Daikin Industries, Ltd., non-volatile content 60%))

[0419] Thickener: CMC (carboxymethylcellulose #1190 (manufactured by Daicel Finechem), non-volatile matter 100%)

[0420] (Example 3-2 to Example 3-36)

[0421] Positive Electrodes 2 to 36 were obtained by the same method as in Example 3-1 except that the conductive material dispersion was changed to each dispersion composition shown in Table 4 (dispersion composition 2 to dispersion composition 36).

[0422] (Comparative Example 3-1 to Comparative Example 3-5)

[0423] Comparative positive electrodes 1 to 5 were obtained by the same method as in Example 3-1 except that the conductive material dispersion was changed to each dispersion composition shown in Table 4 (Comparative dispersion composition 1 to Comparative dispersion composition 5).

[0424] (Reference Example 3-1: Preparation of Standard Positive Electrode)

[0425] 92 mass % of LFP (HED (trademark) LFP-400, manufactured by BASF, non-volatile content 100%) as a positive electrode active material, 4 mass % of acetylene black (DENKA BLACK (registered trademark) HS-100, manufactured by DENKA, non-volatile content 100%), and 1.6 mass % of a thickener (carboxymethylcellulose #1190, manufactured by Daicel Finechem, non-volatile content 100%) were added to a plastic container and mixed with a spatula until uniform. Then, 20.5 mass % of water was added and stirred at 2,000 rpm for 30 seconds using a rotation / revolution mixer (Defoaming Stirring Taro, manufactured by Thinky, ARE-310). Afterwards, the mixture in the plastic container was mixed with a scraper until it became uniform, and PTFE (manufactured by Daikin Industries, Ltd., non-volatile component 60% by mass) was added using a rotation / revolution mixer, and stirred at 2,000 rpm for 30 seconds. Then, 11.2% by mass of water was added, and the rotation / revolution mixer was used to stir at 2,000 rpm for 30 seconds. Finally, a high-speed stirrer was used to stir at 3,000 rpm for 10 minutes to obtain a standard positive electrode composite slurry.

[0426] After applying the standard positive electrode composite material slurry on an aluminum foil with a thickness of 20 μm using an applicator, it was dried in an electric oven at 120°C ± 5°C for 25 minutes to make an electrode film. After that, the electrode film was rolled using a roller press (manufactured by Thank-Metal, 3t hydraulic roller press) to obtain a standard positive electrode. In addition, the unit area weight of each unit of the electrode composite material layer is 20 mg / cm 2 The density of the electrode composite material layer after calendering is 2.1 g / cc.

[0427] [Table 4]

[0428] Table 4

[0429]

[0430] (Manufacturing of Secondary Batteries)

[0431] The standard positive electrode and negative electrode or comparative negative electrode described in Table 5, or the positive electrode or comparative positive electrode and standard negative electrode described in Table 6 were punched out into 50 mm × 45 mm and 45 mm × 40 mm, respectively, and the punched positive electrode and negative electrode and the separator (porous polypropylene film) inserted therebetween were inserted into an aluminum laminate bag and dried in an electric oven at 70°C for 1 hour. After that, 2 mL of an electrolyte solution (a mixed solvent prepared by mixing ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1, and then adding 1% by mass of vinylene carbonate as an additive relative to 100% by mass of the mixed solvent, and dissolving LiPF6 at a concentration of 1M) was injected into a glove box filled with argon gas, and then the aluminum laminate bag was sealed to prepare secondary batteries.

[0432] <Evaluation of Secondary Batteries>

[0433] The obtained secondary batteries were evaluated by the following methods. The results are shown in Tables 5 and 6.

[0434] (Rate characteristics evaluation method of secondary battery)

[0435] The method is implemented in the same manner as in paragraph 0178 of Japanese Patent No. 7107413. If the evaluation criteria are ◎ to △, the method is practically applicable.

[0436] Evaluation criteria for rate characteristics

[0437] ◎: 90% or more (excellent)

[0438] ○: 85% or more and less than 90% (good)

[0439] △: 80% or more and less than 85% (acceptable)

[0440] ×: Less than 80%

[0441] (Evaluation method of cycle characteristics of secondary batteries)

[0442] The method is implemented in the same manner as in paragraph 0179 of Japanese Patent No. 7107413. If the evaluation criteria are ◎ to △, the method is practically applicable.

[0443] Evaluation criteria for cycle characteristics

[0444] ◎: 90% or more (excellent)

[0445] ○: 80% or more and less than 90% (good)

[0446] △: 70% or more and less than 80% (acceptable)

[0447] ×: Less than 70%

[0448] [Table 5]

[0449] Table 5

[0450]

[0451] [Table 6]

[0452] Table 6

[0453]

[0454] From Table 2, Table 5, and Table 6, it can be seen that for the polymer containing 80% by mass or more of a carboxyl group-containing structural unit and a basic compound and having a particle size D 50 It was confirmed that the dispersion composition adjusted to an appropriate pH can achieve a balance among fluidity, storage stability, and battery performance.

[0455] When the particle size D of the carbon nanotube dispersion composition is 50 When the diameter is adjusted to 0.3 μm to 7.0 μm, regardless of the type of carbon nanotubes or the type of basic compound, dispersion using a polymer having a carboxyl group-containing structural unit and having a weight average molecular weight of 5,000 to 360,000, i.e., a dispersant (B), can be applied by adjusting the pH.

[0456] As in the comparative example, when the pH is low or when a polymer with a low content of structural units containing carboxyl groups is used, the fluidity is poor due to insufficient electrical repulsion of the carboxyl groups, and when the pH is high, the affinity of the polymer and the carbon nanotubes is reduced, resulting in thickening caused by the aggregation of the carbon nanotubes. When the dispersant is a polymer with a small molecular weight, the fluidity is poor due to insufficient steric repulsion, and when it is a polymer with a large molecular weight, the viscosity of the polymer itself causes thickening.

[0457] As mentioned above, although the present invention has been described with reference to the embodiment, the present invention is not limited to the above contents. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the invention.

Claims

1. A carbon nanotube dispersion composition, characterized in that It comprises carbon nanotubes (A), a dispersant (B) and a solvent (C), Particle diameter D at 50% volume accumulation obtained by laser diffraction particle size distribution measurement 50 0.3μm~7μm, The carbon nanotube dispersion composition satisfies the following (1) and (2); (1) the dispersant (B) is a polymer having a weight average molecular weight of 5,000 or more and 360,000 or less and having a carboxyl group-containing structural unit derived from at least one of (meth)acrylic acid and a (meth)acrylate having a carboxyl group, The content of the carboxyl group-containing structural unit is 80% by mass or more based on the mass of the polymer; (2) When the particle size D of the carbon nanotube dispersion composition at the time of volume accumulation 50% is obtained by laser diffraction particle size distribution measurement, 50 When X[μm] and pH is Y, X and Y satisfy the following (Formula a) and (Formula b); (Formula a) Y≧-0.149X+4.545 (Formula b) Y≦-0.134X+5.

140. 2 . The carbon nanotube dispersion composition according to claim 1 , further comprising a basic compound (D). 3 . The carbon nanotube dispersion composition according to claim 1 , wherein a phase angle at 25° C. and 1 Hz obtained by dynamic viscoelasticity measurement is 3° or more and less than 60°. 4 . The carbon nanotube dispersion composition according to claim 1 , wherein the complex elastic modulus at 25° C. and 1 Hz obtained by dynamic viscoelasticity measurement is 5 Pa or more and less than 300 Pa. 5 . The carbon nanotube dispersion composition according to claim 1 , wherein the content of the dispersant (B) is 15 to 160 parts by mass based on 100 parts by mass of the carbon nanotubes (A). 6 . The carbon nanotube dispersion composition according to claim 1 , wherein the content of the dispersant (B) is 15 to 90 parts by mass based on 100 parts by mass of the carbon nanotubes (A).

7. The carbon nanotube dispersion composition according to any one of claims 1 to 6, wherein the carbon nanotube (A) has a Buerter specific surface area of ​​100 m2 as measured by nitrogen adsorption. 2 / g and above 1200m 2 / g or less. 8 . The carbon nanotube-dispersed composition according to claim 1 , wherein the carboxyl group-containing structural unit is a structural unit derived from (meth)acrylic acid. 9 . A composite material slurry comprising the carbon nanotube dispersion composition according to claim 1 and an active substance.

10. An electrode membrane formed from the composite material slurry according to claim 9.

11. A secondary battery comprising a positive electrode and a negative electrode, wherein: At least one of the positive electrode and the negative electrode has the electrode film according to claim 10 .

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