Carbon nanotube dispersion composition, carbon nanotube resin composition, composite slurry, electrode film, and nonaqueous electrolyte secondary battery

Abstract

The invention provides a carbon nanotube dispersion composition capable of improving battery performance. Provided is a carbon nanotube dispersion composition containing carbon nanotubes, a dispersant, and a solvent, and satisfying the following conditions (1) and (2). (1) The average outer diameter of the carbon nanotubes, as calculated from an SEM image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition, is 15-50 nm (inclusive). (2) When a pixel group of an SEM image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition is carbon nanotubes, and a value obtained by dividing the distance (absolute maximum length) between two farthest points by the length (skeleton length) of a free curve is linear, the carbon nanotubes having a skeleton length of 1 [mu] m or more have a maximum length (absolute maximum length) of 1 [mu] m or more and a maximum length (absolute maximum length) of 1 [mu] m or more. The ratio of the number of carbon nanotubes having a linearity of 0.9 or more is 40% or more and 90% or less.

Description

Technical Field

[0001] The present invention relates to a carbon nanotube dispersion composition, a carbon nanotube resin composition, a composite material slurry, an electrode film, and a non-aqueous electrolyte secondary battery. Background Art

[0002] With the popularity of electric vehicles and the miniaturization, lightness and high performance of portable devices, secondary batteries with high energy density and high capacity are required. In this context, non-aqueous electrolyte 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.

[0003] As the negative electrode material of these lithium ion secondary batteries, a carbon material represented by graphite is used. Carbon material is a low potential close to lithium (Li), and the charge and discharge capacity per unit mass is large. However, in these electrode materials, the charge and discharge capacity per mass reaches a level close to the theoretical value, and the energy density per mass of the battery is close to the limit. Therefore, from the perspective of improving the utilization rate as an electrode, attempts are being made to reduce conductive additives and adhesives that do not contribute to the discharge capacity.

[0004] As conductive aids, carbon black, Ketjen black, fullerene, graphene, and fine carbon fibers such as carbon nanotubes and carbon nanofibers are used. In particular, carbon nanotubes as a kind of fine carbon fibers are used in large quantities. For example, by adding carbon nanotubes to the negative electrode containing graphite and silicon, the reduction of electrode resistance, the improvement of the load resistance of the battery, the improvement of the strength of the electrode, and the improvement of the expansion and contraction of the electrode are achieved, thereby improving the cycle life of the lithium ion secondary battery (for example, with reference to patent document 1, patent document 2, and patent document 3). In addition, research on reducing electrode resistance by adding carbon nanotubes to the positive electrode has also been carried out (for example, with reference to patent document 4).

[0005] Patent document 5 discloses that in order to obtain an electrode film with excellent conductivity and adhesion, carbon nanotubes are specifically specified by the pH, Brunauer-Emmett-Teller (BET) specific surface area, and average fiber length of the carbon nanotube aqueous dispersion. Patent document 6 discloses that in order to obtain an electrode film with excellent conductivity and adhesion, a carbon nanotube dispersion is specifically specified by the average outer diameter, BET specific surface area, fiber length, complex elastic modulus, and phase angle of the carbon nanotubes. Patent document 7 discloses that in order to obtain a multilayer carbon nanotube aggregate with good dispersibility in a resin, a solvent, etc., the average aspect ratio, bending degree, size of secondary particles of the multilayer carbon nanotubes, size of secondary particles of the inorganic oxide microparticles, and volume density are specifically specified.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Laid-Open No. 4-155776

[0009] Patent Document 2: Japanese Patent Laid-Open No. 4-237971

[0010] Patent Document 3: Japanese Patent Application Publication No. 2004-178922

[0011] Patent Document 4: Japanese Patent Application Publication No. 2011-70908

[0012] Patent Document 5: Japanese Patent No. 6961152

[0013] Patent Document 6: Japanese Patent No. 6801806

[0014] Patent Document 7: Japanese Patent Application Publication No. 2012-082077 Summary of the invention

[0015] Problems to be solved by the invention

[0016] Patent Documents 5 and 6 disclose that a nonaqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics is provided by obtaining an electrode film having excellent conductivity and adhesion. On the other hand, further improvement in battery performance is expected by specifying a more microscopic dispersion state of carbon nanotubes in the electrode film.

[0017] According to the technology disclosed in Patent Document 7, it is disclosed that the multilayer carbon nanotubes are bent to a certain extent to prevent aggregation when added to a resin, etc., so the multilayer carbon nanotubes are preferably bent in a shape compared to multilayer carbon nanotubes with high linearity. On the other hand, in order to ensure a conductive path between multiple particles of the active material in the electrode film and improve battery performance, research is also expected from other aspects.

[0018] One of the objects of the present disclosure is to provide a carbon nanotube dispersion composition, a carbon nanotube resin composition, and a composite material slurry that can improve battery performance, as well as an electrode film and a non-aqueous electrolyte secondary battery obtained using these.

[0019] Technical means of solving problems

[0020] Some embodiments of the present disclosure relate to the following contents. However, the present invention is not limited to the following contents, and may include various embodiments.

[0021] [1] A carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and a solvent, and satisfying the following (1) and (2).

[0022] (1) The average outer diameter of the carbon nanotubes calculated from a scanning electron microscope (SEM) image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition is 15 nm or more and 50 nm or less.

[0023] (2) When the pixel group of the SEM image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition is set as the carbon nanotube, and the value obtained by dividing the distance between the two farthest points (absolute maximum length) by the length of the free curve (skeleton length) is set as the linearity, for carbon nanotubes with a skeleton length of more than 1 μm, the number ratio of carbon nanotubes with a linearity of more than 0.9 is more than 40% and less than 90%.

[0024] [2] The carbon nanotube dispersion composition according to [1], wherein (3) in the Raman spectrum of the coating film of the carbon nanotube dispersion composition, the wavelength at 1560 cm -1 ~1600cm -1 The maximum peak intensity in the range of 1310 cm -1 ~1350cm -1 When the maximum peak intensity in the range of is defined as D, the G / D ratio is 1.0 to 20.0.

[0025] [3] The carbon nanotube dispersion composition according to [1] or [2], wherein (4) after freeze-drying the carbon nanotube dispersion composition, the BET specific surface area of ​​the powder passing through a 60 μm sieve relative to the mass of the carbon nanotubes is 50 m 2 / g~130m 2 / g.

[0026] [4] The carbon nanotube dispersion composition according to any one of [1] to [3], wherein (5) the complex elastic modulus at 25°C and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is 0.1 Pa or more and 200 Pa or less.

[0027] [5] The carbon nanotube dispersion composition according to any one of [1] to [4], wherein (6) the phase angle at 25°C and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is 3° or more and 60° or less.

[0028] [6] A carbon nanotube resin composition comprising: the carbon nanotube dispersion composition according to any one of [1] to [5], and a binder.

[0029] [7] A composite material slurry comprising: the carbon nanotube dispersion composition according to any one of [1] to [5], a binder, and an active material.

[0030] [8] An electrode film, which is a coating film of a composite material slurry, wherein the composite material slurry comprises the carbon nanotube dispersion composition according to any one of [1] to [5], a binder, and an active material.

[0031] [9] A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises the electrode film according to [8].

[0032] Effects of the Invention

[0033] According to one embodiment of the present disclosure, a carbon nanotube dispersion composition, a carbon nanotube resin composition, and a composite material slurry that can improve battery performance, and an electrode film and a non-aqueous electrolyte secondary battery obtained using these can be provided. DETAILED DESCRIPTION

[0034] Hereinafter, a carbon nanotube dispersion composition, and a resin composition, a composite material slurry, an electrode film, and a non-aqueous electrolyte secondary battery containing the same will be described in detail using several embodiments of the present disclosure. However, the present disclosure is not limited to these embodiments, and various modifications are possible.

[0035] In the present disclosure, carbon nanotubes are sometimes referred to as "CNTs" and carbon nanotube dispersion compositions are sometimes referred to as "CNT dispersion compositions". In addition, in the present disclosure, SEM images refer to images taken using a scanning electron microscope. Scanning electron microscopes are also simply referred to as "SEMs".

[0036] The inventors have found that by making the average outer diameter and linearity index of carbon nanotubes satisfy the specified range when contained in a carbon nanotube dispersion composition, one (i.e., each) carbon nanotube is in contact with multiple particles of an active material (at a higher ratio) in an electrode film, and the conductivity between the particles of the active material is improved, thereby providing a secondary battery with excellent rate characteristics and cycle characteristics. The inventors have completed the present invention based on the above findings.

[0037] As an electrode material, whether it is a negative electrode or a positive electrode, multiple particles of active material can be electrically connected by a carbon nanotube to improve conductivity. In the case where the carbon nanotube has linearity, one carbon nanotube can contact more particles of active material, which can help conductivity. In this case, a small amount of carbon nanotubes can be expected to significantly help conductivity.

[0038] For example, the electrode film can reduce the volume of the dispersant and binder to increase the packing density of the active material, but the packing density of the active material can be further increased by further reducing the volume by reducing the amount of carbon nanotubes themselves.

[0039] In the negative electrode, when a carbon-based active material is used, a carbon nanotube can be used to electrically connect multiple particles of the carbon-based active material to improve conductivity. In addition, when a silicon-based active material is used in the negative electrode, there is a tendency for volume changes to occur due to charging and discharging. If volume changes occur in the negative electrode, the electrical connection between the particles of the active material is blocked, and sometimes some particles of the active material are electrically isolated. Regarding linear carbon nanotubes, even if volume changes occur in the active material particles, it is easier to maintain contact with multiple particles of the active material due to its linearity, which can prevent the blocking of the conductive path and inhibit the reduction of battery capacity.

[0040] Similarly, in the positive electrode, one carbon nanotube can electrically connect a plurality of particles of the active material to ensure a conductive path, and therefore, even a small amount of carbon nanotubes can be expected to significantly contribute to conductivity.

[0041] <Carbon nanotube dispersion composition>

[0042] One embodiment relates to a carbon nanotube dispersion composition. The carbon nanotube dispersion composition includes at least carbon nanotubes, a dispersant, and a solvent.

[0043] The carbon nanotube dispersion composition is characterized by satisfying the following (1) and (2).

[0044] (1) The average outer diameter of the carbon nanotubes calculated from an SEM image of the carbon nanotubes contained in the carbon nanotube dispersion composition is 15 nm or more and 50 nm or less.

[0045] (2) When the pixel group of the SEM image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition is set as the carbon nanotubes (i.e., the carbon nanotubes are pixelated in the SEM image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition, or in other words, the pixel group corresponding to the carbon nanotubes is set as a proxy), and the value obtained by dividing the distance between the two farthest points (absolute maximum length) by the length of the free curve (skeleton length) is set as the linearity, for carbon nanotubes with a skeleton length of 1 μm or more, the number ratio of carbon nanotubes with a linearity of 0.9 or more is 40% or more and 90% or less.

[0046] Hereinafter, the index specified in (2) above is also referred to as a linearity index.

[0047] By making the average outer diameter of carbon nanotubes in a state of being contained in a carbon nanotube dispersion composition satisfy a predetermined range and specifying a linearity index, excellent battery performance can be provided in a secondary battery using the carbon nanotube dispersion composition.

[0048] Although the above reasons are not limited by theory, it is believed that by satisfying conditions (1) and (2), the linearity of the carbon nanotubes is maintained in the electrode film, and the carbon nanotubes are connected to multiple particles of the active material at a higher ratio one by one, which can improve the conductivity. The number of particles of the active material connected to one carbon nanotube only needs to be 2 or more, and more preferably 3 or more. In addition, not all carbon nanotubes need to be connected to multiple particles of the active material, and only a part of the carbon nanotubes need to be connected to multiple particles of the active material.

[0049] In condition (1), the average outer diameter of the carbon nanotubes is preferably 15 nm or more, more preferably more than 17 nm, more preferably 19 nm or more, and further preferably 21 nm or more. Within these ranges, it has bending resistance to stress, and can maintain a conductive path distributed between active materials that undergo volume changes as lithium ions are absorbed and released. In addition, there are also the following aspects: carbon nanotubes with an average outer diameter of less than 15 nm are difficult to obtain in a manner having physical property values ​​within the appropriate range of the present disclosure according to their manufacturing method. For example, in a carbon nanotube dispersion composition, it is difficult to synthesize and obtain a carbon nanotube raw material having an average outer diameter of less than 15 nm and having the linearity index of condition (2). In addition, when using a carbon nanotube raw material with an average outer diameter of more than 15 nm, a method for manufacturing a carbon nanotube dispersion composition in a manner having the linearity index of condition (2) in a carbon nanotube dispersion composition is not yet known.

[0050] In condition (1), the average outer diameter of the carbon nanotubes is preferably less than 50 nm, more preferably less than 40 nm, and further preferably less than 30 nm. Within these ranges, the number of fibers per mass of the carbon nanotubes can be increased, the number of active materials to which the carbon nanotubes are distributed can be increased, and the battery performance can be further improved. In addition, if the average outer diameter of the carbon nanotubes is in the range of less than 50 nm, the carbon nanotubes themselves become low resistance, which can further improve the conductivity. Thus, the rate characteristics can be further improved in the secondary battery. Furthermore, since the carbon nanotubes of this embodiment have linearity, they can have high conductivity, and contact with multiple particles of the active material in the electrode film to ensure a conductive path, which helps to improve the conductivity.

[0051] For example, the average outer diameter of the carbon nanotubes may be 15 nm to 50 nm, 15 nm to 40 nm, or 15 nm to 30 nm, or 17 nm to 40 nm, 19 nm to 30 nm, or 21 nm to 30 nm.

[0052] In condition (2), the linearity index of the carbon nanotubes is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. A carbon nanotube group with a high linearity index can be connected to multiple particles of the active material at a higher ratio in the electrode film, which can contribute to high conductivity in the secondary battery.

[0053] In the condition (2), the linearity index of the carbon nanotube is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less.

[0054] If the linearity index of carbon nanotubes increases, the carbon nanotubes themselves tend to become hard, and the carbon nanotube fibers may break when the carbon nanotube dispersion composition is dispersed during the period of providing the electrode film. In such a case, the number of particles of the active material that can be contacted by one carbon nanotube in the electrode film is reduced, and sometimes the conductivity cannot be fully obtained in the secondary battery.

[0055] For example, the linearity index of the carbon nanotubes may be 40% to 90%, 50% to 90%, 60% to 90%, 50% to 80%, 50% to 70%, or 60% to 70%.

[0056] In the present disclosure, the average outer diameter of carbon nanotubes in a carbon nanotube dispersion composition is measured by the following procedure.

[0057] A sample capable of SEM observation of individual carbon nanotubes was prepared using the carbon nanotube dispersion composition. 300 carbon nanotubes were randomly selected from the SEM image of the sample, and the number-average average outer diameter was calculated. Specifically, the following process was followed.

[0058] Sample preparation: The CNT dispersion composition was diluted with a solvent to a CNT concentration of 0.048 mass %. The solvent used to prepare the CNT dispersion composition was used. The diluted dispersion composition was sprayed onto a mica substrate in an amount of several μL and dried on a hot plate at 100°C to prepare a substrate for observing the average outer diameter of CNTs.

[0059] Measurement method: Observe and photograph the carbon nanotubes using a scanning electron microscope. Next, select any 300 carbon nanotubes from the observation photograph and measure their outer diameters. Next, calculate the average outer diameter (nm) of the carbon nanotubes by averaging the outer diameters.

[0060] Specifically, the method for measuring the average outer diameter follows the measuring method of Examples.

[0061] In the present disclosure, the method for measuring the linearity index of carbon nanotubes in the carbon nanotube dispersion composition is a numerical value measured by the following procedure.

[0062] A sample capable of SEM observation of individual carbon nanotubes was prepared using a carbon nanotube dispersion composition. A total of 1,000 to 3,000 carbon nanotubes were selected from the SEM images of the sample, and the absolute maximum length and skeleton length of each carbon nanotube were measured. The number of carbon nanotubes with a skeleton length of 1 μm or more was measured, and the linearity and linearity index were calculated. Specifically, the following process was followed.

[0063] Sample preparation: The CNT dispersion composition was diluted with a solvent to a CNT concentration of 0.048 mass %. The solvent used to prepare the CNT dispersion composition was used. The diluted dispersion composition was sprayed onto a mica substrate in an amount of several μL and dried on a hot plate at 100°C to prepare a substrate for observing the CNT linearity index.

[0064] Measurement method: Obtain an SEM image of the sample substrate. At this time, set it in such a way that the shapes of 50 to 200 carbon nanotubes are observed in one field of view. Take the SEM image under the condition of 4.63nm per pixel. In addition, an error range of 4.63nm±10% is allowed under the shooting conditions. Move the field of view until a total of 1000 to 3000 carbon nanotubes can be observed and obtain the SEM image.

[0065] Software: The SEM image was analyzed using image analysis software "WinROOF2015" (manufactured by Mitani Shoji) and the absolute maximum length and skeleton length of one carbon nanotube were calculated. The linearity was calculated according to the following formula.

[0066] Linearity = absolute maximum length / frame length

[0067] The absolute maximum length is the distance between the two points that are farthest from each other in the target pixel group (that is, the pixel group derived from the one carbon nanotube).

[0068] The skeleton length is the length of the free curve formed by the target pixel group.

[0069] Next, for one field of view of the SEM image, the number a of carbon nanotubes with a skeleton length of 1 μm or more and the number b of carbon nanotubes with a skeleton length of 1 μm or more and a linearity of 0.9 or more were calculated. The linearity index was calculated according to the following formula.

[0070] Linearity index (%) = (b / a) × 100

[0071] Specifically, the linearity index is measured in accordance with the measurement method of the embodiment.

[0072] The carbon nanotube-dispersed composition more preferably satisfies the following (3).

[0073] (3) In the Raman spectrum of the coating film of the carbon nanotube dispersion composition, the wavelength at 1560 cm -1 ~1600cm -1 The maximum peak intensity in the range of 1310 cm -1 ~1350cm -1 When the maximum peak intensity in the range of is defined as D, the G / D ratio is 1.0 to 20.0.

[0074] The G / D ratio of the coating film of the carbon nanotube dispersion composition is preferably 1.0 or more, preferably 1.1 or more, more preferably 1.3 or more, and further preferably 1.7 or more. A high G / D ratio indicates that the carbon nanotubes have high crystallinity. Carbon nanotubes with high crystallinity have the advantage of contributing to conductivity in secondary batteries. Carbon nanotubes with high crystallinity are easy to maintain linearity indicators in the carbon nanotube dispersion composition, can further improve linearity, and more fully obtain the effects described above.

[0075] The G / D ratio of the coating film of the carbon nanotube dispersion composition is preferably less than 20, more preferably less than 10, and further preferably less than 8.0, and may also be less than 7.0, less than 5.0, or less than 2.0. If the G / D ratio of the coating film of the carbon nanotube dispersion composition is within the range, there is a tendency that the contact area between each particle of the active material and a carbon nanotube in the electrode film becomes larger, and the conductivity of the secondary battery can be further improved. In addition, if the crystallinity of the carbon nanotube increases, the carbon nanotube itself becomes hard, and in the carbon nanotube dispersion composition, the fiber length becomes shorter due to the breakage of the carbon nanotube, thereby making it difficult to maintain the linearity index. In addition, in order to prevent the breakage of the carbon nanotube, the management of the dispersion process may become complicated. From the viewpoint that the carbon nanotube itself has moderate flexibility, it is particularly preferred that the G / D ratio of the coating film of the carbon nanotube dispersion composition is less than 8.0.

[0076] For example, the G / D ratio of the coating film of the carbon nanotube dispersion composition may be 1.0 to 20, 1.1 to 10, or 1.3 to 8.0, or 1.0 to 7.0, 1.0 to 5.0, or 1.0 to 2.0.

[0077] In the present disclosure, the G / D ratio of a coating film of a carbon nanotube dispersion composition is a value measured by the following procedure.

[0078] First, a carbon nanotube dispersion composition is applied to a substrate and dried to obtain a coating film. Drying can be performed at a temperature that removes volatile components, and can be appropriately adjusted according to the type of solvent, for example, 100°C to 200°C. The thickness of the coating film can be such that the Raman spectrum can be measured, for example, 1μm to 10μm. For the obtained coating film, the Raman spectrum is measured to calculate the G / D ratio. In detail, the method for measuring the G / D ratio of the coating film of the carbon nanotube dispersion composition is in accordance with the measuring method of the embodiment.

[0079] The carbon nanotube dispersion composition more preferably satisfies the following (4).

[0080] (4) After freeze-drying the carbon nanotube dispersion composition, the BET specific surface area of ​​the powder passing through a 60 μm sieve relative to the mass of the carbon nanotubes is 50 m 2 / g~130m 2 / g.

[0081] The BET specific surface area of ​​the carbon nanotube powder derived from the carbon nanotube dispersion composition relative to the mass of the carbon nanotubes is preferably 50 m 2 / g or more, more preferably 60m 2 / g or more, more preferably 65m 2 / g or more. In these ranges, it can be predicted that in the carbon nanotube dispersion composition, the average outer diameter of the carbon nanotubes is small, the conductivity is improved, and the battery performance can be further improved. In addition, it can be predicted that the fiber length of the carbon nanotubes per volume is long, the linearity is improved, and the amount of carbon nanotubes in the electrode film is small, which can further improve the battery performance.

[0082] The BET specific surface area of ​​the carbon nanotube powder derived from the carbon nanotube dispersion composition relative to the mass of the carbon nanotubes is preferably 130 m 2 / g or less, more preferably 125m 2 / g or less, and more preferably 120m 2 / g or less. In these ranges, in the carbon nanotube dispersion composition, the aggregation of carbon nanotubes is suppressed, and the linearity of carbon nanotubes is maintained in the electrode film, which can further improve the battery performance. In addition, even if the number of carbon nanotubes per volume is reduced, since carbon nanotubes have linearity, one carbon nanotube in the electrode film is in contact with multiple particles of the active material to maintain a conductive path, which can further contribute to the battery performance.

[0083] By setting the BET specific surface area of ​​the carbon nanotube powder relative to the mass of the carbon nanotubes within these ranges, the workability of dispersing the carbon nanotube raw material into the solvent is improved, and a carbon nanotube dispersion composition with good dispersibility can be obtained. By using a carbon nanotube dispersion composition with good dispersibility, the distribution of carbon nanotubes in the electrode film becomes more uniform, and one carbon nanotube is connected to more particles of active materials, which can ensure a conductive path and help improve battery performance.

[0084] For example, the BET specific surface area of ​​the carbon nanotube powder derived from the carbon nanotube dispersion composition relative to the mass of the carbon nanotubes may be 50 m 2 / g or above and 130m 2 / g or less, 60m 2 / g or above and 125m 2 / g or less, or 65m 2 / g and above 120m 2 In these ranges, the battery performance is not deteriorated due to excessive aggregation or excessive dispersion, which is preferred.

[0085] In the present disclosure, the BET specific surface area of ​​the carbon nanotube powder derived from the carbon nanotube dispersion composition is a value measured by the following procedure.

[0086] 100 mL of the carbon nanotube dispersion composition was frozen in a -95°C ethanol bath for 5 hours using a freeze dryer (e.g., FDU-1200 / UT-4000 manufactured by Tokyo Rikki Co., Ltd.), and then dried under reduced pressure of 10 Pa to 30 Pa for 20 hours to obtain a carbon nanotube powder. The obtained carbon nanotube powder was passed through a 60 μm sieve, and the BET specific surface area was measured. In detail, the BET specific surface area of ​​the carbon nanotube powder derived from the carbon nanotube dispersion composition was measured according to the method of the embodiment.

[0087] (Carbon Nanotubes)

[0088] In the state of being contained in the carbon nanotube dispersion composition, the carbon nanotubes are more preferably carbon nanotubes specified by the following characteristics.

[0089] Carbon nanotubes have a shape obtained by winding a flat graphite into a cylindrical shape.

[0090] The carbon nanotube may be either a single-layer carbon nanotube or a multi-layer carbon nanotube. A single-layer carbon nanotube has a structure in which one layer of graphite is wound. A multi-layer carbon nanotube has a structure in which two or more layers of graphite are wound. In addition, the sidewall of the carbon nanotube may not be a graphite structure.

[0091] For example, carbon nanotubes having sidewalls with an amorphous structure may also be used as carbon nanotubes. From the viewpoint of being suitable for industrial mass production, it is preferable to use multilayer carbon nanotubes. In addition, from the viewpoint of dispersing in a manner that the average outer diameter and linearity index meet the desired range, multilayer carbon nanotubes are preferred. When using multilayer carbon nanotubes, single-layer carbon nanotubes may also be mixed in the carbon nanotubes.

[0092] Regarding the multi-walled carbon nanotube, the number of layers of the carbon nanotube is preferably 3 or more and 30 or less, more preferably 3 or more and 20 or less, and more preferably 3 or more and 10 or less.

[0093] About the shape of carbon nanotube, as long as average outer diameter and linear index meet the desired range, then there is no particular limitation. As the shape, for example, various shapes including needle-like, cylindrical tubular, fishbone (fishbone or cup stacking type) and coil-like can be listed. Wherein, from the viewpoint of linearity, the shape of carbon nanotube is preferably needle-like or cylindrical tubular. Carbon nanotube can be a combination of independent shape or two or more shapes. In the case of carbon nanotubes with high flexibility such as fishbone and coil, as for the whole of carbon nanotubes contained in carbon nanotube dispersion composition, as long as average outer diameter and linear index are met.

[0094] Examples of carbon nanotubes include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. However, the carbon nanotubes are not limited to these. The carbon nanotubes may have any of these forms alone or in combination of two or more forms.

[0095] In the state contained in the carbon nanotube dispersion composition, the average fiber length of the carbon nanotube is preferably 1 μm to 5 μm, and more preferably 1 μm to 3.5 μm. In order to measure the fiber length of the carbon nanotube, the CNT dispersion composition is diluted with a solvent so that the CNT concentration becomes 0.048 mass%, and the diluted dispersion composition is sprayed on a mica substrate in an amount of several μL, and then dried on a hot plate at 100°C to prepare a substrate for observing the CNT fiber length. The solvent used when preparing the CNT dispersion composition is used.

[0096] The SEM image was analyzed using image analysis software "WinROOF2015" (manufactured by Mitani Shoji) and the skeleton length of one carbon nanotube was calculated as the fiber length. The average value of the fiber lengths of 1,000 to 3,000 carbon nanotubes was counted as the average fiber length.

[0097] The maximum fiber length of the carbon nanotubes contained in the carbon nanotube dispersion composition is preferably 20 μm or less, more preferably 10 μm or less. The maximum fiber length of the carbon nanotubes can be measured by image analysis using the same method as that for evaluating the average fiber length.

[0098] (Carbon nanotube raw materials)

[0099] The carbon nanotube dispersion composition can be obtained using a carbon nanotube raw material. Hereinafter, several examples of carbon nanotube raw materials that can be used in the method for producing the carbon nanotube dispersion composition are described. The carbon nanotube dispersion composition based on the embodiment can use carbon nanotubes obtained from a variety of sources to exert its effect. In the following description, the carbon nanotube raw material refers to the carbon nanotube in the raw material state before being added to the carbon nanotube dispersion composition.

[0100] The average outer diameter of the carbon nanotube raw material is preferably 50 nm or less, more preferably 40 nm or less, or further preferably 20 nm or less. In these ranges, the amount of dispersant can be reduced relative to the carbon nanotube raw material, and the packing density of the active material can be further increased in the electrode film. For example, the average outer diameter of the carbon nanotube raw material can be 1 nm to 50 nm, 5 nm to 40 nm, or 7 nm to 20 nm. By using the carbon nanotube raw material in the range, a carbon nanotube dispersion composition having an average outer diameter and linearity index in a more suitable range can be obtained.

[0101] The standard deviation of the outer diameter of the carbon nanotube raw material is preferably 1 nm to 5 nm, more preferably 1 nm to 4 nm.

[0102] The average outer diameter of the carbon nanotube raw material was first measured by observing the carbon nanotubes using a scanning electron microscope and photographing them. Next, 300 carbon nanotubes were randomly selected from the observed photographs and their outer diameters were measured. Next, the average outer diameter (nm) of the carbon nanotube raw material was calculated as the number average of the outer diameters.

[0103] The linearity index of the carbon nanotube raw material may be 40% to 90%, 50% to 90%, 60% to 90%, or 50% to 80%, or 60% to 70%. By using the carbon nanotube raw material in the above range, a carbon nanotube dispersion composition containing carbon nanotubes showing an average outer diameter and linearity index in a more appropriate range can be obtained.

[0104] The linearity index of the carbon nanotube raw material is a value obtained as described above by the same procedure as for a sample taken out from the carbon nanotube dispersion composition.

[0105] Regarding the raw materials of carbon nanotubes, in the Raman spectrum, 1560 cm -1 ~1600cm -1The maximum peak intensity in the range of 1310 cm -1 ~1350cm -1 When the maximum peak intensity in the range of is defined as D, the G / D ratio may be 0.8 to 100, 1.1 to 10, or 1.7 to 7. By using the carbon nanotube raw material in these ranges, a carbon nanotube dispersion composition containing carbon nanotubes having a G / D ratio in a more appropriate range can be obtained.

[0106] The G / D ratio of the carbon nanotube raw material is a value obtained by the same procedure as that of the coating film of the carbon nanotube dispersion composition.

[0107] The BET specific surface area of ​​carbon nanotube raw materials can be 100m 2 / g~1000m 2 / g, 150m 2 / g~800m 2 / g, or 200m 2 / g~500m 2 By using the carbon nanotube raw material in these ranges, a carbon nanotube dispersion composition containing carbon nanotubes having a BET specific surface area in a more suitable range can be obtained. The BET specific surface area of ​​the carbon nanotube raw material is preferably 1000 m 2 / g or less, 800m 2 / g or less, or 500m 2 / g or less, also 100m 2 / g or more, 120m 2 / g or above, or 150m 2 In these ranges, when the carbon nanotube raw material is dispersed in a solvent, the dispersion process can be simplified, and dispersibility can be obtained with a small amount of dispersant, so that the packing density of the active material in the electrode film can be further increased.

[0108] The BET specific surface area of ​​the carbon nanotube raw material is a value obtained by the same procedure as that of the carbon nanotube powder derived from the carbon nanotube dispersion composition.

[0109] The carbon nanotube raw material may be used alone or in combination of two or more. When two or more carbon nanotube raw materials are used, it is preferred that at least a portion of the two or more carbon nanotube raw materials show a BET specific surface area within the specified range, and it is more preferred that all of the two or more carbon nanotube raw materials show a BET specific surface area within the specified range. In addition, when a mixed powder of all of the two or more carbon nanotube raw materials is used, it is more preferred that the mixed powder show a BET specific surface area within the specified range.

[0110] The average fiber length of the carbon nanotube raw material is preferably 1 μm to 5 μm, more preferably 1 μm to 3.5 μm. The fiber length of the carbon nanotube raw material can be measured in the following manner: the carbon nanotube raw material is dispersed in toluene using an ultrasonic homogenizer, and then the carbon nanotubes deposited on the mica substrate are observed by SEM and image analysis is performed. The SEM image is analyzed using image analysis software "WinROOF2015" (manufactured by Mitani Shoji) and the like, and for a carbon nanotube, the skeleton length is calculated as the fiber length. The average value obtained by counting the fiber lengths of 1000 to 3000 carbon nanotubes is taken as the average fiber length.

[0111] The maximum fiber length of the carbon nanotube raw material is preferably 20 μm or less, more preferably 10 μm or less. The maximum fiber length of the carbon nanotube raw material can be measured by dispersing the carbon nanotube raw material in toluene using an ultrasonic homogenizer, and then observing the carbon nanotubes deposited on the mica substrate by SEM and performing image analysis.

[0112] The volume resistivity of the carbon nanotube raw material is preferably 1.0×10 -2 Ω·cm~3.0×10 -2 Ω·cm, more preferably 1.0×10 -2 Ω·cm~2.0×10 -2 Ω·cm. The volume resistivity of the carbon nanotubes can be measured using a powder resistivity measuring device (for example, Loresta GP powder resistivity measuring system "MCP-PD-51" manufactured by Mitsubishi Chemical Analytech Co., Ltd.). In the state of being contained in the carbon nanotube dispersion composition, it is more preferable that the volume resistivity of the carbon nanotubes satisfies the above range like the carbon nanotube raw material.

[0113] The carbon purity of the carbon nanotube raw material is represented by the content rate (%) of carbon atoms in the carbon nanotube raw material. The carbon purity is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 98% by mass or more relative to 100% by mass of the carbon nanotube raw material. In the state of being contained in the carbon nanotube dispersion composition, it is more preferable that the carbon purity of the carbon nanotubes satisfies the above range like the carbon nanotube raw material.

[0114] The amount of metal contained in the carbon nanotube raw material is preferably less than 10% by mass, more preferably less than 5% by mass, further preferably less than 2% by mass, and further more preferably less than 1% by mass relative to 100% by mass of the carbon nanotube raw material. Examples of the metal contained in the carbon nanotube raw material include metals or metal oxides used as catalysts when synthesizing the carbon nanotube raw material. Specifically, examples include at least one metal selected from the group consisting of cobalt, nickel, aluminum, magnesium, silicon dioxide, manganese, and molybdenum, metal oxides thereof, and composite oxides thereof. When contained in the carbon nanotube dispersion composition, it is more preferable that the amount of metal in the carbon nanotubes satisfies the above range in the same manner as the carbon nanotube raw material.

[0115] Carbon nanotubes generally exist in the form of secondary particles. In the carbon nanotube raw material, the shape of the secondary particles of carbon nanotubes may be, for example, a state in which carbon nanotubes of general primary particles are intricately entangled with each other, or an aggregate of carbon nanotubes arranged in a straight line.

[0116] When contained in the carbon nanotube dispersion composition, the shape of the secondary particles of the carbon nanotubes can maintain the shape of the carbon nanotube raw material. For example, when contained in the carbon nanotube dispersion composition, the shape of the secondary particles of the carbon nanotubes is a collection of particles arranged in a straight line, so that the average outer diameter and linearity index of the carbon nanotubes can be more appropriately controlled within a specified range.

[0117] The carbon nanotube raw material may be a surface-treated carbon nanotube, a carbon nanotube derivative to which a functional group represented by a carboxyl group is added, or a carbon nanotube containing an organic compound, a metal atom, or a substance represented by fullerene.

[0118] The carbon nanotube raw material may be carbon nanotubes produced by any method. The carbon nanotube raw material can be generally produced by laser ablation, arc discharge, thermal chemical vapor deposition (CVD), plasma CVD, and combustion, but is not limited thereto.

[0119] For example, the carbon nanotube raw material can be produced by contacting and reacting a carbon source with a catalyst in an environment with an oxygen concentration of 1 vol% or less at 500° C. to 1000° C. The carbon source may be at least one of a hydrocarbon and an alcohol.

[0120] Any known raw material can be used as the raw material gas of the carbon source of the raw material of the carbon nanotubes. For example, hydrocarbons represented by methane, ethylene, propane, butane and acetylene, carbon monoxide, and alcohols can be used as raw material gases containing carbon, but they are not limited to these. In particular, from the perspective of ease of use, it is desirable to use at least one of hydrocarbons and alcohols as the raw material gas.

[0121] The carbon nanotube raw material tends to have the following tendency: when the heat treatment temperature becomes higher, the crystallinity of the carbon nanotubes increases, and the hardness of the carbon nanotubes increases, depending on the production method thereof.

[0122] In order to make the carbon nanotubes have an appropriate hardness and prevent the carbon nanotubes from breaking during the dispersion treatment in the production of the carbon nanotube dispersion composition, the heat treatment temperature in the production of the carbon nanotubes is preferably a relatively low temperature, for example, 1000° C. or less.

[0123] In order to obtain the linearity of carbon nanotubes, a certain degree of fiber length is required. However, if the crystallinity of carbon nanotubes is further improved by high-temperature heat treatment, the tendency of carbon nanotubes to break increases. From the above point of view, the heat treatment temperature in the manufacture of carbon nanotubes is also preferably a relatively low temperature. In the above case, the obtained carbon nanotube raw material may contain a single-layer carbon nanotube and a multi-layer carbon nanotube, or a combination of the two. From the point of view of controlling the crystallinity and fiber length of carbon nanotubes, it is easier to manufacture multi-layer carbon nanotubes, which has industrial advantages.

[0124] (Dispersant)

[0125] The dispersant can be used without particular limitation within the range that can stabilize the dispersion of the carbon nanotubes. For example, at least one of a surfactant and a resin-type dispersant can be used. Surfactants are mainly classified into anionic, cationic, nonionic, and amphoteric. A preferred type of dispersant can be used in a preferred amount according to the characteristics required for the dispersion of the carbon nanotubes. In one embodiment, a resin-type dispersant is preferably used.

[0126] 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, but are not limited to these. More 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 are not limited to these.

[0127] Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts. Specifically, examples include stearylamine acetate, trimethyl cocoyl 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, cetyl pyridinium bromide, 4-alkylthiopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride, but the present invention is not limited thereto.

[0128] Examples of the amphoteric surfactant include aminocarboxylates, but the amphoteric surfactant is not limited to these.

[0129] Examples of the nonionic surfactant include, but are not limited to, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers. Specifically, examples include, but are not limited to, polyoxyethylene lauryl ether, sorbitan fatty acid esters, and polyoxyethylene octyl phenyl ethers.

[0130] The selected surfactant is not limited to a single surfactant. It is also possible to use two or more surfactants in combination. For example, a combination of anionic surfactants and nonionic surfactants, or a combination of cationic surfactants and nonionic surfactants 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 surfactants and nonionic surfactants is preferred. The anionic surfactant preferably contains a polycarboxylate. The nonionic surfactant preferably contains polyoxyethylene phenyl ether.

[0131] In addition, as a resin type dispersant, specifically, cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, etc., or salts thereof), polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyacrylonitrile, polyacrylonitrile polymers (copolymers of polyacrylonitrile and acrylic acid, etc.), poly(meth)acrylic acid or salts thereof, poly(meth)acrylate, nitrile rubbers (acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, copolymers of hydrogenated nitrile rubber and hydrogenated butadiene acrylonitrile, etc.), etc. Polymers obtained by introducing other substituents into a part of these polymers, modified polymers, etc., may also be used. Particularly preferred are methyl cellulose, ethyl cellulose, carboxymethyl cellulose, or salts thereof, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyacrylonitrile polymers, copolymers of acrylonitrile and acrylic acid, (meth)acrylic acid or salts thereof, hydrogenated acrylonitrile butadiene rubber, and hydrogenated nitrile rubber and hydrogenated butadiene acrylonitrile copolymer. The resin-type dispersant may be used alone or in combination of two or more. The weight average molecular weight (Mw) of the resin-type dispersant is preferably 5,000 to 250,000, more preferably 10,000 to 150,000.

[0132] In some embodiments, the carbon nanotube dispersion composition may further include a basic compound. The basic compound may be any of an organic compound and an inorganic compound, and is preferably a basic inorganic compound in terms of facilitating the control of the stability of the dispersion system. Examples of the basic inorganic compound include inorganic bases and inorganic metal salts.

[0133] As the inorganic base and the inorganic metal salt, a compound containing at least one of an alkali metal and an alkaline earth metal is preferred. Specifically, chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, and borates containing at least one of an alkali metal and an alkaline earth metal can be cited.

[0134] In addition, among these, chlorides, hydroxides, and carbonates containing at least one of alkali metals and alkaline earth metals are preferred in terms of being able to easily supply cations. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide and magnesium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate and magnesium carbonate. Among these, at least one selected from the group consisting of lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate is more preferred.

[0135] In some embodiments, the carbon nanotube dispersion composition may further contain other arbitrary components such as amine compounds, wetting agents, defoaming agents, surfactants, pH adjusters, wetting and penetrating agents, antioxidants, preservatives, mildew inhibitors, leveling agents, and tackifiers as needed. In addition, the carbon nanotube dispersion composition may also contain conductive materials and polymer components other than carbon nanotubes within the scope that does not hinder the purpose of the present invention. These arbitrary components can be added at any time before, during, or after the dispersion treatment of the carbon nanotube dispersion composition.

[0136] In some embodiments, the carbon nanotube dispersion composition may further include a defoamer. As the defoamer, any commercially available defoamer, wetting agent, hydrophilic organic solvent, water-soluble organic solvent, or other component having a defoaming effect may be used. The defoamer may be used alone or in combination of two or more.

[0137] Examples of defoaming agents include alcohols: ethanol, propanol, isopropanol, butanol, octyl alcohol, hexadecyl alcohol, acetylene alcohol, ethylene glycol monobutyl ether, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, acetylene glycol, polyoxyalkylene glycol, propylene glycol, and other glycols; fatty acid esters: diethylene glycol laurate, glycerol monoricinoleate, alkenyl succinic acid derivatives, sorbitol monolaurate, sorbitan trioleate, polyoxyethylene ethylene monolaurate, polyoxyethylene sorbitan monolaurate, natural wax, etc., amide series: polyoxyalkylene amide, acrylate polyamine, etc., phosphate ester series: tributyl phosphate, sodium octyl phosphate, etc., metal soap series: aluminum stearate, calcium oleate, etc., oil series: animal and vegetable oils, sesame oil, castor oil, etc., mineral oil series: kerosene, paraffin, etc., silicone series: dimethyl silicone oil, silicone cream, silicone emulsion, organic modified polysiloxane, fluorosilicone oil, etc.

[0138] In some embodiments, the carbon nanotube dispersion composition may further include a thickener. Examples of the thickener include polysaccharides such as carboxymethyl cellulose or its salts, polyvinylidene fluoride, and derivatives thereof. Examples of commercially available products include carboxymethyl cellulose #1190 (manufactured by Daicel FineChem). One type of thickener may be used, or two or more types may be used in combination.

[0139] (solvent)

[0140] In some embodiments, the solvent is not particularly limited as long as it is a range in which the carbon nanotubes can be dispersed. The solvent may, for example, be a mixed solvent comprising water, and any one of a water-soluble organic solvent, or two or more thereof. The solvent preferably comprises at least water. When the solvent comprises water, the content of water is 50 parts by mass or more, 80 parts by mass or more, 90 parts by mass or more, 95 parts by mass or more, or 98 parts by mass or more relative to the whole of the solvent (100 parts by mass), and the remainder may comprise a water-soluble organic solvent. In addition, the whole of the solvent (100 parts by mass) may be water.

[0141] In addition, as one embodiment, from the viewpoint of affinity for carbon nanotubes, it is preferred to include an amide organic solvent. When the solvent includes an amide organic solvent, the content of the amide organic solvent may be 50 parts by mass or more, 80 parts by mass or more, 90 parts by mass or more, 95 parts by mass or more, or 98 parts by mass or more relative to the entirety of the solvent (100 parts by mass). Alternatively, the entirety of the solvent (100 parts by mass) may be an amide organic solvent.

[0142] As the water-soluble organic solvent, the following can be used: alcohols (methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, benzyl alcohol, etc.), polyols (ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, hexanediol, pentanediol, glycerol, hexanetriol, thiodiglycol, etc.), polyol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutylene glycol, etc.), Ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N- ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amide series (N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylcaprolactam, etc.), heterocyclic series (cyclohexylpyrrolidone, 2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.), sulfoxide series (dimethyl sulfoxide, etc.), sulfone series (hexamethylphosphoric acid triamide, cyclopentane sulfone, etc.), lower ketone series (acetone, methyl ethyl ketone, etc.), and in addition tetrahydrofuran, urea, and acetonitrile, etc. In particular, when used for composite material slurry for positive electrode, as a water-soluble organic solvent, it is preferred to use an amide-based organic solvent, wherein, from the viewpoint of affinity for carbon nanotubes and solubility of fluororesin as a binder resin, it is preferred to include at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP). The water-soluble organic solvent can be used alone or in combination of two or more.

[0143] (Characteristics of Carbon Nanotube Dispersed Composition)

[0144] The carbon nanotube dispersion composition can be specifically specified by the complex elastic modulus, phase angle, or a combination thereof at 25° C. and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement.

[0145] The complex elastic modulus of the carbon nanotube dispersion composition at 25°C and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is preferably 4 Pa ​​or more, more preferably 10 Pa or more, further preferably 20 Pa or more, further more preferably 30 Pa or more. In addition, it is preferably 250 Pa or less, more preferably 200 Pa or less, further preferably 100 Pa or less, further more preferably 80 Pa or less, and particularly preferably 47 Pa or less.

[0146] Regarding the carbon nanotube dispersion composition, the complex elastic modulus at 25°C and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is preferably 4 Pa ​​to 250 Pa, preferably 4 Pa ​​to 200 Pa, 10 Pa to 100 Pa, 20 Pa to 80 Pa, or 20 Pa to 47 Pa.

[0147] Regarding the carbon nanotube dispersion composition, the phase angle at 25°C and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is preferably 3° or more, more preferably 8° or more, further preferably 12° or more, further preferably 16° or more. In addition, it is preferably 60° or less, more preferably 45° or less, further preferably 35° or less, further more preferably 31° or less.

[0148] The phase angle of the carbon nanotube dispersion composition at 25°C and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is preferably 3° to 60°, preferably 8° to 60°, 16° to 60°, or 16° to 35°.

[0149] The carbon nanotube-dispersed composition may have a complex elastic modulus and a phase angle at 25° C. and a frequency of 10 Hz, respectively, which are obtained by dynamic viscoelasticity measurement and satisfy the above ranges.

[0150] Complex elastic modulus and phase angle can be evaluated by dynamic viscoelasticity measurement. The better the dispersibility of carbon nanotubes, and the lower the viscosity of the carbon nanotube dispersion composition, the more the complex elastic modulus of the carbon nanotube dispersion composition tends to decrease. In addition, phase angle refers to the phase shift of stress wave when the strain provided to the carbon nanotube dispersion composition is set to a sine wave. If it is a pure elastic body, it becomes a sine wave with the same phase as the strain provided, so the phase angle is 0 °. On the other hand, if it is a pure viscous body, it becomes a stress wave that advances 90 °. In general viscoelasticity measurement specimens, it becomes a sine wave with a phase angle greater than 0 ° and less than 90 °. If the dispersibility of the carbon nanotubes in the carbon nanotube dispersion composition is good, the phase angle is close to 90 ° as a pure viscous body.

[0151] When the fiber length of the carbon nanotubes in the carbon nanotube dispersion composition is large, even if the dispersion is good, the complex elastic modulus sometimes becomes a high value because the carbon nanotubes themselves have structural viscosity. However, the carbon nanotube dispersion composition having the complex elastic modulus and the phase angle values ​​within the above range has a good dispersed particle size and dispersibility of the carbon nanotubes. Therefore, it can be preferably used as a carbon nanotube dispersion composition for non-aqueous electrolyte secondary batteries.

[0152] The complex elastic modulus and phase angle at 25° C. and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement of the carbon nanotube dispersion composition were determined according to the measurement methods used in the examples.

[0153] The cumulative particle size D50 of the carbon nanotube dispersion composition is preferably 300 nm to 7000 nm, more preferably 700 nm to 3000 nm. The cumulative particle size D50 of the carbon nanotube dispersion composition can be measured on a volume basis using a particle size distribution meter (eg, Partical LA-960V2, manufactured by Horiba, Ltd.).

[0154] The pH of the carbon nanotube dispersion composition may be 3 to 6. The pH of the carbon nanotube dispersion composition is preferably 4 to 6, and more preferably 4 to 5. The pH of the carbon nanotube dispersion composition can be measured using a pH meter (eg, pH METER F-52 manufactured by Horiba, Ltd.).

[0155] The viscosity of the carbon nanotube dispersion composition is preferably 10 mPa·s or more and less than 10000 mPa·s, more preferably 10 mPa·s or more and less than 2000 mPa·s, as measured at 25°C using a Brookfield viscometer at 60 rpm.

[0156] In one embodiment, the content of carbon nanotubes in the carbon nanotube dispersion composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and further preferably 0.5 parts by mass or more, relative to 100 parts by mass of the carbon nanotube dispersion composition. Within these ranges, when providing a composite material slurry, the carbon nanotube dispersion composition and the active material can be more appropriately mixed and dispersed at a ratio of a plurality of particles of the active material relative to one carbon nanotube.

[0157] Relative to 100 mass parts of carbon nanotube dispersion composition, the content of the carbon nanotube in the carbon nanotube dispersion composition is preferably less than 20 mass parts, more preferably less than 10 mass parts, and then preferably less than 5 mass parts, and also less than 3 mass parts. In these ranges, the dispersibility of the carbon nanotube dispersion composition can be better maintained. In addition, since dispersibility is maintained in the carbon nanotube dispersion composition, when the electrode film is provided using the composite material slurry, the carbon nanotube maintains linearity in the electrode film, and the number of particles of the active material contacted by a carbon nanotube increases, and the performance of the secondary battery can be further improved.

[0158] For example, the content of carbon nanotubes in the carbon nanotube dispersion composition is preferably 0.2 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the carbon nanotube dispersion composition.

[0159] In one embodiment, from the viewpoint of dispersion stability, the amount of the dispersant in the carbon nanotube dispersion composition is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 40 parts by mass or more, and may be 60 parts by mass or more, relative to 100 parts by mass of carbon nanotubes. From the viewpoint of dispersion stability, the amount of the dispersant in the carbon nanotube dispersion composition is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, and further preferably 120 parts by mass or less, and may be 100 parts by mass or less, relative to 100 parts by mass of carbon nanotubes. For example, the amount of the dispersant in the carbon nanotube dispersion composition is preferably 10 to 300 parts by mass, more preferably 40 to 200 parts by mass, and further preferably 60 to 120 parts by mass, and may be 70 to 100 parts by mass.

[0160] In one embodiment, the non-volatile content of the carbon nanotube dispersion composition is 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to 100% by mass of the carbon nanotubes, and the remainder may be a solvent. Here, the non-volatile content is the mass of the coating film after the carbon nanotube dispersion composition is dried.

[0161] When the carbon nanotube dispersion composition contains components other than carbon nanotubes, a dispersant and a solvent, the amount of the other components in the carbon nanotube dispersion composition may be 0.1 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass relative to 100 parts by mass of the carbon nanotube dispersion composition.

[0162] When a basic compound is included in the carbon nanotube dispersion composition, the amount of the basic compound in the carbon nanotube dispersion composition may be 0.01 to 1 part by mass, 0.02 to 0.5 parts by mass, or 0.04 to 0.1 parts by mass relative to 100 parts by mass of the carbon nanotube dispersion composition. When a basic compound is included in the carbon nanotube dispersion composition, the amount of the basic compound in the carbon nanotube dispersion composition may be 1 to 20 parts by mass, 2 to 10 parts by mass, or 4 to 8 parts by mass relative to 100 parts by mass of the dispersant.

[0163] When the carbon nanotube dispersion composition contains a defoamer, the amount of the defoamer in the carbon nanotube dispersion composition may be 0.01 to 1, 0.02 to 0.5, or 0.04 to 0.1 parts by mass relative to 100 parts by mass of the carbon nanotube dispersion composition.

[0164] (Method for producing a carbon nanotube-dispersed composition)

[0165] The method for producing the carbon nanotube dispersion composition is not particularly limited, and the method can be carried out by mixing the carbon nanotube raw material, the dispersant and the solvent together or separately. The carbon nanotube raw material described above can be used as the carbon nanotube raw material. In addition, when the dispersion treatment is carried out after mixing, it is preferable to carry out the dispersion treatment in a manner that the carbon nanotubes in the obtained carbon nanotube dispersion composition have a predetermined average outer diameter and linearity index. The dispersing device used for the dispersion treatment is not particularly limited.

[0166] As the dispersing device, a disperser generally used for pigment dispersion or the like can be used.

[0167] For example, mixers such as dispersers, homomixers, and planetary mixers are listed; homogenizers ("Advanced Digital Sonifer" (registered trademark) model 450DA manufactured by Branson, "clearmix" manufactured by M-technique, "filmix" manufactured by PRIMIX, "abramix" manufactured by Silverson, etc.), paint conditioners (Red Devil, Devil), colloid mills (PUC Colloid Mill, IKA Colloid Mill MK), cone mills (IKA Cone Mill MKO), ball mills, sand mills (SHINMARU ENTERPRISES Dyno Mill), attritors, pearl mills (Eirich DCP Mill The present invention also includes media-type dispersers such as "Jenius PY" manufactured by Jenius, "Starburst" manufactured by Suginos Machine, "nanomizer" manufactured by Nanomizer, etc.), "Clear SS-5" manufactured by M-technique, "MICROS" manufactured by Nara Machinery, etc.; other roller mills, etc., but are not limited to these.

[0168] In some embodiments, the dispersion treatment for preparing the carbon nanotube dispersion composition is preferably carried out using a homogenizer, a medium-type disperser, a medium-free disperser, or a combination thereof. The dispersion treatment using a homogenizer is preferably carried out under a high pressure of, for example, 60 MPa to 150 MPa. In the case of using a medium-type disperser for dispersion treatment, it is preferred to use beads such as zirconium oxide beads. The diameter of the beads used is preferably less than 1.25 mm, more preferably less than 1.0 mm.

[0169] In the dispersion treatment, it is preferred to use a homogenizer, which can be used alone, or a homogenizer can be used in combination with at least one of a medium-type dispersion machine and a medium-free dispersion machine. In the dispersion treatment, the dispersion treatment can also be carried out by a method without using a medium-type dispersion machine to prevent the carbon nanotubes from breaking due to the collision of the medium with the carbon nanotubes. In the case described, in the dispersion treatment, it can be a homogenizer alone, or it can be a combination of a homogenizer and a medium-free dispersion machine. For example, by wet mixing with a medium-free dispersion machine before and after the dispersion treatment of the homogenizer, the fiber length of the carbon nanotube can be maintained, and the carbon nanotubes with a linearity index of a more appropriate range can be included in the dispersed composition.

[0170] As a commercially available example of a homogenizer, for example, "R-MODEL such as R5, G-MODEL such as G5" manufactured by MST Co., Ltd., "Starburst" manufactured by Sugino Machine Co., Ltd., "OMEGA" manufactured by Ashizawa Finetech Co., Ltd., etc., can be cited, but it is not limited to these. As a commercially available example of a medium-free disperser, for example, "3L kneader" manufactured by Inoue Manufacturing Co., Ltd., "planetary mixer" manufactured by Inoue Manufacturing Co., Ltd., "Plastomill" manufactured by Toyo Seiki Manufacturing Co., Ltd., "twin-shaft kneading extruder PCM30" manufactured by Ikegai Co., Ltd., "mixing roll mill" manufactured by Inoue Manufacturing Co., Ltd., etc., can be cited, but it is not limited to these.

[0171] <Carbon nanotube resin composition>

[0172] According to some embodiments, a carbon nanotube resin composition is provided. The carbon nanotube resin composition includes carbon nanotubes, a dispersant, a solvent, and a binder. The carbon nanotube resin composition may include a carbon nanotube dispersion composition and a binder. The binder is described below.

[0173] (Adhesive)

[0174] The binder is a resin used to bond substances such as carbon nanotubes to each other.

[0175] As the binder, for example, there can be listed: polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, methacrylic acid, methacrylate, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc. as constituent units; polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, acrylic resin, formaldehyde resin, silicone resin, and fluororesin; cellulose resin such as carboxymethyl cellulose; rubbers such as styrene butadiene rubber and fluororubber; conductive resins such as polyaniline and polyacetylene, etc. As fluororesin, polytetrafluoroethylene, etc. can be listed. The binder can also be a modified product, a mixture, and a copolymer of the above resins. Among them, the binder preferably contains at least one selected from the group consisting of carboxymethyl cellulose, styrene butadiene rubber, and polyacrylic acid.

[0176] The carboxymethyl cellulose used as a binder preferably has a high viscosity. For example, the viscosity of a 1% aqueous solution of carboxymethyl cellulose is preferably 500 mPa·s to 6000 mPa·s, and more preferably 1000 mPa·s to 3000 mPa·s. The viscosity of a 1% aqueous solution of carboxymethyl cellulose can be measured using a B-type viscometer rotor at 25°C and a rotation speed of 60 rpm.

[0177] The carboxymethyl cellulose used as the binder preferably has a high degree of etherification. For example, the degree of etherification is preferably 0.6 to 1.5, and more preferably 0.8 to 1.2.

[0178] The styrene butadiene rubber used as the binder resin may be a substance generally used as a binder material for electrodes if it is an oil-in-water emulsion. In one embodiment, the binder is preferably an emulsion containing styrene butadiene rubber. For example, "TRD2001" manufactured by JSR Co., Ltd. may be preferably used.

[0179] The type of the binder and its amount ratio can be appropriately selected according to the properties of coexisting substances such as carbon nanotubes and active materials.

[0180] In the carbon nanotube resin composition, the content of the binder may be 1 to 100 parts by mass, 5 to 500 parts by mass, or 10 to 30 parts by mass relative to 1 part by mass of the carbon nanotubes.

[0181] The carbon nanotube resin composition comprises carbon nanotubes, a dispersant, a solvent, and a binder, and can be obtained by mixing these together or separately. In other examples, the carbon nanotube resin composition comprises a carbon nanotube dispersion composition and a binder, and can be obtained by mixing the binder in the carbon nanotube dispersion composition. In any method, in the obtained carbon nanotube resin composition, the average outer diameter and linearity index of the carbon nanotubes are preferably within the ranges described in the carbon nanotube dispersion composition.

[0182] For example, in order to avoid the breakage of carbon nanotubes caused by mixing, the carbon nanotube dispersion composition and the binder are preferably mixed using the dispersion device described in the carbon nanotube dispersion composition. Thus, in the carbon nanotube resin composition, the average outer diameter and linearity index of the carbon nanotubes can also be maintained within the specified range.

[0183] The carbon nanotube resin composition may further contain an additional arbitrary component. The additional arbitrary component may be the component described in the above-mentioned carbon nanotube dispersion composition.

[0184] <Composite material slurry>

[0185] According to some embodiments, a composite material slurry is provided. The composite material slurry includes carbon nanotubes, a dispersant, a solvent, a binder, and an active substance. The composite material slurry may include a carbon nanotube resin composition and an active substance, or may include a carbon nanotube dispersion composition, a binder, and an active substance. The active substance is described below.

[0186] (Active substance)

[0187] The active material is a material that serves as a basis for a battery reaction. From the viewpoint of electromotive force, the active material is divided into a positive electrode active material and a negative electrode active material.

[0188] The positive electrode active material is not particularly limited, and metal compounds such as metal oxides and metal sulfides, and conductive polymers that can be doped or absorbed with lithium ions can be used.

[0189] For example, inorganic compounds such as oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides with lithium, and transition metal sulfides can be cited. Specifically, inorganic compounds such as MnO, V2O5, V6O 13 , and transition metal oxide powders such as TiO2, composite oxide powders of lithium and transition metals such as layered lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide, spinel structured lithium manganese oxide, lithium iron phosphate-based materials as olivine-structured phosphate compounds, transition metal sulfide powders such as TiS2 and FeS, etc.

[0190] The positive electrode active material may be an organic compound. For example, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene may also be used. As the positive electrode active material, the inorganic compound and the organic compound may be mixed and used.

[0191] The negative electrode active material is not particularly limited as long as it can be doped or embedded with lithium ions. For example, metal Li, alloys thereof such as tin alloys, silicon alloys, and lead alloys, Li X Fe2O3、Li X Fe3O4、Li X WO2 (x is a number where 0 < x < 1), metal oxides such as lithium titanate, lithium vanadate, and lithium silicate, conductive polymers such as polyacetylene and polyphenylene, amorphous carbon materials such as soft carbon and hard carbon, graphite materials such as artificial graphite and natural graphite such as highly graphitized carbon materials, carbon black, mesophase carbon black, resin-fired carbon materials, vapor-grown carbon fibers, and carbon fibers. These negative electrode active materials may be used alone or in combination.

[0192] In one embodiment, as the negative electrode active material, a silicon-based negative electrode active material, which is a negative electrode active material containing silicon, such as a silicon alloy and lithium silicate, is preferable.

[0193] As silicon-based negative electrode active materials, for example, there can be listed: so-called metallurgical grade silicon produced by reducing silicon dioxide with carbon; industrial grade silicon whose impurities are reduced by acid treatment or unidirectional solidification of metallurgical grade silicon; high-purity silicon in different crystalline states such as single crystal, polycrystalline, and amorphous, produced by reacting silane with silicon; silicon in which the crystalline state and precipitation state are adjusted while industrial grade silicon is made high-purity by sputtering and electron beam evaporation (EB (electron beam) evaporation) methods, etc.

[0194] In addition, silicon oxide as a compound of silicon and oxygen, various alloys with silicon, and crystalline silicon compounds prepared by a quenching method, etc. can also be cited. Among them, a silicon-based negative electrode active material is preferred, which is a mixture of silicon nanoparticles and silicon oxide having a structure in which silicon nanoparticles are dispersed in silicon oxide, and the outer side of the mixture is covered with a carbon film.

[0195] In one embodiment, the negative electrode active material may include carbonaceous, graphitic carbonaceous, or graphite materials as carbon materials in addition to the silicon-based negative electrode active material. For example, the carbonaceous material may include amorphous carbonaceous materials such as soft carbon and hard carbon.

[0196] Examples of the graphite material include artificial graphite such as highly graphitizable carbon materials and natural graphite, etc. Among them, it is preferable to use powders of graphite materials such as artificial graphite and natural graphite.

[0197] When the carbon material such as artificial graphite and natural graphite is taken as 100 mass %, the amount of the silicon-based negative electrode active material is preferably 3 mass % to 50 mass %, and more preferably 5 mass % to 25 mass %.

[0198] In one embodiment, the BET specific surface area of ​​the active material is preferably 0.1 m 2 / g~10m 2 / g, more preferably 0.2m 2 / g~5m 2 / g, and more preferably 0.3m 2 / g~3m 2 / g.

[0199] In one embodiment, the average particle size of the active material is preferably in the range of 0.5 μm to 50 μm, more preferably in the range of 2 μm to 20 μm. The “average particle size of the active material” described in this disclosure refers to the average value of the particle size (major diameter) of the active material measured using an electron microscope.

[0200] (Method for producing composite material slurry)

[0201] The composite material slurry can be prepared by various methods known in the art. For example, there can be mentioned a method of mixing an active material in a carbon nanotube resin composition, a method of mixing a binder and an active material together or separately in a carbon nanotube dispersion composition, etc. The composite material slurry can be obtained by mixing carbon nanotubes, a dispersant, a solvent, a binder, and an active material together or separately.

[0202] Preferably, the composite material slurry can be obtained by mixing the active material and the binder together or separately in the carbon nanotube dispersion composition. In the method, the average outer diameter and linearity index of the carbon nanotubes in the carbon nanotube dispersion composition can be more appropriately adjusted to a predetermined range, and the control of the dispersion conditions in the subsequent adjustment of the composite material slurry becomes simpler.

[0203] In one embodiment, in order to obtain a composite material slurry, it is preferred that an active substance is added to the carbon nanotube dispersion composition or the carbon nanotube resin composition, and then a dispersion treatment is further performed. The dispersion device used for the dispersion treatment is not particularly limited. The composite material slurry can be prepared using the dispersion device described for the carbon nanotube dispersion composition.

[0204] In one embodiment, the amount of the active material in the composite material slurry is preferably 20 to 90 parts by mass, more preferably 30 to 80 parts by mass, and even more preferably 40 to 60 parts by mass, relative to 100 parts by mass of the composite material slurry.

[0205] In one embodiment, the amount of carbon nanotubes in the composite material slurry is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, further preferably 0.1 to 1 part by mass, and further more preferably 0.15 to 0.5 parts by mass, relative to 100 parts by mass of the active material.

[0206] In one embodiment, the amount of the binder in the composite material slurry is preferably 0.1% to 30% by mass, more preferably 0.5% to 20% by mass, further preferably 1% to 10% by mass, further more preferably 1.5% to 5% by mass, relative to 100 parts by mass of the active material.

[0207] The amount of the binder in the composite material slurry can also be more appropriately controlled according to the type of binder. For example, when the mass of the active material is set to 100 parts by mass, the amount of carboxymethyl cellulose used as a binder is preferably 0.5% by mass to 3.0% by mass, and more preferably 1.0% by mass to 2.0% by mass. When the mass of the active material is set to 100% by mass, the amount of styrene butadiene rubber used as a binder is preferably 0.5% by mass to 3.0% by mass, and more preferably 1.0% by mass to 2.0% by mass. When the mass of the active material is set to 100% by mass, the amount of polyacrylic acid used as a binder is preferably 1% by mass to 25% by mass, and more preferably 5% by mass to 20% by mass.

[0208] The composite material slurry may further contain other additives. The other additives may be the additives described in the carbon nanotube dispersion composition. For example, from the perspective of coating properties on a substrate, a thickener may be additionally contained in the composite material slurry.

[0209] In one embodiment, the amount of the solid content of the composite material slurry is preferably 30% to 90% by mass, more preferably 30% to 80% by mass, and preferably 40% to 70% by mass relative to 100% by mass of the composite material slurry. Here, the solid content of the composite material slurry is a component in the coating film that does not volatilize in the solvent removal step and can form a coating film.

[0210] <Electrode film>

[0211] According to some embodiments, an electrode film is provided. The electrode film can be used in a secondary battery represented by a lithium ion secondary battery. For example, the electrode film can be provided as an electrode composite material layer provided on a current collector in a secondary battery. The electrode film can be obtained by forming a composite material slurry into a film shape. For example, the electrode film can be a coating film obtained by coating a composite material slurry on a current collector and drying it.

[0212] The collector provided with the electrode film is not particularly limited. It can be a material and shape applicable to various secondary batteries, and can be appropriately selected. For example, as the material of the collector, metals such as aluminum, copper, nickel, titanium, and stainless steel, and alloys thereof can be listed. In addition, as the shape of the collector, it can generally be a flat foil shape, but a collector with a roughened surface, an open-hole foil shape, and a mesh shape can also be used.

[0213] There is no particular limitation on the method for coating the composite material slurry on the collector, and known methods can be used, including die coating, dip coating, roll coating, blade coating, spray coating, gravure coating, screen printing, and electrostatic coating.

[0214] As the drying method, drying by placing, a blower dryer, a warm air dryer, an infrared heater, a far infrared heater, etc. can be used, but the method is not particularly limited to these.

[0215] After coating, a rolling treatment using a planographic press or a calender roll may be performed. The thickness of the electrode film is generally 1 μm or more and 500 μm or less, and preferably 10 μm or more and 300 μm or less.

[0216] <Non-aqueous electrolyte secondary battery>

[0217] According to some embodiments, a nonaqueous electrolyte secondary battery is provided. Specifically, the nonaqueous electrolyte secondary battery may be a lithium ion secondary battery. The nonaqueous electrolyte secondary battery comprises a positive electrode, a negative electrode, and an electrolyte. In the secondary battery, at least one of the positive electrode and the negative electrode comprises an electrode film, and the electrode film may be an electrode film based on an embodiment. The electrode film based on an embodiment may be a coating film of a composite material slurry based on an embodiment, or may be an electrode film obtained using a carbon nanotube dispersion composition based on an embodiment, or a carbon nanotube resin composition.

[0218] One or both of the positive electrode and the negative electrode may include an electrode film according to one embodiment. In addition, the negative electrode including the electrode film according to one embodiment may further contribute to improving rate characteristics and cycle characteristics. For example, when a silicon-based active material is included in the negative electrode, the cycle characteristics tend to decrease due to the volume change caused by charging and discharging, but by using an electrode film according to one embodiment, the conductivity between particles of the active material can be maintained before and after the volume change, thereby suppressing the decrease in the cycle characteristics.

[0219] As the positive electrode, a composite material slurry containing a positive electrode active material is applied to a current collector and then dried to form an electrode film.

[0220] As the negative electrode, a composite material slurry containing a negative electrode active material is applied to a current collector and then dried to form an electrode film.

[0221] As an electrolyte, various known compounds in which ions can move can be used. Compounds that can be used as electrolytes may include, for example, lithium salts such as 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). Among them, it is not limited to these, and compounds containing sodium salts and calcium salts may also be used. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolyte.

[0222] There is no particular limitation on the non-aqueous solvent. For example, 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-octanolactone; ethylene 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 can be used alone or in combination of two or more.

[0223] In one embodiment, the secondary battery preferably includes a separator. The separator may be formed of, for example, polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, or any of these materials subjected to a hydrophilic treatment, but is not particularly limited thereto.

[0224] The secondary battery may be in a paper shape, a cylinder shape, a button shape, a stacked shape, or the like, and may be in various shapes depending on the intended use.

[0225] <Other embodiments>

[0226] According to some embodiments, a method for producing a carbon nanotube dispersion composition using carbon nanotubes can be provided. More specifically, a carbon nanotube dispersion composition for producing an electrode material for a secondary battery using carbon nanotubes can be provided. For example, a method for producing a carbon nanotube dispersion composition used in a non-aqueous electrolyte secondary battery, more specifically a negative electrode of a lithium ion secondary battery, and more specifically a negative electrode containing a silicon-based active material can be provided. The carbon nanotubes used in the production method are preferably the carbon nanotube raw materials described in the carbon nanotube dispersion composition.

[0227] For example, the carbon nanotubes preferably satisfy at least the average outer diameter and linearity indexes within the ranges described in the carbon nanotube raw material, and more preferably arbitrarily satisfy one or both of the BET specific surface area and the G / D ratio, and more preferably arbitrarily satisfy other physical property values.

[0228] According to some embodiments, a method for producing a carbon nanotube resin composition using carbon nanotubes, a method for producing a composite material slurry using carbon nanotubes, a method for producing an electrode film using carbon nanotubes, and a method for producing a secondary battery using carbon nanotubes can be provided.

[0229] Furthermore, according to some embodiments, there can be provided a use of carbon nanotubes in a carbon nanotube dispersion composition, a carbon nanotube resin composition, a composite material slurry, an electrode film, and a secondary battery. Regarding carbon nanotubes, as described above. These can be various methods of using carbon nanotubes in a negative electrode of a non-aqueous electrolyte secondary battery, more specifically a lithium ion secondary battery, and more specifically a negative electrode containing a silicon-based active material.

[0230] According to these embodiments, in one or both of the positive electrode and the negative electrode, carbon nanotubes having an average outer diameter and linearity index satisfying a predetermined range can be included in the electrode film, thereby improving the rate characteristics and cycle characteristics of the secondary battery.

[0231] Example

[0232] The present invention is described in more detail below with reference to the following examples. The present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples, "carbon nanotubes" are sometimes referred to as "CNTs". In addition, "parts" means "parts by mass" and "%" means "% by mass" unless otherwise specified.

[0233] Table 1 shows the formulation and evaluation results of the CNT dispersion composition. Table 2 shows the formulation of the composite material slurry for the negative electrode. Table 3 shows the formulation of the composite material slurry for the positive electrode. Tables 4 and 5 show the rate characteristics and cycle characteristics of the secondary battery using the materials made in the embodiments and comparative examples in the negative electrode and the positive electrode, respectively. Tables 2 and 3 show the mass % of each component relative to 100 mass % of the non-volatile component, and show the mass % of the total amount of non-volatile components relative to 100 mass % of the composite material slurry.

[0234] <1>Methods for measuring physical properties

[0235] The measurement methods of physical properties used in Examples are described below.

[0236] (1) Average outer diameter of CNT

[0237] Regarding the average outer diameter of the CNT dispersion composition, a sample was prepared as follows using the CNT dispersion composition shown in Table 1, and the average outer diameter was measured as follows using the sample.

[0238] Sample preparation: The CNT dispersion composition was diluted with a solvent so that the CNT concentration was 0.048 mass %. The diluted dispersion composition was sprayed on a mica substrate in an amount of several μL, and then dried on a hot plate at 100°C to prepare a substrate for observing the average outer diameter of CNTs. Then, the surface of the prepared substrate was sputtered with platinum. The solvent used when preparing the CNT dispersion composition was used.

[0239] Measurement method: The carbon nanotubes were observed and photographed using a scanning electron microscope (manufactured by JEOL Ltd.). Next, the observation was performed at a magnification of 50,000 times, and 300 carbon nanotubes were randomly selected from the multiple observation photos, and their outer diameters were measured. Next, the average outer diameter (nm) of the carbon nanotubes was calculated as the number average of their outer diameters.

[0240] (2) Linearity index

[0241] Regarding the linearity index of the CNT dispersion composition, a sample was prepared as follows using the CNT dispersion composition shown in Table 1, and the linearity index was measured as follows using the sample.

[0242] Sample preparation: The CNT dispersion composition was diluted with a solvent so that the CNT concentration was 0.048 mass %. The diluted dispersion composition was sprayed on a mica substrate in an amount of several μL, and then dried on a hot plate at 100°C to prepare a substrate for observing the CNT linearity index. Then, the surface of the prepared substrate was sputtered with platinum. The solvent used when preparing the CNT dispersion composition was used.

[0243] Measurement method: Use a scanning electron microscope (manufactured by JEOL Ltd.) to obtain an SEM image of the sample. At this time, set it in a way that the shapes of 50 to 200 carbon nanotubes are observed in one field of view. Take the SEM image under the condition of 4.63nm per pixel. In addition, an error range of 4.63nm±10% is allowed under the shooting conditions. Move the field of view until a total of 1000 to 3000 carbon nanotubes can be observed and obtain an SEM image.

[0244] Software: The SEM images were analyzed using the image analysis software "WinROOF2015" (manufactured by Mitani Shoji) to calculate the absolute maximum length and the skeleton length for one carbon nanotube. The linearity was calculated according to the following formula.

[0245] Linearity = absolute maximum length / frame length

[0246] The absolute maximum length is the distance between two points that are farthest apart in the target pixel group.

[0247] The skeleton length is the length of the free curve formed by the target pixel group.

[0248] Next, for one field of view of the SEM image, the number a of carbon nanotubes with a skeleton length of 1 μm or more and the number b of carbon nanotubes with a skeleton length of 1 μm or more and a linearity of 0.9 or more were calculated. The linearity index was calculated according to the following formula.

[0249] Linearity index (%) = (b / a) × 100

[0250] (3) G / D ratio

[0251] Regarding the G / D ratio of the CNT dispersion composition, a sample was prepared as follows using the CNT dispersion composition shown in Table 1, and the G / D ratio was measured as follows using the sample.

[0252] Preparation of samples: The carbon nanotube dispersion composition was applied to a glass substrate (thickness 2 mm) using a K CONTROL COATER (No. 150) manufactured by KR PRINTCOAT, and dried to obtain a coating film. Drying was performed by standing in an oven (SPHH-201 manufactured by ESPEC CORP.) at 120° C. for 5 minutes.

[0253] Measurement method: CNT was set on a Raman microscope (XploRA, manufactured by Horiba, Ltd.) and measured using a laser wavelength of 532nm. The measurement conditions were set as an acquisition time of 60 seconds, a cumulative number of 2 times, a 10% neutral density filter, a 20x magnification of the objective lens, a confocal aperture of 500, a slit width of 100μm, and a measurement wavelength of 100cm. -1 ~3000cm -1 Among the peaks obtained, the peak at 1560 cm -1 ~1600cm -1 The maximum peak intensity in the range is set as G, which will be at 1310 cm -1 ~1350cm -1 The maximum peak intensity within the range is defined as D, and the G / D ratio is calculated and defined as the G / D ratio of CNT.

[0254] (4) BET specific surface area

[0255] Regarding the BET specific surface area of ​​the CNT dispersion composition, a sample was prepared as follows using the CNT dispersion composition shown in Table 1, and the BET specific surface area was measured as follows using the sample.

[0256] Sample preparation: 100 mL of the carbon nanotube dispersion composition was measured in a 500 mL eggplant-shaped flask, and after freezing in a -95°C ethanol bath for 5 hours using a freeze dryer (manufactured by Tokyo Rikaki Co., Ltd., FDU-1200 / UT-4000), the mixture was dried under reduced pressure of 10 Pa to 30 Pa for 20 hours to obtain carbon nanotube powder. The obtained carbon nanotube powder was then passed through a 60 μm mesh.

[0257] Measurement method: After weighing 0.03 g of CNT using an electronic balance (Sartorius, MSA225S100DI), the mixture was dried at 110°C for 15 minutes while being degassed. Then, the BET specific surface area of ​​the carbon nanotube powder was measured using a fully automatic specific surface area measuring device (Mountech, HM-model 1208). The mass used as the denominator for calculating the specific surface area was set to the mass of the carbon nanotube.

[0258] (5) Complex elastic modulus

[0259] The complex elastic modulus of the CNT dispersion composition was evaluated in the following manner: using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific, Inc.) with a cone of 35 mm in diameter and 2°, dynamic viscoelasticity measurement was performed at 25°C and a frequency of 10 Hz with a strain rate ranging from 0.01% to 5%.

[0260] (6) Phase angle

[0261] The phase angle of the CNT dispersion composition was evaluated in the following manner: using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific, Inc.) with a cone of 35 mm in diameter and 2°, dynamic viscoelasticity was measured at 25°C and a frequency of 10 Hz with a strain rate ranging from 0.01% to 5%.

[0262] <Production of standard positive electrode>

[0263] The standard positive electrode used in the examples and comparative examples described below was produced by the following method.

[0264] First, 68.8 parts by mass of a positive electrode active material (manufactured by BASF TODA Battery Materials, HED (registered trademark) NCM-111 1100), 3.0 parts by mass of acetylene black (manufactured by DENKA Co., Ltd., DENKA BLACK (registered trademark) HS100), and 2.2 parts by mass of PVdF (polyvinylidene fluoride, manufactured by Kureha Battery Material Japan Co., Ltd., Kureha KF polymer W#1300) were added to a 150 cm3 volumetric flask. 3 After adding 15.2 parts by mass of NMP into a plastic container, use a spatula to mix until the powder becomes uniform. Then, add 15.2 parts by mass of NMP and stir at 2000rpm for 30 seconds using a rotation and revolution mixer (degassing Rentaro, ARE-310 manufactured by Thinky). Then, use a spatula to mix the mixture in the plastic container until it becomes uniform, and use the rotation and revolution mixer to stir at 2000rpm for 30 seconds. Then, add 10.8 parts by mass of NMP and stir at 2000rpm for 30 seconds using the rotation and revolution mixer. Finally, use a high-speed stirrer to stir at 3000rpm for 10 minutes to obtain a composite material slurry for the positive electrode.

[0265] Next, the composite material slurry for the positive electrode was applied to a 20 μm thick aluminum foil as a current collector using an applicator to form a coating film. The coating film was then dried in an electric oven at 120°C ± 5°C for 25 minutes to adjust the unit area weight per unit area of ​​the electrode to 20 mg / cm 2 The electrode film (coated film after drying) was rolled using a roller press (manufactured by Thank-Metal Co., Ltd., 3 t hydraulic roller press) to obtain an electrode film with a density of 3.1 g / cm 3 The standard positive electrode.

[0266] <Production of standard negative electrode>

[0267] The standard negative electrode used in the examples and comparative examples described below was produced by the following method.

[0268] Into a 150 ml plastic container, 0.3 parts by mass of acetylene black (DENKA BLACK (registered trademark) HS-100, manufactured by DENKA), 0.5% by mass of CMC (carboxymethyl cellulose) (carboxymethyl cellulose #1190, manufactured by Daicel Finechem, non-volatile matter 100%), and 47.9 parts by mass of water were added, and then stirred at 2,000 rpm for 30 seconds using an autorotational mixer (Degassing Rentaro, ARE-310 manufactured by Thinky). Furthermore, 44.6 parts by mass of artificial graphite (CGB-20, manufactured by Nippon Graphite Industries, non-volatile content 100%) and 5.1 parts by mass of silicon (silicon monoxide, manufactured by Osaka Titanium Technologies, silicon monoxide (SILICON MONOOXIDE), SiO 1.3C 5 μm, non-volatile content 100%) were added as active materials, and stirred at 2,000 rpm for 150 seconds using a rotary revolution mixer (Degassing Rentaro, ARE-310 manufactured by Thinky). Subsequently, 1.6 parts by mass of styrene-butadiene rubber (SBR) (TRD2001, manufactured by JSR) was added, and stirred at 2,000 rpm for 30 seconds using a rotary revolution mixer (Degassing Rentaro, ARE-310 manufactured by Thinky), thereby obtaining a standard negative electrode composite material composition. The nonvolatile content of the standard negative electrode composite material composition is set to 50% by mass.

[0269] <2>About ingredients

[0270] The details of the components used in Examples and Comparative Examples are shown below.

[0271] MIRALON: manufactured by Huntsman, multi-layer CNT

[0272] CNT (A): CNT (A) synthesized by the following synthesis method, multilayer CNT

[0273] JENOTUBE 10B: JENOTUBE 10B (manufactured by JEIO, multi-layer CNT)

[0274] NTF01: NTF01 (manufactured by Hamamatsu Carbonics, multilayer CNT)

[0275] Dispersant 1: Dispersant synthesized by the following synthesis method

[0276] Dispersant 2: Dispersant prepared by the following preparation method

[0277] Na2CO3: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0278] NaOH: manufactured by Tokyo Chemical Industry Co., Ltd., purity > 98.0%

[0279] CMC: Carboxymethyl cellulose #1190 (manufactured by Daicel Finechem)

[0280] Styrene butadiene rubber: TRD2001 (manufactured by JSR Corporation)

[0281] HNBR: Therban 3406 (hydrogenated nitrile rubber manufactured by ARLANXEO)

[0282] PVdF: Solef 5130 (polyvinylidene fluoride resin manufactured by Solvay)

[0283] Polytetrafluoroethylene: POLYFLON PTFE D-210C (manufactured by Daikin Industries)

[0284] <Synthesis of CNT(A)>

[0285] The following describes a method for synthesizing CNT (A).

[0286] A catalyst containing iron nitrate is deposited on a silicon wafer (substrate) to form a catalyst layer containing a metal catalyst on the surface of the substrate. Then, a silicon wafer carrying the catalyst is set in the central part of a horizontal reaction tube with a volume of 10L that can be pressurized and can be heated by an external heater. While injecting nitrogen, exhaust is performed, and the air in the reaction tube is replaced by nitrogen so that the environment in the horizontal reaction tube has an oxygen concentration of less than 1% by volume. Then, the reaction tube is heated by an external heater until the center temperature in the horizontal reaction tube becomes 680°C. After reaching 680°C, acetylene gas as a carbon source is introduced into the reaction tube at a flow rate of 2L per minute, so that it is contacted and reacted for 15 hours. After the reaction is completed, the gas in the reaction tube is replaced by nitrogen, and the temperature of the reaction tube is cooled to less than 100°C and taken out by replacing the gas in the reaction tube with nitrogen, thereby obtaining CNT (A).

[0287] <Synthesis of Dispersant 1>

[0288] In a reaction vessel including a thermometer, a condenser, and a stirrer, 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, heated to 70°C, and stirred at 70°C for 300 minutes (5 hours). When the conversion rate reaches 90% or more, the reaction is cooled to terminate the reaction. Then, unreacted raw materials are 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 are placed in a four-necked separable flask, and the disperser is used to rotate it 1,000 times. At this time, the polymer aqueous solution is added dropwise for 1 hour. The generated white precipitate is removed by filtration and dried under reduced pressure to obtain a dispersant 1.

[0289] <Preparation of dispersant 2 solution>

[0290] Capacity 1000cm 3In a plastic container, 475 parts by mass of NMP and 25 parts by mass of NaOH (manufactured by Tosoh Co., Ltd., Tosohpearl) were added, and a high shear mixer (L5M-A, manufactured by SILVERSON) equipped with a fine emulsor screen was used to disperse at a speed of 9000 rpm until the whole became uniform, and then a filter bell was used to pass through a nylon filter with a mesh of 150 μm to make a NaOH dispersion. 780 parts by mass of NMP were loaded into a reaction container including a gas introduction pipe, a thermometer, a condenser, and a stirrer, and replaced with nitrogen. Then, the reaction container was heated to 80°C, 200 parts by mass of HNBR (Therban 3406) were added, and stirred until the HNBR was completely dissolved. Thereafter, 20 parts by mass of a NaOH dispersion was added, and the mixture was stirred while adding air, and the reaction container was kept at 80° C. for 12 hours while being heated to obtain a dispersant 2 solution (solid content concentration: 20.1% by mass).

[0291] <4> CNT dispersion composition

[0292] (Example 1-1)

[0293] Add 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 to a stainless steel container, and stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate, and then install a standard square hole head on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stir at a speed of 7,000rpm until it becomes uniform. The dispersed liquid is supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment is performed. The dispersion treatment is performed 25 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 1.

[0294] (Example 1-2)

[0295] The carbon nanotubes were replaced with CNT(A), and dispersion was performed in the same manner as in Example 1 to obtain a dispersion composition 2.

[0296] (Example 1-3)

[0297] 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.60 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate were added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. 80 g of the dispersed liquid and 120 g of zirconium oxide beads (bead diameter 1 mmφ) were loaded into a glass bottle (M-225, manufactured by Kashiwa Glass Co., Ltd.), and a coating regulator manufactured by Red Devil was used for 5 hours of dispersion treatment. Then, the dispersed liquid after the zirconia beads were separated was supplied to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) for a circulating dispersion treatment. The dispersion treatment was performed 20 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 3.

[0298] (Examples 1-4)

[0299] Add 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 to a stainless steel container, and stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add 0.60 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate, and then install a standard square hole head on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stir at a speed of 7,000 rpm until it becomes uniform. The dispersed liquid is supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment is performed. The dispersion treatment is performed 20 times using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. Then, 80 g of the dispersed liquid and 120 g of zirconium oxide beads (bead diameter 1 mmφ) were placed in a glass bottle (M-225, manufactured by Kashiwayo Glass Co., Ltd.), and a paint conditioner manufactured by Red Devil was used to perform a dispersion treatment for 5 hours. The zirconium oxide beads were then separated to obtain a dispersed composition 4.

[0300] (Examples 1-5)

[0301] 14.4 parts by mass of dispersant 1, 16 parts by mass of MIRALON, and 69.6 parts by mass of ion exchange water were added to Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.), and after dispersion for 3 hours, the mixture was transferred to a stainless steel container, 2565.6 parts by mass of ion exchange water and 1.07 parts by mass of sodium carbonate were added, and a high shear mixer (L5M-A, manufactured by SILVERSON) was equipped with a standard square hole head, and stirred at a speed of 7,000 rpm until the mixture became uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 25 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 5.

[0302] (Examples 1-6)

[0303] 14.4 parts by mass of dispersant 1, 16 parts by mass of MIRALON, and 69.6 parts by mass of ion exchange water were added to Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.), and after dispersion for 3 hours, the mixture was transferred to a stainless steel container, 2565.6 parts by mass of ion exchange water and 1.07 parts by mass of sodium carbonate were added, and a high shear mixer (L5M-A, manufactured by SILVERSON) was equipped with a standard square hole head, and stirred at a speed of 7,000 rpm until the mixture became uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 20 times using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. Next, 80 g of the dispersed liquid and 120 g of zirconium oxide beads (bead diameter 1 mmφ) were placed in a glass bottle (M-225, manufactured by Kashiwayo Glass Co., Ltd.), and a dispersion treatment was performed for 5 hours using a paint conditioner manufactured by Red Devil Co., Ltd., and then the zirconium oxide beads were separated to obtain a dispersed composition 6.

[0304] (Examples 1-7)

[0305] 14.4 parts by mass of dispersant 1, 16 parts by mass of MIRALON, and 69.6 parts by mass of ion exchange water were placed in Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.), dispersed for 3 hours, and then transferred to a stainless steel container, 2565.6 parts by mass of ion exchange water and 1.07 parts by mass of sodium carbonate were added, and a high shear mixer (L5M-A, manufactured by SILVERSON) was equipped with a standard square hole head, and stirred at a speed of 7,000 rpm until it became uniform. Then, 80 g of the dispersion and 120 g of zirconium oxide beads (bead diameter 1 mmφ) were placed in a glass bottle (M-225, manufactured by Kashiwa Glass Co., Ltd.), and a coating conditioner manufactured by Red Devil Co., Ltd. was used for 5 hours of dispersion treatment, and then the zirconium oxide beads were separated. The dispersion was supplied to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) for a circulating dispersion treatment. The dispersion treatment was performed 20 times using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 7.

[0306] (Example 1-8)

[0307] Add ion exchange water 98.82 parts by mass, dispersant 1 0.54 parts by mass to a stainless steel container, stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add CNT (A) 0.6 parts by mass and sodium carbonate 0.04 parts by mass, and then install a standard square hole head to the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), stir at a speed of 7,000rpm until it becomes uniform. From a stainless steel container, a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) is supplied with a dispersed liquid via a pipe, and a cyclic dispersion treatment is performed. The dispersion treatment is to use a single nozzle chamber to perform 40 passes at a nozzle diameter of 0.25mm and a pressure of 100MPa to obtain a dispersed composition 8.

[0308] (Example 1-9)

[0309] 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate were added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 20 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 9.

[0310] (Examples 1-10)

[0311] Add ion exchange water 98.82 parts by mass and dispersant 1 0.54 parts by mass to a stainless steel container, and stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate, and then install a standard square hole head on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stir at a speed of 7,000rpm until it becomes uniform. The dispersed liquid is supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment is performed. The dispersion treatment is performed 40 times using a single nozzle chamber at a nozzle diameter of 0.25mm and a pressure of 100MPa to obtain a dispersed composition 10.

[0312] (Example 1-11)

[0313] 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate were added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 15 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 11.

[0314] (Examples 1-12)

[0315] Add 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 to a stainless steel container, and stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate, and then install a standard square hole head on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stir at a speed of 7,000rpm until it becomes uniform. The dispersed liquid is supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment is performed. The dispersion treatment is performed 55 times using a single nozzle chamber at a nozzle diameter of 0.25mm and a pressure of 100MPa to obtain a dispersed composition 12.

[0316] (Comparative Example 1-1)

[0317] The carbon nanotubes were replaced with JENOTUBE 10B and dispersed in the same manner as in Example 1 to obtain a comparative dispersion composition 1. The material ratios were 2.5 parts by mass of JENOTUBE 10B, 96.3 parts by mass of ion exchange water, 1.0 parts by mass of dispersant 1, and 0.13 parts by mass of sodium carbonate.

[0318] (Comparative Example 1-2)

[0319] The carbon nanotubes were replaced with NTF01 and dispersed in the same manner as in Example 1 to obtain a comparative dispersion composition 2.

[0320] (Comparative Examples 1-3)

[0321] 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate were added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 5 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a comparative dispersion composition 3.

[0322] (Comparative Examples 1-4)

[0323] Add 98.82 parts by mass of ion exchange water and 0.54 parts by mass of dispersant 1 to a stainless steel container, and stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add 0.6 parts by mass of MIRALON and 0.04 parts by mass of sodium carbonate, and then install a standard square hole head on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stir at a speed of 7,000rpm until it becomes uniform. The dispersed liquid is supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment is performed. The dispersion treatment is performed 80 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a comparative dispersion composition 4.

[0324] (Example 1-101)

[0325] 96.40 parts by mass of N-methyl-2-pyrrolidone (NMP) and 3.0 parts by mass of dispersant 2 solution (0.60 parts by mass of HNBR, 0.03 parts by mass of NaOH, and 2.37 parts by mass of NMP) were added to a stainless steel container, and stirred with a disperser until the mixture became uniform. Then, while stirring with a disperser, 0.60 parts by mass of MIRALON was added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until the mixture became uniform. The dispersed liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 25 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 101 .

[0326] (Example 1-102)

[0327] Add 96.40 parts by mass of N-methyl-2-pyrrolidone (NMP) and 3.0 parts by mass of dispersant 2 solution to a stainless steel container, and stir with a disperser until it becomes uniform. Then, while stirring with a disperser, add 0.60 parts by mass of CNT (A), and then install a standard square hole head to the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stir at a speed of 7,000rpm until it becomes uniform. From the stainless steel container, the high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) is supplied with a dispersed liquid via a pipe, and a cyclic dispersion treatment is performed. The dispersion treatment is performed by 25 passes using a single nozzle chamber at a nozzle diameter of 0.25mm and a pressure of 100MPa to obtain a dispersed composition 102.

[0328] (Example 1-103)

[0329] 96.40 parts by mass of N-methyl-2-pyrrolidone (NMP) and 3.0 parts by mass of dispersant 2 solution were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.60 parts by mass of MIRALON was added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 15 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 103.

[0330] (Example 1-104)

[0331] 96.40 parts by mass of N-methyl-2-pyrrolidone (NMP) and 3.0 parts by mass of dispersant 2 solution were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.60 parts by mass of MIRALON was added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 55 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a dispersed composition 104.

[0332] (Comparative Example 1-101)

[0333] 96.40 parts by mass of N-methyl-2-pyrrolidone (NMP) and 3.0 parts by mass of dispersant 2 solution (0.60 parts by mass of HNBR, 0.03 parts by mass of NaOH, and 2.37 parts by mass of NMP) were added to a stainless steel container, and stirred with a disperser until the mixture became uniform. Then, while stirring with a disperser, 0.60 parts by mass of MIRALON was added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until the mixture became uniform. The dispersed liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed five times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a comparative dispersion composition 101 .

[0334] (Comparative Example 1-102)

[0335] 96.40 parts by mass of N-methyl-2-pyrrolidone (NMP) and 3.0 parts by mass of dispersant 2 solution were added to a stainless steel container, and stirred with a disperser until uniform. Then, while stirring with a disperser, 0.60 parts by mass of MIRALON was added, and a standard square hole head was installed on the disperser and high shear mixer (L5M-A, manufactured by SILVERSON), and stirred at a speed of 7,000 rpm until uniform. The dispersed liquid was supplied from the stainless steel container to a high pressure homogenizer (Starburst Labo HJP-17007, manufactured by SUGINO Machine) via a pipe, and a circulating dispersion treatment was performed. The dispersion treatment was performed 80 times using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa to obtain a comparative dispersion composition 102.

[0336] <5> Preparation of CNT resin composition and composite material slurry

[0337] (Composite material slurry for negative electrode 1)

[0338] In capacity 150cm 3In a plastic container, 5.7 parts by mass of the dispersed composition 1, 11.4 parts by mass of an aqueous solution of 2% carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., #1190, recorded as CMC (hereinafter the same)) and 10.7 parts by mass of ion exchange water were measured and dissolved. Then, these were stirred at 2000 rpm for 30 seconds using a self-rotation and revolution mixer (degassing Rentaro, ARE-310 manufactured by Thinky). Then, 2.2 parts by mass of silicon monoxide (manufactured by Osaka Titanium Technologies Co., Ltd., silicon monoxide (SILICON MONOOXIDE), SiO 1.3C 5μm) were added, and the self-rotation and revolution mixer was used to stir at 2000 rpm for 5 minutes. Furthermore, 19.9 parts by mass of artificial graphite (CGB-20, manufactured by Nippon Graphite Industries, Ltd.) was added, and the mixture was stirred at 2000 rpm for 10 minutes using the above-mentioned rotation and revolution mixer.

[0339] Furthermore, 0.7 parts by mass of styrene butadiene rubber (manufactured by JSR Co., Ltd., TRD2001, non-volatile content 48%, recorded as SBR in the table (the same below)) was added, and the mixture was stirred at 2000 rpm for 30 seconds using the autorotating and revolving mixer to obtain a negative electrode composite material slurry 1 having a non-volatile content mass % as recorded in Table 2.

[0340] (Composite material slurry for negative electrode 2 to 7)

[0341] Dispersion composition 1 was changed to dispersion compositions 2 to 7, and negative electrode composite material slurries 2 to 7 were obtained by the same process as that of negative electrode composite material slurry 1.

[0342] (Comparative negative electrode composite material slurry 1)

[0343] The same procedure as that of negative electrode composite material slurry 1 was followed, and the material ratios were changed to 4.5 parts by mass of comparative dispersion composition 1, 11.3 parts by mass of an aqueous solution in which 2% by mass of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., #1190) was dissolved, 11.8 parts by mass of ion exchange water, 2.2 parts by mass of silicon monoxide (manufactured by Osaka Titanium Technologies Co., Ltd., silicon monoxide (SILICONMONOOXIDE), SiO 1.3C 5μm), 19.6 parts by mass of artificial graphite (manufactured by Nippon Graphite Industries, Ltd., CGB-20), and 0.7 parts by mass of styrene butadiene rubber (manufactured by JSR Co., Ltd., TRD2001), thereby obtaining comparative negative electrode composite material slurry 1.

[0344] (Comparative negative electrode composite material slurry 2)

[0345] The same procedure as that of negative electrode composite material slurry 1 was followed, and the material ratios were changed to 11.4 parts by mass of comparative dispersion composition 2, 11.4 parts by mass of an aqueous solution in which 2% by mass of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., #1190) was dissolved, 11.8 parts by mass of ion exchange water, 2.2 parts by mass of silicon monoxide (manufactured by Osaka Titanium Technologies Co., Ltd., silicon monoxide (SILICON MONOOXIDE), SiO 1.3C 5μm), 19.9 parts by mass of artificial graphite (manufactured by Nippon Graphite Industries, Ltd., CGB-20), and 0.7 parts by mass of styrene butadiene rubber (manufactured by JSR Co., Ltd., TRD2001), thereby obtaining comparative negative electrode composite material slurry 2.

[0346] (Composite material slurry for negative electrode 8-12)

[0347] Dispersion composition 1 was changed to dispersion compositions 8 to 12, and negative electrode composite material slurries 8 to 12 were obtained by the same process as that of negative electrode composite material slurry 1.

[0348] (Comparative negative electrode composite material slurry 3 to 4)

[0349] Comparative dispersion composition 1 was changed to comparative dispersion compositions 3 and 4, and comparative negative electrode composite material slurries 3 and 4 were obtained by the same procedure as that of comparative composite material slurry 1 for negative electrodes.

[0350] (Composite material slurry for positive electrode 1)

[0351] In capacity 150cm 3 In a plastic container, 8.2 parts by mass of the dispersion composition 1, 0.3 parts by mass of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., #1190), and 9.3 parts by mass of ion exchange water were measured, and stirred at 2,000 rpm for 30 seconds using a rotary revolution mixer (degassing Rentaro manufactured by Thinky, ARE-310). Then, 32.0 parts by mass of LFP (LFP-400, manufactured by BASF, non-volatile component 100%) as a positive electrode active material was added, and stirred at 2,000 rpm for 5 minutes using a rotary revolution mixer (degassing Rentaro manufactured by Thinky, ARE-310). Furthermore, 0.8 parts by mass of polytetrafluoroethylene (manufactured by Daikin Industries, POLYFLON PTFE D-210C, non-volatile content 60%, recorded as PTFE in the table (the same below)) was then added, and a rotary mixer (degassing Rentaro, ARE-310 manufactured by Thinky) was used to stir at 2,000 rpm for 30 seconds to obtain a positive electrode composite material slurry 1 having a non-volatile content mass % as recorded in Table 3.

[0352] (Composite material slurry for positive electrode 2 to 7)

[0353] The dispersion composition was changed to dispersion composition 2 to 7, and the same process as that of the positive electrode composite material slurry 1 was followed to obtain positive electrode composite material slurries 2 to 7.

[0354] (Comparative positive electrode composite material slurry 1)

[0355] The same process as the positive electrode composite material slurry 1 was followed, and the material ratio was changed to 6.5 parts by mass of the comparative dispersion composition 1, 0.3 parts by mass of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., #1190), 11.0 parts by mass of ion exchange water, 31.4 parts by mass of LFP (LFP-400, manufactured by BASF, non-volatile component 100%), and 0.8 parts by mass of polytetrafluoroethylene (manufactured by Daikin Industries, Ltd., POLYFLON PTFE D-210C, non-volatile component 60%), thereby obtaining a comparative positive electrode composite material slurry 1.

[0356] (Comparative positive electrode composite material slurry 2)

[0357] The same process as the positive electrode composite material slurry 1 was followed, and the material ratio was changed to 16.5 parts by mass of the comparative dispersion composition 2, 0.3 parts by mass of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., #1190), 1.1 parts by mass of ion exchange water, 31.9 parts by mass of LFP (LFP-400, manufactured by BASF, non-volatile component 100%), and 0.8 parts by mass of polytetrafluoroethylene (manufactured by Daikin Industries, Ltd., POLYFLON PTFE D-210C, non-volatile component 60%), thereby obtaining a comparative positive electrode composite material slurry 2.

[0358] (Positive electrode composite material slurry 101)

[0359] In capacity 150cm 3 In a plastic container, 31.1 parts by mass of NMP solution and 0.4 parts by mass of NMP were dissolved with 8% by mass of PVdF (polyvinylidene fluoride, manufactured by Solvey, Solef #5130). Then, 24.9 parts by mass of the dispersed composition 101 were added, and a self-rotation and revolution mixer (degassing Rentaro, ARE-310) was used to stir at 2000 rpm for 30 seconds. Furthermore, 96.7 parts by mass of the positive electrode active material NCM1 were added thereafter, and a self-rotation and revolution mixer (degassing Rentaro, ARE-310) was used to stir at 2000 rpm for 2.5 minutes to obtain a positive electrode composite material slurry 101.

[0360] (Positive Electrode Composite Material Slurries 102 to 104, Comparative Positive Electrode Composite Material Slurries 101 to 102)

[0361] The dispersion composition 101 was changed to the dispersion compositions 102 to 104 and the comparative dispersion compositions 101 to 102, and the positive electrode composite material slurries 102 to 104 and the comparative positive electrode composite material slurries 101 to 102 were obtained respectively by the same process as that of the positive electrode composite material slurry 101.

[0362] <6> Fabrication and evaluation of electrode membrane

[0363] <6-1> Negative electrode film

[0364] (Example 2-1: Negative Electrode 1)

[0365] The obtained negative electrode composite material slurry 1 was applied to a copper foil with a thickness of 20 μm using an applicator, and the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to prepare an electrode film. Thereafter, 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 was 10 mg / cm 2 The density of the composite material layer after calendering is 1.6g / cm 3 .

[0366] (Examples 2-2 to 2-12: Negative Electrodes 2 to 12)

[0367] Negative electrodes 2 to 12 were obtained by replacing negative electrode composite material slurry 1 with negative electrode composite material slurries 2 to 12 and performing the same process as that for negative electrode 1.

[0368] (Comparative Examples 2-1 to 2-4: Comparative Negative Electrodes 1 to 4)

[0369] The negative electrode composite material slurry 1 was changed to comparative negative electrode composite material slurries 1 to 4, and comparative negative electrodes 1 to 4 were obtained by the same process as that of the negative electrode 1.

[0370] <6-2>Positive electrode film

[0371] (Example 3-1: Positive Electrode 1)

[0372] The obtained positive electrode composite material slurry 1 was applied onto an aluminum foil having a thickness of 20 μm using an applicator, and then dried in an electric oven at 120° C.±5° C. for 25 minutes to prepare an electrode film.

[0373] Thereafter, the electrode film was rolled using a roller press (manufactured by Thank-Metal, 3 t 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 was 20 mg / cm 2 The density of the composite material layer after calendering is 2.1 g / cc.

[0374] (Examples 3-2 to 3-7, Comparative Examples 3-1 to 3-2: Positive Electrodes 2 to 7, Comparative Positive Electrodes 1 to 2)

[0375] Positive electrode composite material slurry 1 was replaced with positive electrode composite material slurries 2 to 7 and comparative positive electrode composite material slurries 1 to 2, and positive electrodes 2 to 7 and comparative positive electrodes 1 to 2 were obtained by the same process as that of positive electrode 1.

[0376] (Examples 3-101 to 3-104, Comparative Examples 3-101 to 3-102: Positive Electrodes 101 to 104, Comparative Positive Electrodes 101 to 102)

[0377] Positive electrode composite material slurry 1 was changed to positive electrode composite material slurries 101 to 104 and comparative positive electrode composite material slurries 101 to 102, and positive electrodes 101 to 104 and comparative positive electrodes 101 to 102 were obtained by the same process as that of positive electrode 1.

[0378] <8>Laminated lithium-ion secondary battery

[0379] (Example 4-1: Negative Electrode Evaluation Battery 1)

[0380] The negative electrode 1 and the standard positive electrode are punched out into 50mm×45mm and 45mm×40mm, respectively. The punched negative electrode and the standard positive electrode, and the separator (porous polypropylene film) inserted between them are inserted into an aluminum laminate bag and dried in an electric oven at 70°C for 1 hour. Then, a non-aqueous electrolyte is prepared in a glove box filled with argon. Specifically, first, a mixed solvent is prepared by mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a ratio of 1:1:1 (volume ratio). Next, 1 mass part of VC (vinylene carbonate) and FEC (fluoroethylene carbonate) are added as additives to 100 mass parts of the mixed solvent, and LiPF6 is dissolved at a concentration of 1M to obtain a non-aqueous electrolyte. Next, 2 mL of a non-aqueous electrolyte was injected into the aluminum laminate bag, and the aluminum laminate was sealed to prepare a laminated lithium ion secondary battery (battery 1 for negative electrode evaluation).

[0381] (Examples 4-2 to 4-12, and Comparative Examples 4-1 to 4-4)

[0382] Laminated lithium ion secondary batteries (negative electrode evaluation batteries) 2 to 12 and comparative negative electrode evaluation batteries 1 to 4 were prepared in the same manner as in Example 4-1 except that negative electrode 1 in Example 4-1 was changed to negative electrodes 2 to 12 and comparative negative electrodes 1 to 4.

[0383] (Examples 5-1 to 5-7, 5-101 to 5-104, and Comparative Examples 5-1 to 5-2, 5-101 to 5-102)

[0384] In the preparation of a laminated lithium-ion secondary battery using a positive electrode and a standard negative electrode, the negative electrode in Example 4-1 is set as the standard negative electrode, and the positive electrode is changed to positive electrodes 1 to 7, positive electrodes 101 to 104, specific correction electrodes 1 to 2, and specific correction electrodes 101 to 102. Except for this, the same method as Example 4-1 is used to obtain positive electrode evaluation batteries 1 to 7, positive electrode evaluation batteries 101 to 104, specific correction electrode evaluation batteries 1 to 2, and specific correction electrode evaluation batteries 101 to 102, respectively.

[0385] The rate characteristics and cycle characteristics of the laminated lithium ion secondary battery were evaluated. The evaluation criteria are shown below. The evaluation results are shown in Tables 4 and 5.

[0386] (Rate characteristics evaluation method of secondary battery)

[0387] The obtained secondary battery for negative electrode evaluation and the secondary battery for positive electrode evaluation were placed in a constant temperature room at 25°C, and a charge and discharge device (manufactured by Hokuto Electric Co., Ltd., SM-8) was used for charge and discharge measurement. Constant current and constant voltage charging (cutoff current 1mA (0.02C)) was performed at a charge end voltage of 4.3V at a charging current of 10mA (0.2C), and then constant current discharge was performed at a discharge current of 10mA (0.2C) at a discharge end voltage of 3V. After repeating the above operation 3 times, constant current and constant voltage charging (cutoff current (1mA, 0.02C)) was performed at a charge current of 10mA (0.2C) at a charge end voltage of 4.3V, and constant current discharge was performed at a discharge current of 0.2C and a discharge current of 3C until the discharge end voltage reached 3.0V, and the discharge capacity was calculated respectively. The rate characteristic is the ratio of the 0.2C discharge capacity to the 3C discharge capacity, which can be expressed by the following formula 1.

[0388] (Formula 1) Rate characteristics = 3C discharge capacity / 3rd 0.2C discharge capacity × 100 (%)

[0389] <Judgment Criteria>

[0390] ◎: Rate characteristics are 80% or more (excellent)

[0391] ○: Rate characteristic is 70% or more and less than 80% (good)

[0392] △: Rate characteristic is 60% or more and less than 70% (defective)

[0393] (Method for evaluating cycle characteristics of secondary batteries)

[0394] The obtained secondary battery for negative electrode evaluation and the secondary battery for positive electrode evaluation were placed in a constant temperature room at 25°C, and a charge and discharge device (manufactured by Hokuto Electric, SM-8) was used for charge and discharge measurement. Constant current and constant voltage charging (cut-off current 2.5mA (0.05C)) was performed at a charging current of 25mA (0.5C) with a charge termination voltage of 4.3V, and then constant current discharge was performed at a discharge current of 25mA (0.5C) with a discharge termination voltage of 3V. The operation was repeated 200 times. The cycle characteristics are the ratio of the 0.5C discharge capacity of the third time at 25°C to the 0.5C discharge capacity of the 200th time, which can be expressed by the following formula 2.

[0395] (Formula 2) Cycle characteristics = 200th 0.5C discharge capacity / 3rd 0.5C discharge capacity × 100 (%)

[0396] <Judgment Criteria>

[0397] ◎◎: 90% or more (best)

[0398] ◎: 85% or more (excellent)

[0399] ○: 80% or more and less than 85% (good)

[0400] ×: Less than 80% (defective)

[0401]

[0402]

[0403]

[0404]

[0405]

[0406] [Table 4]

[0407] Table 4

[0408]

[0409] [Table 5]

[0410] Table 5

[0411]

[0412] As shown in the table, Examples in which the physical property values ​​of CNTs observed in the CNT dispersion composition fell within the prescribed ranges can provide secondary batteries that exhibit good rate characteristics and cycle characteristics.

[0413] For example, in Comparative Example 4-1, since the linearity index of the CNT in the CNT dispersed composition is low, it is expected that the number of particles of the active material connected to a CNT in the secondary battery is small. In this case, it is believed that if charging and discharging are repeated in the secondary battery, the volume of the active material changes, and the proportion of the particles of the active material connected to each other by CNT decreases, and the cycle characteristics decrease. In Comparative Example 4-2, it is believed that the average outer diameter of the CNT in the CNT dispersed composition is large, so the conductivity of the CNT in the secondary battery decreases, and the rate characteristics decrease. The same tendency is also found in Comparative Examples 5-1 and 5-2 and other Comparative Examples.

Claims

1. A carbon nanotube dispersion composition comprising: carbon nanotubes, a dispersant, and a solvent, and satisfying the following (1) and (2), (1) the average outer diameter of the carbon nanotubes calculated from a scanning electron microscope image of the carbon nanotubes contained in the carbon nanotube dispersion composition is 15 nm or more and 50 nm or less; (2) When the pixel group of the scanning electron microscope image obtained by observing the carbon nanotubes contained in the carbon nanotube dispersion composition is set as the carbon nanotube, and the value obtained by dividing the distance between the two farthest points (absolute maximum length) by the length of the free curve (skeleton length) is set as the linearity, for carbon nanotubes with a skeleton length of more than 1 μm, the number ratio of carbon nanotubes with a linearity of more than 0.9 is more than 40% and less than 90%.

2. The carbon nanotube dispersion composition according to claim 1, wherein (3) in the Raman spectrum of the coating film of the carbon nanotube dispersion composition, the carbon nanotube dispersion composition has a wavelength of 1560 cm -1 ~1600cm -1 The maximum peak intensity in the range of 1310 cm -1 ~1350cm -1 When the maximum peak intensity in the range of is defined as D, the G / D ratio is 1.0 to 20.

0.

3. The carbon nanotube dispersion composition according to claim 1, wherein (4) after freeze-drying the carbon nanotube dispersion composition, the Buerter specific surface area of ​​the powder passing through a 60 μm sieve relative to the mass of the carbon nanotubes is 50 m 2 / g~130m 2 / g. 4 . The carbon nanotube dispersion composition according to claim 1 , wherein (5) the complex elastic modulus at 25° C. and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is 4 Pa ​​or more and 200 Pa or less. 5 . The carbon nanotube dispersion composition according to claim 1 , wherein (6) a phase angle at 25° C. and a frequency of 10 Hz obtained by dynamic viscoelasticity measurement is 3° or more and 60° or less. 6 . A carbon nanotube resin composition, comprising: the carbon nanotube dispersion composition according to claim 1 , and a binder. 7 . A composite material slurry comprising: the carbon nanotube dispersion composition according to claim 1 , a binder, and an active substance. 8 . An electrode film, which is a coating film of a composite material slurry, wherein the composite material slurry comprises the carbon nanotube dispersion composition according to claim 1 , a binder, and an active material. 9 . A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises the electrode film according to claim 8 .

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