Positive electrode composition, positive electrode forming coating solution, positive electrode, battery, conductive material, slurry, method for manufacturing positive electrode forming coating solution, and method for manufacturing positive electrode.

Abstract

A positive electrode composition comprising an active material, a binder material, and a conductive material, wherein the conductive material comprises: carbon black (A) with an average primary particle size of 17 nm or more and 30 nm or less; a first carbon nanotube (B) with a peak ratio (D / G) of 0.3 or more and 1.4 or less in the Raman spectrum of the D band to the G band; and a second carbon nanotube (C) with a peak ratio (D / G) of less than 0.3 in the Raman spectrum of the D band to the G band.

Description

Technical Field

[0001] This disclosure relates to a positive electrode composition, a coating liquid for forming a positive electrode, a positive electrode, a battery, a conductive material, a slurry, a method for manufacturing the coating liquid for forming a positive electrode, and a method for manufacturing a positive electrode. Background Technology

[0002] With the increasing prominence of environmental and energy issues, technological development aimed at achieving a low-carbon society that reduces dependence on fossil fuels is flourishing. This technological development encompasses a wide range of areas, including the development of low-emission vehicles such as hybrid and electric vehicles, the development of natural energy power generation / storage systems such as solar and wind power, and the development of next-generation power grids that provide efficient power supply and reduce transmission losses.

[0003] One of the key components required by these technologies is the battery, which demands high energy density to enable system miniaturization. Furthermore, it requires high output characteristics to provide stable power regardless of ambient temperature. Additionally, it requires good cycle characteristics to withstand long-term use. Therefore, the replacement of traditional lead-acid, nickel-cadmium, and nickel-metal hydride batteries with lithium-ion rechargeable batteries, which offer higher energy density, output characteristics, and cycle performance, is rapidly progressing.

[0004] Traditionally, the positive electrode of a lithium-ion secondary battery is manufactured by coating a positive electrode paste containing a positive electrode active material, a conductive material, and a binder (also known as a binder) onto a current collector. Lithium-containing composite oxides such as lithium cobalt oxide and lithium manganese oxide have been used as positive electrode active materials. Furthermore, because the conductivity of positive electrode active materials is poor, conductive materials such as carbon black are added to the positive electrode paste to impart conductivity (e.g., Patent Document 1).

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2008-227481 Summary of the Invention

[0006] The problem the invention aims to solve In recent years, there has been a demand to further improve the performance of batteries such as lithium-ion rechargeable batteries.

[0007] One objective of this disclosure is to provide a positive electrode composition for a battery that achieves excellent cycle characteristics. Furthermore, one objective of this disclosure is to provide a positive electrode forming solution for a battery that achieves excellent cycle characteristics. Furthermore, one objective of this disclosure is to provide a positive electrode for a battery that achieves excellent cycle characteristics. Furthermore, one objective of this disclosure is to provide a battery with excellent cycle characteristics. Furthermore, one objective of this disclosure is to provide a conductive material for a battery that achieves excellent cycle characteristics and a slurry comprising the conductive material. Moreover, one objective of this disclosure is to provide a method for manufacturing the aforementioned positive electrode forming solution, which allows for easy manufacturing of the positive electrode forming solution, and a method for manufacturing the aforementioned positive electrode.

[0008] Technical means to solve the problem This disclosure relates to, for example, the following [1] to

[14] .

[0009] [1] A positive electrode composition comprising an active material, a binder material, and a conductive material, wherein the conductive material comprises: Carbon black (A) with an average primary particle size of 17 nm or more and 30 nm or less. First carbon nanotubes (B) with a D-to-G band peak ratio (D / G) greater than 0.3 and less than 1.4 in Raman spectra, and The second carbon nanotube (C) with a peak ratio (D / G) of less than 0.3 in the Raman spectrum of the D band to the G band.

[0010] [2] According to the positive electrode composition of [1], wherein the carbon black (A) is selected from the group consisting of furnace black, acetylene black and Ketjen black.

[0011] [3] According to the cathode composition described in [1] or [2], wherein the BET specific surface area of ​​the carbon black (A) is 100 m². 2 / g or more and 900m 2 / g or less.

[0012] [4] According to any one of [1] to [3], the content of carbon black (A) is 30% by mass or more and 90% by mass or less, based on the total amount of the conductive material.

[0013] [5] According to any one of [1] to [4], the content of the first carbon nanotube (B) is 5% by mass or more and 50% by mass or less, based on the total amount of the conductive material.

[0014] [6] According to any one of [1] to [5], the content of the second carbon nanotube (C) is 1% by mass or more and 45% by mass or less, based on the total amount of the conductive material.

[0015] [7] A coating liquid for forming a positive electrode, comprising any one of [1] to [6] a positive electrode composition and a dispersion medium.

[0016] [8] A positive electrode comprising any one of [1] to [6] of the positive electrode composition.

[0017] [9] A battery having the positive electrode described in [8].

[0018]

[10] A conductive material comprising: Carbon black (A) with an average primary particle size of 17 nm or more and 30 nm or less. First carbon nanotubes (B) with a D-to-G band peak ratio (D / G) greater than 0.3 and less than 1.4 in Raman spectra, and The second carbon nanotube (C) with a peak ratio (D / G) of less than 0.3 in the Raman spectrum of the D band to the G band.

[0019]

[11] A slurry comprising the conductive material and dispersion medium described in

[10] .

[0020]

[12] A method for manufacturing a coating liquid for forming a positive electrode includes a mixing step of mixing an active material, a binder, a conductive material and a dispersion medium, wherein the conductive material comprises: carbon black (A) with an average primary particle size of 17 nm or more and 30 nm or less, a first carbon nanotube (B) with a peak ratio (D / G) of 0.3 or more and 1.4 or less in the Raman spectrum of the D band to the G band, and a second carbon nanotube (C) with a peak ratio (D / G) of less than 0.3 in the Raman spectrum of the D band to the G band.

[0021]

[13] According to the manufacturing method described in

[12] , the mixing step is a step of mixing the active substance, the binder solution containing the binder material, the slurry (A) containing the carbon black (A), the slurry (B) containing the first carbon nanotube (B), and the slurry (C) containing the second carbon nanotube (C).

[0022]

[14] A method for manufacturing a positive electrode includes: applying a positive electrode forming liquid manufactured by the manufacturing method described in

[12] or

[13] onto a current collector, and forming an agent layer containing the active material, the binder material and the conductive material on the current collector.

[0023] The effects of the invention According to this disclosure, a positive electrode composition for a battery capable of achieving excellent cycle characteristics is provided. Furthermore, according to this disclosure, a coating liquid for forming a positive electrode for a battery capable of achieving excellent cycle characteristics is provided. Furthermore, according to this disclosure, a positive electrode for a battery capable of achieving excellent cycle characteristics is provided. Furthermore, according to this disclosure, a battery with excellent cycle characteristics is provided. Furthermore, according to this disclosure, a conductive material for a battery capable of achieving excellent cycle characteristics and a slurry comprising the conductive material are provided. Moreover, according to this disclosure, a method for manufacturing a positive electrode forming coating liquid capable of easily manufacturing the aforementioned positive electrode forming coating liquid, and a method for manufacturing a positive electrode capable of easily manufacturing the aforementioned positive electrode are provided. Detailed Implementation

[0024] The preferred embodiments of this disclosure will now be described in detail. Additionally, in this specification, carbon black may be abbreviated as "CB" and carbon nanotubes as "CNT". Furthermore, in this specification, the tilde symbol "~" is used to indicate a range of values ​​before and after it. Specifically, "X~Y" (where X and Y are both numerical values) means "X or more and Y or less".

[0025] (Positive electrode composition) The cathode composition of this embodiment includes an active material, a binder material, and a conductive material. In this embodiment, the conductive material includes: carbon black (A) with an average primary particle size of 17 nm or more and 30 nm or less; a first carbon nanotube (B) with a peak ratio (D / G) of 0.3 or more and 1.4 or less in the Raman spectrum; and a second carbon nanotube (C) with a peak ratio (D / G) of less than 0.3 in the Raman spectrum.

[0026] The positive electrode composition of this embodiment can be a material constituting the flux layer in the positive electrode. By using a positive electrode having a flux layer composed of the positive electrode composition of this embodiment, a battery with excellent cycle characteristics can be achieved.

[0027] The reasons why the cathode composition of this embodiment is believed to achieve the above-mentioned effects are as follows.

[0028] The cathode composition of this embodiment combines carbon black with a spherical structure and carbon nanotubes with a fibrous structure. This combination is believed to improve the cathode composition's ability to follow the expansion and contraction of the cathode active material during battery charging and discharging. Furthermore, the cathode composition of this embodiment, as carbon nanotubes, contains two types of carbon nanotubes with different peak ratios (D / G). This further enhances the aforementioned following performance, making it easier to maintain the conductive network in the cathode even during repeated battery charging and discharging, thus achieving a battery with excellent cycle characteristics.

[0029] The components of the positive electrode composition of this embodiment will be described in detail below.

[0030] <Conductive Materials> The positive electrode composition of this embodiment includes carbon black (A) as a conductive material. The average primary particle size of the carbon black (A) is 17 nm or more and 30 nm or less.

[0031] When the average primary particle size of carbon black (A) is 17 nm or more, the conductive network formed in the positive electrode is more likely to develop. Furthermore, when the average primary particle size of carbon black (A) is 30 nm or less, the conductive network formed in the positive electrode is more likely to develop. From the viewpoint of obtaining this effect more significantly, the average primary particle size of carbon black (A) can be 27 nm or less, or even 25 nm or less. That is, the average primary particle size of carbon black (A) can be, for example, 17–30 nm, 17–27 nm, or 17–25 nm.

[0032] Furthermore, in this specification, the average primary particle size of carbon black (A) can be obtained by measuring the primary particle size of more than 100 carbon black particles randomly selected from a 50,000x magnified image of a transmission electron microscope (TEM) and calculating the average value. The primary particles of carbon black have a small aspect ratio and are nearly spherical in shape, but not perfectly spherical. Therefore, in this specification, the length of the longest line segment connecting two points on the outer periphery of a primary particle in the TEM image is taken as the primary particle size of the carbon black.

[0033] Carbon black (A) may be selected from the group consisting of acetylene black, furnace black and Ketjen black, preferably acetylene black.

[0034] The BET specific surface area of ​​carbon black (A) can be, for example, 100 m². 2 / g or above, or 110m 2 / g or more, 120m 2 / g or more or 130m 2 / g or more. Therefore, the conductive network formed in the positive electrode tends to be more developed. The BET specific surface area of ​​carbon black (A) can be, for example, 900 m². 2 Below / g, it can also be 890m 2 / g or less, 880m 2 / g or below or 870m 2 Below / g. Therefore, the conductive network formed in the positive electrode tends to be more developed. That is, the BET specific surface area of ​​carbon black (A) can be, for example, 100–900 m². 2 / g, 100~890m 2 / g, 100~880m 2 / g, 100~870m 2 / g, 110~900m 2 / g, 110~890m2 / g, 110~880m 2 / g, 110~870m 2 / g, 120~900m 2 / g, 120~890m 2 / g, 120~880m 2 / g, 120~870m 2 / g, 130~900m 2 / g, 130~890m 2 / g, 130~880m 2 / g or 130~870m 2 / g.

[0035] In addition, in this specification, the BET specific surface area of ​​carbon black (A) is a value determined by static volumetric method using nitrogen as adsorbate, in accordance with JIS Z8830.

[0036] Based on the total amount of conductive material, the carbon black (A) content can be, for example, 30% by mass or more. From the viewpoint of further improving cycle characteristics, it can also be 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more. Furthermore, based on the total amount of conductive material, the carbon black (A) content can be, for example, 90% by mass or less. From the viewpoint of further improving cycle characteristics, it can also be 85% by mass or less, 80% by mass or less, or 75% by mass or less. That is, based on the total amount of conductive material, the content of carbon black (A) can be, for example, 30-90% by mass, 30-85% by mass, 30-80% by mass, 30-75% by mass, 35-90% by mass, 35-85% by mass, 35-80% by mass, 35-75% by mass, 40-90% by mass, 40-85% by mass, 40-80% by mass, 40-75% by mass, 45-90% by mass, 45-85% by mass, 45-80% by mass, 45-75% by mass, 50-90% by mass, 50-85% by mass, 50-80% by mass, 50-75% by mass, 55-90% by mass, 55-85% by mass, 55-80% by mass, 55-75% by mass, 60-90% by mass, 60-85% by mass, 60-80% by mass, 60-75% by mass, 65-90% by mass, 65-85% by mass, 65-80% by mass, or 65-75% by mass.

[0037] The cathode composition of this embodiment further comprises a first carbon nanotube (B) as a conductive material. In the first carbon nanotube (B), the peak ratio (D / G) of the D band to the G band in the Raman spectrum is 0.3 or more and 1.4 or less.

[0038] In carbon nanotubes, the peak ratio (D / G) of the D band to the G band in the Raman spectrum can be used as an indicator of the crystallinity of carbon nanotubes. The peak ratio (D / G) of the first carbon nanotube (B) is 0.3 or higher, and from the viewpoint that a conductive network in the cathode is more easily developed, it can also be 0.4 or higher, 0.5 or higher, or 0.6 or higher. Furthermore, the peak ratio (D / G) of the first carbon nanotube (B) is 1.4 or lower, and from the viewpoint that a conductive network in the cathode is more easily developed, it can also be 1.3 or lower, 1.2 or lower, 1.1 or lower, 1.0 or lower, or 0.9 or lower. That is, the peak ratio (D / G) of the first carbon nanotube (B) can be, for example, 0.3–1.4, 0.3–1.3, 0.3–1.2, 0.3–1.1, 0.3–1.0, 0.3–0.9, 0.4–1.4, 0.4–1.3, 0.4–1.2, 0.4–1.1, 0.4–1.0, 0.4–0.9, 0.5–1.4, 0.5–1.3, 0.5–1.2, 0.5–1.1, 0.5–1.0, 0.5–0.9, 0.6–1.4, 0.6–1.3, 0.6–1.2, 0.6–1.1, 0.6–1.0, or 0.6–0.9.

[0039] Furthermore, in this specification, Raman spectroscopy was measured using a microlaser Raman system (manufactured by Thermo Fisher Scientific, product name "Nicolet Almega XR"). In the Raman spectrum of carbon nanotubes, a band known as the G-band (1600 cm⁻¹) was observed. -1 (nearby) and D zone (1350cm) -1 The vibrational modes (near the carbon nanotube) are as follows: the G-band originates from the hexagonal graphite lattice structure that makes up the cylindrical surface of the carbon nanotube, and the D-band originates from the amorphous region. A lower peak intensity ratio (D / G ratio) between the D and G bands indicates higher crystallinity of the carbon nanotube.

[0040] The average diameter of the first carbon nanotube (B) can be, for example, 2 nm or more, and from the viewpoint that it is easier to develop a conductive network in the positive electrode, it can also be 3 nm or more, 4 nm or more, or 5 nm or more. Furthermore, the average diameter of the first carbon nanotube (B) can be, for example, 15 nm or less, and from the viewpoint that it is easier to develop a conductive network in the positive electrode, it can also be 13 nm or less, 11 nm or less, or 10 nm or less. That is, the average diameter of the first carbon nanotube (B) can be, for example, 2–15 nm, 2–13 nm, 2–11 nm, 2–10 nm, 3–15 nm, 3–13 nm, 3–11 nm, 3–10 nm, 4–15 nm, 4–13 nm, 4–11 nm, 4–10 nm, 5–15 nm, 5–13 nm, 5–11 nm, or 5–10 nm.

[0041] Furthermore, in this specification, the average diameter of carbon nanotubes refers to the average diameter measured based on images of carbon nanotubes observed using a transmission electron microscope (TEM). Specifically, using a JEM-2000FX transmission electron microscope (manufactured by Nippon Electronics Corporation), 10 images of carbon nanotubes were taken at a magnification of 200,000x. For the obtained images, the diameter of 100 randomly selected carbon nanotubes was determined by image analysis and obtained by arithmetic mean.

[0042] The first carbon nanotube (B) can be a multilayer carbon nanotube (MWCNT). The multilayer carbon nanotube can be a carbon nanotube with a coaxial tubular stacked structure having three or more layers of graphene sheets.

[0043] Commercially available products can be used as the first carbon nanotube (B). Examples of first carbon nanotubes (B) include Flotube 6000 and Flotube 7000 (manufactured by Canano Technology Ltd, MWCNT).

[0044] Based on the total amount of conductive material, the content of the first carbon nanotube (B) can be, for example, 5% by mass or more, and from the viewpoint of further improving cycle characteristics, it can also be 10% by mass or more, 15% by mass or more, 18% by mass or more, 20% by mass or more, or 22% by mass or more. Furthermore, based on the total amount of conductive material, the content of the first carbon nanotube (B) can be, for example, 50% by mass or less, and from the viewpoint of further improving cycle characteristics, it can also be 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 28% by mass or less. That is, based on the total amount of conductive material, the content of the first carbon nanotube (B) can be, for example, 5-50% by mass, 5-45% by mass, 5-40% by mass, 5-35% by mass, 5-30% by mass, 5-28% by mass, 10-50% by mass, 10-45% by mass, 10-40% by mass, 10-35% by mass, 10-30% by mass, 10-28% by mass, 15-50% by mass, 15-45% by mass, 15-40% by mass, 15-35% by mass, 15-30% by mass. Mass%, 15-28% mass%, 18-50% mass%, 18-45% mass%, 18-40% mass%, 18-35% mass%, 18-30% mass%, 18-28% mass%, 20-50% mass%, 20-45% mass%, 20-40% mass%, 20-35% mass%, 20-30% mass%, 20-28% mass%, 22-50% mass%, 22-45% mass%, 22-40% mass%, 22-35% mass%, 22-30% mass or 22-28% mass.

[0045] The cathode composition of this embodiment further comprises a second carbon nanotube (C) as a conductive material. In the second carbon nanotube (C), the peak ratio (D / G) of the D band to the G band in the Raman spectrum is less than 0.3.

[0046] The peak ratio (D / G) of the second carbon nanotube (C) is less than 0.3, and from the viewpoint of further improving conductivity, it can also be less than 0.2 or less than 0.1. Furthermore, the peak ratio (D / G) of the second carbon nanotube (C) can be, for example, 0.01 or higher, and from the viewpoint of further improving conductivity, it can also be 0.02 or higher, 0.03 or higher, 0.04 or higher, or 0.05 or higher. That is, the peak ratio (D / G) of the second carbon nanotube (C) can be 0.02 or higher and less than 0.3, 0.02 or higher and less than 0.2, 0.02 or higher and less than 0.1, 0.03 or higher and less than 0.3, 0.03 or higher and less than 0.2, 0.03 or higher and less than 0.1, 0.04 or higher and less than 0.3, 0.04 or higher and less than 0.2, 0.04 or higher and less than 0.1, 0.05 or higher and less than 0.3, 0.05 or higher and less than 0.2, or 0.05 or higher and less than 0.1.

[0047] The average diameter of the second carbon nanotube (C) can be, for example, 0.5 nm or more, and from the viewpoint that it is easier to develop a conductive network in the positive electrode, it can also be 0.6 nm or more or 0.7 nm or more. In addition, the average diameter of the second carbon black (C) can be, for example, less than 2 nm, and from the viewpoint that it is easier to develop a conductive network in the positive electrode, it can also be 1.7 nm or less, 1.5 nm or less, 1.3 nm or less, 1.1 nm or less or 1.0 nm or less. That is, the average diameter of the second carbon nanotube (C) can be, for example, greater than or less than 2 nm, 0.5–1.7 nm, 0.5–1.5 nm, 0.5–1.3 nm, 0.5–1.1 nm, 0.5–1.0 nm, greater than or less than 2 nm, 0.6–1.7 nm, 0.6–1.5 nm, 0.6–1.3 nm, 0.6–1.1 nm, 0.6–1.0 nm, greater than or less than 2 nm, 0.7–1.7 nm, 0.7–1.5 nm, 0.7–1.3 nm, 0.7–1.1 nm, or 0.7–1.0 nm.

[0048] The second carbon nanotube (C) can be a single-layer carbon nanotube (SWCNT) or a double-layer carbon nanotube (DWCNT). A single-layer carbon nanotube can be a carbon nanotube with a tubular structure composed of graphene sheets, while a double-layer carbon nanotube can be a carbon nanotube with a coaxial tubular stacked structure of two layers of graphene sheets.

[0049] Commercially available products can be used as the second carbon nanotube (C). For example, Signis CG300 (manufactured by CHASM Corporation, SWCNT) can be used as the second carbon nanotube (C).

[0050] Based on the total amount of conductive material, the content of the second carbon nanotube (C) can be, for example, 1% by mass or more, and from the viewpoint of further improving cycle performance, it can also be 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 18% by mass or more, 20% by mass or more, or 22% by mass or more. Furthermore, based on the total amount of conductive material, the content of the first carbon nanotube (C) can be, for example, 45% by mass or less, and from the viewpoint of further improving cycle performance, it can also be 40% by mass or less, 35% by mass or less, 30% by mass or less, 28% by mass or less, or 25% by mass or less. That is, based on the total amount of conductive material, the content of the second carbon nanotube (C) can be, for example, 1–45% by mass, 1–40% by mass, 1–35% by mass, 1–30% by mass, 1–28% by mass, 1–25% by mass, 3–45% by mass, 3–40% by mass, 3–35% by mass, 3–30% by mass, 3–28% by mass, 3–25% by mass, 5–45% by mass, 5–40% by mass, 5–35% by mass, 5–30% by mass, 5–28% by mass, 5–25% by mass, 10–45% by mass, 10–40% by mass, 10–35% by mass, 10–30% by mass, 10–28% by mass, 10 ~25% by mass, 15-45% by mass, 15-40% by mass, 15-35% by mass, 15-30% by mass, 15-28% by mass, 15-25% by mass, 18-45% by mass, 18-40% by mass, 18-35% by mass, 18-30% by mass, 18-28% by mass, 18-25% by mass, 20-45% by mass, 20-40% by mass, 20-35% by mass, 20-30% by mass, 20-28% by mass, 20-25% by mass, 22-45% by mass, 22-40% by mass, 22-35% by mass, 22-30% by mass, 22-28% by mass or 22-25% by mass.

[0051] The cathode composition of this embodiment may further include other components (D) besides carbon black (A), first carbon nanotubes (B), and second carbon nanotubes (C) as conductive materials.

[0052] Examples of components (D) include graphene, graphite, porous carbon, etc.

[0053] Based on the total amount of conductive material, the content of component (D) can, for example, be less than 50% by mass. From the viewpoint of more significantly obtaining the aforementioned effects brought about by the combined use of carbon black (A), first carbon nanotubes (B), and second carbon nanotubes (C), it can also be 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or even 0% by mass. That is, based on the total amount of conductive material, the total content of carbon black (A), first carbon nanotubes (B), and second carbon nanotubes (C) can, for example, exceed 50% by mass. From the viewpoint of more significantly obtaining the aforementioned effects brought about by the combined use of carbon black (A), first carbon nanotubes (B), and second carbon nanotubes (C), it can also be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more, or even 100% by mass.

[0054] Based on the total amount of the positive electrode composition, the content of conductive material can be, for example, 0.05% by mass or more, and from the viewpoint that it is easier to develop a conductive network, it can also be 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more. Furthermore, based on the total amount of the positive electrode composition, the content of conductive material can be, for example, 10% by mass or less, and from the viewpoint that a conductive network can be sufficiently formed, it can also be 5% by mass or less, 3% by mass or less, or 1% by mass or less. That is, based on the total amount of the positive electrode composition, the content of conductive material can be, for example, 0.05–10% by mass, 0.05–5% by mass, 0.05–3% by mass, 0.05–1% by mass, 0.1–10% by mass, 0.1–5% by mass, 0.1–3% by mass, 0.1–1% by mass, 0.3–10% by mass, 0.3–5% by mass, 0.3–3% by mass, 0.3–1% by mass, 0.5–10% by mass, 0.5–5% by mass, 0.5–3% by mass, or 0.5–1% by mass.

[0055] <Active Substances> The positive electrode composition of this embodiment includes an active material. The active material can be any substance capable of reversibly adsorbing and releasing cations. The active material may also be referred to as the positive electrode active material.

[0056] There are no particular limitations on the active material; for example, known active materials used in lithium-ion secondary batteries can be used without special restrictions. Examples of active materials include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, and lithium iron phosphate.

[0057] The active material can be, for example, a material with a volume resistivity of 1×10⁻⁶. 4Lithium-containing composite oxides or lithium-containing polyanionic compounds containing manganese with an Ω·cm or higher. Examples of manganese-containing lithium-containing composite oxides include: LiMnO2, LiMnO3, LiMn2O3, and Li... 1+x Mn 2-x Lithium manganese oxides such as O4 (where x = 0 to 0.33); and those containing, for example, LiMn x Ni y Co z O2 (where x+y+z=1, 0≤y<1, 0≤z<1, 0≤x<1), Li 1+x Mn 2-x-y M y O4 (where x = 0–0.33, y = 0–1.0, 2-xy > 0), LiMn 2-x M x Composite oxides of one or more transition metal elements, such as O2 (where x = 0.01–0.1) and Li2Mn3MO8. Examples of lithium-containing polyanionic compounds include LiFePO4, LiMnPO4, and Li2MPO4F (where M is at least one metal selected from the group consisting of Co, Ni, Fe, Cr, and Zn). In each formula, M is at least one metal selected from the group consisting of Fe, Co, Ni, Al, Cu, Mg, Cr, Zn, and Ta.

[0058] From the perspective of achieving excellent adhesion to conductive and binding materials and readily obtaining batteries with superior cycle characteristics, the average particle size (D) of the active material is crucial. 50 The particle size can be less than 20 μm or less than 10 μm. The average particle size (D) of the active material... 50 The average particle size (D50) of the active material can be determined by laser light scattering. For example, the average particle size (D50) of the active material can be greater than 1 μm. 50 For example, it can be 1-20 μm or 1-10 μm.

[0059] Based on the total amount of the cathode composition, the content of active material can be, for example, 80% by mass or more, and from the viewpoint of further improving battery capacity, it can also be 85% by mass or more, 90% by mass or more, or 95% by mass or more. Furthermore, based on the total amount of the cathode composition, the content of active material can be, for example, 99.9% by mass or less, and from the viewpoint of being able to sufficiently obtain battery capacity and more easily and significantly obtain the aforementioned effects brought about by conductive materials, it can also be 99% by mass or less, 98% by mass or less, or 97% by mass or less. That is, based on the total amount of the positive electrode composition, the content of active material can be, for example, 80-99.9% by mass, 80-99% by mass, 80-98% by mass, 80-97% by mass, 85-99.9% by mass, 85-99% by mass, 85-98% by mass, 85-97% by mass, 90-99.9% by mass, 90-99% by mass, 90-98% by mass, 90-97% by mass, 95-99.9% by mass, 95-99% by mass, 95-98% by mass, or 95-97% by mass.

[0060] <Adhesive Materials> Any adhesive material can be used to bond active materials and conductive materials and maintain the shape of the adhesive layer.

[0061] Examples of adhesive materials include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene copolymers, and (meth)acrylate copolymers. The structure of the adhesive polymer can be, for example, a random copolymer, an alternating copolymer, a graft copolymer, or a block copolymer. From the viewpoint of excellent voltage resistance, PVDF is preferred as an adhesive material.

[0062] Based on the total amount of the cathode composition, the content of the binder material can be, for example, 0.5% by mass or more, and from the viewpoint of better adhesion, it can also be 1% by mass or more, 1.5% by mass or more, or 2% by mass or more. Furthermore, based on the total amount of the cathode composition, the content of the binder material can be, for example, 10% by mass or less, and from the viewpoint of further improving battery capacity, it can also be 8% by mass or less, 6% by mass or less, or 4% by mass or less. That is, based on the total amount of the cathode composition, the content of the binder material can be, for example, 0.5–10% by mass, 0.5–8% by mass, 0.5–6% by mass, 0.5–4% by mass, 1–10% by mass, 1–8% by mass, 1–6% by mass, 1–4% by mass, 1.5–10% by mass, 1.5–8% by mass, 1.5–6% by mass, 1.5–4% by mass, 2–10% by mass, 2–8% by mass, 2–6% by mass, or 2–4% by mass.

[0063] The positive electrode composition of this embodiment may further include a dispersant other than the active material, binder, and conductive material.

[0064] <Dispersant> A dispersant is a component that assists in the dispersion of conductive materials in a dispersion medium. When a slurry formed by dispersing conductive materials in a dispersion medium is used to manufacture a positive electrode composition, the positive electrode composition may contain a dispersant.

[0065] Examples of dispersants include high molecular weight dispersants and low molecular weight dispersants. From the viewpoint of long-term dispersion stability of conductive materials, high molecular weight dispersants are preferred. Dispersants can be selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, carboxymethyl cellulose and its salts, polyvinyl acetal, polyvinyl acetate, polyvinylamine, and polyvinyl formal.

[0066] The content of the dispersant relative to 100 parts by mass of the conductive material can be, for example, 100 parts by mass or less. From the viewpoint of suppressing the decrease in conductivity caused by the dispersant, it can also be 80 parts by mass or less, 60 parts by mass or less, or 40 parts by mass or less. When the cathode composition of this embodiment contains a dispersant, the content of the dispersant relative to 100 parts by mass of the conductive material can be, for example, 5 parts by mass or more. From the viewpoint of further improving the dispersibility of the conductive material, it can also be 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more. That is, the content of the dispersant relative to 100 parts by mass of conductive material can be, for example, 5-100 parts by mass, 5-80 parts by mass, 5-60 parts by mass, 5-40 parts by mass, 10-100 parts by mass, 10-80 parts by mass, 10-60 parts by mass, 10-40 parts by mass, 15-100 parts by mass, 15-80 parts by mass, 15-60 parts by mass, 15-40 parts by mass, 20-100 parts by mass, 20-80 parts by mass, 20-60 parts by mass, or 20-40 parts by mass.

[0067] Based on the total amount of the positive electrode composition, the content of the dispersant can be, for example, 10% by mass or less. From the viewpoint of suppressing the decrease in conductivity caused by the dispersant, it can also be 5% by mass or less, 3% by mass or less, or 1% by mass or less. When the positive electrode composition of this embodiment contains a dispersant, based on the total amount of the positive electrode composition, the content of the dispersant can be, for example, 0.05% by mass or more. From the viewpoint of further improving the dispersibility of the conductive material, it can also be 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more. That is, the content of the dispersant is based on the total amount of the positive electrode composition, and can be, for example, 0.05-10% by mass, 0.05-5% by mass, 0.05-3% by mass, 0.05-1% by mass, 0.1-10% by mass, 0.1-5% by mass, 0.1-3% by mass, 0.1-1% by mass, 0.3-10% by mass, 0.3-5% by mass, 0.3-3% by mass, 0.3-1% by mass, 0.5-10% by mass, 0.5-5% by mass, 0.5-3% by mass, or 0.5-1% by mass.

[0068] The positive electrode composition of this embodiment may further include other components besides active materials, binders, conductive materials, and dispersants.

[0069] Other components include, for example, wetting agents and defoaming agents.

[0070] Based on the total amount of the cathode composition, the content of other components can be, for example, less than 5% by mass, less than 3% by mass, less than 2% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.3% by mass, less than 0.2% by mass, or less than 0.1% by mass, or even 0% by mass. That is, based on the total amount of the cathode composition, the total content of active material, binder material, and conductive material (or the total content of active material, binder material, conductive material, and dispersant) can be, for example, more than 95% by mass, more than 97% by mass, more than 98% by mass, more than 99% by mass, more than 99.5% by mass, or more than 99.9% by mass, or even 100% by mass.

[0071] The positive electrode composition of this embodiment can be a material constituting the additive layer in the positive electrode. That is, the positive electrode composition of this embodiment can be formed into a layered structure.

[0072] The positive electrode composition of this embodiment can be formed, for example, by coating with the positive electrode forming solution described later and then drying.

[0073] (Coating solution for positive electrode formation) The positive electrode forming coating solution of this embodiment includes an active substance, a binder, a conductive material, and a dispersion medium. Furthermore, the positive electrode forming coating solution of this embodiment may further include a dispersant.

[0074] The active material, binder, conductive material, and dispersant in the positive electrode forming coating solution of this embodiment can be the same as those in the positive electrode composition described above. That is, the positive electrode forming coating solution of this embodiment can also be described as a coating solution containing the above-described positive electrode composition and dispersion medium.

[0075] The contents of the active material, binder, conductive material and dispersant in the positive electrode forming coating liquid of this embodiment (based on the total amount of solid components in the positive electrode forming coating liquid) can be the same as the contents of the active material, binder, conductive material and dispersant in the above-mentioned positive electrode composition (based on the total amount of the positive electrode composition).

[0076] The dispersion medium can be any medium capable of dispersing the components in the coating liquid. Examples of dispersion media include water, N-methyl-2-pyrrolidone, cyclohexane, methyl ethyl ketone, and methyl isobutyl ketone. Among these, N-methyl-2-pyrrolidone is preferred from the viewpoint of excellent dispersibility.

[0077] There is no particular limitation on the content of the dispersion medium, as long as it is sufficient to achieve the coatability of the coating solution for positive electrode formation. Based on the total amount of the coating solution for positive electrode formation, the content of the dispersion medium can be, for example, 10% by mass or more, or 20% by mass or more, 30% by mass or more, or 40% by mass or more. Furthermore, based on the total amount of the coating solution for positive electrode formation, the content of the dispersion medium can be, for example, 90% by mass or less, or 80% by mass or less, 70% by mass or less, or 60% by mass or less. That is, based on the total amount of the coating liquid for forming the positive electrode, the content of the dispersion medium can be, for example, 10-90% by mass, 10-80% by mass, 10-70% by mass, 10-60% by mass, 20-90% by mass, 20-80% by mass, 20-70% by mass, 20-60% by mass, 30-90% by mass, 30-80% by mass, 30-70% by mass, 30-60% by mass, 40-90% by mass, 40-80% by mass, 40-70% by mass, or 40-60% by mass.

[0078] The positive electrode forming coating solution of this embodiment can form an additive layer composed of the above-described positive electrode composition by coating and drying. Here, drying refers to the operation of removing at least a portion of the dispersion medium from the coating film obtained by coating the positive electrode forming coating solution.

[0079] The method for applying the positive electrode forming coating liquid in this embodiment is not particularly limited, and can be appropriately selected from known coating methods (coating means, coating apparatus). Examples of coating methods include: mold coating, dip coating, roller coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic coating.

[0080] There are no particular limitations on the drying method for the coating; any known drying method (drying means, drying apparatus) can be appropriately selected. Examples of drying methods include methods that vaporize at least a portion of the dispersed medium by heating and / or reducing pressure. Drying methods may include static drying, heating drying, reduced pressure drying, or drying methods using dryers such as forced-air dryers, hot-air dryers, infrared heaters, and far-infrared heaters.

[0081] In this embodiment, the coating solution for forming the positive electrode can be applied to the current collector and then dried. This forms an agent layer composed of the positive electrode composition on the current collector, resulting in a positive electrode comprising the current collector and the agent layer.

[0082] The positive electrode forming coating solution of this embodiment can be obtained by dispersing each component of the above-described positive electrode composition in a dispersion medium. The positive electrode forming coating solution of this embodiment can be manufactured, for example, by the following manufacturing method.

[0083] <Method for manufacturing coating solution for positive electrode formation> The method for manufacturing a coating liquid for forming a positive electrode may include a mixing step of mixing each component in the above-mentioned positive electrode composition with a dispersion medium.

[0084] The mixing process can be a process in which each component is dispersed in a dispersion medium at once, or it can be a process in which each component is dispersed in a dispersion medium separately and then mixed.

[0085] The mixing process can be, for example, mixing an active substance, a binder solution containing a binder, a slurry (A) containing carbon black (A), a slurry (B) containing a first carbon nanotube (B), and a slurry (C) containing a second carbon nanotube (C). Through such a mixing process, a coating solution with uniformly dispersed components can be easily obtained, and damage to the conductive material caused by stirring during mixing can be suppressed.

[0086] The binder solution contains a binder and a dispersion medium. The dispersion medium in the binder solution can be appropriately selected from the dispersion media mentioned above. The dispersion medium in the binder solution can be the same as the dispersion medium in slurry (A), slurry (B), and slurry (C).

[0087] The content of the dispersion medium in the binder solution is not particularly limited, as long as it is sufficient to fully dissolve the binder. Based on the total amount of the binder solution, the content of the dispersion medium in the binder solution can be, for example, 60% by mass or more, or 70% by mass or more, 80% by mass or more, or 90% by mass or more. Furthermore, based on the total amount of the binder solution, the content of the dispersion medium in the binder solution can be, for example, 99.9% by mass or less, or 99% by mass or less, 98% by mass or less, or 97% by mass or less. That is, based on the total amount of the binder solution, the content of the dispersion medium in the binder solution can be, for example, 60–99.9% by mass, 60–99% by mass, 60–98% by mass, 60–97% by mass, 70–99.9% by mass, 70–99% by mass, 70–98% by mass, 70–97% by mass, 80–99.9% by mass, 80–99% by mass, 80–98% by mass, 80–97% by mass, 90–99.9% by mass, 90–99% by mass, 90–98% by mass, or 90–97% by mass.

[0088] Slurry (A) contains carbon black (A) and a dispersion medium. Slurry (A) may further contain a dispersant. The dispersion medium in slurry (A) may be appropriately selected from the above-mentioned dispersion media. The dispersion medium of slurry (A) may be the same as the dispersion medium in the binder solution, slurry (B), and slurry (C).

[0089] The content of the dispersion medium in the slurry (A) is not particularly limited, as long as it is sufficient to fully disperse the carbon black (A). Based on the total amount of slurry (A), the content of the dispersion medium in slurry (A) can be, for example, 60% by mass or more, or 70% by mass or more, 80% by mass or more, or 90% by mass or more. Furthermore, based on the total amount of slurry (A), the content of the dispersion medium in slurry (A) can be, for example, 99.9% by mass or less, or 99% by mass or less, 98% by mass or less, or 97% by mass or less. That is, based on the total amount of slurry (A), the content of the dispersion medium in slurry (A) can be, for example, 60-99.9% by mass, 60-99% by mass, 60-98% by mass, 60-97% by mass, 70-99.9% by mass, 70-99% by mass, 70-98% by mass, 70-97% by mass, 80-99.9% by mass, 80-99% by mass, 80-98% by mass, 80-97% by mass, 90-99.9% by mass, 90-99% by mass, 90-98% by mass, or 90-97% by mass.

[0090] When the slurry (A) contains a dispersant, the content of the dispersant relative to 100 parts by mass of carbon black (A) can be, for example, 5 parts by mass or more, or 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more. Furthermore, the content of the dispersant relative to 100 parts by mass of carbon black (A) can be, for example, less than 100 parts by mass, or less than 90 parts by mass, less than 80 parts by mass, or less than 70 parts by mass. That is, when the slurry (A) contains a dispersant, the content of the dispersant relative to 100 parts by mass of carbon black (A) can be, for example, 5 to 100 parts by mass, 5 to 90 parts by mass, 5 to 80 parts by mass, 5 to 70 parts by mass, 10 to 100 parts by mass, 10 to 90 parts by mass, 10 to 80 parts by mass, 10 to 70 parts by mass, 15 to 100 parts by mass, 15 to 90 parts by mass, 15 to 80 parts by mass, 15 to 70 parts by mass, 20 to 100 parts by mass, 20 to 90 parts by mass, 20 to 80 parts by mass, or 20 to 70 parts by mass.

[0091] Slurry (B) contains first carbon nanotubes (B) and a dispersion medium. Slurry (B) may further contain a dispersant. The dispersion medium in slurry (B) may be appropriately selected from the above-mentioned dispersion media. The dispersion medium of slurry (B) may be the same as the dispersion medium in the binder solution, slurry (A), and slurry (C).

[0092] The content of the dispersion medium in the slurry (B) is not particularly limited, as long as it is sufficient to fully disperse the first carbon nanotubes (B). Based on the total amount of slurry (B), the content of the dispersion medium in the slurry (B) can be, for example, 60% by mass or more, or 70% by mass or more, 80% by mass or more, or 90% by mass or more. Furthermore, based on the total amount of slurry (B), the content of the dispersion medium in the slurry (B) can be, for example, 99.9% by mass or less, or 99% by mass or less, 98% by mass or less, or 97% by mass or less. That is, based on the total amount of slurry (B), the content of the dispersion medium in slurry (B) can be, for example, 60-99.9% by mass, 60-99% by mass, 60-98% by mass, 60-97% by mass, 70-99.9% by mass, 70-99% by mass, 70-98% by mass, 70-97% by mass, 80-99.9% by mass, 80-99% by mass, 80-98% by mass, 80-97% by mass, 90-99.9% by mass, 90-99% by mass, 90-98% by mass, or 90-97% by mass.

[0093] When the slurry (B) contains a dispersant, the content of the dispersant relative to 100 parts by mass of the first carbon nanotubes (B) can be, for example, 5 parts by mass or more, or 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more. Furthermore, the content of the dispersant relative to 100 parts by mass of the first carbon nanotubes (B) can be, for example, less than 100 parts by mass, or less than 90 parts by mass, less than 80 parts by mass, or less than 70 parts by mass. That is, when the slurry (B) contains a dispersant, the content of the dispersant relative to 100 parts by mass of the first carbon nanotube (B) can be, for example, 5-100 parts by mass, 5-90 parts by mass, 5-80 parts by mass, 5-70 parts by mass, 10-100 parts by mass, 10-90 parts by mass, 10-80 parts by mass, 10-70 parts by mass, 15-100 parts by mass, 15-90 parts by mass, 15-80 parts by mass, 15-70 parts by mass, 20-100 parts by mass, 20-90 parts by mass, 20-80 parts by mass, or 20-70 parts by mass.

[0094] The slurry (C) contains second carbon nanotubes (C) and a dispersion medium. The slurry (C) may further contain a dispersant. The dispersion medium in the slurry (C) may be appropriately selected from the above-mentioned dispersion media. The dispersion medium of the slurry (C) may be the same as the dispersion medium in the binder solution, slurry (A), and slurry (B).

[0095] The content of the dispersion medium in the slurry (C) is not particularly limited, as long as it is sufficient to fully disperse the second carbon nanotubes (C). Based on the total amount of slurry (C), the content of the dispersion medium in the slurry (C) can be, for example, 60% by mass or more, or 70% by mass or more, 80% by mass or more, or 90% by mass or more. Furthermore, based on the total amount of slurry (C), the content of the dispersion medium in the slurry (C) can be, for example, 99.9% by mass or less, or 99% by mass or less, 98% by mass or less, or 97% by mass or less. That is, based on the total amount of slurry (C), the content of the dispersion medium in slurry (C) can be, for example, 60-99.9% by mass, 60-99% by mass, 60-98% by mass, 60-97% by mass, 70-99.9% by mass, 70-99% by mass, 70-98% by mass, 70-97% by mass, 80-99.9% by mass, 80-99% by mass, 80-98% by mass, 80-97% by mass, 90-99.9% by mass, 90-99% by mass, 90-98% by mass, or 90-97% by mass.

[0096] When the slurry (C) contains a dispersant, the content of the dispersant relative to 100 parts by mass of the second carbon nanotubes (C) can be, for example, 5 parts by mass or more, or 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more. Furthermore, the content of the dispersant relative to 100 parts by mass of the second carbon nanotubes (C) can be, for example, less than 100 parts by mass, or less than 90 parts by mass, less than 80 parts by mass, or less than 70 parts by mass. That is, when the slurry (C) contains a dispersant, the content of the dispersant relative to 100 parts by mass of the second carbon nanotubes (C) can be, for example, 5-100 parts by mass, 5-90 parts by mass, 5-80 parts by mass, 5-70 parts by mass, 10-100 parts by mass, 10-90 parts by mass, 10-80 parts by mass, 10-70 parts by mass, 15-100 parts by mass, 15-90 parts by mass, 15-80 parts by mass, 15-70 parts by mass, 20-100 parts by mass, 20-90 parts by mass, 20-80 parts by mass, or 20-70 parts by mass.

[0097] There are no particular limitations on the mixing method in the mixing process; appropriate methods (mixing means, mixing devices) can be selected from those that are known.

[0098] (positive electrode) The positive electrode of this embodiment comprises the above-described positive electrode composition. For example, the positive electrode of this embodiment may comprise an additive layer made of the positive electrode composition and a current collector. The additive layer may be disposed (layered) on the current collector.

[0099] There are no particular limitations on the current collector; any known current collector can be used without restriction. Examples of current collectors include metal foil (metals such as gold, silver, copper, platinum, aluminum, iron, nickel, chromium, manganese, lead, tungsten, titanium, and alloys with any of these metals as the main component). Current collectors are usually provided in foil form, but are not limited to this; perforated foil and mesh current collectors can also be used.

[0100] The compound layer may be a compound layer containing the above-mentioned positive electrode composition, or it may be a compound layer composed of the above-mentioned positive electrode composition.

[0101] The thickness of the compound layer can be, for example, 20 μm or more, and from the viewpoint of further improving conductivity, it can also be 30 μm or more, 40 μm or more, or 50 μm or more. Furthermore, the thickness of the compound layer can be, for example, 100 μm or less, and from the viewpoint of further improving conductivity, it can also be 90 μm or less, 80 μm or less, or 70 μm or less. That is, the thickness of the compound layer can be, for example, 20–100 μm, 20–90 μm, 20–80 μm, 20–70 μm, 30–100 μm, 30–90 μm, 30–80 μm, 30–70 μm, 40–100 μm, 40–90 μm, 40–80 μm, 40–70 μm, 50–100 μm, 50–90 μm, 50–80 μm, or 50–70 μm.

[0102] The positive electrode of this embodiment can be manufactured, for example, by a manufacturing method (positive electrode manufacturing method) including a mixture layer forming step, which is a step of applying the above-mentioned positive electrode forming coating liquid onto the current collector and forming a mixture layer on the current collector by drying.

[0103] The manufacturing method of the positive electrode may further include a pressing step of pressing the flux layer formed by the flux layer formation process and the current collector in the lamination direction. The pressing method in the pressing step is not particularly limited, and can be, for example, rolling, die pressing, calendering, etc.

[0104] The manufacturing method of the positive electrode may further include a drying process to remove moisture from the compound layer after the pressurization process. In the drying process, residual moisture in the compound layer may be removed, for example, by vacuum drying.

[0105] The positive electrode of this embodiment can be suitably used as the positive electrode of a battery, especially a secondary battery (e.g., a lithium-ion secondary battery).

[0106] (Battery) The battery of this embodiment has the aforementioned positive electrode. The battery of this embodiment can be a secondary battery or a lithium-ion secondary battery. Because the battery of this embodiment has the aforementioned positive electrode, it tends to have excellent cycle characteristics.

[0107] In the battery of this embodiment, the components other than the positive electrode can be the same as those of a known battery. The method for manufacturing the battery of this embodiment is not particularly limited; except for using the aforementioned positive electrode, it can be manufactured using the same method as that used for manufacturing known batteries.

[0108] The battery of this embodiment may include, for example, the positive electrode, negative electrode, and separator described above.

[0109] The separator is not particularly limited; for example, separators known as separators for lithium-ion secondary batteries can be used without particular restriction. Examples of separators include synthetic resins such as polyethylene and polypropylene. A porous membrane is preferred because it has good electrolyte retention properties.

[0110] There are no particular limitations on the negative electrode; for example, a negative electrode known as a negative electrode for lithium-ion secondary batteries can be used without any particular restrictions. The negative electrode may, for example, include a negative electrode compound layer comprising a negative electrode active material and a binder material, and a negative electrode current collector.

[0111] The battery of this embodiment may, for example, have an electrode assembly formed by stacking or winding a positive electrode and a negative electrode with a separator in between.

[0112] In the battery of this embodiment, for example, the positive electrode, negative electrode, and separator can be immersed in the electrolyte.

[0113] The electrolyte is not particularly limited; for example, it can be a non-aqueous electrolyte containing lithium salts. Examples of non-aqueous solvents containing lithium salts include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. Furthermore, examples of lithium salts soluble in non-aqueous solvents include lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium trifluoromethanesulfonate. Additionally, the battery of this embodiment can also be a battery using an ion-conducting polymer or the like as the electrolyte.

[0114] The application of the battery in this embodiment is not particularly limited. For example, it can be used in a wide range of fields such as portable AV devices such as digital cameras, camcorders, portable audio players, and portable LCD TVs; portable information terminals such as laptops, smartphones, and mobile PCs; as well as other portable gaming devices, power tools, electric bicycles, hybrid vehicles, electric vehicles, and power storage systems.

[0115] The preferred embodiments of this disclosure have been described above, but this disclosure is not limited to the above embodiments.

[0116] (Conductive materials, pastes) For example, one aspect of this disclosure relates to a conductive material comprising carbon black (A), a first carbon nanotube (B), and a second carbon nanotube (C). Furthermore, another aspect of this disclosure relates to a slurry comprising the conductive material and a dispersion medium. Based on such a conductive material and slurry, the aforementioned positive electrode composition can be readily obtained.

[0117] As a dispersion medium in the slurry, the same dispersion medium as that in the above-mentioned coating liquid for forming the positive electrode can be listed.

[0118] The content of the dispersion medium in the slurry is not particularly limited, as long as it is sufficient to fully disperse the conductive material. Based on the total amount of the slurry, the content of the dispersion medium in the slurry can be, for example, 60% by mass or more, or 70% by mass or more, 80% by mass or more, or 90% by mass or more. Furthermore, based on the total amount of the slurry (C), the content of the dispersion medium in the slurry can be, for example, 99.9% by mass or less, or 99% by mass or less, 98% by mass or less, or 97% by mass or less. That is, based on the total amount of slurry, the content of the dispersion medium in the slurry can be, for example, 60–99.9% by mass, 60–99% by mass, 60–98% by mass, 60–97% by mass, 70–99.9% by mass, 70–99% by mass, 70–98% by mass, 70–97% by mass, 80–99.9% by mass, 80–99% by mass, 80–98% by mass, 80–97% by mass, 90–99.9% by mass, 90–99% by mass, 90–98% by mass, or 90–97% by mass.

[0119] The slurry may further contain a dispersant. When the slurry contains a dispersant, the content of the dispersant relative to 100 parts by mass of the conductive material may, for example, be 5 parts by mass or more, or 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more. Furthermore, the content of the dispersant relative to 100 parts by mass of the conductive material may, for example, be less than 100 parts by mass, or less than 90 parts by mass, less than 80 parts by mass, or less than 70 parts by mass. That is, when the slurry contains a dispersant, the content of the dispersant relative to 100 parts by mass of conductive material can be, for example, 5-100 parts by mass, 5-90 parts by mass, 5-80 parts by mass, 5-70 parts by mass, 10-100 parts by mass, 10-90 parts by mass, 10-80 parts by mass, 10-70 parts by mass, 15-100 parts by mass, 15-90 parts by mass, 15-80 parts by mass, 15-70 parts by mass, 20-100 parts by mass, 20-90 parts by mass, 20-80 parts by mass, or 20-70 parts by mass.

[0120] The slurry may further contain other components besides conductive materials and dispersants. Examples of such other components include wetting agents and defoaming agents.

[0121] Conductive materials and pastes can be used, for example, in the manufacture of the aforementioned coating solution for forming the positive electrode. Furthermore, conductive materials and pastes can also be used in coating solutions for forming the negative electrode, coating solutions for carbon-coated current collectors, and other applications.

[0122]

Example

[0123] (Preparation of carbon black) Prepare carbon blacks (A-1) to (A-3) and (X-1) to (X-3) as shown in Table 1. In the table, AB refers to acetylene black, FB refers to furnace black, and KB refers to Ketjen black.

[0124] Table 1 (Preparation of carbon nanotubes) Carbon nanotubes (B-1), (B-2), (Y-1), and (Y-2) as shown in Table 2 were prepared. Additionally, carbon nanotube (C-1) as shown in Table 3 was prepared. Furthermore, in the tables, MWCNT refers to multilayer carbon nanotubes, and SWCNT refers to single-layer carbon nanotubes.

[0125] Table 2 Table 3 (Preparation of carbon black slurry) N-methyl-2-pyrrolidone (hereinafter referred to as NMP) was prepared as the dispersion medium, and polyvinyl alcohol (manufactured by Denka, Poval B05) was prepared as the dispersant. 1.0% by mass of polyvinyl alcohol and 10.0% by mass of carbon black (any one of carbon blacks (A-1) to (A-3) and (X-1) to (X-3) in Table 1) were added to 89.0% by mass of NMP, and the mixture was stirred for 120 minutes using a planetary mixer (manufactured by PRIMIX, HIVIS DISPER-MIX 3D-5 model) to obtain a slurry. The obtained slurry was then fed into a bead mill (manufactured by Ashizawa Finetech, Mogen flow MGF2-ZA) containing zirconia beads (0.5 mm in diameter) for dispersion treatment. After dispersion treatment, the zirconia beads were removed by filtration to obtain a carbon black slurry.

[0126] (Preparation of carbon nanotube slurry) N-methyl-2-pyrrolidone (hereinafter referred to as NMP) was prepared as the dispersion medium, and polyvinyl alcohol (manufactured by Denka, Poval B05) was prepared as the dispersant. 0.4% by mass of polyvinyl alcohol and 0.4% by mass of carbon nanotubes (any one of carbon nanotubes (B-1), (B-2), (Y-1), and (Y-2) in Table 2 and carbon nanotubes (C-1) in Table 3) were added to 99.2% by mass of NMP, and the mixture was stirred for 120 minutes using a planetary mixer (manufactured by PRIMIX, HIVIS DISPER-MIX 3D-5) to obtain a slurry. The obtained slurry was then fed into a bead mill (manufactured by Ashizawa Finetech, Mogenflow MGF2-ZA) containing zirconia beads (0.5 mm in diameter) for dispersion treatment. After dispersion, the zirconia beads were removed by filtration to obtain a carbon nanotube slurry.

[0127] <Example 1-1> (1) Preparation of coating solution for positive electrode formation Slurries containing carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) were prepared using the above method. Additionally, slurries with an average particle size D were prepared. 50 10μm lithium nickel manganese cobalt oxide (manufactured by Beijing DangSheng Co., Ltd., "ME6E") was used as the active material, polyvinylidene fluoride NMP solution (manufactured by Solvey Co., Ltd., "Solef5130") was used as the binder, and NMP was used as the dispersion medium. The amounts of each raw material were adjusted so that, based on the solids ratio, the active material was 97.55% by mass, the conductive material was 1.0% by mass (carbon black (A-1) was 0.7% by mass, carbon nanotubes (B-1) was 0.25% by mass, and carbon nanotubes (C-1) was 0.05% by mass), the binder was 1.3% by mass, and the dispersant was 0.15% by mass. NMP was added until a coatable viscosity was reached, and the mixture was mixed uniformly using a rotary mixer (manufactured by THINKY Co., Ltd., AWATORI Rentaro ARV-310) to obtain the coating solution for positive electrode formation.

[0128] (2) Manufacturing of the positive electrode The positive electrode forming solution prepared in (1) above was applied to one side of a 15 μm thick aluminum foil (manufactured by UACJ Corporation) using an applicator to form a laminate. The laminate was then placed in a dryer and pre-dried at 105°C for 1 hour to completely remove NMP. Next, the dried laminate was pressed using a roller press at a linear pressure of 200 kg / cm to achieve an overall thickness of 80 μm. Then, it was vacuum dried at 170°C for 3 hours to completely remove residual moisture, thus obtaining a positive electrode with a current collector and an additive layer.

[0129] (3) Manufacturing of the negative electrode Pure water (manufactured by Kanto Chemical Co., Ltd.) was prepared as a solvent, artificial graphite (manufactured by Hitachi Chemical Co., Ltd., "MAG-D") as the negative electrode active material, styrene-butadiene rubber (manufactured by Zeon Corporation, Japan, "BM-400B", hereinafter referred to as SBR) as a binder, and carboxymethyl cellulose (manufactured by Daicel, Ltd., "D2200", hereinafter referred to as CMC) as a dispersant. Next, CMC was weighed to a solid content of 1% by mass, and artificial graphite was weighed to a solid content of 97% by mass, and mixed. Pure water was added to the mixture, and it was mixed until homogeneous using a rotary mixer (manufactured by THINKY Co., Ltd., AWATORI Rentaro ARV-310), to obtain a mixture. Then, SBR was weighed to a solid content of 2% by mass and added to the obtained mixture, and it was mixed until homogeneous using a rotary mixer (manufactured by THINKY Co., Ltd., AWATORI Rentaro ARV-310), to obtain a coating solution for negative electrode formation. Next, a coating solution for forming the negative electrode was applied to a 10 μm thick copper foil (manufactured by UACJ Corporation) using a coating applicator to create a laminate. This laminate was then placed in a dryer and pre-dried at 60°C for 1 hour. Next, it was pressed using a roller press at a linear pressure of 50 kg / cm to achieve an overall thickness of 60 μm. Finally, it was vacuum-dried at 120°C for 3 hours to completely remove residual moisture, yielding a negative electrode with a current collector and an additive layer.

[0130] (4) Battery manufacturing In a dry chamber where the dew point is controlled below -50°C, the positive electrode is processed into a size of 40×40mm and the negative electrode into a size of 44×44mm. Aluminum tabs are then welded onto the positive electrode, and nickel tabs are welded onto the negative electrode. The coating surfaces of the positive and negative electrodes are aligned centrally, and a 45×45mm polyolefin microporous membrane is placed between them. Next, a sheet-like outer casing cut / processed to a size of 70×140mm is folded in half along its long side. The outer casing is then positioned so that the aluminum tabs for the positive electrode and the nickel tabs for the negative electrode are exposed outside the casing, and the folded outer casing clamps the laminate of the positive electrode / polyolefin microporous membrane / negative electrode. Next, using a heat sealer, two sides of the outer casing, including the exposed edges of the aluminum tab for the positive electrode and the nickel tab for the negative electrode, are heated and welded together. Then, 2g of electrolyte (manufactured by Kishida Chemical, containing ethylene carbonate / diethyl carbonate = 1 / 2 (volume ratio) and 1M LiPF6 solution) is injected into the side that has not been heated and welded together. After the positive electrode, negative electrode, and polyolefin microporous membrane are fully impregnated with the electrolyte, the remaining side of the outer casing is heated and welded together using a vacuum heat sealer while the internal pressure is reduced, thus obtaining a lithium-ion secondary battery.

[0131] (5) Battery evaluation (5-1) Evaluation of internal resistance The fabricated battery was charged at 25°C with a constant current and constant voltage of 4.3V and a 0.2C limit, followed by a constant current discharge at 0.2C to 3.0V. Then, under the same conditions, it underwent 5 cycles of charge-discharge, and was charged to 50% depth of charge. Subsequently, impedance measurements were performed within a frequency range of 1.5MHz to 0.01Hz and a vibration voltage of 5mV to determine the internal resistance. The results are shown in Table 4.

[0132] (5-2) Evaluation of Cyclic Characteristics The fabricated battery was charged at 25°C with a constant current and constant voltage of 4.3V and a 1C limit, and then discharged at a constant current of 1C to 3.0V. This charge-discharge cycle was repeated 500 times, and the discharge capacity of each cycle was measured. As an indicator of the battery's cycle characteristics, the ratio of the capacity retention after 500 cycles to the capacity retention after one cycle was calculated as the cycle capacity retention rate. The results are shown in Table 4.

[0133] <Examples 1-2> Except for changing the content ratio of carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) from 70:25:5 to 65:20:15, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 4.

[0134] <Examples 1-3> Except for changing the content ratio of carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) from 70:25:5 to 40:30:30, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 4.

[0135] <Examples 1-4> Except for changing the content ratio of carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) from 70:25:5 to 80:17:3, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 4.

[0136] <Comparative Example 1-1> Except for using only carbon black (A-1) as the conductive material, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 5.

[0137] <Comparative Examples 1-2> Except for using only carbon nanotubes (B-1) as the conductive material, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 5.

[0138] <Comparative Examples 1-3> Except for omitting carbon nanotubes (C-1) and changing the content ratio of carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) from 70:25:5 to 70:30:0, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 5.

[0139] <Comparative Examples 1-4> Except for omitting carbon nanotubes (B-1) and changing the content ratio of carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) from 70:25:5 to 70:0:30, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 5.

[0140] <Comparative Examples 1-5> Except for omitting carbon black (A-1) and changing the content ratio of carbon black (A-1), carbon nanotubes (B-1), and carbon nanotubes (C-1) from 70:25:5 to 0:95:5, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 5.

[0141] Table 4 Table 5 <Example 2-1> Except for replacing carbon black (A-1) with carbon black (A-2), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 6.

[0142] <Example 2-2> Except for replacing carbon black (A-1) with carbon black (A-3) and setting the content ratio of carbon black (A-3), carbon nanotubes (B-1), and carbon nanotubes (C-1) to 45:30:25, the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 6.

[0143] <Comparative Example 2-1> Except for replacing carbon black (A-1) with carbon black (X-1), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 7.

[0144] <Comparative Example 2-2> Except for replacing carbon black (A-1) with carbon black (X-2), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 7.

[0145] <Comparative Examples 2-3> Except for replacing carbon black (A-1) with carbon black (X-3), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 7.

[0146] Table 6 Table 7 <Example 3-1> Except for replacing carbon nanotubes (B-1) with carbon nanotubes (B-2), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 8.

[0147] <Comparative Example 3-1> Except for replacing carbon nanotubes (B-1) with carbon nanotubes (Y-1), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 8.

[0148] <Comparative Example 3-2> Except for replacing carbon nanotubes (B-1) with carbon nanotubes (Y-2), the preparation of the coating solution for forming the positive electrode, the manufacture of the positive electrode, the manufacture of the negative electrode, the manufacture of the battery, and the evaluation of the battery were carried out in the same manner as in Examples 1-1. The results are shown in Table 8.

[0149] Table 8 In addition, in Tables 4 to 8, “primary particle size (nm)” represents the average primary particle size (nm) of carbon black. Furthermore, “(A) / (B) / (C)” represents the mass ratio of carbon black (A), first carbon nanotubes (B), and second carbon nanotubes (C).

[0150] The results above confirm that the battery made using the cathode composition according to the above embodiments has low internal resistance and excellent cycle characteristics.

Claims

1. A positive electrode composition comprising an active material, a binder material, and a conductive material, said conductive material comprising: Carbon black A with an average primary particle size of 17nm or larger and 30nm or smaller The first carbon nanotube B with a D / G peak ratio of 0.3 to 1.4 in the Raman spectrum, and The second carbon nanotube C with a peak ratio of D / G less than 0.3 in the Raman spectrum.

2. The positive electrode composition according to claim 1, wherein, The carbon black A is selected from the group consisting of furnace black, acetylene black and Ketjen black.

3. The positive electrode composition according to claim 1, wherein, The BET specific surface area of ​​the carbon black A is 100m². 2 / g or more and 900m 2 / g or less.

4. The positive electrode composition according to claim 1, wherein the content of carbon black A is 30% by mass or more and 90% by mass or less, based on the total amount of the conductive material.

5. The positive electrode composition according to claim 1, wherein, based on the total amount of the conductive material, the content of the first carbon nanotube B is 5% by mass or more and 50% by mass or less.

6. The positive electrode composition according to claim 1, wherein, based on the total amount of the conductive material, the content of the second carbon nanotube C is 1% by mass or more and 45% by mass or less.

7. A coating liquid for forming a positive electrode, comprising the positive electrode composition and dispersion medium according to any one of claims 1 to 6.

8. A positive electrode comprising the positive electrode composition according to any one of claims 1 to 6.

9. A battery having the positive electrode as described in claim 8.

10. A conductive material comprising: Carbon black A with an average primary particle size of 17nm or larger and 30nm or smaller The first carbon nanotube B with a D / G peak ratio of 0.3 to 1.4 in the Raman spectrum, and The second carbon nanotube C with a peak ratio of D / G less than 0.3 in the Raman spectrum.

11. A slurry comprising the conductive material and dispersion medium of claim 10.

12. A method for manufacturing a coating liquid for forming a positive electrode, comprising a mixing step of mixing an active substance, a binder, a conductive material, and a dispersion medium. The conductive material comprises: carbon black A with an average primary particle size of 17 nm or more and 30 nm or less; a first carbon nanotube B with a peak ratio of D band to G band in Raman spectroscopy of 0.3 or more and 1.4 or less; and a second carbon nanotube C with a peak ratio of D band to G band in Raman spectroscopy of less than 0.

3.

13. The manufacturing method according to claim 12, wherein the mixing step is a step of mixing the active substance, the binder solution containing the binder material, the slurry A containing the carbon black A, the slurry B containing the first carbon nanotubes B, and the slurry C containing the second carbon nanotubes C.

14. A method for manufacturing a positive electrode, comprising: The process of applying a positive electrode forming liquid manufactured by the manufacturing method of claim 12 or 13 onto a current collector, and forming an agent layer containing the active material, the binder material and the conductive material on the current collector.

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