Positive electrode composition, coating liquid for forming a positive electrode, positive electrode, battery, method for manufacturing a coating liquid for forming a positive electrode, method for manufacturing a positive electrode, and method for manufacturing a battery

Abstract

Provided is a positive electrode composition which contains a first carbon black, a second carbon black and an active material, wherein: the first carbon black has a BET specific surface area of 200 m2 / g or more and a crystallite size (Lc) of 17 Å or less; the second carbon black has a BET specific surface area of 100 m2 / g or more and a crystallite size (Lc) of 19 Å or more; and the ratio C2 / C1 of the content C2 of the second carbon black to the content C1 of the first carbon black is 0.1 to 0.45.

Description

[Technical Field]

[0001] This disclosure relates to a positive electrode composition, a coating solution for forming a positive electrode, a positive electrode, a battery, a method for producing a coating solution for forming a positive electrode, a method for producing a positive electrode, and a method for producing a battery. [Background technology]

[0002] Due to the growing environmental and energy concerns, there is a surge in the development of technologies aimed at realizing a low-carbon society that reduces reliance on fossil fuels. Such technological developments are diverse and include the development of low-emission vehicles such as hybrid electric vehicles and electric vehicles, the development of renewable energy power generation and storage systems such as solar and wind power generation, and the development of next-generation power grids that efficiently supply electricity and reduce transmission losses.

[0003] One of the key devices required for these technologies is the battery, and such batteries need high energy density to miniaturize the system. They also need high output characteristics to enable stable power supply regardless of ambient temperature. Furthermore, they need good cycle characteristics to withstand long-term use. For these reasons, there is a rapid shift from conventional lead-acid batteries, nickel-cadmium batteries, and nickel-metal hydride batteries to lithium-ion secondary batteries, which have higher energy density, output characteristics, and cycle characteristics.

[0004] Conventionally, the positive electrode of a lithium-ion secondary battery is manufactured by coating a current collector with a positive electrode paste containing a positive electrode active material, a conductive material, and a binder. Lithium-containing composite oxides such as lithium cobalt oxide and lithium manganese oxide have been used as the positive electrode active material. Furthermore, because positive electrode active materials have poor conductivity, conductive materials such as carbon black have been added to the positive electrode paste to impart conductivity (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-227481 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In recent years, there has been a growing demand for further performance improvements in batteries such as lithium-ion rechargeable batteries.

[0007] This disclosure aims to provide a positive electrode composition that enables the realization of a positive electrode with low plate resistance and a battery with excellent discharge rate characteristics. Furthermore, this disclosure aims to provide a coating liquid for forming a positive electrode and a method for manufacturing the same, which enable the realization of a positive electrode with low plate resistance and a battery with excellent discharge rate characteristics. Furthermore, this disclosure aims to provide a positive electrode and a method for manufacturing the same, which enable the realization of a battery with excellent discharge rate characteristics. Finally, this disclosure aims to provide a battery equipped with the above-mentioned positive electrode and a method for manufacturing the same. [Means for solving the problem]

[0008] This disclosure includes, for example, the following: <1> ~ <11> Regarding. <1> It contains a first carbon black, a second carbon black, and an active material. The aforementioned first carbon black is 200m 2 It has a BET specific surface area of ​​17 Å or less and a crystallite size (Lc) of 17 Å or less. The aforementioned second carbon black, 100m 2 It has a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 19 Å or more. The ratio of the content of the second carbon black (C2) to the content of the first carbon black (C1) (C2 / C1) is 0.1 or more and 0.45 or less. Cathode composition. <2> The BET specific surface area of ​​the first carbon black is 200 m². 2 / g or more 400m 2 It is less than / g The BET specific surface area of the second carbon black is 100 m 2 / g or more and 400 m 2 / g or less, The positive electrode composition according to <1>. <3> The crystallite size (Lc) of the first carbon black is 14 Å or more and 17 Å or less, The crystallite size (Lc) of the second carbon black is 19 Å or more and 25 Å or less, The positive electrode composition according to <1> or <2>. <4> A positive electrode including a composite material layer made of the positive electrode composition according to any one of <1> to <3>. <5> A battery including the positive electrode according to <4>. <6> Containing a first carbon black, a second carbon black, an active material, and a liquid medium, The first carbon black has a BET specific surface area of 200 m 2 / g or more and a crystallite size (Lc) of 17 Å or less, The second carbon black has a BET specific surface area of 100 m 2 / g or more and a crystallite size (Lc) of 19 Å or more, The ratio C2 / C1 of the content C2 of the second carbon black to the content C1 of the first carbon black is 0.1 or more and 0.45 or less, A coating liquid for forming a positive electrode. <7>[[ID=4l]] A slurry preparation step of preparing a first slurry containing a first carbon black and a first liquid medium and a second slurry containing a second carbon black and a second liquid medium, A mixing step of mixing the first slurry, the second slurry, and an active material to obtain a coating liquid for forming a positive electrode, Including, The first carbon black has a BET specific surface area of 200 m 2 / g or more and a crystallite size (Lc) of 17 Å or less, The second carbon black is 100 m2 It has a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 19 Å or more. The ratio C2 / C1 of the content of the second carbon black to the content of the first carbon black in the positive electrode forming coating liquid, C1, is 0.1 or more and 0.45 or less. A method for manufacturing a coating solution for forming a positive electrode. <8> A method for manufacturing a positive electrode including a current collector and an asphalt layer, A coating solution preparation step is performed to prepare a coating solution for positive electrode formation containing a first carbon black, a second carbon black, an active material, and a liquid medium. A positive electrode forming step involves applying the positive electrode forming liquid onto the current collector to form the composite material layer on the current collector, Includes, The aforementioned first carbon black is 200m 2 It has a BET specific surface area of ​​17 Å or less and a crystallite size (Lc) of 17 Å or less. The aforementioned second carbon black, 100m 2 It has a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 19 Å or more. The ratio C2 / C1 of the content of the second carbon black to the content of the first carbon black in the positive electrode forming coating liquid, C1, is 0.1 or more and 0.45 or less. A method for manufacturing a positive electrode. <9> The aforementioned coating liquid preparation step is <7> The step is to obtain the coating liquid for forming the positive electrode by the manufacturing method described above. <8> The manufacturing method described above. <10> A method for manufacturing a battery comprising a positive electrode including a current collector and an asphalt layer, A coating solution preparation step is performed to prepare a coating solution for positive electrode formation containing a first carbon black, a second carbon black, an active material, and a liquid medium. A positive electrode forming step involves applying the positive electrode forming liquid onto the current collector to form the composite material layer on the current collector, Includes, The aforementioned first carbon black is 200m 2It has a BET specific surface area of ​​17 Å or less and a crystallite size (Lc) of 17 Å or less. The aforementioned second carbon black, 100m 2 It has a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 19 Å or more. The ratio C2 / C1 of the content of the second carbon black to the content of the first carbon black in the positive electrode forming coating liquid, C1, is 0.1 or more and 0.45 or less. Battery manufacturing method. <11> The coating preparation step is a step of obtaining the coating liquid for forming the positive electrode by the manufacturing method described in claim 7. <10> The manufacturing method described above. [Effects of the Invention]

[0009] This disclosure provides a positive electrode composition that enables the realization of a positive electrode with low plate resistance and a battery with excellent discharge rate characteristics. Furthermore, this disclosure provides a coating liquid for forming a positive electrode and a method for manufacturing the same, which enables the realization of a positive electrode with low plate resistance and a battery with excellent discharge rate characteristics. This disclosure also provides a positive electrode and a method for manufacturing the same, which enables the realization of a battery with excellent discharge rate characteristics. Finally, this disclosure provides a battery comprising the above-mentioned positive electrode and a method for manufacturing the same. [Modes for carrying out the invention]

[0010] Preferred embodiments of this disclosure will be described in detail below. In this specification, carbon black may be abbreviated as "CB". In this specification, the tilde symbol "~" is used to indicate a numerical range including the numbers before and after it. Specifically, the notation "X~Y" (where X and Y are both numerical values) indicates "X or greater and Y or less".

[0011] <Coating liquid for positive electrode formation> The positive electrode forming coating liquid of this embodiment contains a first carbon black, a second carbon black, an active material, and a liquid medium. In this embodiment, the first carbon black is 200 ml 2The second carbon black has a BET specific surface area of ​​1 / g or more and a crystallite size (Lc) of 17 Å or less, and is 100 m 2 It has a BET specific surface area of ​​1 / g or more and a crystallite size (Lc) of 19 Å or more. In this embodiment, the ratio C2 / C1 of the content of the second carbon black to the content C1 of the first carbon black is 0.1 or more and 0.45 or less.

[0012] In this specification, the crystallite size (Lc) of carbon black is measured in accordance with JIS R7651. The crystallite size (Lc) of carbon black refers to the crystallite size in the c-axis direction of the carbon black crystalline layer.

[0013] Furthermore, the degree of structure development (a structure in which primary particles are linked, i.e., primary aggregates) in carbon black varies greatly depending on the thermal history during synthesis (for example, thermal history resulting from the thermal decomposition and combustion reaction of fuel oil, thermal decomposition and combustion reaction of raw materials, rapid cooling and reaction cessation by a cooling medium, etc.) and differences in the frequency of primary particle collisions. The larger the crystallite size (Lc), the more developed the structure of the carbon black is considered to be.

[0014] In this specification, the BET specific surface area of ​​carbon black is measured by the static volumetric method in accordance with JIS Z8830, using nitrogen as the adsorbate.

[0015] By applying and drying the positive electrode forming coating liquid of this embodiment, a composite layer consisting of a positive electrode composition is obtained. That is, by applying the positive electrode forming coating liquid of this embodiment onto a current collector and drying it, a positive electrode including a current collector and a composite layer provided on the current collector can be obtained. A positive electrode obtained from the positive electrode forming coating liquid of this embodiment enables the realization of a battery with low internal resistance and excellent discharge rate characteristics.

[0016] In this embodiment, the reason why the above effects are achieved is not entirely clear, but the applicant believes it to be as follows. The cathode forming coating liquid of this embodiment contains a first carbon black with a small crystallite size (Lc), a small degree of structural development, and a large specific surface area, and a second carbon black with a large crystallite size (Lc) and a large degree of structural development. The first carbon black has a small degree of structural development and a large specific surface area, so it is thought to be easily distributed on the surface of the active material in the cathode composition. The second carbon black has a large degree of structural development, so it is thought to be easily positioned between active materials in the cathode composition. For this reason, by using the first carbon black and the second carbon black in an appropriate ratio, the conductive material is efficiently distributed both on the surface of the active material and between the active materials, efficient conductive paths are formed, and the above effects are obtained.

[0017] In this embodiment, a first carbon black and a second carbon black are used in combination. The first carbon black is 200m 2 It has a BET specific surface area of ​​1 / g or more and a crystallite size (Lc) of 17 Å or less. The second carbon black is 100 m 2 It has a BET specific surface area of ​​1 / g or more and a crystallite size (Lc) of 19 Å or more.

[0018] The BET specific surface area of ​​the first carbon black is 200 m². 2 From the viewpoint of obtaining higher conductivity by increasing the contact area with the positive electrode active material, which is greater than or equal to / g, 220m 2 / g or more, 240m 2 / g or more, 260m 2 / g or more or 280m 2 It may be 1 / g or more. Also, the BET specific surface area of ​​the first carbon black is, for example, 400m². 2 It may be less than or equal to / g, and from the viewpoint of easier uniform dispersion around the positive electrode active material, 380m 2 / g or less, 360m 2 / g or less or 340m 2It may be less than / g. That is, the BET specific surface area of ​​the first carbon black is, for example, 200m². 2 / g or more 400m 2 / g or less, 200m 2 / g or more 380m 2 / g or less, 200m 2 / g or more 360m 2 / g or less, 200m 2 / g or more 340m 2 / g or less, 220m 2 / g or more 400m 2 / g or less, 220m 2 / g or more 380m 2 / g or less, 220m 2 / g or more 360m 2 / g or less, 220m 2 / g or more 340m 2 / g or less, 240m 2 / g or more 400m 2 / g or less, 240m 2 / g or more 380m 2 / g or less, 240m 2 / g or more 360m 2 / g or less, 240m 2 / g or more 340m 2 / g or less, 260m 2 / g or more 400m 2 / g or less, 260m 2 / g or more 380m 2 / g or less, 260m 2 / g or more 360m 2 / g or less, 260m 2 / g or more 340m 2 / g or less, 280m 2 / g or more 400m 2 / g or less, 280m 2 / g or more 380m 2 / g or less, 280m 2 / g or more 360m 2 / g or less, or 280m 2 / g or more 340m 2 It may be less than / g.

[0019] The BET specific surface area of ​​the second carbon black is 100m². 2 / g or more, from the viewpoint that a thicker conductive path is formed between the positive electrode active materials and higher conductivity is obtained, 120 m 2 / g or more, 140 m 2 / g or more, 160 m 2 / g or more, 180 m 2 / g or more, 200 m 2 / g or more or 220 m 2 / g or more may be used. Also, the BET specific surface area of the second carbon black may be, for example, 400 m 2 / g or less, and from the viewpoint that it is likely to be uniformly dispersed between the positive electrode active materials, 390 m 2 / g or less, 380 m 2 / g or less or 370 m 2 / g or less may be used. That is, the BET specific surface area of the second carbon black is, for example, 100 m 2 / g or more and 400 m 2 / g or less, 100 m 2 / g or more and 390 m 2 / g or less, 100 m 2 / g or more and 380 m 2 / g or less, 100 m 2 / g or more and 370 m 2 / g or less, 120 m 2 / g or more and 400 m 2 / g or less, 120 m 2 / g or more and 390 m 2 / g or less, 120 m 2 / g or more and 380 m 2 / g or less, 120 m 2 / g or more and 370 m 2 / g or less, 140 m 2 / g or more and 400 m 2 / g or less, 140 m 2 / g or more and 390 m 2 / g or less, 140 m 2 / g or more and 380 m 2 / g or less, 140 m 2 / g or more and 370 m 2 / g or less, 160 m 2 / g or more and 400 m 2 / g or less, 160 m 2 / g or more and 390 m 2 / g or less, 160 m 2 / g or more and 380 m2 / g or less, 160m 2 / g or more 370m 2 / g or less, 180m 2 / g or more 400m 2 / g or less, 180m 2 / g or more 390m 2 / g or less, 180m 2 / g or more 380m 2 / g or less, 180m 2 / g or more 370m 2 / g or less, 200m 2 / g or more 400m 2 / g or less, 200m 2 / g or more 390m 2 / g or less, 200m 2 / g or more 380m 2 / g or less, 200m 2 / g or more 370m 2 / g or less, 220m 2 / g or more 400m 2 / g or less, 220m 2 / g or more 390m 2 / g or less, 220m 2 / g or more 380m 2 / g or less, or 220m 2 / g or more 370m 2 It may be less than / g.

[0020] The crystallite size (Lc) of the first carbon black is 17 Å or less. From the viewpoint of making the particle shape of the carbon black more rounded, reducing interparticle interactions, making it easier to disperse more uniformly in the active material, and facilitating the formation of conductive pathways, thereby making it easier to obtain better battery characteristics, it may be 16.8 Å or less, 16.6 Å or less, or 16.4 Å or less. Alternatively, the crystallite size (Lc) of the first carbon black may be, for example, 14 Å or more. From the viewpoint of making it easier for π electrons to move through the crystal layer, facilitating the formation of conductive pathways that carry electrons flowing from the current collector to the active material, thereby making it easier to obtain better battery characteristics, it may be 14.5 Å or more, 15 Å or more, 15.5 Å or more, or 15.7 Å or more. In other words, the crystallite size (Lc) of the first carbon black is, for example, 14 Å to 17 Å, 14 Å to 16.8 Å, 14 Å to 16.6 Å, 14 Å to 16.4 Å, 14.5 Å to 17 Å, 14.5 Å to 16.8 Å, 14.5 Å to 16.6 Å, 14.5 Å to 16.4 Å, 15 Å to 17 Å, 15 Å to 1 It may be 6.8 Å or less, 15 Å to 16.6 Å, 15 Å to 16.4 Å, 15.5 Å to 17 Å, 15.5 Å to 16.8 Å, 15.5 Å to 16.6 Å, 15.5 Å to 16.4 Å, 15.7 Å to 17 Å, 15.7 Å to 16.8 Å, 15.7 Å to 16.6 Å, or 15.7 Å to 16.4 Å.

[0021] The crystallite size (Lc) of the second carbon black may be 19 Å or larger, and from the viewpoint of making it easier for π electrons to move through the crystal layer, making it easier to form conductive pathways that carry electrons flowing from the current collector to the active material, and thus making it easier to obtain better battery characteristics, it may be 19.2 Å or larger, 19.4 Å or larger, or 19.6 Å or larger. Alternatively, the crystallite size (Lc) of the second carbon black may be, for example, 25 Å or smaller, and from the viewpoint of making the particle shape of the carbon black more rounded, reducing interparticle interactions, making it easier to disperse more uniformly in the active material, making it easier to form conductive pathways, and thus making it easier to obtain better battery characteristics, it may be 24 Å or smaller, 23 Å or smaller, 22 Å or smaller, or 21 Å or smaller. In other words, the crystallite size (Lc) of the second carbon black may be, for example, 19 Å to 25 Å, 19 Å to 24 Å, 19 Å to 23 Å, 19 Å to 22 Å, 19 Å to 21 Å, 19.2 Å to 25 Å, 19.2 Å to 24 Å, 19.2 Å to 23 Å, 19.2 Å to 22 Å, 19.2 Å to 21 Å, 19.4 Å to 25 Å, 19.4 Å to 24 Å, 19.4 Å to 23 Å, 19.4 Å to 22 Å, 19.4 Å to 21 Å, 19.6 Å to 25 Å, 19.6 Å to 24 Å, 19.6 Å to 23 Å, 19.6 Å to 22 Å, or 19.6 Å to 21 Å.

[0022] In this specification, the crystallite size (Lc) of carbon black is measured in accordance with JIS R7651. The crystallite size (Lc) of carbon black refers to the crystallite size in the c-axis direction of the carbon black crystalline layer.

[0023] The DBP absorption rate of the first carbon black may be, for example, 140 mL / 100g or more, 150 mL / 100g or more, 160 mL / 100g or more, or 170 mL / 100g or more. Alternatively, the DBP absorption rate of the first carbon black may be, for example, 300 mL / 100g or less, 280 mL / 100g or less, 260 mL / 100g or less, or 240 mL / 100g or less. In other words, the DBP absorption amount of the first carbon black is, for example, 140 mL / 100g to 300 mL / 100g, 140 mL / 100g to 280 mL / 100g, 140 mL / 100g to 260 mL / 100g, 140 mL / 100g to 240 mL / 100g, 150 mL / 100g to 300 mL / 100g, 150 mL / 100g to 280 mL / 100g, 150 mL / 100g to 260 mL / 100g, and 150 mL / 100g to 240 It may be mL / 100g or less, 160 mL / 100g to 300 mL / 100g, 160 mL / 100g to 280 mL / 100g, 160 mL / 100g to 260 mL / 100g, 160 mL / 100g to 240 mL / 100g, 170 mL / 100g to 300 mL / 100g, 170 mL / 100g to 280 mL / 100g, 170 mL / 100g to 260 mL / 100g, or 170 mL / 100g to 240 mL / 100g.

[0024] The DBP absorption rate of the second carbon black may be, for example, 200 mL / 100 g or more, and may also be 220 mL / 100 g or more, 240 mL / 100 g or more, or 260 mL / 100 g or more. Alternatively, the DBP absorption rate of the second carbon black may be, for example, 450 mL / 100 g or less, and may also be 420 mL / 100 g or less, 400 mL / 100 g or less, or 380 mL / 100 g or less. In other words, the DBP absorption amount of the second carbon black is, for example, 200 mL / 100g to 450 mL / 100g, 200 mL / 100g to 420 mL / 100g, 200 mL / 100g to 400 mL / 100g, 200 mL / 100g to 380 mL / 100g, 220 mL / 100g to 450 mL / 100g, 220 mL / 100g to 420 mL / 100g, 220 mL / 100g to 400 mL / 100g, and 220 mL / 100g to 380 mL / 100g. It may be mL / 100g or less, 240 mL / 100g to 450 mL / 100g, 240 mL / 100g to 420 mL / 100g, 240 mL / 100g to 400 mL / 100g, 240 mL / 100g to 380 mL / 100g, 260 mL / 100g to 450 mL / 100g, 260 mL / 100g to 420 mL / 100g, 260 mL / 100g to 400 mL / 100g, or 260 mL / 100g to 380 mL / 100g.

[0025] In this specification, DBP absorption is an index used to evaluate the ability of carbon black particles to absorb dibutyl phthalate (DBP) into the voids formed by their particle surface and structure. In this specification, DBP absorption is expressed as a value obtained by converting the value measured by the method described in JIS K6217-4:2008 to the value measured by the method described in JIS K6221 using the following formula (a). DBP absorption amount = (A - 10.974) / 0.7833 …(a) [In the formula, A represents the value of DBP absorption measured by the method described in JIS K6221.]

[0026] The average primary particle diameter of the first carbon black may be, for example, 5 nm or more, and from the viewpoint of reducing interparticle interactions between carbon black particles and making it easier to obtain better dispersibility, it may be 7 nm or more, 9 nm or more, or 11 nm or more. Alternatively, the average primary particle diameter of the first carbon black may be, for example, 21 nm or less, and from the viewpoint of increasing the number of conductive paths to the positive electrode active material and making it easier to obtain higher battery characteristics, it may be 19 nm or less, 18 nm or less, or 17 nm or less. That is, the average primary particle diameter of the first carbon black may be, for example, 5 nm to 21 nm, 5 nm to 19 nm, 5 nm to 18 nm, 5 nm to 17 nm, 7 nm to 21 nm, 7 nm to 19 nm, 7 nm to 18 nm, 7 nm to 17 nm, 9 nm to 21 nm, 9 nm to 19 nm, 9 nm to 18 nm, 9 nm to 17 nm, 11 nm to 21 nm, 11 nm to 19 nm, 11 nm to 18 nm, or 11 nm to 17 nm.

[0027] The average primary particle diameter of the second carbon black may be, for example, 10 nm or more, and from the viewpoint of reducing interparticle interactions between carbon black particles and making it easier to obtain better dispersibility, it may be 12 nm or more, 14 nm or more, or 16 nm or more. Alternatively, the average primary particle diameter of the second carbon black may be, for example, 30 nm or less, and from the viewpoint of increasing the number of conductive paths to the positive electrode active material and making it easier to obtain higher battery characteristics, it may be 27 nm or less, 24 nm or less, or 22 nm or less. In other words, the average primary particle diameter of the second carbon black may be, for example, 10 nm to 30 nm, 10 nm to 27 nm, 10 nm to 24 nm, 10 nm to 22 nm, 12 nm to 30 nm, 12 nm to 27 nm, 12 nm to 24 nm, 12 nm to 22 nm, 14 nm to 30 nm, 14 nm to 27 nm, 14 nm to 24 nm, 14 nm to 22 nm, 16 nm to 30 nm, 16 nm to 27 nm, 16 nm to 24 nm, or 16 nm to 22 nm.

[0028] In this specification, the average primary particle diameter of carbon black can be determined by measuring the primary particle diameter of 100 or more carbon black particles randomly selected from a transmission electron microscope (TEM) image magnified 50,000 times, and calculating the average value. Primary particles of carbon black have a small aspect ratio and a shape close to a perfect sphere, but they are not perfectly spherical. Therefore, in this embodiment, the maximum of the line segments connecting two points on the outer circumference of the primary particle in the TEM image is defined as the primary particle diameter of the carbon black.

[0029] The ash content of the first carbon black and the second carbon black may be, for example, 0.1% by mass or less, 0.05% by mass or less, or 0.02% by mass or less. The ash content can be reduced, for example, by classifying the carbon black using a device such as a dry cyclone.

[0030] In this specification, the ash content of carbon black is measured in accordance with JIS K1469:2003.

[0031] The iron content of the first carbon black and the second carbon black may be, for example, 0.1% by mass or less, 0.02% by mass or less, or 0.005% by mass or less. The iron content can be reduced, for example, by bringing the carbon black into contact with a magnet.

[0032] The iron content of carbon black can be measured by inductively coupled plasma mass spectrometry after pretreatment by acid decomposition according to JIS K0116:2014. Specifically, it can be measured by the following method: First, 1 g of carbon black is accurately weighed into a quartz beaker and heated in an electric furnace at 800°C for 3 hours in an atmospheric environment. Next, 10 mL of mixed acid (70% hydrochloric acid, 30% nitric acid) and 10 mL or more of ultrapure water are added to the residue and heated on a hot plate at 200°C for 1 hour to dissolve. After cooling, the solution diluted and adjusted to 25 mL with ultrapure water is measured using an inductively coupled plasma mass spectrometer (Agilent 8800, manufactured by Agilent).

[0033] When carbon black has a low ash and iron content, the incorporation of foreign substances such as metals and ceramics due to damage to equipment during the mixing process can be more significantly suppressed. Furthermore, the reduction in conductivity within electrodes due to the incorporation of ash, insulating foreign substances, etc., can also be suppressed. Therefore, carbon black with low ash and iron content is suitable for use in lithium-ion secondary batteries where high safety is required.

[0034] The method for producing the first and second carbon blacks is not particularly limited. For example, raw materials such as hydrocarbons can be supplied from a nozzle located upstream of the reactor, carbon black can be produced by a thermal decomposition reaction and / or a combustion reaction, and collected from a bag filter directly connected to the downstream of the reactor.

[0035] The raw materials used are not particularly limited and can include gaseous hydrocarbons such as acetylene, methane, ethane, propane, ethylene, propylene, and butadiene, as well as oily hydrocarbons such as toluene, benzene, xylene, gasoline, kerosene, diesel fuel, and heavy oil. Among these, it is preferable to use acetylene, which has a low impurity content. Acetylene has a greater heat of decomposition than other raw materials, allowing the temperature inside the reactor to be raised. As a result, nucleation of carbon black becomes dominant over particle growth by addition reactions, and the primary particle size of carbon black can be reduced.

[0036] Furthermore, it is preferable to supply oxygen, carbon dioxide, hydrogen, nitrogen, steam, etc., to the reactor in addition to the raw materials that serve as the carbon source. These gases other than the raw materials promote gas agitation in the reactor and increase the frequency of collisions and fusions between primary particles of carbon black produced from the raw materials. Therefore, using gases other than the raw materials tends to facilitate the development of primary aggregates of carbon black. It is preferable to use oxygen as the gas other than the raw materials. When oxygen is used, some of the raw materials burn, raising the temperature in the reactor and making it easier to obtain carbon black with small particle size and high specific surface area. Multiple gases can also be used as gases other than the raw materials. The supply point for gases other than the raw materials is preferably the upstream part of the reactor, and it is preferable to supply them from a nozzle separate from the raw materials. This allows for efficient agitation of the raw materials also supplied from the upstream part, and tends to facilitate the development of primary aggregates.

[0037] In conventional carbon black production, a cooling medium such as water is sometimes introduced from the downstream end of the reactor to stop the thermal decomposition and combustion reactions of the raw materials. However, this does not have the effect of developing primary aggregates, and on the other hand, rapid temperature changes may lead to large variations in properties. Therefore, in this embodiment, it is preferable not to introduce a cooling medium from the downstream end of the reactor.

[0038] The first and second carbon blacks are not limited to carbon blacks directly obtained by the reaction furnace described above, but can also be obtained, for example, by pulverizing the obtained carbon black or by mixing carbon blacks produced under different conditions.

[0039] In this embodiment, the first carbon black and the second carbon black function as conductive materials. The cathode forming coating liquid of this embodiment may further contain other conductive materials other than the first carbon black and the second carbon black. Examples of other conductive materials include carbon materials other than those mentioned above, such as carbon black and carbon nanotubes.

[0040] In this embodiment, the content of other conductive materials (e.g., other carbon materials) may be, for example, 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, or even 0 parts by mass, based on 100 parts by mass of the total amount of the first carbon black and the second carbon black.

[0041] In the coating solution for forming the positive electrode, the ratio C2 / C1 of the content of the second carbon black to the content C1 of the first carbon black is 0.1 or higher. From the viewpoint of reducing the interparticle interaction between carbon black particles, making it easier to disperse more uniformly in the active material, and facilitating the formation of conductive pathways, thereby making it easier to obtain better battery characteristics, the ratio may be 0.13 or higher, 0.15 or higher, 0.17 or higher, or 0.2 or higher. Alternatively, the above ratio C2 / C1 may be 0.45 or lower. From the viewpoint of making it easier for π electrons to move through the crystal layer, facilitating the formation of conductive pathways that carry electrons flowing from the current collector to the active material, thereby making it easier to obtain better battery characteristics, the ratio may be 0.42 or lower, 0.4 or lower, 0.38 or lower, or 0.35 or lower. In other words, the above ratio C2 / C1 is, for example, 0.1 to 0.45, 0.1 to 0.42, 0.1 to 0.4, 0.1 to 0.38, 0.1 to 0.35, 0.13 to 0.45, 0.13 to 0.42, 0.13 to 0.4, 0.13 to 0.38, 0.13 to 0.35, 0.15 to 0.45, 0.15 to 0.42, 0 It may be 0.15 or more and 0.4 or less, 0.15 or more and 0.38 or less, 0.15 or more and 0.35 or less, 0.17 or more and 0.45 or less, 0.17 or more and 0.42 or less, 0.17 or more and 0.4 or less, 0.17 or more and 0.38 or less, 0.17 or more and 0.35 or less, 0.2 or more and 0.45 or less, 0.2 or more and 0.42 or less, 0.2 or more and 0.4 or less, 0.2 or more and 0.38 or less, or 0.2 or more and 0.35 or less.

[0042] In the coating solution for forming the positive electrode, the total content of the first carbon black and the second carbon black (C1+C2) may be, for example, 0.5 parts by mass or more per 100 parts by mass of active material. From the viewpoint of increasing the number of conductive paths to the positive electrode active material and making it easier to obtain higher battery characteristics, it may be 0.75 parts by mass or more, 1 part by mass or more, or 1.5 parts by mass or more. Alternatively, in the coating solution for forming the positive electrode, the total content of the first carbon black and the second carbon black (C1+C2) may be, for example, 4.0 parts by mass or less per 100 parts by mass of active material. From the viewpoint of reducing the interparticle interaction between carbon black particles, making it easier to disperse more uniformly in the active material, and making it easier to form conductive paths and make it easier to obtain better battery characteristics, it may be 3.5 parts by mass or less, 3.0 parts by mass or less, or 2.5 parts by mass or less. That is, the above total content (C1+C2) is, for example, 0.5 parts by mass or more and 4.0 parts by mass or less, 0.5 parts by mass or more and 3.5 parts by mass or less, and 0.5 parts by mass, based on 100 parts by mass of the active material. 3.0 parts by mass or more, 0.5 parts by mass or more and 2.5 parts by mass or less, 0.75 parts by mass or more and 4.0 parts by mass or less, 0.75 parts by mass or more and 3.5 parts by mass or less, 0.75 parts by mass or more and 3.0 parts by mass The following may be 0.75 parts by mass to 2.5 parts by mass, 1 part by mass to 4.0 parts by mass, 1 part to 3.5 parts by mass, 1 part to 3.0 parts by mass, 1 part by mass to 2.5 parts by mass, 1.5 parts by mass to 4.0 parts by mass, 1.5 parts by mass to 3.5 parts by mass, 1.5 parts by mass to 3.0 parts by mass, or 1.5 parts by mass to 2.5 parts by mass.

[0043] The active material can be any substance capable of reversibly intercalating and deintercalating cations. The active material can also be called the positive electrode active material.

[0044] The active material is not particularly limited; for example, known active materials used in lithium-ion secondary batteries can be used without any restrictions. Examples of active materials include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel-manganese-cobalt oxide, and lithium iron phosphate.

[0045] For example, the active material has a volume resistivity of 1 × 10⁻⁶. 4It may be a lithium-containing composite oxide or lithium-containing polyanionic compound containing manganese of Ω·cm or more. Examples of manganese-containing lithium-containing composite oxides include LiMnO2, LiMnO3, LiMn2O3, Li 1+x Mn 2-x Lithium manganese oxide such as O4 (where x = 0 to 0.33); LiMn x Ni y Co z O2 (however, 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 to 0.33, y = 0 to 1.0, 2-xy > 0), LiMn 2-x M x Examples of composite oxides containing one or more transition metal elements include O2 (where x = 0.01 to 0.1) and Li2Mn3MO8. Examples of lithium-containing polyanionic compounds include LiFePO4, LiMnPO4, and Li2MPO4F (where M is at least one metal selected from Co, Ni, Fe, Cr, and Zn). In each compositional formula, M is at least one selected from the group consisting of Fe, Co, Ni, Al, Cu, Mg, Cr, Zn, and Ta.

[0046] Average particle size of the active material (D 50 The average particle size of the active material (D) may be, for example, 20 μm or less or 10 μm or less, from the viewpoint of ensuring sufficient bonding between the conductive material and the binder and making it easier to improve battery characteristics. 50 The average particle size of the active material (D) may be, for example, 200 nm or larger or 1 μm or larger, from the viewpoint of making it easier to improve battery characteristics. 50 ) can be measured by laser light scattering.

[0047] The active material content in the positive electrode forming coating liquid may be, for example, 90% by mass or more, based on the total mass of solids in the positive electrode forming coating liquid, and from the viewpoint of further improving the discharge rate characteristics, it may be 91% by mass or more, 92% by mass or more, or 93% by mass or more. Alternatively, the active material content in the positive electrode forming coating liquid may be, for example, 99% by mass or less, based on the total mass of solids in the positive electrode forming coating liquid, and from the viewpoint of further reducing the internal resistance, it may be 98% by mass or less, 97% by mass or less, or 96% by mass or less. In other words, the content of the active material in the coating liquid for forming the positive electrode may be, for example, 90% by mass or more and 99% by mass or less, 90% by mass or more and 98% by mass or less, 90% by mass or more and 97% by mass or less, 90% by mass or more and 96% by mass or less, based on the total mass of the solid content of the coating liquid for forming the positive electrode.

[0048] Examples of liquid media include water, N-methyl-2-pyrrolidone, cyclohexane, methyl ethyl ketone, and methyl isobutyl ketone. Of these, N-methyl-2-pyrrolidone is preferred from the viewpoint of dispersibility.

[0049] The content of the liquid medium is not particularly limited, and for example, it may be adjusted as appropriate so that the solid content concentration of the coating solution for forming the positive electrode falls within the preferred range described later.

[0050] The coating solution for forming the positive electrode may further contain a binder.

[0051] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene copolymer, and (meth)acrylic acid ester copolymer. The polymer structure of the binder may be, for example, random copolymer, alternating copolymer, graft copolymer, block copolymer, etc. From the viewpoint of excellent dielectric strength, polyvinylidene fluoride is preferred as the binder.

[0052] The amount of binder in the coating solution for forming the positive electrode may be, for example, 0.5 parts by mass or more per 100 parts by mass of active material. From the viewpoint of improving the bonding properties of the positive electrode plate and making it easier to obtain higher battery characteristics, it may be 0.8 parts by mass or more, 1.0 parts by mass or more, or 1.5 parts by mass or more. Alternatively, the amount of binder in the coating solution for forming the positive electrode may be, for example, 5.0 parts by mass or less per 100 parts by mass of active material. From the viewpoint of reducing the resistance component derived from the binder and making it easier to obtain higher battery characteristics, it may be 4.5 parts by mass or less, 4.0 parts by mass or less, or 3.5 parts by mass or less. In other words, the amount of binder in the coating liquid for forming the positive electrode may be, for example, 0.5 parts by mass or more and 5.0 parts by mass or less, 0.5 parts by mass or more and 4.5 parts by mass or less, 0.5 parts by mass or more and 4.0 parts by mass or less, 0.5 parts by mass or more and 3.5 parts by mass or less, 0.8 parts by mass or more and 5.0 parts by mass or less, 0.8 parts by mass or more and 4.5 parts by mass or less, 0.8 parts by mass or more and 4.0 parts by mass or less, 0.8 parts by mass or more and 3.5 parts by mass or less, 1.0 parts by mass or more and 5.0 parts by mass or less, 1.0 parts by mass or more and 4.5 parts by mass or less, 1.0 parts by mass or more and 4.0 parts by mass or less, 1.0 parts by mass or more and 3.5 parts by mass or less, 1.5 parts by mass or more and 5.0 parts by mass or less, 1.5 parts by mass or more and 4.5 parts by mass or less, 1.5 parts by mass or more and 4.0 parts by mass or less, or 1.5 parts by mass or more and 3.5 parts by mass or less, per 100 parts by mass of active material.

[0053] The coating solution for forming the positive electrode may further contain a dispersant for carbon black. The dispersant can be any component that has the function of assisting in the dispersion of carbon black in a liquid medium.

[0054] Examples of dispersants include high-molecular-weight dispersants and low-molecular-weight dispersants. From the viewpoint of long-term dispersion stability of conductive materials (carbon black), high-molecular-weight dispersants are preferred.

[0055] The dispersant may be selected from the group consisting of, for example, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, carboxymethylcellulose and its salts, polyvinyl acetal, polyvinyl acetate, polyvinylamine, and polyvinyl formal.

[0056] The amount of dispersant in the coating solution for forming the positive electrode may be, for example, 5 parts by mass or more, based on 100 parts by mass of the total of the first carbon black and the second carbon black (C1+C2). From the viewpoint of reducing the interparticle interactions between the carbon black particles, making it easier to disperse more uniformly in the active material, and facilitating the formation of conductive paths, thereby making it easier to obtain better battery characteristics, the amount may be 6 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more. Alternatively, the amount of dispersant in the coating solution for forming the positive electrode may be, for example, 50 parts by mass or less, based on 100 parts by mass of the total of the first carbon black and the second carbon black (C1+C2). From the viewpoint of reducing the resistance component derived from the dispersant and making it easier to obtain higher battery characteristics, the amount may be 45 parts by mass or less, 40 parts by mass or less, or 35 parts by mass or less. In other words, the amount of dispersant in the coating liquid for forming the positive electrode may be, for example, 5 to 50 parts by mass, 5 to 45 parts by mass, 5 to 40 parts by mass, 5 to 35 parts by mass, 6 to 50 parts by mass, 6 to 45 parts by mass, 6 to 40 parts by mass, 6 to 35 parts by mass, 8 to 50 parts by mass, 8 to 45 parts by mass, 8 to 40 parts by mass, 8 to 35 parts by mass, 10 to 50 parts by mass, 10 to 45 parts by mass, 10 to 40 parts by mass, or 10 to 35 parts by mass, with the total of the first and second carbon blacks (C1+C2) being 100 parts by mass.

[0057] The solid content concentration of the coating solution for forming the positive electrode is not particularly limited and may be, for example, 50% by mass or more. From the viewpoint of shortening the drying time of the liquid medium when manufacturing the positive electrode and further suppressing the migration of the conductive material when drying the liquid medium, it may be 55% by mass or more, 60% by mass or more, or 65% by mass or more. Furthermore, the solid content concentration of the coating solution for forming the positive electrode is not particularly limited and may be, for example, 90% by mass or less. From the viewpoint of making the coating film smoother when manufacturing the positive electrode and further reducing the variation in the internal resistance of the battery, it may be 85% by mass or less, 80% by mass or less, or 75% by mass or less. That is, the solid content concentration of the positive electrode forming coating liquid is, for example, 50 mass% or more and 90 mass% or less, 50 mass% or more and 85 mass% or less, 50 mass% or more and 80 mass% or less, 50 mass% or more and 75 mass% or less, 55 mass% or more and 90 mass% or less, 55 mass% or more and 85 mass% or less, 55 mass% or more and 80 mass% or less, and 55 mass% or more. It may be 5 mass% or less, 60 mass% or more and 90 mass% or less, 60 mass% or more and 85 mass% or less, 60 mass% or more and 75 mass% or less, 65 mass% or more and 90 mass% or less, 65 mass% or more and 85 mass% or less, 65 mass% or more and 80 mass% or less, or 65 mass% or more and 75 mass% or less.

[0058] The method for manufacturing the coating solution for forming the positive electrode is not particularly limited.

[0059] The coating solution for forming the positive electrode may be manufactured by a manufacturing method that includes, for example, a slurry preparation step of preparing a first slurry containing a first carbon black and a first liquid medium, and a second slurry containing a second carbon black and a second liquid medium, and a mixing step of mixing the first slurry, the second slurry, and an active material to obtain the coating solution for forming the positive electrode. By providing a slurry preparation step in which the first slurry and the second slurry are prepared separately, it is easier to obtain a battery with lower internal resistance and better discharge rate characteristics than when a mixed slurry is prepared by mixing the powder of the first carbon black and the powder of the second carbon black.

[0060] The first slurry may be a mixture of the first carbon black and the first liquid medium. That is, the above manufacturing method may further include a step of mixing the first carbon black and the first liquid medium to form the first slurry.

[0061] Examples of the first liquid medium include the same liquid medium as that used in the positive electrode forming composition described above.

[0062] The content of the first liquid medium in the first slurry is not particularly limited and may be adjusted as appropriate so that the solid content concentration of the first slurry falls within the range described below.

[0063] The first slurry may further contain a carbon black dispersant. Examples of dispersants include those identical to those used in the cathode-forming composition described above.

[0064] The amount of dispersant in the first slurry may be, for example, 5 parts by mass or more per 100 parts by mass of the first carbon black, and from the viewpoint of improving the dispersibility of the carbon black in the slurry and making it easier to obtain a low-viscosity slurry, it may be 6 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more. Alternatively, the amount of dispersant in the first slurry may be, for example, 25 parts by mass or less per 100 parts by mass of the first carbon black, and from the viewpoint of reducing the resistance component derived from the dispersant and making it easier to obtain higher battery characteristics, it may be 24 parts by mass or less, 23 parts by mass or less, or 22 parts by mass or less. In other words, the content of the dispersant in the first slurry may be, for example, 5 to 25 parts by mass, 5 to 24 parts by mass, 5 to 23 parts by mass, 5 to 22 parts by mass, 6 to 25 parts by mass, 6 to 24 parts by mass, 6 to 23 parts by mass, 6 to 22 parts by mass, 8 to 25 parts by mass, 8 to 24 parts by mass, 8 to 23 parts by mass, 8 to 22 parts by mass, 10 to 25 parts by mass, 10 to 24 parts by mass, 10 to 23 parts by mass, or 10 to 22 parts by mass per 100 parts by mass of the first carbon black.

[0065] The solid content concentration of the first slurry is not particularly limited and may be, for example, 5% by mass or more, 7% by mass or more, or 10% by mass or more. Furthermore, the solid content concentration of the first slurry is not particularly limited and may be, for example, 25% by mass or less, 20% by mass or less, or 15% by mass or less. That is, the solid content concentration of the first slurry may be, for example, 5% by mass or more and 25% by mass or less, 5% by mass or more and 20% by mass or less, 5% by mass or more and 15% by mass or less, 7% by mass or more and 25% by mass or less, 7% by mass or more and 20% by mass or less, 7% by mass or more and 15% by mass or less, 10% by mass or more and 25% by mass or less, 10% by mass or more and 20% by mass or less, or 10% by mass or more and 15% by mass or less.

[0066] The second slurry may be a mixture of the second carbon black and the second liquid medium. That is, the above manufacturing method may further include a step of mixing the second carbon black and the second liquid medium to form a second slurry.

[0067] Examples of the second liquid medium include the same liquid medium as that used in the positive electrode forming composition described above.

[0068] The content of the second liquid medium in the second slurry is not particularly limited, and may be adjusted as appropriate so that the solid content concentration of the second slurry falls within the range described below.

[0069] The second slurry may further contain a carbon black dispersant. Examples of dispersants include those identical to those used in the cathode-forming composition described above.

[0070] The amount of dispersant in the second slurry may be, for example, 5 parts by mass or more per 100 parts by mass of the second carbon black. From the viewpoint of improving the dispersibility of the carbon black in the slurry and making it easier to obtain a low-viscosity slurry, it may be 6 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more. Alternatively, the amount of dispersant in the second slurry may be, for example, 25 parts by mass or less per 100 parts by mass of the second carbon black. From the viewpoint of reducing the resistance component derived from the dispersant and making it easier to obtain higher battery characteristics, it may be 24 parts by mass or less, 23 parts by mass or less, or 22 parts by mass or less. In other words, the content of the dispersant in the second slurry may be, for example, 5 to 25 parts by mass, 5 to 24 parts by mass, 5 to 23 parts by mass, 5 to 22 parts by mass, 6 to 25 parts by mass, 6 to 24 parts by mass, 6 to 23 parts by mass, 6 to 22 parts by mass, 8 to 25 parts by mass, 8 to 24 parts by mass, 8 to 23 parts by mass, 8 to 22 parts by mass, 10 to 25 parts by mass, 10 to 24 parts by mass, 10 to 23 parts by mass, or 10 to 22 parts by mass per 100 parts by mass of the second carbon black.

[0071] The solid content concentration of the second slurry is not particularly limited and may be, for example, 5% by mass or more, 7% by mass or more, or 10% by mass or more. Furthermore, the solid content concentration of the second slurry is not particularly limited and may be, for example, 30% by mass or less, 25% by mass or less, or 20% by mass or less. In other words, the solid content concentration of the second slurry may be, for example, 5% by mass or more and 30% by mass or less, 5% by mass or more and 25% by mass or less, 5% by mass or more and 20% by mass or less, 7% by mass or more and 30% by mass or less, 7% by mass or more and 25% by mass or less, 7% by mass or more and 20% by mass or less, 10% by mass or more and 30% by mass or less, 10% by mass or more and 25% by mass or less, or 10% by mass or more and 20% by mass or less.

[0072] The method for mixing the first slurry, the second slurry, and the active material is not particularly limited and may be carried out by known methods (for example, stirring and mixing using a ball mill, sand mill, twin-screw kneader, orbital agitator, planetary mixer, disper mixer, etc.). The first slurry, the second slurry, and the active material may be mixed simultaneously or sequentially.

[0073] <Positive electrode composition> The positive electrode composition of this embodiment contains a first carbon black, a second carbon black, and an active material. The positive electrode composition may further contain a binder. The positive electrode composition may further contain a carbon black dispersant.

[0074] The positive electrode composition may be a composition containing the solid components of the positive electrode forming coating solution, or it may be obtained by removing at least a portion of the liquid medium from the positive electrode forming coating solution. The content ratio of each component in the positive electrode composition may be the same as the content ratio of each component in the positive electrode forming coating solution.

[0075] <Positive electrode> The positive electrode of this embodiment includes a composite layer made of a positive electrode composition and a current collector.

[0076] The positive electrode of this embodiment may be manufactured, for example, by a manufacturing method that includes a positive electrode forming step, in which the above-mentioned positive electrode forming coating liquid is applied to a current collector to form a composite layer made of a positive electrode composition on the current collector.

[0077] The current collector is not particularly limited, and known current collectors can be used without any particular restrictions. Examples of current collectors include metal foil (metals such as gold, silver, copper, platinum, aluminum, iron, nickel, chromium, manganese, lead, tungsten, and titanium, as well as alloys mainly composed of any one of these). Current collectors are generally provided in the form of foil, but are not limited to this, and perforated foil and mesh-type current collectors can also be used.

[0078] The method for applying the positive electrode forming coating onto the current collector is not particularly limited and may include, for example, die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic coating.

[0079] The amount of coating liquid for forming the positive electrode is not particularly limited and may be adjusted as appropriate so that the thickness of the composite layer is within the desired range.

[0080] The composite layer may be formed by removing at least a portion of the liquid medium from the coating film of the positive electrode forming solution formed on the current collector. The method for removing the liquid medium is not particularly limited, and examples of methods that remove at least a portion of the liquid medium by vaporizing it through heating and / or reduced pressure include standing drying, forced-air drying, hot-air drying, infrared heating, far-infrared heating, etc.

[0081] The method for manufacturing a positive electrode may further include a pressurizing step in which the composite layer formed in the positive electrode formation step and the current collector are pressed in the stacking direction. The pressurizing step can bring the composite layer and the current collector into close contact.

[0082] The pressurizing method used in the pressurizing process is not particularly limited and may include methods such as roll pressing, die pressing, and calendering.

[0083] The thickness of the composite layer in the positive electrode is not particularly limited and may be, for example, 50 μm or more. From the viewpoint of increasing the battery capacity, it is preferably 55 μm or more, more preferably 60 μm or more, and may be 65 μm or more or 70 μm or more. Furthermore, the thickness of the composite layer in the positive electrode may be, for example, 150 μm or less. From the viewpoint of further improving the discharge rate characteristics, it is preferably 140 μm or less, more preferably 130 μm or less, and may be 120 μm or less or 110 μm or less. In other words, the thickness of the composite layer in the positive electrode is, for example, 50 μm to 150 μm, 50 μm to 140 μm, 50 μm to 130 μm, 50 μm to 120 μm, 50 μm to 110 μm, 55 μm to 150 μm, 55 μm to 140 μm, 55 μm to 130 μm, 55 μm to 120 μm, 55 μm to 110 μm, 60 μm to 150 μm, 60 μm to 140 μm, 6 The particle size may be 0 μm to 130 μm, 60 μm to 120 μm, 60 μm to 110 μm, 65 μm to 150 μm, 65 μm to 140 μm, 65 μm to 130 μm, 65 μm to 120 μm, 65 μm to 110 μm, 70 μm to 150 μm, 70 μm to 140 μm, 70 μm to 130 μm, 70 μm to 120 μm, or 70 μm to 110 μm.

[0084] The positive electrode of this embodiment can be suitably used as the positive electrode of a battery, particularly a secondary battery (lithium-ion secondary battery).

[0085] <Battery> The battery of this embodiment (preferably a secondary battery, more preferably a lithium-ion secondary battery) comprises a positive electrode including a composite layer made of a positive electrode composition and a current collector. The positive electrode may be manufactured by the manufacturing method described above.

[0086] In the battery of this embodiment, the components other than the positive electrode may be the same as those of known batteries. The manufacturing method of the battery in this embodiment is also not particularly limited, and may be the same as that of conventionally known battery manufacturing methods, except for the use of the positive electrode described above.

[0087] The battery of this embodiment may, for example, include a positive electrode, a negative electrode, and a separator.

[0088] The separator is not particularly limited, and any separator known as a separator for lithium-ion secondary batteries can be used without any particular restriction. Examples of separators include synthetic resins such as polyethylene and polypropylene. The separator is preferably a porous film because it has good electrolyte retention properties.

[0089] The battery of this embodiment may include an electrode group in which a positive electrode and a negative electrode are stacked or wound together with a separator in between.

[0090] In this embodiment, the battery may have a positive electrode, a negative electrode, and a separator immersed in an electrolyte.

[0091] The electrolyte is not particularly limited and may be, for example, a non-aqueous electrolyte containing a lithium salt. Examples of non-aqueous solvents in a non-aqueous electrolyte containing a lithium salt include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. Examples of lithium salts that can be dissolved in a non-aqueous solvent include lithium hexafluoride phosphate, lithium borotetrafluoride, and lithium trifluoromethanesulfonate. The battery of this embodiment may also use an ion-conducting polymer or the like as the electrolyte.

[0092] The negative electrode in the battery of this embodiment may comprise a negative electrode mixture layer formed by coating a negative electrode mixture containing a negative electrode active material and a binder onto a negative electrode current collector, similar to the negative electrode used in a typical lithium-ion secondary battery, and a negative electrode current collector.

[0093] The battery in this embodiment is not particularly limited in its applications and can be used in a wide range of fields, such as portable AV equipment including digital cameras, video cameras, portable audio players, portable LCD TVs, portable information terminals such as notebook computers, smartphones, and mobile PCs, as well as portable game devices, power tools, electric bicycles, hybrid vehicles, electric vehicles, and power storage systems.

[0094] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above. [Examples]

[0095] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0096] <Manufacturing Example A-1: ​​Manufacturing of Carbon Black A-1> Acetylene, the raw material, is injected at a rate of 12 Nm³ from a nozzle installed in the upstream section of the carbon black reactor (furnace length 6m, furnace diameter 0.65m). 3 / h, toluene 32 kg / h, oxygen 23 Nm³ 3 Carbon black was produced by supplying a certain amount of water per hour and collected in a bag filter installed downstream of the reactor. It was then collected in a tank after passing through a dry cyclone and an iron-removing magnet. Acetylene, toluene, and oxygen were heated to 115°C before being supplied to the reactor to obtain carbon black A-1. The resulting carbon black A-1 had a BET specific surface area of ​​301 m². 2 The average primary particle size was 18 nm, and the crystallite size (Lc) was 16.1 Å.

[0097] <Manufacturing Example A-2: Manufacturing of Carbon Black A-2> The oxygen content for manufacturing example A-1 is 23 Nm³. 3 / h to 22Nm 3 Carbon black A-2 was obtained in the same manner as manufacturing example A-1, except that the rate was changed to / h. The obtained carbon black A-2 had a BET specific surface area of ​​240 m². 2The average primary particle size was 20 nm, and the crystallite size (Lc) was 16.4 Å.

[0098] <Manufacturing Example A-3: Manufacturing of Carbon Black A-3> The oxygen content for manufacturing example A-1 is 23 Nm³. 3 / h to 25Nm 3 Except for changing the rate to / h, carbon black A-3 was obtained in the same manner as manufacturing example A-1. The obtained carbon black A-3 had a BET specific surface area of ​​350 m². 2 The average primary particle size was 17 nm, and the crystallite size (Lc) was 15.6 Å.

[0099] <Manufacturing Example X-1: Manufacturing of Carbon Black X-1> The oxygen content for manufacturing example A-1 is 23 Nm³. 3 / h to 21Nm 3 Carbon black X-1 was obtained in the same manner as in manufacturing example A-1, except that the rate was changed to / h. The obtained carbon black X-1 had a BET specific surface area of ​​178 m². 2 The average primary particle size was 22 nm, and the crystallite size (Lc) was 17.1 Å.

[0100] <Manufacturing Example B-1: Manufacturing of Carbon Black B-1> Acetylene, the raw material, is injected at 32 Nm³ from a nozzle installed in the upstream part of the carbon black reactor (furnace length 6m, furnace diameter 0.65m). 3 / h, toluene 12 kg / h, oxygen 20 Nm³ 3 Carbon black was produced by supplying a certain amount of water per hour and collected in a bag filter installed downstream of the reactor. It was then collected in a tank after passing through a dry cyclone and an iron-removing magnet. Acetylene, toluene, and oxygen were heated to 115°C before being supplied to the reactor to obtain carbon black B-1. The resulting carbon black B-1 had a BET specific surface area of ​​245 m². 2 The average primary particle size was 20 nm, and the crystallite size (Lc) was 19.7 Å.

[0101] <Manufacturing Example B-2: Manufacturing of Carbon Black B-2> The oxygen content for manufacturing example B-1 is 20 Nm³.3 / h to 17Nm 3 Carbon black B-2 was obtained in the same manner as manufacturing example B-1, except that the rate was changed to / h. The obtained carbon black B-2 had a BET specific surface area of ​​141 m². 2 The average primary particle size was 23 nm, and the crystallite size (Lc) was 23.4 Å.

[0102] <Manufacturing Example B-3: Manufacturing of Carbon Black B-3> The oxygen content for manufacturing example B-1 is 20 Nm³. 3 / h to 24Nm 3 Carbon black B-3 was obtained in the same manner as manufacturing example B-1, except that the rate was changed to / h. The obtained carbon black B-3 had a BET specific surface area of ​​370 m². 2 The average primary particle size was 16 nm, and the crystallite size (Lc) was 20.5 Å.

[0103] <Manufacturing Example Y-1: Manufacturing of Carbon Black Y-1> The oxygen content for manufacturing example B-1 is 20 Nm³. 3 / h to 5Nm 3 Carbon black Y-1 was obtained in the same manner as in manufacturing example B-1, except that the rate was changed to / h. The obtained carbon black Y-1 had a BET specific surface area of ​​68 m². 2 The average primary particle size was 35 nm, and the crystallite size (Lc) was 32.4 Å.

[0104] [Table 1]

[0105] [Table 2]

[0106] (Example 1-1) (1) Preparation of the first slurry Carbon black A-1, N-methyl-2-pyrrolidone (hereinafter referred to as NMP) as a liquid medium, and polyvinyl alcohol (Denka Co., Ltd., POVAL B05) as a dispersant were prepared. 1.0% by mass of polyvinyl alcohol and 10.0% by mass of carbon black A-1 were added to 89.0% by mass of NMP and stirred for 120 minutes in a planetary mixer (Primix Co., Ltd., Hibis Disperser Mix 3D-5 type) to prepare a slurry containing carbon black A-1. The obtained slurry was placed into a bead mill (Ashizawa Finetech Co., Ltd., Mugen Flow MGF2-ZA) equipped with zirconia beads (diameter 0.5 mm) and dispersed. After dispersion, the zirconia beads were removed by filtration to prepare a carbon black A-1 slurry (A-1).

[0107] (2) Preparation of the second slurry Carbon black B-1, N-methyl-2-pyrrolidone (hereinafter referred to as NMP) as a liquid medium, and polyvinyl alcohol (Denka Co., Ltd., POVAL B05) as a dispersant were prepared. 1.0% by mass of polyvinyl alcohol and 10.0% by mass of carbon black B-1 were added to 89.0% by mass of NMP and stirred for 120 minutes in a planetary mixer (Primix Co., Ltd., Hibis Dispers Mix 3D-5 type) to prepare a slurry containing carbon black B-1. The obtained slurry was placed into a bead mill (Ashizawa Finetech Co., Ltd., Mugen Flow MGF2-ZA) equipped with zirconia beads (diameter 0.5 mm) and dispersed. After dispersion, the zirconia beads were removed by filtration to prepare a carbon black B-1 slurry (B-1).

[0108] (3) Preparation of coating solution for positive electrode formation Slurry (A-1), Slurry (B-1), Active material with average particle size D 50 We prepared 10 μm lithium nickel-manganese-cobalt oxide (ME6E, manufactured by Beijing Dangsheng Co., Ltd.), a polyvinylidene fluoride NMP solution (L#7208, manufactured by Kureha Corporation) as a binder, and NMP as a liquid medium. The mixture was prepared so that, on a solids-to-solids basis, the active material was 98.25% by mass, carbon black A-1 was 0.6% by mass, carbon black B-1 was 0.15% by mass, and the binder was 1.0% by mass. NMP was added until the mixture reached a viscosity suitable for coating (solids concentration between 65% and 75% by mass), and then mixed until uniform using a rotation-and-revolution type mixer (Awatori Rentaro ARV-310, manufactured by Shinky Co., Ltd.) to obtain a coating solution for cathode formation.

[0109] (4) Manufacturing of the positive electrode The prepared positive electrode forming coating solution was deposited onto one side of a 15 μm thick aluminum foil (manufactured by UACJ) using an applicator to create a laminate. The laminate was then left to stand in a dryer and pre-dried at 105°C for 1 hour to completely remove NMP. Next, the dried laminate was pressed in a roll press at a linear pressure of 200 kg / cm to adjust the total thickness of the laminate to 80 μm. Finally, it was vacuum dried at 170°C for 3 hours to completely remove residual moisture, obtaining a positive electrode comprising a current collector and an asphalt layer.

[0110] (5) Manufacturing of the negative electrode Pure water (manufactured by Kanto Chemical Co., Ltd.) was prepared as the solvent, artificial graphite (manufactured by Hitachi Chemical Co., Ltd., "MAG-D") as the negative electrode active material, styrene-butadiene rubber (manufactured by Nippon Zeon Co., Ltd., "BM-400B", hereinafter referred to as SBR) as the binder, and carboxymethylcellulose (manufactured by Daicel Corporation, "D2200", hereinafter referred to as CMC) as the dispersant. Next, CMC was weighed to 1% by mass in solid content and artificial graphite to 97% by mass in solid content and mixed. Pure water was added to this mixture and mixed until homogeneous using a rotation-and-revolution type mixer (manufactured by Thinky Co., Ltd., Awatori Rentaro ARV-310) to obtain a mixture. Next, SBR was weighed to 2% by mass in solid content and added to the obtained mixture and mixed until homogeneous using a rotation-and-revolution type mixer (manufactured by Thinky Co., Ltd., Awatori Rentaro ARV-310) to obtain a coating liquid for negative electrode formation. Next, a coating liquid for forming the negative electrode was deposited onto a 10 μm thick copper foil (manufactured by UACJ) using an applicator to create a laminate, which was then left to stand in a dryer and pre-dried at 60°C for 1 hour. Next, it was pressed with a roll press at a linear pressure of 50 kg / cm to adjust the total thickness of the laminate to 60 μm. Finally, it was vacuum-dried at 120°C for 3 hours to completely remove residual moisture, obtaining a negative electrode comprising a current collector and an asphalt layer.

[0111] (6) Battery manufacturing In a dry room controlled to a dew point of -50°C or lower, the fabricated positive electrode was processed to 40 x 40 mm and the fabricated negative electrode to 44 x 44 mm. Then, an aluminum tab was welded to the positive electrode and a nickel tab to the negative electrode. The composite coating surfaces of the positive and negative electrodes were positioned facing each other in the center, and a 45 x 45 mm polyolefin microporous membrane was placed between the positive and negative electrodes. Next, a sheet-like outer covering cut and processed to a 70 x 140 mm square was folded in half along the center of its long side. Then, the outer covering was positioned so that the aluminum tab for the positive electrode and the nickel tab for the negative electrode were exposed to the outside of the outer covering, and the laminate of the positive electrode / polyolefin microporous membrane / negative electrode was sandwiched between the folded outer covering. Next, using a heat sealer, two sides of the outer casing, including the side where the aluminum tab for the positive electrode and the nickel tab for the negative electrode are exposed, were heat-fused together. Then, 2 g of electrolyte (a solution containing ethylene carbonate / diethyl carbonate = 1 / 2 (volume ratio) and 1 M LiPF6 solution, manufactured by Kishida Chemical Co., Ltd.) was poured into the unfused side to allow the electrolyte to thoroughly permeate the positive electrode, negative electrode, and polyolefin microporous membrane. Finally, the remaining side of the outer casing was heat-fused together using a vacuum heat sealer while reducing the internal pressure to obtain a lithium-ion secondary battery.

[0112] (7) Evaluation (7-1) Plate resistance The positive electrode prepared in (4) above was cut into a 14 mm diameter disc shape and sandwiched between two SUS304 flat electrode plates. The AC impedance was measured using an electrochemical measurement system (Solartron Corporation, Function Generator 1260 and Potentiometer Galvanostat 1287) at an amplitude voltage of 10 mV and a frequency range of 1 Hz to 100 kHz. The resistance value obtained was multiplied by the area of ​​the cut-out disc to obtain the plate resistance. (7-2) Discharge rate characteristics (rate capacity retention rate) The batteries prepared in (6) above were charged at 25°C with a constant current and voltage limit of 4.3V and 0.2C, and then discharged to 3.0V with a constant current of 0.2C. Next, they were recharged again with a constant current and voltage limit of 4.3V and 0.2C, and then discharged to 3.0V with a constant current of 0.2C, and the discharge capacity at this time was measured. Subsequently, the recharge conditions were set to constant current and voltage limit of 4.3V and 0.2C, while the discharge current was gradually changed to 0.5C, 1C, 2C, and 3C. The recharge and discharge cycles were repeated, and the discharge capacity for each discharge current was measured. As an indicator of the battery's discharge rate characteristics, the capacity retention rate at 3C discharge compared to 0.2C discharge was calculated as the rate capacity retention rate.

[0113] (Examples 1-2) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black B-2 was used instead of carbon black B-1, and the composition of the coating solution for forming the positive electrode was adjusted so that the active material was 97.7% by mass, carbon black A-1 was 0.8% by mass, carbon black B-2 was 0.2% by mass, and the binder was 1.3% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 3.

[0114] (Examples 1-3) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black B-3 was used instead of carbon black B-1, and the composition of the coating solution for forming the positive electrode was adjusted so that the active material was 98.25% by mass, carbon black A-1 was 0.6% by mass, carbon black B-3 was 0.15% by mass, and the binder was 1.0% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 3.

[0115] (Comparative Example 1-1) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black Y-1 was used instead of carbon black B-1, and the composition of the coating solution for forming the positive electrode was prepared so that, on a solid-state basis, the active material was 97.7% by mass, carbon black A-1 was 0.8% by mass, carbon black Y-1 was 0.2% by mass, and the binder was 1.3% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 3.

[0116] (Comparative Example 1-2) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black A-3 was used instead of carbon black B-1, and the composition of the coating solution for forming the positive electrode was adjusted so that the active material was 98.25% by mass, carbon black A-1 was 0.6% by mass, carbon black A-3 was 0.15% by mass, and the binder was 1.0% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 3.

[0117] The evaluation results for Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2 are shown in Table 3. In the table, CB1 and CB2 indicate the types of carbon black, C2 / C1 indicates the ratio (mass ratio) of the content of CB2 to the content of CB1, and C1+C2 indicates the total amount of CB1 and CB2 (based on the total amount of the positive electrode composition (solid content of the coating liquid for positive electrode formation)).

[0118] [Table 3]

[0119] (Example 2-1) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black A-2 was used instead of carbon black A-1, and the composition of the coating solution for forming the positive electrode was adjusted so that the active material was 97.7% by mass, carbon black A-2 was 0.8% by mass, carbon black B-1 was 0.2% by mass, and the binder was 1.3% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 4.

[0120] (Example 2-2) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black A-3 was used instead of carbon black A-1, and the composition of the coating solution for forming the positive electrode was adjusted so that the active material was 98.25% by mass, carbon black A-3 was 0.6% by mass, carbon black B-1 was 0.15% by mass, and the binder was 1.0% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 4.

[0121] (Comparative Example 2-1) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black X-1 was used instead of carbon black A-1, and the composition of the coating solution for positive electrode formation was adjusted so that the active material was 97.7% by mass, carbon black X-1 was 0.8% by mass, carbon black B-1 was 0.2% by mass, and the binder was 1.3% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 4.

[0122] [Table 4]

[0123] (Example 3-1) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that the composition of the coating solution for forming the positive electrode was prepared so that, on a solid-state basis, the active material was 98.25% by mass, carbon black A-1 was 0.675% by mass, carbon black B-1 was 0.075% by mass, and the binder was 1.0% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 5.

[0124] (Example 3-2) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that the composition of the coating solution for forming the positive electrode was prepared so that, on a solid-state basis, the active material was 98.25% by mass, carbon black A-1 was 0.45% by mass, carbon black B-1 was 0.3% by mass, and the binder was 1.0% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 5.

[0125] (Comparative Example 3-1) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that the composition of the coating solution for forming the positive electrode was prepared so that, on a solid-state basis, the active material was 98.25% by mass, carbon black A-1 was 0.375% by mass, carbon black B-1 was 0.375% by mass, and the binder was 1.0% by mass. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 5.

[0126] [Table 5]

[0127] (Comparative Example 4-1) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that carbon black B-1 was not used, and the composition of the coating solution for positive electrode formation was prepared so that the active material was 98.25% by mass, carbon black A-1 was 0.75% by mass, and the binder was 1.0% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 6.

[0128] (Comparative Example 4-2) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that only carbon black A-2 was used as the carbon black, and the composition of the coating solution for forming the positive electrode was prepared so that the active material was 97.7% by mass, carbon black A-2 was 1.0% by mass, and the binder was 1.3% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 6.

[0129] (Comparative Example 4-3) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that only carbon black A-3 was used as the carbon black, and the composition of the coating solution for forming the positive electrode was prepared so that the active material was 98.25% by mass, carbon black A-3 was 0.75% by mass, and the binder was 1.0% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 6.

[0130] (Comparative Example 4-4) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that only carbon black X-1 was used as the carbon black, and the composition of the coating solution for forming the positive electrode was prepared so that the active material was 97.7% by mass, carbon black X-1 was 1.0% by mass, and the binder was 1.3% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 6.

[0131] (Comparative Example 4-5) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that only carbon black B-1 was used as the carbon black, and the composition of the coating solution for forming the positive electrode was prepared so that the active material was 98.25% by mass, carbon black B-1 was 0.75% by mass, and the binder was 1.0% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 7.

[0132] (Comparative Example 4-6) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that only carbon black B-2 was used as the carbon black, and the composition of the coating solution for forming the positive electrode was prepared so that the active material was 97.7% by mass, carbon black B-2 was 1.0% by mass, and the binder was 1.3% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 7.

[0133] (Comparative Example 4-7) The positive electrode and battery were manufactured in the same manner as in Example 1-1, except that only carbon black B-3 was used as the carbon black, and the composition of the coating solution for forming the positive electrode was prepared so that the active material was 98.25% by mass, carbon black B-3 was 0.75% by mass, and the binder was 1.0% by mass, on a solid ratio basis. The obtained positive electrode and battery were evaluated using the same method as in Example 1-1. The results are shown in Table 7.

[0134] [Table 6]

[0135] [Table 7]

[0136] As shown in Tables 3-7, in the embodiments corresponding to the above-described embodiments, the plate resistance was small, at 200 Ω·cm² or less, and the rate capacity retention rate was high, at 90% or more. From these results, it was confirmed that according to the above-described embodiments, a battery with low internal resistance and excellent discharge rate characteristics can be realized.

Claims

1. It contains a first carbon black, a second carbon black, and an active material. The aforementioned first carbon black is 200 m ２ Having a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 14 Å or more and 17 Å or less, The aforementioned second carbon black is 100 m ２ It has a BET specific surface area of ​​19 Å or more / g, and a crystallite size (Lc) of 19 Å or more and 25 Å or less. The content C of the first carbon black １ The content of the second carbon black relative to C ２ ratio C ２ / C １ However, it is between 0.1 and 0.

45. Cathode composition.

2. The BET specific surface area of ​​the first carbon black is 200 m². ２ / g or more 400m ２ / g or less, The BET specific surface area of the second carbon black is 100 m ２ / g or more and 400 m ２ / g or less, The positive electrode composition according to claim 1.

3. A positive electrode comprising a composite layer made of the positive electrode composition according to claim 1 or 2.

4. A battery comprising the positive electrode described in claim 3.

5. It contains a first carbon black, a second carbon black, an active material, and a liquid medium. The aforementioned first carbon black is 200 m ２ Having a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 14 Å or more and 17 Å or less, The aforementioned second carbon black is 100 m ２ It has a BET specific surface area of ​​19 Å or more / g, and a crystallite size (Lc) of 19 Å or more and 25 Å or less. The content C of the first carbon black １ The content of the second carbon black relative to C ２ ratio C ２ / C １ However, it is between 0.1 and 0.

45. Coating liquid for positive electrode formation.

6. A slurry preparation step involves preparing a first slurry containing a first carbon black and a first liquid medium, and a second slurry containing a second carbon black and a second liquid medium. A mixing step of mixing the first slurry, the second slurry, and the active material to obtain a coating liquid for forming a positive electrode, Includes, The aforementioned first carbon black is 200 m ２ Having a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 14 Å or more and 17 Å or less, The aforementioned second carbon black is 100 m ２ It has a BET specific surface area of ​​19 Å or more / g, and a crystallite size (Lc) of 19 Å or more and 25 Å or less. The content of the first carbon black in the coating solution for forming the positive electrode is C １ The content of the second carbon black relative to C ２ ratio C ２ / C １ However, it is between 0.1 and 0.

45. A method for manufacturing a coating solution for forming a positive electrode.

7. A method for manufacturing a positive electrode including a current collector and an asphalt layer, A coating solution preparation step is performed to prepare a coating solution for positive electrode formation containing a first carbon black, a second carbon black, an active material, and a liquid medium. A positive electrode forming step involves applying the positive electrode forming liquid onto the current collector to form the composite material layer on the current collector, Includes, The aforementioned first carbon black is 200 m ２ Having a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 14 Å or more and 17 Å or less, The aforementioned second carbon black is 100 m ２ It has a BET specific surface area of ​​19 Å or more / g, and a crystallite size (Lc) of 19 Å or more and 25 Å or less. The content of the first carbon black in the coating solution for forming the positive electrode is C １ The content of the second carbon black relative to C ２ ratio C ２ / C １ However, it is between 0.1 and 0.

45. A method for manufacturing a positive electrode.

8. The manufacturing method according to claim 7, wherein the coating preparation step is a step of obtaining the coating liquid for forming the positive electrode by the manufacturing method described in claim 6.

9. A method for manufacturing a battery comprising a positive electrode including a current collector and an asphalt layer, A coating solution preparation step is performed to prepare a coating solution for positive electrode formation containing a first carbon black, a second carbon black, an active material, and a liquid medium. A positive electrode forming step involves applying the positive electrode forming liquid onto the current collector to form the composite material layer on the current collector, Includes, The aforementioned first carbon black is 200 m ２ Having a BET specific surface area of ​​1 / g or more, and a crystallite size (Lc) of 14 Å or more and 17 Å or less, The aforementioned second carbon black is 100 m ２ It has a BET specific surface area of ​​19 Å or more / g, and a crystallite size (Lc) of 19 Å or more and 25 Å or less. The content of the first carbon black in the coating solution for forming the positive electrode is C １ The content of the second carbon black relative to C ２ ratio C ２ / C １ However, it is between 0.1 and 0.

45. Battery manufacturing method.

10. The manufacturing method according to claim 9, wherein the coating preparation step is a step of obtaining the coating liquid for forming the positive electrode by the manufacturing method described in claim 6.

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