WO2006082708A1

WO2006082708A1 - Secondary cell positive electrode, manufacturing method thereof, and secondary cell

Info

Publication number: WO2006082708A1
Application number: PCT/JP2006/300695
Authority: WO
Inventors: Jiro Iriyama; Kentaro Nakahara; Shigeyuki Iwasa; Masahiro Suguro; Masaharu Satoh
Original assignee: Nec Corporation
Priority date: 2005-02-04
Filing date: 2006-01-19
Publication date: 2006-08-10
Also published as: JPWO2006082708A1

Abstract

It is possible to provide a secondary cell positive electrode having a small electric resistance and a large mechanical strength and a secondary cell capable of performing charge/discharge using a large current and having a large capacity and an excellent storage characteristic. The secondary cell positive electrode has an active material layer containing at least a radical compound and carbon fiber having an average value of inter-layer distance d002 of the graphite structure in a range from 0.335 nm to 0.340 nm. The carbon fiber having such an inter-layer distance has a tensile modulus in a range from 200 GPa to 800 GPa and preferably has a volume resistivity in a range from 200 μΩ•cm to 2000 μΩ•cm. The carbon fiber is preferably a vapor-epitaxial carbon fiber or a carbon fiber formed by meso-phase pitch as a precursor which has been graphitized.

Description

Specification

Positive electrode for secondary battery, method for producing the same, and secondary battery

Technical field

TECHNICAL FIELD [0001] The present invention relates to a positive electrode for a secondary battery, a method for producing the same, and a secondary battery. More specifically, in a positive electrode for a secondary battery containing a radical compound, the electrical resistance of the positive electrode is reduced and the machine The present invention relates to a positive electrode for a secondary battery with improved mechanical strength, a method for producing the same, and a secondary battery.

Background art

[0002] Along with the rapid market expansion of notebook computers, mobile phones, electric vehicles and the like !, storage devices used in these devices are required to have high capacity, high energy density, and high stability. In order to satisfy these requirements, secondary batteries using various materials have been proposed as power storage devices.

[0003] For example, in Patent Document 1 below, as a secondary battery having a high energy density and a high capacity and excellent stability, a nitroxyl radical compound, an oxy radical compound, Lithium secondary batteries using radical compounds such as oxy radical compounds and polymer compounds having an aminotriazine structure have been proposed.

[0004] Further, in Patent Document 2 below, as a secondary battery that can be used at a large current with a high energy density, a -troxyl cation partial structure is formed in an acid state and a -troxyl radical portion is formed in a reduced state. A lithium secondary battery has been proposed in which a structure-troxyl compound is contained in the active material layer of the positive electrode, and the electron transfer reaction between the acid state and the reduced state is used as the positive electrode reaction. .

[0005] In Patent Document 3 below, as a secondary battery having a high energy density and a large capacity and stable, at least a positive electrode, a negative electrode, and an electrolyte are used as constituent elements, and at least an electrochemical oxidation reaction and a reduction reaction are performed. A lithium secondary battery having particles containing an organic compound that generates a radical compound in one process as an active material, and in which the active material layer for the positive electrode is formed of a composite having at least two compositional regions. Secondary batteries have been proposed.

[0006] Further, Patent Document 4 below discloses a secondary battery that improves the conductivity and mechanical strength of an electrode. As an active material layer containing a disulfide group, the S—S bond of the disulfide group is cleaved by electrochemical reduction and regenerated by electrochemical oxidation. The lithium secondary battery used has been proposed. In this lithium secondary battery, carbon nanotubes are dispersed in a conductive matrix. Patent Document 1: Japanese Patent Laid-Open No. 2002-151084

Patent Document 2: JP-A-2002-304996

Patent Document 3: Japanese Patent Laid-Open No. 2002-298850

Patent Document 4: Japanese Patent Laid-Open No. 11-329414

Disclosure of the invention

Problems to be solved by the invention

[0007] However, in the lithium secondary batteries described in Patent Documents 1 to 3, the radical compound contained in the active material layer has low conductivity, and therefore the electrode resistance of the active material layer is high. There is a problem of becoming. In addition, since the active material layer has a relatively low mechanical strength, the active material layer may be cracked, and as a result, the electrode resistance of the active material layer may be increased. High electrical resistance! A lithium secondary battery having an active material layer is prone to a problem that the capacity of the battery is insufficient particularly when charging / discharging with a large current.

[0008] Furthermore, since the lithium secondary batteries described in Patent Documents 1 to 3 have low mechanical strength, the current collector active material layer may fall off during storage without charge / discharge of the lithium secondary battery. Therefore, the charge / discharge capacity of the active material layer during storage (referred to as storage characteristics) may be reduced.

On the other hand, in the lithium secondary battery described in Patent Document 4, since the regeneration efficiency of the cleaved S—S bond is small during the electrochemical reaction during charge and discharge, it is described in Patent Documents 1 to 3. Compared to a lithium secondary battery using an active material layer of the above radical compound, stability during charging and discharging is poor. For this reason, the lithium secondary battery described in Patent Document 4 has a problem that it is difficult to use as a large-capacity secondary battery capable of charging and discharging using a large current, and there is a need for a solution to the problem. It was.

[0010] The present invention has been made to solve the above-mentioned problems, and its first object is to The object is to provide a positive electrode for a secondary battery with low electrode resistance and high mechanical strength, and a method for producing the same. A second object of the present invention is to provide a secondary battery having a large capacity and excellent storage characteristics that can be charged and discharged using a large current.

Means for solving the problem

A positive electrode for a secondary battery according to the present invention for solving the above-described problems is a carbon fiber having an average value of a radical compound and an interlayer distance d of a graphite structure in a range of 0.335 nm or more and 0.340 nm or less.

002

And an active material layer including at least a fiber.

[0012] According to the present invention, since the radical compound and the carbon fiber are included, it is considered that the interface resistance between the two is remarkably reduced, and the conductivity of the active material layer containing them can be increased. As a result, a positive electrode for a secondary battery having a low electric resistance can be configured. Also, the average value of the interlayer distance d of the graphite structure of the carbon fiber contained in the active material layer is 0.335 nm or more.

002

Since the carbon fiber within the range of 340 nm or less has high mechanical strength, the mechanical strength of the active material layer containing such carbon fiber can be increased. As a result, a positive electrode for a secondary battery having an active material layer with high conductivity that does not crack or fall off can be configured. Moreover, since the active material layer of the positive electrode for secondary battery of the present invention contains a radical compound, a secondary battery using the positive electrode for secondary battery can have a large capacity.

In the positive electrode for a secondary battery of the present invention, it is preferable that the tensile elastic modulus of the carbon fiber is in a range of 200 GPa to 800 GPa.

[0014] The average value of the interlayer distance d of the above-mentioned graphite structure is in the range of 0.335 nm or more and 0.340 nm or less.

002

The carbon fiber in the enclosure usually has a large value with a tensile elastic modulus in the range of 200 GPa to 800 GPa. According to the present invention, it is possible to increase the mechanical strength of the active material layer containing such carbon fibers and the positive electrode for a secondary battery including the active material layer.

In the positive electrode for a secondary battery of the present invention, it is preferable that the volume resistivity of the carbon fiber is in a range of 200 μΩ · cm to 2000 Ω′cm.

According to the present invention, since the volume resistivity of the carbon fibers contained in the active material layer is in the range of 200 μΩ-cm to 2000 / ζ Ω′cm, the active material layer containing such carbon fibers. The conductivity becomes higher. As a result, the electrode resistance of the positive electrode for a secondary battery provided with such an active material layer. The resistance can be lowered.

[0017] In the positive electrode for a secondary battery of the present invention, the carbon fiber is preferably a vapor-grown carbon fiber.

[0018] According to this invention, since the carbon fiber is a vapor-grown carbon fiber having excellent dispersibility, the dispersibility of the carbon fiber in the radical compound when producing the active material layer can be improved. wear. As a result, an active material layer having uniform characteristics in each part and a secondary battery positive electrode including the active material layer can be easily obtained.

[0019] In the positive electrode for a secondary battery of the present invention, it is preferable that the carbon fiber is a graphitized carbon fiber having a mesophase pitch as a precursor. Mesophase pitch is a polycyclic aromatic compound contained in coal tar or petroleum pitch that undergoes a polycondensation reaction by heating or the like and has uniform optical anisotropy. By firing carbon fibers having a mesophase pitch as a precursor at a temperature of 2600 ° C to 3000 ° C, carbon fibers having an extremely high graphitization degree can be obtained. Since carbon fiber has such a high degree of graphite and excellent electrical conductivity and mechanical strength, when it is used for a positive electrode, a positive electrode for a secondary battery with low resistance and excellent mechanical strength can be obtained. Can be easily obtained.

[0020] In the positive electrode for a secondary battery of the present invention, the carbon fiber content in the active material layer is preferably in the range of 10 wt% to 50 wt%.

[0021] According to this invention, since the carbon fiber content in the active material layer is 10% by weight or more, the mechanical strength of the active material layer can be increased. The mechanical strength of the positive electrode for the secondary battery can be increased. In addition, since the content ratio of the carbon fiber in the active material layer is 50% by weight or less, the content ratio of the radical compound in the active material layer can be relatively increased, and as a result, the secondary content of the present invention can be increased. A secondary battery using a positive electrode for a battery can have a large capacity.

[0022] The positive electrode for a secondary battery of the present invention preferably contains at least one of the radical compound power nitroxyl radical compound, oxy radical compound and nitrogen radical compound, in particular, Among the troxyl radical compounds, poly (4-methacryloyloxy 1, 2, 6, 6-tetramethylpiperidine 1-1-oxyl), poly (4-ataryloxyoxy 2, 2, 6, 6-tetramethylpiperidine) 1-oxyl) or poly (4-bi) -Luoxy-1,2,6,6-tetramethylpiperidine1-1-oxyl).

[0023] The method for producing a positive electrode for a secondary battery of the present invention for solving the above-mentioned problem is a method for producing a positive electrode for a secondary battery having an active material layer containing at least a radical compound and carbon fiber. In the solvent containing the radical compound, the average value of the interlayer distance d of the graphite structure is

002

It has a step of dispersing the carbon fiber in the range of not less than 0.335 nm and not more than 0.340 nm.

[0024] According to the present invention, it is possible to produce a positive electrode for a secondary battery with low electrical resistance and high mechanical strength.

[0025] In the method for producing a positive electrode for a secondary battery of the present invention, it is preferable to disperse the carbon fiber in the active material layer so that the carbon fiber content is in the range of 10 wt% to 50 wt%. That's right.

[0026] According to this invention, since the carbon fiber content in the active material layer is dispersed so as to be within the above range, an active material layer in which the electrical resistance and mechanical properties are uniform in each part can be formed. As a result, a positive electrode for a secondary battery having a low electrical resistance and a high mechanical strength can be produced.

[0027] The secondary battery of the present invention for solving the above problems is a secondary battery comprising at least a positive electrode, a negative electrode, and an electrolyte solution, wherein the positive electrode is the positive electrode for a secondary battery according to the present invention described above. It is characterized by being.

[0028] According to this invention, since the positive electrode for a secondary battery including a radical compound and having an active material layer having a low electrode resistance and a large mechanical strength is provided, a large current V is charged and discharged. Thus, a secondary battery having a large capacity and excellent storage characteristics can be obtained.

The invention's effect

[0029] As described above, according to the positive electrode for a secondary battery of the present invention, since the conductivity of the active material layer is increased and neither cracking nor dropping occurs, the electrical resistance is low and the mechanical strength is high. A positive electrode for a secondary battery can be configured. Moreover, since the active material layer of the positive electrode for secondary battery of the present invention contains a radical compound, a secondary battery using the positive electrode for secondary battery can have a large capacity. [0030] Further, according to the method for producing a positive electrode for a secondary battery of the present invention, an active material layer having uniform electric resistance and mechanical characteristics in each part can be formed, so that the electric resistance is low and the mechanical strength is large. A positive electrode for a secondary battery can be manufactured.

[0031] Further, according to the secondary battery of the present invention, since the positive electrode for a secondary battery having high mechanical strength is provided, the electrode resistance is increased due to cracks in the active material layer, or the active material layer is dropped off. It is possible to suppress deterioration of storage characteristics. In addition, since the secondary battery of the present invention includes a positive electrode for a secondary battery that includes a radical compound and has an active material layer that has low, electrode resistance, and high mechanical strength, charging and discharging using a large current is possible. A secondary battery having a large capacity and excellent storage characteristics can be obtained.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view showing an example of a secondary battery of the present invention.

Explanation of symbols

[0033] 1 Positive electrode active material layer

2 Negative electrode active material layer

3 Positive current collector

4 Negative electrode current collector

5 Electrolyte

6 Positive electrode outer can

7 Negative electrode outer can

8 Insulating packing

10 Lithium secondary battery

11 Positive electrode

12 Negative electrode

13 Separator

BEST MODE FOR CARRYING OUT THE INVENTION

[0034] Hereinafter, the positive electrode for a secondary battery of the present invention, a method for producing the same, and the secondary battery will be described.

[0035] (Positive electrode for secondary battery) The positive electrode for secondary battery of the present invention is an average of the radical compound and the interlayer distance d of the graphite structure

002 has an active material layer containing at least carbon fibers within a range of 0.335 nm or more and 0.340 nm or less. Such an active material layer is usually formed on a current collector and forms a part of a positive electrode for a secondary battery. It should be noted that the current collector is preferably a general material and shape that is not particularly limited. Examples of the current collector material include various materials such as aluminum, nickel, aluminum alloy, nickel alloy, and carbon. Examples of the shape thereof include foil, flat plate, and mesh. The one that also has shape power can be mentioned.

[0036] (Radical compound)

A radical compound is a compound which comprises an active material layer as an active material. The radical compound, free radical having an unpaired electron (i.e., radical) is a compound having, Rajikarui匕合composing this onset Ming, spin concentration force S l0 ²¹ radical density in the high instrument equilibrium A state where spinZg or higher continues for 1 second or longer. In addition, the charged state of the radical compound constituting the present invention is preferably electrically neutral from the viewpoint of easy charge / discharge reaction.

[0037] Since radicals have spin nuclear momentum, the radical density (density of unpaired electrons) is equal to the spin concentration. Here, the spin concentration is a value obtained by, for example, the following method from the absorption area intensity of an electron spin resonance spectrum (hereinafter referred to as ESR spectrum). First, the sample to be used for measuring the ESR ^ vector is ground and ground with a mortar. By this treatment, the skin effect (a phenomenon in which the microwave does not pass to the inside) can be pulverized into particles having a size that can be ignored. A certain amount of the crushed sample is filled into a quartz glass capillary with an inner diameter of 2 mm or less, preferably 1 to 0.5 mm, 1. Deaerated to 33 to 0.67 kPa (10 to 5 mmHg) or less, and sealed. ^ Measure the vector. The ESR ^ vector can be measured using, for example, the EOL-JES-FR30 ESR ^ spectrometer. The spin concentration can be calculated by integrating the obtained ESR signal twice and comparing it with the calibration curve. In the present invention, any measuring instrument and measurement condition are applicable as long as the spin concentration can be measured correctly.

[0038] Examples of the radical compound include polymer-troxyl radical compound, polymer oxydica Examples thereof include a Louis compound and a polymer hydrazyl radical compound. In the present invention

As the active material, at least one or two or more of these radical compounds can be used.

[0039] Among the above radical compounds, a polymer-troxyl radical compound, that is, a polymer having -toxyl is most preferably used. Nitroxyl is particularly preferable as an active material because of its extremely high stability due to nonlocality of radicals. Typical examples of the polymer-troxyl radical compound include A-1 to A-8 of the following chemical structural formulas. In these polymer-troxyl radical compounds, each radical is further stabilized by steric hindrance due to a bulky substituent in the vicinity and a resonance structure. In addition, the polymer main chain includes poly (meth) acrylic acid, polyalkyl (meth) acrylates, polybutyl ethers, poly (meth) acrylamides, polymer strength, high oxidation resistance and reduction resistance, and electrochemical properties. Is particularly preferable. In the formula, R to R are

15 Each independently represents an alkyl group, and as the alkyl group, a methyl group, an ethyl group, or the like is used. In particular, a methyl group is preferably used in view of electrochemical stability and capacity.

[0040] [Chemical 1]

The A-7 A-8 polymer oxyradical compound is a polymer having an oxyradical, and typical examples thereof include A-9 to A-11 of the following chemical structural formula. The high molecular hydrazyl radical compound is a polymer having a hydrazyl radical, and examples thereof include A-12 and A-13 of the following chemical structural formula. In the formula, R to R are respectively

16 independently represents an alkyl group, and as the alkyl group, a methyl group, an ethyl group, or the like is used. Particularly, a methyl group is preferably used from the viewpoint of electrochemical stability and capacity. [0042] [Chemical 2]

A—12 A—1 3

[0043] (Carbon fiber)

The carbon fiber of the present invention has a graphite structure interlayer distance d

The average value of 002 is 0.335 nm or more 0.34

It is within the range of Onm or less. In the present invention, since such carbon fibers are contained in the active material layer, it is considered that the interfacial resistance with the above-mentioned radical compound is remarkably lowered, and the conductivity of the active material layer containing these may be increased. it can.

In the present invention, the average value of the interlayer distance d of the carbon fiber graphite structure is, for example, an X-ray rotation

002

It can be obtained from time to time. Specifically, in the graphite structure of carbon fiber, it can be represented by the analysis result of the X-ray diffraction peak that appears as the average value of the inter-layer distance d.

002

Since the carbon fiber having an interlayer distance within the above range has a large mechanical strength (for example, tensile elastic modulus), the mechanical strength of the active material layer can be increased. The result is an active material layer that does not fall off if cracked, and has a highly conductive active material layer. Can be configured.

[0045] When the average value of the interlayer distance d of the graphite structure of the carbon fiber is larger than 0.340 nm, the machine

002

The mechanical strength of the active material layer containing carbon fibers may be insufficient due to a lack of mechanical strength (for example, tensile modulus). On the other hand, the interlayer distance d of an ideal graphite structure

002 is 0.335 nm, and there is no carbon fiber with an interlayer distance less than 0.335 nm.

[0046] The tensile elastic modulus of the carbon fiber is preferably in the range of 200 GPa to 800 GPa. The average value of the interlayer distance d of the above graphite structure is 0.335 nm or more and 0.340 nm or less.

002

Carbon fibers in the range of usually have a large value of tensile elastic modulus in the range of 200 GPa to 800 GPa. Such an active material layer containing carbon fibers can increase the mechanical strength of the positive electrode for a secondary battery having a high mechanical strength. If the tensile modulus of the carbon fiber is less than 200 GPa, the mechanical strength of the active material layer containing the carbon fiber may be insufficient because the mechanical strength is insufficient. On the other hand, the upper limit of the tensile modulus of carbon fiber was set to 800 GPa from the viewpoint of carbon fiber production cost. The definition and measurement method of the tensile modulus of carbon fiber are based on JIS R7601-1986 (carbon fiber test method).

[0047] The active material layer containing carbon fiber described above has a feature that mechanical strength is increased. In the present invention, the volume resistivity of the carbon fiber is 200 Ω'cm or more and 2000 Ω'cm or less. It is preferable to be within the range. When carbon fibers having a volume resistivity in such a range are included in the active material layer, the conductivity of the active material layer is increased. As a result, the electrode resistance of the positive electrode for secondary batteries provided with the active material layer can be lowered. The lower limit of the volume resistivity of the carbon fiber was set to 200 μΩ ′ cm from the viewpoint of the production cost of the carbon fiber. On the other hand, if the volume resistivity of the carbon fiber exceeds 2000 Ω ′ cm, the electrode resistance of the positive electrode may not be sufficiently lowered. The definition and measurement method of the volume resistivity of carbon fiber are also in accordance with JIS R7601-1986 (carbon fiber test method), similar to the above-mentioned tensile elastic modulus.

[0048] The types of carbon fibers are classified according to the production method, but the carbon fibers applicable to the present invention are not particularly limited, and various types of carbon fibers that satisfy the above characteristics can be used. For example, PAN carbon fibers obtained by carbonizing polyacryl-tolyl (PolyAcryloNitrile: PAN) precursors, pitches obtained when refining petroleum and coal are used as precursors Pitch carbon fiber obtained by carbonizing and graphitizing this, and vapor grown carbon fiber (Vapor-) obtained by growing fiber on a substrate in a reaction furnace using hydrocarbon vapor. Grown Carbon F¾ers (VGCF), carbon nanotubes (CNT) obtained by an arc discharge method using an arc discharge between graphite electrodes, and the like can be used. These may be used alone or in combination of two or more.

[0049] When forming an active material layer using such carbon fibers, a process of dispersing carbon fibers in a radical compound in a solvent is performed. In particular, vapor-grown carbon fibers (VGCF) It is most preferably used for its excellent dispersibility.

[0050] In addition, mesophase pitch carbon fiber obtained by carbonizing and graphitizing mesophase pitch having optical anisotropy among pitches obtained when refining petroleum or coal is used as a precursor. Is particularly preferred because of its excellent electrical conductivity and mechanical strength. In addition, it is preferable to use a precursor in which boron in the range of 10 to 50 ppm is added to the mesophase pitch for easier progress of graphite.

[0051] The size of the carbon fiber is not particularly limited, but in the present invention, the average length is usually from 10 µm to 200 µm and the average diameter is from 0.4 µm to 4 µm. A fibrous material is preferably used for the reason of good dispersibility. Here, the average length and the average diameter are the average length and the average diameter when 1000 or more carbon fibers are observed with an electron microscope or the like.

[0052] (Active material layer)

The active material layer is formed on the current collector to constitute the positive electrode for a secondary battery of the present invention, and includes at least the radical compound and the carbon fiber.

[0053] It is preferable that the active material layer contains carbon fiber in a proportion within the range of 10 wt% to 50 wt%. By including carbon fiber in this ratio in the active material layer, the mechanical strength of the active material layer can be increased and the electrical resistance can be decreased. If the carbon fiber content in the active material layer is less than 10% by weight, the active material layer may be cracked or dropped, resulting in insufficient mechanical strength. On the other hand, if the carbon fiber content in the active material layer exceeds 50% by weight, the proportion of the radical compound that functions as the active material is relatively lowered. The capacity | capacitance of the secondary battery comprised with the pole will fall.

[0054] In the active material layer constituting the positive electrode for a secondary battery according to the present invention, there is a phenomenon that the conductivity is remarkably increased when the carbon fiber is contained. This is because the interface barrier between the radical compound and the carbon fiber is low because the energy barrier during charge transfer between the radical compound and the carbon constituting the carbon fiber is almost the same. It is believed that there is.

[0055] Such a phenomenon is a remarkable effect obtained by a combination of a radical compound and carbon fiber, and the present inventor has used other conductors such as gold, silver, copper, etc. instead of carbon fiber. In some cases, it has been confirmed that the conductivity of the active material layer does not increase.

[0056] Note that the active material layer described in Patent Document 4 (the active material layer in which carbon nanotubes are dispersed in a conductive matrix containing a disulfide group) has conductivity equivalent to that of carbon nanotubes. What is the active material layer used in the present invention in that even when silver, gold, copper, etc. are dispersed instead of carbon nanotubes to form an active material layer, the conductivity of the active material layer is similarly increased? Differently.

[0057] (Method for producing positive electrode for secondary battery)

Next, the manufacturing method of the positive electrode for secondary batteries is demonstrated. The method for producing a positive electrode for a secondary battery of the present invention is a method for producing a positive electrode for a secondary battery having an active material layer containing at least a radical compound and carbon fiber, and more specifically, in a solvent containing a radical compound. The average value of the interlaminar distance d of the black lead structure is not less than 0.335 nm and not more than 0.340 nm.

002

It has the process of disperse | distributing carbon fiber, It is characterized by the above-mentioned.

[0058] First, a solution in which the radical compound is dissolved in a solvent is prepared, the carbon fiber and a binder (also referred to as a binder) are mixed with the solution, and ultrasonic waves are radiated to the mixed solution. Then, a slurry is obtained by dispersing the carbon fibers in the mixed solution. Next, after applying this slurry on the current collector to a predetermined thickness, the solvent is evaporated, whereby a positive electrode for a secondary battery having an active material layer can be produced.

[0059] As the solvent, n-methylpyrrolidone (NMP), tetrahydrofuran (THF), toluene and the like can be used. These may be used alone or in combination of two or more. [0060] As the binder, poly (vinylidene fluoride), bi-lidene fluoride monohexafluoropropylene copolymer, bi-lidene fluoride-tetrafluoroethylene copolymer, and the like can be used. These may be used alone or in combination of two or more. The ratio of the binder contained in the active material layer is preferably in the range of 1% by weight to 10% by weight. If the ratio of the binder in the active material layer is less than 1% by weight, there is a risk of peeling due to poor adhesion between the formed active material layer and the current collector. On the other hand, when the proportion of the binder in the active material layer exceeds 10% by weight, the proportion of the radical compound or carbon fiber in the active material layer is relatively lowered, so that the positive electrode according to the present invention is used. The capacity of the secondary battery may be reduced, and the mechanical strength of the active material layer may be insufficient.

[0061] As another method for producing a positive electrode for a secondary battery, the radical compound is dissolved in a solvent, the solution is impregnated in the carbon fiber-strength sheet, and the solvent is evaporated. A positive electrode for a secondary battery having a material layer can be manufactured. In this case, since the function as the current collector is borne by the sheet in which the carbon fibers are intertwined, the binder as described above is not included.

[0062] (Secondary battery)

Next, the secondary battery of the present invention will be described. The secondary battery of the present invention is composed of a positive electrode, a negative electrode and an electrolytic solution, and the positive electrode for a secondary battery is used as the positive electrode. In this secondary battery, since the positive electrode for a secondary battery according to the present invention described above is used, an increase in electrode resistance due to cracks in the active material layer and a deterioration in storage characteristics due to dropout of the active material layer. Can be suppressed. In addition, the active material layer of the positive electrode contains a radical compound that functions as an active material and has low electrode resistance, so that the charge / discharge capacity at a large current can be increased. Therefore, this secondary battery can be charged and discharged using a large current, has a large capacity and excellent storage characteristics.

[0063] In the present invention, any laminated form is not particularly limited as to the laminated form of the positive electrode and the negative electrode. For example, it may be a multilayer laminate, a form in which the current collectors are laminated on both sides, or a form in which these are wound.

[0064] The shape of the secondary battery of the present invention is not particularly limited, and a conventionally known one can be used. For example, a coin type, a cylindrical type, a square type, a sheet type, or the like can be used. wear.

FIG. 1 is a schematic cross-sectional view of a coin-type secondary battery showing an example of the secondary battery of the present invention.

A coin-type secondary battery 10 shown in FIG. 1 has a positive electrode 11 composed of an active material layer 1 and a current collector 3, and a negative electrode 12 also composed of an active material layer 2 and a current collector 4. The positive electrode 11 and the negative electrode A porous separator 13 is sandwiched between the two to prevent electrical connection between them. The positive electrode 11, the negative electrode 12 and the separator 13 are immersed in the electrolyte solution 5, and these are configured to be sealed in the positive electrode outer can 6 and the negative electrode outer can 7 by the insulating packing portion 8!, The

[0066] Like the positive electrode, the negative electrode is obtained by forming an active material layer for a negative electrode on a current collector, and the active material layer includes an active material for the negative electrode. The active material for the negative electrode is not particularly limited, and any conventionally known material can be used as long as the acid reduction potential is lower than that of the positive electrode. For example, natural graphite, petroleum coatas, coal coatas, pitch coatas, carbon black, activated carbon, fired carbonized resin, fired organic polymer, pyrolysis vapor grown carbon fiber, mesocarbon microbead, mesophase pitch carbon fiber Any of carbon materials such as polyacrylonitrile-based carbon fiber, fullerene, and carbon nanotube can be used. Also, lithium metal, lithium alloy, lithium nitride, Li

Three

It is also possible to use a Li-based material such as _M N (where X is 0 <x <1 and M is at least one element selected from Co, Ni, and Cu). These materials can be used alone or in combination of two or more.

[0067] As the current collector, one made of any material of copper, silver, copper alloy, silver alloy, and carbon can be used. Examples of the shape of the current collector include foil, flat plate, and mesh. Examples of a method for forming an active material layer including an active material for a negative electrode on a current collector include a method in which a mixture of a negative active material and a binder is applied to the current collector. be able to.

[0068] The binder is not particularly limited, and any conventionally known binder can be used. For example, polyvinylidene fluoride, vinylidene fluoride monohexafluoropropylene copolymer, Examples thereof include redene fluoride-tetrafluoroethylene copolymers. These materials may be used alone or in combination of two or more. Also, especially when metallic lithium or lithium alloy is used as the negative electrode active material. The current collector is also made of the same material, so that the entire negative electrode can be made of the same material.

[0069] As the electrolytic solution, an electrolytic solution in which an electrolyte salt is dissolved is used. The materials used for these are not particularly limited, and conventionally known materials can be used. Electrolyte at ^{20 ° C 10- 5 ~: LO-} is / cm arbitrariness desirable to have ionic conductivity.

[0070] Examples of electrolyte salts include LiPF, LiAsF, LiAlCl, LiCIO, LiBF, LiSbF, LiCF S

6 6 4 4 4 6 3

Select from lithium salts such as O, LiCF CO, Li (CF SO), LiN (CF SO), etc.

3 3 2 3 2 2 3 2 2

Can. Other electrolyte salts include quaternary ammonium salts such as tetraammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, and tetraethylphosphonium tetrafluoroborate. And quaternary phosphonium salts, imidazolium salts such as tetramethylborate tetramethylborate, and salts that are selected for isotropic force. These materials can be used alone or in combination of two or more.

[0071] The electrolyte solution solvent is capable of dissolving the above electrolyte salt, and is arbitrarily selected depending on the electrolyte salt used. Examples of the electrolyte solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and beylene carbonate (VC), dimethyl carbonate (DMC), jetyl carbonate (DEC), A mixture of two or more chain carbonates such as ethino-retinoyl carbonate (EMC) and dipropyl carbonate (DPC) can be used.

[0072] The separator is not particularly limited, and a conventionally known separator can be used. As a material for the separator, for example, polyolefin such as polypropylene and polyethylene, fluorine resin, and the like can be used. As the shape of the separator, for example, a porous thin film is preferably used.

Example

[0073] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1]

First, a positive electrode was produced. As radical compounds, the chemical formula A-l (R to R are all methyl

1 5

Poly (4-methacryloyloxy) which is a cyclic-toxyl structure-containing polymer represented by -2, 2, 6, 6-tetramethylpiperidine 1-oxyl) (PTME) was synthesized.

[0075] Example of synthesis of cyclic-troxyl structure-containing polymer: In a 100 ml eggplant flask equipped with a reflux tube, 20 g (0. O89 mol) of 4-methacryloyloxy 2, 2, 6, 6-tetramethylpiperidine 1-oxyl monomer was added. And dissolved in 80 ml of dry tetrahydrofuran. Thereto was added azobisisobutyric-tolyl (AIBN) O. 29 g (0.00187 mol) (monomer / AIBN = 5 OZl), and the mixture was stirred at 75 to 80 ° C. under an argon atmosphere. After reacting for 6 hours, it was allowed to cool to room temperature. The polymer was precipitated in hexane, filtered, and dried under reduced pressure to obtain 18 g (yield 90%) of poly (2, 2, 6, 6-tetramethylpiperidine metatalylate). Next, 10 g of the obtained poly (2, 2, 6, 6-tetramethylpiperidine metatalylate) was dissolved in 100 ml of dry-treated dichloromethane. To this, 100 ml of a dichloromethane solution of 15.2 g (0. 088 mol) of m-chloroperbenzoic acid was added dropwise over 1 hour with stirring at room temperature. Further, after stirring for 6 hours, the precipitated m-chlorobenzoic acid was removed by filtration, and the filtrate was washed with an aqueous sodium carbonate solution and water, and then dichloromethane was distilled off. The remaining solid is pulverized, and the resulting powder is washed with diethyl carbonate (DEC), dried under reduced pressure, and poly (4-methacryloyloyl), which is a cyclic nitroxyl structure-containing polymer represented by the chemical formula A-1. Xy 2,2,6,6-tetramethylpiperidine-1-oxyl) (PTME) 7.2 g was obtained (yield 68.2%, brown powder). The structure of the polymer obtained was confirmed by IR. As a result of measurement by GPC, values of weight average molecular weight Mw = 89000 and dispersity MwZMn = 3.30 were obtained. The spin concentration obtained from the ESR ^ vector was 2.48 X 10 ²¹ spin / g.

[0076] The above-mentioned radical compound having a cyclic-toxyl structure-containing polymer force, polyvinylidene fluoride (manufactured by Kureha Chemical) as a binder, and benzene gas were thermally decomposed, and iron fine particles were sprayed. Vapor-grown carbon fiber obtained by firing carbon fiber grown on the substrate at 2800 ° C (average value of interlaminar distance d of graphite structure is 0.336 nm, tensile modulus is 700 GPa),

002

A weight ratio of 4: 1: 5 was measured and mixed in n-methylpyrrolidone as a solvent to prepare a slurry. This slurry was irradiated with 40 kilohertz ultrasonic waves for 30 minutes, and then applied onto a positive electrode current collector 20 / zm thick aluminum foil using a doctor blade and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The positive electrode active material layer thus obtained had a thickness of 150 m. The active material layer after drying has Cracks and current collectors were not seen. The volume resistivity of the above vapor-grown carbon fiber was 300 μΩ′cm, the average length was 10 μm, and the average diameter was 0.5 ^ m.

Next, a negative electrode was produced. For the negative electrode, artificial graphite (manufactured by Osaka Gas: MCMB25-28) and rubber binder (manufactured by ZEON: BM-400B) were dispersed in water at a weight ratio of 95: 5 to prepare a slurry. Using a doctor blade, it was applied onto a copper foil having a thickness of 10 m, dried at 80 ° C., and then compressed with a roller. The negative electrode active material layer thus obtained had a thickness of 20 m. The active material layer after drying did not crack or fall off from the current collector.

[0078] As the electrolyte, an electrolyte salt containing 0.9 molZl of LiPF is used.

6

The salt was prepared by dissolving it in an electrolyte solvent consisting of ethylene carbonate Z jetyl carbonate mixed solution (volume mixing ratio 3: 7).

[0079] The positive electrode and the negative electrode produced as described above were cut into a circular shape having a size of 12 mm and overlapped with a 25-μm-thick porous polypropylene used as a separator. The coin-type secondary battery of the form shown in FIG.

[0080] (Example 2)

The same radical compound as in Example 1, the same polyvinylidene fluoride as in Example 1, the same vapor-grown carbon fiber as in Example 1, and acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.). 4: 1: 3: 2 were weighed and mixed in n-methylpyrrolidone as a solvent to prepare a slurry. The slurry was irradiated with ultrasonic waves of 40 kilohertz for 30 minutes, and then applied onto a 20 m thick aluminum foil as a positive electrode current collector using a doctor blade, and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The positive electrode active material layer thus obtained had a thickness of 150 m. The active material layer after drying did not crack or fall off from the current collector. A coin-type secondary battery of Example 2 was fabricated in the same manner as in Example 1 except for the negative electrode other than the positive electrode, the electrolyte, the cell router, and the like.

[Example 3]

The same radical compound as in Example 1, the same polyvinylidene fluoride as in Example 1, and benzene Vapor-grown carbon fibers obtained by pyrolyzing gas and firing carbon fibers grown on a substrate sprayed with iron fine particles at 3000 ° C (the average value of the interlayer distance d of the graphite structure is 0.335η)

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m, the tensile modulus is 800 GPa) and the same acetylene black as in Example 2 is weighed in a weight ratio of 4: 1: 1: 4 and mixed in n-methylpyrrolidone as a solvent to form a slurry. Made. The slurry was irradiated with ultrasonic waves of 40 kilohertz for 30 minutes, and then applied onto a 20 m thick aluminum foil as a positive electrode current collector using a doctor blade and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The positive electrode active material layer thus obtained was 150 m thick. The dried active material layer was strong enough to show no cracks or falling off the current collector. The volume resistivity of the above vapor grown carbon fiber was 200 μΩ′cm, the average length was 10 μm, and the average diameter was 0.5 μm. A coin-type secondary battery of Example 3 was produced in the same manner as Example 1 except for the negative electrode other than the positive electrode, the electrolyte, the separator, and the like.

[Example 4]

As a radical compound, a cyclic-toro represented by the chemical formula A-2 (R to R are all methyl groups).

14

We synthesized poly (4-ataryloxy2,2,6,6-tetramethylbiperidine 1-oxyl) (PTAA), a xyl structure-containing polymer.

[0083] Example of synthesis of cyclic-troxyl structure-containing polymer: In a 100 ml eggplant flask equipped with a reflux tube, 10 g of 4-ataryloxy 2, 2, 6, 6-tetramethylpiperidine 1-oxyl monomer was added in dry tetrahydrofuran. S-Butyllithium as a catalyst and polymerized at -20 ° C for 48 hours to obtain poly (4-atallyloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) 5.8g (Yield 58%, orange powder). The structure of the polymer obtained was confirmed by IR. As a result of measurement by GPC, a value of weight average molecular weight Mw = 4300 was obtained. The spin concentration obtained from the ESR spectrum was found to be 2. 66 X 1 0 ² spin, g.

[0084] The thus obtained radical compound having a cyclic-toxyl structure-containing polymer force, the same polyvinylidene fluoride as in Example 1, and benzene gas were thermally decomposed and grown on a substrate sprayed with iron fine particles. Vapor-grown carbon fiber obtained by calcining the carbon fiber that was fired at 2500 ° C (average value of the interlaminar distance d of the graphite structure is 0.337 nm, tensile modulus is 500 GPa), 4: 1: Weighed to a weight ratio of 5 and mixed them in the solvent n-methylpyrrolidone to make a slurry. This slurry was irradiated with ultrasonic waves of 40 kilohertz for 30 minutes, and then applied onto a 20 m thick aluminum foil as a positive electrode current collector using a doctor blade, and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The positive electrode active material layer thus obtained had a thickness of 150 / zm. The dried active material layer was strong enough to show no cracks or falling off the current collector. The volume resistivity of the above vapor-grown carbon fiber was 800 Ω′cm, the average length was 20 μm, and the average diameter was 0.5 μm. A coin-type secondary battery of Example 4 was produced in the same manner as Example 1 except for the negative electrode other than the positive electrode, the electrolyte, the separator, and the like.

[0085] (Example 5)

As a radical compound, a cyclic-toro represented by the chemical formula A-3 (R to R are all methyl groups).

14

Poly (4 buroxy 2, 2, 6, 6-tetramethylpiperidine 1-oxyl (PTVE), a xyl structure-containing polymer, was synthesized.

[0086] Synthesis Example of Cyclic-Troxyl Structure-Containing Polymer; 200 mL 3-neck round bottom flask under argon atmosphere, 2, 2, 6, 6-tetramethylpiperidine-4-vinyl-1-oxyl (monomer) 10.0 g, dichloromethane lOOmL And cooled to 78 ° C. Further, 280 mg (2 mmol) of boron trifluoride-jetyl ether complex was added and homogenized, and then reacted for 20 hours. After completion of the reaction, the solid obtained was washed several times with methanol and vacuum dried to obtain poly (4 buoxy 2, 2, 6, 6-tetramethylpiperidine 1-oxyl) (PTVE) as a red solid. (Yield 70%). The structure of the polymer obtained was confirmed by IR spectrum. Moreover, as a result of measuring the molecular weight of the DMF soluble part by GPC, the weight average molecular weight Mw = 89000 and the dispersity MwZMn = 2.7 were obtained. The spin density determined by ESR spectrum was 3.05 X 10 ²¹ spin / g.

[0087] The thus obtained radical compound having a cyclic-toxyl structure-containing polymer force, the same polyvinylidene fluoride as in Example 1, and benzene gas were thermally decomposed and grown on a substrate sprayed with iron fine particles. Vapor-grown carbon fiber obtained by firing the baked carbon fiber at 2300 ° C (average of interlaminar distance d of graphite structure is 0.340 nm, tensile modulus is 200 GPa)

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Carbon fibers are weighed in a weight ratio of 4: 1: 5, and they are in the solvent n-methylpyrrolidone. To prepare a slurry. The slurry was irradiated with ultrasonic waves of 40 kilohertz for 30 minutes, and then applied onto a 20 m thick aluminum foil as a positive electrode current collector using a doctor blade, dried at 125 ° C and dried. —Evaporation of methylpyrrolidone was used as the positive electrode. The positive electrode active material layer thus obtained had a thickness of 150 m. In the active material layer after drying, the cracks and current collector force did not fall off. The volume resistivity of the above vapor-grown carbon fiber was 2000 μΩ′cm, the average length was 20 μm, and the average diameter was 0.5 μm. A coin-type secondary battery of Example 5 was fabricated in the same manner as Example 1 except for the negative electrode other than the positive electrode, the electrolyte, the separator, and the like.

[0088] (Example 6)

Graphitized PTVE synthesized in the same manner as in Example 5, polyvinylidene fluoride as in Example 1, and carbon fiber with a mesophase pitch as a precursor (Petoriki Co., Ltd., interlayer distance d of graphite structure) The average value is 0.333 nm, the tensile modulus is 550 GPa, and the volume resistivity is 400 Ω

002

cm, an average length of 70 m, and an average diameter of 0.6 m) were weighed at a weight ratio of 4: 1: 5, and mixed in a solvent n-methylpyrrolidone to prepare a slurry. This slurry was irradiated with 40-kilohertz ultrasonic waves for 30 minutes, and then applied onto a 20 μm-thick aluminum foil as a positive electrode current collector using a doctor blade, and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The positive electrode active material layer thus obtained had a thickness of 135 m. The active material layer after drying did not show any cracks or falling off of the current collector. A coin-type secondary battery of Example 6 was fabricated in the same manner as Example 1 except for the negative electrode other than the positive electrode, the electrolyte, the separator, and the like.

[0089] (Comparative Example 1)

The same radical compound as in Example 1, the same polyvinylidene fluoride as in Example 1, and the same acetylene black as in Example 2 are weighed in a weight ratio of 4: 1: 5 and used as a solvent. A slurry was prepared by mixing with n-methylpyrrolidone. This slurry was irradiated with 40 kilohertz ultrasonic waves for 30 minutes, and then applied onto a 20 m thick aluminum foil as a positive electrode current collector using a doctor blade, and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The positive electrode active material layer thus obtained had a thickness of 150 m. The active material layer after drying was cracked and dropped from the current collector. Negative electrode other than positive electrode, electrolyte And the separator and the like were made in the same manner as in Example 1 to produce a coin-type secondary battery of Comparative Example 1.

[0090] (Comparative Example 2)

The same radical compound as in Example 1, the same polyvinylidene fluoride as in Example 1, and gold powder (average particle size 3 m) were weighed to a weight ratio of 4: 1: 5, and they were used as solvents. A slurry was prepared by mixing with n-methylpyrrolidone. This slurry was irradiated with 40 kilohertz ultrasonic waves for 30 minutes, and then applied onto a 20 m thick aluminum foil, which is a positive electrode current collector, using a doctor blade, and dried at 125 ° C. A positive electrode was obtained by evaporating n-methylpyrrolidone. The active material layer of the positive electrode thus obtained was 150 m thick. The dried active material layer was cracked and detached from the current collector. A coin-type secondary battery of Comparative Example 2 was produced in the same manner as Example 1 except for the negative electrode other than the positive electrode, the electrolyte, the separator, and the like.

[0091] (Evaluation of battery characteristics)

The coin-type secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2 were charged and discharged at a constant current in a voltage range of 2V force and 4V. Charging / discharging was performed in a thermostatic chamber set at 20 ° C. The charge current was 1C and the discharge current was 1C and 50C. The discharge capacity in each case was measured. The 1C current is a current value at which discharge is completed in one hour, and the 50C current is a current 50 times the 1C current. As a measure of the capacity characteristics of the secondary battery during large current discharge, the ratio of the discharge capacity at 50C current to the discharge capacity at 1C current was investigated.

[0092] Further, after charging the fabricated coin-type secondary battery to 4V with a 1C current, storing it in a thermostat set at 20 ° C for one week, and then discharging to 2V with a 1C current and its remaining capacity Was measured. As an amount indicating the storage characteristics of the secondary battery, the ratio of the remaining capacity after one week to the discharge capacity before storage was examined.

[0093] For the secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2, the state of appearance of each positive electrode and the results of examining the above characteristics are shown in Table 1.

[0094] [Table 1] Carbon fiber Carbon fiber Carbon fiber electrode Firing capacity Discharge capacity Weekly discharge capacity Mixing ratio Tensile modulus Volume resistivity Cracking Discharge capacity Discharge capacity before storage

Presence or absence of drop

Example None

Comparison example Yes

[0095] The positive electrodes of Examples 1 to 6 did not crack or fall off, whereas the positive electrodes of Comparative Examples 1 and 2 were cracked or dropped. The positive electrodes of Examples 1 to 6 were free from cracking or falling off because the active material layer contained carbon fibers having an average value of the interlayer distance d of the graphite structure in the range of 0.335 nm to 0.340 nm. This is because the mechanical strength of the active material layer of the positive electrode is improved.

[0096] Regarding the ratio of the 50C discharge capacity to the 1C discharge capacity, the secondary batteries of Examples 1 to 6 were all stronger than the secondary battery of Comparative Example 1. This is because, in the secondary batteries of Examples 1 to 6, the active material layer of the positive electrode is not cracked, the conductivity of the active material layer is high, and the electrode resistance of the positive electrode is low. This shows an improvement over the comparative example.

[0097] Regarding the ratio of the discharge capacity after one week storage to the discharge capacity before storage, the secondary batteries of Examples 1 to 6 were all stronger than the secondary battery of Comparative Example 1. This indicates that in the secondary batteries of Examples 1 to 6, since the active material layer did not fall off, the capacity retention characteristics were improved as compared with the comparative example.

[0098] Further, the secondary battery of Comparative Example 2 has no capacity at 1C discharge, and the ratio of 50C to the 1C discharge capacity and the ratio of the discharge capacity after one week storage to the discharge capacity before storage should be obtained. I couldn't do it. This is probably because the charge transfer resistance at the interface between the radical compound and the gold particles was significantly higher than that of carbon fiber, and the charge / discharge reaction did not proceed. Therefore, even if the same conductor is used, a positive electrode with low electrode resistance cannot be obtained when an active material layer containing gold is used instead of carbon fiber.

Claims

The scope of the claims

[1] The average value of the distance d between the radical compound and the graphite structure is 0.335 nm or more.

002

A positive electrode for a secondary battery comprising an active material layer containing at least carbon fibers within a range of m or less.

[2] The positive electrode for a secondary battery according to [1], wherein a tensile elastic modulus of the carbon fiber is in a range of 200 GPa to 800 GPa.

[3] The positive electrode for a secondary battery according to claim 1 or 2, wherein the volume resistivity of the carbon fiber is in the range of 200 μΩ′cm to 2000 μΩ′cm.

4. The secondary battery positive electrode according to any one of claims 1 to 3, wherein the carbon fiber is a vapor-grown carbon fiber.

5. The positive electrode for a secondary battery according to any one of claims 1 to 3, wherein the carbon fiber is obtained by graphitizing a carbon fiber having a mesophase pitch as a precursor.

[6] The secondary battery according to any one of claims 1 to 5, wherein a content ratio of the carbon fiber in the active material layer is in a range of 10 wt% to 50 wt%. Positive electrode.

[7] The radical compound includes at least one of a polymer-troxyl radical compound, a polymer oxyradical compound, and a polymer hydrazyl radical compound. The positive electrode for a secondary battery according to any one of claims 1 to 6.

[8] Polymer-troxyl radical compound strength Poly (4-methacryloyloxy 2, 2, 6

, 6-Tetramethylpiperidine 1-oxyl), Poly (4-Atalyloxyl 2, 2, 6,

8. The positive electrode for a secondary battery according to claim 7, which is 6-tetramethylpiperidine-1-oxyl) or poly (4 vinyloxy 2,2,6,6-tetramethylpiperidine 1-oxyl).

[9] A method for producing a positive electrode for a secondary battery having an active material layer containing at least a radical compound and carbon fiber, wherein an average value of the interlayer distance d of the graphite structure is determined in a solvent containing the radical compound. Disperse the carbon fiber in the range of 0.335 nm or more and 0.30 nm or less.

002

A process for producing a positive electrode for a secondary battery.

[10] The positive electrode for a secondary battery according to [9], wherein the carbon fiber content in the active material layer is dispersed so as to fall within a range of 10 wt% to 50 wt%. Manufacturing Method.

A secondary battery comprising at least a positive electrode, a negative electrode, and an electrolyte solution, wherein the positive electrode is a positive electrode for a secondary battery according to any one of claims 1 to 8.