JP2009108444A - Method for producing mesophase pitch-based carbon fiber baked at low-temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a carbon fiber as a cathode material for a high-capacity lithium secondary battery, capable of markedly improving its own initial coulomb efficiency and suitable to pulse high current applications. <P>SOLUTION: The carbon fiber is obtained by immersing a mesophase pitch-based carbon fiber precursor in at least one saturated hydrocarbon solution selected from decalin, pyridine, toluene, xylene and benzene solutions followed by baking the precursor at 600-1,500°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mesophase pitch-based low-temperature calcined carbon fiber and a method for producing the same, a negative electrode material for a lithium secondary battery that becomes mesophase pitch-based low-temperature calcined carbon fiber particles, and a method for producing the same.

  In recent years, air pollution, global warming, and depletion of petroleum resources have been pointed out. From the viewpoint of dealing with such environmental problems and energy saving measures, midnight power storage systems, home-use distributed storage systems, solar power storage systems, storage systems for electric vehicles, and the like are attracting attention.

In these power storage systems, it is required that the energy density of the battery used is high, and in order to meet such required performance, lithium ion batteries are promising candidates for high energy density batteries used in power storage systems. Development is underway.
With the increase in functionality and digitization of electronic devices, lithium secondary battery performance characteristics are required to have high energy density, high output, and stable output characteristics.

  Such a lithium secondary battery has a high voltage, a high energy density, a high output, and has a wide operating temperature range because it uses a non-aqueous electrolyte, has many advantages such as excellent long-term storage and miniaturization. Therefore, it can be suitably used for applications such as a mobile phone, a portable computer, a video camera, and an electric vehicle.

  For example, in a combination of a high-efficiency engine and a power storage system (HEV) or a combination of a fuel cell and a power storage system (FCV), in order for the engine or the fuel cell to operate with high efficiency, operation at a constant output is required. In order to cope with load-side output fluctuation or energy regeneration, the power storage system is required to have high output discharge characteristics.

In addition, for example, while mobile phones and the like are becoming smaller and more multifunctional, the secondary power source used is reducing average power consumption due to power saving, but requires a large current during communication. Pulsed use is increasing. That is, in addition to the requirement for high energy density, high output characteristics for several seconds are also required.
As described above, there is a strong demand for practical use of a battery having both high output and high energy density, but no battery that satisfies this technical requirement has been developed at present.

  In order to achieve high energy density and high output at the same time, a multifaceted approach from a positive electrode material, a negative electrode material, an electrolytic solution, or other various battery constituent materials is necessary. However, as an electrode for the negative electrode, attempts have been made to reduce the resistance by thinning the electrode to improve the characteristics such as higher output, and although it has become possible to provide lithium secondary batteries with improved characteristics to a certain extent, There still remain problems such as the need for carbon materials for output negative electrodes and the use of large current pulses.

  On the other hand, for example, as a negative electrode material for a lithium secondary battery used for the above-described negative electrode, various carbon materials and polyacene-based materials that are low-temperature calcined carbon materials of polycyclic aromatic conjugated structure substances have been developed. Yes.

In particular, a carbon material of a polycyclic aromatic conjugated structure substance obtained by processing at a relatively low temperature of 550 to 1000 ° C. is attracting attention as a material exceeding the theoretical capacity of C ₆ Li (372 mAh / g). (For example, refer to Patent Documents 1 and 2). Although the above example is a high-performance material, many problems to be improved remain in practical use due to problems such as initial coulomb efficiency and charge / discharge acceptance characteristics.

Further, for example, a polycyclic aromatic hydrocarbon obtained by thermally decomposing a raw material containing pitch as a main component at a low temperature has a specific surface area of 50 m ² / g by a BET method and a hydrogen / carbon atomic ratio of 0.35 to 0.35. A negative electrode material for a non-aqueous secondary battery, which is 0.05, is disclosed (see, for example, Patent Documents 3, 4, 5, 6, 7, and 8). In the above example, it is difficult to improve the initial coulomb efficiency, the charge / discharge characteristics, and the cycle characteristics unless the negative electrode material having a specific structure of the pitch carbon material is produced with a specific basis weight or less.

  Also disclosed is a negative electrode material for a non-aqueous secondary battery, for example, which is a polycyclic aromatic hydrocarbon by subjecting a raw material mainly composed of naphthalene pitch to a thermal reaction at low temperature without infusibilizing treatment. (For example, see Patent Documents 9, 10, and 11). Conventionally, the polycyclic aromatic hydrocarbon carbon material produced by heat treatment in an inert atmosphere has a high specific surface area and has a problem of initial efficiency. On the other hand, the above example has a problem that the initial yield is improved by not performing the infusibilization treatment, but the carbon yield after the heat treatment is poor and the production method is not efficient.

  For example, a polycyclic aromatic conjugated structure material heat-treated at a low temperature using petroleum pitch as a starting material has been disclosed (see, for example, Patent Documents 12, 13, 14, and 15). In the above example, a polycyclic aromatic conjugated structure material is obtained by heat treatment at a temperature of 550 to 1000 ° C., but problems such as insufficient capacity and initial Coulomb efficiency remain. I went.

  As described above, for the purpose of increasing the capacity, polyacene-based materials (polycyclic aromatic conjugated structure materials) starting from phenol resin, and pitch systems that do not undergo infusibilization for the purpose of improving the initial coulomb efficiency Low-temperature calcined carbon materials (polycyclic aromatic conjugated structure materials) obtained by low-temperature heat treatment of materials (polycyclic aromatic conjugated structure materials) and coke, petroleum pitch, etc. for the purpose of manufacturing costs have been studied. However, none of them solved the problem to be achieved by the present application.

JP 2000-251885 A JP 2002-63892 A Japanese Patent Laid-Open No. 2003-22804 JP 2004-95205 A JP 2004-95203 A JP-A-2005-19095 JP 2004-95202 A JP 2004-95204 A JP 2005-19093 A JP 2004-39489 A JP 2004-95201 A JP 2003-22803 A JP 2005-19094 A JP 2002-63892 A Japanese Patent Laying-Open No. 2005-22803

  The object of the present invention is to greatly improve the low initial Coulomb efficiency, which is one of the problems of the conventional low-temperature calcined carbon, and is suitable for high capacity and pulsed high current applications. It aims at providing the negative electrode material for secondary batteries, and its manufacturing method.

  As a result of intensive investigations while paying attention to the problems of the prior art in order to solve the above problems, the present inventors have paid attention to saturated hydrocarbon-soluble substances contained in mesophase pitch-based carbon fiber precursors. As a result of repeated studies, the present invention has been completed.

That is, the object of the present invention is to
After immersing the mesophase pitch-based carbon fiber precursor in at least one saturated hydrocarbon solution selected from decalin, pyridine, toluene, xylene, and benzene, the pitch-based carbon fiber precursor is heated to a temperature of 600 to 1500 ° C. This can be achieved by a method for producing a mesophase pitch-based low-temperature calcined carbon material that is calcined at a low temperature.

  The present invention includes that the mesophase pitch-based carbon fiber precursor is made of a raw material selected from coal, a volatile organic substance obtained from petroleum-based pitch, a melt-soluble organic substance, and an infusible fibrous organic substance.

Furthermore, another object of the present invention is to
This is achieved by a mesophase pitch-based low-temperature calcined carbon material suitable as a negative electrode material for a lithium secondary battery having a specific surface area of 5 to 50 m ² / g obtained from the nitrogen adsorption isotherm obtained from the nitrogen adsorption isotherm by the above-described production method. be able to.

The present invention includes that the surface spacing (d ₀₀₂ ) of the 002 plane is in the range of 0.335 to 0.41 nm.

  Furthermore, the present invention includes a carbon fiber composite material including at least the mesophase pitch-based low-temperature fired carbon material.

  Furthermore, the present invention includes a negative electrode for a lithium secondary battery having the mesophase pitch-based low-temperature fired carbon material as a main component of a negative electrode active material, and a lithium secondary having the carbon fiber structure material as a main component of a negative electrode active material. A battery negative electrode and a lithium secondary battery using these lithium secondary battery negative electrodes are included.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to improve initial stage Coulomb efficiency, the mesophase pitch type low-temperature-fired carbon fiber which can improve discharge capacity can be obtained.

Hereinafter, the present invention will be described in detail.
In the present invention, when producing a carbon fiber precursor from a mesophase pitch which is a starting material, fiberization and infusibilization treatment are performed. In the fiberization, any means for fiberizing the raw material pitch can be adopted, but it is preferable to perform spinning by a melt blow method from the viewpoint of productivity and the quality of the obtained fiber.

At this time, the spinning temperature is a temperature range above the softening point of the raw material pitch to be used and the mesophase pitch does not change, generally 220 ° C. to 380 ° C., preferably 250 ° C. to 350 ° C.
Therefore, as the raw material pitch, those having a low softening point and a high reaction rate in the infusibilization treatment described later are advantageous from the viewpoint of production cost and stability.

  When the mesophase pitch fiber obtained by the above fiberization is fired as it is, it may be remelted in the firing process, and the graphite layer / orientation formed in the spinning process may be disturbed or the fiber shape may be lost. Therefore, infusibilization processing is performed.

  The infusibilization method is not particularly limited, but is a method of heat treatment in an oxidizing gas atmosphere such as nitrogen dioxide or oxygen, a method of treatment in an oxidizing aqueous solution such as nitric acid, light or γ-ray, etc. Any conventionally known method, such as a polymerization treatment by the above, can be employed.

  In particular, a simpler infusibilization method is preferably performed in air, and examples include a method of heat treatment in air at 150 to 350 ° C. and an average temperature increase rate of 5 ° C./min for a predetermined time. .

  In the production method of the present invention, the carbon fiber precursor thus obtained is immersed in at least one saturated hydrocarbon solution selected from decalin, pyridine, toluene, xylene, and benzene.

The immersion may be performed under any conditions as long as the components soluble in the saturated hydrocarbon solution contained in the carbon fiber precursor can be sufficiently removed. Examples of the solution temperature at the time of immersion from second to 140 hours include temperatures from about 20 ° C. which is room temperature to less than the boiling point of the solution.
In the production method of the present invention, the mesophase pitch-based carbon fiber precursor subjected to the above immersion is fired at a temperature of 600 to 1500 ° C.

  In the case of obtaining normal carbon fiber, the carbon fiber precursor is fired in a temperature range where the graphite structure does not develop around 2000 ° C., but in the case of low-temperature fired carbon, 600 ° C. to 1500 ° C., preferably 600 It is preferable to perform the baking in a temperature range of from ° C to 1200 ° C, more preferably from 600 ° C to 1000 ° C.

  In the production method of the present invention, the mesophase pitch-based carbon fiber precursor can be obtained from any of synthetic pitches using petroleum, coal-based, resin-based, etc., but preferably coal It is preferably made of a raw material selected from volatile organic substances, melt-soluble organic substances and infusible fibrous organic substances obtained from petroleum pitch.

  Mesophase pitch carbon fiber precursors made of these raw materials are advantageous from the viewpoint of production cost and stability because of their low softening point and high infusibility reaction rate due to the spinning temperature.

The mesophase pitch-based low-temperature calcined carbon fiber obtained by the production method of the present invention has a specific surface area of 5 to 50 m ² / g determined by a BET method from a nitrogen adsorption isotherm.
If the specific surface area is too small, the initial discharge capacity and discharge output of the finally obtained lithium secondary battery are not sufficient. On the other hand, when the specific surface area is too large, the initial coulomb efficiency of the finally obtained lithium secondary battery is significantly reduced and the density of the electrode is reduced, so that the capacity per volume is reduced. . The specific surface area is preferably in the range of 10 to 50 m ² / g, and more preferably in the range of 10 to 40 m ² / g.

In addition, the mesophase pitch-based low-temperature-fired carbon fiber preferably has a 002 plane spacing (d ₀₀₂ ) in the range of 0.335 to 0.41 nm, and in the range of 0.335 to 0.375 nm. Is more preferable.

  The mesophase pitch-based low-temperature calcined carbon fiber of the present invention is much wider than the interlayer spacing such as ordinary graphite, so when it is used as an electrode material for a lithium secondary battery, lithium ions are smoothly occluded / Can be released. Further, the amount of occluded / released lithium ions can be greatly increased as compared with the graphite material. As a result, the charge / discharge capacity of the finally obtained lithium secondary battery can be improved, and the cycle characteristics can be improved.

The carbon fiber structure material of the present invention further includes at least carbon fiber in addition to the mesophase pitch-based low-temperature fired carbon fiber of the present invention.
Here, as the carbon fiber to be included, at least the carbon fiber which is prepared from the carbon compound and the low-temperature calcined carbon compound and leaks at least on the surface of the low-temperature calcined carbon compound can be exemplified, preferably the entire carbon fiber As, since the surface portion of the carbon compound and the low-temperature calcined carbon compound are combined, the obtained carbon fiber is a carbon material having both.

Further, the mixing ratio of the mesophase pitch-based low-temperature fired carbon fiber and carbon fiber may be any form as long as the low-temperature fired carbon compound leaks to the surface as a composite form of carbon fiber. , A form in which the carbon compound is formed into a fiber and the low-temperature fired carbon compound covers part or all of the fiber surface, or a form in which the low-temperature fired carbon compound and the carbon compound are combined in a side-by-side manner Can do. The carbon fiber preferably has a 002 plane spacing (d ₀₀₂ ) in the range of 0.335 to 0.37 nm and a net plane group thickness (Lc) in the range of 1.0 nm to 130 nm.

The carbon fiber structure includes not only a collection of carbon fibers but also a fiber structure processed into a shape such as a woven fabric or a non-woven fabric.
When used as a negative electrode material for a lithium secondary battery, for example, the fiber structure is preferable from the viewpoints of moldability, workability, and the like.

In the negative electrode for a lithium secondary battery of the present invention, particles obtained by milling the above-mentioned mesophase pitch-based low-temperature-fired carbon fiber may be used as a main component of the negative electrode active material, or the carbon fiber structure material described above may be the main component of the negative electrode active material. It may be an ingredient.
By using these as the main components of the negative electrode active material, it is possible to provide a negative electrode for a lithium secondary battery with high initial Coulomb efficiency, high capacity and high performance.

  The negative electrode for a lithium secondary battery in the present invention can be produced, for example, by the following method. For example, an appropriate binder is mixed with the negative electrode material of the present invention, and a negative electrode active material is mixed as necessary to improve conductivity. A solvent for dissolving the binder is added to this mixture, and if necessary, it is sufficiently stirred using a homogenizer and glass beads to form a slurry.

  The slurry is applied to a current collector such as rolled copper foil or copper electrodeposited copper foil using a doctor blade or the like, dried, and then consolidated by roll rolling to produce a negative electrode for a lithium secondary battery. can do.

Here, as the binder, rubber-based materials such as poly (vinylidene fluoride) (PVdF), polytetrafluoroethylene, fluororesin, fluororubber, and SBR can be used. The amount of the binder can be appropriately determined according to the type, particle diameter, shape, target electrode thickness, strength, etc. of the negative electrode material, and is not particularly limited.
As the solvent, an organic solvent such as NMP (N-methylpyrrolidone) or DMF (dimethylformamide) or water can be used depending on the binder.

  As the negative electrode active material, the above-described mesophase pitch-based low-temperature calcined carbon of the present invention or a carbon fiber structure material may be used as a main component (at least 50% by weight or more), but a material capable of inserting and extracting lithium as another component. Can be used without any particular limitation, for example, artificial graphite, natural graphite, mesophase pitch hydrocarbon, non-graphitizable carbon material, petroleum coke, which becomes an intercalation compound by occlusion of lithium ions, An easily graphitizable carbon material or a mixed material with the above-described materials can be used. Although metal fine particles can be used, a carbon material (especially acetylene black, ketjen black, carbon black) is preferable. Since the carbon material can occlude lithium ions between the layers, the carbon material can contribute to the capacity of the negative electrode in addition to the conductivity, and is also rich in electrolyte retention.

  In producing a negative electrode for a lithium secondary battery using the negative electrode material for a lithium secondary battery in the present invention, for example, a known conductive material such as acetylene black, ketjen black, carbon black, graphite, and metal fine particles is used. Although it is possible, acetylene black, ketjen black, and carbon black are particularly preferable because they have a great effect of reducing internal resistance. The addition amount of the conductive material may be appropriately determined according to the type of active material used for the electrode, particle diameter, shape, target electrode thickness, strength, electrical conductivity, etc., but 1% by weight of the electrode weight The content is preferably 35% by weight or less. More preferably, the content is 3% by weight or more and 10% by weight or less. The addition amount of the binder is preferably 1% by weight or more and 20% by weight or less based on the active material. More preferably, the content is 3% by weight or more and 10% by weight or less. When the amount added is large, there is a problem that the internal resistance is large and sufficient output characteristics cannot be obtained.

A lithium secondary battery is produced using the negative electrode produced as described above. The lithium secondary battery includes a negative electrode, a positive electrode, a separator, and an electrolyte as a basic structure.
Although what was manufactured from the negative electrode material of this invention as mentioned above is used for a negative electrode, it does not restrict | limit especially about another positive electrode, a separator, and electrolyte, All can use a well-known thing.

  The active material of the positive electrode is not particularly limited as long as it is a material capable of inserting and extracting lithium. For example, lithium composite cobalt oxide, lithium composite nickel oxide, lithium composite manganese oxide, or a mixture of the above Alternatively, a lithium composite oxide such as a system in which one or more kinds of different metal elements are added to the composite oxide can be used. Moreover, although a disulfide type compound, a polyacene type substance, activated carbon, etc. can be used, in order to obtain a battery having a high voltage and a high capacity, it is preferable to use a lithium composite oxide.

  The separator plays a major role in holding the electrolyte, as well as serving as an insulator disposed between the positive electrode and the negative electrode. Although there is no particular limitation, a single-layer or multi-layer separator can be used. In addition, the separator material is not particularly limited, and examples thereof include polyolefins such as polyethylene and polypropylene, paper, glass, cellulose, and the like, depending on the heat resistance and safety design of the lithium secondary battery. Can be determined as appropriate.

The electrolyte is also the same as a conventional non-aqueous electrolyte in which an electrolyte material such as a known lithium salt is dissolved in a known solvent. The electrolyte can be appropriately determined according to a conventional method, comprehensively considering the types of electrode material, negative electrode material, etc., usage conditions such as charging voltage, and the like. More specifically, lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ are used in one or two kinds such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, dimethoxyethane, γ-butyrolactone, and the like. A solution dissolved in the above organic solvent is used.

  Further, the shape, size, etc. of the lithium ion secondary battery in the present invention are not particularly limited, and any shape such as a cylindrical type, a square type, a film type battery, a coin type, and the like may be used according to each application. What is necessary is just to select the thing of a dimension. The material for the battery container is appropriately selected depending on the use and shape of the battery, and is not particularly limited, and is typically stainless steel, aluminum, aluminum-laminated film, and the like, which can also be applied in the present invention. is there.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In addition, each value in an Example was calculated | required according to the following method.
Charging capacity (mAh / g):
The charge capacity was determined from the capacity after charging at room temperature to 2.0 V with a constant current of 0.1 mA / cm ² .
Discharge capacity (mAh / g):
The discharge capacity was obtained from the capacity after discharging at room temperature to 0 V with a constant current of 0.1 mA / cm ² .
Initial coulomb efficiency (%):
The initial coulomb efficiency was obtained from the following formula after charging and discharging for 3 cycles.
[Equation 1]
Initial Coulomb efficiency = Discharge capacity / Charge capacity x 100 (%)

[Example 1]
Petroleum mesophase pitch was used as a raw material, and a melt pitch was ejected from the slit using a die in a temperature range of 350 ° C., which is equal to or higher than the softening point, and mesophase pitch fiber was produced by a melt blow method. The ejected mesophase pitch fibers were collected on a collecting plate to obtain mat-like mesophase pitch fibers. The result of X-ray diffraction analysis of this fiber is shown in FIG.

  The resulting mat-like mesophase pitch fiber was infusibilized and then milled to obtain a mesophase pitch carbon fiber precursor (particulate). When this precursor was measured with a laser diffraction particle size distribution analyzer, the average particle size was 10 μm.

  This precursor is immersed in toluene (25 ° C.) as a saturated hydrocarbon solution for 120 hours to remove soluble components, followed by filtration and drying to obtain a mesophase pitch-based carbon precursor that has been subjected to immersion treatment. It was. Next, the mixture was put into a high-speed rotary pulverizer and pulverized to obtain a mesophase pitch-based carbon precursor (toluene solubles removed product). The result of the X-ray diffraction analysis of this precursor is shown in FIG.

  Subsequently, the obtained mesophase pitch-based carbon precursor particles subjected to immersion treatment were fired at 800 ° C. to obtain mesophase pitch-based carbon (low-temperature fired product). FIG. 3 shows an X-ray diffraction analysis of this mesophase pitch-based carbon (low-temperature fired product).

Further, when mesophase pitch-based carbon (low-temperature fired product) was measured with a laser diffraction particle size distribution analyzer, the average particle diameter d _(0.5) was 1 to 2 μm. Table 1 shows the specific surface area determined by the BET method from the nitrogen adsorption isotherm.

Next, using the obtained mesophase pitch-based carbon (low-temperature fired product) as a negative electrode active material, negative electrode material powder 87 parts by mass, conductive material acetylene black 3 parts by mass, binder polyvinylidene fluoride (PVdF) 10 parts by mass, And N-methylpyrrolidone (NMP) which is a solvent was mixed, and the slurry for negative electrode formation was obtained. The slurry was applied to one side of a copper foil having a thickness of 16 μm, dried, and then pressed to obtain an electrode for negative electrode having a thickness of 86 μm (negative electrode material layer thickness 70 μm). This electrode sheet is punched into a circular shape with a diameter of 7.0 mm, used as a working electrode, metallic lithium as a counter electrode, a separator made of a porous polypropylene film inserted between the working electrode and the counter electrode, and an electrolytic solution (ethylene carbonate and ethyl carbonate). A lithium secondary battery half-cell was prepared in an argon dry box using a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / liter in a solvent in which methyl carbonate was mixed at a weight ratio of 70:30, and charge / discharge characteristics at the negative electrode Evaluated.

<Charge / discharge capacity evaluation>
The charge / discharge capacity of the battery obtained in the test example was evaluated. The conditions, conducted to 3.0V charged at room temperature with a constant current of 0.1 mA / cm ^2, and discharge was conducted discharged to 0V with a constant current of 0.1 mA / cm ^2. Thereafter, charging was performed at a constant current of 0.1 mA / cm ² up to 2.0 V, and thereafter, a constant voltage of 2.0 V was performed for 3 hours. And discharge was performed to 0 V with a constant current of 0.1 mA / cm ² .
Table 2 summarizes the average values obtained by repeating this charge and discharge for 3 cycles.

[Comparative Example 1]
In Example 1, the same operation was performed except that the immersion treatment was not performed.

2 is an X-ray diffraction analysis diagram of a mesophase pitch-based carbon precursor obtained by the operation of Example 1. FIG. 2 is an X-ray diffraction analysis diagram of a mesophase pitch-based carbon precursor (a product from which toluene can be removed) obtained by the operation of Example 1. FIG. 2 is an X-ray diffraction analysis diagram of mesophase pitch-based carbon (low-temperature fired product) obtained by the operation of Example 1. FIG.

Claims (9)

  After immersing the mesophase pitch-based carbon fiber precursor in at least one saturated hydrocarbon solution selected from decalin, pyridine, toluene, xylene, and benzene, the mesophase pitch-based carbon fiber precursor is heated to 600-1500 ° C. A method for producing mesophase pitch-based low-temperature-fired carbon fibers that is fired at a temperature.   The production method according to claim 1, wherein the mesophase pitch-based carbon fiber precursor is made of a raw material selected from coal, a volatile organic material obtained from petroleum-based pitch, a melt-soluble organic material, and an infusible fibrous organic material. A mesophase pitch-based low-temperature-fired carbon fiber having a specific surface area of 5 to 50 m ² / g obtained from the nitrogen adsorption isotherm obtained by the BET method, obtained by the production method according to claim 1. The mesophase pitch-based low-temperature calcined carbon fiber according to claim 3, wherein a surface spacing (d ₀₀₂ ) of 002 faces is in a range of 0.335 to 0.41 nm.   A carbon fiber structure material suitable as a negative electrode material for a lithium secondary battery, comprising at least the mesophase pitch-based low-temperature fired carbon fiber according to claim 3.   The electrode for lithium secondary battery negative electrodes which uses the particle | grains which milled the mesophase pitch type low-temperature-fired carbon fiber of Claim 3 as a main component of a negative electrode active material.   The electrode for lithium secondary battery negative electrodes which uses the carbon fiber structure material of Claim 5 as a main component of a negative electrode active material.   The lithium secondary battery using the electrode for lithium secondary battery negative electrodes of Claim 6.   The lithium secondary battery using the electrode for lithium secondary battery negative electrodes of Claim 7.

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