JPH11176442A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery, having superion cycle characteristics in a wide temperature range, from high temperatures to low temperatures by improving a negative electrode active material. SOLUTION: In a secondary battery comprising a positive electrode of lithium including oxide, and a negative electrode of mix of meso-phase graphite and vapor phase deposition carbon fibers, the meso-phase graphte in the mix has a volume average grain diameter of 3 μm or more and 15 μm or less, a specific surface of 0.7 m<2> /g or more and 5.0 m<2> /g or less as measured by BET method, and a face interval (d 002) of 3.36 Å or more and 3.40 Å or less for a face (002) by a wide-angle X-ray diffraction method, and the vapor phase deposition carbon fiber has a specific surface of 10 m<2> /g or more and 20 m<2> /g or less as measured in the BET method, an average fiber diameter of 0.1 μm or more and 0.3 μm or less, and a face interval (d 002) of 3.36 Å or more and 3.40 Åor less for a face 002 by the wide angle X-ray diffraction method, and a ratio of the meso-phase graphite and the vapor phase deposition carbon fibers is set at 97:3-80:20 by weight ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly, to a small, lightweight and novel negative electrode for a secondary battery.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become portable,
Cordless technology is rapidly advancing. Accordingly, there has been an increasing demand for a small, lightweight, and high energy density secondary battery serving as a driving power supply. From such a viewpoint, a non-aqueous electrolyte secondary battery, particularly a lithium secondary battery, is expected to be particularly high as a battery having a high voltage and a high energy density, and its development has been rushed.

Conventionally, manganese dioxide, vanadium pentoxide, titanium disulfide, and the like have been used as a positive electrode active material of a lithium secondary battery. A battery was constituted by the positive electrode, the lithium negative electrode, and the organic electrolyte, and charging and discharging were repeated. However, in general, in a secondary battery using lithium metal for the negative electrode, problems such as an internal short circuit due to dendritic lithium generated at the time of charging and a side reaction between the active material and the electrolytic solution are major obstacles to the formation of the secondary battery. Further, no satisfactory charge / discharge characteristics or overdischarge characteristics have been found.

In recent years, the safety of lithium batteries has been strictly pointed out, and it is extremely difficult to ensure safety in battery systems using lithium metal or lithium alloy for the negative electrode.

[0005] Recently, a new type of electrode active material utilizing an intercalation reaction of a layered compound has attracted attention, and an interlayer compound has been considered as an electrode material for a secondary battery. In particular, a carbon material capable of intercalating or deintercalating Li ions is promising as a negative electrode material for a lithium secondary battery, and its development has been actively carried out and many reports have been made.

Above all, mesophase microspheres generated by heat treatment at a pitch of 350 to 450 ° C. are separated and extracted, and optically anisotropic granules having a lamellar structure consisting of a single phase are graphitized. Since the obtained graphite powder (hereinafter, referred to as mesophase graphite) is spherical, it has good filling properties as an electrode plate, is expected to have a high capacity, and has a large amount of intercalation of lithium. Japanese Patent Application Laid-Open No. H11-15545 discloses that a lamella structure allows lithium to enter and exit smoothly during charging and discharging, which is advantageous in high-rate charging and discharging.
7, JP-A-4-115458, JP-A-4-115458
No. 280068, and the like. In addition, with only mesophase graphite, the expansion and contraction of the crystal in the c-axis direction of the graphite accompanying charge and discharge causes the electrode plate to swell during the repetition of the charge and discharge cycle, making it impossible to maintain the original shape and reducing the capacity. For this reason, since the so-called cycle characteristics are insufficient in practical use, a proposal to improve the cycle characteristics by increasing the strength of the electrode plate by mixing vapor-grown carbon fibers with mesophase graphite has been proposed in JP-A-4-237971, It is disclosed in JP-A-6-111818 and the like.

In general, it is known that the physical properties of the negative electrode mixture have a particularly large effect on the battery characteristics, particularly the specific surface area, and particularly the high-rate charge / discharge characteristics and the high-temperature storage characteristics of the battery. However, the case of a mixture of mesophase graphite and vapor grown carbon fiber is no exception. In terms of high-rate charge / discharge characteristics and low-temperature cycle characteristics, the larger the specific surface area, the larger the reaction area, and the smaller the polarization, which is advantageous. On the other hand, in terms of high-temperature cycle characteristics and high-temperature storage characteristics, the smaller the specific surface area, the smaller the reaction area.
This is advantageous because the decomposition of the electrolytic solution due to side reactions is reduced.

For this reason, conventionally, when mesophase graphite is used alone as a negative electrode mixture, the particle size and specific surface area are controlled.
Its use is disclosed in JP-A-7-134988 and the like. Also, regarding the physical property values for using the vapor-grown carbon fiber alone as the negative electrode mixture, see JP-A-6-84517.
However, in the past disclosed technologies, physical properties of a mixture of mesophase graphite and vapor-grown carbon fiber have not been studied in detail.

On the other hand, when the battery is used in a small laptop computer, which is a main use of the battery, the temperature inside the device rises due to the heat generated from the circuit of the device.
The built-in battery will be used at a high temperature of about 35-45 ° C. Also, considering the use of mobile phones, which is another major application, charging in cold regions in winter,
It is assumed that both discharges are at a low temperature of about 0 ° C.

[0010]

However, in the past disclosed techniques, the evaluation of the cycle characteristics does not consider the ambient temperature of the battery. Therefore, it was not always possible to obtain sufficient cycle characteristics under the actual use conditions at various temperatures as described above.

The present invention has been made to solve such a problem, and has an excellent mixture of graphite powder and graphitic carbon fiber in an appropriate ratio to provide excellent high-temperature cycle characteristics and low-temperature cycle characteristics. And a non-aqueous electrolyte secondary battery.

[0012]

In order to solve the above problems, the present invention comprises a positive electrode comprising a lithium-containing oxide, a negative electrode comprising a mixture of graphite powder and graphitic carbon fiber, and a non-aqueous electrolyte. By using a mixture of graphite powder and graphitic carbon fiber in a weight ratio of 97: 3 to 80:20 in the negative electrode, a non-aqueous material having excellent high-temperature cycle characteristics and low-temperature cycle characteristics can be obtained. It is intended to provide an electrolyte secondary battery.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be carried out under specific conditions described in each claim, but the reason for leading to the specific conditions will be described in detail below.

The negative electrode in which the mesophase graphite and the vapor grown carbon fiber having the physical properties specified in the claims of the present invention are mixed at a predetermined ratio exhibits extremely excellent characteristics at a wide temperature range from low to high temperatures. The reason is presumed as follows.

The mesophase graphite preferably has an average particle size of 3 μm to 15 μm, more preferably 5 μm to 10 μm.
Those having a size of μm or less are good. If it is smaller than this, the crystallinity of the graphite will be underdeveloped, and only a graphite having a low capacity will be obtained. On the other hand, if it is larger than this, the expansion and shrinkage of each particle due to charge and discharge is very large, which increases the stress applied to the electrode plate. As a result, a mixture that cannot participate in the reaction is produced, which causes a decrease in capacity. The specific surface area is preferably 0.7 m ² / g or more and 5.0 m ² / g or less, and more preferably 2.5 m ² / g or more and 4 m ² / g or less. If it is smaller than this, the polarization at the time of the charge / discharge reaction becomes large, and the capacity is reduced particularly at the time of high-rate discharge or at a low temperature of 0 ° C. or lower. On the other hand, the surface distance (d002) between the 002 planes by the wide-angle X-ray diffraction method is preferably from 3.36 ° to 3.40 °. If the battery is smaller than this, it is difficult to intercalate lithium ions between layers of graphite at the time of charging at a low temperature, and the capacity is remarkably reduced. I can't get it.

The vapor-grown carbon fiber has a specific surface area of 1%.
0 m ² / g or more and 20 m ² / g or less, preferably 14 m ² / g or less.
Those having a range of m ² / g to 17 m ² / g are preferred. Below this value, the resistance of the electrode plate increases, and during charging at low temperatures, lithium ions cannot be intercalated between the graphite layers and metallic lithium precipitates on the negative electrode surface, causing a significant decrease in capacity. Cycle characteristics deteriorate. If it is larger than this, no problem occurs at low temperatures, but 35
At a high temperature of not less than ℃, a side reaction with the electrolyte is apt to occur and gas is generated, or the electrode plate surface is coated with a reaction product with the electrolyte, the reaction area is reduced and the capacity is deteriorated. .

The average fiber diameter (average value of 100 fibers randomly observed with a scanning electron microscope) is not less than 0.1 μm and not more than 0.3 μm.
μm or less is good. If the diameter is smaller than this, it becomes too fine for the mesophase graphite particles, so the effect of improving the strength of the electrode plate or improving the conductivity between the mesophase graphite particles by mixing the vapor grown carbon fiber is provided. Is not sufficient, so that those having sufficient charge / discharge cycle characteristics cannot be obtained. On the other hand, when the thickness is larger than this, the packing density at the time of manufacturing the electrode plate cannot be increased, and only a material having a low capacity can be obtained. In addition, 0 by the wide-angle X-ray diffraction method.
The plane interval (d002) of the 02 plane is 3.36 ° or more and 3.4.
0 ° or less is good. Those smaller than this make it difficult for lithium ions to intercalate between graphite layers during charging at low temperatures, resulting in a significant reduction in capacity.
The crystallinity of graphite is underdeveloped, the amount that can intercalate lithium ions decreases, and only low-capacity ones can be obtained, or when used in a high-temperature atmosphere, cause side reactions with the electrolyte. This leads to a decrease in capacity and a decrease in high-rate discharge characteristics.

The mixing ratio of the mesophase graphite and the vapor grown carbon fiber is 97: 3 to 80:20, preferably 95: 5 to 90:10, by weight. If the amount of vapor-grown carbon fiber is larger than this, the packing density at the time of manufacturing the electrode plate cannot be increased, and only a low-capacity carbon fiber can be obtained. If the number of vapor grown carbon fibers is less than this, the effect of improving the strength of the electrode plate or improving the conductivity between the mesophase graphite particles cannot be sufficiently obtained.

As a method for producing a vapor-grown carbon fiber, as disclosed in JP-A-5-221622, a carbon compound such as benzene, methane or carbon monoxide and a catalyst such as iron or nickel are used. It can be obtained by heating the contained organic transition metal compound to 800 to 1300 ° C. in a carrier gas such as hydrogen. At this time, the diameter and length of the obtained vapor grown carbon fiber change depending on the temperature and time. Further, this is carried out in an inert atmosphere at 2400 to 300
Graphite is formed by heat treatment at 0 ° C., preferably 2600 to 2900 ° C., but the specific surface area can be changed by the heat treatment time.

The reason is presumed as follows. That is, the graphitization of the vapor-grown carbon fiber is carried out by a heat treatment for 10 minutes or more to obtain 002 by wide-angle X-ray diffraction.
The plane spacing (d 002) of the planes becomes 3.40 ° or less, and proceeds to a necessary and sufficient extent. When exposed to a high-temperature atmosphere for a longer period of time, it is considered that carbon evaporates from the surface of the vapor-grown carbon fiber, fine cracks occur, and the specific surface area gradually increases.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022]

(Embodiment 1) FIG. 1 is a longitudinal sectional view of a cylindrical battery used in this embodiment. In FIG. 1, reference numeral 1 denotes a battery case formed by processing a steel plate having resistance to an organic electrolyte, 2 denotes a sealing plate provided with a safety valve, and 3 denotes an insulating packing. Reference numeral 4 denotes an electrode group, in which a positive electrode and a negative electrode are spirally wound a plurality of times via a separator and inserted into the battery case 1. A positive electrode lead 5 is drawn out from the positive electrode and connected to the sealing plate 2, and a negative electrode lead 6 is drawn out from the negative electrode and connected to the bottom of the battery case 1. Reference numeral 7 denotes an insulating ring provided on the upper and lower portions of the electrode plate group 4, respectively. Less than,
The positive electrode plate, the negative electrode plate and the like will be described.

For the positive electrode, acetylene black and polytetrafluoroethylene dispersion are mixed with LiCoO ₂ powder synthesized by mixing Li ₂ Co ₃ and Co ₃ O ₄ and calcining at 900 ° C. to form a carboxymethyl cellulose aqueous solution. Into a paste. This paste is applied on both sides of an aluminum foil having a thickness of 0.03 mm, dried, and rolled to obtain a thickness of 0.19 mm, a width of 40 mm, and a length of 25.
A 0 mm electrode plate was used. The negative electrode was manufactured as follows.

A mixture of mesophase graphite and vapor-grown carbon fiber in a weight ratio of 93: 7 is mixed by a mixer (for example, a hybridizer: manufactured by Noboru Nara Machinery Co., Ltd.), and then styrene / butadiene rubber dispersion is mixed. And suspended in an aqueous solution of carboxymethyl cellulose to form a paste.

Then, this paste is applied to a thickness of 0.02 mm.
Coated on both sides of copper foil, dried and rolled to a thickness of 0.20
It was an electrode plate having a width of 0.22 mm, a width of 42 mm, and a length of 285 mm.

A lead was attached to each of the positive electrode plate and the negative electrode plate, spirally wound through a polyethylene separator, and inserted into a battery case 1 having a diameter of 14.0 mm and a height of 50 mm. The electrolytic solution includes ethylene carbonate (hereinafter abbreviated as EC) and diethylene carbonate (hereinafter abbreviated as EC).
DEC) at a volume ratio of 40:60, and a solution prepared by dissolving 1 mol / L of LiPF ₆ in the solvent was injected, and the container was sealed.

The mesophase graphite was obtained as follows. The coal pitch was heat-melted at 390 ° C. and separated and extracted from the pitch matrix by centrifugation to produce mesophase microspheres. Next, carbonization was performed at 1000 ° C. in an inert gas atmosphere, and graphitization was performed at 2800 ° C. After that, the average particle size was 6 μm using an air classifier.
(The particle size distribution is measured by a laser diffraction particle size distribution analyzer:
(Performed by Shimadzu SALD-2000). The specific surface area of the obtained mesophase graphite is 3.2 m ² / g.
(The specific surface area was measured by a BET one-point method measuring apparatus: Nikkiso Co., Ltd. Model 4200 Microtrac Betasoap automatic surface area meter), and the surface spacing (d002) of 002 by wide-angle X-ray diffraction method was 3 .363 °.

The vapor grown carbon fiber was obtained as follows. A carbon compound of benzene and an organic transition metal compound containing iron as a catalyst are mixed in a hydrogen carrier gas in a hydrogen carrier gas.
The mixture was heated to 000 ° C. to obtain a vapor grown carbon fiber. This was heat-treated at 2800 ° C. in an inert atmosphere to be graphitized. In this case, the specific surface area by changing the time for heat treatment to obtain those from 8m ² / g of 25 m ² / g. The fiber diameter of the obtained vapor-grown carbon fiber was 1 with a scanning electron microscope.
As a result of observing 00 lines and taking the average, 0.2 μm was obtained.
385.

Using the mixture of mesophase graphite and vapor-grown carbon fiber, a battery was prepared by the above-described method. A battery having a specific surface area of 8 m ² / g was designated as Battery A, and a battery having a specific surface area of 10 m ² / g was designated as Battery B. 14m cell C things ² / g, the battery D things ^{17m 2 / g, 20m 2 /} g cell E things, 25 m ² /
g was designated as battery F. Next, tests were performed using these batteries under the following conditions.

The charging is performed by a constant current and constant voltage method, and the voltage is set to 4.1.
V and the maximum current were limited to 350 mA for 3 hours, and a charge / discharge cycle in which discharging was performed at 100 mA to 3.0 V by a constant current method was repeatedly performed in an environment of 45 ° C, 20 ° C, and 0 ° C. FIG. 2 shows the results of the test performed under the environment of 45 ° C.
FIG. 3 shows the results obtained under the environment of FIG. 3, and FIG. 4 shows the results obtained under the environment of 0 ° C.

As shown in FIG. 3, under the environment of 20 ° C., there is almost no difference in the cycle characteristics with any of the vapor grown carbon fibers. However, as shown in FIG. 2, in the environment of 45 ° C., the cycle deterioration of the battery F is earlier than that of the batteries A to E. When the internal resistance of the battery after the end of the cycle was measured, it was found that the battery F increased in comparison with the other batteries. When these batteries were disassembled, in battery F, gas presumably generated by the decomposition of the electrolytic solution during the charge / discharge cycle was ejected from the inside. In the battery F, what is considered to be a decomposition product of the electrolytic solution is attached between the negative electrode plate and the separator, and the negative electrode plate and the separator cannot be separated, and the negative electrode mixture and the copper foil are separated. Was. FIG.
As shown in the figure, under the environment of 0 ° C., the initial capacity becomes lower as the specific surface area of the vapor grown carbon fiber decreases,
In particular, the initial capacity of the battery A is significantly lower than that of the other batteries, and the cycle characteristics are poor. After the test, the battery was disassembled and the surface of the negative electrode plate was observed.
In this case, metallic lithium was deposited on the entire surface.

Example 2 In obtaining vapor-grown carbon fibers, the heating time of a carbon compound of benzene and an organic transition metal compound containing iron as a catalyst in a carrier gas of hydrogen was changed to change the fiber diameter. Of 0.06 μm, 0.2 μm and 1.0 μm. Other than that, batteries were prepared in the same manner as in Example 1, and were designated as Battery G, Battery H, and Battery I, respectively. The results of evaluating the charge / discharge cycle characteristics at 20 ° C. under the same conditions as in Example 1 are shown in FIG. Show.

As shown in FIG. 5, the capacity of the battery I was low from the beginning of the charge / discharge cycle because the chargeability of the negative electrode mixture was lower than that of the batteries G and H. Battery G
The initial capacity of the battery H was almost the same as that of the battery H, but the capacity was significantly reduced as the cycle was repeated.

Example 3 A mesophase graphite having an average particle size of 2.3 μm, a specific surface area of 7.3 m ² / g and an average particle size of 20 μm was used.
m and a specific surface area of 0.6 m ² / g except that a battery was prepared in the same manner as the battery D of Example 1 to obtain a battery J and a battery K, respectively, and charged and discharged under the same conditions as in Example 1. FIG. 6 shows the results of evaluating the cycle characteristics at 45 ° C., and FIG. 7 shows the results of the evaluation at 0 ° C.

As shown in FIG. 7, although the charge / discharge cycle characteristics at 0 ° C. are improved in the battery J as compared with the battery K, the cycle characteristics at 45 ° C. are considerably reduced as shown in FIG. ing. In the battery K, the charge / discharge cycle characteristics at 0 ° C. are lower in capacity than in the initial stage.

From the above examples, the volume average particle diameter of the mesophase graphite is 3 μm or more and 15 μm or less, and BE
The specific surface area measured by the T method is 0.7 m ² / g or more and 5.0 m ² / g or less, the 002 plane spacing (d 002) is 3.36 ° or more and 3.40 ° or less by the wide-angle X-ray diffraction method, The grown carbon fiber has a surface area of 10 m ² / g or more and 20 m ² / g or less and a mean fiber diameter of 0.1 μm or more and 0.3 μm or less measured by a BET method, and has a 002 plane spacing (d) obtained by wide-angle X-ray diffraction. 002) is 3.3
Using a mixture of not less than 6 ° and not more than 3.40 °, the mixing ratio of mesophase graphite and vapor-grown carbon fiber is 9 by weight.
By setting the ratio to 7: 3 to 80:20, good cycle characteristics can be obtained both at low and high temperatures.

In this embodiment, EC and DE are used as electrolytes.
A solution in which 1 mol / liter of LiPF ₆ was dissolved in a solvent in which C was mixed at a volume ratio of 40:60 was used. However, the present invention is not limited to this, and a conventionally known one can be used. However, when a graphite material is used for the negative electrode as in the present invention, propylene carbonate (hereinafter abbreviated as PC) is not preferable because it undergoes a decomposition reaction at the time of charging and tends to accompany gas generation. An E
It can be said that C is suitable because it hardly involves side reactions as in the case of PC. However, EC has a very high melting point and is solid at room temperature, so that it is difficult to use it with a single solvent. Therefore, it is preferable to use a mixed solvent in which an aliphatic carboxylic acid ester such as 1,2-dimethoxyethane or DEC which is a solvent having a low melting point and a low viscosity is mixed. As the Li salt dissolved in these solvents, any conventionally known ones such as lithium hexafluorophosphate, lithium borofluoride, lithium hexafluoroarsenate and lithium perchlorate can be used.

On the other hand, the cathode contains a compound containing lithium ions.
LiCoO_Two, LiNiO _Two, LiNiCoO
_Two, LiFeO_Two, LiMn_TwoO_FourEtc. are available
You. The composite oxide is, for example, charcoal of lithium or cobalt.
Salts or oxides as raw materials, depending on the desired composition
They can be easily obtained by mixing and firing.
Wear. Of course, the same applies when other raw materials are used.
Can be achieved. Among them, LiCoO_TwoAre compared for chargeable / dischargeable capacity
Large and chemically stable in the electrolyte.
You. Usually, the firing temperature is set between 650 and 1200 ° C.
Is determined.

Although LiCoO ₂ was used for the positive electrode in this embodiment, other than the above, LiNiO ₂ , LiNiCo
When O ₂ , LiFeO ₂ , and LiMn ₂ O ₄ were used, almost the same effect was obtained although a slight difference in capacity was observed.

[0040]

As is apparent from the above description, as the graphite powder used for the negative electrode, the volume average particle diameter of mesophase graphite is 3 μm or more and 15 μm or less, and 0.7 m ² / g or more in the specific surface area measurement by the BET method. 5.0 m ² / g
In the following, the plane distance (d) of the 002 plane by the wide-angle X-ray diffraction method will be described.
002) is not less than 3.36 ° and not more than 3.40 °, and the vapor grown carbon fiber has a specific surface area of 10
m ² / g or more 20 m ² / g or less, preferably 14m ² / g
Not less than 17 m ² / g and an average fiber diameter of 0.1
μm or more and 0.3 μm or less, and 0 according to the wide-angle X-ray diffraction method.
The plane spacing (002) of the 02 planes is 3.36 ° or more and 3.40 °
By using a mixture in which the mixing ratio of mesophase graphite and vapor-grown carbon fiber is 97: 3 to 80:20 by weight, polarization during low temperature charging and decomposition of electrolyte during high temperature cycling, etc. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery having a high capacity, a high energy density, and excellent cycle characteristics in actual use because the side reaction can be reduced.

The control of the specific surface area of the vapor grown carbon fiber is performed during the graphitization time in the examples, but is not necessarily limited to this method. For example, a method of changing the particle size by classification or the like may be used. good.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical battery according to an embodiment of the present invention.

FIG. 2 is a diagram showing cycle characteristics in an environment of 45 ° C. in Example 1.

FIG. 3 is a diagram showing cycle characteristics under an environment of 20 ° C. in Example 1.

FIG. 4 is a diagram showing cycle characteristics in an environment of 0 ° C. in Example 1.

FIG. 5 is a diagram showing cycle characteristics under an environment of 20 ° C. in Example 2.

FIG. 6 is a view showing cycle characteristics in an environment of 45 ° C. in Example 3.

FIG. 7 is a diagram showing cycle characteristics in an environment of 0 ° C. in Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulation packing 4 Electrode group 5 Positive electrode lead 6 Negative electrode lead 7 Insulation ring

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shusaku Goto 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] A positive electrode comprising a lithium-containing oxide, a negative electrode comprising a mixture of graphite powder and graphitic carbon fibers, and a non-aqueous electrolyte, wherein the negative electrode comprises graphite powder and graphitic carbon fibers. The mixing ratio is 97: 3 to 80:20 by weight.
A non-aqueous electrolyte secondary battery characterized by the following. 2. Graphite powder is obtained by graphitizing mesophase spheres produced by heat-treating pitch, has a volume average particle diameter of 3 μm to 15 μm, and is 0.7 m ² / g in specific surface area measurement by BET method. 5.0
^2. The non-aqueous electrolyte secondary according to claim 1, wherein the distance between the 002 planes (d 002) measured by wide-angle X-ray diffraction is not less than 3.36 ° and not more than 3.40 °. battery. 3. The graphitic carbon fiber is obtained by graphitizing a vapor-grown carbon fiber obtained by pyrolyzing a hydrocarbon gas, and has a specific surface area of 10 m ² / ^b measured by a BET method.
g to 20 m ² / g and the average fiber diameter is 0.1
μm or more and 0.3 μm or less, and the plane spacing (d 002) of the 002 plane by wide angle X-ray diffraction is 3.36 ° or more and
The non-aqueous electrolyte secondary battery according to claim 1, wherein the angle is 40 ° or less.