JP2002124255A - Nonaqueous solvent secondary battery - Google Patents

Nonaqueous solvent secondary battery

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Publication number
JP2002124255A
JP2002124255A JP2000311973A JP2000311973A JP2002124255A JP 2002124255 A JP2002124255 A JP 2002124255A JP 2000311973 A JP2000311973 A JP 2000311973A JP 2000311973 A JP2000311973 A JP 2000311973A JP 2002124255 A JP2002124255 A JP 2002124255A
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JP
Japan
Prior art keywords
non
secondary battery
mesophase pitch
aqueous solvent
negative electrode
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Pending
Application number
JP2000311973A
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Japanese (ja)
Inventor
Takatsugu Fujiura
Hitoshi Sakamoto
Koichi Sugano
Hirotaka Tsuruya
斉 坂本
公一 菅野
隆次 藤浦
浩隆 鶴谷
Original Assignee
Mitsubishi Gas Chem Co Inc
三菱瓦斯化学株式会社
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Application filed by Mitsubishi Gas Chem Co Inc, 三菱瓦斯化学株式会社 filed Critical Mitsubishi Gas Chem Co Inc
Priority to JP2000311973A priority Critical patent/JP2002124255A/en
Publication of JP2002124255A publication Critical patent/JP2002124255A/en
Pending legal-status Critical Current

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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/12Battery technologies with an indirect contribution to GHG emissions mitigation
    • Y02E60/122Lithium-ion batteries

Abstract

(57) [Summary] [PROBLEMS] When a graphite material is used for a negative electrode of a non-aqueous solvent secondary battery, a high discharge capacity and high charge / discharge efficiency are realized, and at the same time, a good electrode structure is improved while improving electrode filling properties. Can be secured, PC
The present invention provides a negative electrode capable of using an electrolyte solution containing, and enables the production of a lithium ion secondary battery having a large capacity and excellent rate characteristics, cycle stability, and low-temperature characteristics. A mesophase pitch is used as a raw material.
A non-scale graphite powder produced by graphitization at a temperature of not less than ℃, wherein the optical structure is a mosaic structure, and the plane spacing d of crystallites in the C-axis direction in X-ray diffraction.
002 is 0.3358 nm or more, crystallite size Lc 002 is 100 nm or less, 136 in Raman scattering spectrum.
A lithium salt was dissolved in a negative electrode using a graphite powder in which the intensity ratio (I1360 / I1580) of two Raman bands of 0 and 1580 cm -1 was 0.1 or more as a carbon material, and a nonaqueous solvent containing propylene carbonate. A non-aqueous solvent secondary battery using an electrolytic solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous solvent secondary battery such as a lithium ion secondary battery having a large capacity and excellent rate characteristics, cycle stability, and low-temperature characteristics.

[0002]

2. Description of the Related Art A lithium ion secondary battery using a carbon material for a negative electrode has a high voltage, a high energy density, and excellent safety and cycle characteristics. As a power source for electronic devices, practical use has recently been rapidly progressing.

As a carbon material for the negative electrode, graphite, hardly graphitizable carbon (hard carbon), coke, and the like are used. In particular, graphite materials such as natural graphite and artificial graphite have the advantage that they have higher crystallinity than other carbon materials, have a higher discharge capacity, and have an extremely high true density, so that the packing density of the electrodes can be increased. ing. However, if a graphite material is used for the negative electrode,
Propylene carbonate (hereinafter referred to as PC), which has a low melting point, a high dielectric constant, and a high electrical conductivity even at low temperatures, has a disadvantage that it cannot be used due to decomposition during charging.
As a result, the lithium ion secondary battery using the graphite material for the negative electrode is compared with the lithium ion secondary battery using the non-graphitizable carbon for the negative electrode in which the electrolyte containing PC can be used.
The problem is that the rate characteristics and the low-temperature characteristics are inferior.

A negative electrode material using graphite having a very high crystallinity, such as natural graphite, has a high discharge capacity, but is flaky and bulky, and has poor dispersibility in a binder at the time of preparing the negative electrode. As a result, problems such as peeling off and non-uniformity occur, and it is difficult to obtain a good electrode structure, which is a factor of shortening the cycle life of the lithium ion secondary battery. Therefore, further improvement of the electrode filling property is required by improving the shape of the filling powder. As an example of a carbon material that responds to such an improvement in the filling property, spherical mesocarbon microbeads (MCMB) can be cited. However, MCMB has a very low yield at the time of production and is expensive. Not enough.

[0005]

Accordingly, a negative electrode made of a non-scale graphite material having a high discharge capacity, a high charge / discharge efficiency and a good filling property, and an electrolytic solution obtained by dissolving a lithium salt in a non-aqueous solvent containing PC. There is a demand for a lithium ion secondary battery having a large capacity and excellent rate characteristics, cycle stability, and low-temperature characteristics.

An object of the present invention is to overcome the problem that an electrolytic solution containing PC is decomposed when a graphite material is used for a negative electrode, to realize a high discharge capacity and a high charge / discharge efficiency, and to enhance electrode filling. At the same time, a negative electrode made of non-scale graphite powder capable of securing a good electrode structure is provided.
By combining an electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent containing C, it is possible to manufacture a lithium ion secondary battery having a large capacity and excellent rate characteristics, cycle stability, and low-temperature characteristics. .

[0007]

Means for Solving the Problems The present inventors have attempted to solve the above-mentioned problem that an electrolyte containing PC is decomposed during charging and discharging of a carbon material for a negative electrode of a non-aqueous solvent secondary battery using mesophase pitch as a raw material. As a result of intensive study, a non-scaly graphite powder having a specific structure in X-ray diffraction and Raman scattering spectrum, which is obtained by graphitizing the mesophase pitch at 2000 ° C. or higher, contains PC. It has been found that PC is not decomposed in charge and discharge in an electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent. Furthermore, since these graphite powders exhibit a high discharge capacity and a high charge / discharge efficiency, a large capacity and composed of an electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent containing a negative electrode made of the graphite material and PC. The present inventors have found that a lithium ion secondary battery having excellent rate characteristics, cycle stability, and low-temperature characteristics can be manufactured, and have reached the present invention.

That is, the present invention relates to a non-scale graphite powder produced by graphitizing a mesophase pitch as a raw material at a temperature of 2000 ° C. or more, wherein the optical structure is a mosaic structure, The plane spacing d 002 of the crystallites in the axial direction is 0.3358 nm or more, the crystallite size Lc 002 is 100 nm or less, and the intensity ratio (I1360 / I1580) of the two Raman bands of 1360 and 1580 cm −1 in the Raman scattering spectrum is 0.1
A negative electrode using the graphite powder as a carbon material,
A non-aqueous solvent secondary battery using an electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent containing propylene carbonate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The raw mesophase pitch used in the present invention can be any of petroleum, coal and synthetic mesophase pitches. Softening point of mesophase pitch by flow tester method is 150
C. or higher, those having an optical anisotropy content of 50% or more based on observation with a polarizing microscope and a carbonization yield of 70% or more are preferable.
Here, the carbonization yield means that the mesophase pitch powder is heated (10 ° C./min) in an inert gas atmosphere,
This is a numerical value when the temperature is maintained for 2 hours after the temperature reaches ° C. In such a mesophase pitch, a condensed polycyclic hydrocarbon such as naphthalene, methylnaphthalene, anthracene, phenanthrene, acenaphthene, acenaphthylene, or pyrene is polymerized in the presence of hydrogen fluoride / boron trifluoride as a super strong acid catalyst. The resulting synthetic mesophase pitch exhibits high chemical purity, is excellent in graphitization, and has an extremely high carbonization yield and is suitably used.

Next, two methods for preparing a carbon material for a negative electrode that can be used in the present invention from a mesophase pitch will be described below.

In the first method, 400 in a non-oxidizing atmosphere.
Granular or powdered mesophase pitch heat-treated product is charged and stirred in advance in a reactor kept at a temperature range of ~ 800 ° C, and mesophase pitch is added thereto. Manufactured.
In this method, the added mesophase pitch is first turned into a low-viscosity liquid by heating, and is dispersed on the surface of a previously prepared granular or powdered mesophase pitch heat-treated product (hereinafter referred to as a return medium). After that, the polymerization reaction by heat progresses, and finally changes into an infusible heat-treated product.
Since the return medium is always kept in a fluid state by stirring, the gas generated by the reaction of the mesophase pitch is quickly discharged out of the system, and the heat treatment can be efficiently performed in a small-volume reactor. Further, the mesophase pitch is dispersed on the surface of the return medium and polymerization proceeds, and solidifies while being subjected to shear by the flow of the return medium, so that the optical structure of the obtained heat-treated product has a mosaic structure.

The reactor used here is a tank-type reactor provided with a stirrer which can sufficiently stir a granular or powdery mesophase pitch heat-treated product, or a cylindrical reactor having a stirrable paddle. , Or a rotary kiln can be used. When a row reactor is used, a reactor such as that described in JP-A-7-286181, in which the rotating shaft of the stirring blade is installed at an angle, can be used.

The heat-treated mesophase pitch is pulverized after cooling to near room temperature. The pulverization conditions are selected such that the average particle size of the powder is usually in the range of 1 to 50 μm, preferably 2 to 30 μm. The pulverized carbonaceous powder is usually calcined before the graphitization treatment. However, the calcining step may be omitted and the graphitization treatment may be performed immediately after the pulverization. Generally, the calcination step is performed in a non-oxidizing atmosphere at 800 to 160
Performed at 0 ° C. The powder thus obtained is non-scale-like and almost maintains the shape at the time of the pulverization process. Further, this powder is heated to 2000 ° C. or more, preferably 2500 ° C.
By performing the graphitization treatment at a temperature of not less than ℃, a graphite powder having a non-scale mosaic structure can be obtained.

In the second method, the mesophase pitch is set to 20.
After shaping into a thread through a nozzle at 0 ° C to 400 ° C,
This is a method of manufacturing by infusibilizing, pulverizing, and then graphitizing at 2000 ° C. or higher. There is no particular limitation on the apparatus for shaping into a thread shape, but a spinning machine capable of pressure spinning, centrifugal spinning and the like is used. The shape and size of the nozzle are not particularly limited, but in the case of pressure spinning, the inner diameter is from 0.1 mm to 0.4 mm.
And a ratio L / D of the nozzle diameter to the length of about 1 to 10 is used. The spinning is generally performed at a temperature higher by about 70 ° C. to 120 ° C. than the softening point by the flow tester method, and is formed into a pitch yarn of 10 μm to 20 μm. The pitch yarn is made infusible in an oxidizing atmosphere, then carbonized and graphitized at 2000 ° C. or higher. Usually, after the infusibilizing treatment or the carbonizing treatment, the powder is pulverized so that the particle size of the powder is usually in the range of 1 to 50 μm, preferably 2 to 30 μm. Thus, a graphite powder having a non-scale mosaic structure is obtained.

The graphite powder prepared by the above two methods is
The plane spacing d 002 of crystallites in the C-axis direction in X-ray diffraction is 0.3358 nm or more, and the crystallite size Lc is 100 n.
m or less, and 1360 in the Raman scattering spectrum.
And the intensity ratio of the two Raman bands at 1580 cm -1 (I
1360 / I1580) is 0.1 or more. By introducing a mosaic structure into the graphite material, the growth of the extreme crystal size is suppressed. As a result, the crystal size Lc in the C-axis direction becomes 100 nm or less. It is also reported that the intensity ratio of the Raman band (I1360 / I1580) is generally correlated with the amount of graphite crystal edges exposed on the surface of the graphite powder, and the Raman band is exposed by controlling this value to 0.1 or more. The amount of the edge surface is relatively increased. Such a graphite material does not cause decomposition of PC in charge and discharge in an electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent containing PC,
Since it exhibits high discharge capacity and high charge / discharge efficiency, it is composed of a negative electrode made of the graphite material and an electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent containing PC, and has a large capacity and rate characteristics, cycle stability, and A lithium ion secondary battery having excellent low-temperature characteristics can be manufactured.

The negative electrode used in the present invention is obtained by kneading the above-mentioned carbon material with a binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), a solvent and the like to form a negative electrode mixture. It is produced by applying and drying a copper or stainless steel foil as a current collector.

The non-aqueous solvent used in the present invention is preferably a solvent composed of a combination of a high dielectric constant solvent and a low viscosity solvent. As the high dielectric constant solvent, for example, ethylene carbonate (EC), propylene carbonate (P
C) and cyclic carbonates such as butylene carbonate (BC) are usually suitably used, but in the present invention, 10% by volume of the high dielectric constant solvent contained in the electrolytic solution is used.
The above is characterized by using a PC having a low melting point, a high dielectric constant, and a high electric conductivity even at a low temperature.
The content of PC in the high dielectric constant solvent is preferably 2
0 vol% or more, and more preferably 40 vol% or more. The high dielectric constant solvent components other than PC include the above-described EC,
BC or the like is used alone or in combination of two or more.

Examples of the low-viscosity solvent include dimethyl carbonate (DMC) and methyl ethyl carbonate (M
Chain carbonates such as EC) and diethyl carbonate (DEC); ethers such as tetrahydrofuran, 1,4-dioxane and 1,2-dimethoxyethane; γ-
Lactones such as butyl lactone; nitriles such as acetonitrile; esters such as methyl propionate;
Amides such as dimethylformamide are exemplified. These low-viscosity solvents may be used alone or in combination of two or more. The high dielectric constant solvent and the low viscosity solvent are arbitrarily selected and used in combination. The high-dielectric solvent and the low-viscosity solvent are usually used in a volume ratio (high-dielectric solvent: low-viscosity solvent) of about 1: 9 to 4: 1.

The electrolyte used in the present invention includes, for example, LiPF 6 , LiBF 6 , LiClO 4 , LiN (S
O 2 CF 3 ) 2 and the like. These electrolytes may be used alone or in combination of two or more. These electrolytes are used after being dissolved in the above non-aqueous solvent at a concentration of usually 0.1 to 3 mol / l, preferably 0.5 to 1.5 mol / l.

As the positive electrode material used in the present invention, for example, a composite metal oxide of at least one metal selected from the group consisting of cobalt, manganese, chromium, nickel, iron and vanadium and lithium is used. You.
Examples of such a composite metal oxide include LiCo.
O 2 , LiMn 2 O 4 , LiNiO 2 and the like can be mentioned. The positive electrode is made by kneading the positive electrode material of the previous period with a conductive agent such as acetylene black and carbon black, a binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), and a solvent to form a positive electrode mixture. It is produced by coating and drying on aluminum or stainless steel foil as a current collector.

The structure of the lithium secondary battery is not particularly limited, and generally includes a coin-type battery having a positive electrode, a negative electrode, and a single-layer or multi-layer separator, and further has a positive electrode, a negative electrode, and a roll-shaped separator. Examples include a cylindrical battery and a square battery. As the separator, a microporous polyolefin membrane, a woven fabric, a nonwoven fabric, or the like is used. Further, a gel separator and an electrolyte in which an electrolyte solution composed of the above-mentioned electrolyte and a solvent containing PC is impregnated with a polymer such as polyacrylonitrile or polyethylene oxide can also be used.

[0022]

The present invention will be more specifically described below with reference to examples and comparative examples. However, the present invention is not limited by these examples.

Example 1 Naphthalene was polymerized in the presence of hydrogen fluoride and boron trifluoride to form a mesophase pitch (softening point: 235 ° C., optical anisotropy content: 100%,
(Carbonization yield: 87%). In order to heat-treat the pitch, the temperature was raised to 530 ° C. at 5 ° C./min in a nitrogen atmosphere,
This temperature was maintained for one hour. After cooling to room temperature, the product was pulverized to obtain a mesophase pitch heat-treated product having an average particle size of about 0.5 mm. Next, a diameter 1 equipped with a stirrer
200 g of this heat-treated product was previously charged as a return medium into a 70 mm, 170 mm height tank reactor, and the temperature was raised to 550 ° C. in a nitrogen stream while stirring. Here, the mesophase pitch is added to the reactor at a rate of 10 g per minute,
A total of 300 g was charged. After charging, 10 at 550 ° C
After holding for 1 minute, the reactor was cooled and the contents were taken out to obtain 400 g of a granular heat-treated product. The same operation was repeated seven times using 200 g of the resultant as the next returning medium to obtain a mesophase pitch heat-treated product having a replacement ratio of about 99%. The optical structure of this heat-treated product is almost 100%
Mosaic organization. Since this heat-treated product does not melt when it is graphitized, the mosaic structure does not essentially change even if it is graphitized by the following operation. The obtained heat-treated product was subjected to an impact-type pulverizer to obtain an average particle size of 15 μm.
Crushed. Observation of this pulverized product using an electron microscope revealed that the powder was round, rounded and nearly spherical. The powder was heated at 5 ° C./min in a nitrogen atmosphere,
After reaching 00 ° C., the temperature was held for 10 minutes to perform calcination. At this time, no melting of the particles or adhesion between the particles was observed. Subsequently, a graphitization treatment was performed at 3000 ° C. in an argon atmosphere. The powder thus obtained had a mosaic structure, and almost kept the non-scaly shape at the time of pulverization. Further, as a result of analyzing the crystal structure of the graphite powder by an X-ray diffraction method, the (002) plane crystallite spacing d 002 was 0.3359 nm, and the crystallite size Lc 002 was 8
It was 0 nm. 136 in Raman scattering spectrum
The intensity ratio (I1360 / I1580) of the two Raman bands at 0 and 1580 cm −1 was 0.17. To 90 parts by weight of the obtained carbon material, 10 parts by weight of a polyvinylidene fluoride powder (binder) was added, mixed and mixed with dimethylformamide as a solvent, applied to a copper foil, dried, cut into 1 cm squares, and evaluated. Test piece. Then, LiPF 6 was converted to propylene carbonate / ethylene carbonate / methyl ethyl carbonate (PC / EC /
A solution (concentration: 1.2 mol / l) dissolved in a mixed solvent having a volume ratio of (MEC) of 1/1/4 was used as an electrolytic solution, and a thickness of 50 μm was used.
A half cell using a polypropylene microporous membrane of m as a separator was produced. As a counter electrode, lithium metal having a diameter of 16 mm and a thickness of 0.5 mm was used. A small piece of lithium metal was used as a reference electrode in the same manner as the counter electrode. Constant current charging was performed at a current density of 0.2 mA / cm 2 until the electrode potential of the test piece for evaluation with respect to the reference electrode became 10 mV. Next, when a constant current discharge was performed at a current density of 0.2 mAh / cm 2 until the electrode potential of the test piece for evaluation with respect to the reference electrode was 1.5 V, the charge capacity was 336 mAh / g, and the discharge capacity was 315 mAh / g. The charge / discharge efficiency was 94%.

Example 2 The same carbon material as in Example 1 was used, and LiPF 6 was used in PC / EC /
When a solution (concentration: 1.2 mol / l) dissolved in a mixed solvent having a MEC capacity ratio of 2/1/5 was used as an electrolyte, the lithium battery negative electrode performance of this carbon material was measured.
42 mAh / g, the discharge capacity is 310 mAh / g,
The charge / discharge efficiency was 91%.

Example 3 Naphthalene was polymerized in the presence of hydrogen fluoride and boron trifluoride to form a mesophase pitch (softening point: 235 ° C., optical anisotropy content 100%,
(Carbonization yield: 87%). The pitch has an inner diameter of 0.1
The mixture was placed in a spinning machine equipped with a single-hole nozzle having a diameter / length of 5 mm and a ratio L / D of 4 and formed into a 12-micron pitch yarn at 320 ° C. 7 g of the pitch yarn was charged into a hot air circulating furnace, heated from 150 ° C. to 270 ° C. at a rate of 1.5 ° C./min in air, and taken out to complete infusibility. The obtained infusible yarn was subjected to ball milling to obtain an average particle size of 15
Milled to μm. The temperature of the powder was increased at a rate of 5 ° C./min in a nitrogen atmosphere. At this time, no melting of the particles or adhesion between the particles was observed. The particle shape remained fibrous and was non-scaled. The optical texture was almost 100% mosaic texture.
Subsequently, a graphitization treatment was performed at 3000 ° C. in an argon atmosphere. The powder thus obtained had a mosaic structure, and kept almost non-scale-like shape as it was. Further, as a result of analyzing the crystal structure of the graphite powder by an X-ray diffraction method, the (002) plane crystallite spacing d 002 was obtained.
Is 0.3361 nm, and the crystallite size Lc 002 is 46 n.
m. The intensity ratio of the two Raman bands at 1360 and 1580 cm -1 in the Raman scattering spectrum (I1
(360 / I 1580) was 0.17. As in Example 1, LiPF 6 was used when the capacity ratio of PC / EC / MEC was 1
/ 1/4 solution (concentration 1.2mol)
/ l) was used as an electrolyte, and the negative electrode performance of this carbon material was measured. The charge capacity was 318 mAh / g, the discharge capacity was 305 mAh / g, and the charge / discharge efficiency was 96%.
Met.

Example 4 The same carbon material as in Example 3 was used except that LiPF 6 was used in PC / EC /
When a solution (concentration: 1.2 mol / l) dissolved in a mixed solvent having a MEC capacity ratio of 2/1/5 was used as an electrolyte, the lithium battery negative electrode performance of this carbon material was measured.
31 mAh / g, the discharge capacity is 307 mAh / g,
The charge / discharge efficiency was 93%.

Comparative Example 1 In order to heat-treat the same mesophase pitch as that used in Example 1, the temperature was raised to 530 ° C. at 5 ° C./min in a nitrogen atmosphere and kept at this temperature for 1 hour. After cooling to room temperature, it was pulverized by a jet mill to an average particle size of 15 μm. When this pulverized product was observed using an electron microscope,
Although it was a non-flaky powder, the optical structure was almost 100% flowing. The temperature of the powder was increased at a rate of 5 ° C./min in a nitrogen atmosphere. At this time, no melting of the particles or adhesion between the particles was observed. Subsequently, a graphitization treatment was performed at 3000 ° C. in an argon atmosphere. After the graphitization, the non-flaky powder was maintained, but the optical structure was almost 100% flowing. As a result of analyzing the crystal structure of the graphite powder by the X-ray diffraction method, the (002) plane spacing d 002 between crystallites was 0.3.
356nm, size Lc 002 of the crystallite was 250nm. 1360 and 15 in Raman scattering spectrum
The intensity ratio of two Raman bands at 80 cm -1 (I1360
/ I1580) was 0.06. As in Example 1, LiPF 6 was replaced with a PC / EC / MEC capacity ratio of 1/1.
Solution dissolved in a mixed solvent of / 4 (concentration: 1.2 mol / l)
Was used as an electrolyte to measure the negative electrode performance of this carbon material on a lithium battery. As a result, the charge capacity was 625 mAh / g, the discharge capacity was 305 mAh / g, and the charge / discharge efficiency was as low as 49%.

Comparative Example 2 The same mesophase pitch as used in Example 1 was heated at a rate of 5 ° C./min to 530 ° C. in a nitrogen atmosphere and kept at this temperature for 1 hour. After cooling to room temperature, it was coarsely pulverized to a size of several mm. Next, 5 ° C./min in a nitrogen atmosphere
And calcined by holding for 10 minutes after reaching 1000 ° C.
Subsequently, a graphitization treatment was performed at 3000 ° C. in an argon atmosphere. The graphitized coarse powder was pulverized by a jet mill to an average particle size of 15 μm. Although the intensity ratio (I1360 / I1580) of the two Raman bands at 1360 and 1580 cm -1 in the Raman scattering spectrum of this graphite powder was 0.23, it was a scale-like powder, and the optical structure was almost 100% flowing. Met. As a result of analyzing the crystal structure of the graphite powder by an X-ray diffraction method, the (002) plane crystallite spacing d 002 was 0.3357 nm, and the crystallite size Lc 002 was 220 nm. As in Example 1, LiPF 6 was replaced with a PC / EC / MEC capacity ratio of 1/1.
Solution dissolved in a mixed solvent of / 4 (concentration: 1.2 mol / l)
Was used as an electrolytic solution, and the lithium battery negative electrode performance of this carbon material was measured. As a result, the charge capacity was 473 mAh / g, the discharge capacity was 329 mAh / g, and the charge / discharge efficiency was as low as 70%.

[0029]

As described in detail above, according to the present invention,
Overcoming the problem that the electrolyte containing PC decomposes when using the graphite material for the negative electrode, achieves high discharge capacity and high charge / discharge efficiency, and improves the electrode filling property and at the same time secures a good electrode structure. Thus, a graphite powder having a non-scale-like shape is obtained. A negative electrode using this graphite powder and PC
By using an electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent containing, a lithium ion secondary battery having a large capacity and excellent in rate characteristics, cycle stability, and low-temperature characteristics can be manufactured.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hitoshi Sakamoto 22nd Wadai, Tsukuba, Ibaraki Prefecture F-term in Mitsubishi Gas Chemical Company, R & D Co., Ltd. (Reference) AM04 AM05 AM07 CJ02 CJ28 DJ16 DJ17 HJ13 HJ14 5H050 AA06 AA07 AA08 BA17 CA08 CA09 CB08 EA10 EA24 FA17 FA19 GA02 GA05 GA27 HA13 HA14

Claims (4)

[Claims]
1. A mesophase pitch of 2000
A non-scale graphite powder produced by graphitization at a temperature of not less than ℃, wherein the optical structure is a mosaic structure, and the plane spacing d of crystallites in the C-axis direction in X-ray diffraction.
002 is 0.3358 nm or more, crystallite size Lc 002 is 100 nm or less, 136 in Raman scattering spectrum.
A lithium salt was dissolved in a negative electrode using a graphite powder in which the intensity ratio (I1360 / I1580) of two Raman bands of 0 and 1580 cm -1 was 0.1 or more as a carbon material, and a nonaqueous solvent containing propylene carbonate. A non-aqueous solvent secondary battery using an electrolytic solution.
2. The method according to claim 1, wherein the graphite powder is 400 to 8 in a non-oxidizing atmosphere.
A mesophase pitch heat-treated product in the form of granules or powder is charged in a reactor at 00 ° C in advance, mesophase pitch is added with stirring, and the mesophase pitch heat-treated product obtained by heat treatment is crushed, and then 2,000 ° C or more. 2. The non-aqueous solvent secondary battery according to claim 1, wherein the non-aqueous solvent secondary battery is obtained by graphitization.
3. The graphite powder has a mesophase pitch of 200.
The non-aqueous solvent secondary battery according to claim 1, wherein the non-aqueous solvent secondary battery is obtained by shaping into a thread shape through a nozzle at ~ 400 ° C, infusibilizing and pulverizing, and then graphitizing at 2000 ° C or higher.
4. The non-aqueous solvent according to claim 1, wherein the mesophase pitch is obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride / boron trifluoride. Rechargeable battery.
JP2000311973A 2000-10-12 2000-10-12 Nonaqueous solvent secondary battery Pending JP2002124255A (en)

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Cited By (6)

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WO2011049199A1 (en) 2009-10-22 2011-04-28 昭和電工株式会社 Graphite material, carbonaceous material for battery electrodes, and batteries
JP2011084429A (en) * 2009-10-15 2011-04-28 Osaka Gas Co Ltd Carbon material, and method for producing carbon material and graphite material
JP2012114201A (en) * 2010-11-24 2012-06-14 Nec Tokin Corp Power storage device
WO2012144618A1 (en) 2011-04-21 2012-10-26 昭和電工株式会社 Graphite/carbon mixed material, carbon material for battery electrodes, and battery
WO2012144617A1 (en) 2011-04-21 2012-10-26 昭和電工株式会社 Graphite material, carbon material for battery electrode, and battery
US10177380B2 (en) 2013-12-20 2019-01-08 Lg Chem, Ltd. Anode active material and lithium secondary battery including the same

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011084429A (en) * 2009-10-15 2011-04-28 Osaka Gas Co Ltd Carbon material, and method for producing carbon material and graphite material
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