WO1998053511A1 - Carbonaceous material for the anode of lithium ion secondary cell and lithium ion secondary cell made by using the carbonaceous material - Google Patents

Carbonaceous material for the anode of lithium ion secondary cell and lithium ion secondary cell made by using the carbonaceous material Download PDF

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Publication number
WO1998053511A1
WO1998053511A1 PCT/JP1998/002127 JP9802127W WO9853511A1 WO 1998053511 A1 WO1998053511 A1 WO 1998053511A1 JP 9802127 W JP9802127 W JP 9802127W WO 9853511 A1 WO9853511 A1 WO 9853511A1
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Prior art keywords
carbon material
negative electrode
boron
silicon
lithium ion
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PCT/JP1998/002127
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French (fr)
Japanese (ja)
Inventor
Haruo Sakagoshi
Akihito Sasaki
Udai Tanaka
Masayuki Ito
Tadashi Takeuchi
Hiroshi Okubo
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Toyo Tanso Co., Ltd.
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Publication of WO1998053511A1 publication Critical patent/WO1998053511A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a carbon material for a negative electrode of a lithium ion secondary battery using a carbon material as a negative electrode active material, and a lithium ion secondary battery using the carbon material for a negative electrode.
  • Conventional technology a carbon material for a negative electrode of a lithium ion secondary battery using a carbon material as a negative electrode active material, and a lithium ion secondary battery using the carbon material for a negative electrode.
  • the L i C o C 2, etc. as the positive electrode active material has been practically Richiumui ion secondary battery using a carbon material in the negative electrode active material.
  • One of the keys to realizing a smaller and lighter lithium-ion secondary battery is the carbon material for the negative electrode. Therefore, the search for new and useful carbon materials for negative electrodes is under way.
  • the characteristics required of the carbon material for the negative electrode include an increase in the doping amount, that is, the initial capacity, an improvement in the initial efficiency, which is a ratio between the undoped amount and the doping amount, and a discharge capacity after the predetermined cycle and the initial cycle. This is an improvement in cycle characteristics, which is a ratio with respect to the discharge capacity.
  • Japanese Unexamined Patent Publication Nos. Hei 5-25010, Hei 5-26 680, Japanese Unexamined Patent Publication No. Hei 5-292904, Hei 8-3-1422 Discloses a carbon material containing boron as a carbon material for a negative electrode.
  • this negative electrode carbon material is effective in increasing the initial capacity.
  • the improvement of the initial efficiency and the improvement of the cycle characteristics are not enough, and it has not been put to practical use.
  • Japanese Unexamined Patent Application Publication Nos. Hei 8-2-25913, Hei 8-23 6104, and Japanese Patent Laid-Open Publication No. Hei 8-231273 disclose the use of silicon as a carbon material for a negative electrode.
  • a carbon material is disclosed.
  • the carbon material for negative electrode has an effect of increasing the initial capacity, the improvement of the initial efficiency and the improvement of the cycle characteristics are insufficient, and the carbon material has not been put to practical use. Summary of the Invention
  • An object of the present invention is to provide a carbon material for a negative electrode of a lithium ion secondary battery having a large initial capacity and excellent initial efficiency and cycle characteristics, and a lithium ion secondary battery using the carbon material for a negative electrode.
  • the present invention has solved and solved the above-mentioned problems by using a carbon material containing boron and silicon for a negative electrode.
  • the product of the present invention exhibits an improvement in initial efficiency and cycle characteristics in addition to an increase in initial capacity, as compared with a conventional boron-containing or silicon-containing carbon material.
  • carbon contains a boron element and a silicon element, and the content of the boron element is preferably 1 to 20% by weight.
  • this boron element is a graphitization catalyst, the crystallization of carbon progresses too much and the wettability decreases, making it difficult to form a lithium secondary battery negative electrode sheet. It may be. As a result, the adhesion to the copper foil as the current collector may be poor. Therefore, when the boron element and the silicon element are contained in carbon, the carbon material for the negative electrode of a lithium ion secondary battery, which has been subjected to one of the following processes (1) to (3) or a combination of two or more thereof, may be used. it can. Thereby, the adhesion to the copper foil can be improved.
  • a lithium ion secondary battery formed using the above-described carbon material for a negative electrode as a negative electrode active material exhibits excellent characteristics such as an increase in initial capacity, an increase in initial efficiency, and an improvement in cycle characteristics.
  • FIG. 1 is a view showing the discharge capacity and the initial efficiency of the negative electrode materials for lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 and 2.
  • FIG. 2 is a diagram showing the improvement in wettability of the negative electrode materials for lithium secondary batteries according to Examples 4 to 8 and Comparative Examples 3 to 6.
  • FIG. 3 is a diagram showing a charge / discharge curve as a material for a negative electrode of a lithium secondary battery according to Example 2 (f) and Comparative Example 2 (a).
  • FIG. 5 shows the size of the lithium secondary battery negative electrode material according to Example 2 (f) and Comparative Example 2 (a) obtained by performing CV measurement while changing the scanning speed in a scanning range of 3 to O OV. It is a figure showing a click voltammogram.
  • FIG 6 is a diagram showing the relationship between the fifth peak obtained from FIG current (i p) and the scanning speed of the square root (v 1/2).
  • FIG. 7 is an exploded perspective view showing one embodiment of the lithium secondary battery according to the present invention.
  • FIG. 8 is a diagram showing the cycle efficiency of the lithium secondary batteries according to Examples 9 to 16 and Comparative Examples 7 to 9.
  • a raw material carbon material such as pitch coke, petroleum coke, graphite, etc., whose particle size has been adjusted as necessary, is combined with a boron or boron compound and a silicon or silicon compound. Is added and mixed. This is packed in, for example, a graphite crucible and heat-treated. The heat treatment temperature is finally set to 240 ° C. or higher.
  • the obtained heat-treated carbon material is adjusted to a required particle size by a predetermined treatment such as pulverization and classification to obtain a desired carbon material for a lithium secondary battery negative electrode. It was confirmed that the boron element in the obtained carbon material was present as boron carbide, and the silicon element in the obtained carbon material was present as silicon carbide.
  • usable carbon materials include carbon black, raw coke, pitch, synthetic resin, etc. in addition to the above, and there is no particular limitation, but it is desirable that the weight loss during heat treatment is not so remarkable.
  • the additive can be a boron compound other than B (boron), B 4 C, BN, ⁇ 2 0 3, ⁇ ⁇ 5, ⁇ 3 ⁇ 0 3 and the like.
  • Beta_ ⁇ boron oxides such as 3, the moderate oxidation during the heat treatment, the fine pores are formed, one flop de lithium
  • a carbon material having a crystal structure that can further enhance the de-doping effect can be obtained.
  • the amount of boron or boron compound added is such that the abundance ratio as a boron element in the carbon material after the heat treatment falls within the range of 1 to 20% by weight. If the amount is less than 1% by weight, it is difficult to expect the promotion of graphitization, while if it exceeds 20% by weight, a large amount of boron carbide is mixed in the graphitized carbon material after the heat treatment, and the carbonization of the carbonized material becomes large. This is because the merit of adding boron is offset by the negative influence of boron, and it is difficult to expect improvement in battery performance. More preferable addition of boron or boron compound is 1% by weight or more and 5% by weight as a boron element in the carbon material after heat treatment. Less than / 0 .
  • S i C, S i O include S i 0 2 or the like.
  • the abundance as a silicon element in the carbon material after the heat treatment is 0.1 to 1 to 20% by weight. It is desirable that the addition amount be within the range of / 0 . If the content is less than 0.01% by weight, it is difficult to expect the effect of the addition of silicon, that is, the improvement in cycle characteristics and initial efficiency. On the other hand, if the content exceeds 20% by weight, a large amount of carbon As with boron carbide, the benefits of adding silicon are offset by the negative effects of the silicon carbide, making it difficult to expect improved battery performance. In addition, more preferable addition of silicon or silicon compound is such that the abundance ratio as silicon element in the carbon material after heat treatment is 0.01 wt. / 0 or more, 5 weight. Less than / 0 .
  • the reason why the final heat treatment temperature is set to 240 ° C. or higher is that boron does not easily diffuse in the plane of the carbon hexagonal network at 240 ° C. or lower.
  • Another example of the production method of the present invention is as follows. First, various cokes, artificial graphite, etc., whose particle size has been adjusted as required, are used as aggregates, and a binder such as pitch and boron or a boron compound (1 to 20% by weight in terms of boron after heat treatment) and cake are added. After adding silicon or a silicon compound (0.01 to 20% by weight in silicon conversion after heat treatment), kneading is performed. After adjusting the particle size of the obtained kneaded material as necessary, it is formed into an appropriate block by cold isostatic pressing (CIP method) or the like, and this block is placed in a reducing atmosphere or an inert gas atmosphere. Heat treatment at a temperature of 240 ° C.
  • CIP method cold isostatic pressing
  • a desired carbon material for a negative electrode of a lithium secondary battery by adjusting the particle size by a predetermined treatment such as pulverization and classification.
  • a predetermined treatment such as pulverization and classification.
  • examples of the aggregate include various cokes such as pitch coke, petroleum cocoa, raw pitch coke, and raw petroleum coke, as well as carbon black, artificial graphite, and natural graphite.
  • examples of the binder include pitch, synthetic resin, and the like. There is no particular limitation, but a binder that does not significantly reduce the weight during heat treatment is preferable.
  • the addition of boron or boron compounds and silicon or silicon compounds is not limited to the stage of the kneading process, and may be added to the kneaded material after molding before molding.
  • the atmosphere can be formed by a gas generated from a binder pitch, or an argon gas, a helium gas, or the like.
  • a CVR method or a CVD method can be used as a method of mixing boron and silicon into a carbon material.
  • the carbon material may be a compact or a powder.
  • these boron and silicon are distributed particularly in the surface layer.
  • the carbon material into which boron and silicon are incorporated is preferably a graphite material from the viewpoint of battery characteristics.
  • S i ⁇ as Kei originally Motogen, S i 0 2, and S i C can be performed using the S i H and the like.
  • the carbon material for a negative electrode of the present invention has good adhesion to a copper foil as a current collector, and can further improve battery productivity and battery performance.
  • the carbon material for a negative electrode of the present invention is basically an improved material of a carbon material containing an appropriate amount of boron, but at the same time, is also an improved material that also includes a specific negative factor caused by containing boron. I can say.
  • boron which is also a graphitizing catalyst, tends to promote crystallization by all means, making it difficult to avoid a decrease in wettability.
  • the graphitized carbon material whose raw carbon material has been finally graphitized is finally adjusted to the particle size by pulverization and classification, and then commercialized.
  • the particle size adjustment is not selected based on the criteria that take wettability into account, many particles (products) within the specified range after the particle size adjustment include many that do not actually have good wettability. ing.
  • the microscopic observation of the particle shape after particle size adjustment shows that the particles are not smooth but rough, and that the surface has fine particles that cannot be removed by classification.
  • boron and silicon are mixed by a CVD method or a CVR method with a carbon material previously graphitized by heat treatment or a graphite material such as natural graphite or artificial graphite
  • the carbon material (block-shaped or powdered) ) Is mixed with boron and silicon by CVD or CVR, and then the carbon material is impregnated or coated with pitch or resin and fired (about 700-1500 ° C), and then the particle size is adjusted. I just need.
  • the second treatment there is a treatment for selecting, from the graphitized carbon powder after the particle size adjustment, those having relatively good wettability.
  • a graphitized carbon powder containing a boron element and a silicon element having a bulk density of 0.5 (g / cm 3 ) or more and an oil absorption of 100 (m 1 Z 100 g) or less is selected. Measures are effective.
  • the boron-containing graphite can be excellent in the wettability with the binder, and therefore, can be excellent in the adhesiveness with the copper foil after the slurry.
  • the packing density at the time of sheeting is increased, the weight of the active material that can be filled in the same container can be increased, and thus a battery with a large capacity can be manufactured.
  • the graphitized carbon powder has a particle size distribution of 5-20 rn for 10% D, 10-35 ⁇ for 50% D, and 30-65 m for 90% D.
  • the specific surface area of the graphitized powder can be reduced and the safety can be improved, and the packing density at the time of sheeting can be increased.
  • a treatment for removing fine particles from the graphitized carbon powder after particle size adjustment and smoothing the powder surface there is a treatment for removing fine particles from the graphitized carbon powder after particle size adjustment and smoothing the powder surface.
  • a phosphoric acid H 3 P_ ⁇ 4, H. P 2 0 7 , (HP 0 3) r,, ⁇ 4 ⁇ 2 0 6, ⁇ 3 Ro_ ⁇ 3, ⁇ 3 ⁇ 0 2 like phosphorus
  • a typical example is an aqueous solution of an oxygen acid of formula (I), but there is no particular limitation as long as it is basically a compound containing ⁇ , ⁇ and ⁇ .
  • the heat treatment temperature may be any temperature at which the phosphoric acid evaporates, and is generally preferably 700 ° C. or higher.
  • the above processes 1 to 3 can be repeated.
  • (1) the carbon powder that has been treated can be subjected to (2) particle size adjustment in the treatment, and (3) phosphoric acid can be added in the treatment.
  • (2) the particle size of the treatment can be adjusted, and additionally, (3) phosphoric acid can be added.
  • the boron element and the silicon element are contained by the 0 method or the 1 method after the carbon powder is formed, it is preferable that at least one of the treatments 2 and 3 is performed. Note that the above treatments (1) to (3) can be applied not only to carbon powder containing boron and silicon elements but also to carbon powder containing only boron.
  • Lithium secondary batteries have a combination of a positive electrode, a negative electrode and a separator with a non-aqueous electrolyte, or a combination of an organic or inorganic solid electrolyte as a positive electrode, a negative electrode and a separator with a non-aqueous electrolyte. It is not limited.
  • lithium-conoult composite oxide As the active material of the positive electrode, but lithium-cobalt-based composite oxide, lithium nickel or lithium Manganese-based active materials such as spinel-type lithium manganese oxides, such as manganese-based composite oxides and titanium disulfide, or various host materials such as vanadium pentoxide and molybdenum trioxide that can absorb and release lithium. Can be used.
  • the organic solvent is not fundamentally limited. Conventionally, the same effects as those of the present invention can be obtained as long as they are used in lithium secondary batteries.
  • solvents such as propylene carbonate, ethylene carbonate, ⁇ -butyrolactone, and sulfolane can be used in solvents having a high dielectric constant such as 1,2-dimethoxetane, dimethyl carbonate, ethylmethylcarbonate, getylcarbonate, and methylformate.
  • a mixture of low-viscosity solvents can be used.
  • a lithium ion conductive solid electrolyte for example, an organic solid electrolyte such as PAN or an inorganic solid electrolyte such as lithium titanate may be used alone or in combination with an organic solvent.
  • the batteries may be of any shape, such as prismatic, cylindrical, coin-shaped or paper-shaped.
  • the particle size was adjusted to 20 m to obtain carbon materials (a) to (h) in Example 2 and carbon materials (a) to (e) in Comparative Example 2 as shown in FIG.
  • the carbon material containing boron and silicon elements is less than the general graphitic carbon material that does not contain both boron and silicon elements and the carbon material that contains only boron. It can be seen that both initial efficiency and discharge capacity are excellent.
  • the effect of improving the initial efficiency and the discharge capacity is further increased. I understand.
  • Block artificial graphite (bulk density 1.8 g / cm 3 , average pore radius 1.5 ⁇ m) was impregnated with pitch in advance and fired at 1200 ° C.
  • the obtained block was pulverized to an average particle size of 20 ⁇ m and the particle size was adjusted.
  • the artificial graphite powder obtained, using B 2 ⁇ 3 as the element boron source 1 8 CVR treatment was performed at normal pressure under an argon atmosphere of 00 ° C.
  • the resulting material, Kei originally performed normal pressure CVR process using S i 0 2 at 2000 ° C as Motogen, Hong resulting graphitized carbon powder adhesion test between the copper foil described later did.
  • the powder obtained by the same production method as in Example 2 (g) was subjected to particle size adjustment, the powder bulk density was 0.75 (g / cm 3 ), and the oil absorption was 67 (m 1/100 g).
  • a graphitized carbon powder having a particle size distribution of 7111 for 10% 0, 20111 for 50% 0, and 58111 for 90% 0 was obtained and subjected to an adhesion test with a copper foil described later.
  • the oil absorption refers to the value measured by the method A (mechanical method) specified in JI SK6221 “Test method for carbon black for rubber” Section 6.1.1.
  • the Pitchiko one box adjusted particle size to an average particle size 30 w m, the C and the elemental boron source, the S i 0 2 as Kei originally Motogen, so the ratio is the same as in Example 1 (c) Added and mixed. These mixtures were packed in graphite crucibles, heat-treated (graphitized) at 2600 ° C in an Acheson furnace, and then adjusted to an average particle size of 20 / m. The resulting graphitized powder 100 parts by weight of phosphoric acid (H 3 P_ ⁇ ) was added thoroughly mixed 30 parts by weight. The graphitized powder whose surface was moistened with phosphoric acid was packed in a graphite crucible and heat-treated at 1200 ° C. The obtained powder was subjected to an adhesion test with a copper foil described later. (Comparative Example 6)
  • the graphitized carbon powder obtained before the addition of phosphoric acid obtained in Example 1 (c) was subjected to an adhesion test with a copper foil described later.
  • Example 7 in which the powder bulk density and the oil absorption amount satisfy the requirements of the present invention and the particle size distribution is also appropriate, the same good results as in Examples 4 to 6 can be obtained.
  • Example 8 which was subjected to phosphoric acid addition and heat treatment, almost no peeling was observed.
  • Comparative Example 6 which was not subjected to phosphoric acid addition and heat treatment, peeled considerably.
  • FIG. 3 shows, as representative examples, charge / discharge curves of the negative electrode material of the lithium secondary battery of Example 2 (f) and Comparative Example 2 (a). From Fig. 1, it can be seen that the carbon material containing boron and silicon has lower initial efficiency and discharge capacity than the general graphite carbon material that does not contain both boron and silicon and the carbon material that contains only boron. It can be seen that is also excellent. Further, it can be seen that in the case of Examples 1 to 3 in which the contents of boron and silicon are in the specific ranges of the present invention, the effects of improving the initial efficiency and the discharge capacity are further enhanced.
  • Example 2 (f) the lithium secondary battery negative electrode material containing boron and silicon obtained in Example 2 (f) is compared with Comparative Example 2 (a) (a conventional graphite-based negative electrode material). Therefore, while having the potential flatness of about 0.25V [VVsLi / Li], which is an advantage of the conventional graphite material, and 1.3V [VVsLi / Li] From the above, it can be clearly seen that the discharge capacity of 1% or more of the discharge capacity up to 0.25 V makes the lithium secondary battery negative electrode material resistant to overdischarge.
  • a peak was observed at around 1.2 V in the anode direction and at around 1.4 V in the force sword direction, and this peak was observed in Comparative Example 2 (a). I understand that there is no.
  • the scanning speed V was 0.5 CmV Zs], 0.3 [mVZs], 0.1 [mVZs], 0.
  • FIG. 7 shows an exploded perspective view of the lithium secondary battery according to the present invention.
  • 1 is a lithium secondary battery
  • 2 is an electrode group
  • 3 is a positive electrode plate
  • 4 is a negative electrode plate
  • 5 is a separator
  • 6 is a battery case
  • 7 is a case lid
  • 8 is a safety valve
  • 10 is a positive electrode terminal
  • 1 1 Is a positive electrode lead.
  • the configuration of the lithium secondary battery 1 is a prismatic lithium secondary battery in which a spiral electrode group 2 composed of a positive electrode plate 3, a negative electrode plate 4, a separator 5, and a non-aqueous electrolyte is housed in a battery case 6.
  • the battery case 6 is made of an iron body with a thickness of 0.3 mm and an inner dimension of 33.1 x 46.5 x 7.5 mm with a nickel plating of 5 ⁇ m on the surface. Is provided with a hole 100 for injecting an electrolytic solution.
  • the current collector is an aluminum foil having a thickness of 20 ⁇ m. It is a substance holding lithium cobalt composite oxide as a substance.
  • the positive electrode plate 3 is prepared by mixing 8 parts of polyvinylidene fluoride as a binder and 5 parts of acetylene black as a conductive agent with 87 parts of an active material to prepare a paste, and then applying the paste to both surfaces of a current collector material It was prepared by drying.
  • Comparative Example 7 The one using the graphite powder described in Comparative Example 2 (b) of FIG. 1 is referred to as Comparative Example 7.
  • Comparative Example 8 the same manufacturing method was used except that the presence or absence of boron or silicon was the same as that used in Example 8.
  • a graphite element containing boron was used as a comparative example 8, and a graphite powder containing only silicon was used. Is referred to as Comparative Example 9.
  • Separators one data 5, microporous polyethylene membrane, also electrolyte, L i PF 6 to 1 mo 1/1 containing ethylene carbonate: dimethyl carbonate ne Ichito 1: Using a mixture of 1 (volume ratio).
  • the positive electrode plate 3 is connected to the terminal 10 of the case lid 7 provided with the safety valve 8 and the positive electrode terminal 10 via the positive electrode lead 11.
  • the negative electrode plate 4 is connected by contact with the wall of the battery case 6. Then, this battery is sealed by laser welding the lid 7 to the case 6.
  • the electrolyte volume was 25 m 1.
  • the batteries of No. 16 had a first cycle capacity of 860-89 OmAh, while the batteries of Comparative Examples 7-9, which did not contain either boron element or silicon element, had no initial cycle capacity. 840-85 OmAh. In the comparison of the first cycle only, Examples 9 to 16 are only slightly better than Comparative Examples 7 to 9.
  • the carbon material for a negative electrode of a lithium ion secondary battery of the present invention and the lithium ion secondary battery using the carbon material for a negative electrode have the above-described configuration, the initial capacity is large, and the initial efficiency and the cycle characteristics are excellent.

Abstract

A carbonaceous material for the anode of a lithium ion secondary cell, which comprises carbon, 1 to 20 % by weight of boron and 0.01 to 20 % by weight of silicon; and a lithium ion secondary cell made by using the carbonaceous material as the anode active material. The secondary cell exhibits excellent characteristics such as an increased initial capacity, an increased initial efficiency and improved cyclic characteristics.

Description

明 細 書 リチウムイオン二次電池負極用炭素材料及びその負極用炭素材料を用い たリチウムイオン二次電池 技術分野  Description Carbon material for negative electrode of lithium ion secondary battery and lithium ion secondary battery using the carbon material for negative electrode
本発明は、 負極活物質として炭素材料を使ったリチウムイオン二次電 池負極用炭素材料及びその負極用炭素材料を用いたリチウムイオン二次 電池に関する。 従来の技術  The present invention relates to a carbon material for a negative electrode of a lithium ion secondary battery using a carbon material as a negative electrode active material, and a lithium ion secondary battery using the carbon material for a negative electrode. Conventional technology
近年の電気 ·電子機器の小型軽量化に伴い、 小型軽量で高エネルギー 密度の二次電池の開発が急がれている。 この開発の成果として、 L i C o C 2 等を正極活物質とし、 炭素材料を負極活物質に用いたリチウムィ オン二次電池が実用化されている。 With the recent reduction in the size and weight of electric and electronic devices, the development of small and lightweight secondary batteries with high energy density is urgently required. As a result of this development, the L i C o C 2, etc. as the positive electrode active material, has been practically Richiumui ion secondary battery using a carbon material in the negative electrode active material.
このリチウムイオン二次電池の小型軽量化を実現させるための鍵の一 つを負極用炭素材料が握っている。 そのため、 新規で有用な負極用炭素 材料の探索が進められている。  One of the keys to realizing a smaller and lighter lithium-ion secondary battery is the carbon material for the negative electrode. Therefore, the search for new and useful carbon materials for negative electrodes is under way.
この負極用炭素材料に求められる特性は、 ドープ量すなわち初期容量 の増大と、 脱ドープ量と ド一プ量との比率である初期効率の向上と、 所 定サイクル後の放電容量と初回サイクル時の放電容量との比率であるサ ィクル特性の向上である。  The characteristics required of the carbon material for the negative electrode include an increase in the doping amount, that is, the initial capacity, an improvement in the initial efficiency, which is a ratio between the undoped amount and the doping amount, and a discharge capacity after the predetermined cycle and the initial cycle. This is an improvement in cycle characteristics, which is a ratio with respect to the discharge capacity.
特開平 5— 2 5 1 0 8 0号公報、 特開平 5— 2 6 6 8 8 0号公報、 特 開平 5— 2 9 9 0 8 4号公報、 特開平 8— 3 1 4 2 2号公報には、 負極 用炭素材料として、 ホウ素を含有する炭素材料が開示されている。 しか しながら、 この負極用炭素材料は、 初期容量の増大に効果が認められる ものの、 初期効率の向上とサイクル特性の向上が不十分であり、 実用化 に至っていない。 Japanese Unexamined Patent Publication Nos. Hei 5-25010, Hei 5-26 680, Japanese Unexamined Patent Publication No. Hei 5-292904, Hei 8-3-1422 Discloses a carbon material containing boron as a carbon material for a negative electrode. However, this negative electrode carbon material is effective in increasing the initial capacity. However, the improvement of the initial efficiency and the improvement of the cycle characteristics are not enough, and it has not been put to practical use.
特開平 8— 2 5 9 2 1 3号公報、 特開平 8— 2 3 6 1 0 4号公報、 特 開平 8— 2 3 1 2 7 3号公報には、 負極用炭素材料として、 ケィ素を含 有する炭素材料が開示されている。 しかしながら、 この負極用炭素材料 は、 初期容量の増大に効果が認められるものの、 初期効率の向上とサイ クル特性の向上が不十分であり、 実用化に至っていない。 発明の要約  Japanese Unexamined Patent Application Publication Nos. Hei 8-2-25913, Hei 8-23 6104, and Japanese Patent Laid-Open Publication No. Hei 8-231273 disclose the use of silicon as a carbon material for a negative electrode. A carbon material is disclosed. However, although the carbon material for negative electrode has an effect of increasing the initial capacity, the improvement of the initial efficiency and the improvement of the cycle characteristics are insufficient, and the carbon material has not been put to practical use. Summary of the Invention
本発明の目的は、 初期容量が大きく、 初期効率及びサイクル特性に優 れたリチウムイオン二次電池負極用炭素材料及びその負極用炭素材料を 用いたリチウムイオン二次電池を提供することである。  An object of the present invention is to provide a carbon material for a negative electrode of a lithium ion secondary battery having a large initial capacity and excellent initial efficiency and cycle characteristics, and a lithium ion secondary battery using the carbon material for a negative electrode.
本発明は、 ホウ素及びケィ素を含有する炭素材料を負極に用いること により、 上記課題を解決し、 完成した。 本発明品は、 従来のホウ素含有 又はケィ素含有の炭素材料に比較して、 初期容量の増大に加えて、 初期 効率の向上及びサイクル特性の向上を発揮する。  The present invention has solved and solved the above-mentioned problems by using a carbon material containing boron and silicon for a negative electrode. The product of the present invention exhibits an improvement in initial efficiency and cycle characteristics in addition to an increase in initial capacity, as compared with a conventional boron-containing or silicon-containing carbon material.
すなわち、 本発明は、 炭素にホウ素元素とケィ素元素を含有させてな り、 好ましくは、 前記ホウ素元素の含有量を 1〜 2 0重量。んとし、 前記 ゲイ素の含有量を 0 . 0 1〜2 0重量％としたリチウムイオン二次電池 負極用炭素材料である。 炭素にホウ素元素とケィ素元素を含有させる手 段は二つある。 一つは、 原料炭素材料にホウ素源及びケィ素元素源を添 加した混合物を熱処理する。 もう一つは、 原料炭素材料を先に熱処理し た後、 ホゥ素源及びケィ素元素源を C V D法又は C V R法を利用して添 加して、 炭素にホウ素元素及びケィ素元素を含有させる手段である。 このホウ素元素は黒鉛化触媒であるため、 炭素の結晶化が進み過ぎて 濡れ性が低下し、 リチウム二次電池負極板にするためのシ一ト化が困難 になることがある。 その結果、 集電体である銅箔との密着性が不良とな ることがある。 そこで、 炭素にホウ素元素とケィ素元素を含有させる際 に、 下記の①〜③のいずれか一つの処理又は二以上の組合せ処理が施さ れたリチウムィオン二次電池負極用炭素材料とすることができる。 これ により、 銅箔との密着性を改善することができる。 That is, in the present invention, carbon contains a boron element and a silicon element, and the content of the boron element is preferably 1 to 20% by weight. A carbon material for a negative electrode of a lithium ion secondary battery in which the content of the above-mentioned gay element is 0.01 to 20% by weight. There are two ways to make carbon contain boron and silicon. One is to heat-treat a mixture in which a boron source and a silicon element source are added to a raw carbon material. Second, after the raw carbon material is heat-treated first, a boron source and a silicon element source are added using a CVD method or a CVR method, so that the carbon element contains the boron element and the silicon element. Means. Since this boron element is a graphitization catalyst, the crystallization of carbon progresses too much and the wettability decreases, making it difficult to form a lithium secondary battery negative electrode sheet. It may be. As a result, the adhesion to the copper foil as the current collector may be poor. Therefore, when the boron element and the silicon element are contained in carbon, the carbon material for the negative electrode of a lithium ion secondary battery, which has been subjected to one of the following processes (1) to (3) or a combination of two or more thereof, may be used. it can. Thereby, the adhesion to the copper foil can be improved.
① ホウ素元素及びケィ素元素を含有させた炭素材にピッチ又は樹脂 を含浸又はコートして焼成したのち、 粉碎して炭素粉末にする処理。 ① A process of impregnating or coating a carbon material containing boron and silicon elements with pitch or resin, firing and then pulverizing into carbon powder.
② ホウ素元素及びケィ素元素を含有させた炭素粉末を、 粉体嵩密度 が 0. 5 (g/c m3 ) 以上、 且つ吸油量が 1 00 (m l /1 00 g) 以下に調整する処理。 ② Processing to adjust the carbon powder containing boron element and silicon element to have a powder bulk density of 0.5 (g / cm 3 ) or more and an oil absorption of 100 (ml / 100 g) or less.
③ ホウ素元素及びケィ素元素を含有させた炭素粉末にリン酸を添加 したのち熱処理する処理。  ③ Heat treatment after adding phosphoric acid to carbon powder containing boron element and silicon element.
以上説明した負極用炭素材料を負極活物質に用いて形成したリチウム イオン二次電池は、 初期容量の増大と、 初期効率の向上と、 サイクル特 性の向上という優れた特性を発揮する。 図面の簡単な説明  A lithium ion secondary battery formed using the above-described carbon material for a negative electrode as a negative electrode active material exhibits excellent characteristics such as an increase in initial capacity, an increase in initial efficiency, and an improvement in cycle characteristics. BRIEF DESCRIPTION OF THE FIGURES
第 1図は、 実施例 1〜 3と比較例 1〜 2に係るリチウム二次電池負極 用材の放電容量と初期効率を示す図である。  FIG. 1 is a view showing the discharge capacity and the initial efficiency of the negative electrode materials for lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 and 2.
第 2図は、 実施例 4〜 8と比較例 3〜 6に係るリチウム二次電池負極 用材の濡れ性改善を示す図である。  FIG. 2 is a diagram showing the improvement in wettability of the negative electrode materials for lithium secondary batteries according to Examples 4 to 8 and Comparative Examples 3 to 6.
第 3図は、 実施例 2 (f)， 比較例 2 (a)に係るリチゥム二次電池負極用材 としての充放電曲線を示す図である。  FIG. 3 is a diagram showing a charge / discharge curve as a material for a negative electrode of a lithium secondary battery according to Example 2 (f) and Comparative Example 2 (a).
第 4図は、 実施例 2(f), 比較例 2(a)に係るリチウム二次電池負極用材 について、 走査速度を一定 （v = l. 0 [mV/ s ) ) とし、 3V^ ~~ ^ 0Vの走査範囲で CV測定して得られたサイクリックボルタモグラム （ 電流—電位曲線） を示す図である。 FIG. 4 shows that the scanning speed of the negative electrode material for the lithium secondary battery according to Example 2 (f) and Comparative Example 2 (a) was constant (v = l.0 [mV / s)) and 3V ^ ~~ Cyclic voltammogram obtained by CV measurement in ^ 0V scanning range ( FIG. 4 is a diagram showing a current-potential curve).
第 5図は、 実施例 2 (f), 比較例 2 (a)に係るリチウム二次電池負極用材 について、 3 ~~ ^ O Vの走査範囲で走査速度を変えながら C V測定し て得られたサイクリックボルタモグラムを示す図である。  FIG. 5 shows the size of the lithium secondary battery negative electrode material according to Example 2 (f) and Comparative Example 2 (a) obtained by performing CV measurement while changing the scanning speed in a scanning range of 3 to O OV. It is a figure showing a click voltammogram.
第 6図は、 第 5図から得られるピーク電流 （ i p ) と走査速度の平方 根 （v 1 / 2 ) との関係を示す図である。 6 is a diagram showing the relationship between the fifth peak obtained from FIG current (i p) and the scanning speed of the square root (v 1/2).
第 7図は、 本発明に係るリチウム二次電池の一実施形態を示す分解斜 視図である。  FIG. 7 is an exploded perspective view showing one embodiment of the lithium secondary battery according to the present invention.
第 8図は、 実施例 9〜 1 6と比較例 7〜 9に係るリチゥム二次電池の サイクル効率を示す図である。  FIG. 8 is a diagram showing the cycle efficiency of the lithium secondary batteries according to Examples 9 to 16 and Comparative Examples 7 to 9.
発明の詳細な開示 Detailed Disclosure of the Invention
以下、 本発明の負極用炭素材料を、 種々の製法例に基づき詳細に説明 する。  Hereinafter, the carbon material for a negative electrode of the present invention will be described in detail based on various production methods.
( 1 ) まず、 基本的な製法例としては、 必要に応じて粒度調整したピッ チコ一クス、 石油系コークス、 黒鉛等の原料炭素材料に、 ホウ素又はホ ゥ素化合物とケィ素又はケィ素化合物を添加混合する。 これを、 例えば 黒鉛ルツボ等に詰めて熱処理する。 熱処理温度は、 最終的に 2 4 0 0 °C 以上とする。 得られた熱処理済みの炭素材を、 所定の粉砕， 分級等の処 理により必要な粒度に調整して、 所望のリチゥム二次電池負極用炭素材 料を得る。 得られた炭素材料中のホウ素元素は炭化ホウ素となって存在 し、 得られた炭素材料中のケィ素元素は炭化ケィ素となって存在してい ることが確認された。  (1) First, as a basic production method, a raw material carbon material such as pitch coke, petroleum coke, graphite, etc., whose particle size has been adjusted as necessary, is combined with a boron or boron compound and a silicon or silicon compound. Is added and mixed. This is packed in, for example, a graphite crucible and heat-treated. The heat treatment temperature is finally set to 240 ° C. or higher. The obtained heat-treated carbon material is adjusted to a required particle size by a predetermined treatment such as pulverization and classification to obtain a desired carbon material for a lithium secondary battery negative electrode. It was confirmed that the boron element in the obtained carbon material was present as boron carbide, and the silicon element in the obtained carbon material was present as silicon carbide.
上記製法において、 使用可能な炭素材料は、 上記以外に、 カーボンブ ラック、 生コークス等の他ピッチ、 合成樹脂等が挙げられ、 特に制限は ないが、 熱処理時の重量減少があまり著しくないものが望ましい。 B (ホウ素） 以外の添加可能なホウ素化合物としては、 B 4 C， B N , Β 2 03 , Β 〇5 , Η3 Β 03 等が挙げられる。 In the above-mentioned manufacturing method, usable carbon materials include carbon black, raw coke, pitch, synthetic resin, etc. in addition to the above, and there is no particular limitation, but it is desirable that the weight loss during heat treatment is not so remarkable. . The additive can be a boron compound other than B (boron), B 4 C, BN, Β 2 0 3, Β 〇 5, Η 3 Β 0 3 and the like.
このうち、 Β 2 03 ， Β 4 〇5 もしくは Η 3 Β〇3 等のホウ素酸化物 を使用すれば、 熱処理過程で適度の酸化反応により、 微細な気孔が形成 され、 リチウムのド一プ ·脱ド一プ効果をより高め得る結晶組織を有す る炭素材が得られる利点がある。 Among, the use of beta 2 0 3, beta 4 〇 5 or Eta 3 Beta_〇 boron oxides such as 3, the moderate oxidation during the heat treatment, the fine pores are formed, one flop de lithium There is an advantage that a carbon material having a crystal structure that can further enhance the de-doping effect can be obtained.
また、 ホウ素又はホウ素化合物の添加は、 熱処理後の炭素材料におけ るホウ素元素としての存在比が 1〜2 0重量％の範囲内に収まるような 添加量であることが望ましい。 1重量％未満では、 黒鉛化の促進が期待 できにくくなるからであり、 一方 2 0重量％を超えると、 熱処理後の黒 鉛化炭素材料に多量の炭化ホウ素が混在するようになり、 その炭化ホゥ 素によるマイナスの影響分だけホウ素添加によるメリットが相殺され、 電池の性能の向上が期待できにくくなるからである。 なお、 より好まし いホウ素又はホウ素化合物の添加は、 熱処理後の炭素材料におけるホウ 素元素としての存在比が 1重量％以上、 5重量。 /0未満である。 It is desirable that the amount of boron or boron compound added is such that the abundance ratio as a boron element in the carbon material after the heat treatment falls within the range of 1 to 20% by weight. If the amount is less than 1% by weight, it is difficult to expect the promotion of graphitization, while if it exceeds 20% by weight, a large amount of boron carbide is mixed in the graphitized carbon material after the heat treatment, and the carbonization of the carbonized material becomes large. This is because the merit of adding boron is offset by the negative influence of boron, and it is difficult to expect improvement in battery performance. More preferable addition of boron or boron compound is 1% by weight or more and 5% by weight as a boron element in the carbon material after heat treatment. Less than / 0 .
また、 S i (ケィ素） 以外の添加可能なケィ素化合物としては、 S i C , S i O, S i 02 等が挙げられる。 As the additive capable Kei-containing compounds other than S i (Keimoto), S i C, S i O, include S i 0 2 or the like.
このうち、 S i〇， S i〇2 等のケィ素酸化物を使用すれば、 ホウ素 酸化物の添加の場合と同様の効果、 即ち熱処理過程で適度の酸化反応に より、 微細な気孔が形成され、 リチウムのドープ ·脱ドープ効果をより 高め得る結晶組織に転化する効果が得られる。 Among, S I_〇, using the Kei-containing oxide such as S I_〇 2, the same effect as in the case of the addition of boron oxide, i.e. more moderate oxidation during the heat treatment, fine pores formed Thus, an effect of converting into a crystal structure that can further enhance the doping and undoping effects of lithium is obtained.
そして、 ケィ素又はケィ素化合物の添加は、 熱処理後の炭素材料にお けるケィ素元素としての存在比が 0 . ◦ 1〜2 0重量。 /0の範囲内に収ま るような添加量であることが望ましい。 0 . 0 1重量％未満では、 ゲイ 素添加の効果、 即ちサイクル特性及び初期効率の改善が期待できにくく なる。 一方 2 0重量％を超えると、 熱処理後の炭素材料に多量の炭化ケ ィ素が混在するようになり、 炭化ホウ素と同様、 その炭化ケィ素による マイナスの影響分だけケィ素添加によるメリットが相殺され、 電池性能 の向上が期待できにくくなる。 なお、 より好ましいケィ素又はケィ素化 合物の添加は、 熱処理後の炭素材料におけるケィ素元素としての存在比 が 0 . 0 1重量。 /0以上、 5重量。 /0未満である。 When silicon or a silicon compound is added, the abundance as a silicon element in the carbon material after the heat treatment is 0.1 to 1 to 20% by weight. It is desirable that the addition amount be within the range of / 0 . If the content is less than 0.01% by weight, it is difficult to expect the effect of the addition of silicon, that is, the improvement in cycle characteristics and initial efficiency. On the other hand, if the content exceeds 20% by weight, a large amount of carbon As with boron carbide, the benefits of adding silicon are offset by the negative effects of the silicon carbide, making it difficult to expect improved battery performance. In addition, more preferable addition of silicon or silicon compound is such that the abundance ratio as silicon element in the carbon material after heat treatment is 0.01 wt. / 0 or more, 5 weight. Less than / 0 .
また、 最終の熱処理温度として 2 4 0 0 °C以上を条件としたのは、 2 4 0 0 °C以下では、 炭素六角網平面内でホウ素の拡散が起こりにくいか らである。  The reason why the final heat treatment temperature is set to 240 ° C. or higher is that boron does not easily diffuse in the plane of the carbon hexagonal network at 240 ° C. or lower.
( 2 ) さらに、 本発明の他の製法例は、 次のとおりである。 まず、 必要 に応じて粒度調整した種々のコークスゃ人造黒鉛等を骨材とし、 これに ピッチ等のバインダ一とホウ素又はホウ素化合物 （熱処理後のホウ素換 算で 1〜2 0重量％) とケィ素又はケィ素化合物 （熱処理後のケィ素換 算で 0 . 0 1〜2 0重量％) を添加した後、 混練する。 得られた混練物 を必要に応じて粒度調整した後、 冷間静水圧成形法 （C I P法） 等によ り適当なブロックに成形し、 このブロックを還元性雰囲気又は不活性ガ ス雰囲気の下で 2 4 0 0 °C以上の温度で熱処理する。 さらに所定の粉砕 、 分級等の処理により粒度調整して、 所望のリチウム二次電池負極用炭 素材料を得ることが望ましい。 このように予めブロック化した後、 熱処 理して粒度調整することにより、 特性面でのバラツキが小さレ、炭素材料 を安定してかつ効率良く得られる。  (2) Further, another example of the production method of the present invention is as follows. First, various cokes, artificial graphite, etc., whose particle size has been adjusted as required, are used as aggregates, and a binder such as pitch and boron or a boron compound (1 to 20% by weight in terms of boron after heat treatment) and cake are added. After adding silicon or a silicon compound (0.01 to 20% by weight in silicon conversion after heat treatment), kneading is performed. After adjusting the particle size of the obtained kneaded material as necessary, it is formed into an appropriate block by cold isostatic pressing (CIP method) or the like, and this block is placed in a reducing atmosphere or an inert gas atmosphere. Heat treatment at a temperature of 240 ° C. or more. Further, it is desirable to obtain a desired carbon material for a negative electrode of a lithium secondary battery by adjusting the particle size by a predetermined treatment such as pulverization and classification. By thus pre-blocking and then heat-treating to adjust the particle size, the dispersion in characteristics is small, and a carbon material can be obtained stably and efficiently.
上記の製法において、 骨材としてはピッチコークス、 石油コ一タス、 生ピッチコ一クス、 生石油コークス等の種々のコークスをはじめ、 力一 ボンブラック、 人造黒鉛、 天然黒鉛等を挙げることができ、 特に制限は ない。 またバインダーとしては、 ピッチ、 合成樹脂等が挙げられ、 特に 制限はないが、 熱処理時の重量減少があまり著しくないものが望ましい 。 また、 ホウ素又はホウ素化合物及びケィ素又はケィ素化合物の添加は 、 混練工程の段階に限られず、 成形前であれば後から混練物に添加する ようにしてもよレ、。 In the above-mentioned manufacturing method, examples of the aggregate include various cokes such as pitch coke, petroleum cocoa, raw pitch coke, and raw petroleum coke, as well as carbon black, artificial graphite, and natural graphite. There are no particular restrictions. Examples of the binder include pitch, synthetic resin, and the like. There is no particular limitation, but a binder that does not significantly reduce the weight during heat treatment is preferable. Also, the addition of boron or boron compounds and silicon or silicon compounds However, the present invention is not limited to the stage of the kneading process, and may be added to the kneaded material after molding before molding.
さらに、 熱処理時の雰囲気としての還元性雰囲気また不活性ガス雰囲 気の形成に際しては、 二次電池負極用炭素材料にマイナスの影響を及ぼ さない限り、 その形成手段に制限はない。 例えば、 その雰囲気をバイン ダ一ピッチから発生するガス、 あるいはアルゴンガス、 ヘリウムガス等 で形成することが可能である。  Further, in forming a reducing atmosphere or an inert gas atmosphere as an atmosphere during the heat treatment, there is no limitation on a forming method as long as the carbon material for the negative electrode of the secondary battery is not negatively affected. For example, the atmosphere can be formed by a gas generated from a binder pitch, or an argon gas, a helium gas, or the like.
( 3 ) また、 炭素材料にホウ素及びケィ素を混在させる方法としては、 C V R法又は C V D法を利用することができる。 この場合、 炭素材料は 成形体であっても粉体であってもかまわない。 C V R処理や C V D処理 によりとり込まれたホウ素及びケィ素を有する炭素材料では、 特に表面 層にこれらのホウ素、 ケィ素が多く分布する。 これを負極用炭素材料と した場合、 初期サイクルにおける不可逆容量を低減できる効果が得られ る。 また、 ホウ素及びケィ素がとり込まれる炭素材料としては、 電池特 性の面から黒鉛質のものであることが望ましい。 特に高結晶化した黒鉛 化炭素材や黒鉛 （天然黒鉛， 人造黒鉛等） を使用した場合は、 その高結 晶化構造に由来する電位平坦性， 高容量という特性が加味され、 性能の 優れた電池が製造できるという付加的効果が得られる。  (3) As a method of mixing boron and silicon into a carbon material, a CVR method or a CVD method can be used. In this case, the carbon material may be a compact or a powder. In a carbon material having boron and silicon taken in by CVR treatment or CVD treatment, these boron and silicon are distributed particularly in the surface layer. When this is used as the carbon material for the negative electrode, the effect of reducing the irreversible capacity in the initial cycle can be obtained. The carbon material into which boron and silicon are incorporated is preferably a graphite material from the viewpoint of battery characteristics. In particular, when a highly crystallized graphitized carbon material or graphite (natural graphite, artificial graphite, etc.) is used, the characteristics of potential flatness and high capacity derived from the highly crystallized structure are taken into account, resulting in excellent performance. The additional effect that a battery can be manufactured is obtained.
上記の C V R法又は C V D法を利用してホウ素を混在させる場合は、 ホウ素源として C、 B 2 〇3 、 B C 1 等を使用して行うことがで きる。 When mixing boron using a CVR method or the CVD method described above, C as a source of boron, B 2 〇 3, it is as possible out performed using BC 1 and the like.
この際、 B 2 〇3 、 B C 1 等のホウ素酸化物又はホウ素ハロゲン化 物を使用した場合、 炭素材料が酸素又はハロゲンによる適度の侵食を受 けて微細な気孔が形成され、 リチウムのドープ ·脱ドープ効果をより高 め得る構造とすることができる。 In this case, when using B 2 〇 3, BC boron oxides such as 1 or boron halide compound, the fine pores and accept moderate erosion carbon material by oxygen or halogen is formed, doped lithium A structure that can further enhance the undoping effect can be obtained.
また、 C V R法又は C V D法を利用してケィ素を混在させる場合は、 ケィ素元素源として S i 〇、 S i 02 、 S i Cし 、 S i H 等を使用 して行うことができる。 Also, when using CVR or CVD to mix silicon, S i 〇 as Kei originally Motogen, S i 0 2, and S i C, can be performed using the S i H and the like.
この際、 S i 〇、 S i C 1 4 等のケィ素酸化物又はケィ素ハロゲン化 物を使用した場合、 炭素材料が酸素又はハロゲンによる適度の侵食を受 けて微細な気孔が形成され、 リチウムのド一プ .脱ドープ効果をより高 め得る構造とすることができる。 At this time, S i 〇, when using the S i C 1 Kei-containing oxides such as 4 or Keimoto halogenated compounds, fine pores and accept moderate erosion carbon material by oxygen or halogen is formed, A structure that can further enhance the doping effect of lithium can be obtained.
( 4 ) 次に、 本発明の負極用炭素材料は、 集電体である銅箔との密着性 も良好で、 電池の生産性及び電池性能の一層の向上も可能にしうるもの である。  (4) Next, the carbon material for a negative electrode of the present invention has good adhesion to a copper foil as a current collector, and can further improve battery productivity and battery performance.
前述したように本発明の負極用炭素材料は、 基本的に適量のホウ素を 含有した炭素材料の改良材ではあるが、 同時にホゥ素を含有することに よる特有のマイナス要因も包含した改良材とも言える。 即ち、 黒鉛化触 媒でもあるホウ素の添加によりどうしても結晶化が進み過ぎる傾向にあ り、 濡れ性の低下が避けにくい改良材でもある。  As described above, the carbon material for a negative electrode of the present invention is basically an improved material of a carbon material containing an appropriate amount of boron, but at the same time, is also an improved material that also includes a specific negative factor caused by containing boron. I can say. In other words, the addition of boron, which is also a graphitizing catalyst, tends to promote crystallization by all means, making it difficult to avoid a decrease in wettability.
また、 原料炭素材が最終的に黒鉛化処理された黒鉛化炭素材は、 粉砕 •分級により最終的に粒度調整されて製品化される。 しかしながら、 銅 箔との濡れ性を悪く している二つの原因がある。 一つは、 粒度調整が濡 れ性を考慮した基準で選別されていないために、 粒度調整後の所定範囲 内の粒子群 （製品） には、 現実に濡れ性の良くないものも多く含まれて いる。 もう一つは、 粒度調整後の粒子の形状はミクロ的に観察すると、 平滑でなくて粗い状態にあり、 しかもその表面には、 分級ではとり除け なレ、微細粒子が付着している。  In addition, the graphitized carbon material whose raw carbon material has been finally graphitized is finally adjusted to the particle size by pulverization and classification, and then commercialized. However, there are two causes of poor wettability with copper foil. First, since the particle size adjustment is not selected based on the criteria that take wettability into account, many particles (products) within the specified range after the particle size adjustment include many that do not actually have good wettability. ing. Second, the microscopic observation of the particle shape after particle size adjustment shows that the particles are not smooth but rough, and that the surface has fine particles that cannot be removed by classification.
上記のように濡れ性の低下が目立つようになると、 その分シ一ト化が 困難となり、 銅箔との密着性が不良となりリチウム二次電池としての性 能の低下のみならず、 電池の生産性の低下にもつながるという新たな問 題が浮上する。 そこで、 この問題を改善するためのいくつかの有効な処 理にっき、 以下説明する。 If the decrease in wettability becomes conspicuous as described above, it becomes difficult to reduce the wettability, the adhesion to the copper foil becomes poor, and not only the performance as a lithium secondary battery is reduced, but also the production of the battery. A new problem emerges that leads to a decline in gender. Therefore, there are some useful actions to remedy this problem. This will be explained below.
①まず、 第 1の処理として結晶化度の高い黒鉛化炭素粉体には、 その 表面にアモルファス層を形成する処理が有効である。 例えば、 予めホウ 素及びケィ素を含有した炭素材 （ブロック材も含めて） を黒鉛化する製 造工程を採用する場合は、 黒鉛化した炭素材にピッチ又は樹脂を含浸又 はコートした後、 700〜 1500°C程度で焼成し、 この後粉碎し、 粒 度調整すればよい。 また、 予め熱処理により黒鉛化した炭素材又は天然 黒鉛や人造黒鉛等の黒鉛材に C V D法又は C V R法によりホウ素及びケ ィ素を混在させる製造工程を採用する場合は、 炭素材 （ブロック状又は 粉末） に CVD法又は CVR法によりホウ素及びケィ素を混入し、 その 後前記炭素材にピッチ又は樹脂を含浸又はコ一トして焼成 （700〜1 500°C程度） をした後、 粒度調整すればよい。  ① First, as a first treatment, it is effective to form an amorphous layer on the surface of graphitized carbon powder with high crystallinity. For example, if a manufacturing process for graphitizing a carbon material (including block material) containing boron and silicon in advance is used, impregnate or coat the graphitized carbon material with pitch or resin. Baking at about 700 to 1500 ° C, then pulverizing and adjusting the particle size. If a manufacturing process is used in which boron and silicon are mixed by a CVD method or a CVR method with a carbon material previously graphitized by heat treatment or a graphite material such as natural graphite or artificial graphite, the carbon material (block-shaped or powdered) ) Is mixed with boron and silicon by CVD or CVR, and then the carbon material is impregnated or coated with pitch or resin and fired (about 700-1500 ° C), and then the particle size is adjusted. I just need.
②第 2の処理として、 粒度調整後の黒鉛化炭素粉体のうち、 濡れ性の 比較的良いものを選別する処理が挙げられる。 具体的には、 ホウ素元素 及びケィ素元素を含有する黒鉛化炭素粉体として嵩密度が 0. 5 (g/ c m3 ) 以上で吸油量が 100 (m 1 Z 100 g) 以下のものを選定す る手段が有効である。 このように選定すれば、 ホウ素含有黒鉛でありな がらバインダーとの濡れ性に優れ、 従ってスラリーとした後の銅箔との 密着性に優れたものとすることができる。 また、 シート化時の充填密度 が高くなるため、 同一容器内に充填できる活物質の重量を増すことがで き、 従って容量の大きな電池の作製が可能となる。 (2) As the second treatment, there is a treatment for selecting, from the graphitized carbon powder after the particle size adjustment, those having relatively good wettability. Specifically, a graphitized carbon powder containing a boron element and a silicon element having a bulk density of 0.5 (g / cm 3 ) or more and an oil absorption of 100 (m 1 Z 100 g) or less is selected. Measures are effective. With such a selection, the boron-containing graphite can be excellent in the wettability with the binder, and therefore, can be excellent in the adhesiveness with the copper foil after the slurry. In addition, since the packing density at the time of sheeting is increased, the weight of the active material that can be filled in the same container can be increased, and thus a battery with a large capacity can be manufactured.
また、 黒鉛化炭素粉体として、 上記粉体特性に加えて 10%Dが 5〜 20 rn, 50%Dが 10〜35 μπι、 および 90%Dが 30〜65 mの粒度分布を有する特性のものを選定すれば、 黒鉛化粉体としての比 表面積をより小さくおさえることができ、 安全性にも優れたものとする ことができると共に、 シート化時の充填密度をより高いものとすること W In addition to the above powder properties, the graphitized carbon powder has a particle size distribution of 5-20 rn for 10% D, 10-35 μπι for 50% D, and 30-65 m for 90% D. By selecting a material, the specific surface area of the graphitized powder can be reduced and the safety can be improved, and the packing density at the time of sheeting can be increased. W
ができるので、 一層の容量の向上が期待できる電池の作製が可能となる , Making it possible to manufacture batteries that can be expected to have even higher capacity.
③第 3の処理として、 粒度調整後の黒鉛化炭素粉体から微細粒子を除 去し、 その粉体表面を平滑化する処理が挙げられる。 具体的には、 ホウ 素元素及びケィ素元素を含有する黒鉛化炭素粉体にリン酸を添加した後 、 熱処理する手段が有効である。 ここで 「リン酸」 は、 H 3 P〇4 ， H . P 2 07 , (H P 03) r, ， Η4 Ρ 2 06 ， Η3 Ρ〇3 ， Η 3 Ρ 02 等 のリンの酸素酸の水溶液がその代表的なものであるが、 基本的に Ρと Η と〇を含む化合物であればよく、 特に制限はない。 なお、 熱処理温度は 、 リン酸が蒸発する温度であればよく、 一般には 7 0 0 °C以上が望まし レ、。 (3) As a third treatment, there is a treatment for removing fine particles from the graphitized carbon powder after particle size adjustment and smoothing the powder surface. Specifically, it is effective to add a phosphoric acid to a graphitized carbon powder containing a boron element and a silicon element and then heat-treat the powder. Where "phosphoric acid", H 3 P_〇 4, H. P 2 0 7 , (HP 0 3) r,, Η 4 Ρ 2 0 6, Η 3 Ro_〇 3, Η 3 Ρ 0 2 like phosphorus A typical example is an aqueous solution of an oxygen acid of formula (I), but there is no particular limitation as long as it is basically a compound containing Ρ, Η and 〇. The heat treatment temperature may be any temperature at which the phosphoric acid evaporates, and is generally preferably 700 ° C. or higher.
上記①〜③の処理は重ねることができる。 例えば、 ①処理を施した炭 素粉末に、 ②処理の粒度調整を施し、 更に③処理のリン酸添加を施すこ とができる。 また、 ②処理の粒度調整を施し、 加えて③処理のリン酸添 加を施すことができる。 なお、 炭素粉末にした後、 ¥ 0法又はじ 1 法によりホウ素元素及びケィ素元素を含ませる場合には、 ②と③処理の 少なくとも一つを施すことが好ましい。 なお、 上記①〜③の処理は、 ホ ゥ素元素及びケィ素元素を含有させた炭素粉末だけに限らず、 ホウ素元 素だけを含有させた炭素粉末にも適用可能である。  The above processes ① to ③ can be repeated. For example, (1) the carbon powder that has been treated can be subjected to (2) particle size adjustment in the treatment, and (3) phosphoric acid can be added in the treatment. In addition, (2) the particle size of the treatment can be adjusted, and additionally, (3) phosphoric acid can be added. In addition, when the boron element and the silicon element are contained by the 0 method or the 1 method after the carbon powder is formed, it is preferable that at least one of the treatments 2 and 3 is performed. Note that the above treatments (1) to (3) can be applied not only to carbon powder containing boron and silicon elements but also to carbon powder containing only boron.
つぎに、 前述した電池負極用炭素材料を負極活物質として用いてなる リチウムイオン二次電池の構造を説明する。 リチウム二次電池の構成は 、 正極、 負極及びセパレータと非水電解液との組み合わせ、 あるいは正 極、 負極及びセパレータとしての有機また無機固体電解質と非水電解液 との組み合わせがあるが、 これに限定されるものでもない。  Next, a structure of a lithium ion secondary battery using the above-described carbon material for a battery negative electrode as a negative electrode active material will be described. Lithium secondary batteries have a combination of a positive electrode, a negative electrode and a separator with a non-aqueous electrolyte, or a combination of an organic or inorganic solid electrolyte as a positive electrode, a negative electrode and a separator with a non-aqueous electrolyte. It is not limited.
正極の活物質としてリチウムコノくルト複合酸化物を用いるのが普通で あるが、 リチウムコバルト系複合酸化物、 リチウムニッケル又はリチウ ムニッケル系複合酸化物、 二硫化チタンをはじめとしてスピネル型リチ ゥムマンガン酸化物などのマンガン系活物質、 あるいは五酸化バナジゥ ム及び三酸化モリブデンなどリチウムを吸蔵放出するようなホスト物質 であれば種々のものを用いることができる。 It is common to use a lithium-conoult composite oxide as the active material of the positive electrode, but lithium-cobalt-based composite oxide, lithium nickel or lithium Manganese-based active materials such as spinel-type lithium manganese oxides, such as manganese-based composite oxides and titanium disulfide, or various host materials such as vanadium pentoxide and molybdenum trioxide that can absorb and release lithium. Can be used.
さらに、 有機溶媒も基本的に限定されるものではない。 従来、 リチウ ムニ次電池に用いられているものであれば本発明と同様の効果を得るこ とができる。 例えば、 溶媒としては、 プロピレンカーボネート、 ェチレ ンカーボネート、 γ—プチロラク トン、 スルホランなどの高誘電率溶媒 に 1 ， 2—ジメ トキシェタン、 ジメチルカーボネート、 ェチルメチルカ —ボネート、 ジェチルカーボネート、 メチルフオルメートなどの低粘度 溶媒を混合したものを用いることができる。 あるいは、 リチウムイオン 伝導性の固体電解質、 例えば P A Nなどの有機系固体電解質もしくはリ チウムタイタネートなどの無機系固体電解質を単独でもしくは有機溶媒 と組み合わせて用レ、てもよい。  Further, the organic solvent is not fundamentally limited. Conventionally, the same effects as those of the present invention can be obtained as long as they are used in lithium secondary batteries. For example, solvents such as propylene carbonate, ethylene carbonate, γ-butyrolactone, and sulfolane can be used in solvents having a high dielectric constant such as 1,2-dimethoxetane, dimethyl carbonate, ethylmethylcarbonate, getylcarbonate, and methylformate. A mixture of low-viscosity solvents can be used. Alternatively, a lithium ion conductive solid electrolyte, for example, an organic solid electrolyte such as PAN or an inorganic solid electrolyte such as lithium titanate may be used alone or in combination with an organic solvent.
加えて、 電池は、 角形、 円筒形、 コイン形又はペーパー形など形状は どんなものであってもよい。 発明を実施するための最良の形態  In addition, the batteries may be of any shape, such as prismatic, cylindrical, coin-shaped or paper-shaped. BEST MODE FOR CARRYING OUT THE INVENTION
以下に実施例及び比較例を掲げて本発明を更に詳しく説明するが、 本 発明はこれら実施例のみに制限されるものではない。  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.
まず、 リチウムイオン二次電池負極用炭素材料の放電容量及び初期効 率に関して、 実施例と比較例を対比して説明する。  First, the discharge capacity and the initial efficiency of the carbon material for a negative electrode of a lithium ion secondary battery will be described in comparison with Examples and Comparative Examples.
(実施例 1及び比較例 1 )  (Example 1 and Comparative Example 1)
平均粒径 3 0 mに粒度調整したピッチコークスに、 ホウ素元素源と して B C又は B 2 0 3 を、 ケィ素元素源として S i C又は S i〇2 を 、 それぞれの割合を変えて添加、 混合した。 これらの混合物を黒鉛ルツ ボに詰め、 アチェソン炉にて 2 6 0 0 °Cで熱処理を行った。 その後、 そ れぞれの熱処理物について平均粒径が 2 0 mとなるように粒度調整を 行レ、、 第 1図に示すように実施例 1にっき (a)〜(d)、 比較例 1にっき (a)〜 (f)の炭素材料を得た。 Added to the average particle diameter of 3 0 m pitch coke particle size control in the BC or B 2 0 3 as a boron element source, the S i C or S I_〇 2 as Kei originally Motogen, by changing the respective proportions , Mixed. These mixtures can be mixed with graphite It was heat-treated at 260 ° C. in an Acheson furnace. Thereafter, the particle size of each heat-treated product was adjusted so that the average particle size became 20 m. As shown in FIG. 1, Examples 1 to 3 (a) to (d), Comparative Example 1 Carbon materials (a) to (f) were obtained.
(実施例 2及び比較例 2 )  (Example 2 and Comparative Example 2)
平均粒径 1 0 mに粒度調整したピッチコークス 1 0 0重量部に、 バ インダ一ピッチ 5 0重量部を加え、 2 0 0 °Cにて混練を行った。 得られ た混練物を平均粒径 1 0 0 mに粒度調整し、 これに、 ホウ素元素源と して B 4 C又は B 2 〇3 を、 ケィ素元素源として S i C又は S i〇2 を 、 それぞれの割合を変えて添加、 混合した。 これらの混合物を C I P成 形し、 1 0 0 0 °Cで焼成した後、 アチェソン炉にて 2 6 0 0。Cの熱処理 を行った。 熱処理後、 各ブロック状成形物を粉砕、 分級して平均粒径がTo 100 parts by weight of pitch coke whose particle size was adjusted to an average particle diameter of 100 m, 50 parts by weight of a binder pitch was added, and kneading was performed at 200 ° C. The resulting kneaded product was adjusted particle size to an average particle size 1 0 0 m, which in the B 4 C or B 2 〇 3 as a boron element source, S i C or S I_〇 2 as Kei originally Motogen Was added in different proportions and mixed. These mixtures were subjected to CIP molding, fired at 100 ° C., and then fired in an Acheson furnace. C was heat treated. After heat treatment, each block-shaped molded product is pulverized and classified to obtain an average particle size.
2 0 mとなるよう粒度調整を行い、 第 1図に示すように実施例 2につ き (a)〜(h)、 比較例 2にっき (a)〜(e)の炭素材料を得た。 The particle size was adjusted to 20 m to obtain carbon materials (a) to (h) in Example 2 and carbon materials (a) to (e) in Comparative Example 2 as shown in FIG.
(実施例 3 )  (Example 3)
平均粒径 2 0 mに粒度調整した人造黒鉛を黒鉛ルツボに入れ、 ホウ 素元素源として B 2 03 を使用し 1 8 0 0 °Cのアルゴン雰囲気の下、 常 圧にて C V R処理を行った。 得られた物を、 ケィ素元素源として S i O を使用し 2 0 0 0 °Cにて常圧 C V R処理を行い、 第 1図に示す実施例Put artificial graphite adjusted particle size to an average particle size 2 0 m to a graphite crucible, carried under an argon atmosphere using the B 2 0 3 as boric originally Motogen 1 8 0 0 ° C, the CVR process under atmospheric pressure Was. The obtained product was subjected to a normal pressure CVR treatment at 200 ° C. using SiO as a silicon element source, and the embodiment shown in FIG. 1 was used.
3 (a)と実施例 3 (b)の炭素材料を得た。 3 (a) and the carbon material of Example 3 (b) were obtained.
第 1図から判るように、 ホウ素元素及びケィ素元素を含有する炭素材 料は、 ホウ素元素及びケィ素元素を両方含まない一般的な黒鉛質炭素材 料やホウ素のみを含む炭素材料に比べ、 初期効率， 放電容量の点でいず れも優れていることが分かる。 また、 ホウ素元素及びケィ素元素の各含 有量が本発明の要件 （特定範囲） を満たす実施例 1〜3の場合は、 その 初期効率及び放電容量についての改善効果がさらに高くなつていること が分かる。 As can be seen from Fig. 1, the carbon material containing boron and silicon elements is less than the general graphitic carbon material that does not contain both boron and silicon elements and the carbon material that contains only boron. It can be seen that both initial efficiency and discharge capacity are excellent. In addition, in Examples 1 to 3 in which the content of each of the boron element and the silicon element satisfies the requirements (specific range) of the present invention, the effect of improving the initial efficiency and the discharge capacity is further increased. I understand.
つぎに、 リチウムイオン二次電池負極用炭素材料の濡れ性に関して、 実施例と比較例を対比して説明する。  Next, the wettability of the carbon material for a negative electrode of a lithium ion secondary battery will be described in comparison with Examples and Comparative Examples.
(実施例 4)  (Example 4)
平均粒径 3 0 μ mに粒度調整したピッチコークスに、 ホウ素元素源と して B4 Cを、 ケィ素元素源として S i〇2 を、 その割合が実施例 1 ( d) と同じになるように添加、 混合した。 これらの混合物を黒鉛ルツボ に詰め、 アチェソン炉にて 2 6 0 0°Cの熱処理 （黒鉛化） を行った。 得 られた黒鉛化炭素粉体に 2 5 0°Cでピッチをコ一トした後、 1 2 0 0°C で焼成し、 この後、 平均粒径が 2 0 mとなるように粒度調整を行い、 後述の銅箔との密着性試験に洪した。 Pitch coke particle size adjustment to an average particle diameter of 3 0 mu m, consisting of B 4 C as a boron element source, the S I_〇 2 as Kei originally Motogen, the same the rate is as in Example 1 (d) And mixed as above. These mixtures were packed in a graphite crucible and heat-treated (graphitized) at 260 ° C in an Acheson furnace. After coating the obtained graphitized carbon powder with a pitch at 250 ° C, it is baked at 1200 ° C, and then the particle size is adjusted so that the average particle size becomes 20 m. This led to a later-mentioned adhesion test with copper foil.
(実施例 5)  (Example 5)
平均粒径 1 0 mに粒度調整したピッチコ一クス 1 0 0重量部に、 ノく インダ一ピッチ 5 0重量部を加え、 2 0 0°Cにて混練を行った。 得られ た混練物を平均粒径 1 0 0 に粒度調整し、 これに、 ホウ素元素源と して B 2 03 を、 ケィ素元素源として S i〇2 を、 その割合が実施例 2To 100 parts by weight of pitch coke having an average particle size adjusted to 100 m, 50 parts by weight of iron pitch was added and kneaded at 200 ° C. The resulting kneaded product was adjusted particle size to an average particle diameter of 1 0 0, which in the B 2 0 3 as a boron element source, the S I_〇 2 as Kei originally Motogen, the ratio is Example 2
(g) と同じになるように添加、 混合した。 これらの混合物を C I P成 形し、 1 0 0 0°Cで焼成した後、 アチェソン炉にて 2 6 0 0°Cの熱処理It was added and mixed in the same manner as in (g). These mixtures were formed into CIP, fired at 1000 ° C, and then heat-treated at 260 ° C in an Acheson furnace.
(黒鉛化） を行った。 得られた黒鉛化炭素ブロックにピッチを含浸した 後、 1 2 0 0 °Cで焼成し、 この後粉砕 ·分級して平均粒径が 2 0 mと なるように粒度調整を行い、 後述の銅箔との密着性試験に洪した。 (Graphitization). After impregnating the obtained graphitized carbon block with pitch, baking it at 1200 ° C., then pulverizing and classifying to adjust the particle size to an average particle size of 20 m, Flooded adhesion test with foil.
(実施例 6 )  (Example 6)
ブロック状の人造黒鉛 （嵩密度 1. 8 g/c m3 ， 平均ポア一半径 1 . 5 u m) に対して、 予めピッチを含浸し、 1 2 0 0°Cで焼成する処理 を施した。 得られたプロックを平均粒径 2 0 u mに粉砕、 粒度調整した 。 得られた人造黒鉛粉末を、 ホウ素元素源として B2 〇3 を使用し 1 8 00°Cのアルゴン雰囲気の下、 常圧にて CVR処理を行った。 得られた 物を、 ケィ素元素源として S i 02 を使用し 2000°Cにて常圧 CVR 処理を行い、 得られた黒鉛化炭素粉体を後述の銅箔との密着性試験に洪 した。 Block artificial graphite (bulk density 1.8 g / cm 3 , average pore radius 1.5 μm) was impregnated with pitch in advance and fired at 1200 ° C. The obtained block was pulverized to an average particle size of 20 μm and the particle size was adjusted. The artificial graphite powder obtained, using B 2 〇 3 as the element boron source 1 8 CVR treatment was performed at normal pressure under an argon atmosphere of 00 ° C. The resulting material, Kei originally performed normal pressure CVR process using S i 0 2 at 2000 ° C as Motogen, Hong resulting graphitized carbon powder adhesion test between the copper foil described later did.
(比較例 3〜 5 )  (Comparative Examples 3 to 5)
実施例 4〜 6でそれぞれ、 黒鉛化後のピッチ含浸又はコート '焼成処 理工程を経由せずに得られた粒度調整済の黒鉛化粉体を、 後述の銅箔と の密着性試験に供した。  In each of Examples 4 to 6, the graphitized powder having been subjected to pitch impregnation after graphitization or having been subjected to particle size adjustment obtained without passing through the coating and baking treatment steps was subjected to an adhesion test with a copper foil described later. did.
(実施例 7)  (Example 7)
実施例 2 (g) と同様の製法で得られた粉体を粒度調整し、 粉体嵩密 度 0. 75 (g/cm3 ) 、 吸油量が 67 (m 1 / 100 g ) であって 、 10%0が7 111、 50%0が20 111、 90%0が58 111からな る粒度分布を有する黒鉛化炭素粉体を得て、 後述の銅箔との密着性試験 に供した。 なお、 吸油量は、 J I SK6221 「ゴム用カーボンブラッ クの試験方法」 6. 1. 1項で規定されている A法 （機械法） により測 定された値を指す。 The powder obtained by the same production method as in Example 2 (g) was subjected to particle size adjustment, the powder bulk density was 0.75 (g / cm 3 ), and the oil absorption was 67 (m 1/100 g). A graphitized carbon powder having a particle size distribution of 7111 for 10% 0, 20111 for 50% 0, and 58111 for 90% 0 was obtained and subjected to an adhesion test with a copper foil described later. The oil absorption refers to the value measured by the method A (mechanical method) specified in JI SK6221 “Test method for carbon black for rubber” Section 6.1.1.
(実施例 8 )  (Example 8)
平均粒径 30 w mに粒度調整したピッチコ一クスに、 ホウ素元素源と して Cを、 ケィ素元素源として S i 02 を、 その割合が実施例 1 ( c) と同じになるように添加、 混合した。 これらの混合物を黒鉛ルツボ に詰め、 アチェソン炉にて 2600°Cの熱処理 （黒鉛化） を行った後、 平均粒度が 20 / mとなるように粒度調整を行った。 得られた黒鉛化粉 体 100重量部にリン酸 （H3 P〇 ) を 30重量部添加し十分混合し た。 こうして表面をリン酸で湿らした黒鉛化粉体を黒鉛ルツボに詰め、 1200°Cで熱処理を行った。 得られた粉体を後述の銅箔との密着性試 験に供した。 (比較例 6 ) The Pitchiko one box adjusted particle size to an average particle size 30 w m, the C and the elemental boron source, the S i 0 2 as Kei originally Motogen, so the ratio is the same as in Example 1 (c) Added and mixed. These mixtures were packed in graphite crucibles, heat-treated (graphitized) at 2600 ° C in an Acheson furnace, and then adjusted to an average particle size of 20 / m. The resulting graphitized powder 100 parts by weight of phosphoric acid (H 3 P_〇) was added thoroughly mixed 30 parts by weight. The graphitized powder whose surface was moistened with phosphoric acid was packed in a graphite crucible and heat-treated at 1200 ° C. The obtained powder was subjected to an adhesion test with a copper foil described later. (Comparative Example 6)
実施例 1 ( c ) で得られたリン酸添加前の黒鉛化炭素粉体を、 後述の 銅箔との密着性試験に供した。  The graphitized carbon powder obtained before the addition of phosphoric acid obtained in Example 1 (c) was subjected to an adhesion test with a copper foil described later.
〔銅箔との密着性試験〕  (Adhesion test with copper foil)
厚み 2 0 mの銅箔上に、 上記 （実施例 5〜 8 ) 及び （比較例 4〜 7 ) で用意した各黒鉛化炭素粉体 9 0重量部とバインダ一としてのポリフ ッ化ビ二リデン 1 0重量部とを混合し、 N—メチル一2—ピロリ ドン （ NM P ) を適宜加えてペース ト状に調整したものを塗布、 乾燥すること により負極板を作製した。 得られた負極板を机の端に当てて 1 5回擦る しごき試験を行い、 その後、 黒鉛化炭素粉体と銅箔との密着度合いを目 視にて観察した結果を、 まとめて第 2図に示す。  On a 20-m-thick copper foil, 90 parts by weight of each of the graphitized carbon powder prepared in the above (Examples 5 to 8) and (Comparative Examples 4 to 7) and polyvinylidene fluoride as a binder were used. The mixture was mixed with 10 parts by weight, N-methyl-1-pyrrolidone (NMP) was appropriately added, the mixture was adjusted to a paste, and the mixture was dried to prepare a negative electrode plate. The obtained negative electrode plate was rubbed 15 times with the edge of a desk, and the ironing test was performed.After that, the degree of adhesion between the graphitized carbon powder and the copper foil was visually observed. Shown in
第 2図からも明らかなように、 黒鉛化後にピッチ含浸 ·焼成処理を施 してから粒度調整した実施例 4〜 6の黒鉛化炭素粉体では、 剥離が認め られなかった。 これに対し、 黒鉛化後ピッチ含浸 ·焼成処理を施してい ない比較例 3〜 5の黒鉛化炭素粉体では、 かなり剥離した。  As is clear from FIG. 2, no exfoliation was observed in the graphitized carbon powders of Examples 4 to 6, which were subjected to pitch impregnation and firing after graphitization and then to particle size adjustment. In contrast, the graphitized carbon powders of Comparative Examples 3 to 5, which were not subjected to pitch impregnation and firing after graphitization, peeled considerably.
また、 粉体嵩密度及び吸油量が本発明の要件を満たし、 粒度分布も適 切である実施例 7は、 実施例 4〜6と同程度の良好な結果が得られるこ とが分かる。  In addition, it can be seen that in Example 7 in which the powder bulk density and the oil absorption amount satisfy the requirements of the present invention and the particle size distribution is also appropriate, the same good results as in Examples 4 to 6 can be obtained.
リン酸添加 ·熱処理を施した実施例 8は、 ほとんど剥離が認められな かった。 これに対し、 リン酸添加 ·熱処理を施さない比較例 6はかなり 剥離した。  In Example 8, which was subjected to phosphoric acid addition and heat treatment, almost no peeling was observed. In contrast, Comparative Example 6, which was not subjected to phosphoric acid addition and heat treatment, peeled considerably.
実施例 1〜 3及び比較例 1、 2についても、 上述の実施例 5〜 8及び 比較例 4〜 7と同じ要領で負極板を作製した後、 各実施例及び比較例に 対応する負極板を単板試験に供した。 この時、 対極、 参照極としてリチ ゥム金属を用い、 0 . 5 mA hで 0 Vまで充電し、 3 Vまで放電を行つ た。 電解液は L i P F 6 を 1 m o 1 / 1を含むエチレンカーボネィ ト ： ジメチルカ一ボネイ ト = 1 ： 1 (体積比） の混合液を使用した。 各放電 容量、 初期効率の結果を、 各炭素材料のホウ素濃度、 ケィ素濃度と共に 第 1図に示す。 なお、 第 3図には代表例として、 実施例 2 (f ) 、 比較 例 2 (a) のリチウム二次電池負極用材としての充放電曲線を示す。 第 1図から、 ホウ素及びケィ素を含有する炭素材料は、 ホウ素及びケ ィ素を両方含まない一般的な黒鉛炭素材料やホウ素のみを含む炭素材料 に比べ、 初期効率、 放電容量の点でいずれも優れていることがわかる。 また、 ホウ素及びケィ素の各含有量が本発明の特定範囲である実施例 1 〜 3の場合は、 その初期効率及び放電容量についての改善効果がさらに 高くなつていることが分かる。 For Examples 1 to 3 and Comparative Examples 1 and 2, after preparing the negative electrode plates in the same manner as in Examples 5 to 8 and Comparative Examples 4 to 7, the negative electrode plates corresponding to the respective Examples and Comparative Examples were prepared. It was subjected to a veneer test. At this time, lithium metal was used as a counter electrode and a reference electrode, charged to 0 V at 0.5 mAh, and discharged to 3 V. Ethylene carbonate Nei DOO electrolytic solution containing a L i PF 6 1 mo 1/ 1: A mixed solution of dimethyl carbonate = 1: 1 (volume ratio) was used. Fig. 1 shows the results of each discharge capacity and initial efficiency, together with the boron concentration and the silicon concentration of each carbon material. FIG. 3 shows, as representative examples, charge / discharge curves of the negative electrode material of the lithium secondary battery of Example 2 (f) and Comparative Example 2 (a). From Fig. 1, it can be seen that the carbon material containing boron and silicon has lower initial efficiency and discharge capacity than the general graphite carbon material that does not contain both boron and silicon and the carbon material that contains only boron. It can be seen that is also excellent. Further, it can be seen that in the case of Examples 1 to 3 in which the contents of boron and silicon are in the specific ranges of the present invention, the effects of improving the initial efficiency and the discharge capacity are further enhanced.
また、 第 3図から、 実施例 2(f)で得られたホウ素及びケィ素を含有す るリチウム二次電池負極材は、 比較例 2(a) (従来の黒鉛系負極材） に比 ベて、 従来の黒鉛系材料の利点である、 0. 25V [V V s L i /L i 一 〕 付近までの電位平坦性を有しつつ、 かつ 1. 3V [V V s L i /L i一 〕 以上において 0. 25 Vまでの放電容量の 1 %以上の放電容量を 有することにより、 過放電にも強いリチウム二次電池負極材となってい ることがよく分かる。  Also, from FIG. 3, the lithium secondary battery negative electrode material containing boron and silicon obtained in Example 2 (f) is compared with Comparative Example 2 (a) (a conventional graphite-based negative electrode material). Therefore, while having the potential flatness of about 0.25V [VVsLi / Li], which is an advantage of the conventional graphite material, and 1.3V [VVsLi / Li] From the above, it can be clearly seen that the discharge capacity of 1% or more of the discharge capacity up to 0.25 V makes the lithium secondary battery negative electrode material resistant to overdischarge.
また、 第 3図から分かるように、 1. 3 V付近でピークが認められる 力 このピークについて電気化学的な特性を調べるべく、 本発明者らは 3 ~~ ^。 の走査範囲で （サイクリックボルタンメ トリー） 測定 を行った。 その結果を第 4図〜第 5図に示す。  In addition, as can be seen from FIG. 3, the force at which a peak is observed at around 1.3 V. In order to examine the electrochemical characteristics of this peak, the present inventors performed 3 to ~ ^. (Cyclic voltammetry) measurement was performed in the scanning range of. The results are shown in FIGS.
第 4図は、 電位の走査速度 v=l. 0 〔mVZs〕 でのサイクリック ボルタモグラム （電流一電位曲線） である。 この図から明らかなように 、 実施例 2(f)はアノード方向で 1. 2V付近、 力ソード方向で 1. 4V 付近でピークが見られ、 比較例 2 (a)についてはこのピークが見られない ことが分かる。 また、 実施例 2(f)において、 走査速度 Vを 0. 5 CmV Zs〕 ， 0. 3 〔mVZs〕 ， 0. 1 〔mVZs〕 ， 0. 05 [mV/ s〕 と変えながら測った場合のサイクリックボルタモグラムは図 5のよ うになり、 これをピーク電流 （ i p ) と走査速度の平方根 （v1/2)との 関係で示せば、 図 6に示すような直線が得られる。 Fig. 4 is a cyclic voltammogram (current-potential curve) at a potential scanning speed v = 1.0 [mVZs]. As is clear from this figure, in Example 2 (f), a peak was observed at around 1.2 V in the anode direction and at around 1.4 V in the force sword direction, and this peak was observed in Comparative Example 2 (a). I understand that there is no. In Example 2 (f), the scanning speed V was 0.5 CmV Zs], 0.3 [mVZs], 0.1 [mVZs], 0. 05 [mV / s] and the cyclic voltammograms when measured while changing the good Uninari of Figure 5, this peak current (i p ) And the square root of the scanning speed (v 1/2 ), a straight line as shown in Fig. 6 is obtained.
第 5図及び第 6図から、 以下のことが明らかとなった。 即ち、 v〉0 . 05 (mV/ s ] で 1. 3 V付近のピークが起こる反応は拡散律速で ある。 また、 v< 0. 05 [mV/ s ] では力ソード方向の電流の絶対 値 I i PC I とアノード方向の電流値 i P2がー致することから、 この 1. 3 V付近でのピーク反応は可逆である。 さらに、 実施例 2(f)について、 1 V以上の範囲でカソ一ド ·アノード両方向の電気量をそれぞれ I Qc I , Qa として比較すると、 走査速度 v = 0. 05 〔mVZs〕 のとき 、 いずれの Qも 9 〔C〕 とほぼ等しかった。 From Fig. 5 and Fig. 6, the following became clear. In other words, the reaction where a peak around 1.3 V occurs at v> 0.05 (mV / s) is diffusion-controlled, and at v <0.05 [mV / s], the absolute value of the current in the force direction Since I i PC I and the current value i P2 in the anode direction are close to each other, the peak reaction at around 1.3 V is reversible. Comparing the quantity of electricity in both the cathode and anode directions as IQ c I and Qa, respectively, when the scanning speed v = 0.05 [mVZs], each Q was almost equal to 9 [C].
つぎに、 本発明の負極用炭素材料を用いたリチウムイオン二次電池の サイクル特性に関する実施例を説明する。  Next, examples relating to the cycle characteristics of a lithium ion secondary battery using the carbon material for a negative electrode of the present invention will be described.
〔実施例電池の作製〕  (Preparation of Example Battery)
第 7図に、 本発明に係るリチウム二次電池の分解斜視図を示す。 1は リチウム二次電池、 2は電極群、 3は正極板、 4は負極板、 5はセパレ ータ、 6は電池ケース、 7はケース蓋、 8は安全弁、 1 0は正極端子、 1 1は正極リードである。  FIG. 7 shows an exploded perspective view of the lithium secondary battery according to the present invention. 1 is a lithium secondary battery, 2 is an electrode group, 3 is a positive electrode plate, 4 is a negative electrode plate, 5 is a separator, 6 is a battery case, 7 is a case lid, 8 is a safety valve, 10 is a positive electrode terminal, 1 1 Is a positive electrode lead.
リチウム二次電池 1の構成は、 正極板 3、 負極板 4、 セパレータ 5及 び非水系の電解液からなる渦巻き状の電極群 2が電池ケース 6に収納さ れた角形リチウム二次電池である。 電池ケース 6は、 厚さ 0. 3mm、 内寸 33. 1 X 46. 5 X 7. 5 mmの鉄製本体の表面に厚さ 5 μ mの ニッケルメツキを施したものであり、 側部上部には電解液注入用の孔 1 00が設けられている。  The configuration of the lithium secondary battery 1 is a prismatic lithium secondary battery in which a spiral electrode group 2 composed of a positive electrode plate 3, a negative electrode plate 4, a separator 5, and a non-aqueous electrolyte is housed in a battery case 6. . The battery case 6 is made of an iron body with a thickness of 0.3 mm and an inner dimension of 33.1 x 46.5 x 7.5 mm with a nickel plating of 5 μm on the surface. Is provided with a hole 100 for injecting an electrolytic solution.
正極板 3は、 その集電体が厚み 20 μ mのアルミ箔であり、 それに活 物質としてリチウムコバルト複合酸化物を保持したものである。 正極板 3は、 結着剤であるポリフッ化ビニリデン 8部と導電剤であるァセチレ ンブラック 5部とを活物質 87部と共に混合してペースト状に調整した 後、 集電体材料の両面に塗布、 乾燥することによって作製した。 In the positive electrode plate 3, the current collector is an aluminum foil having a thickness of 20 μm. It is a substance holding lithium cobalt composite oxide as a substance. The positive electrode plate 3 is prepared by mixing 8 parts of polyvinylidene fluoride as a binder and 5 parts of acetylene black as a conductive agent with 87 parts of an active material to prepare a paste, and then applying the paste to both surfaces of a current collector material It was prepared by drying.
実施例にかかる負極板 4は 8種類作製した。 一つは、 厚み 20 mの 銅箔からなる集電体の両面に、 以下の配合の黒鉛粉末 86重量部と結着 剤としてのポリフッ化ビニリデン 14重量部とを混合し、 NMPを加え てペース ト状に調整したものを塗布、 乾燥することにより作製した。 使 用した黒鉛粉末は第 1図の実施例 1 (b) (d) ， 実施例 2 (a) (d ) ( f ) (h) ， 実施例 3 (a) (b) に記載のものであって、 それに よる電池を実施例 9〜 16とする。  Eight types of negative electrode plates 4 according to the examples were produced. One is to mix 86 parts by weight of graphite powder with the following composition and 14 parts by weight of polyvinylidene fluoride as a binder on both sides of a current collector made of copper foil with a thickness of 20 m, add NMP, and add NMP. The product was prepared by applying and drying the product prepared in the shape of ト. The graphite powder used was that described in Example 1 (b) (d), Example 2 (a) (d) (f) (h), and Example 3 (a) (b) in FIG. Therefore, the batteries according to Examples 9 to 16 are used.
比較例にかかる負極板 4は 4種類作製した。 第 1図の比較例 2 (b) に記載の黒鉛粉末を使用したものを比較例 7とする。 またホウ素又はケ ィ素の有無が異なるだけで同じ製法により、 ホウ素元素だ:ナを含有する 黒鉛粉末を使用したものを比較例 8とし、 ケィ素元素だけを含有する黒 鉛粉末を使用したものを比較例 9とする。  Four types of negative electrode plates 4 according to comparative examples were produced. The one using the graphite powder described in Comparative Example 2 (b) of FIG. 1 is referred to as Comparative Example 7. In addition, the same manufacturing method was used except that the presence or absence of boron or silicon was the same as that used in Example 8.A graphite element containing boron was used as a comparative example 8, and a graphite powder containing only silicon was used. Is referred to as Comparative Example 9.
セパレ一タ 5は、 ポリエチレン微多孔膜、 また電解液は、 L i PF6 を 1 mo 1 / 1含むエチレンカーボネート ： ジメチルカーボネ一ト = 1 ： 1 (体積比） の混合液を使用した。 なお、 正極板 3は、 安全弁 8と正 極端子 10を設けたケース蓋 7の端子 10と正極リード 1 1を介して接 続されている。 負極板 4は電池ケース 6の內壁との接触により接続され ている。 そして、 この電池は、 ケース 6に蓋 7をレーザー溶接して封口 される。 Separators one data 5, microporous polyethylene membrane, also electrolyte, L i PF 6 to 1 mo 1/1 containing ethylene carbonate: dimethyl carbonate ne Ichito = 1: Using a mixture of 1 (volume ratio). The positive electrode plate 3 is connected to the terminal 10 of the case lid 7 provided with the safety valve 8 and the positive electrode terminal 10 via the positive electrode lead 11. The negative electrode plate 4 is connected by contact with the wall of the battery case 6. Then, this battery is sealed by laser welding the lid 7 to the case 6.
このようにして、 最終的に上記構成に係る設計容量 90 OmA hの電 池を作製した。 なお、 電解液量を 25m 1 とした。  In this way, a battery having a design capacity of 90 OmAh according to the above configuration was finally manufactured. The electrolyte volume was 25 m 1.
〔電池の性能試験〕 実施例 9〜 16、 比較例 7〜9の電池について、 0. 5Cの電流で 4 . 1 Vまで定電流定電圧充電を行って満充電状態とした。 そして、 各電 池を 1 Cで 2. 75Vまで放電し、 クーロン効率、 放電容量を測定した 。 さらに、 同様の充放電条件で 500サイクルまで実施し、 500サイ クル目のクーロン効率、 放電容量を測定した。 そして、 初回サイクルの 放電容量と 500サイクル目の放電容量との比率によるサイクル特性を 算出した。 その結果を第 8図に示す。 [Battery performance test] The batteries of Examples 9 to 16 and Comparative Examples 7 to 9 were charged at a constant current and a constant voltage up to 4.1 V with a current of 0.5 C to reach a fully charged state. Then, each battery was discharged to 2.75 V at 1 C, and Coulomb efficiency and discharge capacity were measured. Furthermore, the same charge and discharge conditions were used up to 500 cycles, and the coulomb efficiency and discharge capacity at the 500th cycle were measured. Then, the cycle characteristics were calculated based on the ratio between the discharge capacity in the first cycle and the discharge capacity in the 500th cycle. Figure 8 shows the results.
この結果、 ホウ素元素とケィ素元素の両方を適量含有する実施例 9〜 As a result, Examples 9 to 10 containing appropriate amounts of both boron element and silicon element
1 6の電池は、 初回サイクルの容量が 860〜89 OmAhであるのに 対して、 ホウ素元素とケィ素元素のいずれか一方又は全く含まない比較 例 7〜 9の電池は、 初回サイクルの容量が 840〜85 OmAhである 。 初回サイクルだけの比較では、 実施例 9〜 1 6は、 比較例 7〜9より 僅かに優れるだけである。 The batteries of No. 16 had a first cycle capacity of 860-89 OmAh, while the batteries of Comparative Examples 7-9, which did not contain either boron element or silicon element, had no initial cycle capacity. 840-85 OmAh. In the comparison of the first cycle only, Examples 9 to 16 are only slightly better than Comparative Examples 7 to 9.
しかしながら、 500サイクル目の容量をみると、 実施例 9〜 1 6は However, looking at the capacity at the 500th cycle, Examples 9 to 16 show that
820〜88 OmAhで低下が少ないのに対して、 比較例 7〜 9は 75820 to 88 OmAh, the decrease is small, whereas Comparative Examples 7 to 9 are 75
0〜 76 OmAhとかなり低下している。 It has dropped considerably from 0 to 76 OmAh.
なお、 実施例 9〜 1 6について、 500サイクル後に、 0. 5Cの電 流で 4. I Vまで、 定電流定電圧充電を行って満充電状態とし、 直径 2 . 5 mmの釘を貫通させる安全性試験を行った。 この結果、 実施例 9〜 In Examples 9 to 16, after 500 cycles, a constant current and constant voltage charge was performed up to 4.IV with a current of 0.5 C up to 4.IV to make the battery fully charged, and a nail with a diameter of 2.5 mm was passed through. A sex test was performed. As a result, Examples 9 to
1 6のいずれの電池でも発煙や発火を示さず、 良好な安全性を示した。 産業上の利用可能性 None of the 16 batteries showed smoke or ignition, indicating good safety. Industrial applicability
本発明のリチウムイオン二次電池負極用炭素材料及びその負極用炭素 材料を用いたリチウムイオン二次電池は、 上述の構成よりなるので、 初 期容量が大きく、 初期効率及びサイクル特性に優れる。  Since the carbon material for a negative electrode of a lithium ion secondary battery of the present invention and the lithium ion secondary battery using the carbon material for a negative electrode have the above-described configuration, the initial capacity is large, and the initial efficiency and the cycle characteristics are excellent.

Claims

請 求 の 範 囲 The scope of the claims
1 . 炭素に、 ホウ素元素とケィ素元素を含有させてなるリチウムィ オン二次電池負極用炭素材料。  1. Carbon material for lithium ion secondary battery negative electrode, which contains boron element and silicon element in carbon.
2 . 炭素に、 ホウ素元素を 1〜2 0重量％含有させるとともに、 ケ ィ素元素を 0 . 0 1〜2 0重量％含有させてなるリチウムイオン二次電 池負極用炭素材料。 2. A carbon material for a negative electrode of a lithium ion secondary battery, comprising 1 to 20% by weight of boron element in carbon and 0.01 to 20% by weight of silicon element.
3 . ホウ素又はホウ素化合物及びケィ素又はケィ素化合物を含有す る炭素材を熱処理し、 粒度調整した炭素粉末からなる請求項 1又は 2記 載のリチウムィオン二次電池負極用炭素材料。 3. The carbon material for a negative electrode of a lithium ion secondary battery according to claim 1 or 2, comprising a carbon powder obtained by heat-treating a carbon material containing boron or a boron compound and a silicon or a silicon compound to adjust the particle size.
4 . 前記炭素材が、 炭素成形体である請求項 3記載のリチウムィォ ン二次電池負極用炭素材料。 4. The carbon material for a negative electrode of a lithium ion secondary battery according to claim 3, wherein the carbon material is a carbon compact.
5 . 前記ホウ素化合物がホウ素酸化物である請求項 3又は 4記載の リチウムイオン二次電池負極用炭素材料。 5. The carbon material for a negative electrode of a lithium ion secondary battery according to claim 3, wherein the boron compound is a boron oxide.
6 . 前記ケィ素化合物がケィ素酸化物である請求項 3〜 5の 、ずれ か一項に記載のリチウムィオン二次電池負極用炭素材料。 6. The carbon material for a negative electrode of a lithium ion secondary battery according to any one of claims 3 to 5, wherein the silicon compound is a silicon oxide.
7 . 前記熱処理における最終的な温度条件が、 2 4 0 0 °C以上であ る請求項 3〜 6のいずれか一項に記載のリチウムィオン二次電池負極用 炭素材料。 7. The carbon material for a negative electrode of a lithium ion secondary battery according to any one of claims 3 to 6, wherein a final temperature condition in the heat treatment is 240 ° C or more.
8 . 負極用炭素材料中に含有されるホウ素元素及びケィ素元素が、 化学気相蒸着法 （CVD法） 又は化学気相反応法 （CVR法） により炭 素材にとり込まれたものである請求項 1又は 2記載のリチウムイオン二 次電池負極用炭素材料。 8. The boron element and the silicon element contained in the carbon material for the negative electrode are 3. The carbon material for a negative electrode of a lithium ion secondary battery according to claim 1, wherein the carbon material is incorporated into the carbon material by a chemical vapor deposition method (CVD method) or a chemical vapor reaction method (CVR method).
9. 前記炭素材が黒鉛化炭素材又は黒鉛であり、 前記 CVD法又は C V R法の対象となるホウ素元素源が、 ホゥ素酸化物又はホゥ素ハロゲ ン化物であり、 前記 C V D法又は C V R法の対象となるケィ素元素源が 、 ケィ素酸化物又はケィ素ハロゲン化物である請求項 8記載のリチウム ィオン二次電池負極用炭素材料。 9. The carbon material is a graphitized carbon material or graphite, and the boron element source to be subjected to the CVD method or the CVR method is a boron oxide or a boron halide; 9. The carbon material for a negative electrode of a lithium ion secondary battery according to claim 8, wherein the target silicon element source is a silicon oxide or a silicon halide.
10. 1. 3 V 〔vsL i /L i - 〕 以上での放電容量として、 0〜0 . 25 V 〔vsL i /L i― 〕 までの放電容量の 1 %以上を有する請求項 1〜 9のいずれか一項に記載のリチウムィオン二次電池負極用炭素材料 10.1.3 Claims 1 to 9 which have a discharge capacity at 1 V or more of 0 to 0.25 V [vsL i / L i-] as a discharge capacity at 0.3 V [vsL i / L i-] or more. Carbon material for a negative electrode of a lithium ion secondary battery according to any one of the above
1 1. 炭素に、 ホウ素元素とケィ素元素を含有させ、 下記の①〜③の レ、ずれか一つ又は二以上の組合せが施されたリチウムィオン二次電池負 極用灰素材料。 1 1. An ash material for negative electrodes of lithium ion secondary batteries in which carbon contains boron element and silicon element, and one or a combination of two or more of the following ① to ③ is applied.
① ホウ素元素及びケィ素元素を含有させた炭素材にピッチ又は樹脂 を含浸又はコ一トして焼成したのち、 粉砕して炭素粉末にすること。 ① Carbon material containing boron and silicon elements should be impregnated or coated with pitch or resin, fired, and then ground to carbon powder.
② ホウ素元素及びケィ素元素を含有させた炭素粉末を、 粉体嵩密度 が 0. 5 (g/cm3 ) 以上、 且つ吸油量が 100 (m 1 /100 g) 以下に調整すること。 ② Carbon powder containing boron element and silicon element should be adjusted to have a powder bulk density of 0.5 (g / cm 3 ) or more and an oil absorption of 100 (m 1/100 g) or less.
③ ホウ素元素及びケィ素元素を含有させた炭素粉末にリン酸を添加 したのち熱処理すること。 ③ Heat treatment after adding phosphoric acid to carbon powder containing boron element and silicon element.
1 2 . 請求項 1〜 1 1のいずれかに記載の負極用炭素材料を負極活物 質として用いてなるリチウムイオン二次電池。 12. A lithium ion secondary battery using the carbon material for a negative electrode according to any one of claims 1 to 11 as a negative electrode active material.
PCT/JP1998/002127 1997-05-19 1998-05-13 Carbonaceous material for the anode of lithium ion secondary cell and lithium ion secondary cell made by using the carbonaceous material WO1998053511A1 (en)

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