JP2015011870A - Electrode active material, electrode and power storage device - Google Patents

Abstract

An electrode active material capable of obtaining an electricity storage device with good cycle characteristics is provided. A carbon material containing at least one component (A) selected from the group consisting of metals, metalloids and oxides thereof, and a coating carbon material covering at least a part of the carbon material. An electrode active material. [Selection figure] None

Description

  The present invention relates to an electrode active material, an electrode, and an electricity storage device, and more specifically, an electrode active material suitably used for an electricity storage device such as a lithium ion secondary battery and a lithium ion capacitor, an electrode containing the electrode active material, And an electricity storage device including the electrode as a negative electrode.

  2. Description of the Related Art In recent years, progress in downsizing and weight reduction of electronic devices has been remarkable, and accordingly, demands for downsizing and weight reduction of batteries used as power sources for driving the electronic devices are further increased. In order to satisfy such demands for reduction in size and weight, nonaqueous electrolyte secondary batteries represented by lithium ion secondary batteries have been developed as power storage devices. In addition, an electric double layer capacitor is known as an electric storage device having characteristics such as high output density and good cycle performance. Further, lithium ion capacitors that combine the storage principles of lithium ion secondary batteries and electric double layer capacitors are attracting attention as power storage devices for applications that require high energy density characteristics and high output characteristics.

  As a negative electrode active material used for such an electricity storage device, a graphite-based material is generally used. However, since the capacity of the graphite-based active material has an upper limit (372 mAh / g), a negative electrode active material capable of further increasing the capacity is demanded. On the other hand, as a negative electrode active material exhibiting a high charge / discharge capacity, an active material containing a metal, a semimetal or an oxide thereof that can be alloyed with lithium, such as Si, Ge, Ag, In, Sn, Pb, etc. Consideration is ongoing. However, an active material containing these metals and the like has a problem that the volume change due to charging / discharging is large, and detachment from the electrode occurs due to repeated charging / discharging, which deteriorates the cycle characteristics of the electricity storage device.

  In order to deal with this problem, Patent Document 1 proposes to use a negative electrode active material in which Si or Sn is dispersed in amorphous carbon. In Patent Document 2, metal nanoparticles and MOx (M = Si) are proposed. , Sn, etc.) A negative electrode active material for a lithium secondary battery in which a nanoparticle-present core and a core containing crystalline carbon are coated with a coating layer containing amorphous carbon has been proposed. There has been proposed an electrode material using a carbonaceous material in which the surface of carbon particles supporting at least Sn is further coated with a carbon material.

JP 2010-153346 A JP 2012-99452 A JP 2003-242979 A

However, in a power storage device using a conventional active material containing a metal, a semimetal or an oxide thereof, a practical cycle characteristic has not yet been realized.
Accordingly, an object of the present invention is to provide an electrode active material containing a metal, a metalloid and / or an oxide thereof, which can obtain an electricity storage device having good cycle characteristics.

  The present invention relates to a carbon material containing at least one component (A) selected from the group consisting of metals, metalloids and oxides thereof (hereinafter also referred to as “metal-containing carbon”), and the carbon material. An electrode active material comprising a coating carbon material covering at least a part is provided.

  Moreover, this invention provides the electrode containing the said electrode active material, Furthermore, the electrical storage device provided with the said electrode as a negative electrode is provided.

  By using the electrode active material of the present invention, an electricity storage device having a high capacity and excellent cycle characteristics can be obtained. Therefore, the electrode active material of the present invention is extremely useful as an electrode material for power storage devices such as lithium ion capacitors and lithium ion secondary batteries.

1 shows a scanning electron microscope (SEM) photograph of a cross section of the electrode active material obtained in Example 1. FIG. 2 is a schematic diagram showing an example of a cross section of the electrode active material obtained in Example 1. FIG.

Hereinafter, the present invention will be described in detail.
Electrode active material The electrode active material of the present invention covers a carbon material containing at least one component (A) selected from the group consisting of metals, metalloids and oxides thereof, and at least a part of the carbon material. It contains a carbon material for coating. Here, the “carbon material containing component (A)” does not mean a state in which metal particles or the like are supported on the surface in contact with the outside of the carbon material, but the carbon material is contained in the component (A ) And means that component (A) is confined in carbon.

  In addition, when manufacturing metal inclusion carbon, a one part component (A) exists also in the metal inclusion carbon surface normally. As a result of intensive studies that the present inventors have considered that the component (A) present on the carbon surface is desorbed due to charge and discharge, and thus deteriorates the cycle characteristics, the carbon adheres to the metal-encapsulated carbon surface. The present invention has been completed by finding that the above-mentioned problems can be solved by further coating the metal-encapsulated carbon with a carbon material in order to prevent desorption associated with charge / discharge of the component (A).

In the electrode active material of the present invention, the metal or metalloid is not particularly limited, but is preferably a metal or metalloid capable of forming an alloy with lithium, for example, Si, Ge, Ag, In, Sn, Pb, Mg, Ti, V, Cd, Se, Mn, Pt, and B are mentioned. In the electrode active material of the present invention, the metal or metalloid may be an alloy containing these metal or metalloid. Among these, Si or Sn is preferable because an electrode active material capable of exhibiting a particularly high lithium storage / release capacity can be obtained.
As the metal or metalloid oxide, for the same reason, an oxide of Si or Sn is preferable.

The component (A) is preferably finely dispersed in carbon, and the particle diameter thereof is preferably 1 to 200 nm, particularly preferably 1 to 100 nm.
Furthermore, the component (A) preferably contains a component having a crystallite size determined from the first peak in the X-ray diffraction spectrum of 500 angstroms or less, and particularly preferably contains a component having a crystallite size of 400 angstroms or less.

  The first peak in the X-ray diffraction spectrum is the height of the peak derived from the component (A) crystal in the X-ray diffraction spectrum (when there are multiple types of component (A), each component (A)) is the height. Is the highest peak. In addition, if it is a known crystal, it can be known from the powder diffraction database ICDD (manufactured by Lightstone Co., Ltd.) which peak is the first peak in the X-ray diffraction spectrum. For example, in Sn, the diffraction peak derived from the (200) plane is the first peak.

The component (A) having such a structure can disperse the stress caused by the volume change of the component (A) accompanying charge / discharge, and as a result, an electricity storage device having excellent cycle characteristics can be obtained. it is conceivable that.
The particle diameter and crystallite size of component (A) can be measured by the methods described in the following examples.

Although it does not specifically limit as a carbon material which comprises metal inclusion carbon, and a coating carbon material, The following results are shown when graphiticity is evaluated by Raman spectroscopic analysis about the electrode active material of the present invention. It is preferable. That is, the Raman spectrum has a D band and a G band, and the ratio ID / IG of each intensity ID and IG is preferably 0.3 to 1.0, and preferably 0.5 to 1.0. It is particularly preferred. Here, the intensity ID of the D band means the height of a peak recognized in the vicinity of 1360 cm ⁻¹ in the Raman spectrum, while the intensity IG of the G band means a peak recognized in the vicinity of 1580 cm ^{−1 in} the Raman spectrum. Means the height of When the carbon material constituting the metal-encapsulating carbon and the covering carbon material have such a structure, an electricity storage device having a higher desired effect can be obtained.

The specific surface area of the electrode active material of the present invention is preferably 0.01~100m ² / g, particularly preferably 0.1 to 50 m ² / g. If the specific surface area is too small, the internal resistance of the obtained electrode may be increased. On the other hand, if the specific surface area is too large, the strength of the obtained electrode may be insufficient or the Coulomb efficiency may be reduced.
The specific surface area can be measured by the method described in the following examples.

  The electrode active material of the present invention can be produced by an appropriate method. An organic polymer particle containing the component (A) (hereinafter also simply referred to as “organic polymer particle”) is coated with a carbon material for coating. It is preferable to manufacture by coating with an organic compound to become, and then heating in the presence of an inert gas.

  The organic polymer particles can be produced, for example, by subjecting an organic monomer to emulsion polymerization or suspension polymerization together with the component (A). As the emulsion polymerization method or suspension polymerization method, a known method can be employed.

  The organic monomer used for the production of the organic polymer particles is not particularly limited. For example, vinyl monomers such as styrene, (meth) acrylic acid, (meth) acrylic acid ester, acrylonitrile, butadiene, and divinylbenzene. An addition condensation type monomer obtained by combining phenol, cresol, melamine, resorcinol and the like with aldehydes, hexamethylenetetramine and the like; The organic monomers used for the production of the organic polymer particles can be used alone or in combination of two or more.

  In order to finely disperse component (A) in carbon, it is preferable to polymerize after dispersing component (A) and the organic monomer in the system using a dispersant. As the dispersant, known dispersants such as cationic, anionic and nonionic can be used as appropriate, and they can be used alone or in combination of two or more.

When the organic polymer particles are subjected to emulsion polymerization or suspension polymerization, known emulsifiers and dispersants can be appropriately used.
Examples of the emulsifier include sulfate esters of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether disulfonates, aliphatic sulfonates, aliphatic carboxylates, dehydroabietic acid salts, naphthalene sulfonic acid / formalin condensates, Anionic surfactants such as sulfate ester salts of ionic surfactants; nonionic surfactants such as alkyl esters of polyethylene glycol, alkyl phenyl ethers of polyethylene glycol, alkyl ethers of polyethylene glycol; perfluorobutyl sulfonates; Fluorosurfactants such as perfluoroalkyl group-containing phosphate esters, perfluoroalkyl group-containing carboxylates, and perfluoroalkylethylene oxide adducts are listed. Is the may be used one or more kinds.

  Dispersants used when polymerizing organic polymer particles include natural glues based on water-soluble polysaccharide derivatives such as gum arabic, acacia, guar gum, locust bean gum, etc .; alkali metal salts or ammonium of carboxymethyl cellulose Salt; Polyvinyl alcohol etc. can be mentioned, One or more selected from these can be used.

  In addition, when manufacturing organic polymer particle | grains, in order to form a space | gap part inside the electrode active material of this invention, you may mix the organic solvent with low compatibility with the polymer obtained.

Examples of the organic compound that coats the organic polymer particles thus obtained include, for example, pitches such as petroleum pitch and coal pitch; polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyethylene, polyethylene terephthalate, polyvinyl Thermoplastic resins such as pyrrolidone, polyacrylonitrile, acrylonitrile styrene copolymer, acrylonitrile butadiene copolymer, styrene-ethylene / butylene-styrene block copolymer; thermosetting resins such as phenol resin, melamine resin, and epoxy resin be able to. The carbides of these organic compounds constitute the coating carbon material.
In this invention, the organic compound used as the carbon material for a coating can be used individually or in mixture of 2 or more types.

  In the present invention, when coating the organic polymer particles, a carbon material such as carbon black, vapor-grown carbon fiber, graphene, or carbon nanotube is mixed with the organic compound, thereby coating carbon containing these. Materials can also be used.

By heating the organic polymer particles coated with the organic compound in the presence of an inert gas, the particles can be carbonized to obtain the electrode active material of the present invention. Examples of the inert gas include N ₂ and argon. The heating temperature is preferably 500 to 2,000 ° C, particularly preferably 600 to 1,500 ° C. The heating time is preferably 30 minutes to 5 hours, particularly preferably 30 minutes to 3 hours. By performing an oxidation treatment before carbonization, the yield of the obtained electrode active material can be increased. The oxidation treatment can be performed, for example, by heating in an air atmosphere. The heating temperature during the oxidation treatment is preferably 100 to 500 ° C, particularly preferably 200 to 400 ° C. The heating time in the oxidation treatment is preferably 30 minutes to 8 hours, particularly preferably 1 to 5 hours.

  The electrode active material of the present invention gives a high capacity and excellent cycle characteristics to an electricity storage device using the electrode active material. The electrode active material of the present invention is preferably used as a negative electrode active material for a secondary battery, and particularly preferably used as a negative electrode active material for a lithium ion secondary battery.

Electrode The electrode of the present invention contains the electrode active material of the present invention and is usually formed by forming an active material layer containing the electrode active material of the present invention and a binder on a current collector. is there. The active material layer can be usually produced by preparing a slurry containing an electrode active material and a binder, applying the slurry on a current collector, and drying the slurry.

  The electrode of the present invention is preferably a negative electrode using the electrode active material of the present invention as a negative electrode active material, preferably a negative electrode of a secondary battery, particularly preferably a negative electrode of a lithium ion secondary battery. .

The content of the electrode active material of the present invention with respect to the entire active material layer is preferably 50 to 90% by mass.
The electrode active material of this invention can be used individually or in combination of 2 or more types.

The material of the current collector is preferably aluminum, stainless steel or the like when the electrode of the present invention is a positive electrode, while copper, nickel, stainless steel or the like is preferable when the electrode of the present invention is a negative electrode.
The thickness of the current collector is usually 10 to 50 μm regardless of whether the current is positive or negative.

  Examples of the binder include rubber-based binders such as styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR); fluorine-based resins such as polytetrafluoroethylene and polyvinylidene fluoride; polypropylene, polyethylene, and polyacrylic acid In addition, a fluorine-modified (meth) acrylic binder disclosed in JP-A-2009-246137 can be mentioned. Although the usage-amount of a binder is not specifically limited, Preferably it is 1-20 mass% with respect to the electrode active material of this invention.

  The active material layer further includes a conductive agent such as carbon black, graphite, and metal powder; carboxyl methyl cellulose, its Na salt or ammonium salt, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated Thickeners such as starch and casein may be contained.

The thickness of the active material layer is not particularly limited, but is usually 5 to 500 μm, preferably 10 to 200 μm, and particularly preferably 10 to 100 μm.
Moreover, when the density of the said active material layer is an electrode used for a lithium ion secondary battery, Preferably it is 1.50-2.00 g / cc, Most preferably, it is 1.60-1.90 g / cc. . When the density of the active material layer is within such a range, the balance between the liquid retention of the electrolytic solution and the contact resistance of the active material is good, so that an electricity storage device having a high capacity and a low resistance can be provided.

Electric storage device The electric storage device of the present invention comprises the electrode of the present invention as a negative electrode. Examples of the electricity storage device include a secondary battery and a lithium ion capacitor. In this invention, it is preferable that it is a lithium ion secondary battery provided with the electrode of this invention as a negative electrode.

  The electricity storage device of the present invention preferably includes at least a positive electrode and an electrolyte in addition to the electrode of the present invention used as a negative electrode. The configuration and manufacturing method of the electrode of the present invention used as the negative electrode are as described in the above “electrode”.

In the electricity storage device of the present invention, the basic configuration and manufacturing method of the positive electrode are the same as those described in the “electrode” except for the type of active material.
When the electricity storage device of the present invention is a lithium ion capacitor, examples of the positive electrode active material used include activated carbon and polyacene-based materials. On the other hand, when the electricity storage device of the present invention is a lithium ion secondary battery, examples of the positive electrode active material used include lithium transition metal composite oxides such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide, Examples thereof include transition metal oxides such as manganese dioxide and carbonaceous materials such as graphite fluoride. These positive electrode active materials can be used individually or in mixture of 2 or more types.

In the electricity storage device of the present invention, the electrolyte is usually used in the state of an electrolytic solution dissolved in a solvent. In the present invention, the electrolyte is preferably one that can generate lithium ions. Specifically, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (FSO ₂ ) _{2 and the} like. These electrolytes can be used alone or in admixture of two or more.

  As the solvent for dissolving the electrolyte, an aprotic organic solvent is preferable. Specifically, ethylene carbonate, propylene carbonate, butylene carbonate, 1-fluoroethylene carbonate, 1- (trifluoromethyl) ethylene carbonate, dimethyl Examples thereof include carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane and the like. These solvents can be used alone or in admixture of two or more.

  The concentration of the electrolyte in the electrolyte is preferably 0.1 mol / L or more, and more preferably in the range of 0.5 to 1.5 mol / L in order to reduce the internal resistance due to the electrolyte. preferable. The electrolyte may contain additives such as vinylene carbonate, vinyl ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, and diethyl sulfone.

  As described above, the electrolyte is usually prepared and used in a liquid state, but a gel or solid electrolyte may be used for the purpose of preventing leakage.

  When the electrolyte is used in the state of an electrolyte, a separator is usually provided between the positive electrode and the negative electrode so that the positive electrode and the negative electrode are not in physical contact. Examples of the separator include a nonwoven fabric or a porous film using cellulose rayon, polyethylene, polypropylene, polyamide, polyester, polyimide, or the like as a raw material.

  As the structure of the electricity storage device, for example, a laminated cell in which a laminated body in which three or more plate-like positive electrodes and negative electrodes are laminated via a separator is enclosed in an exterior film, and a strip-like positive electrode and negative electrode are separators. Examples include a wound cell in which a laminated body wound through a container is accommodated in a rectangular or cylindrical container.

  Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

  The following (1) to (6) were evaluated using the electrode active materials obtained in the following Examples and Comparative Examples. The results are shown in Table 3.

(1) Raman spectroscopic analysis The obtained electrode active material was subjected to Raman spectroscopic analysis using a laser with a wavelength of 532 nm using an inVia Reflex Raman microscope manufactured by Renishaw Corporation. From the obtained Raman spectrum, the ratio between the intensity (height, ID) of the peak of D band observed near 1360 cm ⁻¹ and the intensity (height, IG) of the peak of G band recognized near 1580 cm ^−1. ID / IG was measured.

(2) X-ray diffraction analysis The obtained electrode active material was subjected to X-ray diffraction analysis under the conditions shown in Table 1 using SmartLab manufactured by Rigaku Corporation. In the obtained X-ray diffraction spectrum, the crystallite size was calculated from the full width at half maximum of the peak of the (200) plane observed near 2θ = 30.5 °, which is the first peak of Sn.

(3) Measurement of particle diameter of component (A) The particle diameter of the component (A) contained in the obtained electrode active material was measured using the scanning electron microscope (SEM).

(4) Measurement of specific surface area The specific surface area of the obtained electrode active material was determined by BET method using BELSORP-miniII manufactured by Nippon Bell Co., Ltd.

(5) Measurement of powder resistance value About the obtained electrode active material, Mitsubishi Chemical Analytech Co., Ltd., the powder resistance measurement system MCP-PD51, and the resistivity meter MCP-T610, press pressure 38.2MPa The resistance value at the time of pressing with was measured.

(6) Evaluation of cycle characteristics (capacity retention ratio) 0.30 g of the obtained electrode active material, 0.017 g of acetylene black, 0.342 g of 3% aqueous solution of carboxymethylcellulose, 0.30 g of distilled water, and polyacrylic acid binder 046 g was mixed to prepare a slurry. The obtained slurry was applied to a Cu foil, preliminarily dried at 100 ° C. for 1 hour, and then dried at 200 ° C. under reduced pressure for 3 hours to obtain a negative electrode plate. The obtained negative electrode plate was cut into a diameter of 12 mm. In the glove box, a negative electrode plate cut into a circle, a separator with a diameter of 25 mm, and a Li foil cut with a diameter of 12.5 mm were superposed in this order and placed in a bipolar cell manufactured by Toyo System Co., Ltd. An appropriate amount of a 1.2M LiPF ₆ ethylene carbonate / diethyl carbonate = 30/70 (volume ratio) solution was added as an electrolytic solution to the obtained cell, followed by degassing under reduced pressure to complete an evaluation cell. .

  The produced cell was set in a charge / discharge evaluation apparatus manufactured by Toyo System Co., Ltd., and a 15-cycle charge / discharge test was performed under the conditions shown in Table 2. The capacity retention ratio (ratio of the discharge capacity at the 15th cycle to the discharge capacity at the 1st cycle) was evaluated as cycle characteristics.

[Example 1]
In a plastic container with a lid, SnO ₂ 14.2 g, 1,4-divinylbenzene 40.0 g, and 52.0 g of hexanoic acid as a dispersing agent, 2.6 g of BYK102 (manufactured by Big Chemie Japan) and SZ6030 (Toray Dow Corning Co., Ltd. (1.56 g) was added together with 400 g of dispersion ZrO ₂ beads (bead diameter 0.1 mm) and shaken for 1 hour in a paint shaker. Then, ZrO ₂ beads were removed by filtering with 7 μm pore Kiriyama filter paper to obtain a brown transparent liquid.

In a separable flask equipped with a nitrogen introduction tube, a stirring blade, a cooling tube, and a thermometer, the obtained brown transparent liquid 110.3 g, distilled water 926 g, polyvinyl alcohol 9.19 g, Na ₂ CO ₃ 0.92 g, dodecyl Sodium benzenesulfonate 0.74 g and NaNO ₂ 4.59 g were added, and the temperature was raised to 85 ° C. while stirring at 500 rpm. Thereafter, 0.76 g of azobisisobutylnitrile was added, and the polymerization reaction was performed by heating and stirring at 85 ° C. for 4 hours. The reaction solution was naturally cooled to 38 ° C., and then neutralized by adding 15 ml of 5N aqueous KOH solution. After stirring for 30 minutes, suction filtration was performed with 7 μm pore Kiriyama filter paper, and the obtained polymer particles were washed successively with 1 L of water and 1 L of ethanol. Then, 12 hours at 60 ° C. and dried in vacuo to afford the 1,4-divinylbenzene polymer particles containing a SnO _2.

4.0 g of coal tar pitch (coal pitch) was added to 12.0 g of tetrahydrofuran (THF), and the mixture was stirred at 83 ° C. for 1 hour using a magnetic stirrer to obtain a viscous liquid. To this viscous liquid, 2.0 g of 1,4-divinylbenzene polymer particles containing SnO ₂ was added and stirred for 1 hour under reduced pressure to perform defoaming treatment. Then, after stirring for 1 hour under reflux, THF was distilled off using an evaporator. Furthermore, by drying for 3 hours in a box-type muffle furnace set at 150 ° C., 1,4-divinylbenzene polymer particles encapsulating SnO ₂ coated with coal tar pitch were obtained.

The obtained polymer particles were heated to 350 ° C. at a temperature rising rate of 2 ° C./min in an air atmosphere using a box-type muffle furnace, and then subjected to oxidation treatment by heating at that temperature for 3 hours. . Using a tubular furnace, the temperature was raised to 800 ° C. at a rate of temperature rise of 12 ° C./min in a N ₂ stream, and then heated at that temperature for 1 hour to perform carbonization treatment to obtain an electrode active material. In this production example, SnO ₂ is reduced to Sn. The same applies to Examples 2-3 and Comparative Examples 1-2 described later.
Said evaluation was performed about the obtained electrode active material. The evaluation results are shown in Table 3.

Moreover, the SEM photograph which image | photographed the cross section of the obtained electrode active material is shown in FIG. 2 is a schematic diagram showing an example of a cross section of the electrode active material obtained in Example 1. FIG.
FIG. 1 is an enlarged photograph of a part of a cross-section of the obtained electrode active material, specifically, a part surrounded by a square broken line in FIG.
In FIG. 1, the gray part including the white point (lower left of the photograph) is metal-encapsulated carbon, and it can be seen that the component (A) (white point) is included in the carbon material (gray part). Moreover, in FIG. 1, a black part (upper part of a photograph) is the carbon material for a coating | cover which coat | covers metal inclusion carbon.
From FIG. 1, it is clear that the electrode active material obtained in Example 1 contains a carbon material containing component (A) and a coating carbon material covering the carbon material.

[Example 2]
In Example 1, an electrode active material was produced in the same manner as in Example 1 except that the carbonization temperature was changed to 1350 ° C.

[Example 3]
In a plastic container with a lid, SnO ₂ 3.0 g, phenol 4.2 g, toluene 8.9 g, dispersant BYK102 (manufactured by Big Chemie Japan Co., Ltd.) 1.5 g, and dispersion ZrO ₂ beads (bead diameter 0.1 mm) 90 g was added and shaken for 1 hour in a paint shaker. Then, ZrO ₂ beads were removed by filtering with 7 μm pore Kiriyama filter paper to obtain a brown transparent liquid.

In a separable flask equipped with a nitrogen introduction tube, a stirring blade, a cooling tube, and a thermometer, 17.7 g of the obtained brown transparent liquid, 280 g of distilled water, 2.3 g of gum arabic, 2.3 g of nonionic surfactant, 12.7 g of a 37 wt% aqueous solution of formaldehyde and 0.4 g of a 10 wt% aqueous solution of dodecylbenzenesulfonic acid were added, and the temperature was raised to 85 ° C. in a hot water bath while stirring at 350 rpm. After 1 hour, the temperature was raised to the reflux temperature. After reaching the reflux temperature, 1.0 g of a 10 wt% aqueous solution of dodecylbenzenesulfonic acid was added every 20 minutes, and a total of 8.4 g was added together with the initial charge. . After refluxing for a total of 3 hours, 12.7 g of a 37 wt% aqueous solution of formaldehyde was added. As the resin solidified in the reaction system, the hot water bath was removed and the solution was naturally cooled to 38 ° C. Subsequently, it neutralized by adding 40 ml of 0.1N NaOH aqueous solution. Thereafter, the supernatant was removed by decantation, suction filtered through a 7 μm pore Kiriyama filter paper, and the obtained polymer particles were washed successively with 1 L of water and 1 L of ethanol. Then, 12 hours at 60 ° C. and dried in vacuo to afford the phenol resin particles containing a SnO _2.
The obtained phenol resin particles encapsulating SnO ₂ were coated with coal tar pitch in the same manner as in Example 1, and an oxidation treatment and a carbonization treatment were performed to obtain an electrode active material.

[Comparative Example 1]
Using a tubular furnace, the phenol resin particles encapsulating SnO ₂ obtained in Example 3 were heated to 800 ° C. at a temperature rising rate of 12 ° C./min in a N ₂ stream, and then heated at that temperature for 1 hour. Electrode active material was obtained by carbonizing.

[Comparative Example 2]
The phenol resin particles encapsulating SnO ₂ obtained in Example 3 were immersed in 1N hydrochloric acid, shaken for 30 seconds, and allowed to stand for 1 minute. Thereafter, 10 times as much pure water as hydrochloric acid was added and diluted, and then filtered through Kiriyama filter paper having a pore size of 7 μm. After the phenol resin particles encapsulating SnO ₂ are acid-washed in this way, the temperature is raised to 800 ° C. at a rate of temperature rise of 12 ° C./min in a N ₂ stream using a tubular furnace, and then at that temperature for 1 hour. An electrode active material was obtained by heating and carbonization.

1: Electrode active material 2: Carbon material for coating 3: Carbon material containing component (A) 4: Component (A)

Claims (6)

  An electrode comprising a carbon material containing at least one component (A) selected from the group consisting of metals, metalloids and oxides thereof, and a coating carbon material covering at least a part of the carbon material Active material.   The electrode active material according to claim 1, wherein the component (A) includes a component having a crystallite size of 500 angstroms or less determined from a first peak in an X-ray diffraction spectrum.   The electrode active material according to claim 1 or 2, wherein the Raman spectrum has a D band and a G band, and the ratio ID / IG of each intensity ID and IG is 0.3 to 1.0.   The electrode active material of any one of Claims 1-3 in which the said component (A) contains at least 1 sort (s) chosen from the group which consists of Si, Sn, and those oxides.   The electrode containing the electrode active material of any one of Claims 1-4.   An electricity storage device comprising the electrode according to claim 5 as a negative electrode.