JP2005259378A - Carbon material for positive electrode activator of nonaqueous electrolytic solution secondary battery, positive electrode of nonaqueous electrolytic solution secondary battery and nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon material for a positive electrode activator of a nonaqueous electrolytic solution secondary battery with high-density and high-capacity, a positive electrode of a nonaqueous electrolytic solution secondary battery including the carbon material, and a nonaqueous electrolytic solution secondary battery using the positive electrode. <P>SOLUTION: As to the carbon material for the positive electrolytic activator of the nonaqueous electrolytic solution secondary battery composed of at least a positive electrode to/from which mainly anion is inserted/separated; a negative electrode capable of storing and releasing metallic lithium or lithium ions; and a nonaqueous electrolytic solution made by dissolving a lithium salt into a nonaqueous solvent, the material having X-ray diffraction intensity ratio I<SB>2θ=22.3</SB>/I<SB>2θ=26.4</SB>by the CuKα-line of 0.15 or less, (wherein I<SB>2θ=22.3</SB>, I<SB>2θ=26.4</SB>represent diffraction intensities at 2θ=22.3°, 2θ=26.4°, respectively) is used. A carbonaceous material with ≤0.15 of I<SB>2θ=22.3</SB>/I<SB>2θ=26.4</SB>is one with a low content of amorphous carbon and the ratio of the amorphous carbon contained in the carbonaceous material is low, so that a high discharging-capacity positive electrode of a nonaqueous electrolytic solution secondary battery can be realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carbon material for a positive electrode active material of a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery positive electrode including the carbon material, and a non-aqueous electrolyte secondary battery using the positive electrode.

  In recent years, non-aqueous electrolyte secondary batteries having high energy density have been developed with the reduction in weight and size of electrical products. In addition, as the application field of non-aqueous electrolyte secondary batteries expands, improvements in battery characteristics are desired.

  A non-aqueous electrolyte secondary battery is composed of at least a positive electrode and a negative electrode, and a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent. The negative electrode can occlude and release metallic lithium and lithium ions. Metals, metal compounds (including oxides and alloys with lithium), and carbonaceous materials are used.

  In particular, as a carbonaceous material, for example, a nonaqueous electrolyte secondary battery using a carbonaceous material capable of inserting and extracting lithium such as coke, artificial graphite, and natural graphite has been proposed. In such a non-aqueous electrolyte secondary battery, since lithium does not exist in a metal state, dendrite formation is suppressed, and battery life and safety can be improved. In particular, non-aqueous electrolyte secondary batteries using graphite-based carbonaceous materials such as artificial graphite and natural graphite are attracting attention as meeting the demand for higher capacity.

  On the other hand, as positive electrode active materials for non-aqueous electrolyte secondary batteries, two types of positive electrode active materials are known depending on the form of reaction during charging and discharging.

In the first type, lithium ions are desorbed and inserted between the crystal layers, and the charge / discharge is performed. For example, transition metals such as Fe, Co, Ni, Mn, V, and Ti are used. Inorganic compounds such as oxides, composite oxides of these transition metals and lithium, and sulfides are known. _{Specifically, MnO, V 2 O 5,} V 6 O 13, TiO transition metal oxides such as _2, lithium-nickel composite oxide basic composition is LiNiO _2, lithium-cobalt complex oxide is LiCoO _2, LiMnO ₂ or LiMn ₂ O ₄ , such as a lithium-manganese composite oxide, a composite oxide of lithium and a transition metal, and transition metal sulfides such as TiS ₂ and FeS. Among them, lithium and transition metal composite oxides such as lithium nickel composite oxide, lithium cobalt composite oxide, and lithium manganese composite oxide are preferably used because they can achieve both high capacity and high cycle characteristics. ing.

  The second type is a positive electrode such as a conductive polymer or carbonaceous material in which only anions are mainly inserted / extracted. For example, polyaniline, polypyrrole, polyparaphenylene, graphite, etc. can be used. Are known.

In the battery using this second type of positive electrode active material, charging is performed by inserting an anion such as PF ₆ ⁻ into the positive electrode and Li ⁺ into the negative electrode from the electrolyte, and PF ₆ from the positive electrode. ^The discharge is performed when Li ⁺ is desorbed from the negative electrode, such as ⁻ . An example of such a battery is a dual carbon cell using graphite as the positive electrode, pitch coke as the negative electrode, and lithium perchlorate dissolved in a mixed solvent of propylene carbonate and ethyl methyl carbonate as the electrolyte. It has been.

  Non-Patent Document 1 reports a value of 24 mAh / g as the discharge capacity of the positive electrode active material when the positive electrode active material is graphite and the reference electrode is lithium metal and charged to 4.75 V and discharged to 3.0 V. Yes.

In addition, as a solvent for the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery, an aprotic solvent having a high decomposition voltage and a high dielectric constant is used. For example, a mixed solvent such as propylene carbonate and ethyl methyl carbonate is used. Used.
DENKI KAGAKU, 48 (8), 438 (1978)

  In a non-aqueous electrolyte secondary battery, a higher density and higher capacity positive electrode material is required for higher capacity. Conventionally, when a carbon material is used as a positive electrode active material, the capacity is increased. There was a problem of being insufficient. Moreover, it was not clear what kind of physical property the carbon material has a high capacity.

  The present invention relates to a carbon material for a positive electrode active material of a high-density, high-capacity non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery positive electrode containing the carbon material, and a non-aqueous electrolyte using the positive electrode An object is to provide a secondary battery.

The present inventors at least comprise at least a positive electrode through which anions are inserted / desorbed, a negative electrode capable of inserting and extracting metallic lithium or lithium ions, and a non-aqueous electrolyte solution obtained by dissolving a lithium salt in a non-aqueous solvent. As a result of various studies on the carbon material for the positive electrode active material of the non-aqueous electrolyte secondary battery, the crystallinity is high, and the X-ray diffraction intensity ratio by CuKα ray is I _{2θ = 22.3} / I _{2θ = 26.4} (however, , I _{2θ = 22.3} and I _{2θ = 26.4} represent the diffraction intensity at 2θ = 22.3 ° and 2θ = 26.4 °, respectively. The present invention was completed by finding that it exhibits performance.

That is, the present invention comprises at least a positive electrode in which anions are mainly inserted and desorbed, a negative electrode capable of inserting and extracting metallic lithium or lithium ions, and a non-aqueous electrolyte solution obtained by dissolving a lithium salt in a non-aqueous solvent. In the positive electrode active material carbon material used for the non-aqueous electrolyte secondary battery, the X-ray diffraction intensity ratio by CuKα ray I _{2θ = 22.3} / I _{2θ = 26.4} (where I _{2θ = 22.3} , I _{2θ = 26.4} represents the diffraction intensity at 2θ = 22.3 ° and 2θ = 26.4 °), respectively, and is 0.15 or less. The gist is the carbon material for the positive electrode active material.

  The interplanar spacing d (002) of the 002 plane of the graphite crystal of the carbon material for the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention is usually further improved by setting it to 3.34 angstroms or more and 3.38 angstroms or less. Performance.

  The non-aqueous electrolyte secondary battery positive electrode of the present invention is characterized by including the carbon material for a positive electrode active material of the present invention.

  The nonaqueous electrolyte secondary battery of the present invention has such a positive electrode of the present invention.

As the diffraction intensity according to the present invention, a value obtained by subtracting the background intensity at the angle from the X-ray intensity at each angle is used. The diffraction intensity at 2θ = 22.3 ° is derived from amorphous carbon, and the diffraction intensity at 2θ = 26.4 ° is derived from graphite crystals. Therefore, I _{2θ = 22.3} / I _{2θ = 26.4} being 0.15 or less means that the proportion of amorphous carbon contained in the carbonaceous material of the present invention is small. Although the detailed reason is unknown, the small amount of amorphous carbon contained in the carbonaceous material traps anions inserted into the positive electrode active material by charging, making it impossible to desorb during discharge. It is surmised that the rate of

  The interplanar spacing d (002) of the 002 plane of the graphite crystal according to the present invention is determined by a method determined by the Japan Society for the Promotion of Science 117 (Japan Society for the Promotion of Science, carbon, 25, 36, 1963). The value of d (002) is a value corresponding to the graphite layer, and the value of 3.34 angstroms or more and 3.38 angstroms or less is suitable for insertion / extraction of anions between the graphite layers. It is assumed that there is.

  According to the present invention, a high-capacity nonaqueous electrolyte secondary battery is provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention. It is not specified in the contents of.

[Configuration of non-aqueous electrolyte secondary battery]
(1) Positive electrode In the present invention, the carbonaceous material used as the positive electrode active material has a diffraction intensity I _{2θ = 22.3} at 2θ = 22.3 ° and 2θ = 2θ in a powder X-ray diffraction pattern using CuKα rays. The intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of the diffraction intensity I _{2θ = 26.4} at 26.4 ° has high crystallinity of 0.15 or less.

As described above, the X-ray diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} by CuKα rays (hereinafter simply referred to as “diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} ”). Of 0.15 or less means that the content ratio of amorphous carbon is small. As described above, carbon materials having a small content ratio of amorphous carbon are coal pitch coke, petroleum pitch coke. , A carbon selected from needle coke, mesophase pitch-based carbon fiber, mesocarbon microbead, carbon black, thermal black, condensable polycyclic polynuclear aromatic hydrocarbon, etc. It is selected from artificial graphite and / or natural graphite obtained by heat treatment at a temperature of 0 ° C. or higher. In addition, it is possible to use those artificial graphite and / or natural graphite that are further reduced in the content ratio of amorphous carbon by heat treatment in an oxygen-containing atmosphere.

  Further, the carbon material for the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention has an interplanar spacing d (002) of the 002 plane of the graphite crystal of usually 3.34 angstroms or more, preferably 3.341 angstroms or more, and Preferably, it is 3.342 angstroms or more, usually 3.38 angstroms or less, preferably 3.375 angstroms or less, more preferably 3.37 angstroms or less, and even better performance is exhibited. The reason for this is not clear, but it is presumed that the carbon material having the value of d (002) defined above has an effective graphite layer in the insertion / extraction of anions.

The positive electrode active material for a carbon material of the present invention may also be in the Raman spectrum analysis using argon laser beam, the intensity _{I A} of the peak _{P A} is detected in the range of 1580～1620Cm ^-1, range of 1350 ^-1 in intensity ratio _I a / _{I B} of the intensity _{I B} of a peak _{P B} detected (hereinafter referred to as "peak intensity ratio _I a / _{I B.")} is preferably not more than 0 and 0.5 or less, peak half-width of _{P a} is 26cm ^-1 or less, and particularly preferably 25 cm ^-1 or less.

The BET specific surface area of the carbon material for positive electrode active material of the present invention is usually 1 m ² / g or more and 100 m ² / g or less, and the median diameter determined by the laser diffraction / scattering method is usually 0.1 μm or more. 100 μm or less is preferable.

  The method for producing the positive electrode using such a carbon material is not particularly limited. For example, it can be manufactured by adding a binder, a thickener, a conductive material, a solvent or the like to the above-described carbon material as necessary to form a slurry, applying the slurry to a substrate of a current collector, and drying. . Further, the carbon material can be roll-formed as it is to obtain a sheet electrode, or a pellet electrode by compression molding.

  The binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used in electrode production. Specific examples include polyvinylidene fluoride, polytetrafluoroethylene, styrene / butadiene rubber, and isoprene rubber. And butadiene rubber.

  Examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.

  Examples of the conductive material include metal materials such as copper and nickel, and carbonaceous materials such as graphite and carbon black. In particular, the positive electrode preferably contains a conductive material.

  The solvent used for the production of the positive electrode may be aqueous or organic. Examples of the aqueous solvent include water and alcohol, and examples of the organic solvent include N-methylpyrrolidone (NMP) and toluene.

  As a material for the current collector for the positive electrode, metals such as aluminum, titanium, and tantalum are used. Among these, aluminum foil is preferable from the viewpoint of easy processing into a thin film and cost.

(2) Negative electrode As the negative electrode material (negative electrode active material), metal lithium or a material capable of inserting and extracting lithium ions is used. For example,
(1) Lithium metal
(2) Carbonaceous material
(3) Examples include metals and metal compounds capable of inserting and extracting lithium ions. Among these, specific examples of metals and metal compounds capable of inserting and extracting lithium ions include the following.
(3) -1 Metal oxide capable of occluding and releasing lithium, such as tin oxide, antimony tin oxide, silicon monoxide, vanadium oxide
(3) -2 Metals that can be alloyed with lithium such as aluminum, silicon, tin, antimony, lead, arsenic, zinc, bismuth, copper, cadmium, silver, gold, platinum, palladium, magnesium, sodium, potassium
(3) -3 Alloys containing the above metals (including intermetallic compounds)
(3) -4 Metal that can be alloyed with lithium and a composite alloy compound of lithium and an alloy containing the metal
(3) -5 Lithium metal nitride such as cobalt lithium nitride These negative electrode materials may be used alone or in combination of two or more.

  As the negative electrode material, a carbonaceous material is preferable in terms of safety and cost.

  As the carbonaceous material, graphite (graphite) such as artificial graphite and natural graphite, pyrolyzate of organic matter under various pyrolysis conditions, and the like can be used.

The BET specific surface area of carbonaceous materials such as graphite materials used as the negative electrode material is usually 0.5 m ² / g or more and 25.0 m ² / g or less, and the median diameter determined by the laser diffraction / scattering method is Usually, it is preferably 1 μm or more and 100 μm or less.

  A method for producing a negative electrode using such a negative electrode material is not particularly limited. For example, a negative electrode can be produced by adding a binder, a thickener, a conductive material, a solvent, and the like to the negative electrode material as necessary to form a slurry, which is applied to a substrate of a current collector and dried. it can. In this case, it can be manufactured in the same manner as the positive electrode manufacturing method described above.

  In addition, the negative electrode material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, a pellet electrode by compression molding, or deposition, sputtering, plating, etc. on the current collector A thin film of negative electrode material can also be formed.

  As the material for the current collector for the negative electrode, metals such as copper, nickel, and stainless steel are used, and among these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

(3) Non-aqueous electrolyte As the solvent of the non-aqueous electrolyte, an aprotic organic solvent is used. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons , Ethers, amines, esters, amides, phosphate ester compounds, and the like can be used. Listed as representative of these are 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate, vinylene carbonate, methyl formate, dimethyl sulfoxide, propylene carbonate, acetonitrile, γ-butyrolactone, dimethylformamide, dimethyl carbonate, diethyl carbonate, sulfolane, ethyl methyl carbonate, 1,4-dioxane, 4-methyl-2-pentanone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl Examples include ether, sulfolane, methylsulfolane, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, trimethyl phosphate, and triethyl phosphate. It is. These solvents may be used alone or in combination of two or more, but preferably contain a high dielectric constant solvent having a relative dielectric constant of 20 or more.

  As the solvent, it is particularly preferable to use a mixture of ethylene carbonate and dimethyl carbonate, and the mixing ratio is usually ethylene carbonate: dimethyl carbonate = 1: 1 to 1:10 (volume ratio).

Lithium salts as solutes include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiB (C ₆ H ₅ ) ₄
LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ or the like can be used, and these electrolytes may be used alone or in combination of two or more.

  When the solute concentration in the electrolytic solution is reduced by charging and the solute concentration becomes 0, charging cannot be performed any more. Therefore, it is necessary to contain an amount of solute corresponding to the capacity of the positive electrode and the negative electrode in the electrolytic solution. When the solute concentration is low, a large amount of electrolyte solution is required in the battery. Therefore, it is preferable that the solute concentration in the electrolyte solution is high. In some cases, the solute can be deposited in the solvent in the discharged state. From such points, the lower limit of the concentration of the lithium salt in the non-aqueous electrolyte is usually 0.05 mol / L or more, preferably 0.5 mol / L or more, particularly preferably 1 mol / L or more, and the upper limit is usually 5 mol / L. L or less, preferably 4 mol / L or less, particularly preferably 3 mol / L or less. Below this lower limit, the conductivity decreases or a large amount of electrolyte is required to secure a solute suitable for the capacity of the positive and negative electrodes, so the energy density per weight or volume of the battery tends to decrease. . On the other hand, when the upper limit is exceeded, there is a possibility that a solute precipitates or the conductivity decreases.

(4) Separator In the nonaqueous electrolyte secondary battery of the present invention, a separator is usually interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. The material and shape of the separator used in the non-aqueous electrolyte secondary battery of the present invention are not particularly limited, but it is preferable to select from materials that are stable with respect to the non-aqueous electrolyte described above and excellent in liquid retention. It is preferable to use a porous sheet or a nonwoven fabric made of a polyolefin such as polyethylene or polypropylene.

(5) Battery manufacturing method The non-aqueous electrolyte secondary battery of the present invention is manufactured by assembling the positive electrode, the negative electrode, and the non-aqueous electrolyte described above and a separator used as necessary into an appropriate shape. The Furthermore, other components such as an outer case can be used as necessary. The method for assembling the battery is not particularly limited, and may be appropriately selected from methods usually employed.

  The shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be appropriately selected from various commonly employed shapes according to the application. Examples of the shape include a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like. The nonaqueous electrolyte secondary battery may be assembled by a known method in accordance with the shape of the target battery.

[Charging method of non-aqueous electrolyte secondary battery]
When charging the non-aqueous electrolyte secondary battery of the present invention, when the charge end voltage of the positive electrode is expressed using lithium as a reference electrode, it is usually 4.3 V or higher, preferably 4.5 V or higher, particularly preferably 4.6 V. In the above manner, it is preferable to charge to a voltage expressed as 5.6 V or less, preferably 5.55 V or less, particularly preferably 5.5 V or less. If the end-of-charge voltage is below this lower limit, a high capacity cannot be obtained, and if it exceeds the upper limit, the solvent of the non-aqueous electrolyte solution is likely to decompose, which is not preferable.

  Charging is preferably performed up to the above state with lithium as a reference electrode with respect to the positive electrode, but the end-of-charge voltage of the battery when graphite or silicon is used for the negative electrode is about 0.1 V lower than the above. Is preferred. This is due to the following reason. That is, graphite, silicon or the like has a voltage of about 0.1 V with respect to lithium at the charging end. Therefore, the charge termination voltage of a battery using a positive electrode and a negative electrode such as graphite or silicon is about 0.1 V lower than that in the case where lithium is used as a reference electrode with respect to the positive electrode, so that the charged state of the positive electrode is reduced. This can be equivalent to the case where lithium is used as a reference electrode.

  The charging method described above is a method for charging a positive electrode. However, in the case of charging a battery composed of a positive electrode and a negative electrode, the charge termination voltage is changed depending on the type of the negative electrode, and charging is performed when lithium to the positive electrode is used as a reference electrode. A similar effect can be obtained by defining a charging method for setting the end voltage to a predetermined voltage and setting the state of charge of the positive electrode at the charging end to a predetermined state.

  If the charging rate (rate) is too high, the battery reaches the charge end voltage before the positive electrode and the negative electrode are sufficiently charged, so that a sufficient capacity cannot be obtained. For this reason, when charging with a constant current, it is preferable to charge at a charging rate of 1C or less (1C is a current value for discharging a rated capacity with a discharge capacity of 1 hour in 1 hour) or less. However, if the charging speed is excessively slow, it takes a long time for charging. Therefore, in the case of constant current charging, it is preferably 0.01C or more. It is also possible to charge the battery while maintaining a constant voltage after reaching the end-of-charge voltage.

  At the time of charging, if the battery temperature is excessively high, the non-aqueous electrolyte is likely to be decomposed. If the temperature is low, charging to the positive electrode and the negative electrode is likely to be insufficient. .

  The non-aqueous electrolyte secondary battery of the present invention obtained by charging in this way varies depending on the discharge rate and the negative electrode used, but usually a value of about 2 to 3 V at a discharge rate of 1 C or less from the charged state. Is used as the end-of-discharge voltage to obtain a nearly rated discharge capacity. For example, when lithium is used as a reference electrode and the end-of-charge voltage of the positive electrode is 4.9 V, the discharge capacity per positive electrode active material is 25 mAh / It is possible to obtain a high discharge capacity of g or more, particularly about 30 to 70 mAh / g.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.

  Hereinafter, the charge end voltage of the positive electrode using lithium as a reference electrode is referred to as “charge end voltage (vs. Li)”.

Example 1
As the positive electrode active material, commercially available graphite powder A having the following physical properties was used. In the powder X-ray diffraction pattern using CuKα ray of the graphite powder, the diffraction intensity _{I 2 [Theta] = 22.3} at 2 [Theta] = 22.3 °, a diffraction of the diffraction intensity _{I 2 [Theta] = 26.4} at 2 [Theta] = 26.4 ° The intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} was 0.02. The value of the surface separation d (002) was 3.3342 angstrom. In Raman spectrum analysis using argon laser beam, the peak intensity ratio _I A / _{I B} was 0.14. Further, according to the catalog value, the BET specific surface area measured by nitrogen adsorption was 20 m ² / g, and the median diameter measured by a laser diffraction particle size distribution meter was 3.4 μm.

  A mixture of 70 parts by weight of the graphite powder and 30 parts by weight of a conductive material composed of 95% by weight of acetylene black and 5% by weight of polytetrafluoroethylene with ethanol added thereto was pressure-bonded to a stainless steel mesh to form a positive electrode. The mixture pressed on the stainless steel mesh was 20 mg, and the graphite powder was 14 mg. This was dried at 200 ° C. for 4 hours before assembling the battery.

Metallic lithium as the negative electrode, EC (ethylene carbonate): DMC (dimethyl carbonate) = 1: 1 (volume ratio) mixed solution of LiPF ₆ in a 1 mol / L mixed solvent, and a polypropylene porous sheet as the negative electrode As a separator, a semi-open cell type battery was produced in an argon dry box.

  At room temperature, the battery was charged with a constant current of 1 mA (about 0.6 C) to a charge end voltage (vs. Li) of 4.9 V, and then discharged to 3.5 V with a constant current of 1 mA. The discharge capacity per substance (hereinafter referred to as “reversible capacity”) was 40 mAh / g.

Example 2
In Example 1, a semi-open cell was prepared in the same manner except that the commercially available graphite powder B having the following physical properties was used as the positive electrode active material, and charge / discharge was performed similarly. As a result, the reversible capacity was 35 mAh / g. It was.

The graphite powder had a diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of 0.08. The value of the surface separation d (002) was 3.373 angstroms. According to the catalog values, the BET specific surface area measured by nitrogen adsorption was 90 m ² / g, and the median diameter measured by a laser diffraction particle size distribution meter was 13.2 μm.

Example 3
In Example 1, a semi-open cell was prepared in the same manner except that the commercially available graphite powder C having the following physical properties was used as the positive electrode active material, and charge / discharge was performed in the same manner. As a result, the reversible capacity was 28 mAh / g. It was.

The diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of this graphite powder was 0.10. The value of the surface separation d (002) was 3.380 angstroms.

Comparative Example 1
In Example 1, a semi-open cell was prepared in the same manner except that a commercially available vapor-grown carbon fiber D having the following physical properties was used as the positive electrode active material, and charge / discharge was performed similarly. As a result, the reversible capacity was 18 mAh / g.

The diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of this vapor grown carbon fiber was 0.19. The value of the surface separation d (002) was 3.380 angstroms. According to the catalog value, this vapor grown carbon fiber had a fiber diameter of 150 nm, a fiber length of 10 to 20 μm, and a specific surface area of 13 m ² / g.

Comparative Example 2
In Example 1, a semi-open cell was prepared in the same manner except that the commercially available carbon black E having the following physical properties was used as the positive electrode active material. As a result of the same charge and discharge, the reversible capacity was 7 mAh / g. It was.

The carbon black had a diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of 0.64.

Example 5
The graphite powder used in Example 1 was heat-treated at 500 ° C. for 3 hours in an oxygen atmosphere. The resulting graphite powder had a diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of 0.01. In addition, the value of the interplanar spacing d (002) was 3.348 angstroms. A semi-open cell was prepared in the same manner as in Example 1 except that this graphite powder was used as the positive electrode active material, and charge / discharge was performed in the same manner. As a result, the reversible capacity was 67 mAh / g.

From the results of the above examples and comparative examples, a carbon material having a diffraction intensity ratio I _{2θ = 22.3} / I _{2θ = 26.4} of 0.15 or less is used as the positive electrode active material, whereby a high-capacity non-aqueous electrolyte solution is used. It can be seen that a secondary battery can be obtained.

  The application of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, etc.

Claims (4)

A non-aqueous electrolyte comprising at least a positive electrode in which anions are mainly inserted / desorbed, a negative electrode capable of inserting and extracting metallic lithium or lithium ions, and a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent In the carbon material for the positive electrode active material used for the secondary battery,
X-ray diffraction intensity ratio by CuKα ray I _{2θ = 22.3} / I _{2θ = 26.4} (where I _{2θ = 22.3} and I _{2θ = 26.4} are 2θ = 22.3 °, 2θ = The carbon material for a positive electrode active material of a non-aqueous electrolyte secondary battery, wherein the diffraction intensity at 26.4 ° is 0.15 or less.   2. The carbon material for a positive electrode active material of a non-aqueous electrolyte secondary battery according to claim 1, wherein an inter-surface distance d (002) of the 002 surface is 3.34 angstroms or more and 3.38 angstroms or less.   A non-aqueous electrolyte comprising at least a positive electrode in which anions are mainly inserted / desorbed, a negative electrode capable of inserting and extracting metallic lithium or lithium ions, and a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent A positive electrode of a secondary battery, comprising the carbon material for a positive electrode active material according to claim 1 or 2, wherein the positive electrode is a non-aqueous electrolyte secondary battery positive electrode.   A non-aqueous electrolyte comprising at least a positive electrode in which anions are mainly inserted / desorbed, a negative electrode capable of inserting and extracting metallic lithium or lithium ions, and a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent A non-aqueous electrolyte secondary battery comprising the positive electrode according to claim 3 in a secondary battery.