WO2013176067A1 - Positive electrode active material for non-aqueous secondary batteries - Google Patents

Positive electrode active material for non-aqueous secondary batteries Download PDF

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WO2013176067A1
WO2013176067A1 PCT/JP2013/063883 JP2013063883W WO2013176067A1 WO 2013176067 A1 WO2013176067 A1 WO 2013176067A1 JP 2013063883 W JP2013063883 W JP 2013063883W WO 2013176067 A1 WO2013176067 A1 WO 2013176067A1
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Prior art keywords
positive electrode
electrode active
active material
carbon
aqueous secondary
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PCT/JP2013/063883
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French (fr)
Japanese (ja)
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崇 中林
心 ▲高▲橋
寛 北川
将成 織田
豊隆 湯浅
秀一 高野
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株式会社 日立製作所
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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 positive electrode active material for a non-aqueous secondary battery, a manufacturing method thereof, and a positive electrode for a non-aqueous secondary battery and a non-aqueous secondary battery using the positive electrode active material.
  • Lithium ion secondary batteries have a higher energy density than nickel metal hydride batteries and the like, and are used, for example, as power sources for portable electronic devices.
  • application to medium and large-sized applications such as hybrid vehicles, electric vehicles, stationary uninterruptible power supplies, and power leveling has been promoted.
  • the lithium ion secondary battery has a heat generation and ignition accident, and it is necessary to improve safety.
  • a layered oxide positive electrode active material such as LiCoO 2 is used as the positive electrode active material.
  • Li lithium
  • the layered oxide-based positive electrode active material lithium (Li) atoms themselves support the crystal structure, and the structure becomes unstable when Li atoms are desorbed by charging.
  • Li atoms supporting the Li layer are excessively desorbed due to overcharge, the structure collapses and oxygen is released, which may lead to heat generation and ignition.
  • an olivine-based positive electrode active material represented by LiMPO 4 (M is a metal) having an olivine structure that is excellent in safety. Since the olivine-based positive electrode active material has an olivine structure, the structure is stable even when Li atoms are desorbed by charging, and since oxygen and phosphorus are covalently bonded, oxygen is hardly released and safety is high.
  • olivine-based positive electrode active materials include olivine iron-based positive electrode active materials having iron as a constituent element, olivine manganese-based positive electrode active materials having manganese as a constituent element, and the like.
  • the reaction potential is as low as 3.4 V (vs. Li / Li + ), so the energy density is low, and the conductivity and Li ion diffusibility are low.
  • the olivine manganese-based positive electrode active material has attracted attention because of its high reaction potential of 4.1 V (vs. Li / Li + ) and high energy density.
  • the olivine manganese-based positive electrode active material has lower conductivity and Li ion diffusibility than the olivine iron-based positive electrode active material, and therefore has a low capacity.
  • Patent Document 1 a method for increasing the specific surface area and increasing the capacity of the olivine manganese-based positive electrode active material has been proposed in (Patent Document 1) and the like in order to improve the reactivity with the electrolytic solution.
  • Patent Document 2 and the like have proposed a method of increasing the capacity by coating the surface of the olivine-based positive electrode active material with a carbon material, increasing the crystallinity of the carbon layer, and improving the conductivity.
  • Non-patent document 1 when the positive electrode active material is stored at a high temperature (55 ° C.), manganese (Mn) is eluted, and as a result, capacity reduction occurs when charging / discharging at a high temperature (55 ° C.). Has been reported. And (Non-Patent Document 1) reports that by increasing the amount of acetylene black which is a carbon coating source, the elution amount of Mn is suppressed and the decrease in capacity due to charging and discharging during high temperature is suppressed.
  • Patent Document 3 when the olivine iron-based positive electrode active material absorbs water, the metal is easily eluted into the electrolytic solution, and Fe, Mn, etc. eluted into the electrolytic solution are deposited on the negative electrode, and the output resistance is reduced. There is a problem that the life performance is deteriorated due to a significant increase or a decrease in discharge capacity.
  • the zeolite is accommodated in the battery case to remove moisture, and the specific surface area of the positive electrode active material is increased to 5%.
  • a method has been proposed in which the amount of moisture brought in is reduced and the elution of Fe, Mn, and the like is suppressed by setting it to ⁇ 13 m 2 / g.
  • Non-patent Document 1 has a problem that the amount of acetylene black used for carbon coating is excessively 30% by weight and the electrode capacity is lowered. Further, (Non-Patent Document 1) has no description regarding the specific surface area. Furthermore, (Patent Document 3) is an invention related to an olivine iron-based positive electrode active material having higher conductivity and Li ion diffusibility than the olivine manganese-based positive electrode active material, and the properties required for specific surface area and the like are different. Further, since zeolite is stored in the battery case, the space for storing the positive electrode is narrowed, and the battery capacity is reduced. Furthermore, there is no description regarding the crystallinity of the carbon coating layer.
  • the present invention has been made in view of the above points, and is fired at a low temperature in order to obtain a small particle size, and even when the crystallinity of the carbon coating is low, there is little Mn elution during high-temperature storage and high-temperature storage characteristics.
  • An object of the present invention is to provide a positive electrode active material for a non-aqueous secondary battery.
  • the positive electrode active material for a non-aqueous secondary battery according to the present invention has a chemical formula Li A Mn X M 1-X (PO 4 ) B (where 0.8 ⁇ A ⁇ 1.2, 0 8 ⁇ B ⁇ 1.2, 0.3 ⁇ X ⁇ 1, and M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr)
  • the lithium composite oxide having a olivine type structure is covered, and a part or the whole of the surface of the lithium composite oxide is coated with a carbon material, and the area ratio of the carbon D band and the carbon G band by Raman measurement ( SD / S G ) is 3.5 or more, the specific surface area S is 13 m 2 / g ⁇ S ⁇ 40 m 2 / g, and the crystallite diameter D is determined from the particle diameter d and the half width obtained by X-ray diffraction.
  • the ratio (d / D) is 1 or more and 1.
  • the positive electrode active material for a non-aqueous secondary battery of the present invention even if the area ratio of the carbon D band and the carbon G band by Raman measurement is 3.5 or more and low crystallinity, Side reactions with certain lithium composite oxides can be suppressed, the amount of Mn elution is small, and high temperature storage characteristics are good. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.
  • FIG. 2 is a scanning electron micrograph of a positive electrode active material in Example 2.
  • FIG. It is a figure which shows the Raman measurement result of the positive electrode active material in Example 2.
  • 2 is a scanning electron micrograph of a positive electrode active material in Comparative Example 1.
  • 4 is a scanning electron micrograph of a positive electrode active material in Comparative Example 2. It is a fragmentary sectional view of one embodiment of the non-aqueous secondary battery of the present invention.
  • the positive electrode active material for a non-aqueous secondary battery of the present invention has a chemical formula Li A Mn X M 1-X (PO 4 ) B (where 0.8 ⁇ A ⁇ 1.2, 0.8 ⁇ B ⁇ 1. 2, 0.3 ⁇ X ⁇ 1, wherein M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr) Includes complex oxides.
  • M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr
  • M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr
  • M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr
  • M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr
  • M is one or more metal
  • Li and P are 80 mol% or more and 120 mol% or less with respect to Mn and other metal atoms. If Li is in the above range, the lithium composite oxide can have an olivine structure. In particular, Li and P are preferably 100 mol% or more and 120 mol% or less with respect to Mn and other metal atoms. When Li and P are within the above ranges, generation of metal as a by-product can be prevented. Therefore, precipitation of the metal foreign material in a negative electrode can be prevented, a short circuit can be prevented and safety can be improved.
  • the positive electrode active material has a ratio (d / D) of a particle diameter (denoted as d) to a crystallite diameter (denoted as D) obtained from a half width obtained by X-ray diffraction is 1 or more and 1.35 or less. is there.
  • d / D is 1.35 or less
  • the crystallinity of the core material Li A Mn X M 1-X PO 4 is good, and since there are few defects, the diffusibility of Li ions increases, resulting in high capacity. It is done.
  • the crystallite diameter D does not become larger than the particle diameter d and coincides with the particle diameter d when the crystallite diameter D is maximum, so the minimum value of d / D is 1. Therefore, the closer d / D is to 1, the better the crystallinity.
  • the particle diameter d is the result of observing a randomly extracted positive electrode active material using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and observing three or more randomly selected fields.
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • the average particle diameter is an average value obtained from all the particle diameters extracted from the order of 40 particle diameters in each visual field extracted from the order in which the particle diameters are close to the median value.
  • the crystallite diameter D is a physical property value obtained from the half width in the X-ray diffraction (XRD) measurement result.
  • the XRD measurement is performed by the concentration method, the X-ray is CuK ⁇ ray, and the output is 40 kV and 40 mA. Measurement was performed under the condition that the step width was 0.03 °, and the measurement time per step was 15 seconds. The measurement data was smoothed by the Savitzky-Goley method, and then the background and K ⁇ 2 line were removed. ) Find the full width at half maximum ⁇ exp of the peak (space group is Pmna). Further, a standard Si sample (NIST standard sample 640d) was measured under the same apparatus and under the same conditions, and a half width ⁇ i of the peak was obtained.
  • ⁇ is the wavelength of the X-ray source
  • ⁇ is the reflection angle
  • K is a Scherrer constant
  • K 0.9.
  • the positive electrode active material of the present invention a part or the whole of the surface of the lithium composite oxide is coated with a carbon material, and the area of the carbon D band (S D ) and the area of the carbon G band (S G ) by Raman measurement.
  • the area ratio (S D / S G ) is 3.5 or more.
  • the carbon material becomes low crystalline, and the area ratio (S D / S G ) is 3.5 or more.
  • the coating with the carbon material does not necessarily have to be a carbon material, and a part thereof may be a material other than the carbon material.
  • the carbon content of the positive electrode active material is preferably 0.5% by weight or more and less than 30% by weight.
  • the carbon content is more preferably 1% by weight or more.
  • conductivity is improved and rate characteristics are improved.
  • the carbon content is more than 30% by weight, the battery capacity decreases.
  • the carbon content is more preferably 5% by weight or less. When the carbon content is 5% by weight or less, the decrease in electrode capacity can be more effectively suppressed.
  • the specific surface area S of the positive electrode active material is 13 m 2 / g ⁇ S ⁇ 40 m 2 / g.
  • the specific surface area S is larger than 13 m 2 / g, the reaction field between the positive electrode active material and the electrolyte is widened, the resistance is lowered, and the capacity is increased.
  • the specific surface area S is 40 m 2 / g or less, side reaction between hydrogen fluoride in the electrolyte and Li A Mn X M 1-X (PO 4 ) B as a core material can be suppressed, and Mn and Elution of metal and generation of a resistance layer can be suppressed, and high-temperature storage characteristics are improved.
  • the particle size of the positive electrode active material is preferably 10 nm or more and 500 nm or less.
  • the particle diameter d is less than 10 nm, the bulk density is high and the capacity per volume is reduced.
  • the particle diameter d exceeds 500 nm, the Li ion diffusion path becomes longer, resulting in higher resistance and lower capacity.
  • the particle diameter d is more preferably 30 nm or more and 50 nm or less.
  • a capacity of 30 nm or more and 50 nm or less results in a high capacity and good high-temperature storage characteristics.
  • the positive electrode active material may be made into secondary particles by granulation or the like.
  • the positive electrode active material for a non-aqueous secondary battery as described above includes a step of mixing raw materials of a lithium composite oxide, a step of pre-baking the mixed raw materials, and a carbon source mixed with a pre-fired body obtained by pre-baking And a method including a step of subjecting the mixed calcined body and the carbon source to main firing.
  • the firing temperature in the main firing step is preferably not less than the crystallization temperature of the lithium composite oxide and not more than a temperature obtained by adding 400 ° C. to the crystallization temperature.
  • the carbon source to be mixed with the calcined product can be appropriately selected from sucrose, lactose, maltose, trehalose, turanose, cellobiose, glucose, glycogen, starch, cellulose, dextrin and other sugars, pitch-based carbon materials, and the like.
  • the amount to be mixed can be determined in consideration of the above-described carbon content.
  • a positive electrode for a non-aqueous secondary battery having a high capacity and good high-temperature storage characteristics can be produced.
  • the positive electrode can be produced by a conventionally known method. Specifically, for example, the above positive electrode active material, a conductive material and a binder are kneaded, and a dispersion solvent such as N-methylpyrrolidone is added. A positive electrode mixture slurry is prepared by appropriately diluting. The positive electrode mixture slurry is applied to the surface of an aluminum foil or the like used as a positive electrode current collector, and then dried and pressed with a pressure roller to form a positive electrode mixture layer on the current collector to form a positive electrode. Make it.
  • the binder is not particularly limited, but polyvinylidene fluoride, polyacrylonitrile, styrene-butadiene rubber and the like are applicable.
  • the conductive material for example, carbon materials such as graphite, acetylene black, carbon black, carbon fiber, and metal carbide can be applied, and each can be used alone or in admixture of two or more.
  • Non-aqueous secondary battery By using the positive electrode, a non-aqueous secondary battery having a high capacity and good high-temperature storage characteristics can be obtained.
  • a configuration of the non-aqueous secondary battery a conventionally known general configuration can be adopted.
  • FIG. 5 shows a partial cross-sectional view of an embodiment of a non-aqueous secondary battery according to the present invention.
  • a separator 7 is disposed between the positive electrode 5 and the negative electrode 6.
  • the positive electrode 5, the negative electrode 6 and the separator 7 are wound and sealed together with a non-aqueous electrolyte (not shown) in a battery can 10 made of stainless steel or aluminum.
  • the positive electrode 5 is provided with a positive electrode lead 8, and the negative electrode 6 is provided with a negative electrode lead 9, each configured to extract current.
  • Insulating plates 12 are respectively provided between the positive electrode 5 and the negative electrode lead 9 and between the negative electrode 6 and the positive electrode lead 8. Further, between the battery can 10 in contact with the negative electrode lead 9 and the sealing lid portion 13 in contact with the positive electrode lead 8, a packing for separating the positive electrode and the negative electrode as well as preventing leakage of the electrolyte. 11 is provided.
  • LiPF 6 is contained in the electrolytic solution.
  • the positive electrode active material for a non-aqueous secondary battery of the present invention high temperature storage characteristics are improved even when LiPF 6 is contained in the electrolytic solution, and good output characteristics resulting from LiPF 6 can be obtained. That is, it is possible to obtain a secondary battery having a high capacity, good high-temperature storage characteristics, and good output characteristics.
  • its content is preferably 0.01 to 5 mol% in the electrolytic solution.
  • Example 1 Iron citrate (FeC 6 H 5 O 7 .nH 2 O) and citric acid monohydrate (C 6 H 8 O 7 .H 2 O) were dissolved in pure water. To the obtained solution, a solution in which manganese acetate tetrahydrate (Mn (CH 3 COO) 2 .4H 2 O) was dissolved in pure water was added. Further, lithium dihydrogen phosphate and an aqueous lithium acetate solution were added to the pure water. The dissolved solution was added. The obtained solution was dried using a spray dryer to obtain a raw material powder. This raw material powder was temporarily fired at 440 ° C. for 10 hours to obtain a temporarily fired body.
  • Mn (CH 3 COO) 2 .4H 2 O manganese acetate tetrahydrate
  • lithium dihydrogen phosphate and an aqueous lithium acetate solution were added to the pure water. The dissolved solution was added.
  • the obtained solution was dried using a spray dryer to obtain a raw material powder. This
  • the obtained positive electrode active material was measured by X-ray diffraction.
  • the core material was a lithium composite oxide having an olivine structure represented by the chemical formula LiMnFePO 4. When the Raman measurement was performed, the surface was coated with a carbon material. It was.
  • the carbon content of the positive electrode active material was 2.0% by weight.
  • the specific surface area of the positive electrode active material was 15.0 m 2 / g as measured using a catalyst analyzer BEL-CAT (manufactured by Nippon Bell Co., Ltd.).
  • the carbon coating amount per surface area was 1.3 mg / m 2 .
  • the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4.
  • the particle diameter d of the positive electrode active material is 45 nm
  • the crystallite diameter D is 38 nm
  • the ratio of the particle diameter d to the crystallite diameter D (d / G) was 1.2.
  • Example 2 A positive electrode active material was prepared in the same manner as in Example 1 except that 7 parts by weight of sucrose was used.
  • FIG. 1 shows an SEM image of the positive electrode active material 1.
  • the obtained positive electrode active material was subjected to elemental analysis by high frequency inductively coupled plasma optical emission spectrometry (ICP-AES). As a result, the Mn content was 27% by weight and the Fe content was 6.5% by weight.
  • the carbon content was 2.0% by weight.
  • the particle diameter d was 39 nm
  • the crystallite diameter D was 32 nm
  • d / D was 1.2.
  • the specific surface area was 23.1 m 2 / g as measured using a catalyst analyzer BEL-CAT (manufactured by Nippon Bell Co., Ltd.).
  • the carbon coating amount per surface area was 0.9 mg / m 2 .
  • the Raman measurement result of a positive electrode active material is shown.
  • the area ratio (S D / S G ) of the carbon D band 3 and the carbon G band 2 by Raman measurement was 4.4.
  • Example 3 A positive electrode active material was produced in the same manner as in Example 1 except that 10 parts by weight of sucrose was used. The carbon content was 2.0% by weight. The specific surface area of the positive electrode active material was 36.1 m 2 / g. The carbon coating amount per surface area was 0.9 mg / m 2 . Further, the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4. Furthermore, the particle diameter d of the positive electrode active material was 35 nm, the crystallite diameter D determined from the half width obtained by X-ray diffraction was 30 nm, and d / D was 1.2.
  • FIG. 3 shows an SEM image of the positive electrode active material 1.
  • the carbon content was 1.9% by weight.
  • the specific surface area was 6.2 m 2 / g.
  • the carbon coating amount per surface area was 3.0 mg / m 2 .
  • the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4.
  • FIG. 4 shows an SEM image of the positive electrode active material 1.
  • the carbon content was 3.8% by weight.
  • the specific surface area was 41.9 m 2 / g.
  • the carbon coating amount per surface area was 0.9 mg / m 2 .
  • the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4.
  • Example 3 A positive electrode active material was produced in the same manner as in Example 1 except that the atmosphere during the pre-baking was argon and sucrose was not added after the pre-baking.
  • the obtained positive electrode active material had a particle diameter d of 35 nm, a crystallite diameter D of 22 nm, and d / D of 1.6.
  • the carbon content was 6.3% by weight.
  • Example 4 A positive electrode active material was produced in the same manner as in Example 2 except that the main firing temperature was 900 ° C.
  • the particle diameter d of the obtained positive electrode active material was 150 nm.
  • the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 3.1.
  • a positive electrode fabrication method 82.5 parts by weight of the positive electrode active material prepared in Examples 1 to 3 and Comparative Examples 1 to 4, 10 parts by weight of acetylene black (Denka Black (registered trademark) manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and binder A mixture of 7.5 parts by weight of modified polyacrylonitrile dissolved in N-methylpyrrolidone was kneaded to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry was uniformly coated on an aluminum foil using a coating machine. After drying at 80 ° C. in the air, a positive electrode was obtained by punching and pressing to ⁇ 15 mm.
  • acetylene black Denki Kagaku Kogyo Co., Ltd.
  • Electrode characteristics were evaluated for each positive electrode produced as described above.
  • the electrolytic solution vinylene carbonate was added to a mixed solvent of ethylene carbonate and ethyl methyl carbonate, and 1M LiPF 6 was added thereto. Moreover, lithium metal was used for the negative electrode.
  • Mn elution evaluation and maintenance rate evaluation With respect to the positive electrodes using the positive electrode active materials of Examples 1 to 3, Comparative Example 1 and Comparative Example 2, the Mn elution amount was evaluated. First, charge / discharge is performed for 3 cycles under the same conditions as in the charge / discharge test. Next, after washing the positive electrode with dimethyl carbonate, it is immersed in 5 ml of an electrolytic solution. And it preserve
  • the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement of the positive electrode active material is 4.4, and the specific surface area of the positive electrode active material is larger than 13 m 2 / g as shown in Table 1.
  • the initial discharge capacity is as high as 131 Ah / kg or more
  • the Mn elution amount after high-temperature storage is as small as 2.2% or less
  • the discharge capacity maintenance rate is also 97 Since it is as high as% or more, high capacity and high temperature storage characteristics are good.
  • Comparative Example 1 in which the positive electrode active material has a specific surface area of 13 m 2 / g or less has an initial discharge capacity as low as 110 Ah / kg. Further, in Comparative Example 2 having a specific surface area larger than 40 m 2 / g, the elution amount of Mn is as high as 4.9%, the discharge capacity retention rate after high-temperature storage is as low as 89%, and high-temperature storage characteristics are poor. I understood. Further, since d / D is 1.6, Comparative Example 3 in which the core material has low crystallinity has an initial discharge capacity as low as 110 Ah / kg. Further, in Comparative Example 4 in which the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement is 3.1, the particle diameter is enlarged and the initial discharge capacity is as low as 121 Ah / kg.
  • the positive electrode active material of the present invention has a high capacity and good high-temperature storage characteristics.
  • the positive electrode for a non-aqueous secondary battery of the present invention is expected to be applied to a mobile body and a stationary power storage power source that require a large-capacity large-sized lithium ion secondary battery.

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Abstract

The purpose of the present invention is to provide a positive electrode active material for non-aqueous secondary batteries that is baked at a low temperature in order to achieve a small particle diameter and has little Mn elution during high temperature storage and good high-temperature storage properties, even if the carbon coating crystallinity is low. This positive electrode active material for non-aqueous secondary batteries is characterized by: including a lithium complex oxide having an olivine-type structure indicated by chemical formula LiAMnXM1-x(PO4)B (in formula, 0.8≤A≤1.2, 0.8≤B≤1.2, 0.3≤X<1, and M is at least one type of metal atom selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr); all or part of the surface of the lithium complex oxide being coated by a carbon material; the area ratio (SD/SG) between a carbon D band (3) and a carbon G band (2) found using Raman measurement being at least 3.5; the specific surface area (S) being 13 m2/g<S≤40 m2/g; and the ratio (d/D) between particle diameter (d) and the crystallite diameter (D) found from the half width obtained by using X-ray diffraction being 1-1.35.

Description

非水系二次電池用正極活物質Cathode active material for non-aqueous secondary batteries
　本発明は、非水系二次電池用正極活物質及びその製造方法、並びにその正極活物質を用いた非水系二次電池用正極及び非水系二次電池に関する。 The present invention relates to a positive electrode active material for a non-aqueous secondary battery, a manufacturing method thereof, and a positive electrode for a non-aqueous secondary battery and a non-aqueous secondary battery using the positive electrode active material.
　非水系二次電池として、非水系電解液を用い、リチウムイオンを充放電反応に用いるリチウムイオン二次電池が実用化されている。リチウムイオン二次電池は、ニッケル水素電池等と比べてエネルギー密度が大きく、例えば、携帯電子機器の電源として用いられている。近年では、さらに、ハイブリット自動車、電気自動車、定置無停電電源、電力平準化用途等、中・大型用途への適用が進められている。一方、リチウムイオン二次電池の発熱・発火事故が起きており、安全性の向上が必要である。 As a non-aqueous secondary battery, a lithium ion secondary battery using a non-aqueous electrolyte and using lithium ions for a charge / discharge reaction has been put into practical use. Lithium ion secondary batteries have a higher energy density than nickel metal hydride batteries and the like, and are used, for example, as power sources for portable electronic devices. In recent years, application to medium and large-sized applications such as hybrid vehicles, electric vehicles, stationary uninterruptible power supplies, and power leveling has been promoted. On the other hand, the lithium ion secondary battery has a heat generation and ignition accident, and it is necessary to improve safety.
　現在、正極活物質には、ＬｉＣｏＯ2等の層状酸化物系正極活物質が用いられている。層状酸化物系正極活物質は、リチウム（Ｌｉ）原子自体が結晶構造を支えており、充電によりＬｉ原子が脱離すると構造が不安定となる。また、過充電となりＬｉ層を支えるＬｉ原子が過剰に脱離すると、構造が崩壊して酸素を放出し、発熱・発火に至る恐れがある。 Currently, a layered oxide positive electrode active material such as LiCoO 2 is used as the positive electrode active material. In the layered oxide-based positive electrode active material, lithium (Li) atoms themselves support the crystal structure, and the structure becomes unstable when Li atoms are desorbed by charging. Moreover, when Li atoms supporting the Li layer are excessively desorbed due to overcharge, the structure collapses and oxygen is released, which may lead to heat generation and ignition.
　そこで、安全性に優れるオリビン構造を有するＬｉＭＰＯ4（Ｍは金属）で表されるオリビン系正極活物質に高い関心が寄せられている。オリビン系正極活物質は、オリビン構造であるため、充電によりＬｉ原子が脱離しても構造が安定であり、且つ、酸素とリンが共有結合しているため酸素が放出され難く安全性が高い。 Therefore, there is a great interest in an olivine-based positive electrode active material represented by LiMPO 4 (M is a metal) having an olivine structure that is excellent in safety. Since the olivine-based positive electrode active material has an olivine structure, the structure is stable even when Li atoms are desorbed by charging, and since oxygen and phosphorus are covalently bonded, oxygen is hardly released and safety is high.
　オリビン系正極活物質には、鉄を構成元素とするオリビン鉄系正極活物質や、マンガンを構成元素とするオリビンマンガン系正極活物質等が知られている。オリビン鉄系正極活物質は実用化されているが、反応電位が３．４Ｖ（ｖｓ．Ｌｉ／Ｌｉ+）と低いためエネルギー密度が低く、導電性・Ｌｉイオン拡散性は低い。一方、オリビンマンガン系正極活物質は、反応電位が４．１Ｖ（ｖｓ．Ｌｉ／Ｌｉ+）と高く、エネルギー密度が高いため注目を集めている。しかし、オリビンマンガン系正極活物質は、オリビン鉄系正極活物質と比較しても導電性・Ｌｉイオン拡散性が低く、そのため低容量となる。 Known olivine-based positive electrode active materials include olivine iron-based positive electrode active materials having iron as a constituent element, olivine manganese-based positive electrode active materials having manganese as a constituent element, and the like. Although the olivine iron-based positive electrode active material has been put into practical use, the reaction potential is as low as 3.4 V (vs. Li / Li + ), so the energy density is low, and the conductivity and Li ion diffusibility are low. On the other hand, the olivine manganese-based positive electrode active material has attracted attention because of its high reaction potential of 4.1 V (vs. Li / Li + ) and high energy density. However, the olivine manganese-based positive electrode active material has lower conductivity and Li ion diffusibility than the olivine iron-based positive electrode active material, and therefore has a low capacity.
　そこで、（特許文献１）等に、電解液との反応性を向上させるためオリビンマンガン系正極活物質の比表面積を大きくし容量を高くする方法が提案されている。 Therefore, a method for increasing the specific surface area and increasing the capacity of the olivine manganese-based positive electrode active material has been proposed in (Patent Document 1) and the like in order to improve the reactivity with the electrolytic solution.
　また、（特許文献２）等には、オリビン系正極活物質の表面を炭素材料で被覆し、炭素層の結晶性を高くし導電性を改善することで高容量とする方法が提案されている。 In addition, (Patent Document 2) and the like have proposed a method of increasing the capacity by coating the surface of the olivine-based positive electrode active material with a carbon material, increasing the crystallinity of the carbon layer, and improving the conductivity. .
　ところで、（非特許文献１）には、正極活物質を高温（５５℃）で保存するとマンガン（Ｍｎ）が溶出し、その結果、高温（５５℃）で充放電を行うと容量低下が起きることが報告されている。そして（非特許文献１）には、炭素被覆源であるアセチレンブラックの量を増やすことで、Ｍｎの溶出量が抑制され高温中充放電による容量低下が抑制されることが報告されている。 By the way, in (Non-patent document 1), when the positive electrode active material is stored at a high temperature (55 ° C.), manganese (Mn) is eluted, and as a result, capacity reduction occurs when charging / discharging at a high temperature (55 ° C.). Has been reported. And (Non-Patent Document 1) reports that by increasing the amount of acetylene black which is a carbon coating source, the elution amount of Mn is suppressed and the decrease in capacity due to charging and discharging during high temperature is suppressed.
　また、（特許文献３）には、オリビン鉄系正極活物質が水を吸収すると、電解液に金属が溶出し易くなり、電解液に溶出したＦｅやＭｎ等が負極に析出し、出力抵抗が大幅に増加したり、放電容量が大幅に低下して寿命性能が低下するという問題があり、これに対し、ゼオライトを電池ケース内に収容して水分を除去し、正極活物質の比表面積を５～１３ｍ2／ｇとすることで水分持ち込み量を低減しＦｅやＭｎ等の溶出を抑制する方法が提案されている。 Also, in Patent Document 3, when the olivine iron-based positive electrode active material absorbs water, the metal is easily eluted into the electrolytic solution, and Fe, Mn, etc. eluted into the electrolytic solution are deposited on the negative electrode, and the output resistance is reduced. There is a problem that the life performance is deteriorated due to a significant increase or a decrease in discharge capacity. On the other hand, the zeolite is accommodated in the battery case to remove moisture, and the specific surface area of the positive electrode active material is increased to 5%. A method has been proposed in which the amount of moisture brought in is reduced and the elution of Fe, Mn, and the like is suppressed by setting it to ˜13 m 2 / g.
特開２０１０－２８７４５０号公報JP 2010-287450 A 特開２００６－３０２６７１号公報JP 2006-302671 A 特開２０１０－１６５５０７号公報JP 2010-165507 A
　しかしながら、高容量を得るため比表面積を大きくするには、粒成長を抑制するために低温での焼成が必要となり、低結晶性の炭素被覆となってＭｎが溶出し易くなる。 However, in order to increase the specific surface area in order to obtain a high capacity, it is necessary to perform firing at a low temperature in order to suppress grain growth, and Mn tends to elute due to a low crystalline carbon coating.
　また、（非特許文献１）の方法では、炭素被覆に用いるアセチレンブラック量が３０重量％と過多であり、電極容量が低くなる問題がある。また、（非特許文献１）に比表面積に関する記載はない。さらに、（特許文献３）は、オリビンマンガン系正極活物質より導電性・Ｌｉイオン拡散性が高いオリビン鉄系正極活物質に関する発明であり、比表面積等について求められる性質が異なる。また、ゼオライトを電池ケース内に収納するため、正極を収納するスペースが狭くなり電池容量が低下する。さらに、炭素被覆層の結晶性に関する記載がない。 Also, the method of (Non-patent Document 1) has a problem that the amount of acetylene black used for carbon coating is excessively 30% by weight and the electrode capacity is lowered. Further, (Non-Patent Document 1) has no description regarding the specific surface area. Furthermore, (Patent Document 3) is an invention related to an olivine iron-based positive electrode active material having higher conductivity and Li ion diffusibility than the olivine manganese-based positive electrode active material, and the properties required for specific surface area and the like are different. Further, since zeolite is stored in the battery case, the space for storing the positive electrode is narrowed, and the battery capacity is reduced. Furthermore, there is no description regarding the crystallinity of the carbon coating layer.
　そこで本発明は、上記の点に鑑みてなされたものであり、小粒子径とするために低温で焼成し、炭素被覆の結晶性が低くても、高温保存時のＭｎ溶出が少なく高温保存特性が良好な非水系二次電池用正極活物質を提供することを目的とする。 Accordingly, the present invention has been made in view of the above points, and is fired at a low temperature in order to obtain a small particle size, and even when the crystallinity of the carbon coating is low, there is little Mn elution during high-temperature storage and high-temperature storage characteristics. An object of the present invention is to provide a positive electrode active material for a non-aqueous secondary battery.
　上記課題を解決するため、本発明の非水系二次電池用正極活物質は、化学式ＬｉAＭｎXＭ1-X（ＰＯ4）B（式中、０．８≦Ａ≦１．２、０．８≦Ｂ≦１．２、０．３≦Ｘ＜１、ＭはＬｉ、Ｆｅ、Ｎｉ、Ｃｏ、Ｔｉ、Ｃｕ、Ｚｎ、Ｍｇ、及びＺｒから選ばれる一種以上の金属原子である）で表わされるオリビン型構造を有するリチウム複合酸化物を含み、前記リチウム複合酸化物の表面の一部又は全体が炭素材料で被覆されており、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）が３．５以上であり、比表面積Ｓが１３ｍ2／ｇ＜Ｓ≦４０ｍ2／ｇであり、粒子径ｄとＸ線回折で得られる半値幅から求められる結晶子径Ｄとの比（ｄ／Ｄ）が１以上１．３５以下であることを特徴とする。 In order to solve the above problems, the positive electrode active material for a non-aqueous secondary battery according to the present invention has a chemical formula Li A Mn X M 1-X (PO 4 ) B (where 0.8 ≦ A ≦ 1.2, 0 8 ≦ B ≦ 1.2, 0.3 ≦ X <1, and M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr) The lithium composite oxide having a olivine type structure is covered, and a part or the whole of the surface of the lithium composite oxide is coated with a carbon material, and the area ratio of the carbon D band and the carbon G band by Raman measurement ( SD / S G ) is 3.5 or more, the specific surface area S is 13 m 2 / g <S ≦ 40 m 2 / g, and the crystallite diameter D is determined from the particle diameter d and the half width obtained by X-ray diffraction. The ratio (d / D) is 1 or more and 1.35 or less.
　本発明の非水系二次電池用正極活物質によれば、ラマン測定によるカーボンＤバンドとカーボンＧバンドとの面積比率が３．５以上と低結晶性であっても、電解液と核材であるリチウム複合酸化物との副反応を抑制でき、Ｍｎ溶出量が少なく高温保存特性が良好である。なお、上記した以外の課題、構成及び効果は、以下の実施形態の説明により明らかにされる。 According to the positive electrode active material for a non-aqueous secondary battery of the present invention, even if the area ratio of the carbon D band and the carbon G band by Raman measurement is 3.5 or more and low crystallinity, Side reactions with certain lithium composite oxides can be suppressed, the amount of Mn elution is small, and high temperature storage characteristics are good. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.
実施例２における正極活物質の走査型電子顕微鏡写真である。2 is a scanning electron micrograph of a positive electrode active material in Example 2. FIG. 実施例２における正極活物質のラマン測定結果を示す図である。It is a figure which shows the Raman measurement result of the positive electrode active material in Example 2. 比較例１における正極活物質の走査型電子顕微鏡写真である。2 is a scanning electron micrograph of a positive electrode active material in Comparative Example 1. 比較例２における正極活物質の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of a positive electrode active material in Comparative Example 2. 本発明の非水系二次電池の一実施形態の部分断面図である。It is a fragmentary sectional view of one embodiment of the non-aqueous secondary battery of the present invention.
　以下、実施形態に基づき本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail based on embodiments.
（正極活物質）
　本発明の非水系二次電池用正極活物質は、化学式ＬｉAＭｎXＭ1-X（ＰＯ4）B（式中、０．８≦Ａ≦１．２、０．８≦Ｂ≦１．２、０．３≦Ｘ＜１、ＭはＬｉ、Ｆｅ、Ｎｉ、Ｃｏ、Ｔｉ、Ｃｕ、Ｚｎ、Ｍｇ、及びＺｒから選ばれる一種以上の金属原子である）で表わされるオリビン型構造を有するリチウム複合酸化物を含む。特に、Ｍとしては高い電位を得ることができるＮｉ及びＣｏが好ましい。また、ＭとしてＦｅを用いると、導電性・Ｌｉイオン拡散性が向上し、充放電サイクル特性が良好になり好ましい。 (Positive electrode active material)
The positive electrode active material for a non-aqueous secondary battery of the present invention has a chemical formula Li A Mn X M 1-X (PO 4 ) B (where 0.8 ≦ A ≦ 1.2, 0.8 ≦ B ≦ 1. 2, 0.3 ≦ X <1, wherein M is one or more metal atoms selected from Li, Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr) Includes complex oxides. In particular, Ni and Co that can obtain a high potential are preferable as M. Further, it is preferable to use Fe as M because conductivity / Li ion diffusibility is improved and charge / discharge cycle characteristics are improved.
　Ｌｉ及びＰは、Ｍｎその他の金属原子に対して８０モル％以上１２０モル％以下である。Ｌｉが上記範囲内であれば、リチウム複合酸化物はオリビン型構造をとることができる。特に、Ｌｉ及びＰは、Ｍｎその他の金属原子に対し１００モル％以上１２０モル％以下であることが好ましい。Ｌｉ及びＰが上記範囲内であれば、副生成物として金属が生成されるのを防ぐことができる。したがって、負極での金属異物の析出を防止でき、短絡を防ぐことができ安全性が高まる。 Li and P are 80 mol% or more and 120 mol% or less with respect to Mn and other metal atoms. If Li is in the above range, the lithium composite oxide can have an olivine structure. In particular, Li and P are preferably 100 mol% or more and 120 mol% or less with respect to Mn and other metal atoms. When Li and P are within the above ranges, generation of metal as a by-product can be prevented. Therefore, precipitation of the metal foreign material in a negative electrode can be prevented, a short circuit can be prevented and safety can be improved.
　また、正極活物質は、Ｘ線回折で得られる半値幅から求められる結晶子径（Ｄとする）に対する粒子径（ｄとする）の比（ｄ／Ｄ）が、１以上１．３５以下である。ｄ／Ｄが１．３５以下であると、核材であるＬｉAＭｎXＭ1-XＰＯ4の結晶性が良く、欠陥が少ないためＬｉイオンの拡散性が高まり、結果として高容量が得られる。結晶子径Ｄは、粒子径ｄより大きくなることはなく、結晶子径Ｄが最大の時に粒子径ｄと一致するため、ｄ／Ｄの最小値は１である。したがって、ｄ／Ｄが１に近い値であるほど、結晶性が良くなる。 In addition, the positive electrode active material has a ratio (d / D) of a particle diameter (denoted as d) to a crystallite diameter (denoted as D) obtained from a half width obtained by X-ray diffraction is 1 or more and 1.35 or less. is there. When d / D is 1.35 or less, the crystallinity of the core material Li A Mn X M 1-X PO 4 is good, and since there are few defects, the diffusibility of Li ions increases, resulting in high capacity. It is done. The crystallite diameter D does not become larger than the particle diameter d and coincides with the particle diameter d when the crystallite diameter D is maximum, so the minimum value of d / D is 1. Therefore, the closer d / D is to 1, the better the crystallinity.
　なお、粒子径ｄは、無作為に抽出した正極活物質を、走査型電子顕微鏡（ＳＥＭ）又は透過型電子顕微鏡（ＴＥＭ）を用いて観察し、無作為に選んだ３視野以上を観察した結果から求めた平均粒子径である。個々の粒子は完全な球状ではないため、ＳＥＭ又はＴＥＭ像における粒子の長径と短径の平均値を粒子径とする。平均粒子径は、各視野で４０個の粒子を、粒子径が中央値に近い順から抽出し、３視野以上で抽出した全ての粒子径から求められる平均値である。 In addition, the particle diameter d is the result of observing a randomly extracted positive electrode active material using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and observing three or more randomly selected fields. The average particle size obtained from Since the individual particles are not perfectly spherical, the average value of the major axis and minor axis of the particle in the SEM or TEM image is taken as the particle diameter. The average particle diameter is an average value obtained from all the particle diameters extracted from the order of 40 particle diameters in each visual field extracted from the order in which the particle diameters are close to the median value.
　また、結晶子径Ｄは、Ｘ線回折（ＸＲＤ）測定結果における半値幅から求められる物性値である。ＸＲＤ測定は集中法で行い、Ｘ線はＣｕＫα線を用い、出力は４０ｋＶ、４０ｍＡとする。ステップ幅が０．０３°、１ステップ当たりの測定時間が１５秒の条件で測定を行い、測定データをＳａｖｉｔｚｋｙ－Ｇｏｌｅｙ法によりスムージングした後、バックグラウンド及びＫα2線を除去し、その時の（１０１）ピーク（空間群をＰｍｎａとする）の半値幅βexpを求める。さらに、同一装置、同一条件で標準Ｓｉサンプル（ＮＩＳＴ標準試料６４０ｄ）を測定し、ピークの半値幅βiを求め、下記の式 Further, the crystallite diameter D is a physical property value obtained from the half width in the X-ray diffraction (XRD) measurement result. The XRD measurement is performed by the concentration method, the X-ray is CuKα ray, and the output is 40 kV and 40 mA. Measurement was performed under the condition that the step width was 0.03 °, and the measurement time per step was 15 seconds. The measurement data was smoothed by the Savitzky-Goley method, and then the background and Kα 2 line were removed. ) Find the full width at half maximum β exp of the peak (space group is Pmna). Further, a standard Si sample (NIST standard sample 640d) was measured under the same apparatus and under the same conditions, and a half width β i of the peak was obtained.
Figure JPOXMLDOC01-appb-M000001
 により半値幅βを定義する。この半値幅βを用い、下記のＳｃｈｅｒｒｅｒの式
Figure JPOXMLDOC01-appb-M000001
 Defines the half width β. Using this half-value width β, the following Scherrer equation
Figure JPOXMLDOC01-appb-M000002
 を用いて結晶子径Ｄを求める。ここでλはＸ線源の波長であり、θは反射角であり、ＫはＳｃｈｅｒｒｅｒ定数であり、Ｋ＝０．９とする。
Figure JPOXMLDOC01-appb-M000002
 Is used to determine the crystallite diameter D. Here, λ is the wavelength of the X-ray source, θ is the reflection angle, K is a Scherrer constant, and K = 0.9.
　本発明の正極活物質は、リチウム複合酸化物の表面の一部又は全体が炭素材料で被覆されており、ラマン測定によるカーボンＤバンドの面積（ＳD）とカーボンＧバンドの面積（ＳG）の面積比率（ＳD／ＳG）が３．５以上である。粒子径を抑制するために低温で焼成すると、炭素材料が低結晶性となり、面積比率（ＳD／ＳG）が３．５以上となる。炭素材料による被覆は、全てが炭素材料である必要はなく、一部が炭素材料以外の材料であっても構わない。 In the positive electrode active material of the present invention, a part or the whole of the surface of the lithium composite oxide is coated with a carbon material, and the area of the carbon D band (S D ) and the area of the carbon G band (S G ) by Raman measurement. The area ratio (S D / S G ) is 3.5 or more. When fired at a low temperature in order to suppress the particle diameter, the carbon material becomes low crystalline, and the area ratio (S D / S G ) is 3.5 or more. The coating with the carbon material does not necessarily have to be a carbon material, and a part thereof may be a material other than the carbon material.
　また、正極活物質の炭素含有量は、０．５重量％以上３０重量％未満であることが好ましい。炭素含有量を０．５重量％以上とすることで、良好な導電性が得られ容量を高めることができ、核材であるリチウム複合酸化物と電解液との副反応を抑制できる。特に、炭素含有量は１重量％以上であることがより好ましい。炭素含有量が１重量％以上であると、導電性が良くなりレート特性が改善される。また、炭素含有量が３０重量％より多いと電池容量が低下する。炭素含有量は５重量％以下であることがより好ましい。炭素含有量が５重量％以下であると電極容量の低下をより効果的に抑制することができる。 Further, the carbon content of the positive electrode active material is preferably 0.5% by weight or more and less than 30% by weight. By setting the carbon content to 0.5% by weight or more, good conductivity can be obtained, the capacity can be increased, and side reactions between the lithium composite oxide as a core material and the electrolytic solution can be suppressed. In particular, the carbon content is more preferably 1% by weight or more. When the carbon content is 1% by weight or more, conductivity is improved and rate characteristics are improved. On the other hand, when the carbon content is more than 30% by weight, the battery capacity decreases. The carbon content is more preferably 5% by weight or less. When the carbon content is 5% by weight or less, the decrease in electrode capacity can be more effectively suppressed.
　正極活物質の比表面積Ｓは、１３ｍ2／ｇ＜Ｓ≦４０ｍ2／ｇとする。比表面積Ｓが１３ｍ2／ｇより大きいと、正極活物質と電解液との反応場が広くなり、抵抗が低下して高容量となる。また、比表面積Ｓが４０ｍ2／ｇ以下であると、電解液中のフッ化水素と核材であるＬｉAＭｎXＭ1-X（ＰＯ4）Bとの副反応を抑制でき、Ｍｎや金属の溶出及び抵抗層の生成を抑制でき、高温保存特性が良好となる。 The specific surface area S of the positive electrode active material is 13 m 2 / g <S ≦ 40 m 2 / g. When the specific surface area S is larger than 13 m 2 / g, the reaction field between the positive electrode active material and the electrolyte is widened, the resistance is lowered, and the capacity is increased. Further, when the specific surface area S is 40 m 2 / g or less, side reaction between hydrogen fluoride in the electrolyte and Li A Mn X M 1-X (PO 4 ) B as a core material can be suppressed, and Mn and Elution of metal and generation of a resistance layer can be suppressed, and high-temperature storage characteristics are improved.
　正極活物質の粒子径は、１０ｎｍ以上５００ｎｍ以下であることが好ましい。粒子径ｄが１０ｎｍ未満であると、嵩密度が高く体積当たりの容量が低下する。また、粒子径ｄが５００ｎｍを超えるとＬｉイオンの拡散パスが長くなり、高抵抗となって容量が低下する。特に、粒子径ｄは３０ｎｍ以上５０ｎｍ以下であることがより好ましい。正極活物質が１次粒子として凝集せず、単分散である場合、３０ｎｍ以上５０ｎｍ以下であると高容量となり、且つ高温保存特性が良好となる。なお、正極活物質は、造粒等により二次粒子化していても構わない。 The particle size of the positive electrode active material is preferably 10 nm or more and 500 nm or less. When the particle diameter d is less than 10 nm, the bulk density is high and the capacity per volume is reduced. On the other hand, when the particle diameter d exceeds 500 nm, the Li ion diffusion path becomes longer, resulting in higher resistance and lower capacity. In particular, the particle diameter d is more preferably 30 nm or more and 50 nm or less. When the positive electrode active material is not agglomerated as primary particles and is monodispersed, a capacity of 30 nm or more and 50 nm or less results in a high capacity and good high-temperature storage characteristics. The positive electrode active material may be made into secondary particles by granulation or the like.
（正極活物質の製造方法）
　以上のような非水系二次電池用正極活物質は、リチウム複合酸化物の原料を混合する工程と、混合した原料を仮焼成する工程と、仮焼成により得られる仮焼成体に炭素源を混合する工程と、混合した仮焼成体及び炭素源を本焼成する工程とを含む方法により製造することができる。本焼成工程における焼成温度は、リチウム複合酸化物の結晶化温度以上であり、且つその結晶化温度に４００℃を加えた温度以下であることが好ましい。結晶化温度に４００℃を加えた温度以下で本焼成工程を行うことで、粒成長を抑制することができ、小粒子径の正極活物質を得ることができる。また、低温で焼成するため低コストとなる。 (Method for producing positive electrode active material)
The positive electrode active material for a non-aqueous secondary battery as described above includes a step of mixing raw materials of a lithium composite oxide, a step of pre-baking the mixed raw materials, and a carbon source mixed with a pre-fired body obtained by pre-baking And a method including a step of subjecting the mixed calcined body and the carbon source to main firing. The firing temperature in the main firing step is preferably not less than the crystallization temperature of the lithium composite oxide and not more than a temperature obtained by adding 400 ° C. to the crystallization temperature. By performing the main baking step at a temperature equal to or lower than 400 ° C. added to the crystallization temperature, grain growth can be suppressed and a positive electrode active material having a small particle diameter can be obtained. Moreover, since it bakes at low temperature, it becomes low cost.
　仮焼成体と混合する炭素源としては、スクロース、ラクトース、マルトース、トレハロース、ツラノース、セロビオース、グルコース、グリコーゲン、デンプン、セルロース、デキストリン等の糖類、ピッチ系炭素材料等から適宜選択することができる。また、混合する量は、上述の炭素含有量を考慮して定めることができる。 The carbon source to be mixed with the calcined product can be appropriately selected from sucrose, lactose, maltose, trehalose, turanose, cellobiose, glucose, glycogen, starch, cellulose, dextrin and other sugars, pitch-based carbon materials, and the like. The amount to be mixed can be determined in consideration of the above-described carbon content.
（非水系二次電池用正極）
　本発明の非水系二次電池用正極活物質を用いることにより、高容量且つ高温保存特性が良好な非水系二次電池用正極を作製することができる。正極は、従来知られた方法により作製することができ、具体的には、例えば、上記の正極活物質と、導電材及びバインダーとを混練し、Ｎ－メチルピロリドン等の分散溶媒を添加して適宜希釈することにより正極合剤スラリーを調製する。その正極合剤スラリーを、正極集電体として用いるアルミニウム箔等の表面に塗布した後、乾燥し、加圧ローラーでプレス等することにより正極合剤層を集電体上に形成して正極を作製する。 (Positive electrode for non-aqueous secondary batteries)
By using the positive electrode active material for a non-aqueous secondary battery of the present invention, a positive electrode for a non-aqueous secondary battery having a high capacity and good high-temperature storage characteristics can be produced. The positive electrode can be produced by a conventionally known method. Specifically, for example, the above positive electrode active material, a conductive material and a binder are kneaded, and a dispersion solvent such as N-methylpyrrolidone is added. A positive electrode mixture slurry is prepared by appropriately diluting. The positive electrode mixture slurry is applied to the surface of an aluminum foil or the like used as a positive electrode current collector, and then dried and pressed with a pressure roller to form a positive electrode mixture layer on the current collector to form a positive electrode. Make it.
　バインダーとしては、特に限定されるものではないが、ポリフッ化ビニリデン、ポリアクリロニトリル、スチレン－ブタジエンゴム等が適用可能である。また、導電材としては、例えば、黒鉛、アセチレンブラック、カーボンブラック、カーボンファイバー、金属炭化物等のカーボン材料が適用可能であり、それぞれ単独で又は２種以上を混合して用いることができる。 The binder is not particularly limited, but polyvinylidene fluoride, polyacrylonitrile, styrene-butadiene rubber and the like are applicable. In addition, as the conductive material, for example, carbon materials such as graphite, acetylene black, carbon black, carbon fiber, and metal carbide can be applied, and each can be used alone or in admixture of two or more.
（非水系二次電池）
　そして、上記正極を用いることにより、高容量且つ高温保存特性が良好な非水系二次電池を得ることができる。非水系二次電池の構成としては、従来知られた一般的な構成を採用することができる。 (Non-aqueous secondary battery)
By using the positive electrode, a non-aqueous secondary battery having a high capacity and good high-temperature storage characteristics can be obtained. As a configuration of the non-aqueous secondary battery, a conventionally known general configuration can be adopted.
　図５に、本発明に係る非水系二次電池の一実施形態の部分断面図を示す。図５の非水系二次電池４は、正極５と負極６との間にセパレータ７が配置される。これら正極５、負極６及びセパレータ７が捲回され、非水電解液（図示せず）と共にステンレス製又はアルミニウム製の電池缶１０に封入される。 FIG. 5 shows a partial cross-sectional view of an embodiment of a non-aqueous secondary battery according to the present invention. In the nonaqueous secondary battery 4 of FIG. 5, a separator 7 is disposed between the positive electrode 5 and the negative electrode 6. The positive electrode 5, the negative electrode 6 and the separator 7 are wound and sealed together with a non-aqueous electrolyte (not shown) in a battery can 10 made of stainless steel or aluminum.
　正極５には正極リード８が設けられ、負極６には負極リード９が設けられており、それぞれ電流が取り出されるように構成されている。正極５と負極リード９との間、負極６と正極リード８との間には、それぞれ絶縁板１２が設けられている。また、負極リード９に接触している電池缶１０と、正極リード８に接触している密閉蓋部１３との間には、電解液の漏れ防止と共にプラス極とマイナス極とを分けるためのパッキン１１が設けられている。 The positive electrode 5 is provided with a positive electrode lead 8, and the negative electrode 6 is provided with a negative electrode lead 9, each configured to extract current. Insulating plates 12 are respectively provided between the positive electrode 5 and the negative electrode lead 9 and between the negative electrode 6 and the positive electrode lead 8. Further, between the battery can 10 in contact with the negative electrode lead 9 and the sealing lid portion 13 in contact with the positive electrode lead 8, a packing for separating the positive electrode and the negative electrode as well as preventing leakage of the electrolyte. 11 is provided.
　本発明の非水系二次電池においては、電解液にＬｉＰＦ6が含まれていることが好ましい。本発明の非水系二次電池用正極活物質を用いることで、電解液にＬｉＰＦ6が含まれていても高温保存特性が良好となり、ＬｉＰＦ6に起因する良好な出力特性を得ることができる。すなわち、高容量で、高温保存特性が良好であり、且つ良好な出力特性を有する二次電池を得ることができる。ＬｉＰＦ6を含む場合、その含有量は、電解液中０．０１～５モル％とすることが好ましい。 In the non-aqueous secondary battery of the present invention, it is preferable that LiPF 6 is contained in the electrolytic solution. By using the positive electrode active material for a non-aqueous secondary battery of the present invention, high temperature storage characteristics are improved even when LiPF 6 is contained in the electrolytic solution, and good output characteristics resulting from LiPF 6 can be obtained. That is, it is possible to obtain a secondary battery having a high capacity, good high-temperature storage characteristics, and good output characteristics. When LiPF 6 is contained, its content is preferably 0.01 to 5 mol% in the electrolytic solution.
　次に、実施例及び比較例により、本発明をさらに詳細に説明するが、これらに限定されるものではない。 Next, the present invention will be described in more detail by way of examples and comparative examples, but is not limited thereto.
（実施例１）
　クエン酸鉄（ＦｅＣ6Ｈ5Ｏ7・ｎＨ2Ｏ）及びクエン酸一水和物（Ｃ6Ｈ8Ｏ7・Ｈ2Ｏ）を純水に溶解した。得られた溶液に、酢酸マンガン四水和物（Ｍｎ（ＣＨ3ＣＯＯ）2・４Ｈ2Ｏ）を純水に溶解させた溶液を加え、さらにリン酸二水素リチウム及び酢酸リチウム水溶液を純水に溶解させた溶液を加えた。得られた溶液を、スプレードライヤーを用い乾燥し、原料粉末を得た。この原料粉末を４４０℃で１０時間仮焼成し、仮焼成体を得た。得られた仮焼成体１００重量部と炭素源としてスクロース５重量部とを混合した。そして、得られた混合粉末を７００℃で１０時間本焼成し、目的の正極活物質を製造した。なお、本焼成の際の焼成温度は、核材であるリチウム複合酸化物の結晶化温度より３００℃高い温度に相当する。得られた正極活物質は、Ｘ線回折で測定したところ、核材が化学式ＬｉＭｎＦｅＰＯ4で表されるオリビン型構造を有するリチウム複合酸化物であり、ラマン測定したところ、表面が炭素材料で被覆されていた。 Example 1
Iron citrate (FeC 6 H 5 O 7 .nH 2 O) and citric acid monohydrate (C 6 H 8 O 7 .H 2 O) were dissolved in pure water. To the obtained solution, a solution in which manganese acetate tetrahydrate (Mn (CH 3 COO) 2 .4H 2 O) was dissolved in pure water was added. Further, lithium dihydrogen phosphate and an aqueous lithium acetate solution were added to the pure water. The dissolved solution was added. The obtained solution was dried using a spray dryer to obtain a raw material powder. This raw material powder was temporarily fired at 440 ° C. for 10 hours to obtain a temporarily fired body. 100 parts by weight of the obtained temporary fired body and 5 parts by weight of sucrose as a carbon source were mixed. And the obtained mixed powder was main-baked at 700 degreeC for 10 hours, and the target positive electrode active material was manufactured. Note that the firing temperature at the time of the main firing corresponds to a temperature 300 ° C. higher than the crystallization temperature of the lithium composite oxide as the core material. The obtained positive electrode active material was measured by X-ray diffraction. The core material was a lithium composite oxide having an olivine structure represented by the chemical formula LiMnFePO 4. When the Raman measurement was performed, the surface was coated with a carbon material. It was.
　正極活物質の炭素含有量は２．０重量％であった。また、正極活物質の比表面積は、触媒分析装置ＢＥＬ－ＣＡＴ（日本ベル社製）を用いて測定したところ、１５．０ｍ2／ｇであった。表面積当たりの炭素被覆量は１．３ｍｇ／ｍ2であった。さらに、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）は４．４であった。さらに、透過型顕微鏡観察及びＸ線回折の結果によれば、正極活物質の粒子径ｄは４５ｎｍであり、結晶子径Ｄは３８ｎｍであり、粒子径ｄと結晶子径Ｄとの比（ｄ／Ｇ）は１．２であった。 The carbon content of the positive electrode active material was 2.0% by weight. The specific surface area of the positive electrode active material was 15.0 m 2 / g as measured using a catalyst analyzer BEL-CAT (manufactured by Nippon Bell Co., Ltd.). The carbon coating amount per surface area was 1.3 mg / m 2 . Furthermore, the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4. Furthermore, according to the results of transmission microscope observation and X-ray diffraction, the particle diameter d of the positive electrode active material is 45 nm, the crystallite diameter D is 38 nm, and the ratio of the particle diameter d to the crystallite diameter D (d / G) was 1.2.
（実施例２）
　スクロースを７重量部とした以外は、上記実施例１と同様の方法により正極活物質を作製した。図１に、正極活物質１のＳＥＭ像を示す。また、得られた正極活物質を高周波誘導結合プラズマ発光分光分析（ＩＣＰ－ＡＥＳ）により元素分析した結果、Ｍｎ量は２７重量％、Ｆｅ量は６．５重量％であった。炭素含有量は２．０重量％であった。粒子径ｄは３９ｎｍ、結晶子径Ｄは３２ｎｍでありｄ／Ｄは１．２であった。また、比表面積は、触媒分析装置ＢＥＬ－ＣＡＴ（日本ベル社製）を用い測定したところ、２３．１ｍ2／ｇであった。表面積当たりの炭素被覆量は０．９ｍｇ／ｍ2であった。図２に、正極活物質のラマン測定結果を示す。ラマン測定によるカーボンＤバンド３とカーボンＧバンド２の面積比率（ＳD／ＳG）は４．４であった。 (Example 2)
A positive electrode active material was prepared in the same manner as in Example 1 except that 7 parts by weight of sucrose was used. FIG. 1 shows an SEM image of the positive electrode active material 1. The obtained positive electrode active material was subjected to elemental analysis by high frequency inductively coupled plasma optical emission spectrometry (ICP-AES). As a result, the Mn content was 27% by weight and the Fe content was 6.5% by weight. The carbon content was 2.0% by weight. The particle diameter d was 39 nm, the crystallite diameter D was 32 nm, and d / D was 1.2. The specific surface area was 23.1 m 2 / g as measured using a catalyst analyzer BEL-CAT (manufactured by Nippon Bell Co., Ltd.). The carbon coating amount per surface area was 0.9 mg / m 2 . In FIG. 2, the Raman measurement result of a positive electrode active material is shown. The area ratio (S D / S G ) of the carbon D band 3 and the carbon G band 2 by Raman measurement was 4.4.
（実施例３）
　スクロースを１０重量部とした以外は、上記実施例１と同様の方法により正極活物質を作製した。炭素含有量は２．０重量％であった。また、正極活物質の比表面積は３６．１ｍ2／ｇであった。表面積当たりの炭素被覆量は０．９ｍｇ／ｍ2であった。また、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）は４．４であった。さらに、正極活物質の粒子径ｄは３５ｎｍであり、Ｘ線回折で得られる半値幅から求められる結晶子径Ｄは３０ｎｍであり、ｄ／Ｄは１．２であった。 (Example 3)
A positive electrode active material was produced in the same manner as in Example 1 except that 10 parts by weight of sucrose was used. The carbon content was 2.0% by weight. The specific surface area of the positive electrode active material was 36.1 m 2 / g. The carbon coating amount per surface area was 0.9 mg / m 2 . Further, the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4. Furthermore, the particle diameter d of the positive electrode active material was 35 nm, the crystallite diameter D determined from the half width obtained by X-ray diffraction was 30 nm, and d / D was 1.2.
（比較例１）
　スクロースを３．５重量部とした以外は、上記実施例１と同様の方法により正極活物質を作製した。図３に正極活物質１のＳＥＭ像を示す。また、炭素含有量は１．９重量％であった。また、比表面積は６．２ｍ2／ｇであった。表面積当たりの炭素被覆量は３．０ｍｇ／ｍ2であった。さらに、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）は４．４であった。 (Comparative Example 1)
A positive electrode active material was produced in the same manner as in Example 1 except that sucrose was changed to 3.5 parts by weight. FIG. 3 shows an SEM image of the positive electrode active material 1. The carbon content was 1.9% by weight. The specific surface area was 6.2 m 2 / g. The carbon coating amount per surface area was 3.0 mg / m 2 . Furthermore, the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4.
（比較例２）
　スクロースを１４重量部とした以外は、上記実施例１と同様の方法により正極活物質を作製した。図４に正極活物質１のＳＥＭ像を示す。炭素含有量は３．８重量％であった。また、比表面積は４１．９ｍ2／ｇであった。表面積当たりの炭素被覆量は０．９ｍｇ／ｍ2であった。さらに、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）は４．４であった。 (Comparative Example 2)
A positive electrode active material was produced in the same manner as in Example 1 except that sucrose was changed to 14 parts by weight. FIG. 4 shows an SEM image of the positive electrode active material 1. The carbon content was 3.8% by weight. The specific surface area was 41.9 m 2 / g. The carbon coating amount per surface area was 0.9 mg / m 2 . Furthermore, the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 4.4.
（比較例３）
　仮焼成時の雰囲気をアルゴンとし、仮焼成後にスクロースを添加しない以外は、上記実施例１と同様の方法により正極活物質を作製した。得られた正極活物質の粒子径ｄは３５ｎｍ、結晶子径Ｄは２２ｎｍであり、ｄ／Ｄは１．６であった。また、炭素含有量は６．３重量％だった。 (Comparative Example 3)
A positive electrode active material was produced in the same manner as in Example 1 except that the atmosphere during the pre-baking was argon and sucrose was not added after the pre-baking. The obtained positive electrode active material had a particle diameter d of 35 nm, a crystallite diameter D of 22 nm, and d / D of 1.6. The carbon content was 6.3% by weight.
（比較例４）
　本焼成温度を９００℃とした以外は、実施例２と同様の方法により正極活物質を作製した。得られた正極活物質の粒子径ｄは１５０ｎｍであった。また、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）は３．１であった。 (Comparative Example 4)
A positive electrode active material was produced in the same manner as in Example 2 except that the main firing temperature was 900 ° C. The particle diameter d of the obtained positive electrode active material was 150 nm. Further, the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement was 3.1.
（正極作製方法）
　実施例１～３、及び比較例１～４で作製した正極活物質８２．５重量部、導電材としてアセチレンブラック（電気化学工業株式会社製、デンカブラック（登録商標））１０重量部、及びバインダーとして変性ポリアクリロニトリル７．５重量部をＮ－メチルピロリドンに溶解した溶液を混錬し正極合剤スラリーを調製した。得られた正極合剤スラリーを、アルミ箔上に塗布機を用いて均一に塗布した。大気中にて８０℃で乾燥後、φ１５ｍｍに打抜き加圧して正極を得た。 (Positive electrode fabrication method)
82.5 parts by weight of the positive electrode active material prepared in Examples 1 to 3 and Comparative Examples 1 to 4, 10 parts by weight of acetylene black (Denka Black (registered trademark) manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and binder A mixture of 7.5 parts by weight of modified polyacrylonitrile dissolved in N-methylpyrrolidone was kneaded to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry was uniformly coated on an aluminum foil using a coating machine. After drying at 80 ° C. in the air, a positive electrode was obtained by punching and pressing to φ15 mm.
（電極特性評価）
　上記により作製したそれぞれの正極について、電極特性を評価した。電解液として、エチレンカーボネート及びエチルメチルカーボネートの混合溶媒にビニレンカーボネートを添加し、これに１Ｍ　ＬｉＰＦ6を添加したものを用いた。また、負極にはリチウム金属を用いた。 (Electrode characteristic evaluation)
Electrode characteristics were evaluated for each positive electrode produced as described above. As the electrolytic solution, vinylene carbonate was added to a mixed solvent of ethylene carbonate and ethyl methyl carbonate, and 1M LiPF 6 was added thereto. Moreover, lithium metal was used for the negative electrode.
　充放電試験は、４．５Ｖ（ｖｓ．Ｌｉ／Ｌｉ+）となるまで定電流定電圧充電を行い、２Ｖ（ｖｓ．Ｌｉ／Ｌｉ+）となるまで定電流放電を行った。充放電電流値は０．１Ｃとした。３サイクル目の放電容量を初期放電容量とした。測定結果を表１に示す。 In the charge / discharge test, constant current / constant voltage charging was performed until 4.5 V (vs. Li / Li + ) was performed, and constant current discharging was performed until 2 V (vs. Li / Li + ) was achieved. The charge / discharge current value was 0.1C. The discharge capacity at the third cycle was defined as the initial discharge capacity. The measurement results are shown in Table 1.
（Ｍｎ溶出量評価及び維持率評価）
　実施例１～３、比較例１及び比較例２の正極活物質を用いた正極について、Ｍｎ溶出量を評価した。まず、上記の充放電試験と同様の条件で充放電を３サイクル行う。次に、正極を炭酸ジメチルで洗浄後、電解液５ｍｌ中に浸漬させる。そして、アルゴン雰囲気下、８０℃で１４日間保存する。保存後に電解液に溶出したＭｎ溶出量を、ＩＣＰ－ＡＥＳで測定した。その結果を表１に示す。また、保存後の電極特性評価を行い、２サイクル目の放電容量を保存後放電容量として測定した。その結果を表１に示す。維持率は保存後放電容量を初期放電容量で割り１００を乗じた値である。 (Mn elution evaluation and maintenance rate evaluation)
With respect to the positive electrodes using the positive electrode active materials of Examples 1 to 3, Comparative Example 1 and Comparative Example 2, the Mn elution amount was evaluated. First, charge / discharge is performed for 3 cycles under the same conditions as in the charge / discharge test. Next, after washing the positive electrode with dimethyl carbonate, it is immersed in 5 ml of an electrolytic solution. And it preserve | saves at 80 degreeC under argon atmosphere for 14 days. The amount of Mn eluted into the electrolyte after storage was measured by ICP-AES. The results are shown in Table 1. Further, the electrode characteristics after storage were evaluated, and the discharge capacity at the second cycle was measured as the discharge capacity after storage. The results are shown in Table 1. The maintenance rate is a value obtained by dividing the discharge capacity after storage by the initial discharge capacity and multiplying by 100.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　正極活物質のラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）が４．４であり、表１に示すように正極活物質の比表面積が１３ｍ2／ｇより大きく４０ｍ2／ｇ以下である実施例１～３は、初期放電容量が１３１Ａｈ／ｋｇ以上と高容量であり、高温保存後のＭｎ溶出量が２．２％以下と少なく放電容量の維持率も９７％以上と高いことから、高容量且つ高温保存特性が良好である。一方、正極活物質の比表面積が１３ｍ2／ｇ以下である比較例１は、初期放電容量が１１０Ａｈ／ｋｇと低容量である。また、比表面積が４０ｍ2／ｇより大きい比較例２では、Ｍｎ溶出量が４．９％と多くなり、高温保存後の放電容量の維持率も８９％と低く、高温保存特性が悪いことが分かった。また、ｄ／Ｄが１．６であることから核材が低結晶性である比較例３は、初期放電容量が１１０Ａｈ／ｋｇと低い。さらに、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）が３．１である比較例４は、粒子径が肥大となり初期放電容量が１２１Ａｈ／ｋｇと低い。 The area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement of the positive electrode active material is 4.4, and the specific surface area of the positive electrode active material is larger than 13 m 2 / g as shown in Table 1. In Examples 1 to 3, which are 40 m 2 / g or less, the initial discharge capacity is as high as 131 Ah / kg or more, the Mn elution amount after high-temperature storage is as small as 2.2% or less, and the discharge capacity maintenance rate is also 97 Since it is as high as% or more, high capacity and high temperature storage characteristics are good. On the other hand, Comparative Example 1 in which the positive electrode active material has a specific surface area of 13 m 2 / g or less has an initial discharge capacity as low as 110 Ah / kg. Further, in Comparative Example 2 having a specific surface area larger than 40 m 2 / g, the elution amount of Mn is as high as 4.9%, the discharge capacity retention rate after high-temperature storage is as low as 89%, and high-temperature storage characteristics are poor. I understood. Further, since d / D is 1.6, Comparative Example 3 in which the core material has low crystallinity has an initial discharge capacity as low as 110 Ah / kg. Further, in Comparative Example 4 in which the area ratio (S D / S G ) of the carbon D band and the carbon G band by Raman measurement is 3.1, the particle diameter is enlarged and the initial discharge capacity is as low as 121 Ah / kg.
　以上の結果から、正極活物質の比表面積が１３ｍ2／ｇより大きく４０ｍ2／ｇ以下であると、高容量で且つ高温保存特性が良好であることが明らかとなった。したがって、本発明の正極活物質が高容量で且つ高温保存特性が良好であることが示された。 From the above results, it was revealed that when the specific surface area of the positive electrode active material was larger than 13 m 2 / g and not larger than 40 m 2 / g, the high capacity and the high temperature storage characteristics were good. Therefore, it was shown that the positive electrode active material of the present invention has a high capacity and good high-temperature storage characteristics.
　本発明の非水系二次電池用正極は、高容量の大型リチウムイオン二次電池が必要とされる移動体や定置型電力貯蔵用電源への適用が期待される。 The positive electrode for a non-aqueous secondary battery of the present invention is expected to be applied to a mobile body and a stationary power storage power source that require a large-capacity large-sized lithium ion secondary battery.
１　　正極活物質
２　　カーボンＧバンド
３　　カーボンＤバンド
４　　非水系二次電池
５　　正極
６　　負極
７　　セパレータ
８　　正極リード
９　　負極リード
１０　電池缶
１１　パッキン
１２　絶縁板
１３　密閉蓋部 DESCRIPTION OF SYMBOLS 1 Positive electrode active material 2 Carbon G band 3 Carbon D band 4 Non-aqueous secondary battery 5 Positive electrode 6 Negative electrode 7 Separator 8 Positive electrode lead 9 Negative electrode lead 10 Battery can 11 Packing 12 Insulating plate 13 Sealing lid part

Claims (7)

  1. 　化学式ＬｉAＭｎXＭ1-X（ＰＯ4）B（式中、０．８≦Ａ≦１．２、０．８≦Ｂ≦１．２、０．３≦Ｘ＜１、ＭはＬｉ、Ｆｅ、Ｎｉ、Ｃｏ、Ｔｉ、Ｃｕ、Ｚｎ、Ｍｇ、及びＺｒから選ばれる一種以上の金属原子である）で表わされるオリビン型構造を有するリチウム複合酸化物を含み、前記リチウム複合酸化物の表面の一部又は全体が炭素材料で被覆されており、ラマン測定によるカーボンＤバンドとカーボンＧバンドの面積比率（ＳD／ＳG）が３．５以上であり、比表面積Ｓが１３ｍ2／ｇ＜Ｓ≦４０ｍ2／ｇであり、粒子径ｄとＸ線回折で得られる半値幅から求められる結晶子径Ｄとの比（ｄ／Ｄ）が１以上１．３５以下である非水系二次電池用正極活物質。 Chemical formula Li A Mn X M 1-X (PO 4 ) B (where 0.8 ≦ A ≦ 1.2, 0.8 ≦ B ≦ 1.2, 0.3 ≦ X <1, M is Li, A lithium composite oxide having an olivine type structure represented by Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr). Part or the whole is coated with a carbon material, the area ratio (S D / S G ) of the carbon D band and carbon G band by Raman measurement is 3.5 or more, and the specific surface area S is 13 m 2 / g < Non-aqueous secondary battery in which S ≦ 40 m 2 / g and the ratio (d / D) between the particle diameter d and the crystallite diameter D obtained from the half width obtained by X-ray diffraction is 1 or more and 1.35 or less Positive electrode active material.
  2. 　正極活物質の炭素含有量が、０．５重量％以上３０重量％未満である請求項１に記載の非水系二次電池用正極活物質。 The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein the positive electrode active material has a carbon content of 0.5 wt% or more and less than 30 wt%.
  3. 　正極活物質の粒子径ｄが、１０ｎｍ以上５００ｎｍ以下である請求項１に記載の非水系二次電池用正極活物質。 The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein the particle diameter d of the positive electrode active material is 10 nm or more and 500 nm or less.
  4. 　請求項１～３のいずれかに記載の非水系二次電池用正極活物質の製造方法であって、リチウム複合酸化物の原料を混合する工程と、混合した原料を仮焼成する工程と、仮焼成により得られる仮焼成体に炭素源を混合する工程と、混合した仮焼成体及び炭素源を本焼成する工程とを含み、本焼成する工程における焼成温度が、リチウム複合酸化物の結晶化温度以上であり且つ前記結晶化温度に４００℃を加えた温度以下である前記製造方法。 A method for producing a positive electrode active material for a non-aqueous secondary battery according to any one of claims 1 to 3, comprising a step of mixing a raw material of a lithium composite oxide, a step of temporarily firing the mixed raw material, Including a step of mixing a carbon source with a pre-fired body obtained by firing and a step of subjecting the mixed pre-fired body and carbon source to main firing, and the firing temperature in the main firing step is a crystallization temperature of the lithium composite oxide The manufacturing method as described above, which is not higher than a temperature obtained by adding 400 ° C. to the crystallization temperature.
  5. 　請求項１～３のいずれかに記載の非水系二次電池用正極活物質を用いた非水系二次電池用正極。 A positive electrode for a non-aqueous secondary battery using the positive electrode active material for a non-aqueous secondary battery according to any one of claims 1 to 3.
  6. 　請求項５に記載の非水系二次電池用正極を有する非水系二次電池。 A non-aqueous secondary battery comprising the positive electrode for a non-aqueous secondary battery according to claim 5.
  7. 　電解液にＬｉＰＦ6が含まれている請求項６に記載の非水系二次電池。 The nonaqueous secondary battery according to claim 6 , wherein LiPF 6 is contained in the electrolytic solution.
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