WO2021182488A1 - 蓄電素子 - Google Patents

蓄電素子 Download PDF

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Publication number
WO2021182488A1
WO2021182488A1 PCT/JP2021/009403 JP2021009403W WO2021182488A1 WO 2021182488 A1 WO2021182488 A1 WO 2021182488A1 JP 2021009403 W JP2021009403 W JP 2021009403W WO 2021182488 A1 WO2021182488 A1 WO 2021182488A1
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Prior art keywords
negative electrode
active material
electrode active
power storage
graphite particles
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PCT/JP2021/009403
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English (en)
French (fr)
Japanese (ja)
Inventor
和輝 川口
純 大山
大聖 関口
智典 加古
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GS Yuasa International Ltd
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GS Yuasa International Ltd
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Priority to CN202180020302.3A priority Critical patent/CN115485899A/zh
Priority to JP2022507229A priority patent/JPWO2021182488A1/ja
Priority to US17/910,456 priority patent/US20230163302A1/en
Priority to DE112021001538.9T priority patent/DE112021001538T5/de
Publication of WO2021182488A1 publication Critical patent/WO2021182488A1/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/42—Powders or particles, e.g. composition thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/48—Conductive polymers
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/446—Initial charging measures
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 power storage element.
  • Non-aqueous electrolyte secondary batteries represented by lithium-ion non-aqueous electrolyte secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. due to their high energy density.
  • the non-aqueous electrolyte secondary battery generally includes an electrode body having a pair of electrodes electrically separated by a separator, and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between the two electrodes. It is configured to charge and discharge by doing so.
  • capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as power storage elements other than non-aqueous electrolyte secondary batteries.
  • a carbon material such as graphite is used as the negative electrode active material of the power storage element for the purpose of improving the energy density of the power storage element (see Patent Document 1).
  • graphite is used as the negative electrode active material, and the amount of electricity charged per mass of the negative electrode active material in the fully charged state of the power storage element with respect to the theoretical capacity per mass of graphite.
  • the negative electrode utilization rate which is a ratio
  • the capacity retention rate after the charge / discharge cycle at a high rate may be significantly reduced.
  • the present invention has been made based on the above circumstances, and when graphite is used as the negative electrode active material and the negative electrode utilization rate in the fully charged state of the power storage element is increased, after a charge / discharge cycle at a high rate. It is an object of the present invention to provide a power storage element capable of suppressing a decrease in the capacity retention rate of graphite.
  • the power storage element includes a negative electrode and a positive electrode, and the negative electrode is directly or indirectly laminated on the negative electrode base material. It has a negative electrode active material layer, the negative electrode active material layer contains a negative electrode active material, the negative electrode active material is mainly composed of solid graphite particles, and the aspect ratio of the solid graphite particles is 1 or more and 5 or less.
  • the negative electrode utilization rate which is the ratio of the amount of charged electricity per mass of the negative electrode active material in the fully charged state to the theoretical capacity per mass of graphite, is 0.65 or more.
  • a power storage element capable of suppressing a decrease in the capacity retention rate after a charge / discharge cycle at a high rate is provided. Can be provided.
  • FIG. 1 is an external perspective view showing an embodiment of a power storage element.
  • FIG. 2 is a schematic view showing an embodiment of a power storage device in which a plurality of power storage elements are assembled.
  • the power storage element includes a negative electrode and a positive electrode, and the negative electrode has a negative electrode base material and a negative electrode active material layer directly or indirectly laminated on the negative electrode base material.
  • the negative electrode active material layer contains the negative electrode active material, the negative electrode active material contains solid graphite particles as a main component, and the aspect ratio of the solid graphite particles is 1 or more and 5 or less, and the theory per mass of graphite.
  • the negative electrode utilization rate which is the ratio of the amount of charging electricity per mass of the negative electrode active material in the fully charged state to the capacity, is 0.65 or more.
  • the power storage element can suppress a decrease in the capacity retention rate after a charge / discharge cycle at a high rate.
  • the reason for this is not clear, but the following reasons can be inferred. That is, in a battery designed to have a large negative electrode utilization rate such as a negative electrode utilization rate of 0.65 or more, a high rate charge / discharge cycle using graphite as the negative electrode active material causes a significant decrease in the capacity retention rate. There is a risk.
  • the power storage element uses solid graphite particles having an aspect ratio of 1 or more and 5 or less as the main component of the negative electrode active material, so that the current distribution of the negative electrode is non-uniform during the charge / discharge cycle. It is possible to suppress the formation and the non-uniformity of the expansion amount. As a result, the power storage element can suppress a decrease in the capacity retention rate after the charge / discharge cycle at a high rate.
  • the “main component in the negative electrode active material” means the component having the highest content, and means the component contained in an amount of 50% by mass or more with respect to the total mass of the negative electrode active material.
  • the “aspect ratio” refers to the longest diameter A of the particles and the longest diameter B in the direction perpendicular to the diameter A in the cross section of the particles observed in the SEM image obtained by using a scanning electron microscope. It means the A / B value which is the ratio of.
  • the “fully charged state” is a state in which the power storage element is charged until the rated upper limit voltage for securing the rated capacity determined in advance is reached (typically, SOC (State of Charge) 100%). The state in which the power storage element is charged until it becomes).
  • the battery when charging is performed using the charge control device adopted by the power storage element, the battery is charged until the end-of-charge voltage is reached when the charge operation is stopped and controlled.
  • the state of being For example, after charging the power storage element with a current of 1/3 C at a constant current until it reaches the rated upper limit voltage or the charge end voltage, until the current reaches 0.01 C at the rated upper limit voltage or the charge end voltage.
  • the state in which constant voltage (CV) charging is performed is a typical example of the "fully charged state" here.
  • the "charged electricity amount per mass of the negative electrode active material in the fully charged state” is stored in the negative electrode active material of the unit mass in the state where the power storage element is charged until the rated upper limit voltage or the charging end voltage is reached.
  • “Actual charge capacity per mass of negative electrode active material” which means the maximum rechargeable capacity that the negative electrode active material can actually store reversibly (without destroying the structure of the active material). Is a different concept.
  • the amount of electricity charged per mass of the negative electrode active material in the fully charged state can be arbitrarily set according to the usage mode of the power storage element, etc., and is usually set to a value smaller than the actual charging capacity per mass of the negative electrode active material. Set.
  • Theoretical capacity refers to the maximum amount of electricity that a unit mass of active material can theoretically store in a assumed electrochemical reaction based on Faraday's law. For example, when the negative electrode active material is graphite, the theoretical capacity per mass of graphite is 372 mAh / g.
  • the negative electrode utilization rate is 0.80 or more and 0.90 or less.
  • the negative electrode utilization rate is within the above range, it is possible to achieve both high capacity and high energy density of the power storage element and the effect of suppressing a decrease in the charge / discharge cycle maintenance rate at a high rate at a higher level.
  • the average particle size of the solid graphite particles is preferably 5 ⁇ m or less.
  • the power storage element can suppress a decrease in the capacity retention rate after a charge / discharge cycle at a higher rate.
  • the "average particle size” means a value (median diameter: D50) in which the volume-based integrated distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50%.
  • the power storage element includes a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.
  • a non-aqueous electrolyte secondary battery will be described as a preferable example of the power storage element.
  • the positive electrode and the negative electrode usually form electrode bodies that are alternately superposed by stacking or winding through a separator.
  • the electrode body is housed in a battery container, and the battery container is filled with a non-aqueous electrolyte.
  • the negative electrode includes a negative electrode base material and a negative electrode active material layer that is directly or indirectly laminated on at least one surface of the negative electrode base material.
  • the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode may include an intermediate layer arranged between the negative electrode base material and the negative electrode active material layer.
  • the negative electrode base material is a base material having conductivity.
  • metals such as copper, nickel, stainless steel and nickel-plated steel or alloys thereof are used, and copper or a copper alloy is preferable.
  • examples of the form of the negative electrode base material include foil, a vapor-deposited film, and the like, and foil is preferable from the viewpoint of cost. That is, copper foil is preferable as the negative electrode base material. Examples of the copper foil include rolled copper foil and electrolytic copper foil.
  • conductive means that the volume resistivity is measured according to JIS-H-0505 (1975 years) is not more than 1 ⁇ 10 7 ⁇ ⁇ cm, "non-conductive "means that the volume resistivity is 1 ⁇ 10 7 ⁇ ⁇ cm greater.
  • the average thickness of the negative electrode base material is preferably 2 ⁇ m or more and 35 ⁇ m or less, more preferably 3 ⁇ m or more and 25 ⁇ m or less, further preferably 4 ⁇ m or more and 20 ⁇ m or less, and particularly preferably 5 ⁇ m or more and 15 ⁇ m or less.
  • the "average thickness of the base material” means a value obtained by dividing the punching mass when punching a base material having a predetermined area by the average particle size and the punching area of the base material.
  • the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode active material contains solid graphite particles as the main component. Since the negative electrode active material contains solid graphite particles as a main component, the capacity of the power storage element can be increased. Further, the negative electrode active material may contain other negative electrode active materials other than the solid graphite particles.
  • graphite is a carbon substance having an average lattice spacing d (002) of (002) planes measured by X-ray diffraction before charging / discharging or in a discharged state of less than 0.34 nm. ..
  • solid means that the inside of the particles is clogged and there are substantially no voids. More specifically, “solid” refers to the cross-section of a particle observed in an SEM image obtained using a scanning electron microscope (SEM), excluding voids within the particle with respect to the total area of the particle. It means that the area ratio is 95% or more. In a preferred embodiment, the area ratio of the solid graphite particles can be 97% or higher (eg, 99% or higher).
  • the discharged state refers to a state in which the open circuit voltage is 0.7 V or more in a unipolar battery using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and a metal Li as a counter electrode. Since the potential of the metal Li counter electrode in the open circuit state is substantially equal to the redox potential of Li, the open circuit voltage in the single pole battery is substantially equal to the potential of the negative electrode containing the carbon material with respect to the redox potential of Li. .. That is, the fact that the open circuit voltage of the single-pole battery is 0.7 V or more means that lithium ions that can be occluded and discharged are sufficiently released from the carbon material that is the negative electrode active material during charging and discharging. ..
  • the area ratio R of the graphite particles excluding the voids in the particles with respect to the total area of the particles can be determined by the following procedure.
  • (1) Preparation of sample for measurement The powder of graphite particles to be measured is fixed with a thermosetting resin. A cross-section polisher is used to expose the cross section of the graphite particles fixed with the resin, and a sample for measurement is prepared.
  • (2) Acquisition of SEM image JSM-7001F (manufactured by JEOL Ltd.) is used as a scanning electron microscope to acquire the SEM image.
  • the SEM image shall be an observation of a secondary electron image.
  • the acceleration voltage is 15 kV.
  • the observation magnification is set so that the number of graphite particles appearing in one field of view is 3 or more and 15 or less.
  • the obtained SEM image is saved as an image file.
  • various conditions such as spot diameter, working distance, irradiation current, brightness, focus, etc. are appropriately set so that the outline of the graphite particles becomes clear.
  • Cutout of contour of graphite particles Using the image cropping function of the image editing software Adobe Photoshop Elements 11, the contour of graphite particles is cut out from the acquired SEM image. This contour clipping is performed by selecting the outside of the contour of the active material particles using the quick selection tool and editing the non-graphite particles to a black background.
  • Binarization process For the image of the first graphite particle among the cut out graphite particles, use the image analysis software PopImaging 6.00 from the concentration that maximizes the intensity inside the outline of the particle (inside the particle). The binarization process is performed by setting a concentration 20% smaller as the threshold value. By the binarization process, the area on the low concentration side is calculated to obtain "area S1 excluding voids in the particles".
  • the same image of the first graphite particles as before is binarized with a density of 10 as a threshold value.
  • the outer edge of the graphite particles is determined by the binarization treatment, and the area inside the outer edge is calculated to obtain "the total area S0 of the particles".
  • S1 that is, S1 / S0
  • the second and subsequent images of the graphite particles among the cut out graphite particles are also subjected to the above binarization treatment to calculate the area S1 and the area S0, respectively.
  • the area ratios R2, R3, ... Of the respective graphite particles are calculated.
  • Determining the area ratio R By calculating the average value of all the area ratios R1, R2, R3, ... Calculated by the binarization process, "the voids in the particles are defined with respect to the total area of the particles.
  • the area ratio R of the removed graphite particles is determined.
  • the solid graphite particles those having an appropriate aspect ratio and shape can be appropriately selected and used from among various known graphite particles.
  • known graphite particles include artificial graphite particles and natural graphite particles.
  • artificial graphite is a general term for artificially produced graphite
  • natural graphite is a general term for graphite obtained from natural minerals.
  • specific examples of the natural graphite particles include scaly graphite, lump graphite (scaly graphite), and earthy graphite.
  • the solid graphite particles may be flat scaly natural graphite particles or spheroidized natural graphite particles obtained by spheroidizing the scaly graphite.
  • the solid graphite particles are artificial graphite particles.
  • the solid graphite particles may be graphite particles having a surface coated (for example, an amorphous carbon coat).
  • the lower limit of the aspect ratio of the solid graphite particles is 1 (for example, 1.5), preferably 2.0.
  • the aspect ratio of the solid graphite particles may be 2.2 or greater (eg 2.5 or greater).
  • the aspect ratio of the solid graphite particles may be 2.3 or higher (eg 2.5 or higher, eg 2.7 or higher).
  • the upper limit of the aspect ratio of the solid graphite particles is 5 (for example, 4.5) from the viewpoint of better suppressing the decrease in the capacity retention rate after the charge / discharge cycle at a high rate. 2 is preferable.
  • the aspect ratio of the solid graphite particles may be 3.5 or less (eg 3.2 or less).
  • the aspect ratio can be determined as follows. (1) Preparation of measurement sample A measurement sample with an exposed cross section used for determining the area ratio R described above is used. (2) Acquisition of SEM image JSM-7001F (manufactured by JEOL Ltd.) is used as a scanning electron microscope to acquire the SEM image.
  • the SEM image shall be an observation of a secondary electron image.
  • the acceleration voltage is 15 kV.
  • the observation magnification is set so that the number of negative electrode active material particles appearing in one field of view is 100 or more and 1000 or less.
  • the obtained SEM image is saved as an image file.
  • various conditions such as spot diameter, working distance, irradiation current, brightness, focus, etc. are appropriately set so that the outline of the negative electrode active material particles becomes clear.
  • the lower limit of the average particle size of the solid graphite particles is preferably 0.5 ⁇ m, more preferably 1 ⁇ m (for example, 1.5 ⁇ m). In some embodiments, the average particle size of the solid graphite particles may be 2 ⁇ m or greater, or 2.5 ⁇ m or greater. As the upper limit of the average particle size, 10 ⁇ m (for example, 8 ⁇ m) is preferable, 5 ⁇ m is more preferable, and 4.8 ⁇ m is more preferable, from the viewpoint of better suppressing capacity deterioration at a high rate. In some embodiments, the average particle size of the solid graphite particles may be 4 ⁇ m or less, or 3.5 ⁇ m or less (eg, 3 ⁇ m or less).
  • the power storage element can suppress a decrease in the capacity retention rate after a charge / discharge cycle at a higher rate.
  • the technique disclosed herein can be preferably carried out in an embodiment in which the average particle size of the solid graphite particles is 1 ⁇ m or more and less than 8 ⁇ m (further, 2 ⁇ m or more and 5 ⁇ m or less, particularly 2 ⁇ m or more and 3.5 ⁇ m or less).
  • the solid graphite particles disclosed herein are those having an aspect ratio of 1 or more and 5 or less and a median diameter of 10 ⁇ m or less; an aspect ratio of 1.2 or more and 4.5 or less.
  • the median diameter is 5 ⁇ m or less; the aspect ratio is 1.3 or more and 4.2 or less, and the median diameter is 4.5 ⁇ m or less; the aspect ratio is 1.5 or more and 3.5 or less.
  • the median diameter is 3.5 ⁇ m or less; the aspect ratio is 2 or more and 3.5 or less and the median diameter is 3.5 ⁇ m or less: the aspect ratio is 2.5 or more and 3.2 or less.
  • the median diameter is 3 ⁇ m or less: and the like are exemplified.
  • the median diameter (D50) which is the above-mentioned "average particle diameter” can be a measured value by the following method. Measurement is performed using a laser diffraction type particle size distribution measuring device (“SALD-2200” manufactured by Shimadzu Corporation) as a measuring device and Wing SALD II as a measurement control software. A scattering type measurement mode is adopted, and a laser beam is irradiated to a wet cell in which a dispersion liquid in which a measurement sample is dispersed in a dispersion solvent circulates, and a scattered light distribution is obtained from the measurement sample. Then, the scattered light distribution is approximated by a lognormal distribution, and the particle diameter corresponding to a cumulative degree of 50% is defined as the median diameter (D50).
  • SALD-2200 laser diffraction type particle size distribution measuring device
  • Wing SALD II as a measurement control software.
  • a scattering type measurement mode is adopted, and a laser beam is irradiated to a wet cell in which a dispersion liquid in
  • the degree of graphitization P 1 of the solid graphite particles is not particularly limited, but can be generally less than 0.9 (for example, 0.5 or more and less than 0.9).
  • the graphitization degree P 1 of the solid graphite particles is, for example, 0.65 or more and 0.95 or less, typically 0.7 or more and 0.90 or less.
  • the BET specific surface area of the solid graphite particles is not particularly limited, but is, for example, 3 m 2 / g or more. By using the solid graphite particles having a large BET specific surface area as described above, the above-mentioned effects can be more exerted.
  • the BET specific surface area of the solid graphite particles is preferably 3.2 m 2 / g or more, more preferably 3.5 m 2 / g or more, and further preferably 3.7 m 2 / g or more.
  • the upper limit of the BET specific surface area of the solid graphite particles is, for example, 10 m 2 / g.
  • the BET specific surface area of the solid graphite particles is preferably 8 m 2 / g or less, more preferably 6 m 2 / g or less, and further preferably 5 m 2 / g or less.
  • the BET specific surface area of the solid graphite particles can be grasped by measuring the pore size distribution by the one-point method using nitrogen gas adsorption.
  • the R value of the solid graphite particles is not particularly limited, but can be approximately 0.25 or more (for example, 0.25 or more and 0.8 or less).
  • the "R value” is the ratio of the peak intensity of D-band to the peak intensity of G-band in the Raman spectrum (I G1) (I D1) (I D1 / I G1).
  • the R value of the solid graphite particles is, for example, 0.28 or more (for example, 0.28 or more and 0.7 or less), and typically 0.3 or more (for example, 0.3 or more and 0.6 or less). In some embodiments, the R value of the solid graphite particles may be 0.5 or less, or 0.4 or less.
  • the lower limit of the content of the solid graphite particles with respect to the total mass of the negative electrode active material is preferably 60% by mass, more preferably 70% by mass.
  • the content of the solid graphite particles with respect to the total mass of the negative electrode active material may be, for example, 80% by mass or more, or 90% by mass.
  • the capacity retention rate of the power storage element after the charge / discharge cycle at a high rate can be further increased.
  • the upper limit of the content of the solid graphite particles with respect to the total mass of the negative electrode active material may be, for example, 100% by mass.
  • the negative electrode active material layer disclosed herein may contain a carbonaceous active material other than the solid graphite particles as long as the effects of the present invention are not impaired.
  • carbonaceous active materials other than such solid graphite particles include hollow graphite particles and non-graphite carbon particles.
  • non-graphitizable carbon particles include non-graphitizable carbon and easily graphitizable carbon.
  • graphite-resistant carbon means that the average lattice spacing d (002) of the (002) plane measured by the X-ray diffraction method before charging / discharging or in the discharged state is 0.36 nm or more and 0.42 nm or less. Refers to the carbon material of.
  • the “graphitizable carbon” refers to a carbon material having d (002) of 0.34 nm or more and less than 0.36 nm.
  • a carbonaceous active material other than the solid graphite particles it is appropriate that the mass of the solid graphite particles is 50% by mass or more of the total mass of the carbonic active material contained in the negative electrode active material layer. Yes, preferably 70% by mass or more, more preferably 80% by mass or more.
  • a power storage element in which 90% by mass of the carbonaceous active material contained in the negative electrode active material layer is the solid graphite particles is preferable.
  • the negative electrode active material layer may contain a negative electrode active material made of a material other than the carbonaceous active material (hereinafter, referred to as a non-carbonaceous active material) as long as the effect of the present invention is not impaired.
  • a non-carbonaceous active material examples include metalloids such as Si, metals such as Sn, oxides thereof, or composites of these with a carbon material.
  • the content of the non-carbon active material is preferably, for example, 50% by mass or less, preferably 30% by mass or less, more preferably 30% by mass or less, based on the total mass of the negative electrode active material contained in the negative electrode active material layer. It is 10% by mass or less.
  • the content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but the lower limit thereof is preferably 50% by mass, more preferably 80% by mass, and even more preferably 90% by mass. On the other hand, as the upper limit of this content, 99% by mass is preferable, and 98% by mass is more preferable.
  • the negative electrode active material layer contains optional components such as a conductive agent, a thickener, and a filler, if necessary.
  • the solid graphite particles also have conductivity, but the conductive agent is not particularly limited as long as it is a conductive material.
  • a conductive agent include graphite other than solid graphite particles, carbonaceous materials, metals, conductive ceramics and the like.
  • the carbonaceous material include non-graphitized carbon and graphene-based carbon.
  • non-graphitized carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black.
  • Examples of carbon black include furnace black, acetylene black, and ketjen black.
  • Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), and fullerenes.
  • the shape of the conductive agent include powder and fibrous.
  • one of these materials may be used alone, or two or more of these materials may be mixed and used. Further, these materials may be used in combination.
  • a material in which carbon black and CNT are composited may be used.
  • carbon black is preferable from the viewpoint of electron conductivity and coatability, and acetylene black is particularly preferable.
  • binder examples include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, polyacrylic acid, and polyimide; ethylene-propylene-diene rubber (EPDM), Elastomers such as sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; polysaccharide polymers and the like can be mentioned.
  • fluororesins polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.
  • thermoplastic resins such as polyethylene, polypropylene, polyacrylic acid, and polyimide
  • EPDM ethylene-propylene-diene rubber
  • SBR styrene-butadiene rubber
  • fluororubber examples of the binder
  • polysaccharide polymers and the like can be mentioned.
  • the content of the binder in the negative electrode mixture layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less.
  • the thickener examples include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose.
  • CMC carboxymethyl cellulose
  • methyl cellulose examples include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose.
  • this functional group may be deactivated in advance by methylation or the like.
  • the proportion of the thickener in the entire negative electrode mixture layer can be about 8% by mass or less, and usually about 5.0% by mass or less (for example, 1.0% by mass or less). ) Is preferable.
  • the filler is not particularly limited.
  • the main components of the filler are polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide and aluminosilicate, magnesium hydroxide and hydroxide.
  • Hydroxides such as calcium and aluminum hydroxide, carbonates such as calcium carbonate, sparingly soluble ionic crystals such as calcium fluoride, barium fluoride and barium sulfate, nitrides such as aluminum nitride and silicon nitride, talc and montmorillonite, Examples thereof include mineral resource-derived substances such as boehmite, zeolite, apatite, kaolin, mulite, spinel, olivine, cericite, bentonite, and mica, or man-made products thereof.
  • the proportion of the filler in the entire negative electrode mixture layer can be about 8.0% by mass or less, and usually about 5.0% by mass or less (for example, 1.0). It is preferably mass% or less).
  • the lower limit of the negative electrode utilization rate is 0.65, preferably 0.80, and more preferably 0.85.
  • the upper limit of the negative electrode utilization rate is preferably 0.90, more preferably 0.88.
  • the negative electrode utilization rate is the ratio of the amount of electricity charged per mass of the negative electrode active material in a fully charged state to the theoretical capacity per mass of graphite.
  • the amount of electricity charged per mass of the negative electrode active material in a fully charged state shall be measured by the following procedure. (1) After the target battery is discharged to a discharged state (low SOC region), it is disassembled in the glove box. (2) In the glove box controlled to an atmosphere having an oxygen concentration of 5 ppm or less, the positive electrode and the negative electrode are taken out to assemble a small laminate cell. (3) After charging the small laminate cell to the fully charged state, constant current constant voltage (CCCV) discharge is performed at 0.01 C to the lower limit voltage when the rated capacity is obtained by the power storage element.
  • CCCV constant current constant voltage
  • the small laminate cell is disassembled, the negative electrode is taken out, and the small laminate cell in which lithium metal is arranged as the counter electrode is reassembled.
  • Additional discharge is performed at a current density of 0.01 C until the negative electrode potential reaches 2.0 V (vs. Li / Li +) to adjust the negative electrode to a completely discharged state.
  • the total amount of electricity in (3) and (5) above is divided by the mass of the negative electrode active material of the positive and negative electrode facing portions in the small laminate cell to obtain the amount of charging electricity per mass.
  • the intermediate layer is a coating layer on the surface of the negative electrode base material, and contains conductive particles such as carbon particles to reduce the contact resistance between the base material and the mixture layer.
  • the composition of the intermediate layer is not particularly limited, and can be formed by, for example, a composition containing a resin binder and conductive particles.
  • the positive electrode includes a positive electrode base material and a positive electrode mixture layer that is directly or indirectly laminated on at least one surface of the positive electrode base material.
  • the positive electrode mixture layer contains a positive electrode active material.
  • the positive electrode may include an intermediate layer arranged between the positive electrode base material and the positive electrode mixture layer.
  • the positive electrode base material is a base material having conductivity.
  • metals such as aluminum, titanium, tantalum, and stainless steel or alloys thereof are used.
  • aluminum and aluminum alloys are preferable from the viewpoint of balance of potential resistance, high conductivity and cost.
  • examples of the form of the positive electrode base material include foil, a vapor-deposited film, and the like, and foil is preferable from the viewpoint of cost. That is, aluminum foil is preferable as the positive electrode base material.
  • Examples of aluminum or aluminum alloy include A1085 and A3003 specified in JIS-H4000 (2014).
  • the positive electrode mixture layer is formed from a so-called positive electrode mixture containing a positive electrode active material.
  • a positive electrode active material for example, a known positive electrode active material can be appropriately selected.
  • a material capable of occluding and releasing lithium ions is usually used.
  • the positive electrode active material include a lithium transition metal composite oxide having an ⁇ -NaFeO type 2 crystal structure, a lithium transition metal composite oxide having a spinel type crystal structure, a polyanion compound, a chalcogen compound, sulfur and the like.
  • lithium transition metal composite oxide having an ⁇ -NaFeO type 2 crystal structure examples include Li [Li x Ni 1-x ] O 2 (0 ⁇ x ⁇ 0.5) and Li [Li x Ni ⁇ Co (1-x). - ⁇ ) ] O 2 (0 ⁇ x ⁇ 0.5, 0 ⁇ ⁇ 1), Li [Li x Co (1-x) ] O 2 (0 ⁇ x ⁇ 0.5), Li [Li x Ni ⁇ Mn (1-x- ⁇ ) ] O 2 (0 ⁇ x ⁇ 0.5, 0 ⁇ ⁇ 1), Li [Li x Ni ⁇ Mn ⁇ Co (1-x- ⁇ - ⁇ ) ] O 2 ( 0 ⁇ x ⁇ 0.5, 0 ⁇ , 0 ⁇ , 0.5 ⁇ + ⁇ ⁇ 1), Li [Li x Ni ⁇ Co ⁇ Al (1-x- ⁇ - ⁇ ) ] O 2 (0 ⁇ x Examples thereof include ⁇ 0.5, 0 ⁇ , 0 ⁇ , 0.5 ]
  • Examples of the lithium transition metal composite oxide having a spinel-type crystal structure include Li x Mn 2 O 4 , Li x Ni ⁇ Mn (2- ⁇ ) O 4 .
  • Examples of the polyanion compound include LiFePO 4 (LFP), LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , Li 3 V 2 (PO 4 ) 3 , Li 2 MnSiO 4 , Li 2 CoPO 4 F and the like.
  • Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, molybdenum dioxide and the like. The atoms or polyanions in these materials may be partially substituted with atoms or anion species consisting of other elements. The surface of these materials may be coated with other materials.
  • Li x Fe 1-z M z (PO 4 ) y (0.85 ⁇ x ⁇ 1.10, 0.95 ⁇ y ⁇ 1.05, 0 ⁇ z ⁇ 0.5, M is A polyanion compound having an olivine-type crystal structure represented by a metal other than Li and Fe (for example, lithium iron phosphate) is preferable.
  • x is preferably 0.9 or more, and may be 1.
  • z is preferably 0.3 or less, and may be 0.1 or less.
  • the M is not particularly limited as long as it is a metal other than Li and Fe, but Co, Al, Cr, Mg, Mn, Ni and Ti are preferable, and Mn is particularly preferable. Further, a part of PO 4 may be replaced with other anions such as BO 3 , SiO 4 , WO 4 , and MoO 4.
  • the growth of the coating film on the negative electrode can be a main factor of the capacity decrease after the charge / discharge cycle at a high rate. According to the power storage element, since the negative electrode active material has the above configuration, the generation of a new surface of the negative electrode active material is suppressed, and the film growth is suppressed. Therefore, in the embodiment using such a polyanion compound, the above-mentioned effects can be more exerted.
  • one of these materials may be used alone, or two or more of these materials may be mixed and used.
  • one of these compounds may be used alone, or two or more of these compounds may be mixed and used.
  • the content of the positive electrode active material in the positive electrode mixture layer is not particularly limited, but the lower limit thereof is preferably 50% by mass, more preferably 80% by mass, and even more preferably 90% by mass. On the other hand, as the upper limit of this content, 99% by mass is preferable, and 98% by mass is more preferable.
  • the amount of charging electricity per unit area of the negative electrode active material in a fully charged state is, for example, the negative electrode activity per unit area of the negative electrode active material layer with respect to the mass P of the positive electrode active material per unit area of the positive electrode active material layer. It can be adjusted by changing the ratio N / P of the mass N of the substance.
  • the positive electrode mixture contains optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary.
  • Optional components such as a conductive agent, a binder, a thickener, and a filler can be selected from the materials exemplified in the negative electrode.
  • the conductive agent is not particularly limited as long as it is a conductive material.
  • a conductive agent can be selected from the materials exemplified in the negative electrode.
  • the proportion of the conductive agent in the entire positive mixture layer can be approximately 1.0% by mass to 20% by mass, and is usually approximately 2.0% by mass to 15% by mass (for example). It is preferably 3.0% by mass to 6.0% by mass).
  • the binder can be selected from the materials exemplified in the negative electrode.
  • the proportion of the binder in the entire positive mixture layer can be approximately 0.50% by mass to 15% by mass, and is usually approximately 1.0% by mass to 10% by mass (for example, 1. It is preferably 5% by mass to 3.0% by mass).
  • the thickener examples include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose.
  • CMC carboxymethyl cellulose
  • methyl cellulose examples include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose.
  • the proportion of the thickener in the entire positive electrode mixture layer can be about 8% by mass or less, and usually about 5.0% by mass or less (for example, 1.0% by mass or less). ) Is preferable.
  • the filler can be selected from the materials exemplified in the negative electrode.
  • the proportion of the filler in the entire positive electrode mixture layer can be about 8.0% by mass or less, and usually about 5.0% by mass or less (for example, 1.0% by mass or less). It is preferable to do so.
  • the intermediate layer is a coating layer on the surface of the positive electrode base material, and contains conductive particles such as carbon particles to reduce the contact resistance between the positive electrode base material and the positive electrode mixture layer.
  • the structure of the intermediate layer is not particularly limited, and can be formed by, for example, a composition containing a resin binder and conductive particles.
  • Non-aqueous electrolyte As the non-aqueous electrolyte, a known non-aqueous electrolyte usually used for a general non-aqueous electrolyte secondary battery (storage element) can be used.
  • the non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the non-aqueous electrolyte may be a solid electrolyte or the like.
  • non-aqueous solvent a known non-aqueous solvent usually used as a non-aqueous solvent for a general non-aqueous electrolyte for a power storage element can be used.
  • the non-aqueous solvent include cyclic carbonates, chain carbonates, esters, ethers, amides, sulfones, lactones, nitriles and the like. Among these, it is preferable to use at least cyclic carbonate or chain carbonate, and it is more preferable to use cyclic carbonate and chain carbonate in combination.
  • the volume ratio of the cyclic carbonate to the chain carbonate is not particularly limited, but may be, for example, 5:95 to 50:50. preferable.
  • cyclic carbonate examples include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), and difluoroethylene.
  • EC ethylene carbonate
  • PC propylene carbonate
  • BC butylene carbonate
  • VEC vinylene carbonate
  • VEC vinylethylene carbonate
  • FEC fluoroethylene carbonate
  • difluoroethylene examples thereof include carbonate (DFEC), styrene carbonate, catechol carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, and among these, EC is preferable.
  • chain carbonate examples include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate and the like, and among these, EMC is preferable.
  • electrolyte salt a known electrolyte salt usually used as an electrolyte salt of a general non-aqueous electrolyte for a power storage element can be used.
  • electrolyte salt examples include lithium salt, sodium salt, potassium salt, magnesium salt, onium salt and the like, but lithium salt is preferable.
  • lithium salt examples include inorganic lithium salts such as LiPF 6 , LiPO 2 F 2 , LiBF 4 , LiClO 4 , LiN (SO 2 F) 2 , LiSO 3 CF 3 , LiN (SO 2 CF 3 ) 2 , and LiN (SO).
  • 2 C 2 F 5 ) 2 , LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ), LiC (SO 2 CF 3 ) 3 , LiC (SO 2 C 2 F 5 ) 3 and other hydrogens are replaced with fluorine.
  • examples thereof include a lithium salt having a fluorinated hydrocarbon group. Among these, an inorganic lithium salt is preferable, and LiPF 6 is more preferable.
  • the lower limit of the concentration of the electrolyte salt in the nonaqueous electrolyte is preferably 0.1 mol / dm 3, more preferably 0.3 mol / dm 3, more preferably 0.5mol / dm 3, 0.7mol / dm 3 Is particularly preferable.
  • the upper limit is not particularly limited, but is preferably 2.5 mol / dm 3, more preferably 2.0 mol / dm 3, more preferably 1.5 mol / dm 3.
  • non-aqueous electrolyte a molten salt at room temperature, an ionic liquid, or the like can also be used.
  • separator for example, a woven fabric, a non-woven fabric, a porous resin film, or the like is used. Among these, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of liquid retention of a non-aqueous electrolyte.
  • polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of strength, and polyimide and aramid are preferable from the viewpoint of oxidative decomposition resistance. Moreover, you may combine these resins.
  • An inorganic layer may be laminated between the separator and the electrode (usually the positive electrode).
  • This inorganic layer is a porous layer also called a heat-resistant layer or the like.
  • a separator having an inorganic layer formed on one surface or both surfaces of the porous resin film can also be used.
  • the inorganic layer is usually composed of inorganic particles and a binder, and may contain other components.
  • the shape of the power storage element of the present embodiment is not particularly limited, and examples thereof include a cylindrical battery, a pouch film type battery, a square type battery, a flat type battery, a coin type battery, and a button type battery.
  • FIG. 1 shows a square non-aqueous electrolyte secondary battery 1 as an example of a power storage element.
  • the figure is a perspective view of the inside of the battery container.
  • the electrode body 2 having the positive electrode and the negative electrode wound around the separator is housed in the square battery container 3.
  • the positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode current collector 41.
  • the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode current collector 51.
  • the method for manufacturing the power storage element can be appropriately selected from known methods.
  • a negative electrode is manufactured, a positive electrode is manufactured, a non-aqueous electrolyte is prepared, and a positive electrode and a negative electrode are laminated or wound through a separator to form an electrode body that is alternately superimposed.
  • the electrode body is housed in a battery container, and the non-aqueous electrolyte is injected into the battery container.
  • the positive electrode can be obtained by laminating the positive electrode mixture layer directly on the positive electrode base material or via an intermediate layer.
  • the positive electrode mixture layer is laminated by applying the positive electrode mixture paste to the positive electrode base material.
  • the negative electrode can be obtained by laminating the negative electrode mixture layer directly on the negative electrode base material or via an intermediate layer, similarly to the positive electrode.
  • the negative electrode mixture layer is laminated by applying a negative electrode mixture paste containing solid graphite particles to the negative electrode base material.
  • the positive electrode mixture paste and the negative electrode mixture paste may contain a dispersion medium.
  • the dispersion medium for example, an aqueous solvent such as water or a mixed solvent mainly composed of water; or an organic solvent such as N-methylpyrrolidone or toluene can be used.
  • the method of accommodating the negative electrode, the positive electrode, the non-aqueous electrolyte, etc. in the battery container can be performed by a known method. After accommodating, a power storage element can be obtained by sealing the accommodating port. Details of each element constituting the power storage element obtained by the above manufacturing method are as described above.
  • the power storage element when graphite is used as the negative electrode active material and the negative electrode utilization rate in the fully charged state of the power storage element is increased, it is possible to suppress a decrease in the capacity retention rate after the charge / discharge cycle under a high rate.
  • the power storage element of the present invention is not limited to the above embodiment, and various modifications may be made without departing from the gist of the present invention.
  • the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a well-known technique.
  • some of the configurations of certain embodiments can be deleted.
  • a well-known technique can be added to the configuration of a certain embodiment.
  • the mode in which the power storage element is a non-aqueous electrolyte secondary battery has been mainly described, but other power storage elements may be used.
  • other power storage elements include capacitors (electric double layer capacitors, lithium ion capacitors) and the like.
  • the non-aqueous electrolyte secondary battery include a lithium ion non-aqueous electrolyte secondary battery.
  • the present invention can also be realized as a power storage device including the plurality of the power storage elements.
  • the technique of the present invention may be applied to at least one power storage element included in the power storage device.
  • the power storage device includes a power storage element according to the above-described embodiment, a detection unit, and a control unit.
  • the detection unit detects the voltage between the positive electrode and the negative electrode of the power storage element.
  • a conventionally known voltmeter, voltage sensor, or the like can be used.
  • the control unit is electrically connected to the detection unit and is configured to stop charging the power storage element when the voltage detected by the detection unit is equal to or higher than a predetermined value.
  • the control unit can be composed of a computer and a computer program. Further, the control unit may be partially or wholly composed of a processor made of a semiconductor chip.
  • the potential of the positive electrode when the voltage of the power storage element is the predetermined value, the potential of the positive electrode is 4.2 V (vs. Li / Li +) or less. That is, the potential of the positive electrode when charging is stopped is 4.2 V (vs. Li / Li +) or less.
  • the potential of the positive electrode when the charging of the power storage element is stopped by the control unit is preferably 4.1 V (vs.
  • the potential of the positive electrode when charging of the power storage element is stopped by the control unit may be, for example, 3.8 V (vs. Li / Li +) or less, or 3.7 V (vs. Li +) or less. / Li + ) or less.
  • the above-mentioned effect can be more exerted.
  • an assembled battery can be constructed by using a single or a plurality of power storage elements (cells) of the present invention, and a power storage device can be further configured by using the assembled battery.
  • the power storage device can be used as a power source for automobiles such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid vehicles (PHEV). Further, the power storage device can be used for various power supply devices such as an engine starting power supply device, an auxiliary power supply device, and an uninterruptible power supply (UPS).
  • EV electric vehicles
  • HEV hybrid electric vehicles
  • PHEV plug-in hybrid vehicles
  • the power storage device can be used for various power supply devices such as an engine starting power supply device, an auxiliary power supply device, and an uninterruptible power supply (UPS).
  • UPS uninterruptible power supply
  • FIG. 2 shows an example of a power storage device 30 in which a power storage unit 20 in which two or more electrically connected power storage elements 1 are assembled is further assembled.
  • the power storage device 30 may include a bus bar (not shown) that electrically connects two or more power storage elements 1 and a bus bar (not shown) that electrically connects two or more power storage units 20.
  • the power storage unit 20 or the power storage device 30 may include a condition monitoring device (not shown) for monitoring the state of one or more power storage elements.
  • Example 1 (Preparation of negative electrode) Bulk solid graphite particles with an aspect ratio of 3.0, an average particle size (D 50 ) of 3.0 ⁇ m, and a BET specific surface area of 3.9 m 2 / g, which are negative electrode active materials, and styrene-butadiene rubber, which is a binder ( SBR), carboxymethyl cellulose (CMC) as a thickener, and water as a dispersion medium were mixed to prepare a negative electrode mixture paste.
  • SBR binder
  • CMC carboxymethyl cellulose
  • the mass ratio of the solid graphite particles, the binder and the thickener was 96: 3: 1 in terms of solid content.
  • the actual charge capacity per mass of the solid graphite particles (the maximum chargeable capacity that the active material can actually reversibly store) was 335 mAh / g.
  • the negative electrode mixture paste was prepared by adjusting the viscosity with the amount of water and kneading with a multi-blender mill. This negative electrode mixture paste was applied to both sides of the negative electrode base material so that a non-laminated portion was formed on one end edge of the copper foil as the negative electrode base material, and dried to prepare a negative electrode active material layer.
  • the coating amount of the negative electrode mixture (the dispersion medium evaporated from the negative electrode mixture paste) per unit area on one side after drying was adjusted to 4.82 mg / cm 2 . After the above drying, the negative electrode active material layer was pressed with a roll press machine so as to have a predetermined packing density to obtain a negative electrode.
  • a positive electrode using LiFePO 4 (LFP) as a positive electrode active material was prepared.
  • a positive electrode mixture paste containing the above positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and acetylene black as a conductive agent and using N-methylpyrrolidone (NMP) as a dispersion medium was prepared. ..
  • the mass ratio of the positive electrode active material, the binder, and the conductive agent was 91: 4: 5 in terms of solid content.
  • This positive electrode mixture paste was applied to both sides of the positive electrode base material so that a non-laminated portion was formed on one end edge of the positive electrode base material, dried, and pressed to form a positive electrode active material layer.
  • the coating amount of the positive electrode mixture (the dispersion medium evaporated from the positive electrode mixture paste) per unit area on one side after drying was adjusted to 9.34 mg / cm 2 .
  • An aluminum foil having a thickness of 15 ⁇ m was used as the positive electrode base material.
  • an intermediate layer was arranged on the surface of the positive electrode base material.
  • the intermediate layer is for the intermediate layer by kneading N-methylpyrrolidone (NMP) as a solvent, acetylene black as a conductive auxiliary agent, hydroxyethyl chitosan as a binder, and pyromellitic acid as a cross-linking agent.
  • NMP N-methylpyrrolidone
  • acetylene black as a conductive auxiliary agent
  • hydroxyethyl chitosan as a binder
  • pyromellitic acid as a cross-linking agent.
  • I made a paste.
  • the mass ratio of the conductive auxiliary agent, the binder, and the cross-linking agent was 1: 1: 1 in terms of solid content.
  • This paste for the intermediate layer was applied to both sides of the positive electrode base material by a gravure coating machine so that the coating amount of the intermediate layer per unit area after drying was 0.05 mg / cm 2, and dried. ..
  • Non-aqueous electrolyte The non-aqueous electrolyte is prepared by dissolving LiPF 6 having a salt concentration of 1.2 mol / dm 3 in a solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 30:35:35. And prepared.
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • Separator A polyethylene microporous membrane having a thickness of 15 ⁇ m was used as the separator.
  • the positive electrode, the negative electrode, and the separator were laminated to prepare an electrode body. Then, the non-laminated portion of the positive electrode base material and the non-laminated portion of the negative electrode base material were welded to the positive electrode current collector and the negative electrode current collector, respectively, and sealed in the battery container. Next, after welding the battery container and the lid plate, the non-aqueous electrolyte was injected and sealed. In this way, the batteries (storage elements) of Examples 1 to 6 and Comparative Example 1 to Comparative Example 10 were obtained. The design rated capacity of this battery is 8.0 Ah.
  • Examples 2 to 6 and Comparative Examples 1 to 10 A power storage element was obtained in the same manner as in Example 1 except that the structure of the negative electrode active material, the aspect ratio, the average particle size (D 50), and the coating amount of the negative electrode mixture were as shown in Table 1.
  • This operation was performed three times, and the discharge capacity confirmed the third time was defined as the discharge capacity after the charge / discharge cycle integration time of 300 hours.
  • the percentage of the discharge capacity after the charge / discharge cycle integration time of 300 hours with respect to the initial discharge capacity was calculated and used as the “capacity retention rate [%] after the charge / discharge cycle integration time of 300 hours”.
  • Table 1 below shows the negative electrode utilization rate of each power storage element and the capacity retention rate after 300 hours of charge / discharge cycle integration time.
  • Examples 1 to 8 contain a negative electrode active material containing solid graphite particles having a negative electrode utilization rate of 0.65 or more and an aspect ratio of 1 or more and 5 or less as a main component. No. 6 had a good effect of suppressing a decrease in the capacity retention rate after the charge / discharge cycle.
  • Comparative Examples 7 to 9 containing a negative electrode active material containing solid graphite particles as a main component the capacity retention rate after the charge / discharge cycle was significantly reduced.
  • Comparative Example 10 when the negative electrode utilization rate is less than 0.65, the negative electrode active material containing hollow graphite particles as a main component and the aspect ratio are more than 5.
  • the power storage element uses specific solid graphite particles as the negative electrode active material, and the capacity retention rate after the charge / discharge cycle at a high rate, which is a problem when the negative electrode utilization rate satisfies 0.65 or more. It can be seen that the decrease in the amount of
  • the power storage element can suppress a decrease in the capacity retention rate after a charge / discharge cycle at a high rate when graphite is used as the active material of the negative electrode and the negative electrode utilization rate is increased.
  • the present invention is a non-aqueous electrolyte power storage element such as a non-aqueous electrolyte secondary battery used as a power source that requires rapid charging of electronic devices such as personal computers and communication terminals, and automobiles such as EVs, HEVs, and PHEVs. It is preferably used as.
  • a large lithium ion secondary battery can be mentioned as a preferred application target of the present invention. For example, it may be used in a charge / discharge cycle including a high-rate discharge of 3C or more (for example, 3C to 50C) and a large capacity type having a battery capacity of 5.0Ah or more (for example, 5.0Ah or more and 100Ah or less).
  • An example is an assumed large lithium ion secondary battery.
  • the non-aqueous electrolyte power storage element according to the present invention can be suitably applied to the above-mentioned large-sized lithium ion secondary battery because the decrease in the capacity retention rate after the charge / discharge cycle at a high rate is suppressed.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Power Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)
PCT/JP2021/009403 2020-03-11 2021-03-10 蓄電素子 Ceased WO2021182488A1 (ja)

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US17/910,456 US20230163302A1 (en) 2020-03-11 2021-03-10 Energy storage device
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EP4539167A4 (en) * 2022-08-01 2025-11-05 Gs Yuasa Int Ltd NON-AQUEOUS ELECTROLYTE ENERGY STORAGE ELEMENT

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EP4539167A4 (en) * 2022-08-01 2025-11-05 Gs Yuasa Int Ltd NON-AQUEOUS ELECTROLYTE ENERGY STORAGE ELEMENT

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