WO2019111644A1 - Secondary battery - Google Patents

Secondary battery Download PDF

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Publication number
WO2019111644A1
WO2019111644A1 PCT/JP2018/041908 JP2018041908W WO2019111644A1 WO 2019111644 A1 WO2019111644 A1 WO 2019111644A1 JP 2018041908 W JP2018041908 W JP 2018041908W WO 2019111644 A1 WO2019111644 A1 WO 2019111644A1
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WO
WIPO (PCT)
Prior art keywords
negative electrode
positive electrode
secondary battery
capacity
mah
Prior art date
Application number
PCT/JP2018/041908
Other languages
French (fr)
Japanese (ja)
Inventor
貴宏 相馬
八木　陽心
Original Assignee
日立オートモティブシステムズ株式会社
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Publication of WO2019111644A1 publication Critical patent/WO2019111644A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/574—Devices or arrangements for the interruption of current
    • 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
    • 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
    • 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
    • H01M4/133—Electrodes based on 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
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 secondary battery.
  • lithium ion batteries are used as secondary batteries in electric vehicles and hybrid vehicles.
  • Such secondary batteries are required to have high output, high energy density and safety.
  • it is necessary to prevent the safety of the battery system from being impaired even if the secondary battery is overcharged due to an erroneous operation or the like. Therefore, in order to ensure safety in the event of overcharging, a secondary battery is provided with a current interrupting mechanism.
  • Patent Document 1 describes a battery system in which lithium carbonate is contained in a positive electrode mixture as a gas generating agent, and lithium carbonate generates a decomposition gas to operate a current interrupting mechanism when overcharged.
  • Patent Document 1 does not specify the charge capacity of the negative electrode up to the potential at which a decomposition gas is generated at the time of overcharge. For example, when the charge capacity of the negative electrode is small before reaching the reaction potential of the gas generating agent in the overcharged state, lithium is deposited on the surface of the negative electrode, and breaks through the separator separating the positive and negative electrodes, There is a possibility that the secondary battery may be damaged due to a short circuit between the positive and negative electrodes.
  • the battery container accommodating the positive electrode and the negative electrode, and the internal pressure of the battery container reach a predetermined operating pressure
  • a current blocking mechanism for interrupting a current flowing between the positive electrode and the negative electrode, wherein the positive electrode mixture contains a gas generating agent, and the potential of the positive electrode is the secondary battery.
  • the capacity until the reaction potential of the gas generating agent is exceeded by exceeding the charge termination voltage of the battery is more than the capacity until the potential of the negative electrode exceeds the charge termination voltage of the secondary battery and reaches the charge termination voltage of the negative electrode. I made it smaller.
  • a secondary battery excellent in overcharge safety can be provided.
  • FIG. 1 is a longitudinal sectional view of a cylindrical secondary battery 1.
  • the cylindrical secondary battery 1 has dimensions of, for example, an outer diameter of 40 mm and a height of 100 mm.
  • the cylindrical secondary battery 1 is configured such that the power generation unit 20 is accommodated inside a bottomed cylindrical battery can 60 whose opening is sealed by a sealing lid 50. First, the battery can 60 and the power generation unit 20 will be described, and next, the sealing lid 50 will be described.
  • a caulking portion 61 is formed at the can opening end (upper side in the figure).
  • the caulking portion 61 includes a bent portion 62 formed by bending the can open end inward, and a grooving portion 63 protruding inward at a predetermined distance on the battery bottom side.
  • the sealing lid 50 is crimped and fixed by interposing the gasket 43 between the bent portion 62 and the grooving portion 63, and the cylindrical secondary battery 1 is sealed.
  • the power generation unit 20 is integrally configured by unitizing the electrode group 10, the positive electrode current collecting member 31, and the negative electrode current collecting member 21 as described below.
  • the electrode group 10 has an axial core 15 at the central portion, and a positive electrode, a negative electrode and a separator are wound around the axial core 15.
  • the hollow cylindrical shaft core 15 has a large diameter recess 15a formed on the inner surface of the upper end in the axial direction (vertical direction in the drawing), and the positive electrode current collector 31 is press-fitted into the recess 15a.
  • the positive electrode current collecting member 31 is made of, for example, aluminum, and a disk-like base 31a, a lower cylindrical portion 31b which protrudes toward the shaft core 15 at the inner peripheral portion of the base 31a and is pressed into the inner surface of the shaft core 15. And an upper cylindrical portion 31 c protruding toward the sealing lid 50 at the outer peripheral edge.
  • the base 31 a of the positive electrode current collecting member 31 is formed with an opening 31 d for releasing a decomposition gas generated inside the battery at the time of overcharging.
  • the positive electrode leads 16 of the positive electrode sheet 11 a described in detail later with reference to FIG. 3 are all welded to the upper cylindrical portion 31 c of the positive electrode current collecting member 31.
  • the positive electrode lead 16 is overlapped and joined onto the upper cylindrical portion 31 c of the positive electrode current collecting member 31. Since each positive electrode lead 16 is very thin, one can not take out a large current. For this reason, a large number of positive electrode leads 16 are formed at predetermined intervals over the entire length from the winding start to the winding end on the shaft core 15.
  • the positive electrode lead 16 of the positive electrode sheet 11 a and the ring-shaped pressing member 32 are welded to the outer periphery of the upper cylindrical portion 31 c of the positive electrode current collecting member 31.
  • the large number of positive electrode leads 16 are in close contact with the outer periphery of the upper cylindrical portion 31c of the positive electrode current collecting member 31, and the pressing member 32 is wound around the outer periphery of the positive electrode lead 16 and temporarily fixed.
  • the positive electrode current collecting member 31 Since the positive electrode current collecting member 31 is oxidized by the electrolytic solution, the reliability can be improved by forming it with aluminum. As soon as the surface is exposed by processing, aluminum forms an aluminum oxide film on the surface, and this aluminum oxide film can prevent oxidation by the electrolytic solution. Further, by forming the positive electrode current collecting member 31 of aluminum, it is possible to weld the positive electrode lead 16 of the positive electrode sheet 11a by ultrasonic welding, spot welding or the like.
  • a stepped portion 15 b whose outer diameter is reduced in diameter is formed on the outer periphery of the lower end portion of the shaft core 15, and the negative electrode current collecting member 21 is press-fitted and fixed to the stepped portion 15 b.
  • the negative electrode current collecting member 21 is formed of, for example, copper, and an opening 21b which is press-fit into the step 15b of the shaft core 15 is formed in the disk-shaped base 21a.
  • An outer peripheral tubular portion 21c is formed to protrude.
  • the negative electrode leads 17 of the negative electrode sheet 12a described in detail in FIG. 3 to be described later are all welded to the outer peripheral cylindrical portion 21c of the negative electrode current collecting member 21 by ultrasonic welding or the like. Since each negative electrode lead 17 is very thin, many are formed at predetermined intervals over the entire length from the winding start to the winding end to the shaft core 15 in order to take out a large current.
  • the negative electrode lead 17 of the negative electrode sheet 12 a and the ring-shaped pressing member 22 are welded to the outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting member 21.
  • the large number of negative electrode leads 17 are in close contact with the outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting member 21, and the pressing member 22 is wound around and temporarily fixed to the outer periphery of the negative electrode lead 17.
  • a copper negative electrode current supply lead 23 is welded to the lower surface of the negative electrode current collector 21.
  • the negative electrode current supply lead 23 is welded to the battery can 60 at the bottom of the battery can 60.
  • the battery can 60 is formed, for example, of carbon steel with a thickness of 0.5 mm, and the surface is plated with nickel. By using such a material, the negative electrode current supply lead 23 can be welded to the battery can 60 by resistance welding or the like.
  • a flexible positive electrode conductive lead 33 formed by laminating a plurality of aluminum foils is welded to one end of the upper surface of the base portion 31 a of the positive electrode current collector 31 by welding.
  • the positive electrode conductive lead 33 is made possible to flow a large current by laminating and integrating a plurality of aluminum foils, and is given flexibility. That is, in order to flow a large current, it is necessary to increase the thickness of the connecting member, but if it is formed of a single metal plate, the rigidity is increased and the flexibility is impaired. Therefore, a large number of thin aluminum foils are laminated to give flexibility.
  • the thickness of the positive electrode conductive lead 33 is, for example, about 0.5 mm, and is formed by laminating five aluminum foils each having a thickness of 0.1 mm.
  • FIG. 2 is an exploded perspective view of the cylindrical secondary battery shown in FIG.
  • the electrode group 10 has an axial core 15 (see FIG. 1) at the center, and a positive electrode, a negative electrode and a separator are wound around the axial core 15. Then, the outermost first separator 13 is stopped by the adhesive tape 19.
  • the sealing lid 50 is provided with a cap 3 having an exhaust port 3c, a cap case 37 mounted on the cap 3 and having a cleavage groove 37a, a positive electrode connection plate 35 spot-welded to the back of a central portion of the cap case 37, a positive electrode connection plate It comprises an insulating ring 41 sandwiched between the peripheral upper surface of 35 and the back surface of the cap case 37, and is assembled in advance as a subassembly.
  • the cap 3 is formed by applying nickel plating to iron such as carbon steel.
  • the cap 3 has a disk-like peripheral portion 3a and a headless, bottomed cylindrical portion 3b projecting upward from the peripheral portion 3a, and has a hat-like shape as a whole.
  • An exhaust port 3c is formed at the center of the cylindrical portion 3b.
  • the cylindrical portion 3b functions as a positive electrode external terminal, and a bus bar or the like is connected.
  • the peripheral portion of the cap 3 is integrated by a folded flange 37 b of a cap case 37 formed of an aluminum alloy. That is, the peripheral edge of the cap case 37 is folded back along the upper surface of the cap 3 and the cap 3 is fixed by caulking.
  • the annular ring folded back on the upper surface of the cap 3, that is, the flange 37b and the cap 3 are friction welded and welded. That is, the cap case 37 and the cap 3 are integrated by caulking and fixing by the flange 37 b and welding.
  • the sealing lid 50 is provided with the flange 50F in which the cap case 37 and the cap 3 are integrated.
  • a circular cleavage groove 37a and a cleavage groove 37a radially extending in four directions from the circular cleavage groove 37a are formed.
  • the cleavage groove 37a is formed by pressing the upper surface side of the cap case 37 into a V-shape by a press and making the remaining portion thin.
  • the cleavage groove 37a is cleaved when the internal pressure in the battery can 60 rises to a predetermined value or more, and the decomposition gas inside is released.
  • the sealing lid 50 constitutes a current blocking mechanism.
  • a crack is generated in the cap case 37 in the cleavage groove 37a, and the inside decomposition gas is discharged from the exhaust port 3c of the cap 3. It is discharged and the pressure in the battery can 60 is reduced.
  • the cap case 37 called a cap case bulges out of the container due to the internal pressure of the battery can 60, and the electrical connection with the positive electrode connection plate 35 is cut off, thereby securing safety in the case of overcharging.
  • the safety against overcharge is improved by providing a sufficient capacity in the negative electrode even at the potential at which the gas generating agent reacts at the time of overcharge, but the details will be described. Will be described later.
  • the sealing lid 50 is placed on the upper cylindrical portion 31 c of the positive electrode current collecting member 31 in an insulating state. That is, the cap case 37 in which the cap 3 is integrated is mounted on the upper end surface of the positive electrode current collecting member 31 in an insulating state via the insulating ring 41. However, the cap case 37 is electrically connected to the positive electrode current collecting member 31 by the positive electrode conductive lead 33, and the cap 3 of the sealing lid 50 becomes the positive electrode of the battery 1.
  • the insulating ring 41 has an opening 41 a and a side 41 b projecting downward. A connection plate 35 is fitted in the opening 41 a of the insulating ring 41.
  • connection plate 35 is formed of an aluminum alloy, has a substantially dish shape that is substantially uniform throughout substantially except for the central portion and bent to a slightly lower position on the central side.
  • the thickness of the connection plate 35 is, for example, about 1 mm.
  • a thin and dome-shaped protrusion 35 a is formed at the center of the connection plate 35, and a plurality of openings 35 b are formed around the protrusion 35 a.
  • the opening 35 b has a function of releasing the gas generated inside the battery.
  • the protrusion 35 a of the connection plate 35 is joined to the bottom surface of the central portion of the cap case 37 by resistance welding or friction diffusion bonding.
  • the electrode assembly 10 is housed in the battery can 60, and the sealing lid 50, which is manufactured in advance as a partial assembly, is electrically connected by the positive electrode current collecting member 31 and the positive electrode conductive lead 33 and placed on the cylinder upper part.
  • the outer peripheral wall 43b of the gasket 43 is bent by a press or the like, and the sealing lid 50 is crimped so as to be pressed in the axial direction by the base 43a and the outer peripheral wall 43b. Thereby, the sealing lid 50 is fixed to the battery can 60 via the gasket 43.
  • the gasket 43 is initially formed on the peripheral side edge of the ring-shaped base portion 43a so that the outer peripheral wall portion 43b is substantially vertically erected upward, and the inner peripheral side is substantially downward from the base portion 43a It has a shape having a cylindrical portion 43c vertically suspended.
  • a predetermined amount of non-aqueous electrolytic solution is injected into the inside of the battery can 60.
  • the non-aqueous electrolytic solution it is preferable to use a solution in which a lithium salt is dissolved in a carbonate-based solvent.
  • lithium salts include lithium fluorophosphate (LiPF6), lithium fluoroborate (LiBF6), and the like.
  • the carbonate-based solvent ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl ethyl carbonate (MEC), or a mixture of solvents selected from one or more of the above solvents, Can be mentioned.
  • FIG. 3 is a view showing a power generation unit of the cylindrical secondary battery 1.
  • the detail of the structure of the electrode group 10 is shown, and the perspective view of the state which cut
  • the electrode group 10 has a configuration in which the positive electrode 11, the negative electrode 12, and the first and second separators 13 and 14 are wound around the outer periphery of the shaft core 15.
  • the first separator 13 is wound around the innermost periphery in contact with the outer periphery of the shaft core 15, and the negative electrode 12, the second separator 14 and the positive electrode 11 are laminated in this order on the outside It has been rolled up.
  • a first separator 13 and a second separator 14 are wound several turns inside the innermost negative electrode 12.
  • the outermost periphery is a negative electrode 12 and a first separator 13 wound around the outer periphery.
  • the positive electrode 11 is formed of aluminum foil and has a long shape, and includes a positive electrode sheet 11 a and a positive electrode processing portion in which a positive electrode mixture 11 b is applied to both surfaces of the positive electrode sheet 11 a.
  • the upper side edge along the longitudinal direction of the positive electrode sheet 11a is a positive electrode mixture non-treated portion 11c in which the positive electrode mixture 11b is not applied and the aluminum foil is exposed.
  • a large number of positive electrode leads 16 projecting upward in parallel with the shaft core 15 are integrally formed at equal intervals.
  • the positive electrode mixture 11 b is composed of a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a positive electrode gas generating compound (gas generating agent).
  • the positive electrode conductive material is not limited as long as it can assist the transfer of electrons generated by the lithium storage and release reaction in the positive electrode mixture to the positive electrode.
  • the positive electrode conductive material include graphite and acetylene black.
  • the positive electrode binder can bind the positive electrode active material to the positive electrode conductive material and can bind the positive electrode mixture to the positive electrode current collector, unless it is significantly degraded by contact with the non-aqueous electrolyte.
  • the positive electrode binder include polyvinylidene fluoride (PVDF) and fluororubber.
  • Examples of the positive electrode gas generating compound include a carbonic acid inorganic compound, an oxalic acid inorganic compound, and a nitric acid inorganic compound which generate gas at the positive electrode potential in the overcharged state.
  • inorganic carbonated compounds are preferable, and examples thereof include lithium carbonate.
  • the method of forming the positive electrode mixture layer is not limited as long as the positive electrode mixture is formed on the positive electrode.
  • a method of applying a dispersion solution of the constituent material of the positive electrode mixture 11b on the positive electrode sheet 11a can be mentioned.
  • Examples of a method of applying the positive electrode mixture 11b to the positive electrode sheet 11a include a roll coating method, a slit die coating method, and the like. N-methyl pyrrolidone (NMP), water or the like is added to the positive electrode mixture 11b as a solvent example of the dispersion solution, and a kneaded slurry is uniformly coated on both sides of a 20 ⁇ m thick aluminum foil and dried. Press and cut. An example of the coating thickness of the positive electrode mixture 11 b is about 40 ⁇ m on one side. When cutting the positive electrode sheet 11a, the positive electrode lead 16 is integrally formed.
  • NMP N-methyl pyrrolidone
  • water or the like is added to the positive electrode mixture 11b as a solvent example of the dispersion solution, and a kneaded slurry is uniformly coated on both sides of a 20 ⁇ m thick aluminum foil and dried. Press and cut.
  • An example of the coating thickness of the positive electrode mixture 11 b is about 40 ⁇ m on
  • the negative electrode 12 is formed of a copper foil and has a long shape, and has a negative electrode sheet 12a and a negative electrode processing portion in which a negative electrode mixture 12b is applied to both surfaces of the negative electrode sheet 12a.
  • the lower side edge along the longitudinal direction of the negative electrode sheet 12 a is a negative electrode mixture non-treated portion 12 c in which the negative electrode mixture 12 b is not applied and the copper foil is exposed.
  • a large number of negative electrode leads 17 extending in the opposite direction to the positive electrode lead 16 are integrally formed at equal intervals.
  • the negative electrode mixture 12 b is composed of a negative electrode active material, a negative electrode binder, and a thickener. By using graphite carbon as the negative electrode active material, a lithium ion secondary battery for a plug-in hybrid car or an electric car that requires a large capacity can be manufactured.
  • the method of forming the negative electrode mixture 12b is not limited as long as the negative electrode mixture 12b is formed on the negative electrode sheet 12a.
  • coating the negative mix 12b to the negative electrode sheet 12a the method of apply
  • a slurry obtained by adding N-methyl-2-pyrrolidone or water as a dispersion solvent to the negative electrode mixture 12b and kneading the mixture is used to form a rolled copper foil having a thickness of 10 ⁇ m. After applying uniformly on both sides and drying, it is pressed and cut.
  • An example of the coating thickness of the negative electrode mixture 12 b is about 40 ⁇ m on one side.
  • the width of the first separator 13 and the second separator 14 is WS
  • the width of the negative electrode mixture 12b formed on the negative electrode sheet 12a is WC
  • the width of the positive electrode mixture 11b formed on the positive electrode sheet 11a is WA
  • the width WC of the negative electrode mixture 12b is always larger than the width WA of the positive electrode mixture 11b. This is because in the case of a lithium ion secondary battery, lithium, which is a positive electrode active material, is ionized to permeate the separator, but when the negative electrode active material is not formed on the negative electrode side and the negative electrode sheet 12a is exposed, the negative electrode sheet It is because lithium precipitates on 12a and causes an internal short circuit.
  • FIG. 4 is an external perspective view of the prismatic secondary battery 100.
  • the prismatic secondary battery 100 includes a battery case including a battery can 101 and a battery cover 102.
  • the material of the battery can 101 and the battery cover 102 is aluminum or an aluminum alloy.
  • the battery can 101 is formed in a flat rectangular box shape whose one end is opened by deep drawing.
  • the battery can 101 has a rectangular flat bottom plate 101c, a pair of wide side plates 101a rising from each of a pair of long sides of the bottom plate 101c, and a pair of narrow side plates 101b rising from each of a pair of short sides of the bottom plate 101c. And.
  • FIG. 5 is an exploded perspective view of the prismatic secondary battery 100.
  • a wound electrode group 170 (see FIG. 6) is accommodated in the battery can 101.
  • the positive electrode current collector 180 joined to the positive electrode 174 of the wound electrode group 170 and the negative electrode 175 of the wound electrode group 170 are joined.
  • the insulating sheet 108 a covering the central portion of the wound electrode group 170 and the insulating sheet 108 b covering the positive electrode uncoated portion of the wound electrode group 170 and the wound electrode group 170.
  • the material of the insulating sheets 108a, 108b and 108c is a resin having an insulating property such as polypropylene, and the battery can 101 and the wound electrode group 170 are electrically insulated.
  • the battery cover 102 has a rectangular flat plate shape and is laser welded so as to close the opening of the battery can 101. That is, the battery cover 102 seals the opening of the battery can 101.
  • the battery lid 102 is provided with a positive electrode external terminal 104 and a negative electrode external terminal 105 electrically connected to the positive electrode 174 and the negative electrode 175 of the wound electrode group 170.
  • the positive electrode external terminal 104 is electrically connected to the positive electrode 174 (see FIG. 6) of the wound electrode group 170 via the current blocking mechanism 181 and the positive electrode current collector 180. Are electrically connected to the negative electrode 175 of the wound electrode group 170 via the negative electrode current collector 190. Therefore, power is supplied to the external device through the positive electrode external terminal 104 and the negative electrode external terminal 105, or externally generated power is supplied to the wound electrode group 170 through the positive electrode external terminal 104 and the negative electrode external terminal 105. Be charged.
  • a liquid injection hole 106 a for injecting an electrolytic solution into the battery case is formed in the battery cover 102.
  • the injection hole 106 a is sealed by the injection plug 106 b after the injection of the electrolyte.
  • the electrolytic solution for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF6) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.
  • the battery cover 102 is provided with a gas discharge valve 103.
  • the gas discharge valve 103 is formed by partially thinning the battery cover 102 by press processing.
  • the thin film member may be attached to the opening of the battery cover 102 by laser welding or the like, and the thin portion may be used as the gas discharge valve.
  • the gas discharge valve 103 generates heat by generating heat due to an abnormality such as an internal short circuit in the prismatic secondary battery 100, and when the pressure in the battery container rises and reaches a predetermined pressure, it is cleaved and the gas is generated from the inside By discharging, the pressure in the battery container is reduced.
  • the current interrupting mechanism 181 operates when the prismatic secondary battery 100 is overcharged and the positive electrode gas generating compound is decomposed by the positive electrode potential at that time to generate a decomposed gas and raise the internal pressure. Then, the electrical connection with the positive electrode external terminal 104 is cut off, and safety is ensured when the battery is overcharged.
  • the safety against overcharge is improved by providing a sufficient capacity in the negative electrode even at the potential at which the gas generating agent reacts at the time of overcharge, but the details will be described. Will be described later.
  • FIG. 6 is a perspective view showing a wound electrode group 170 of a square secondary battery.
  • FIG. 6 shows a state in which the winding end side of the wound electrode group 170 is developed.
  • the wound electrode group 170 which is a power generation element, has a laminated structure by winding the long positive electrode 174 and the negative electrode 175 in a flat shape around the winding central axis W with the separators 173a and 173b interposed. ing.
  • the positive electrode 174 is formed by forming a positive electrode mixture layer 176 on both surfaces of the positive electrode foil 171.
  • the positive electrode mixture is a mixture of a positive electrode active material, a positive electrode conductive agent, a binder (positive electrode binder), and a positive electrode gas generating compound.
  • the positive electrode gas generating compound include a carbonic acid inorganic compound, an oxalic acid inorganic compound, and a nitric acid inorganic compound that generate gas at the positive electrode potential in the overcharged state.
  • inorganic carbonated compounds are preferable, and examples thereof include lithium carbonate.
  • the negative electrode 175 has a negative electrode mixture layer 177 formed on both sides of the negative electrode foil 172.
  • the negative electrode mixture is a mixture of a negative electrode active material, a binder (negative electrode binder), and a thickener.
  • the positive electrode foil 171 is an aluminum foil having a thickness of about 20 to 30 ⁇ m
  • the negative electrode foil 172 is a copper foil having a thickness of about 15 to 20 ⁇ m.
  • the material of the separators 173a and 173b is a microporous polyethylene resin through which lithium ions can pass.
  • the positive electrode active material is a lithium-containing transition metal double oxide such as lithium manganate
  • the negative electrode active material is a carbon material such as graphite capable of reversibly absorbing and desorbing lithium ions.
  • the wound electrode group 170 In the width direction of the wound electrode group 170, that is, both ends in the direction of the wound central axis W orthogonal to the winding direction, one is a laminated portion of the positive electrode 174 and the other is a laminated portion of the negative electrode 175 There is.
  • the laminated portion of the positive electrode 174 provided at one end is obtained by laminating the positive uncoated portion on which the positive electrode mixture layer 176 is not formed, that is, the exposed portion of the positive electrode foil 171.
  • the laminated portion of the negative electrode 175 provided at the other end is obtained by laminating the uncoated portion of the negative electrode where the negative electrode mixture layer 177 is not formed, that is, the exposed portion of the negative electrode foil 172.
  • the laminated portion of the positive electrode uncoated portion and the laminated portion of the negative electrode uncoated portion are respectively crushed in advance, and connected to the positive electrode current collector 180 and the negative electrode current collector 190 by ultrasonic bonding.
  • the above-described cylindrical secondary battery and prismatic secondary battery are sealed non-aqueous electrolyte secondary batteries.
  • the secondary battery comprises a positive electrode having a positive electrode mixture layer, a negative electrode having a negative electrode mixture layer, and a non-aqueous electrolyte to which a gas generating agent is added that generates a decomposition gas when the battery voltage exceeds a predetermined voltage.
  • a current blocking mechanism that is accommodated in the battery case and that operates when the pressure in the battery case rises with the generation of decomposition gas during overcharge.
  • Lithium carbonate is contained in the positive electrode as a gas generating agent.
  • the gas generating agent reacts at the time of overcharge, lithium is precipitated on the surface of the negative electrode
  • the separator may be broken, and the positive and negative electrodes may be short-circuited to damage the secondary battery.
  • the amount of the gas generating agent to be added is too small, the amount of gas generation at the time of overcharging may be small, and the current interruption mechanism may not operate properly.
  • too much emphasis is placed on the reliability of the current blocking mechanism, and if the gas generating agent is excessively added, the performance of the secondary battery is degraded. This is because the gas generating agent does not contribute to the charge / discharge reaction in the voltage range originally used, and becomes a resistance component of the secondary battery.
  • the overcharge negative electrode capacity is set larger than the overcharge capacity until the gas generating agent (positive electrode gas generating compound) reacts during overcharge and the current interruption mechanism operates.
  • the gas generating agent positive electrode gas generating compound
  • the secondary battery in the present embodiment does not add an excessive amount of the gas generating agent, because the negative electrode can sufficiently secure the charge capacity until the gas generating agent reacts and the current blocking mechanism operates. Does not reduce the performance of the secondary battery.
  • FIG. 7 is a graph showing the relationship between the potential and the capacity of the secondary battery in the present embodiment.
  • the vertical axis indicates the positive electrode and negative electrode potential (V) and the battery voltage (V) of the secondary battery
  • the horizontal axis indicates the capacity (mAh).
  • the dotted line indicated by a1 in FIG. 7 indicates the change of the negative electrode initial charge capacity Qnc, and the solid line indicated by a2 indicates the change of the negative electrode initial discharge capacity Qnd.
  • the change in negative electrode initial charge capacity Qnc shown in a1 in the figure gradually charges the negative electrode from less than 0% of SOC, further charges it more than 0% of SOC, and further charges it more than 100% of SOC to react the gas generating agent
  • the case where it charges until it exceeds electric potential is shown.
  • 0.2 C C is the capacity rate, and the relative ratio of the discharge current value to the battery capacity) until the potential with respect to lithium metal falls from 1.6 V to 0.005 V (negative charge termination voltage)
  • the negative electrode is set to a charge capacity exceeding the reaction potential of the gas generating agent.
  • the overcharge negative electrode capacity Qnoc of the negative electrode is set larger than the overcharge capacity Qcoc of the secondary battery.
  • the change in the negative electrode initial discharge capacity Qnd shown in a2 of FIG. 7 shows the case where the negative electrode is gradually discharged from the charge capacity exceeding the reaction potential of the gas generating agent to 100% SOC and discharged to SOC 0%. Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 0.005 V to 1.6 V (discharge termination voltage of the negative electrode).
  • the negative electrode irreversible capacity Qnf is a capacity obtained by subtracting the initial capacity of the negative electrode first discharge capacity Qnd from the initial capacity of the negative electrode initial charge capacity Qnc.
  • the negative electrode irreversible capacity Qnf is a difference between the amount of electricity consumed for forming a solid. State interphase (SEI) film on the surface of the negative electrode at the time of initial charge and the amount of electricity trapped in the crystal structure and unable to be discharged.
  • SEI State interphase
  • the negative electrode reversible capacity Qnk is a capacity obtained by subtracting the negative electrode irreversible capacity Qnf from the capacity exceeding the reaction potential of the gas generating agent.
  • the charge termination voltage of the negative electrode is preferably 0.005 V or more and 0.010 V or less based on lithium metal.
  • the discharge termination voltage of the negative electrode is preferably 1.5 V or more and 1.6 V or less based on lithium metal.
  • the dotted line indicated by b1 in FIG. 7 represents a change in positive electrode initial charge capacity Qpc
  • the solid line indicated by b2 represents a change in positive electrode initial discharge capacity Qpd.
  • the change of the positive electrode initial charge capacity Qpc indicated by b1 in the figure indicates the case where the positive electrode is gradually charged from less than 0% of SOC, charged to more than 0% of SOC, and charged to a potential of 4.3V at 100% of SOC. Specifically, constant current charging is performed with a current of 0.2 C until the potential with respect to lithium metal becomes 4.3 V (positive electrode charge termination voltage) corresponding to 3.0 V to SOC 100%, and then 4.3 V After reaching a voltage of 2, charge for 2 hours with a constant voltage of 4.3V.
  • the dotted line indicates the case where the SOC is further charged up to 100% and charged to the reaction potential of 4.8 V of the gas generating agent.
  • the change of the positive electrode initial discharge capacity Qpd shown in b2 of FIG. 7 shows the case where the positive electrode is discharged from SOC 100% to less than SOC 0%. Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 4.3 V to 3.0 V (the discharge final voltage of the positive electrode).
  • the positive electrode irreversible capacity Qpf is a capacity obtained by subtracting the initial capacity of the positive electrode first discharge capacity Qpd from the initial capacity of the positive electrode initial charge capacity Qpc.
  • the positive electrode irreversible capacity Qpf is generated due to the slow diffusion rate of lithium absorption into the crystal structure at the end of discharge.
  • the positive electrode reversible capacity Qpk is a capacity obtained by subtracting the positive electrode irreversible capacity Qpf from the capacity at SOC 100%.
  • the charge termination voltage of the positive electrode is preferably 4.2 V or more and 4.3 V or less based on lithium metal.
  • the discharge termination voltage of the positive electrode is preferably 2.5 V or more and 3.0 V or less based on lithium metal.
  • the solid line indicated by d1 in FIG. 7 represents the change of the battery capacity Qc.
  • the battery voltage is represented by the difference between the positive electrode potential and the negative electrode potential.
  • the battery capacity Qc indicates a capacity between SOC 0% and SOC 100%.
  • SOC means a state of charge where an upper limit voltage can be obtained within the range of reversibly chargeable and dischargeable operating voltage, that is, a fully charged state is SOC 100% and a state where a lower limit voltage is obtained is SOC 0% It shows the state of charge when.
  • secondary batteries are used between SOC 0% and SOC 100%.
  • the SOC 100% performs constant current charging at a current of 1 C until the battery voltage reaches 4.2 V (battery charge termination voltage), and then, after reaching a voltage of 4.2 V, charging for 2 hours at a constant voltage of 4.2 V It is in a state of SOC 0% is a state in which constant current discharge is performed at a current of 1 C until the battery voltage reaches 2.7 V (discharge final voltage of the battery).
  • the charge termination voltage of the secondary battery is a voltage that can be safely used without causing an excessive load on the secondary battery, and is preferably 4.1 V or more and 4.3 V or less.
  • the discharge end voltage of the secondary battery is preferably 2.5 V or more and 3.0 V or less.
  • the dotted line indicated by d2 in FIG. 7 indicates the overcharge area of the secondary battery.
  • Overcharging of the secondary battery refers to a state of charge of 100% or more of SOC.
  • the gas generating agent is decomposed, the internal pressure of the secondary battery is increased, and the current interrupting mechanism operates.
  • the capacity from SOC 100% to the voltage at which the gas generating agent reacts is referred to as overcharge capacity Qcoc of the secondary battery.
  • the overcharged negative electrode capacity Qnoc of the negative electrode is a capacity from 100% of SOC to when the negative electrode potential reaches 0.005V.
  • the overcharge negative electrode capacity Qnoc of the negative electrode is set larger than the overcharge capacity Qcoc of the secondary battery. If the overcharge negative electrode capacity Qnoc is smaller than the overcharge capacity Qcoc, lithium is deposited on the surface of the negative electrode before the current interrupting mechanism operates during overcharge, thereby separating the positive and negative electrodes. As a result, the positive and negative electrodes may be short-circuited, which may damage the secondary battery.
  • the positive electrode mixture includes the positive electrode active material, the positive electrode conductive material, the positive electrode binder, and the positive electrode gas generating compound.
  • the positive electrode active material is preferably lithium oxide. Examples thereof include lithium cobaltate, lithium manganate, lithium nickelate, lithium complex oxide (lithium oxide containing two or more types selected from cobalt, nickel and manganese) and the like. In this embodiment, lithium oxide containing cobalt, nickel and manganese was used.
  • a gas-generating compound it is preferable to add a gas-generating compound to the positive electrode mixture in order to ensure safety during overcharge.
  • the gas generating compound include a carbonic acid inorganic compound, a boric acid inorganic compound, and a nitric acid inorganic compound that generate gas at the positive electrode potential in the overcharged state.
  • inorganic carbonated compounds are preferable, and examples thereof include lithium carbonate.
  • lithium carbonate was contained in the positive electrode. Lithium carbonate reacts at a potential of 4.8 V or more with respect to lithium metal to generate gas.
  • the negative electrode mixture comprises the negative electrode active material, the negative electrode binder, and the thickener.
  • the negative electrode mixture may have a negative electrode conductive material such as acetylene black.
  • Graphite carbon is preferably used as the negative electrode active material.
  • the active material used for negative mix is used 1 type, or 2 or more types of these. In the present embodiment, natural graphite was used.
  • the secondary battery is composed of a positive electrode having a positive electrode capacity measured in the charge and discharge test shown in FIG. 7 and a negative electrode having a negative electrode capacity measured in the charge and discharge test shown in FIG.
  • the positive electrode initial charge capacity of the positive electrode active material is 175 mAh / g
  • the positive electrode initial charge capacity per unit area of the positive electrode coated with the positive electrode active material is 1.82 mAh / cm 2
  • the unit area of the positive electrode is The positive electrode reversible capacity per unit area is 1.60 mAh / cm 2
  • the positive electrode irreversible capacity per unit area of the positive electrode is 0.22 mAh / cm 2.
  • the negative electrode initial charge capacity of the negative electrode active material is 360 mAh / g, and the negative electrode initial charge capacity per unit area of the negative electrode coated with the negative electrode active material is 2.72 mAh / cm 2.
  • the negative electrode reversible capacity per unit area of the negative electrode is 2.45 mAh / cm 2, and the negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
  • the lithium ion secondary battery in the present embodiment is configured of such a positive electrode and a negative electrode.
  • the irreversible capacity per unit area of the negative electrode is larger than the irreversible capacity of the positive electrode, so when constant current discharge is performed at a current of 1 C until the battery voltage reaches 2.7 V. The reduction of the battery voltage is caused by the negative electrode.
  • the negative electrode is provided with a sufficient capacity even at the potential at which the gas generating agent reacts during overcharge. This improves the safety of the secondary battery against overcharging. Specifically, the capacity until the potential of the positive electrode exceeds the charge termination voltage of the secondary battery and reaches the reaction potential of the gas generating agent, and the potential of the negative electrode exceeds the charge termination voltage of the secondary battery and the charge termination of the negative electrode make it smaller than the capacity to reach the voltage. In other words, the ratio of the overcharged negative electrode capacity Qnoc to the overcharged negative electrode capacity Qcoc is 1.0 or more.
  • FIG. 8 is a graph showing the rate of increase in battery resistance of the secondary battery. Specifically, it is a diagram showing a rate of increase in battery resistance when the cycle test of the secondary battery is performed by changing the ratio (Qnk / Qc) of the negative electrode reversible capacity Qnk to the battery capacity Qc. In the cycle test, the secondary battery was repeatedly charged and discharged with constant current in a range from 30% SOC to 70% SOC in an environment of 25 ° C.
  • the battery resistance was measured by adjusting the battery voltage to 3.7 V in an environment of 25 ° C. of the secondary battery. First, after charging to 3.7 V with a constant current of 1 C, charging was performed with a constant voltage for 2 hours, and then discharging was performed with a current of 60 A, and the battery resistance after 10 seconds was determined. The battery resistance was determined by dividing the difference between the voltage before current application and the voltage after 10 seconds by the applied current. The rate of increase of battery resistance is the ratio of battery resistance before and after the cycle test. The battery resistance was measured daily, and a cycle test was performed until the rate of increase in battery resistance reached 130%.
  • the horizontal axis in FIG. 8 is the ratio (Qnk / Qc) of the negative electrode reversible capacity Qnk to the battery capacity Qc, and the vertical axis is the number of cycles until the battery resistance increase rate reaches 130% (days).
  • the cycle days were plotted in the graph according to the ratio (Qnk / Qc) of the negative electrode reversible capacity Qnk to the battery capacity Qc of the secondary battery.
  • the cycle characteristic of the secondary battery is better as the ratio of the negative electrode reversible capacity Qnk to the battery capacity Qc is higher. This is because the mass of the negative electrode active material accompanied by charge and discharge reaction in the voltage range usually used is increased, so the current load on the electrode is reduced and the cycle characteristics are improved without adding the gas generating agent excessively. It is because
  • the ratio is 1.5 or more, taking a margin.
  • the secondary battery includes a positive electrode including a positive electrode mixture layer, a negative electrode including a negative electrode mixture layer, and a gas generating agent that generates a decomposition gas when the battery voltage exceeds a predetermined voltage.
  • the non-aqueous electrolyte as described above is accommodated in the battery case, and is provided with a current interrupting mechanism that operates when the pressure in the battery case rises with the generation of the decomposition gas at the time of overcharging.
  • Lithium carbonate is contained in the positive electrode as a gas generating agent.
  • FIG. 9 is a graph showing the relationship between the potential and the capacity of the secondary battery in the present embodiment.
  • the vertical axis represents the positive and negative electrode potentials of the secondary battery and the battery voltage (V), and the horizontal axis represents the capacity (mAh).
  • the relationship between the potential and the capacity of the secondary battery shown in FIG. 9 in the present embodiment shows characteristics when the positive electrode irreversible capacity Qpf is larger than the negative electrode irreversible capacity Qnf.
  • the dotted line indicated by a3 in FIG. 9 represents the change in the negative electrode initial charge capacity Qnc, and the solid line indicated by a4 represents the change in the negative electrode initial discharge capacity Qnd.
  • the dotted line indicated by b3 in FIG. 9 represents the change in the positive electrode initial charge capacity Qpc, and the solid line indicated by b4 represents the change in the positive electrode initial discharge capacity Qpd.
  • the solid line indicated by d3 in FIG. 9 represents the change of the battery capacity Qc.
  • the dotted line indicated by d4 in FIG. 9 indicates the overcharge area of the secondary battery.
  • the change in negative electrode initial charge capacity Qnc shown in a3 in the figure gradually charges the negative electrode from less than 0% of SOC, further charges it more than 0% of SOC, and further charges it more than 100% of SOC, the reaction of the gas generating agent
  • the case where it charges until it exceeds electric potential is shown.
  • constant current charging is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 1.6 V to 0.005 V (the charge termination voltage of the negative electrode), and after reaching a voltage of 0.005 V , Charge for 2 hours with a constant voltage of 0.005V.
  • the negative electrode is set to a charge capacity exceeding the reaction potential of the gas generating agent.
  • the overcharge negative electrode capacity Qnoc is set larger than the overcharge capacity Qcoc.
  • the change of the negative electrode initial discharge capacity Qnd shown in a4 of FIG. 9 shows a case where the negative electrode is gradually discharged from the charge capacity exceeding the reaction potential of the gas generating agent to 100% SOC and discharged to SOC 0% (less than). Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 0.005 V to 1.6 V (discharge termination voltage of the negative electrode).
  • the negative electrode irreversible capacity Qnf is a capacity obtained by subtracting the initial capacity of the negative electrode first discharge capacity Qnd from the initial capacity of the negative electrode initial charge capacity Qnc.
  • the negative electrode reversible capacity Qnk is a capacity obtained by subtracting the negative electrode irreversible capacity Qnf from the capacity exceeding the reaction potential of the gas generating agent.
  • the charge termination voltage of the negative electrode is preferably 0.005 V or more and 0.010 V or less based on lithium metal.
  • the discharge termination voltage of the negative electrode is preferably 1.5 V or more and 1.6 V or less based on lithium metal.
  • the dotted line indicated by b3 in FIG. 9 represents the change in the positive electrode initial charge capacity Qpc
  • the solid line indicated by b4 represents the change in the positive electrode initial discharge capacity Qpd.
  • the change in the positive electrode initial charge capacity Qpc indicated by b3 in the figure indicates the case where the positive electrode is gradually charged from less than 0% of SOC, charged to more than 0% of SOC, and charged to a potential of 4.3V at 100% of SOC. Specifically, constant current charging is performed with a current of 0.2 C until the potential with respect to lithium metal becomes 4.3 V (positive electrode charge termination voltage) corresponding to 3.0 V to SOC 100%, and then 4.3 V After reaching a voltage of 2, charge for 2 hours with a constant voltage of 4.3V.
  • the dotted line indicates the case where the SOC is further charged up to 100% and charged to the reaction potential of 4.8 V of the gas generating agent.
  • the change of the positive electrode initial discharge capacity Qpd indicated by b4 in FIG. 9 shows the case where the positive electrode is discharged from SOC 100% to SOC 0%. Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 4.3 V to 3.0 V (the discharge final voltage of the positive electrode).
  • the positive electrode irreversible capacity Qpf is a capacity obtained by subtracting the initial capacity of the positive electrode first discharge capacity Qpd from the initial capacity of the positive electrode initial charge capacity Qpc.
  • the positive electrode reversible capacity Qpk is a capacity obtained by subtracting the positive electrode irreversible capacity Qpf from the capacity at SOC 100%.
  • the charge termination voltage of the positive electrode is preferably 4.2 V or more and 4.3 V or less based on lithium metal.
  • the discharge termination voltage of the positive electrode is preferably 2.5 V or more and 3.0 V or less based on lithium metal.
  • the solid line indicated by d3 in FIG. 9 represents the change of the battery capacity Qc.
  • the battery voltage is represented by the difference between the positive electrode potential and the negative electrode potential.
  • the battery capacity Qc indicates a capacity between SOC 0% and SOC 100%.
  • the SOC 100% performs constant current charging at a current of 1 C until the battery voltage reaches 4.2 V (battery charge termination voltage), and then, after reaching a voltage of 4.2 V, charging for 2 hours at a constant voltage of 4.2 V It is in a state of SOC 0% is a state in which constant current discharge is performed at a current of 1 C until the battery voltage reaches 2.7 V (discharge final voltage of the battery).
  • the charge termination voltage of the secondary battery is a voltage that can be safely used without causing an excessive load on the secondary battery, and is preferably 4.1 V or more and 4.3 V or less.
  • the discharge end voltage of the secondary battery is preferably 2.5 V or more and 3.0 V or less.
  • the dotted line indicated by d4 in FIG. 9 indicates the overcharge area of the secondary battery.
  • Overcharging of the secondary battery refers to a state of charge of 100% or more of SOC.
  • the gas generating agent is decomposed, the internal pressure of the secondary battery is increased, and the current interrupting mechanism operates.
  • the capacity from SOC 100% to the voltage at which the gas generating agent reacts is referred to as overcharge capacity Qcoc.
  • the overcharged negative electrode capacity Qnoc of the negative electrode is a capacity from 100% of SOC to when the negative electrode potential reaches 0.005V.
  • the overcharge negative electrode capacity Qnoc of the negative electrode is set larger than the overcharge capacity Qcoc of the secondary battery.
  • the positive electrode reversible capacity Qpk which is the capacity until the potential of the positive electrode reaches the charge termination voltage of the secondary battery, and the charge termination voltage of the secondary battery, until the potential of the positive electrode reaches the reaction potential of the gas generating agent
  • the sum with the overcharge capacity Qcoc which is the capacity of the above, is set smaller than the negative electrode reversible capacity Qnk of the negative electrode.
  • the positive electrode mixture and the negative electrode mixture are the same as those described in the first embodiment, and thus the description thereof is omitted.
  • capacitance of the positive electrode of the lithium ion secondary battery in this embodiment and a negative electrode is demonstrated.
  • the secondary battery is composed of a positive electrode having a positive electrode capacity measured in the charge and discharge test shown in FIG. 9 and a negative electrode having a negative electrode capacity measured in the charge and discharge test shown in FIG.
  • the positive electrode initial charge capacity of the positive electrode active material is 180 mAh / g
  • the positive electrode initial charge capacity per unit area of the positive electrode coated with the positive electrode active material is 1.87 mAh / cm 2
  • the unit area of the positive electrode is The positive electrode reversible capacity per unit area is 1.59 mAh / cm 2
  • the positive electrode irreversible capacity per unit area of the positive electrode is 0.28 mAh / cm 2.
  • the negative electrode initial charge capacity of the negative electrode active material is 365 mAh / g, and the negative electrode initial charge capacity per unit area of the negative electrode coated with the negative electrode active material is 2.75 mAh / cm 2.
  • the negative electrode reversible capacity per unit area of the negative electrode is 2.48 mAh / cm 2, and the negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
  • the lithium ion secondary battery in the present embodiment is configured of such a positive electrode and a negative electrode.
  • the irreversible capacity per unit area of the positive electrode is larger than the irreversible capacity of the negative electrode, constant current discharge at a current of 1 C until the battery voltage becomes 2.7 V The reduction of the battery voltage is caused by the positive electrode.
  • the safety of the secondary battery against overcharge can be improved by providing a sufficient capacity in the negative electrode even at the potential at which the gas generating agent reacts at the time of overcharge.
  • the internal pressure of the battery container 60 containing the positive electrode having the positive electrode mixture, the negative electrode having the negative electrode mixture, the positive electrode and the negative electrode, and the battery container 60 has a predetermined operating pressure.
  • a current blocking mechanism 181 for blocking the current flowing between the positive electrode and the negative electrode, and the positive electrode mixture contains a gas generating agent, and the potential of the positive electrode is the charge termination voltage of the secondary battery 1, 100.
  • the capacity until the reaction potential of the gas generating agent is reached is smaller than the capacity until the potential of the negative electrode exceeds the charge termination voltage of the secondary battery 1, 100 to reach the charge termination voltage of the negative electrode.
  • the reaction potential of the gas generating agent in the secondary batteries 1 and 100 is 4.8 V to 5.0 V. Thereby, a secondary battery excellent in safety against overcharge can be provided.
  • the gas generating agent in the secondary battery 1, 100 is lithium carbonate.
  • lithium carbonate in the positive electrode As a gas generating agent, it is possible to provide a secondary battery excellent in safety against overcharge.
  • the negative electrode active material of the negative electrode in the secondary batteries 1 and 100 is one or more of natural graphite, artificial graphite, non-graphitizable carbon, graphitizable carbon, and silicon oxide mixed. This improves the safety of the secondary battery against overcharging.
  • the charge termination voltage of the negative electrode in the secondary battery 1, 100 is in the range of 0.01 V to 0.005 V. This improves the safety of the secondary battery against overcharging.
  • the secondary battery 1, 100 has a capacity until the potential of the positive electrode reaches the charge termination voltage of the secondary battery 1, 100 and the charge termination voltage of the secondary battery 1, 100.
  • the sum of the capacity of the gas generating agent until reaching the reaction potential is smaller than the reversible capacity of the negative electrode.
  • the negative electrode can sufficiently receive the charge capacity until the gas generating agent decomposes and the current blocking mechanism reacts, so it is not necessary to add the gas generating agent in excess.
  • the ratio of the reversible capacity of the negative electrode to the battery capacity of the secondary batteries 1 and 100 is 1.5 or more.
  • the positive electrode first charge capacity per unit area of the positive electrode coated with the positive electrode active material is 1.82 mAh / cm 2
  • the positive electrode reversible capacity per unit area of the positive electrode is 1.60 mAh /
  • the positive electrode irreversible capacity per unit area of the positive electrode is 0.22 mAh / cm 2
  • the negative electrode of the secondary battery has a negative electrode initial charge capacity of 2.72 mAh / cm 2 per unit area of the negative electrode coated with the negative electrode active material, and a negative electrode reversible capacity of 2.45 mAh / cm 2 per unit area of the negative electrode.
  • the negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
  • the positive electrode of the secondary battery has a first charge capacity per unit area of the positive electrode coated with the positive electrode active material of 1.87 mAh / cm 2 and a reversible capacity per unit area of the positive electrode of 1.59 mAh / and the positive electrode irreversible capacity per unit area of the positive electrode is 0.28 mAh / cm 2, and
  • the negative electrode of the secondary battery has an initial negative charge capacity per unit area of the negative electrode coated with the negative electrode active material of 2.75 mAh / cm 2, and a negative electrode reversible capacity per unit area of the negative electrode of 2.48 mAh / cm 2
  • the negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
  • the negative electrode can sufficiently receive the charge capacity until the gas generating agent decomposes and the current blocking mechanism reacts, so it is not necessary to add the gas generating agent in excess.

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Abstract

If the charging capacity of a negative electrode is small, there is a risk that lithium will precipitate on the surface of the negative electrode and break through the separator that divides the positive and negative electrodes, causing a short circuit between the positive and negative electrodes, and thereby damaging the secondary battery. This secondary battery 1, 100 comprises: a positive electrode having a positive electrode mixture; a negative electrode having a negative electrode mixture; a battery container 60 for accommodating the positive electrode and the negative electrode; and a current shut-off mechanism 181 that shuts off the current flowing between the positive electrode and the negative electrode when the internal pressure of the battery container 60 has reached a prescribed working pressure. The positive electrode mixture contains a gas generating agent. The capacity that accommodates an increase in the potential of the positive electrode, from the charging termination voltage of the secondary battery 1, 100 to the potential which triggers the gas generating agent reaction, is made to be smaller than the capacity that accommodates an increase in the potential of the negative electrode, from the charging termination voltage of the secondary battery 1, 100 to the charging termination voltage of the negative electrode.

Description

二次電池Secondary battery
　本発明は、二次電池に関する。 The present invention relates to a secondary battery.
　近年、電気自動車及びハイブリッド自動車には二次電池としてリチウムイオン電池が用いられている。このような二次電池は、高出力、高エネルギー密度および安全性が求められる。特に、二次電池は誤操作等による過充電になった場合でも電池システムの安全性が損なわれないようにする必要がある。そのため、過充電になった場合に安全性を確保するために二次電池に電流遮断機構が設けられている。 In recent years, lithium ion batteries are used as secondary batteries in electric vehicles and hybrid vehicles. Such secondary batteries are required to have high output, high energy density and safety. In particular, it is necessary to prevent the safety of the battery system from being impaired even if the secondary battery is overcharged due to an erroneous operation or the like. Therefore, in order to ensure safety in the event of overcharging, a secondary battery is provided with a current interrupting mechanism.
　特許文献１には、ガス発生剤として正極合剤に炭酸リチウムが含有され、過充電になった場合に炭酸リチウムが分解ガスを発生して電流遮断機構を作動させる電池システムが記載されている。 Patent Document 1 describes a battery system in which lithium carbonate is contained in a positive electrode mixture as a gas generating agent, and lithium carbonate generates a decomposition gas to operate a current interrupting mechanism when overcharged.
特開２０１３－１３８０１４号公報JP, 2013-138014, A
　特許文献１では、過充電時に分解ガスが発生する電位までの負極の充電容量について規定されていない。例えば、過充電の状態でガス発生剤の反応電位に到達する前に、負極の充電容量が少ない場合には、負極電極表面にリチウムが析出して、正負極を分離しているセパレータを突き破り、正負極間が短絡して、二次電池が破損する虞がある。 Patent Document 1 does not specify the charge capacity of the negative electrode up to the potential at which a decomposition gas is generated at the time of overcharge. For example, when the charge capacity of the negative electrode is small before reaching the reaction potential of the gas generating agent in the overcharged state, lithium is deposited on the surface of the negative electrode, and breaks through the separator separating the positive and negative electrodes, There is a possibility that the secondary battery may be damaged due to a short circuit between the positive and negative electrodes.
　本発明による二次電池は、正極合剤を有する正極と、負極合剤を有する負極と、前記正極と前記負極を収容する電池容器と、前記電池容器の内圧が所定の作動圧となったときに、前記正極と負極の間に流れる電流を遮断する電流遮断機構と、を備える二次電池であって、　前記正極合剤にはガス発生剤が含まれ、前記正極の電位が前記二次電池の充電終止電圧を超えて前記ガス発生剤の反応電位に達するまでの容量を、前記負極の電位が前記二次電池の充電終止電圧を超えて前記負極の充電終止電圧に達するまでの容量よりも小さくした。 In the secondary battery according to the present invention, when the positive electrode having the positive electrode mixture, the negative electrode having the negative electrode mixture, the battery container accommodating the positive electrode and the negative electrode, and the internal pressure of the battery container reach a predetermined operating pressure A current blocking mechanism for interrupting a current flowing between the positive electrode and the negative electrode, wherein the positive electrode mixture contains a gas generating agent, and the potential of the positive electrode is the secondary battery. The capacity until the reaction potential of the gas generating agent is exceeded by exceeding the charge termination voltage of the battery is more than the capacity until the potential of the negative electrode exceeds the charge termination voltage of the secondary battery and reaches the charge termination voltage of the negative electrode. I made it smaller.
　本発明によれば、過充電に対する安全性に優れた二次電池を提供することができる。 According to the present invention, a secondary battery excellent in overcharge safety can be provided.
円筒形二次電池の縦断面図である。It is a longitudinal cross-sectional view of a cylindrical secondary battery. 円筒形二次電池の分解斜視図である。It is a disassembled perspective view of a cylindrical secondary battery. 円筒形二次電池の発電ユニットを示す図である。It is a figure which shows the electric power generation unit of a cylindrical secondary battery. 角形二次電池の外観斜視図である。It is an external appearance perspective view of a square secondary battery. 角形二次電池の分解斜視図である。It is a disassembled perspective view of a square secondary battery. 角形二次電池の捲回電極群を示す図である。It is a figure which shows the winding electrode group of a square secondary battery. 第１の実施形態における二次電池の電位と容量の関係を示すグラフである。It is a graph which shows the relationship of the electric potential and capacity | capacitance of the secondary battery in 1st Embodiment. 二次電池の電池抵抗の上昇率を示した図である。It is the figure which showed the rise rate of the battery resistance of the secondary battery. 第２の実施形態における二次電池の電位と容量の関係を示すグラフである。It is a graph which shows the relationship of the electric potential of the secondary battery in 2nd Embodiment, and a capacity | capacitance.
　本発明の実施形態の説明に先立って、本発明の実施形態において適用する円筒形二次電池および角形二次電池の構成について説明する。
［円筒形二次電池の構成］
　図１～図３は、円筒形二次電池１の構成の一例を示す図である。
　図１は、円筒形二次電池１の縦断面図である。円筒形二次電池１は、例えば、外形４０ｍｍφ、高さ１００ｍｍの寸法を有する。この円筒形二次電池１は、密閉蓋５０で開口部が封止される有底円筒形の電池缶６０の内部に発電ユニット２０を収容して構成されている。まず、電池缶６０と発電ユニット２０について説明し、次に、密閉蓋５０を説明する。 Prior to the description of the embodiments of the present invention, the configurations of cylindrical secondary batteries and prismatic secondary batteries applied in the embodiments of the present invention will be described.
[Configuration of cylindrical secondary battery]
1 to 3 are diagrams showing an example of the configuration of a cylindrical secondary battery 1.
FIG. 1 is a longitudinal sectional view of a cylindrical secondary battery 1. The cylindrical secondary battery 1 has dimensions of, for example, an outer diameter of 40 mm and a height of 100 mm. The cylindrical secondary battery 1 is configured such that the power generation unit 20 is accommodated inside a bottomed cylindrical battery can 60 whose opening is sealed by a sealing lid 50. First, the battery can 60 and the power generation unit 20 will be described, and next, the sealing lid 50 will be described.
　有底円筒形の電池缶６０には、缶開口端部 (図中上側)にかしめ部６１が形成されている。このかしめ部６１で密閉蓋５０を電池缶６０にかしめ固定することにより、開口部を密閉し、非水電解液を使用する密閉形の円筒形二次電池１のシール性能を担保している。かしめ部６１は、缶開口端部を内側に折り曲げてなる折り曲げ部６２、および電池底面側に所定距離離れた位置で内側に突き出したグルービング部６３とを備えている。後述するように、折り曲げ部６２とグルービング部６３との間にガスケット４３を介在させて密閉蓋５０がかしめ固定され、円筒形二次電池１が密閉されている。 In the bottomed cylindrical battery can 60, a caulking portion 61 is formed at the can opening end (upper side in the figure). By sealing the sealing lid 50 to the battery can 60 by the caulking portion 61, the opening is sealed to secure the sealing performance of the sealed cylindrical secondary battery 1 using the non-aqueous electrolyte. The caulking portion 61 includes a bent portion 62 formed by bending the can open end inward, and a grooving portion 63 protruding inward at a predetermined distance on the battery bottom side. As described later, the sealing lid 50 is crimped and fixed by interposing the gasket 43 between the bent portion 62 and the grooving portion 63, and the cylindrical secondary battery 1 is sealed.
　発電ユニット２０は、電極群１０と、正極集電部材３１と、負極集電部材２１とを、以下で説明するように一体的にユニット化して構成されている。電極群１０は、中央部に軸芯１５を有し、軸芯１５の周囲に正極電極、負極電極およびセパレータが捲回されている。 The power generation unit 20 is integrally configured by unitizing the electrode group 10, the positive electrode current collecting member 31, and the negative electrode current collecting member 21 as described below. The electrode group 10 has an axial core 15 at the central portion, and a positive electrode, a negative electrode and a separator are wound around the axial core 15.
　中空な円筒形状の軸芯１５は軸方向（図面の上下方向）の上端部の内面に径大の凹部１５ａが形成され、この凹部１５ａに正極集電部材３１が圧入されている。正極集電部材３１は、例えば、アルミニウムにより形成され、円盤状の基部３１ａ、この基部３１ａの内周部において軸芯１５側に向かって突出し、軸芯１５の内面に圧入される下部筒部３１ｂ、および外周縁において密閉蓋５０側に突き出す上部筒部３１ｃを有する。正極集電部材３１の基部３１ａには、過充電時に電池内部で発生する分解ガスを放出するための開口部３１ｄが形成されている。 The hollow cylindrical shaft core 15 has a large diameter recess 15a formed on the inner surface of the upper end in the axial direction (vertical direction in the drawing), and the positive electrode current collector 31 is press-fitted into the recess 15a. The positive electrode current collecting member 31 is made of, for example, aluminum, and a disk-like base 31a, a lower cylindrical portion 31b which protrudes toward the shaft core 15 at the inner peripheral portion of the base 31a and is pressed into the inner surface of the shaft core 15. And an upper cylindrical portion 31 c protruding toward the sealing lid 50 at the outer peripheral edge. The base 31 a of the positive electrode current collecting member 31 is formed with an opening 31 d for releasing a decomposition gas generated inside the battery at the time of overcharging.
　後述の図３で詳述する正極シート１１ａの正極リード１６は、すべて、正極集電部材３１の上部筒部３１ｃに溶接される。この場合、正極リード１６は、正極集電部材３１の上部筒部３１ｃ上に重なり合って接合される。各正極リード１６は大変薄いため、１つでは大電流を取りだすことができない。このため、軸芯１５への巻き始めから巻き終わりまでの全長に亘り、多数の正極リード１６が所定間隔に形成されている。 The positive electrode leads 16 of the positive electrode sheet 11 a described in detail later with reference to FIG. 3 are all welded to the upper cylindrical portion 31 c of the positive electrode current collecting member 31. In this case, the positive electrode lead 16 is overlapped and joined onto the upper cylindrical portion 31 c of the positive electrode current collecting member 31. Since each positive electrode lead 16 is very thin, one can not take out a large current. For this reason, a large number of positive electrode leads 16 are formed at predetermined intervals over the entire length from the winding start to the winding end on the shaft core 15.
　正極集電部材３１の上部筒部３１ｃの外周には、正極シート１１ａの正極リード１６およびリング状の押え部材３２が溶接されている。多数の正極リード１６は、正極集電部材３１の上部筒部３１ｃの外周に密着させておき、正極リード１６の外周に押え部材３２を巻き付けて仮固定し、この状態で溶接される。 The positive electrode lead 16 of the positive electrode sheet 11 a and the ring-shaped pressing member 32 are welded to the outer periphery of the upper cylindrical portion 31 c of the positive electrode current collecting member 31. The large number of positive electrode leads 16 are in close contact with the outer periphery of the upper cylindrical portion 31c of the positive electrode current collecting member 31, and the pressing member 32 is wound around the outer periphery of the positive electrode lead 16 and temporarily fixed.
　正極集電部材３１は、電解液によって酸化されるので、アルミニウムで形成することにより信頼性を向上することができる。アルミニウムは、なんらかの加工により表面が露出すると、直ちに、表面に酸化アルミウム皮膜が形成され、この酸化アルミニウム皮膜により、電解液による酸化を防止することができる。また、正極集電部材３１をアルミニウムで形成することにより、正極シート１１ａの正極リード１６を超音波溶接またはスポット溶接等により溶接することが可能となる。 Since the positive electrode current collecting member 31 is oxidized by the electrolytic solution, the reliability can be improved by forming it with aluminum. As soon as the surface is exposed by processing, aluminum forms an aluminum oxide film on the surface, and this aluminum oxide film can prevent oxidation by the electrolytic solution. Further, by forming the positive electrode current collecting member 31 of aluminum, it is possible to weld the positive electrode lead 16 of the positive electrode sheet 11a by ultrasonic welding, spot welding or the like.
　軸芯１５の下端部の外周には、外径が径小とされた段部１５ｂが形成され、この段部１５ｂに負極集電部材２１が圧入されて固定されている。負極集電部材２１は、例えば、銅により形成され、円盤状の基部２１ａに軸芯１５の段部１５ｂに圧入される開口部２１ｂが形成され、外周縁に、電池缶６０の底部側に向かって突き出す外周筒部２１ｃが形成されている。 A stepped portion 15 b whose outer diameter is reduced in diameter is formed on the outer periphery of the lower end portion of the shaft core 15, and the negative electrode current collecting member 21 is press-fitted and fixed to the stepped portion 15 b. The negative electrode current collecting member 21 is formed of, for example, copper, and an opening 21b which is press-fit into the step 15b of the shaft core 15 is formed in the disk-shaped base 21a. An outer peripheral tubular portion 21c is formed to protrude.
　後述の図３で詳述する負極シート１２ａの負極リード１７は、すべて、負極集電部材２１の外周筒部２１ｃに超音波溶接等により溶接される。各負極リード１７は大変薄いため、大電流を取りだすために、軸芯１５への巻き始めから巻き終わりまで全長にわたり、所定間隔で多数形成されている。 The negative electrode leads 17 of the negative electrode sheet 12a described in detail in FIG. 3 to be described later are all welded to the outer peripheral cylindrical portion 21c of the negative electrode current collecting member 21 by ultrasonic welding or the like. Since each negative electrode lead 17 is very thin, many are formed at predetermined intervals over the entire length from the winding start to the winding end to the shaft core 15 in order to take out a large current.
　負極集電部材２１の外周筒部２１ｃの外周には、負極シート１２ａの負極リード１７およびリング状の押え部材２２が溶接されている。多数の負極リード１７は、負極集電部材２１の外周筒部２１ｃの外周に密着させておき、負極リード１７の外周に押え部材２２を巻き付けて仮固定し、この状態で溶接される。 The negative electrode lead 17 of the negative electrode sheet 12 a and the ring-shaped pressing member 22 are welded to the outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting member 21. The large number of negative electrode leads 17 are in close contact with the outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting member 21, and the pressing member 22 is wound around and temporarily fixed to the outer periphery of the negative electrode lead 17.
　負極集電部材２１の下面には、銅製の負極通電リード２３が溶接されている。負極通電リード２３は、電池缶６０の底部において、電池缶６０に溶接されている。電池缶６０は、例えば、０．５ｍｍの厚さの炭素鋼で形成され、表面にニッケルメッキが施されている。このような材料を用いることにより、負極通電リード２３は、電池缶６０に抵抗溶接等により溶接することができる。 A copper negative electrode current supply lead 23 is welded to the lower surface of the negative electrode current collector 21. The negative electrode current supply lead 23 is welded to the battery can 60 at the bottom of the battery can 60. The battery can 60 is formed, for example, of carbon steel with a thickness of 0.5 mm, and the surface is plated with nickel. By using such a material, the negative electrode current supply lead 23 can be welded to the battery can 60 by resistance welding or the like.
　正極集電部材３１の基部３１ａの上面には、複数のアルミニウム箔が積層されて構成されたフレキシブルな正極導電リード３３が、その一端部を溶接されて接合されている。正極導電リード３３は、複数枚のアルミニウム箔を積層して一体化することにより、大電流を流すことが可能とされ、且つ、フレキシブル性を付与されている。つまり、大電流を流すには接続部材の厚さを大きくする必要があるが、１枚の金属板で形成すると剛性が大きくなり、フレキシブル性が損なわれる。そこで、板厚の小さな多数のアルミニウム箔を積層してフレキシブル性を持たせている。正極導電リード３３の厚さは、例えば、０．５ｍｍ程度であり、厚さ０．１ｍｍのアルミニウム箔を５枚積層して形成される。 A flexible positive electrode conductive lead 33 formed by laminating a plurality of aluminum foils is welded to one end of the upper surface of the base portion 31 a of the positive electrode current collector 31 by welding. The positive electrode conductive lead 33 is made possible to flow a large current by laminating and integrating a plurality of aluminum foils, and is given flexibility. That is, in order to flow a large current, it is necessary to increase the thickness of the connecting member, but if it is formed of a single metal plate, the rigidity is increased and the flexibility is impaired. Therefore, a large number of thin aluminum foils are laminated to give flexibility. The thickness of the positive electrode conductive lead 33 is, for example, about 0.5 mm, and is formed by laminating five aluminum foils each having a thickness of 0.1 mm.
　図２は、図１に示した円筒形二次電池の分解斜視図である。
　電極群１０は、中央部に軸芯１５（図１参照）を有し、軸芯１５の周囲に正極電極、負極電極およびセパレータが捲回されている。そして最外周の第１のセパレータ１３が接着テープ１９で止められる。 FIG. 2 is an exploded perspective view of the cylindrical secondary battery shown in FIG.
The electrode group 10 has an axial core 15 (see FIG. 1) at the center, and a positive electrode, a negative electrode and a separator are wound around the axial core 15. Then, the outermost first separator 13 is stopped by the adhesive tape 19.
　密閉蓋５０は、排気口３ｃを有するキャップ３と、キャップ３に装着され開裂溝３７ａを有するキャップケース３７と、キャップケース３７の中央部裏面にスポット溶接された正極接続板３５と、正極接続板３５の周縁上面とキャップケース３７の裏面との間に挟持される絶縁リング４１とを備え、予めサブアセンブリとして組み立てられている。 The sealing lid 50 is provided with a cap 3 having an exhaust port 3c, a cap case 37 mounted on the cap 3 and having a cleavage groove 37a, a positive electrode connection plate 35 spot-welded to the back of a central portion of the cap case 37, a positive electrode connection plate It comprises an insulating ring 41 sandwiched between the peripheral upper surface of 35 and the back surface of the cap case 37, and is assembled in advance as a subassembly.
　キャップ３は、炭素鋼等の鉄にニッケルメッキを施して形成されている。キャップ３は、円盤状の周縁部３ａと、この周縁部３ａから上方に突出する有頭無底の筒部３ｂとを有し、全体としてハット型を呈している。筒部３ｂには、中央に排気口３ｃが形成されている。筒部３ｂは正極外部端子として機能し、バスバーなどが接続される。 The cap 3 is formed by applying nickel plating to iron such as carbon steel. The cap 3 has a disk-like peripheral portion 3a and a headless, bottomed cylindrical portion 3b projecting upward from the peripheral portion 3a, and has a hat-like shape as a whole. An exhaust port 3c is formed at the center of the cylindrical portion 3b. The cylindrical portion 3b functions as a positive electrode external terminal, and a bus bar or the like is connected.
　キャップ３の周縁部は、アルミニウム合金で形成されたキャップケース３７の折り返しフランジ３７ｂで一体化されている。すなわち、キャップケース３７の周縁をキャップ３の上面に沿って折り返してキャップ３がかしめ固定されている。キャップ３の上面で折り返されている円環、すなわちフランジ３７ｂとキャップ３が摩擦接合溶接されている。すなわち、キャップケース３７とキャップ３は、フランジ３７ｂによるかしめ固定と溶接によって一体化されている。このように、密閉蓋５０はキャップケース３７とキャップ３とが一体化したフランジ５０Ｆを備えている。 The peripheral portion of the cap 3 is integrated by a folded flange 37 b of a cap case 37 formed of an aluminum alloy. That is, the peripheral edge of the cap case 37 is folded back along the upper surface of the cap 3 and the cap 3 is fixed by caulking. The annular ring folded back on the upper surface of the cap 3, that is, the flange 37b and the cap 3 are friction welded and welded. That is, the cap case 37 and the cap 3 are integrated by caulking and fixing by the flange 37 b and welding. Thus, the sealing lid 50 is provided with the flange 50F in which the cap case 37 and the cap 3 are integrated.
　キャップケース３７の中央円形領域には、円形形状の開裂溝３７ａと、この円形開裂溝３７ａから四方に放射状に伸びる開裂溝３７ａとが形成されている。開裂溝３７ａは、プレスによりキャップケース３７の上面側をＶ字形状に押し潰して、残部を薄肉にしたものである。開裂溝３７ａは、電池缶６０内の内圧が所定値以上に上昇すると開裂して、内部の分解ガスを放出する。 In the central circular area of the cap case 37, a circular cleavage groove 37a and a cleavage groove 37a radially extending in four directions from the circular cleavage groove 37a are formed. The cleavage groove 37a is formed by pressing the upper surface side of the cap case 37 into a V-shape by a press and making the remaining portion thin. The cleavage groove 37a is cleaved when the internal pressure in the battery can 60 rises to a predetermined value or more, and the decomposition gas inside is released.
　密閉蓋５０は電流遮断機構を構成している。過充電時には、電池缶６０の内部に発生した分解ガスにより、内部圧力が基準値を超えると、開裂溝３７ａにおいてキャップケース３７に亀裂が発生し、内部の分解ガスがキャップ３の排気口３ｃから排出されて電池缶６０内の圧力が低減される。また、電池缶６０の内圧によりキャップケースと呼ばれるキャップケース３７が容器外方に膨出して正極接続板３５との電気的接続が断たれ、過充電になった場合に安全性を確保する。 The sealing lid 50 constitutes a current blocking mechanism. At the time of overcharging, if the internal pressure exceeds the reference value due to the decomposition gas generated inside the battery can 60, a crack is generated in the cap case 37 in the cleavage groove 37a, and the inside decomposition gas is discharged from the exhaust port 3c of the cap 3. It is discharged and the pressure in the battery can 60 is reduced. Further, the cap case 37 called a cap case bulges out of the container due to the internal pressure of the battery can 60, and the electrical connection with the positive electrode connection plate 35 is cut off, thereby securing safety in the case of overcharging.
　なお、本発明の実施形態では、過充電時に、ガス発生剤が反応する電位においても、負極に十分な容量を設ける事で、過充電に対して安全性を向上させるものであるが、その詳細については後述する。 In the embodiment of the present invention, the safety against overcharge is improved by providing a sufficient capacity in the negative electrode even at the potential at which the gas generating agent reacts at the time of overcharge, but the details will be described. Will be described later.
　密閉蓋５０は、正極集電部材３１の上部筒部３１ｃ上に絶縁状態で載置されている。すなわち、キャップ３が一体化されたキャップケース３７は、その絶縁リング４１を介して絶縁状態で正極集電部材３１の上端面に載置されている。しかし、キャップケース３７は、正極導電リード３３により正極集電部材３１とは電気的に接続され、密閉蓋５０のキャップ３が電池１の正極となる。ここで、絶縁リング４１は、開口部４１ａおよび下方に突出する側部４１ｂを有している。絶縁リング４１の開口部４１ａ内には接続板３５が嵌合されている。 The sealing lid 50 is placed on the upper cylindrical portion 31 c of the positive electrode current collecting member 31 in an insulating state. That is, the cap case 37 in which the cap 3 is integrated is mounted on the upper end surface of the positive electrode current collecting member 31 in an insulating state via the insulating ring 41. However, the cap case 37 is electrically connected to the positive electrode current collecting member 31 by the positive electrode conductive lead 33, and the cap 3 of the sealing lid 50 becomes the positive electrode of the battery 1. Here, the insulating ring 41 has an opening 41 a and a side 41 b projecting downward. A connection plate 35 is fitted in the opening 41 a of the insulating ring 41.
　接続板３５は、アルミニウム合金で形成され、中央部を除くほぼ全体が均一でかつ、中央側が少々低い位置に撓んだ、ほぼ皿形状を有している。接続板３５の厚さは、例えば、１ｍｍ程度である。接続板３５の中心には、薄肉でドーム形状に形成された突起部３５ａが形成されており、突起部３５ａの周囲には、複数の開口部３５ｂが形成されている。開口部３５ｂは、電池内部に発生するガスを放出する機能を有している。接続板３５の突起部３５ａはキャップケース３７の中央部の底面に抵抗溶接または摩擦拡散接合により接合されている。 The connection plate 35 is formed of an aluminum alloy, has a substantially dish shape that is substantially uniform throughout substantially except for the central portion and bent to a slightly lower position on the central side. The thickness of the connection plate 35 is, for example, about 1 mm. A thin and dome-shaped protrusion 35 a is formed at the center of the connection plate 35, and a plurality of openings 35 b are formed around the protrusion 35 a. The opening 35 b has a function of releasing the gas generated inside the battery. The protrusion 35 a of the connection plate 35 is joined to the bottom surface of the central portion of the cap case 37 by resistance welding or friction diffusion bonding.
　そして、電池缶６０に電極群１０を収容し、予め部分アセンブリとして作製された密閉蓋５０を正極集電部材３１と正極導電リード３３により電気的に接続して筒上部に載置する。そして、プレス等により、ガスケット４３の外周壁部４３ｂを折曲して基部４３ａと外周壁部４３ｂにより、密閉蓋５０を軸方向に圧接するようにかしめ加工する。これにより、密閉蓋５０がガスケット４３を介して電池缶６０に固定される。 Then, the electrode assembly 10 is housed in the battery can 60, and the sealing lid 50, which is manufactured in advance as a partial assembly, is electrically connected by the positive electrode current collecting member 31 and the positive electrode conductive lead 33 and placed on the cylinder upper part. Then, the outer peripheral wall 43b of the gasket 43 is bent by a press or the like, and the sealing lid 50 is crimped so as to be pressed in the axial direction by the base 43a and the outer peripheral wall 43b. Thereby, the sealing lid 50 is fixed to the battery can 60 via the gasket 43.
　ガスケット４３は、当初、リング状の基部４３ａの周側縁に、上部方向に向けてほぼ垂直に起立して形成された外周壁部４３ｂと、内周側に、基部４３ａから下方に向けてほぼ垂直に垂下して形成された筒部４３ｃとを有する形状を有している。電池缶６０をかしめることにより、密閉蓋５０は外周壁部４３ｂを介して電池缶６０で挟持される。 The gasket 43 is initially formed on the peripheral side edge of the ring-shaped base portion 43a so that the outer peripheral wall portion 43b is substantially vertically erected upward, and the inner peripheral side is substantially downward from the base portion 43a It has a shape having a cylindrical portion 43c vertically suspended. By caulking the battery can 60, the sealing lid 50 is sandwiched by the battery can 60 via the outer peripheral wall 43b.
　電池缶６０の内部には、非水電解液が所定量注入されている。非水電解液の一例としては、リチウム塩がカーボネート系溶媒に溶解した溶液を用いることが好ましい。リチウム塩の例として、フッ化リン酸リチウム（ＬｉＰＦ６）、フッ化ホウ酸リチウム（ＬｉＢＦ６）、等が挙げられる。また、カーボネート系溶媒の例として、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）、プロピレンカーボネート（ＰＣ）、メチルエチルカーボネート（ＭＥＣ）、或いは上記溶媒の１種類以上から選ばれる溶媒を混合したもの、が挙げられる。 A predetermined amount of non-aqueous electrolytic solution is injected into the inside of the battery can 60. As an example of the non-aqueous electrolytic solution, it is preferable to use a solution in which a lithium salt is dissolved in a carbonate-based solvent. Examples of lithium salts include lithium fluorophosphate (LiPF6), lithium fluoroborate (LiBF6), and the like. Further, as an example of the carbonate-based solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl ethyl carbonate (MEC), or a mixture of solvents selected from one or more of the above solvents, Can be mentioned.
　図３は円筒形二次電池１の発電ユニットを示す図である。この図３では、電極群１０の構造の詳細を示し、一部を切断した状態の斜視図を示す。図３に図示されるように、電極群１０は、軸芯１５の外周に、正極電極１１、負極電極１２、および第１、第２のセパレータ１３、１４が捲回された構成を有する。 FIG. 3 is a view showing a power generation unit of the cylindrical secondary battery 1. In this FIG. 3, the detail of the structure of the electrode group 10 is shown, and the perspective view of the state which cut | disconnected one part is shown. As illustrated in FIG. 3, the electrode group 10 has a configuration in which the positive electrode 11, the negative electrode 12, and the first and second separators 13 and 14 are wound around the outer periphery of the shaft core 15.
　この電極群１０では、軸芯１５の外周に接する最内周には第１のセパレータ１３が捲回され、その外側を、負極電極１２、第２のセパレータ１４および正極電極１１が、この順に積層され、捲回されている。最内周の負極電極１２の内側には第１のセパレータ１３および第２のセパレータ１４が数周捲回されている。また、最外周は負極電極１２およびその外周に捲回された第１のセパレータ１３となっている。 In this electrode group 10, the first separator 13 is wound around the innermost periphery in contact with the outer periphery of the shaft core 15, and the negative electrode 12, the second separator 14 and the positive electrode 11 are laminated in this order on the outside It has been rolled up. A first separator 13 and a second separator 14 are wound several turns inside the innermost negative electrode 12. The outermost periphery is a negative electrode 12 and a first separator 13 wound around the outer periphery.
　正極電極１１は、アルミニウム箔により形成され長尺な形状を有し、正極シート１１ａと、この正極シート１１ａの両面に正極合剤１１ｂが塗布された正極処理部を有する。正極シート１１ａの長手方向に沿った上方側の側縁は、正極合剤１１ｂが塗布されずアルミニウム箔が露出した正極合剤未処理部１１ｃとなっている。この正極合剤未処理部１１ｃには、軸芯１５と平行に上方に突き出す多数の正極リード１６が等間隔に一体的に形成されている。 The positive electrode 11 is formed of aluminum foil and has a long shape, and includes a positive electrode sheet 11 a and a positive electrode processing portion in which a positive electrode mixture 11 b is applied to both surfaces of the positive electrode sheet 11 a. The upper side edge along the longitudinal direction of the positive electrode sheet 11a is a positive electrode mixture non-treated portion 11c in which the positive electrode mixture 11b is not applied and the aluminum foil is exposed. In the positive electrode mixture non-treated portion 11c, a large number of positive electrode leads 16 projecting upward in parallel with the shaft core 15 are integrally formed at equal intervals.
　正極合剤１１ｂは、正極活物質と、正極導電剤と、正極バインダと、正極ガス発生化合物（ガス発生剤）とからなる。このうち、正極導電材は、正極合剤中におけるリチウムの吸蔵放出反応で生じた電子の正極電極への伝達を補助できるものであれば制限は無い。正極導電材の例として、黒鉛やアセチレンブラックなどが挙げられる。 The positive electrode mixture 11 b is composed of a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a positive electrode gas generating compound (gas generating agent). Among them, the positive electrode conductive material is not limited as long as it can assist the transfer of electrons generated by the lithium storage and release reaction in the positive electrode mixture to the positive electrode. Examples of the positive electrode conductive material include graphite and acetylene black.
　正極バインダは、正極活物質を正極導電材に結着させ、また正極合剤を正極集電体に結着させることが可能であり、非水電解液との接触により、大幅に劣化しなければ特に制限はない。正極バインダの例としてポリフッ化ビニリデン（ＰＶＤＦ）やフッ素ゴムなどが挙げられる。 The positive electrode binder can bind the positive electrode active material to the positive electrode conductive material and can bind the positive electrode mixture to the positive electrode current collector, unless it is significantly degraded by contact with the non-aqueous electrolyte. There is no particular restriction. Examples of the positive electrode binder include polyvinylidene fluoride (PVDF) and fluororubber.
　正極ガス発生化合物としては、過充電状態の正極電位においてガス発生をする炭酸無機化合物、蓚酸無機化合物、又は、硝酸無機化合物が挙げられる。中でも、炭酸無機化合物が好ましく、例えば炭酸リチウムが挙げられる。 Examples of the positive electrode gas generating compound include a carbonic acid inorganic compound, an oxalic acid inorganic compound, and a nitric acid inorganic compound which generate gas at the positive electrode potential in the overcharged state. Among them, inorganic carbonated compounds are preferable, and examples thereof include lithium carbonate.
　正極合剤層の形成方法は、正極電極上に正極合剤が形成される方法であれば制限はない。正極合剤１１ｂの形成方法の例として、正極合剤１１ｂの構成物質の分散溶液を正極シート１１ａ上に塗布する方法が挙げられる。 The method of forming the positive electrode mixture layer is not limited as long as the positive electrode mixture is formed on the positive electrode. As an example of the formation method of the positive electrode mixture 11b, a method of applying a dispersion solution of the constituent material of the positive electrode mixture 11b on the positive electrode sheet 11a can be mentioned.
　正極合剤１１ｂを正極シート１１ａに塗布する方法の例として、ロール塗工法、スリットダイ塗工法等が挙げられる。正極合剤１１ｂに分散溶液の溶媒例として、Ｎ－メチルピロリドン（ＮＭＰ）や水等を添加し、混練したスラリを、厚さ２０μｍのアルミニウム箔の両面に均一に塗布し、乾燥させた後、プレスして裁断する。正極合剤１１ｂの塗布厚さの一例としては片側約４０μｍである。正極シート１１ａを裁断する際、正極リード１６を一体的に形成する。 Examples of a method of applying the positive electrode mixture 11b to the positive electrode sheet 11a include a roll coating method, a slit die coating method, and the like. N-methyl pyrrolidone (NMP), water or the like is added to the positive electrode mixture 11b as a solvent example of the dispersion solution, and a kneaded slurry is uniformly coated on both sides of a 20 μm thick aluminum foil and dried. Press and cut. An example of the coating thickness of the positive electrode mixture 11 b is about 40 μm on one side. When cutting the positive electrode sheet 11a, the positive electrode lead 16 is integrally formed.
　負極電極１２は、銅箔により形成され長尺な形状を有し、負極シート１２ａと、この負極シート１２ａの両面に負極合剤１２ｂが塗布された負極処理部を有する。負極シート１２ａの長手方向に沿った下方側の側縁は、負極合剤１２ｂが塗布されず銅箔が露出した負極合剤未処理部１２ｃとなっている。この負極合剤未処理部１２ｃには、正極リード１６とは反対方向に延出された、多数の負極リード１７が等間隔に一体的に形成されている。 The negative electrode 12 is formed of a copper foil and has a long shape, and has a negative electrode sheet 12a and a negative electrode processing portion in which a negative electrode mixture 12b is applied to both surfaces of the negative electrode sheet 12a. The lower side edge along the longitudinal direction of the negative electrode sheet 12 a is a negative electrode mixture non-treated portion 12 c in which the negative electrode mixture 12 b is not applied and the copper foil is exposed. In the negative electrode mixture non-treated portion 12c, a large number of negative electrode leads 17 extending in the opposite direction to the positive electrode lead 16 are integrally formed at equal intervals.
　負極合剤１２ｂは、負極活物質と、負極バインダと、増粘剤とからなる。負極活物質として黒鉛炭素を用いることにより、大容量が要求されるプラグインハイブリッド自動車や電気自動車向けのリチウムイオン二次電池が作製できる。負極合剤１２ｂの形成方法は、負極シート１２ａ上に負極合剤１２ｂが形成される方法であれば制限はない。負極合剤１２ｂを負極シート１２ａに塗布する方法の例として、負極合剤１２ｂの構成物質の分散溶液を負極シート１２ａ上に塗布する方法が挙げられる。塗布方法の例として、ロール塗工法、スリットダイ塗工法等が挙げられる。 The negative electrode mixture 12 b is composed of a negative electrode active material, a negative electrode binder, and a thickener. By using graphite carbon as the negative electrode active material, a lithium ion secondary battery for a plug-in hybrid car or an electric car that requires a large capacity can be manufactured. The method of forming the negative electrode mixture 12b is not limited as long as the negative electrode mixture 12b is formed on the negative electrode sheet 12a. As an example of the method of apply | coating the negative mix 12b to the negative electrode sheet 12a, the method of apply | coating the dispersion solution of the constituent of the negative mix 12b on the negative electrode sheet 12a is mentioned. Examples of the coating method include a roll coating method and a slit die coating method.
　負極合剤１２ｂを負極シート１２ａに塗布する方法の例として、負極合剤１２ｂに分散溶媒としてＮ－メチル－２－ピロリドンや水を添加し、混練したスラリを、厚さ１０μｍの圧延銅箔の両面に均一に塗布し、乾燥させた後、プレスして裁断する。負極合剤１２ｂの塗布厚さの一例としては片側約４０μｍである。負極シート１２ａを裁断する際、負極リード１７を一体的に形成する。 As an example of a method of applying the negative electrode mixture 12b to the negative electrode sheet 12a, a slurry obtained by adding N-methyl-2-pyrrolidone or water as a dispersion solvent to the negative electrode mixture 12b and kneading the mixture is used to form a rolled copper foil having a thickness of 10 μm. After applying uniformly on both sides and drying, it is pressed and cut. An example of the coating thickness of the negative electrode mixture 12 b is about 40 μm on one side. When cutting the negative electrode sheet 12a, the negative electrode lead 17 is integrally formed.
　第１のセパレータ１３および第２のセパレータ１４の幅をＷS、負極シート１２ａに形成される負極合剤１２ｂの幅をＷC、正極シート１１ａに形成される正極合剤１１ｂの幅をＷAとした場合、下記の式（１）を満足するように形成される。
　　　　　　ＷS＞ＷC＞ＷA　　　　　　（１） When the width of the first separator 13 and the second separator 14 is WS, the width of the negative electrode mixture 12b formed on the negative electrode sheet 12a is WC, and the width of the positive electrode mixture 11b formed on the positive electrode sheet 11a is WA , And are formed to satisfy the following equation (1).
WS>WC> WA (1)
　すなわち、正極合剤１１ｂの幅ＷAよりも、常に、負極合剤１２ｂの幅ＷCが大きい。これは、リチウムイオン二次電池の場合、正極活物質であるリチウムがイオン化してセパレータを浸透するが、負極側に負極活物質が形成されておらず負極シート１２ａが露出していると負極シート１２ａにリチウムが析出し、内部短絡を発生する原因となるからである。 That is, the width WC of the negative electrode mixture 12b is always larger than the width WA of the positive electrode mixture 11b. This is because in the case of a lithium ion secondary battery, lithium, which is a positive electrode active material, is ionized to permeate the separator, but when the negative electrode active material is not formed on the negative electrode side and the negative electrode sheet 12a is exposed, the negative electrode sheet It is because lithium precipitates on 12a and causes an internal short circuit.
［角形二次電池の構成］
　図４～図６は、角形二次電池１００の構成の一例を示す図である。
　図４は角形二次電池１００の外観斜視図である。図４に示すように、角形二次電池１００は、電池缶１０１と電池蓋１０２とからなる電池容器を備えている。電池缶１０１および電池蓋１０２の材質は、アルミニウムまたはアルミニウム合金などである。電池缶１０１は、深絞り加工を施すことによって、一端が開口された扁平な矩形箱状に形成されている。電池缶１０１は、矩形平板状の底板１０１ｃと、底板１０１ｃの一対の長辺部のそれぞれから立ち上がる一対の幅広側板１０１ａと、底板１０１ｃの一対の短辺部のそれぞれから立ち上がる一対の幅狭側板１０１ｂとを有している。 [Configuration of square secondary battery]
4 to 6 show an example of the configuration of the prismatic secondary battery 100. FIG.
FIG. 4 is an external perspective view of the prismatic secondary battery 100. As shown in FIG. 4, the prismatic secondary battery 100 includes a battery case including a battery can 101 and a battery cover 102. The material of the battery can 101 and the battery cover 102 is aluminum or an aluminum alloy. The battery can 101 is formed in a flat rectangular box shape whose one end is opened by deep drawing. The battery can 101 has a rectangular flat bottom plate 101c, a pair of wide side plates 101a rising from each of a pair of long sides of the bottom plate 101c, and a pair of narrow side plates 101b rising from each of a pair of short sides of the bottom plate 101c. And.
　図５は角形二次電池１００の分解斜視図である。図５に示すように、電池缶１０１には捲回電極群１７０（図６参照）が収容されている。捲回電極群１７０の正極電極１７４に接合される正極集電体１８０および捲回電極群１７０の負極電極１７５に接合される。負極集電体１９０ならびに捲回電極群１７０は、捲回電極群１７０の中央部を覆う絶縁シート１０８aと捲回電極群１７０の正極未塗工部を覆う絶縁シート１０８ｂと捲回電極群１７０の負極未塗工部を覆う絶縁シート１０８ｃに覆われた状態で電池缶１０１に収容されている。絶縁シート１０８a、１０８ｂ、１０８ｃの材質は、ポリプロピレン等の絶縁性を有する樹脂であり、電池缶１０１と、捲回電極群１７０とは電気的に絶縁されている。 FIG. 5 is an exploded perspective view of the prismatic secondary battery 100. As shown in FIG. 5, a wound electrode group 170 (see FIG. 6) is accommodated in the battery can 101. The positive electrode current collector 180 joined to the positive electrode 174 of the wound electrode group 170 and the negative electrode 175 of the wound electrode group 170 are joined. In the negative electrode current collector 190 and the wound electrode group 170, the insulating sheet 108 a covering the central portion of the wound electrode group 170 and the insulating sheet 108 b covering the positive electrode uncoated portion of the wound electrode group 170 and the wound electrode group 170. It is accommodated in the battery can 101 in the state covered with the insulating sheet 108c which covers a negative electrode uncoated part. The material of the insulating sheets 108a, 108b and 108c is a resin having an insulating property such as polypropylene, and the battery can 101 and the wound electrode group 170 are electrically insulated.
　図４および図５に示すように、電池蓋１０２は、矩形平板状であって、電池缶１０１の開口を塞ぐようにレーザー溶接されている。つまり、電池蓋１０２は、電池缶１０１の開口を封止している。図４に示すように、電池蓋１０２には、捲回電極群１７０の正極電極１７４および負極電極１７５と電気的に接続された正極外部端子１０４および負極外部端子１０５が配置されている。 As shown in FIG. 4 and FIG. 5, the battery cover 102 has a rectangular flat plate shape and is laser welded so as to close the opening of the battery can 101. That is, the battery cover 102 seals the opening of the battery can 101. As shown in FIG. 4, the battery lid 102 is provided with a positive electrode external terminal 104 and a negative electrode external terminal 105 electrically connected to the positive electrode 174 and the negative electrode 175 of the wound electrode group 170.
　図５に示すように、正極外部端子１０４は電流遮断機構１８１と正極集電体１８０を介して捲回電極群１７０の正極電極１７４（図６参照）に電気的に接続され、負極外部端子１０５は負極集電体１９０を介して捲回電極群１７０の負極電極１７５に電気的に接続されている。このため、正極外部端子１０４および負極外部端子１０５を介して外部機器に電力が供給され、あるいは、正極外部端子１０４および負極外部端子１０５を介して外部発電電力が捲回電極群１７０に供給されて充電される。 As shown in FIG. 5, the positive electrode external terminal 104 is electrically connected to the positive electrode 174 (see FIG. 6) of the wound electrode group 170 via the current blocking mechanism 181 and the positive electrode current collector 180. Are electrically connected to the negative electrode 175 of the wound electrode group 170 via the negative electrode current collector 190. Therefore, power is supplied to the external device through the positive electrode external terminal 104 and the negative electrode external terminal 105, or externally generated power is supplied to the wound electrode group 170 through the positive electrode external terminal 104 and the negative electrode external terminal 105. Be charged.
　図５に示すように、電池蓋１０２には、電池容器内に電解液を注入するための注液孔１０６ａが穿設されている。注液孔１０６ａは、電解液注入後に注液栓１０６ｂによって封止される。電解液としては、たとえば、エチレンカーボネート等の炭酸エステル系の有機溶媒に６フッ化リン酸リチウム（ＬｉＰＦ６）等のリチウム塩が溶解された非水電解液を用いることができる。 As shown in FIG. 5, a liquid injection hole 106 a for injecting an electrolytic solution into the battery case is formed in the battery cover 102. The injection hole 106 a is sealed by the injection plug 106 b after the injection of the electrolyte. As the electrolytic solution, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF6) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.
　電池蓋１０２には、ガス排出弁１０３が設けられている。ガス排出弁１０３は、プレス加工によって電池蓋１０２を部分的に薄肉化することで形成されている。なお、薄膜部材を電池蓋１０２の開口にレーザー溶接等により取り付けて、薄肉部分をガス排出弁としてもよい。ガス排出弁１０３は、角形二次電池１００が内部短絡等の異常により発熱してガスが発生し、電池容器内の圧力が上昇して所定圧力に達したときに開裂して、内部からガスを排出することで電池容器内の圧力を低減させる。 The battery cover 102 is provided with a gas discharge valve 103. The gas discharge valve 103 is formed by partially thinning the battery cover 102 by press processing. The thin film member may be attached to the opening of the battery cover 102 by laser welding or the like, and the thin portion may be used as the gas discharge valve. The gas discharge valve 103 generates heat by generating heat due to an abnormality such as an internal short circuit in the prismatic secondary battery 100, and when the pressure in the battery container rises and reaches a predetermined pressure, it is cleaved and the gas is generated from the inside By discharging, the pressure in the battery container is reduced.
　電流遮断機構１８１は、角形二次電池１００が過充電状態となり、そのときの正極電位により正極ガス発生化合物が分解し、分解ガスが発生して、内圧が上昇した場合に作動する。そして、正極外部端子１０４との電気的接続が断たれ、過充電になった場合に安全性を確保する。 The current interrupting mechanism 181 operates when the prismatic secondary battery 100 is overcharged and the positive electrode gas generating compound is decomposed by the positive electrode potential at that time to generate a decomposed gas and raise the internal pressure. Then, the electrical connection with the positive electrode external terminal 104 is cut off, and safety is ensured when the battery is overcharged.
　なお、本発明の実施形態では、過充電時に、ガス発生剤が反応する電位においても、負極に十分な容量を設ける事で、過充電に対して安全性を向上させるものであるが、その詳細については後述する。 In the embodiment of the present invention, the safety against overcharge is improved by providing a sufficient capacity in the negative electrode even at the potential at which the gas generating agent reacts at the time of overcharge, but the details will be described. Will be described later.
　図６は、角形二次電池の捲回電極群１７０を示す斜視図である。図６は、捲回電極群１７０の巻き終り側を展開した状態を示している。発電要素である捲回電極群１７０は、長尺状の正極電極１７４および負極電極１７５をセパレータ１７３ａ，１７３ｂを介在させて捲回中心軸Ｗ周りに扁平形状に捲回することで積層構造とされている。 FIG. 6 is a perspective view showing a wound electrode group 170 of a square secondary battery. FIG. 6 shows a state in which the winding end side of the wound electrode group 170 is developed. The wound electrode group 170, which is a power generation element, has a laminated structure by winding the long positive electrode 174 and the negative electrode 175 in a flat shape around the winding central axis W with the separators 173a and 173b interposed. ing.
　正極電極１７４は、正極箔１７１の両面に正極合剤層１７６が形成されてなる。正極合剤は、正極活物質と、正極導電剤と、結着材（正極バインダ）と、正極ガス発生化合物とが配合されたものである。正極ガス発生化合物としては、過充電状態の正極電位においてガス発生をする炭酸無機化合物、蓚酸無機化合物、又は、硝酸無機化合物が挙げられる。中でも、炭酸無機化合物が好ましく、例えば炭酸リチウムが挙げられる。 The positive electrode 174 is formed by forming a positive electrode mixture layer 176 on both surfaces of the positive electrode foil 171. The positive electrode mixture is a mixture of a positive electrode active material, a positive electrode conductive agent, a binder (positive electrode binder), and a positive electrode gas generating compound. Examples of the positive electrode gas generating compound include a carbonic acid inorganic compound, an oxalic acid inorganic compound, and a nitric acid inorganic compound that generate gas at the positive electrode potential in the overcharged state. Among them, inorganic carbonated compounds are preferable, and examples thereof include lithium carbonate.
　負極電極１７５は、負極箔１７２の両面に負極合剤層１７７が形成されてなる。負極合剤は、負極活物質と、結着材（負極バインダ）と、増粘剤とが配合されたものである。 The negative electrode 175 has a negative electrode mixture layer 177 formed on both sides of the negative electrode foil 172. The negative electrode mixture is a mixture of a negative electrode active material, a binder (negative electrode binder), and a thickener.
　正極箔１７１は、厚さ２０～３０μｍ程度のアルミニウム箔であり、負極箔１７２は、厚さ１５～２０μｍ程度の銅箔である。セパレータ１７３ａ，１７３ｂの素材はリチウムイオンが通過可能な微多孔質のポリエチレン樹脂である。正極活物質はマンガン酸リチウム等のリチウム含有遷移金属複酸化物であり、負極活物質はリチウムイオンを可逆に吸蔵、放出可能な黒鉛等の炭素材である。 The positive electrode foil 171 is an aluminum foil having a thickness of about 20 to 30 μm, and the negative electrode foil 172 is a copper foil having a thickness of about 15 to 20 μm. The material of the separators 173a and 173b is a microporous polyethylene resin through which lithium ions can pass. The positive electrode active material is a lithium-containing transition metal double oxide such as lithium manganate, and the negative electrode active material is a carbon material such as graphite capable of reversibly absorbing and desorbing lithium ions.
　捲回電極群１７０の幅方向、すなわち捲回方向に直交する捲回中心軸Ｗの方向の両端部は、一方が正極電極１７４の積層部とされ、他方が負極電極１７５の積層部とされている。一端に設けられる正極電極１７４の積層部は、正極合剤層１７６が形成されていない正極未塗工部、すなわち正極箔１７１の露出部が積層されたものである。他端に設けられる負極電極１７５の積層部は、負極合剤層１７７が形成されていない負極未塗工部、すなわち負極箔１７２の露出部が積層されたものである。正極未塗工部の積層部および負極未塗工部の積層部は、それぞれ予め押し潰され、それぞれ正極集電体１８０および負極集電体１９０に超音波接合により接続される。 In the width direction of the wound electrode group 170, that is, both ends in the direction of the wound central axis W orthogonal to the winding direction, one is a laminated portion of the positive electrode 174 and the other is a laminated portion of the negative electrode 175 There is. The laminated portion of the positive electrode 174 provided at one end is obtained by laminating the positive uncoated portion on which the positive electrode mixture layer 176 is not formed, that is, the exposed portion of the positive electrode foil 171. The laminated portion of the negative electrode 175 provided at the other end is obtained by laminating the uncoated portion of the negative electrode where the negative electrode mixture layer 177 is not formed, that is, the exposed portion of the negative electrode foil 172. The laminated portion of the positive electrode uncoated portion and the laminated portion of the negative electrode uncoated portion are respectively crushed in advance, and connected to the positive electrode current collector 180 and the negative electrode current collector 190 by ultrasonic bonding.
［第１の実施形態］
　上述した円筒形二次電池、角形二次電池に適用した本発明の第１の実施形態について、図７乃至図８を参照して説明する。 First Embodiment
A first embodiment of the present invention applied to the above-described cylindrical secondary battery and square secondary battery will be described with reference to FIGS. 7 to 8.
　上述した円筒形二次電池、角形二次電池は、密閉型非水電解質の二次電池である。この二次電池は、正極合剤層を備えた正極と、負極合剤層を備えた負極と、所定の電池電圧を超えた場合に分解ガスを発生するガス発生剤が添加された非水電解質と、が電池ケース内に収容され、過充電時に分解ガスの発生に伴って電池ケース内の圧力が上昇した際に作動する電流遮断機構を備える。ガス発生剤として、炭酸リチウムを正極電極に含有する。 The above-described cylindrical secondary battery and prismatic secondary battery are sealed non-aqueous electrolyte secondary batteries. The secondary battery comprises a positive electrode having a positive electrode mixture layer, a negative electrode having a negative electrode mixture layer, and a non-aqueous electrolyte to which a gas generating agent is added that generates a decomposition gas when the battery voltage exceeds a predetermined voltage. And a current blocking mechanism that is accommodated in the battery case and that operates when the pressure in the battery case rises with the generation of decomposition gas during overcharge. Lithium carbonate is contained in the positive electrode as a gas generating agent.
　従来における二次電池は、過充電時にガス発生剤が反応し、電流遮断機構が作動するまでの過充電容量よりも、過充電負極容量が小さい場合には、負極電極表面にリチウムが析出して、セパレータを突き破り、正負極間が短絡して、二次電池が破損する虞がある。 In the conventional secondary battery, when the overcharge negative electrode capacity is smaller than the overcharge capacity until the current interrupting mechanism operates, the gas generating agent reacts at the time of overcharge, lithium is precipitated on the surface of the negative electrode The separator may be broken, and the positive and negative electrodes may be short-circuited to damage the secondary battery.
　そして、添加されるガス発生剤の量が少な過ぎれば、過充電時におけるガス発生量が少なくなり、電流遮断機構が正常に作動しない場合がある。一方で、電流遮断機構の信頼性を重視するあまり、ガス発生剤を過剰に添加すると二次電池の性能が低下する。これは、ガス発生剤は、本来使用される電圧範囲においては、充放電反応には寄与せず、二次電池の抵抗成分となる為である。 If the amount of the gas generating agent to be added is too small, the amount of gas generation at the time of overcharging may be small, and the current interruption mechanism may not operate properly. On the other hand, too much emphasis is placed on the reliability of the current blocking mechanism, and if the gas generating agent is excessively added, the performance of the secondary battery is degraded. This is because the gas generating agent does not contribute to the charge / discharge reaction in the voltage range originally used, and becomes a resistance component of the secondary battery.
　本実施形態における二次電池は、過充電時にガス発生剤（正極ガス発生化合物）が反応し、電流遮断機構が作動するまで過充電容量よりも、過充電負極容量を大きく設定した。これにより、過充電時に負極電極表面にリチウムが析出するのを抑制でき、二次電池の安全性を確保できる。 In the secondary battery in the present embodiment, the overcharge negative electrode capacity is set larger than the overcharge capacity until the gas generating agent (positive electrode gas generating compound) reacts during overcharge and the current interruption mechanism operates. As a result, precipitation of lithium on the surface of the negative electrode during overcharge can be suppressed, and the safety of the secondary battery can be secured.
　また、本実施形態における二次電池は、ガス発生剤が反応し、電流遮断機構が作動するまでの充電容量を負極が十分に確保できるため、ガス発生剤を過剰に添加することはなく、二次電池の性能を低下させない。 Further, the secondary battery in the present embodiment does not add an excessive amount of the gas generating agent, because the negative electrode can sufficiently secure the charge capacity until the gas generating agent reacts and the current blocking mechanism operates. Does not reduce the performance of the secondary battery.
　図７は本実施形態における二次電池の電位と容量の関係を示すグラフである。この図７では、縦軸に二次電池の正極および負極電位（V）と電池電圧（V）を、横軸に容量（mAh）を示している。 FIG. 7 is a graph showing the relationship between the potential and the capacity of the secondary battery in the present embodiment. In FIG. 7, the vertical axis indicates the positive electrode and negative electrode potential (V) and the battery voltage (V) of the secondary battery, and the horizontal axis indicates the capacity (mAh).
　図７のａ１で示す点線は負極初回充電容量Qncの変化を、ａ２で示す実線は負極初回放電容量Qndの変化を表す。これらの変化は環境温度２５℃における以下の充放電試験に基づくものである。 The dotted line indicated by a1 in FIG. 7 indicates the change of the negative electrode initial charge capacity Qnc, and the solid line indicated by a2 indicates the change of the negative electrode initial discharge capacity Qnd. These changes are based on the following charge / discharge test at an ambient temperature of 25 ° C.
　図中のａ１に示す負極初回充電容量Qncの変化は、負極をＳＯＣ０％未満から徐々に充電し、ＳＯＣ０％を超えて更に充電し、ＳＯＣ１００％を超えて更に充電して、ガス発生剤の反応電位を超えるまで充電した場合を示している。具体的には、リチウム金属に対する電位が１．６Vから０．００５V（負極の充電終止電圧）になるまで、０．２C（C はCapacityレートであり、電池容量に対する放電電流値の相対的な比率）の電流で定電流充電し、続いて、０．００５Vの電圧に到達後、０．００５Vの定電圧で２時間充電する。負極はガス発生剤の反応電位を超える充電容量に設定する。換言すれば、後述するように、負極の過充電負極容量Qnocを二次電池の過充電容量Qcocよりも大きく設定する。 The change in negative electrode initial charge capacity Qnc shown in a1 in the figure gradually charges the negative electrode from less than 0% of SOC, further charges it more than 0% of SOC, and further charges it more than 100% of SOC to react the gas generating agent The case where it charges until it exceeds electric potential is shown. Specifically, 0.2 C (C is the capacity rate, and the relative ratio of the discharge current value to the battery capacity) until the potential with respect to lithium metal falls from 1.6 V to 0.005 V (negative charge termination voltage) Constant current charge with a current of (2) followed by charge for 2 hours with a constant voltage of 0.005 V after reaching a voltage of 0.005 V. The negative electrode is set to a charge capacity exceeding the reaction potential of the gas generating agent. In other words, as described later, the overcharge negative electrode capacity Qnoc of the negative electrode is set larger than the overcharge capacity Qcoc of the secondary battery.
　図７のａ２に示す負極初回放電容量Qndの変化は、負極をガス発生剤の反応電位を超える充電容量からＳＯＣ１００％へ徐々に放電し、ＳＯＣ０％まで放電した場合を示している。具体的には、リチウム金属に対する電位が０．００５Vから１．６V（負極の放電終止電圧）になるまで、０．２Cの電流で定電流放電する。 The change in the negative electrode initial discharge capacity Qnd shown in a2 of FIG. 7 shows the case where the negative electrode is gradually discharged from the charge capacity exceeding the reaction potential of the gas generating agent to 100% SOC and discharged to SOC 0%. Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 0.005 V to 1.6 V (discharge termination voltage of the negative electrode).
　負極不可逆容量Qnfは、負極初回充電容量Qncの初期容量から負極初回放電容量Qndの初期容量を引いた容量である。負極不可逆容量Qnfとは、初回充電時に負極表面におけるSEI（Solid.　State Interphase）被膜の形成に消費される電気量と、結晶構造内にトラップされて放電できない電気量の差である。負極可逆容量Qnkは、ガス発生剤の反応電位を超える容量から負極不可逆容量Qnfを引いた容量である。 The negative electrode irreversible capacity Qnf is a capacity obtained by subtracting the initial capacity of the negative electrode first discharge capacity Qnd from the initial capacity of the negative electrode initial charge capacity Qnc. The negative electrode irreversible capacity Qnf is a difference between the amount of electricity consumed for forming a solid. State interphase (SEI) film on the surface of the negative electrode at the time of initial charge and the amount of electricity trapped in the crystal structure and unable to be discharged. The negative electrode reversible capacity Qnk is a capacity obtained by subtracting the negative electrode irreversible capacity Qnf from the capacity exceeding the reaction potential of the gas generating agent.
　ここで負極の充電終止電圧は、リチウム金属を基準として、０．００５V以上、０．０１０V以下が好ましい。負極の放電終止電圧は、リチウム金属を基準として、１．５V以上、１．６V以下が好ましい。 Here, the charge termination voltage of the negative electrode is preferably 0.005 V or more and 0.010 V or less based on lithium metal. The discharge termination voltage of the negative electrode is preferably 1.5 V or more and 1.6 V or less based on lithium metal.
　図７のｂ１で示す点線は正極初回充電容量Qpcの変化を、ｂ２で示す実線は正極初回放電容量Qpdの変化を表す。これらの変化は環境温度２５℃における以下の充放電試験に基づくものである。 The dotted line indicated by b1 in FIG. 7 represents a change in positive electrode initial charge capacity Qpc, and the solid line indicated by b2 represents a change in positive electrode initial discharge capacity Qpd. These changes are based on the following charge / discharge test at an ambient temperature of 25 ° C.
　図中のｂ１に示す正極初回充電容量Qpcの変化は、正極をＳＯＣ０％未満から徐々に充電し、ＳＯＣ０％を超えて充電し、ＳＯＣ１００％の電位４．３Vまで充電した場合を示している。具体的には、リチウム金属に対する電位が３．０VからＳＯＣ１００％に対応する４．３V（正極の充電終止電圧）になるまで、０．２Cの電流で定電流充電し、続いて、４．３Vの電圧に到達後、４．３Vの定電圧で２時間充電する。なお、ＳＯＣ１００％を超えて更に充電して、ガス発生剤の反応電位４．８Vまで充電した場合を点線で示している。 The change of the positive electrode initial charge capacity Qpc indicated by b1 in the figure indicates the case where the positive electrode is gradually charged from less than 0% of SOC, charged to more than 0% of SOC, and charged to a potential of 4.3V at 100% of SOC. Specifically, constant current charging is performed with a current of 0.2 C until the potential with respect to lithium metal becomes 4.3 V (positive electrode charge termination voltage) corresponding to 3.0 V to SOC 100%, and then 4.3 V After reaching a voltage of 2, charge for 2 hours with a constant voltage of 4.3V. The dotted line indicates the case where the SOC is further charged up to 100% and charged to the reaction potential of 4.8 V of the gas generating agent.
　図７のｂ２に示す正極初回放電容量Qpdの変化は、正極をＳＯＣ１００％からＳＯＣ０％未満まで放電した場合を示している。具体的には、リチウム金属に対する電位が４．３Vから３．０V（正極の放電終止電圧）になるまで、０．２Cの電流で定電流放電する。 The change of the positive electrode initial discharge capacity Qpd shown in b2 of FIG. 7 shows the case where the positive electrode is discharged from SOC 100% to less than SOC 0%. Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 4.3 V to 3.0 V (the discharge final voltage of the positive electrode).
　正極不可逆容量Qpfは、正極初回充電容量Qpcの初期容量から正極初回放電容量Qpdの初期容量を引いた容量である。正極不可逆容量Qpfとは、放電末期の結晶構造内へのリチウム吸蔵の拡散速度が遅いことに起因して生じる。正極可逆容量Qpkは、ＳＯＣ１００％の時の容量から正極不可逆容量Qpfを引いた容量である。 The positive electrode irreversible capacity Qpf is a capacity obtained by subtracting the initial capacity of the positive electrode first discharge capacity Qpd from the initial capacity of the positive electrode initial charge capacity Qpc. The positive electrode irreversible capacity Qpf is generated due to the slow diffusion rate of lithium absorption into the crystal structure at the end of discharge. The positive electrode reversible capacity Qpk is a capacity obtained by subtracting the positive electrode irreversible capacity Qpf from the capacity at SOC 100%.
　ここで正極の充電終止電圧はリチウム金属を基準として、４．２V以上、４．３V以下が好ましい。正極の放電終止電圧は、リチウム金属を基準として、２．５V以上、３．０V以下が好ましい。 Here, the charge termination voltage of the positive electrode is preferably 4.2 V or more and 4.3 V or less based on lithium metal. The discharge termination voltage of the positive electrode is preferably 2.5 V or more and 3.0 V or less based on lithium metal.
　図７のｄ１で示す実線は電池容量Qcの変化を表す。電池電圧は正極電位と負極電位の差で表される。電池容量QcはSOC０％からSOC１００％間の容量を示す。 The solid line indicated by d1 in FIG. 7 represents the change of the battery capacity Qc. The battery voltage is represented by the difference between the positive electrode potential and the negative electrode potential. The battery capacity Qc indicates a capacity between SOC 0% and SOC 100%.
　ここでSOCとは、可逆的に充放電可能な作動電圧の範囲において、その上限となる電圧が得られる充電状態、即ち満充電状態をSOC１００％とし、下限となる電圧が得られる状態をSOC０％とした時の充電状態を示すものである。通常、二次電池はSOC０％からSOC１００％の間で使用される。 Here, SOC means a state of charge where an upper limit voltage can be obtained within the range of reversibly chargeable and dischargeable operating voltage, that is, a fully charged state is SOC 100% and a state where a lower limit voltage is obtained is SOC 0% It shows the state of charge when. Usually, secondary batteries are used between SOC 0% and SOC 100%.
　SOC１００％は電池電圧が４．２V（電池の充電終止電圧）になるまで、１Cの電流で定電流充電し、続いて４．２Vの電圧に到達後、４．２Vの定電圧で２時間充電した状態である。SOC０％は、電池電圧が２．７V（電池の放電終止電圧）になるまで、１Cの電流で定電流放電した状態である。 The SOC 100% performs constant current charging at a current of 1 C until the battery voltage reaches 4.2 V (battery charge termination voltage), and then, after reaching a voltage of 4.2 V, charging for 2 hours at a constant voltage of 4.2 V It is in a state of SOC 0% is a state in which constant current discharge is performed at a current of 1 C until the battery voltage reaches 2.7 V (discharge final voltage of the battery).
　ここで二次電池の充電終止電圧は、二次電池に過度な負荷がかからず、安全に使用できる電圧であり、４．１V以上、４．３V以下が好ましい。二次電池の放電終止電圧は、２．５V以上、３．０V以下が好ましい。 Here, the charge termination voltage of the secondary battery is a voltage that can be safely used without causing an excessive load on the secondary battery, and is preferably 4.1 V or more and 4.3 V or less. The discharge end voltage of the secondary battery is preferably 2.5 V or more and 3.0 V or less.
　図７のｄ２で示す点線は、二次電池の過充電の領域を示す。二次電池の過充電はSOC１００％以上の充電状態をいう。過充電時には、所定の電圧を超えるとガス発生剤が分解し、二次電池の内圧が上昇して、電流遮断機構が作動する。SOC１００％からガス発生剤が反応する電圧までの容量を二次電池の過充電容量Qcocと称する。 The dotted line indicated by d2 in FIG. 7 indicates the overcharge area of the secondary battery. Overcharging of the secondary battery refers to a state of charge of 100% or more of SOC. At the time of overcharging, when the predetermined voltage is exceeded, the gas generating agent is decomposed, the internal pressure of the secondary battery is increased, and the current interrupting mechanism operates. The capacity from SOC 100% to the voltage at which the gas generating agent reacts is referred to as overcharge capacity Qcoc of the secondary battery.
　負極の過充電負極容量Qnocは、SOC１００％から負極電位が０．００５Vに到達するまでの容量である。本実施形態では、負極の過充電負極容量Qnocを二次電池の過充電容量Qcocよりも大きく設定する。仮に、過充電負極容量Qnocが過充電容量Qcocよりも小さい場合には、過充電時において電流遮断機構が作動する前に、負極電極表面にリチウムが析出して、正負極を分離しているセパレータを突き破り、正負極間が短絡して、二次電池が破損する虞がある。 The overcharged negative electrode capacity Qnoc of the negative electrode is a capacity from 100% of SOC to when the negative electrode potential reaches 0.005V. In the present embodiment, the overcharge negative electrode capacity Qnoc of the negative electrode is set larger than the overcharge capacity Qcoc of the secondary battery. If the overcharge negative electrode capacity Qnoc is smaller than the overcharge capacity Qcoc, lithium is deposited on the surface of the negative electrode before the current interrupting mechanism operates during overcharge, thereby separating the positive and negative electrodes. As a result, the positive and negative electrodes may be short-circuited, which may damage the secondary battery.
（正極合剤）
　上記の通り、正極合剤は正極活物質と、正極導電材と、正極バインダと、正極ガス発生化合物からなる。正極活物質はリチウム酸化物が好ましい。例として、コバルト酸リチウム、マンガン酸リチウム、ニッケル酸リチウム、リチウム複合酸化物（コバルト、ニッケル、マンガンから選ばれる２種類以上を含むリチウム酸化物）等が挙げられる。本実施形態ではコバルト、ニッケル、マンガンを含むリチウム酸化物を使用した。 (Positive mix)
As described above, the positive electrode mixture includes the positive electrode active material, the positive electrode conductive material, the positive electrode binder, and the positive electrode gas generating compound. The positive electrode active material is preferably lithium oxide. Examples thereof include lithium cobaltate, lithium manganate, lithium nickelate, lithium complex oxide (lithium oxide containing two or more types selected from cobalt, nickel and manganese) and the like. In this embodiment, lithium oxide containing cobalt, nickel and manganese was used.
　正極合剤には、過充電時の安全性を確保するために、ガス発生化合物を添加することが好ましい。ガス発生化合物としては、過充電状態の正極電位においてガス発生をする炭酸無機化合物、蓚酸無機化合物、又は、硝酸無機化合物が挙げられる。中でも、炭酸無機化合物が好ましく、例えば炭酸リチウムが挙げられる。実施例１では、炭酸リチウムを正極電極に含有した。炭酸リチウムはリチウム金属を基準として、４．８V以上の電位で反応し、ガスを発生する。 It is preferable to add a gas-generating compound to the positive electrode mixture in order to ensure safety during overcharge. Examples of the gas generating compound include a carbonic acid inorganic compound, a boric acid inorganic compound, and a nitric acid inorganic compound that generate gas at the positive electrode potential in the overcharged state. Among them, inorganic carbonated compounds are preferable, and examples thereof include lithium carbonate. In Example 1, lithium carbonate was contained in the positive electrode. Lithium carbonate reacts at a potential of 4.8 V or more with respect to lithium metal to generate gas.
（負極合剤）
　上記の通り、負極合剤は、負極活物質と、負極バインダと、増粘剤とからなる。負極合剤は、アセチレンブラックなどの負極導電材を有しても良い。負極活物質としては、黒鉛炭素を用いることが好ましい。例えば、天然黒鉛、人造黒鉛、難黒鉛化炭素（ハードカーボン）、易黒鉛化炭素（ソフトカーボン）、酸化ケイ素（例えばSiO、SiO２）である。負極合剤に用いられる活物質はこれらの一種または二種以上を使用する。本実施形態では、天然黒鉛を使用した。 (Negative mix)
As described above, the negative electrode mixture comprises the negative electrode active material, the negative electrode binder, and the thickener. The negative electrode mixture may have a negative electrode conductive material such as acetylene black. Graphite carbon is preferably used as the negative electrode active material. For example, natural graphite, artificial graphite, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), silicon oxide (eg, SiO, SiO 2 ). The active material used for negative mix is used 1 type, or 2 or more types of these. In the present embodiment, natural graphite was used.
　次に、本実施形態におけるリチウムイオン二次電池の正極電極と負極電極の容量について説明する。二次電池は、図７に示す充放電試験で測定された正極容量をもつ正極電極と、図７に示す充放電試験で測定された負極容量をもつ負極電極で構成されている。 Next, the capacities of the positive electrode and the negative electrode of the lithium ion secondary battery in the present embodiment will be described. The secondary battery is composed of a positive electrode having a positive electrode capacity measured in the charge and discharge test shown in FIG. 7 and a negative electrode having a negative electrode capacity measured in the charge and discharge test shown in FIG.
　正極電極は、正極活物質の正極初回充電容量が175mAh/gであり、正極活物質が塗布された正極電極の単位面積あたりの正極初回充電容量が1.82mAh/cm2であり、正極電極の単位面積当たりの正極可逆容量が1.60mAh/cm2であり、かつ正極電極の単位面積当たりの正極不可逆容量が0.22mAh/cm2である。 The positive electrode initial charge capacity of the positive electrode active material is 175 mAh / g, the positive electrode initial charge capacity per unit area of the positive electrode coated with the positive electrode active material is 1.82 mAh / cm 2, and the unit area of the positive electrode is The positive electrode reversible capacity per unit area is 1.60 mAh / cm 2, and the positive electrode irreversible capacity per unit area of the positive electrode is 0.22 mAh / cm 2.
　正極電極と対向する負極電極は、負極活物質の負極初回充電容量が360mAh/gであり、負極活物質が塗布された負極電極の単位面積当たりの負極初回充電容量が2.72mAh/cm2であり、負極電極の単位面積当たりの負極可逆容量が2.45mAh/cm2であり、かつ負極電極の単位面積あたりの負極不可逆容量が0.27mAh/cm2である。 The negative electrode initial charge capacity of the negative electrode active material is 360 mAh / g, and the negative electrode initial charge capacity per unit area of the negative electrode coated with the negative electrode active material is 2.72 mAh / cm 2. The negative electrode reversible capacity per unit area of the negative electrode is 2.45 mAh / cm 2, and the negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
　本実施形態におけるリチウムイオン二次電池は、このような正極電極と負極電極で構成される。なお、このリチウムイオン二次電池では、負極電極の単位面積当たりの不可逆容量が、正極電極の不可逆容量よりも大きいため、電池電圧が２．７Vになるまで、１Cの電流で定電流放電した時の電池電圧の低下は負極電極に起因する。 The lithium ion secondary battery in the present embodiment is configured of such a positive electrode and a negative electrode. In this lithium ion secondary battery, the irreversible capacity per unit area of the negative electrode is larger than the irreversible capacity of the positive electrode, so when constant current discharge is performed at a current of 1 C until the battery voltage reaches 2.7 V. The reduction of the battery voltage is caused by the negative electrode.
　本実施形態では、過充電時に、ガス発生剤が反応する電位においても、負極に十分な容量を設ける。これにより、過充電に対して二次電池の安全性を向上させる。
　具体的には、正極の電位が二次電池の充電終止電圧を超えてガス発生剤の反応電位に達するまでの容量を、負極の電位が二次電池の充電終止電圧を超えて負極の充電終止電圧に達するまでの容量よりも小さくする。換言すれば、過充電負極容量Qnocを、過充電容量Qcocに対する過充電負極容量Qnocの比が１．０以上とする。これにより、過充電時に負極表面上にリチウムが析出するのを抑制し、内部短絡に至ることなく、ガス発生剤が反応して電池内圧が上昇し、電流遮断機構が作動し、過充電時の安全性を向上させることができる。 In the present embodiment, the negative electrode is provided with a sufficient capacity even at the potential at which the gas generating agent reacts during overcharge. This improves the safety of the secondary battery against overcharging.
Specifically, the capacity until the potential of the positive electrode exceeds the charge termination voltage of the secondary battery and reaches the reaction potential of the gas generating agent, and the potential of the negative electrode exceeds the charge termination voltage of the secondary battery and the charge termination of the negative electrode Make it smaller than the capacity to reach the voltage. In other words, the ratio of the overcharged negative electrode capacity Qnoc to the overcharged negative electrode capacity Qcoc is 1.0 or more. As a result, precipitation of lithium on the surface of the negative electrode during overcharge is suppressed, and the gas generating agent reacts to increase the internal pressure of the battery without causing an internal short circuit, and the current blocking mechanism operates, thereby causing overcharge. Safety can be improved.
　図８は、二次電池の電池抵抗の上昇率を示した図である。具体的には、電池容量Qcに対する負極可逆容量Qnkの比（Qnk/Qc）を変えて二次電池のサイクル試験をした時の電池抵抗の上昇率を示した図である。
　サイクル試験は、二次電池を25゜Cの環境下でＳＯＣ30％からＳＯＣ70％になるまでの範囲において、定電流で繰り返し充放電をおこなったものである。 FIG. 8 is a graph showing the rate of increase in battery resistance of the secondary battery. Specifically, it is a diagram showing a rate of increase in battery resistance when the cycle test of the secondary battery is performed by changing the ratio (Qnk / Qc) of the negative electrode reversible capacity Qnk to the battery capacity Qc.
In the cycle test, the secondary battery was repeatedly charged and discharged with constant current in a range from 30% SOC to 70% SOC in an environment of 25 ° C.
　電池抵抗の測定は、二次電池を25゜Cの環境下において、電池電圧を3.7Vに調整して測定した。まず、1Cの定電流で3.7Vまで充電した後、２時間定電圧で充電を行い、次に60Aの電流で放電し、１０秒後の電池抵抗を求めた。電池抵抗は、電流印加前の電圧と１０秒後の電圧の差を印加電流で割ることにより求めた。電池抵抗の上昇率はサイクル試験前後の電池抵抗の割合である。電池抵抗の測定は毎日行い、電池抵抗の上昇率が130%に到達するまでサイクル試験を行った。 The battery resistance was measured by adjusting the battery voltage to 3.7 V in an environment of 25 ° C. of the secondary battery. First, after charging to 3.7 V with a constant current of 1 C, charging was performed with a constant voltage for 2 hours, and then discharging was performed with a current of 60 A, and the battery resistance after 10 seconds was determined. The battery resistance was determined by dividing the difference between the voltage before current application and the voltage after 10 seconds by the applied current. The rate of increase of battery resistance is the ratio of battery resistance before and after the cycle test. The battery resistance was measured daily, and a cycle test was performed until the rate of increase in battery resistance reached 130%.
　図８の横軸は電池容量Qcに対する負極可逆容量Qnkの比（Qnk/Qc）であり、縦軸は電池抵抗の上昇率が130％に到達するまでのサイクル日数（日）である。二次電池の電池容量Qcに対する負極可逆容量Qnkの比（Qnk/Qc）に応じてサイクル日数を図中にプロットした。 The horizontal axis in FIG. 8 is the ratio (Qnk / Qc) of the negative electrode reversible capacity Qnk to the battery capacity Qc, and the vertical axis is the number of cycles until the battery resistance increase rate reaches 130% (days). The cycle days were plotted in the graph according to the ratio (Qnk / Qc) of the negative electrode reversible capacity Qnk to the battery capacity Qc of the secondary battery.
　図８に示すように、電池容量Qcに対する負極可逆容量Qnkの比が高い方が、二次電池のサイクル特性が良いことが分かる。これは、通常使用される電圧範囲で充放電反応を伴う負極活物質量が増えているため、ガス発生剤を過剰に添加することなく、電極の電流負荷が低減し、サイクル特性が向上している為である。 As shown in FIG. 8, it can be seen that the cycle characteristic of the secondary battery is better as the ratio of the negative electrode reversible capacity Qnk to the battery capacity Qc is higher. This is because the mass of the negative electrode active material accompanied by charge and discharge reaction in the voltage range usually used is increased, so the current load on the electrode is reduced and the cycle characteristics are improved without adding the gas generating agent excessively. It is because
　このように、電池容量Qcに対しする負極可逆容量Qnkとの比が高いほど、電池抵抗の上昇が抑制できており、比が１．４以上で飽和傾向にあるが、サイクル特性を安定させるためには、マージンをとって、比が１．５以上であることが望ましい。 As described above, the higher the ratio of the negative electrode reversible capacity Qnk to the battery capacity Qc, the more the increase in the battery resistance can be suppressed, and the ratio tends to be saturated at a ratio of 1.4 or more. Preferably, the ratio is 1.5 or more, taking a margin.
［第２の実施形態］
　上述した円筒形二次電池、角形二次電池に適用した本発明の第２の実施形態について、図９を参照して説明する。 Second Embodiment
A second embodiment of the present invention applied to the above-described cylindrical secondary battery and square secondary battery will be described with reference to FIG.
　上述した円筒形二次電池、角形二次電池は、密閉型非水電解質の二次電池である。本実施形態では、この二次電池は、正極合剤層を備えた正極と、負極合剤層を備えた負極と、所定の電池電圧を超えた場合に分解ガスを発生するガス発生剤が添加された非水電解質と、が電池ケース内に収容され、過充電時に分解ガスの発生に伴って電池ケース内の圧力が上昇した際に作動する電流遮断機構を備える。ガス発生剤として、炭酸リチウムを正極電極に含有する。 The above-described cylindrical secondary battery and prismatic secondary battery are sealed non-aqueous electrolyte secondary batteries. In the present embodiment, the secondary battery includes a positive electrode including a positive electrode mixture layer, a negative electrode including a negative electrode mixture layer, and a gas generating agent that generates a decomposition gas when the battery voltage exceeds a predetermined voltage. The non-aqueous electrolyte as described above is accommodated in the battery case, and is provided with a current interrupting mechanism that operates when the pressure in the battery case rises with the generation of the decomposition gas at the time of overcharging. Lithium carbonate is contained in the positive electrode as a gas generating agent.
　図９は本実施形態における二次電池の電位と容量の関係を示すグラフである。この図９では、縦軸に二次電池の正極および負極電位と電池電圧（V）とを、横軸に容量（mAh）を示している。 FIG. 9 is a graph showing the relationship between the potential and the capacity of the secondary battery in the present embodiment. In FIG. 9, the vertical axis represents the positive and negative electrode potentials of the secondary battery and the battery voltage (V), and the horizontal axis represents the capacity (mAh).
　本実施形態における図９で示す二次電池の電位と容量の関係では、正極不可逆容量Qpfが負極不可逆容量Qnfよりも大きい場合の特性を示している。 The relationship between the potential and the capacity of the secondary battery shown in FIG. 9 in the present embodiment shows characteristics when the positive electrode irreversible capacity Qpf is larger than the negative electrode irreversible capacity Qnf.
　図９のａ３で示す点線は負極初回充電容量Qncの変化を、ａ４で示す実線は負極初回放電容量Qndの変化を表す。図９のｂ３で示す点線は正極初回充電容量Qpcの変化を、ｂ４で示す実線は正極初回放電容量Qpdの変化を表す。図９のｄ３で示す実線は電池容量Qcの変化を表す。図９のｄ４で示す点線は、二次電池の過充電の領域を示す。これらの変化は環境温度２５℃における以下の充放電試験に基づくものである。 The dotted line indicated by a3 in FIG. 9 represents the change in the negative electrode initial charge capacity Qnc, and the solid line indicated by a4 represents the change in the negative electrode initial discharge capacity Qnd. The dotted line indicated by b3 in FIG. 9 represents the change in the positive electrode initial charge capacity Qpc, and the solid line indicated by b4 represents the change in the positive electrode initial discharge capacity Qpd. The solid line indicated by d3 in FIG. 9 represents the change of the battery capacity Qc. The dotted line indicated by d4 in FIG. 9 indicates the overcharge area of the secondary battery. These changes are based on the following charge / discharge test at an ambient temperature of 25 ° C.
　図中のａ３に示す負極初回充電容量Qncの変化は、負極をＳＯＣ０％未満から徐々に充電し、ＳＯＣ０％を超えて更に充電し、ＳＯＣ１００％を超えて更に充電して、ガス発生剤の反応電位を超えるまで充電した場合を示している。具体的には、リチウム金属に対する電位が１．６Vから０．００５V（負極の充電終止電圧）になるまで、０．２Cの電流で定電流充電し、続いて、０．００５Vの電圧に到達後、０．００５Vの定電圧で２時間充電する。負極はガス発生剤の反応電位を超える充電容量に設定する。換言すれば、過充電負極容量Qnocを過充電容量Qcocよりも大きく設定する。 The change in negative electrode initial charge capacity Qnc shown in a3 in the figure gradually charges the negative electrode from less than 0% of SOC, further charges it more than 0% of SOC, and further charges it more than 100% of SOC, the reaction of the gas generating agent The case where it charges until it exceeds electric potential is shown. Specifically, constant current charging is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 1.6 V to 0.005 V (the charge termination voltage of the negative electrode), and after reaching a voltage of 0.005 V , Charge for 2 hours with a constant voltage of 0.005V. The negative electrode is set to a charge capacity exceeding the reaction potential of the gas generating agent. In other words, the overcharge negative electrode capacity Qnoc is set larger than the overcharge capacity Qcoc.
　図９のａ４に示す負極初回放電容量Qndの変化は、負極をガス発生剤の反応電位を超える充電容量からＳＯＣ１００％へ徐々に放電し、ＳＯＣ０％（未満）まで放電した場合を示している。具体的には、リチウム金属に対する電位が０．００５Vから１．６V（負極の放電終止電圧）になるまで、０．２Cの電流で定電流放電する。 The change of the negative electrode initial discharge capacity Qnd shown in a4 of FIG. 9 shows a case where the negative electrode is gradually discharged from the charge capacity exceeding the reaction potential of the gas generating agent to 100% SOC and discharged to SOC 0% (less than). Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 0.005 V to 1.6 V (discharge termination voltage of the negative electrode).
　負極不可逆容量Qnfは、負極初回充電容量Qncの初期容量から負極初回放電容量Qndの初期容量を引いた容量である。負極可逆容量Qnkは、ガス発生剤の反応電位を超える容量から負極不可逆容量Qnfを引いた容量である。 The negative electrode irreversible capacity Qnf is a capacity obtained by subtracting the initial capacity of the negative electrode first discharge capacity Qnd from the initial capacity of the negative electrode initial charge capacity Qnc. The negative electrode reversible capacity Qnk is a capacity obtained by subtracting the negative electrode irreversible capacity Qnf from the capacity exceeding the reaction potential of the gas generating agent.
　ここで負極の充電終止電圧は、リチウム金属を基準として、０．００５V以上、０．０１０V以下が好ましい。負極の放電終止電圧は、リチウム金属を基準として、１．５V以上、１．６V以下が好ましい。 Here, the charge termination voltage of the negative electrode is preferably 0.005 V or more and 0.010 V or less based on lithium metal. The discharge termination voltage of the negative electrode is preferably 1.5 V or more and 1.6 V or less based on lithium metal.
　図９のｂ３で示す点線は正極初回充電容量Qpcの変化を、ｂ４で示す実線は正極初回放電容量Qpdの変化を表す。これらの変化は環境温度２５℃における以下の充放電試験に基づくものである。 The dotted line indicated by b3 in FIG. 9 represents the change in the positive electrode initial charge capacity Qpc, and the solid line indicated by b4 represents the change in the positive electrode initial discharge capacity Qpd. These changes are based on the following charge / discharge test at an ambient temperature of 25 ° C.
　図中のｂ３に示す正極初回充電容量Qpcの変化は、正極をＳＯＣ０％未満から徐々に充電し、ＳＯＣ０％を超えて充電し、ＳＯＣ１００％の電位４．３Vまで充電した場合を示している。具体的には、リチウム金属に対する電位が３．０VからＳＯＣ１００％に対応する４．３V（正極の充電終止電圧）になるまで、０．２Cの電流で定電流充電し、続いて、４．３Vの電圧に到達後、４．３Vの定電圧で２時間充電する。なお、ＳＯＣ１００％を超えて更に充電して、ガス発生剤の反応電位４．８Vまで充電した場合を点線で示している。 The change in the positive electrode initial charge capacity Qpc indicated by b3 in the figure indicates the case where the positive electrode is gradually charged from less than 0% of SOC, charged to more than 0% of SOC, and charged to a potential of 4.3V at 100% of SOC. Specifically, constant current charging is performed with a current of 0.2 C until the potential with respect to lithium metal becomes 4.3 V (positive electrode charge termination voltage) corresponding to 3.0 V to SOC 100%, and then 4.3 V After reaching a voltage of 2, charge for 2 hours with a constant voltage of 4.3V. The dotted line indicates the case where the SOC is further charged up to 100% and charged to the reaction potential of 4.8 V of the gas generating agent.
　図９のｂ４に示す正極初回放電容量Qpdの変化は、正極をＳＯＣ１００％からＳＯＣ０％まで放電した場合を示している。具体的には、リチウム金属に対する電位が４．３Vから３．０V（正極の放電終止電圧）になるまで、０．２Cの電流で定電流放電する。 The change of the positive electrode initial discharge capacity Qpd indicated by b4 in FIG. 9 shows the case where the positive electrode is discharged from SOC 100% to SOC 0%. Specifically, constant current discharge is performed at a current of 0.2 C until the potential with respect to lithium metal becomes from 4.3 V to 3.0 V (the discharge final voltage of the positive electrode).
　正極不可逆容量Qpfは、正極初回充電容量Qpcの初期容量から正極初回放電容量Qpdの初期容量を引いた容量である。正極可逆容量Qpkは、ＳＯＣ１００％の時の容量から正極不可逆容量Qpfを引いた容量である。 The positive electrode irreversible capacity Qpf is a capacity obtained by subtracting the initial capacity of the positive electrode first discharge capacity Qpd from the initial capacity of the positive electrode initial charge capacity Qpc. The positive electrode reversible capacity Qpk is a capacity obtained by subtracting the positive electrode irreversible capacity Qpf from the capacity at SOC 100%.
　ここで正極の充電終止電圧はリチウム金属を基準として、４．２V以上、４．３V以下が好ましい。正極の放電終止電圧は、リチウム金属を基準として、２．５V以上、３．０V以下が好ましい。 Here, the charge termination voltage of the positive electrode is preferably 4.2 V or more and 4.3 V or less based on lithium metal. The discharge termination voltage of the positive electrode is preferably 2.5 V or more and 3.0 V or less based on lithium metal.
　図９のｄ３で示す実線は電池容量Qcの変化を表す。電池電圧は正極電位と負極電位の差で表される。電池容量QcはSOC０％からSOC１００％間の容量を示す。 The solid line indicated by d3 in FIG. 9 represents the change of the battery capacity Qc. The battery voltage is represented by the difference between the positive electrode potential and the negative electrode potential. The battery capacity Qc indicates a capacity between SOC 0% and SOC 100%.
　SOC１００％は電池電圧が４．２V（電池の充電終止電圧）になるまで、１Cの電流で定電流充電し、続いて４．２Vの電圧に到達後、４．２Vの定電圧で２時間充電した状態である。SOC０％は、電池電圧が２．７V（電池の放電終止電圧）になるまで、１Cの電流で定電流放電した状態である。 The SOC 100% performs constant current charging at a current of 1 C until the battery voltage reaches 4.2 V (battery charge termination voltage), and then, after reaching a voltage of 4.2 V, charging for 2 hours at a constant voltage of 4.2 V It is in a state of SOC 0% is a state in which constant current discharge is performed at a current of 1 C until the battery voltage reaches 2.7 V (discharge final voltage of the battery).
　ここで二次電池の充電終止電圧は、二次電池に過度な負荷がかからず、安全に使用できる電圧であり、４．１V以上、４．３V以下が好ましい。二次電池の放電終止電圧は、２．５V以上、３．０V以下が好ましい。 Here, the charge termination voltage of the secondary battery is a voltage that can be safely used without causing an excessive load on the secondary battery, and is preferably 4.1 V or more and 4.3 V or less. The discharge end voltage of the secondary battery is preferably 2.5 V or more and 3.0 V or less.
　図９のｄ４で示す点線は、二次電池の過充電の領域を示す。二次電池の過充電はSOC１００％以上の充電状態をいう。過充電時には、所定の電圧を超えるとガス発生剤が分解し、二次電池の内圧が上昇して、電流遮断機構が作動する。SOC１００％からガス発生剤が反応する電圧までの容量を過充電容量Qcocと称する。 The dotted line indicated by d4 in FIG. 9 indicates the overcharge area of the secondary battery. Overcharging of the secondary battery refers to a state of charge of 100% or more of SOC. At the time of overcharging, when the predetermined voltage is exceeded, the gas generating agent is decomposed, the internal pressure of the secondary battery is increased, and the current interrupting mechanism operates. The capacity from SOC 100% to the voltage at which the gas generating agent reacts is referred to as overcharge capacity Qcoc.
　負極の過充電負極容量Qnocは、SOC１００％から負極電位が０．００５Vに到達するまでの容量である。本実施形態では、負極の過充電負極容量Qnocを二次電池の過充電容量Qcocよりも大きく設定する。さらに、正極の電位が二次電池の充電終止電圧に達するまでの容量である正極可逆容量Qpkと、二次電池の充電終止電圧を超えて、正極の電位がガス発生剤の反応電位に達するまでの容量である過充電容量Qcocとの和が、負極の負極可逆容量Qnkよりも小さく設定する。これにより、ガス発生剤が分解して電流遮断機構が反応するまでの充電容量を負極が十分に受容できるため、ガス発生剤を過剰に添加する必要がない。 The overcharged negative electrode capacity Qnoc of the negative electrode is a capacity from 100% of SOC to when the negative electrode potential reaches 0.005V. In the present embodiment, the overcharge negative electrode capacity Qnoc of the negative electrode is set larger than the overcharge capacity Qcoc of the secondary battery. Furthermore, the positive electrode reversible capacity Qpk, which is the capacity until the potential of the positive electrode reaches the charge termination voltage of the secondary battery, and the charge termination voltage of the secondary battery, until the potential of the positive electrode reaches the reaction potential of the gas generating agent The sum with the overcharge capacity Qcoc, which is the capacity of the above, is set smaller than the negative electrode reversible capacity Qnk of the negative electrode. As a result, the negative electrode can sufficiently receive the charge capacity until the gas generating agent decomposes and the current blocking mechanism reacts, so it is not necessary to add the gas generating agent in excess.
　正極合剤、負極合剤は、第１の実施形態で述べたものと同様であるのでその説明を省略する。 The positive electrode mixture and the negative electrode mixture are the same as those described in the first embodiment, and thus the description thereof is omitted.
　本実施形態におけるリチウムイオン二次電池の正極電極と負極電極の容量について説明する。二次電池は、図９に示す充放電試験で測定された正極容量をもつ正極電極と、図９に示す充放電試験で測定された負極容量をもつ負極電極で構成されている。 The capacity | capacitance of the positive electrode of the lithium ion secondary battery in this embodiment and a negative electrode is demonstrated. The secondary battery is composed of a positive electrode having a positive electrode capacity measured in the charge and discharge test shown in FIG. 9 and a negative electrode having a negative electrode capacity measured in the charge and discharge test shown in FIG.
　正極電極は、正極活物質の正極初回充電容量が180mAh/gであり、正極活物質が塗布された正極電極の単位面積あたりの正極初回充電容量が1.87mAh/cm2であり、正極電極の単位面積当たりの正極可逆容量が1.59mAh/cm2であり、かつ正極電極の単位面積当たりの正極不可逆容量が0.28mAh/cm2である。 The positive electrode initial charge capacity of the positive electrode active material is 180 mAh / g, the positive electrode initial charge capacity per unit area of the positive electrode coated with the positive electrode active material is 1.87 mAh / cm 2, and the unit area of the positive electrode is The positive electrode reversible capacity per unit area is 1.59 mAh / cm 2, and the positive electrode irreversible capacity per unit area of the positive electrode is 0.28 mAh / cm 2.
　正極電極と対向する負極電極は、負極活物質の負極初回充電容量が365mAh/gであり、負極活物質が塗布された負極電極の単位面積当たりの負極初回充電容量が2.75mAh/cm2であり、負極電極の単位面積当たりの負極可逆容量が2.48mAh/cm2であり、かつ負極電極の単位面積あたりの負極不可逆容量が0.27mAh/cm2である。 The negative electrode initial charge capacity of the negative electrode active material is 365 mAh / g, and the negative electrode initial charge capacity per unit area of the negative electrode coated with the negative electrode active material is 2.75 mAh / cm 2. The negative electrode reversible capacity per unit area of the negative electrode is 2.48 mAh / cm 2, and the negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
　本実施形態におけるリチウムイオン二次電池は、このような正極電極と負極電極で構成される。なお、このリチウムイオン二次電池では、正極電極の単位面積当たりの不可逆容量が、負極電極の不可逆容量よりも大きいため、電池電圧が２．７Vになるまで、１Cの電流で定電流放電した時の電池電圧の低下は正極電極に起因する。 The lithium ion secondary battery in the present embodiment is configured of such a positive electrode and a negative electrode. In this lithium ion secondary battery, since the irreversible capacity per unit area of the positive electrode is larger than the irreversible capacity of the negative electrode, constant current discharge at a current of 1 C until the battery voltage becomes 2.7 V The reduction of the battery voltage is caused by the positive electrode.
　本実施形態によれば、過充電時に、ガス発生剤が反応する電位においても、負極に十分な容量を設けることにより、過充電に対して二次電池の安全性を向上させることができる。 According to this embodiment, the safety of the secondary battery against overcharge can be improved by providing a sufficient capacity in the negative electrode even at the potential at which the gas generating agent reacts at the time of overcharge.
　以上説明した実施形態によれば、次の作用効果が得られる。
（１）二次電池１、１００は、正極合剤を有する正極と、負極合剤を有する負極と、正極と負極を収容する電池容器６０と、電池容器６０の内圧が所定の作動圧となったときに、正極と負極の間に流れる電流を遮断する電流遮断機構１８１と、を備え、正極合剤にはガス発生剤が含まれ、正極の電位が二次電池１、１００の充電終止電圧を超えてガス発生剤の反応電位に達するまでの容量を、負極の電位が二次電池１、１００の充電終止電圧を超えて負極の充電終止電圧に達するまでの容量よりも小さくした。これにより、過充電に対する安全性に優れた二次電池を提供することができる。 According to the embodiment described above, the following effects can be obtained.
(1) In the secondary batteries 1 and 100, the internal pressure of the battery container 60 containing the positive electrode having the positive electrode mixture, the negative electrode having the negative electrode mixture, the positive electrode and the negative electrode, and the battery container 60 has a predetermined operating pressure. And a current blocking mechanism 181 for blocking the current flowing between the positive electrode and the negative electrode, and the positive electrode mixture contains a gas generating agent, and the potential of the positive electrode is the charge termination voltage of the secondary battery 1, 100. The capacity until the reaction potential of the gas generating agent is reached is smaller than the capacity until the potential of the negative electrode exceeds the charge termination voltage of the secondary battery 1, 100 to reach the charge termination voltage of the negative electrode. Thereby, a secondary battery excellent in safety against overcharge can be provided.
（２）二次電池１、１００におけるガス発生剤の反応電位は4.8V～5.0Vである。これにより、過充電に対する安全性に優れた二次電池を提供することができる。 (2) The reaction potential of the gas generating agent in the secondary batteries 1 and 100 is 4.8 V to 5.0 V. Thereby, a secondary battery excellent in safety against overcharge can be provided.
（３）二次電池１、１００におけるガス発生剤は炭酸リチウムである。ガス発生剤として、炭酸リチウムを正極電極に含有することにより、過充電に対する安全性に優れた二次電池を提供することができる。 (3) The gas generating agent in the secondary battery 1, 100 is lithium carbonate. By containing lithium carbonate in the positive electrode as a gas generating agent, it is possible to provide a secondary battery excellent in safety against overcharge.
（４）二次電池１、１００における負極の負極活物質は、天然黒鉛、人造黒鉛、難黒鉛化炭素、易黒鉛化炭素、酸化ケイ素の一種または二種以上を混合した。これにより、過充電に対して二次電池の安全性を向上させる。 (4) The negative electrode active material of the negative electrode in the secondary batteries 1 and 100 is one or more of natural graphite, artificial graphite, non-graphitizable carbon, graphitizable carbon, and silicon oxide mixed. This improves the safety of the secondary battery against overcharging.
（５）二次電池１、１００における負極の充電終止電圧は0.01V～0.005Vの範囲である。
これにより、過充電に対して二次電池の安全性を向上させる。 (5) The charge termination voltage of the negative electrode in the secondary battery 1, 100 is in the range of 0.01 V to 0.005 V.
This improves the safety of the secondary battery against overcharging.
（６）二次電池１、１００は、正極の電位が二次電池１、１００の充電終止電圧に達するまでの容量と、二次電池１、１００の充電終止電圧を超えて、正極の電位がガス発生剤の反応電位に達するまでの容量との和が、負極の可逆容量よりも小さい。これにより、ガス発生剤が分解して電流遮断機構が反応するまでの充電容量を負極が十分に受容できるため、ガス発生剤を過剰に添加する必要がない。 (6) The secondary battery 1, 100 has a capacity until the potential of the positive electrode reaches the charge termination voltage of the secondary battery 1, 100 and the charge termination voltage of the secondary battery 1, 100. The sum of the capacity of the gas generating agent until reaching the reaction potential is smaller than the reversible capacity of the negative electrode. As a result, the negative electrode can sufficiently receive the charge capacity until the gas generating agent decomposes and the current blocking mechanism reacts, so it is not necessary to add the gas generating agent in excess.
（７）二次電池１、１００は、二次電池１、１００の電池容量に対する負極の可逆容量の比が1.5以上である。これにより、通常使用される電圧範囲で充放電反応を伴う負極活物質量が増えているため、ガス発生剤を過剰に添加することなく、電極の電流負荷が低減し、サイクル特性が向上する。 (7) In the secondary batteries 1 and 100, the ratio of the reversible capacity of the negative electrode to the battery capacity of the secondary batteries 1 and 100 is 1.5 or more. As a result, since the mass of the negative electrode active material accompanied by charge and discharge reaction in the voltage range normally used is increased, the current load on the electrode is reduced and the cycle characteristics are improved without adding the gas generating agent in excess.
（８）二次電池の正極は、正極活物質が塗布された正極電極の単位面積あたりの正極初回充電容量が1.82mAh/cm2であり、正極電極の単位面積当たりの正極可逆容量が1.60mAh/cm2であり、かつ正極電極の単位面積当たりの正極不可逆容量が0.22mAh/cm2であり、
　二次電池の負極は、負極活物質が塗布された負極電極の単位面積当たりの負極初回充電容量が2.72mAh/cm2であり、負極電極の単位面積当たりの負極可逆容量が2.45mAh/cm2であり、かつ負極電極の単位面積あたりの負極不可逆容量が0.27mAh/cm2である。
　これにより、過充電に対する安全性に優れた二次電池を提供することができる。 (8) The positive electrode first charge capacity per unit area of the positive electrode coated with the positive electrode active material is 1.82 mAh / cm 2, and the positive electrode reversible capacity per unit area of the positive electrode is 1.60 mAh / and the positive electrode irreversible capacity per unit area of the positive electrode is 0.22 mAh / cm 2, and
The negative electrode of the secondary battery has a negative electrode initial charge capacity of 2.72 mAh / cm 2 per unit area of the negative electrode coated with the negative electrode active material, and a negative electrode reversible capacity of 2.45 mAh / cm 2 per unit area of the negative electrode. The negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
Thereby, a secondary battery excellent in safety against overcharge can be provided.
（９）二次電池の正極は、正極活物質が塗布された正極電極の単位面積あたりの正極初回充電容量が1.87mAh/cm2であり、正極電極の単位面積当たりの正極可逆容量が1.59mAh/cm2であり、かつ正極電極の単位面積当たりの正極不可逆容量が0.28mAh/cm2であり、
　二次電池の負極は、負極活物質が塗布された負極電極の単位面積当たりの負極初回充電容量が2.75mAh/cm2であり、負極電極の単位面積当たりの負極可逆容量が2.48mAh/cm2であり、かつ負極電極の単位面積あたりの負極不可逆容量が0.27mAh/cm2である。
　これにより、ガス発生剤が分解して電流遮断機構が反応するまでの充電容量を負極が十分に受容できるため、ガス発生剤を過剰に添加する必要がない。 (9) The positive electrode of the secondary battery has a first charge capacity per unit area of the positive electrode coated with the positive electrode active material of 1.87 mAh / cm 2 and a reversible capacity per unit area of the positive electrode of 1.59 mAh / and the positive electrode irreversible capacity per unit area of the positive electrode is 0.28 mAh / cm 2, and
The negative electrode of the secondary battery has an initial negative charge capacity per unit area of the negative electrode coated with the negative electrode active material of 2.75 mAh / cm 2, and a negative electrode reversible capacity per unit area of the negative electrode of 2.48 mAh / cm 2 The negative electrode irreversible capacity per unit area of the negative electrode is 0.27 mAh / cm 2.
As a result, the negative electrode can sufficiently receive the charge capacity until the gas generating agent decomposes and the current blocking mechanism reacts, so it is not necessary to add the gas generating agent in excess.
　本発明は、上記の実施形態に限定されるものではなく、本発明の特徴を損なわない限り、本発明の技術思想の範囲内で考えられるその他の形態についても、本発明の範囲内に含まれる。 The present invention is not limited to the above-described embodiment, and other forms considered within the scope of the technical idea of the present invention are also included in the scope of the present invention as long as the features of the present invention are not impaired. .
１　円筒形二次電池
１０　電極群
６０　電池缶
５０　蓋
６１　かしめ部
６３　グルービング部
１００　角形二次電池
１０２　電池蓋
１０１ｃ　底板
１０１ａ　幅広側板
１０１ｂ　幅狭側板
１０１　電池缶
１０７　蓋組立体
１７０　捲回電極群
１７４　正極電極
１８０　正極集電体
１７５　負極電極
１０８a　捲回電極群の中央部を覆う絶縁シート
１０８ｂ　捲回電極群の正極未塗工部を覆う絶縁シート
１０８ｃ　捲回電極群の負極未塗工部を覆う絶縁シート
１０４　正極外部端子
１０５　負極外部端子
１８１　電流遮断機構
１０６ａ　注液孔
１０６ｂ　注液栓
１０３　ガス排出弁
１７３ａ，１７３ｂ　セパレータ
１７１　正極箔
１７６　正極合剤層
１７２　負極箔
１７７　負極合剤層 DESCRIPTION OF SYMBOLS 1 cylindrical secondary battery 10 electrode group 60 battery can 50 cover 61 caulking part 63 grooving part 100 square secondary battery 102 battery cover 101 c bottom plate 101 a wide side plate 101 b narrow side plate 101 battery can 107 lid assembly 170 coiled electrode group 174 Positive electrode 180 Positive electrode current collector 175 Negative electrode 108a Insulating sheet 108b covering central part of wound electrode group Insulating sheet 108c covering positive electrode uncoated part of wound electrode group Cover negative electrode uncoated part of wound electrode group Insulating sheet 104 positive electrode external terminal 105 negative electrode external terminal 181 current blocking mechanism 106a injection hole 106b liquid injection plug 103 gas discharge valve 173a, 173b separator 171 positive electrode foil 176 positive electrode mixture layer 172 negative electrode foil 177 negative electrode mixture layer

Claims (9)

  1. 　正極合剤を有する正極と、
    　負極合剤を有する負極と、
    　前記正極と前記負極を収容する電池容器と、
    　前記電池容器の内圧が所定の作動圧となったときに、前記正極と負極の間に流れる電流を遮断する電流遮断機構と、を備える二次電池であって、
    　前記正極合剤にはガス発生剤が含まれ、
    　前記正極の電位が前記二次電池の充電終止電圧を超えて前記ガス発生剤の反応電位に達するまでの容量を、前記負極の電位が前記二次電池の充電終止電圧を超えて前記負極の充電終止電圧に達するまでの容量よりも小さくした二次電池。     A positive electrode having a positive electrode mixture,
    A negative electrode having a negative electrode mixture,
    A battery container containing the positive electrode and the negative electrode;
    And a current interrupting mechanism for interrupting a current flowing between the positive electrode and the negative electrode when the internal pressure of the battery container reaches a predetermined operating pressure,
    The positive electrode mixture contains a gas generating agent,
    The capacity until the potential of the positive electrode exceeds the charge termination voltage of the secondary battery to reach the reaction potential of the gas generating agent, and the potential of the negative electrode exceeds the charge termination voltage of the secondary battery, the charge of the negative electrode is Secondary battery smaller than capacity until reaching the end voltage.
  2. 　請求項１に記載の二次電池において、
    　前記ガス発生剤の反応電位は4.8V～5.0Vである二次電池。     In the secondary battery according to claim 1,
    The secondary battery wherein the reaction potential of the gas generating agent is 4.8 V to 5.0 V.
  3. 　請求項２に記載の二次電池において、
    　前記ガス発生剤は炭酸リチウムである二次電池。     In the secondary battery according to claim 2,
    The secondary battery in which the gas generating agent is lithium carbonate.
  4. 　請求項１に記載の二次電池において、
    　前記負極の負極活物質は、天然黒鉛、人造黒鉛、難黒鉛化炭素、易黒鉛化炭素、酸化ケイ素の一種または二種以上を混合した二次電池。     In the secondary battery according to claim 1,
    The negative electrode active material of the said negative electrode is a secondary battery which mixed 1 type, or 2 or more types of natural graphite, artificial graphite, non-graphitizing carbon, graphitizing carbon, and a silicon oxide.
  5. 　請求項４に記載の二次電池において、
    　前記負極の充電終止電圧は0.01V～0.005Vの範囲である二次電池。     In the secondary battery according to claim 4,
    A secondary battery in which the charge termination voltage of the negative electrode is in the range of 0.01 V to 0.005 V.
  6. 　請求項１に記載の二次電池において、
    　前記正極の電位が前記二次電池の充電終止電圧に達するまでの容量と、前記二次電池の充電終止電圧を超えて、前記正極の電位が前記ガス発生剤の反応電位に達するまでの容量との和が、前記負極の可逆容量よりも小さい二次電池。     In the secondary battery according to claim 1,
    The capacity until the potential of the positive electrode reaches the charge termination voltage of the secondary battery, and the capacity until the potential of the positive electrode reaches the reaction potential of the gas generating agent, exceeding the charge termination voltage of the secondary battery The secondary battery whose sum of is smaller than the reversible capacity of the said negative electrode.
  7. 　請求項５または請求項６に記載の二次電池において、
    　前記二次電池の電池容量に対する前記負極の可逆容量の比が1.5以上である二次電池。     In the secondary battery according to claim 5 or 6,
    The secondary battery whose ratio of the reversible capacity of the said negative electrode to the battery capacity of the said secondary battery is 1.5 or more.
  8. 　請求項１に記載の二次電池において、
    　前記正極は、正極活物質が塗布された正極電極の単位面積あたりの正極初回充電容量が1.82mAh/cm2であり、前記正極電極の単位面積当たりの正極可逆容量が1.60mAh/cm2であり、かつ前記正極電極の単位面積当たりの正極不可逆容量が0.22mAh/cm2であり、
    　前記負極は、負極活物質が塗布された負極電極の単位面積当たりの負極初回充電容量が2.72mAh/cm2であり、前記負極電極の単位面積当たりの負極可逆容量が2.45mAh/cm2であり、かつ前記負極電極の単位面積あたりの負極不可逆容量が0.27mAh/cm2である二次電池。     In the secondary battery according to claim 1,
    The positive electrode has a first charge capacity per unit area of the positive electrode coated with the positive electrode active material of 1.82 mAh / cm 2, a reversible capacity per unit area of the positive electrode of 1.60 mAh / cm 2, and The positive electrode irreversible capacity per unit area of the positive electrode is 0.22 mAh / cm 2,
    The negative electrode has a negative electrode initial charge capacity per unit area of 2.72 mAh / cm 2 for the negative electrode coated with the negative electrode active material, and a negative electrode reversible capacity per unit area of the negative electrode is 2.45 mAh / cm 2, The secondary battery whose negative electrode irreversible capacity per unit area of the said negative electrode is 0.27 mAh / cm <2>.
  9. 　請求項１に記載の二次電池において、
    　前記正極は、正極活物質が塗布された正極電極の単位面積あたりの正極初回充電容量が1.87mAh/cm2であり、前記正極電極の単位面積当たりの正極可逆容量が1.59mAh/cm2であり、かつ前記正極電極の単位面積当たりの正極不可逆容量が0.28mAh/cm2であり、
    　前記負極は、負極活物質が塗布された負極電極の単位面積当たりの負極初回充電容量が2.75mAh/cm2であり、前記負極電極の単位面積当たりの負極可逆容量が2.48mAh/cm2であり、かつ前記負極電極の単位面積あたりの負極不可逆容量が0.27mAh/cm2である二次電池。     In the secondary battery according to claim 1,
    The positive electrode has a first charge capacity per unit area of the positive electrode coated with the positive electrode active material of 1.87 mAh / cm 2, a reversible capacity per unit area of the positive electrode of 1.59 mAh / cm 2, and The positive electrode irreversible capacity per unit area of the positive electrode is 0.28 mAh / cm 2,
    The negative electrode has an initial negative charge capacity per unit area of the negative electrode coated with the negative electrode active material of 2.75 mAh / cm 2, and a reversible capacity per unit area of the negative electrode of 2.48 mAh / cm 2, and The secondary battery whose negative electrode irreversible capacity per unit area of the said negative electrode is 0.27 mAh / cm <2>.
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JPH10134817A (en) * 1996-10-28 1998-05-22 Shin Kobe Electric Mach Co Ltd Organic electrolyte secondary battery
JP2000306610A (en) * 1999-04-21 2000-11-02 Japan Storage Battery Co Ltd Nonaqueous electrolyte secondary battery
JP2015011930A (en) * 2013-07-01 2015-01-19 トヨタ自動車株式会社 Nonaqueous electrolyte secondary battery

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JPH10134817A (en) * 1996-10-28 1998-05-22 Shin Kobe Electric Mach Co Ltd Organic electrolyte secondary battery
JP2000306610A (en) * 1999-04-21 2000-11-02 Japan Storage Battery Co Ltd Nonaqueous electrolyte secondary battery
JP2015011930A (en) * 2013-07-01 2015-01-19 トヨタ自動車株式会社 Nonaqueous electrolyte secondary battery

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021020290A1 (en) * 2019-08-01 2021-02-04 株式会社Ｇｓユアサ Non-aqueous electrolyte power storage element, manufacturing method thereof, and power storage device

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