WO2017174374A1 - Energy storage device - Google Patents

Energy storage device Download PDF

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Publication number
WO2017174374A1
WO2017174374A1 PCT/EP2017/057054 EP2017057054W WO2017174374A1 WO 2017174374 A1 WO2017174374 A1 WO 2017174374A1 EP 2017057054 W EP2017057054 W EP 2017057054W WO 2017174374 A1 WO2017174374 A1 WO 2017174374A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrode sheet
tab
positive electrode
active material
energy storage
Prior art date
Application number
PCT/EP2017/057054
Other languages
French (fr)
Inventor
Yoshihiro Yamamoto
Original Assignee
Lithium Energy and Power GmbH & Co. KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lithium Energy and Power GmbH & Co. KG filed Critical Lithium Energy and Power GmbH & Co. KG
Priority to CN201780021238.4A priority Critical patent/CN108886128B/en
Priority to CN202211680815.XA priority patent/CN116259897A/en
Priority to DE112017001858.7T priority patent/DE112017001858T5/en
Publication of WO2017174374A1 publication Critical patent/WO2017174374A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/10—Multiple hybrid or EDL capacitors, e.g. arrays or modules
    • H01G11/12—Stacked hybrid or EDL capacitors
    • 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
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/54—Connection of several leads or tabs of plate-like electrode stacks, e.g. electrode pole straps or bridges
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/172—Arrangements of electric connectors penetrating the casing
    • H01M50/174—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells
    • H01M50/176—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells for prismatic or rectangular cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/74—Terminals, e.g. extensions of current collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/74—Terminals, e.g. extensions of current collectors
    • H01G11/76—Terminals, e.g. extensions of current collectors specially adapted for integration in multiple or stacked hybrid or EDL capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • 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
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/538—Connection of several leads or tabs of wound or folded electrode stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to an energy storage device having a positive electrode sheet and a negative electrode sheet which are stacked together with a separator interposed therebetween.
  • the energy storage device uses an electrode assembly having a positive electrode sheet and a negative electrode sheet which are stacked alternately with a separator interposed therebetween.
  • the positive electrode sheet and the negative electrode sheet are formed by applying an active material layer on both surfaces of a metal foil by coating.
  • Patent Document 1 there may be a case where tabs are formed on a positive electrode sheet and a negative electrode sheet of an energy storage device such that each of the tabs projects outward in a width direction from a straight edge portion of the sheet on one side in the width direction. At least a portion of the tab is formed as an active material non-formed portion where an active material layer is not formed, and the active material non-formed portion is electrically connected to an external terminal through a current collector.
  • an active material non-formed portion is formed not only on the tab but also on a portion along an edge portion of the positive electrode sheet from which the tab projects.
  • the active material non-formed portion formed along the edge portion of the positive electrode sheet in this manner is disposed so as to opposedly face an active material layer of the negative electrode sheet with a separator interposed therebetween.
  • Patent Document l Japanese Patent No. 5354042
  • the present invention has been made in view of the above, and it is an object of the present invention to suppress the occurrence of short-circuiting in an active material non-formed portion in an energy storage device which includes the active material non-formed portion formed along an edge portion of an electrode sheet on a tab side.
  • An energy storage device includes : a first electrode sheet; and a second electrode sheet stacked on the first electrode sheet with a separator interposed between the first electrode sheet and the second electrode sheet and having a polarity different from a polarity of the first electrode sheet,
  • the first electrode sheet includes ⁇
  • a metal foil having an edge portion extending in a first direction in a straight manner, and a first tab projecting from the edge portion in a second direction which intersects with the first direction!
  • a portion extending along the edge portion and the first tab of the metal foil are formed into an active material non-formed portion where the active material layer is not formed
  • the insulation layer is formed on the active material non-formed portion.
  • the insulation layer be formed in a region of the active material non-formed portion which includes a proximal portion of the first tab.
  • the first tab be rounded at the proximal portion thereof.
  • a stress applied to the proximal portion of the first tab is dispersed so that strength of the first tab can be enhanced.
  • the energy storage device further includes a current collector which electrically connects the first electrode sheet to an external terminal
  • the first tab may be connected to the current collector in a bent state.
  • the proximal portion of the first tab on which a stress is concentrated due to bending is reinforced by the insulation layer so that rigidity and durability of the first tab can be enhanced.
  • a portion of the insulation layer formed on a surface of the first tab project from an edge portion of the separator in the second direction.
  • the insulation layer be also formed on an end surface of the metal foil in the active material non-formed portion.
  • the edge portion of the first electrode sheet can be easily disposed by making the edge portion of the first electrode sheet close to the edge portion of the separator positioned outside the edge portion of the first electrode sheet in the second direction. Accordingly, the first electrode sheet can be expanded in the second direction so that battery capacity can be increased.
  • the first tab and the second tab may project toward the same side in the second direction and, at the same time, may be disposed in a spaced-apart manner from each other in the first direction.
  • this type of energy storage device can acquire the above-mentioned advantageous effects.
  • the winding body may have a first tab bundle formed by stacking the plurality of first tabs.
  • rigidity of the proximal portion of the first tab is enhanced by the insulation layer so that it is possible to suppress the deflection of the first tab which warps in a thickness direction of the first electrode sheet at the time of winding the first electrode sheet. Accordingly, at the time of overlapping the plurality of first tabs by winding the first electrode sheet, the hooking engagement between the first tabs minimally occurs so that breakage of each first tab can be suppressed.
  • the first tab bundle may be provided to the flat portion.
  • this type of energy storage device can acquire the above-mentioned advantageous effects.
  • the energy storage device includes a layered product which is formed of a plurality of first electrode sheets and a plurality of second electrode sheets where the first electrode sheet and the second electrode sheet are stacked alternately with the separator interposed between the first electrode sheet and the second electrode sheet
  • the layered product may include a first tab bundle formed by stacking the first tabs respectively formed on the plurality of first electrode sheets.
  • the present invention even when a state is brought about where the first electrode sheet and the second electrode sheet directly and opposedly face each other due to positional displacement, shrinkage, breakage or the like of the separator, the occurrence of short-circuiting in the active material non-formed portion of the first electrode sheet can be suppressed. This is because the insulation layer is interposed between the active material non-formed portion of the first electrode sheet and the second electrode sheet.
  • Fig. 1 is a perspective view showing an energy storage device according to an embodiment of the present invention.
  • Fig. 2 is a perspective view with a part broken away showing the inside of the energy storage device taken along a line A- A in Fig. 1.
  • Fig. 3 is a perspective view of an electrode assembly of the energy storage device shown in Fig. 1.
  • Fig. 4 is a developed view of the electrode assembly shown in Fig. 3.
  • Fig. 5 is an enlarged view of Fig. 4 showing a positive electrode tab of a positive electrode sheet and portions around the positive electrode tab.
  • Fig. 6 is a cross- sectional view of a first insulation portion of an insulation layer of the positive electrode sheet and portions around the first insulation portion taken along a line B-B in Fig. 5 as viewed in a longitudinal direction of the positive electrode sheet.
  • Fig. 7 is a cross-sectional view of a second insulation portion of the insulation layer of the positive electrode sheet and portions around the second insulation portion taken along a line C _ C in Fig. 5 as viewed in a longitudinal direction of the positive electrode sheet.
  • Fig. 8 is a cross- sectional view of the second insulation portion of the insulation layer of the positive electrode sheet and portions around the second insulation portion taken along a line D-D in Fig. 5 as viewed in a projecting direction of the positive electrode tab.
  • Fig. 9 is an exploded perspective view schematically showing an electrode assembly of an energy storage device according to another embodiment of the present invention.
  • Fig. 1 shows an energy storage device 1 according to an embodiment of the present invention.
  • the energy storage device 1 is a nonaqueous electrolyte secondary battery such as a lithium ion battery, for example.
  • the present invention is also applicable to various energy storage devices including a capacitor besides the lithium ion battery.
  • the energy storage device 1 includes a case 2 having an approximately rectangular parallelepiped shape, for example.
  • the case 2 includes a case body 3 having an upper surface opening portion, and a lid body 4 which closes the upper surface opening portion of the case body 3.
  • case body 3 As a material for forming the case body 3, metal such as aluminum or an aluminum alloy is used, for example. A whole surface of the case body 3 may be covered by an insulation layer made of a resin (not shown in the drawing), for example.
  • the lid body 4 is formed of a metal plate having a rectangular shape, for example.
  • the lid body 4 is connected to an opening edge portion of the case body 3 by welding.
  • An external terminal 11 of a positive electrode and an external terminal 12 of a negative electrode are fixed to a surface of the lid body 4.
  • the respective external terminals 11, 12 are fixed to an upper surface of the lid body 4 by caulking by way of upper gaskets 13 respectively, for example.
  • metal such as aluminum, copper or nickel is used, for example.
  • a gas release vent 8 for releasing a gas generated in the case body 3 to the outside of the case 2, and an electrolyte solution filling port (not shown in the drawing) are provided to the lid body 4.
  • the electrolyte solution filling port is closed by an electrolyte solution filling plug 10.
  • At least one electrode assembly 20 (corresponding to "winding body” in Claims), current collectors 15 which electrically connect the electrode assembly 20 to the external terminals 11, 12 of the positive electrode and the negative electrode, and an electrolyte solution (not shown in the drawing) are stored in the case 2.
  • the current collector 15 shown in Fig. 2 is a positive electrode current collector connected to the external terminal 11 of the positive electrode, the configuration of the positive electrode current collector 15 is described hereinafter with reference to Fig. 2, and the illustration and the description of a negative electrode current collector connected to the external terminal 12 of the negative electrode are omitted.
  • the negative electrode current collector has the same configuration as the positive electrode current collector 15 described hereinafter, the negative electrode current collector may have the same configuration as the positive electrode current collector 15 described hereinafter, the negative electrode current collector may have the same configuration as the positive electrode current collector 15 described hereinafter, the negative electrode current collector may have the same configuration as the positive electrode current collector 15 described hereinafter, the negative electrode current collector may have the same configuration as the positive electrode current collector 15 described hereinafter, the negative electrode current collector may have the
  • the positive electrode current collector 15 and the negative electrode current collector may be made of materials which differ from each other.
  • metal such as aluminum is used as a material for forming the positive electrode current collector 15, for example, and metal such as copper is used as a material for forming the negative electrode current collector, for example.
  • the current collector 15 is fixed to a lower surface of the lid body 4 by caulking by way of a lower gasket 14, for example.
  • the current collector 15 includes, for example, a first flat plate portion 15a fixed to the lid body 4, a connecting portion 15b which extends downward while being curved from an edge portion of the first flat plate portion 15a, and a second flat plate portion 15c continuously formed with the first flat plate portion 15a by way of the connecting portion 15b and disposed below the first flat plate portion 15a in an opposedly facing manner.
  • the first flat plate portion 15a is electrically connected to the external terminal 11 through a rivet portion (not shown in the drawing) extending downward from the external terminal 11, for example.
  • Tabs 35 described later which are formed on the electrode assembly 20 are joined to a lower surface of the second flat plate portion 15c by ultrasonic welding, for example. With such a configuration, the external terminal 11 is electrically connected to the electrode assembly 20.
  • the electrode assembly 20 is configured such that a positive electrode sheet (corresponding to "first electrode sheet” in Claims) 21, a negative electrode sheet 22 (corresponding to "second electrode sheet” in Claims), and two separators 23, 23 each formed using a microporous resin sheet, each having an elongated strip shape with a fixed width, are made to overlap with each other, and are wound into an approximately elongated circular shape with a high flatness ratio.
  • a positive electrode sheet corresponding to "first electrode sheet” in Claims
  • a negative electrode sheet 22 corresponding to "second electrode sheet” in Claims
  • two separators 23, 23 each formed using a microporous resin sheet, each having an elongated strip shape with a fixed width, are made to overlap with each other, and are wound into an approximately elongated circular shape with a high flatness ratio.
  • Either one of two separators 23, 23 is interposed between one layer of the positive electrode sheet 21 and one layer of the negative electrode sheet 22 disposed adjacently to one layer of the positive electrode sheet 21.
  • an outermost layer of the electrode assembly 20 is formed of either one of the separators 23.
  • An axis of winding (winding axis) of the positive electrode sheet 21, the negative electrode sheet 22 and two separators 23, 23 is conceptually indicated by symbol X in Fig. 3.
  • the electrode assembly 20 is stored in the inside of the case body 3 in a posture where the winding axis X extends substantially in a direction in which a bottom wall portion and the upper surface opening portion of the case body 3 shown in Fig. 1 face each other in an opposed manner (in a vertical direction in Fig. l).
  • respective end portions of the electrode assembly 20 in a direction in which the winding axis X extends form end surface portions 20a, 20b on which edge portions of the positive electrode sheet 21 in a width direction (lateral direction), edge portions of the negative electrode sheet 22 in a width direction (lateral direction), and edge portions of the separators 23, 23 in a width direction (lateral direction) are disposed.
  • the electrode assembly 20 includes ⁇ a pair of flat portions 20c, 20c which are disposed to opposedly face each other with the winding axis X interposed therebetween and extends in a straight manner in parallel to each other as viewed in a direction in which the winding axis X extends! and a pair of curved portions 20d, 20d which extends in a semi- circularly curved manner as viewed in a direction in which the winding axis X extends and connects the pair of flat portions 20c, 20c to each other.
  • the flat portion 20c is a portion which extends in a straight manner in design. In a state where the electrode assembly 20 is actually stored in the case 2, the flat portion 20c is not always disposed in a completely straight manner, and there may be a case where the flat portion 20c is disposed in a deflected manner although the flat portion 20c may be formed into an approximately linear shape as a whole.
  • the positive electrode sheet 21 includes ⁇ a strip-shaped positive electrode metal foil 24; and positive active material layers 25 which are formed on both surfaces of the positive electrode metal foil 24 respectively. Edge portions on both sides in a width direction (lateral direction) of the positive electrode metal foil 24 are formed in a straight extending manner in a longitudinal direction of the positive electrode metal foil 24. On one side in a width direction of the positive electrode metal foil 24 (a lower side in Fig. 3 and Fig. 4), the positive active material layer 25 is formed so as to reach the edge portion of the positive electrode metal foil 24. On the edge portion on the other side in the width direction of the positive electrode metal foil 24 (an upper side in Fig. 3 and Fig.
  • the positive active material layer 25 is not formed, and a first active material non-formed portion 34 is formed where the positive electrode metal foil 24 is exposed.
  • the first active material non-formed portion 34 of the positive electrode metal foil 24 is covered by an insulation layer 40 described layer (see Fig. 5 to Fig. 8). In Fig. 3, the illustration of the insulation layer 40 is omitted.
  • lithium manganate (LiM ⁇ O , nickel-cobalt-lithium manganate (LiNi x CoyMni-x- y O2), lithium cobaltate (L1C0O2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO , lithium manganese phosphate (LiMnPO , materials formed by using substitution additives in these compounds or mixtures of these compounds can be used.
  • LiM ⁇ O nickel-cobalt-lithium manganate
  • LiNiO2 lithium cobaltate
  • LiNiO2 lithium nickelate
  • LiFePO lithium iron phosphate
  • LiMnPO lithium manganese phosphate
  • the negative electrode sheet 22 includes ⁇ a strip-shaped negative electrode metal foil 26; and negative active material layers 27 which are formed on both surfaces of the negative electrode metal foil 26 respectively. Edge portions of the negative electrode metal foil 26 on both sides in a width direction (lateral direction) are formed in a straight extending manner in a longitudinal direction of the negative electrode metal foil 26. On both sides in a width direction of the negative electrode metal foil 26 (an upper side and a lower side in Fig. 3 and Fig. 4), the negative active material layers 27 are formed so as to reach the edge portions of the negative electrode metal foil 26. With such a configuration, respective whole surfaces of the negative electrode metal foil 26 are covered by the negative active material layers 27.
  • metal other than copper may be used.
  • graphite is used, for example.
  • materials capable of occluding lithium such as other carbon materials, lithium metal, a lithium alloy, lithium titanate (L ⁇ isO ⁇ ), silicon, silicon monoxide, or tin, or a mixture of these materials may be used.
  • a longitudinal direction of the positive electrode sheet 21, a longitudinal direction of the negative electrode sheet 22, and a longitudinal direction of the separator 23 are simply referred to as
  • longitudinal direction P a lateral direction of the positive electrode sheet 21, a lateral direction of the negative electrode sheet 22, and a lateral direction of the separator 23
  • lateral direction Q a thickness direction of the positive electrode sheet 21, a thickness direction of the negative electrode sheet 22, and a thickness direction of the separator 23
  • thickness direction R a thickness direction of the separator 23
  • the longitudinal direction P corresponds to the "first direction” in Claims.
  • the lateral direction Q corresponds to "second direction” in Claims, and is a width direction parallel to the winding axis X (see Fig. 3) of the electrode assembly 20.
  • a width of the negative electrode sheet 22 is set larger than a width of the positive electrode sheet 21.
  • the negative electrode sheet 22 projects outward from the edge portion of the positive electrode sheet 21 on both sides in the lateral direction Q.
  • a width of the separator 23 is set larger than the width of the negative electrode sheet 22.
  • the separator 23 projects outward from an edge portion of the negative electrode sheet 22 on both sides in the lateral direction Q.
  • a plurality of positive electrode tabs (corresponding to "first tab” in Claims) 35 which project outward in the lateral direction Q from the
  • first active material non-formed portion 34 which extends in a straight manner along the edge portion of the positive electrode metal foil 24 on one side (an upper side in Fig. 3 and Fig. 4) in the lateral direction Q are formed at intervals in the longitudinal direction P.
  • the first active material non-formed portion 34 and the plurality of positive electrode tabs 35 are formed of a sheet of positive electrode metal foil 24, and the respective positive electrode tabs 35 are integrally connected to the first active material non-formed portion 34.
  • the positive electrode tab 35 forms a second active material non-formed portion where an active material layer is not formed on a surface of the positive electrode metal foil 24.
  • rounded portions 35f are formed on corner portions between edge portions of the positive electrode tab 35 in the longitudinal direction P and an edge portion of the first active material non-formed portion 34 in the lateral direction Q.
  • the rounded portions 35f, 35f are formed on both edge portions of the proximal portion 35a in the longitudinal direction P.
  • the stress concentration applied to the proximal portion 35a of the positive electrode tab 35, particularly, to the corner portions of the proximal portion 35a can be dispersed so that breakage of the positive tab 35 at the proximal portion 35a can be suppressed. That is, the strength of the proximal portion 35a of the positive electrode tab 35 can be enhanced.
  • a plurality of negative electrode tabs (corresponding to "second tab” in Claims) 37 are also formed on the negative electrode metal foil 26 in the same manner as the positive electrode tabs 35.
  • the negative electrode tabs 37 are formed in a projecting manner toward the same side as the positive electrode tabs 35 in the lateral direction Q. Most of the portion of the negative electrode tab 37 except for a proximal end portion is formed into an active material non-formed portion where an active material layer is not formed on the surface of the negative electrode metal foil 26.
  • the electrode assembly 20 which is formed by winding the positive electrode sheet 21, the negative electrode sheet 22 and the separators 23, 23 in a state where the positive electrode sheet 21 and the negative electrode sheet 22 are made to overlap with each other with the separator 23, 23 interposed therebetween has a positive electrode tab bundle (corresponding to "first tab bundle” in Claims) 55 which is formed by stacking a plurality of positive electrode tabs 35.
  • the positive electrode tab bundle 55 is formed on one flat portion 20c of the electrode assembly 20.
  • the negative electrode tabs 37 are disposed in a spaced-apart manner from the positive electrode tabs 35 in the longitudinal direction P and hence, there is no possibility that the positive electrode tabs 35 and the negative electrode tabs 37 overlap with each other.
  • the plurality of negative electrode tabs 37 are made to overlap with each other. With such a configuration, a negative electrode tab bundle 57 which forms the second tab bundle is formed.
  • the positive electrode tab bundle 55 and the negative electrode tab bundle 57 respectively project from one end surface portion 20a (the end surface portion on an upper side in Fig. 3) of the electrode assembly 20. Further, the positive electrode tab bundle 55 and the negative electrode tab bundle 57 respectively project from one (a viewer's side in Fig. 3) of the pair of flat portions 20c, 20c with respect to a center line Y extending in the longitudinal direction when the end surface portion 20a of the electrode assembly 20 is viewed in the direction in which the winding axis X extends.
  • the positive electrode tab bundle 55 which projects from one flat portion 20c of the electrode assembly 20 is connected to the positive electrode current collector 15 in a state where the positive electrode tab bundle 55 is bent in a falling manner toward the other flat portion 20c side in the thickness direction Z (the direction orthogonal to the winding axis X and the center line Y) of the electrode assembly 20.
  • the respective positive electrode tabs 35 which form the positive electrode tab bundle 55 are curved at the proximal portions 35a thereof (portions ranging from proximal ends to intermediate portions), and distal-end-side portions (portions ranging from distal ends 35c to the intermediate portions) 35b of the respective positive electrode tabs 35 face an upper side of the end surface portion 20a of the electrode assembly 20 and, at the same time, are disposed along a lower surface of the second flat plate portion 15c of the positive electrode current collector 15.
  • the positive electrode tab bundle 55 is joined to the lower surface of the second flat plate portion 15c of the positive electrode current collector 15 by ultrasonic welding, for example. With such a configuration, the respective positive electrode tabs 35 are electrically connected to the external terminal 11 of the positive electrode through the positive electrode current collector 15.
  • the negative electrode tabs 37 are also electrically connected to the external terminal 12 (see Fig. l) of the negative electrode through the negative current collector (not shown in the drawing) in a state where the negative electrode tabs 37 are bent in the same manner as the positive electrode tabs 35.
  • Fig. 5 is an enlarged view showing the positive electrode tab 35 and portions around the positive electrode tab 35 as viewed from one surface side of the positive electrode sheet 21.
  • Fig. 6 is a cross- sectional view of the first active material non-formed portion 34 and portions around the first active material non-formed portion 34 at a portion displaced from the positive electrode tab 35 in the longitudinal direction P taken along a line B-B in Fig. 5 as viewed in the longitudinal direction P.
  • Fig. 7 is a cross- sectional view of the positive electrode tab 35 and portions around the positive electrode tab 35 taken along a line OC in Fig. 5 as viewed in the longitudinal direction P.
  • Fig. 8 is a cross-sectional view of the positive electrode tab 35 and portions around the positive electrode tab 35 taken along a line D-D in Fig. 5 as viewed in a projecting direction (lateral direction Q) of the positive electrode tab 35.
  • the negative active material layer 27 is disposed in a more outwardly projecting manner than the positive active material layer 25 is.
  • the insulation layer 40 is formed on the surface of the positive electrode metal foil 24 such that the insulation layer 40 is disposed adjacently to the edge portion of the positive active material layer 25 along one edge portion of the positive active material layer 25 in the lateral direction Q.
  • the insulation layer 40 is formed on both surfaces of the positive electrode metal foil 24.
  • the insulation layer 40 includes a first insulation layer portion 41 formed on the first active material non-formed portion 34 of the positive electrode metal foil 24, and a second insulation layer portion 42 formed on the positive electrode tab 35 which forms the second active material non-formed portion.
  • the first insulation layer portion 41 is formed on surfaces of the first active material non-formed portion 34 on both sides in the same manner. On each surface of the first active material non-formed portion 34, the first insulation layer portion 41 is formed along an upper edge portion of the positive active material layer 25 in the lateral direction Q, and covers an upper edge portion of the positive active material layer 25.
  • the first insulation layer portion 41 is formed in a projecting manner from an upper end surface 24a of the positive electrode metal foil 24 in the lateral direction Q, and covers the upper end surface 24a.
  • the first insulation layer portion 41 is formed over the entire length of the first active material non-formed portion 34 in the longitudinal direction P. With such a configuration, surfaces of the first active material non-formed portion 34 on both sides and the upper end surface 24a of the first active material non-formed portion 34 are completely covered by the first insulation layer portion 41.
  • the second insulation layer portion 42 is formed in a region including the proximal portion 35a of the positive electrode tab 35.
  • the second insulation layer portion 42 is formed on a portion of the positive electrode tab 35 ranging from a proximal end to an intermediate portion.
  • a distal-end-side portion 35b of the positive electrode tab 35 is exposed without being covered by the insulation layer 40 and hence, the distal-end-side portion 35b and the above-mentioned current collector 15 can be connected to each other.
  • the second insulation layer portion 42 is formed on both surfaces of the positive electrode tab 35 in the same manner.
  • the second insulation layer portion 42 is integrally connected to an outer side of the first insulation layer portion 41 in the lateral direction Q.
  • an upper edge portion 42a of the second insulation layer portion 42 is positioned outside an upper edge portion 22a of the negative electrode sheet 22a and an upper edge portion 23a of the separator 23.
  • the proximal portion 35a of the positive electrode tab 35 is covered by the insulation layer 40, the proximal portion 35a can be reinforced by the insulation layer 40 while suppressing the occurrence of short-circuiting.
  • the positive electrode tab 35 is bent for connection with the current collector 15 as described above (see Fig. 2) and hence, a stress is liable to be concentrated on the proximal portion 35a which is curved by bending.
  • the proximal portion 35a is reinforced by the insulation layer 40 and hence, rigidity of the positive electrode tab 35 can be enhanced so that durability of the positive electrode tab 35 can be enhanced.
  • rigidity of the proximal portion 35a of the positive electrode tab 35 is enhanced by the insulation layer 40 and hence, it is possible to suppress the deflection of the positive electrode tab 35 which warps in a thickness direction R of the positive electrode sheet 21 at the time of winding the positive electrode sheet 21. Accordingly, at the time of making the plurality of positive electrode tabs 35 overlap with each other by winding the positive electrode sheet 21, the hooking engagement between the positive electrode tabs 35 minimally occurs so that breaking of each positive electrode tab 35 can be suppressed.
  • the rounded portions 35f, 35f are formed on the proximal portion 35a and hence, even when tension is applied to the positive electrode sheet 21 at the time of winding the positive electrode sheet 21, the stress concentration to the proximal portion 35a is alleviated so that the strength of the proximal portion 35a is further enhanced.
  • the second insulation layer portion 42 of the insulation layer 40 projects outward from the positive electrode tab 35 on both sides in the longitudinal direction P, and covers side edge surfaces 35d, 35e on both sides of the positive electrode tab 35.
  • the proximal portion 35a of the positive electrode tab 35 is configured such that surfaces of the positive electrode tab 35 on both sides and side edge surfaces 35d, 35e of the positive electrode tab 35 on both sides are covered by the second insulation layer portion 42.
  • an insulation material having high electric resistivity is used as a material for forming the insulation layer 40.
  • an insulation material having high electric resistivity is used as a specific material for forming the insulation layer 40.
  • a specific material for forming the insulation layer 40 for example, a mixture of inorganic and/or organic particles and a binder is used.
  • the inorganic particles for example, particles made of alumina (AI2O3), S1O2, Zr02, T1O2 or MgO are used, and as the organic particles, for example, polyimide powder is used.
  • the binder for example, polyvinylidene fluoride (PVDF),
  • PTFE polytetrafluoroethylene
  • polyimide polyimide
  • polyamide polyamide
  • the insulation layer 40 is disposed such that the insulation layer 40 faces the negative active material layer 27 with the separator 23 interposed therebetween.
  • the second insulation layer portion 42 of the insulation layer 40 projects from the upper edge portion 23a of the separator 23 in the lateral direction Q.
  • the insulation layer 40 which covers a metal portion of the positive electrode sheet 21 is interposed between the metal foil 24 at the first active material non-formed portion 34 and the positive electrode tab 35 and the negative active material layer 27 and hence, the occurrence of short-circuiting can be prevented.
  • the insulation layer 40 covers not only surfaces of the first active material non-formed portion 34 and the proximal portion 35a of the positive electrode tab 35 on both sides but also the upper end surface 24a of the first active material non-formed portion 34 and side edge surfaces 35d, 35e of the positive electrode tab 35 and hence, the occurrence of short-circuiting can be further effectively suppressed.
  • the positive electrode metal foil 24 is covered by the insulation layer 40 and hence, melting of metal on the positive electrode metal foil 24 positioned in the vicinity of the negative electrode sheet 22 can be prevented so that the precipitation of metal on the negative electrode sheet 22 can be suppressed whereby the occurrence of short-circuiting attributed to metal precipitate can be prevented.
  • the upper end surface 24a of the first active material non-formed portion 34 is covered by the insulation layer 40 and hence, while suppressing short-circuiting at the upper end surface 24a, the upper end surface 24a can be easily disposed close to the upper edge portion 23a of the separator 23 positioned outside the upper end surface 24a in the lateral direction Q. Accordingly, the positive electrode metal foil 24 can be expanded in the lateral direction Q so that battery capacity can be increased.
  • the positive electrode tab 35 is formed by cutting the positive electrode metal foil 24 into a predetermined shape.
  • the positive electrode tabs 35 can be formed by cutting portions of the positive electrode metal foil 24 except for portions of the positive electrode metal foil 24 which correspond to the positive electrode tabs 35 at one edge portion of the positive electrode metal foil 24 in the lateral direction Q.
  • the above-mentioned upper end surface 24a of the first active material non-formed portion 34 and side edge surfaces 35d, 35e of the positive electrode tab 35 are formed by cutting the positive electrode metal foil 24 as described above and, thereafter, the insulation layer 40 is formed. In this manner, the formation of the insulation layer 40 is performed after the positive electrode metal foil 24 is cut and hence, the end surface 24a of the first active material non-formed portion 34 and the side edge surfaces 35d, 35e of the positive electrode tab 35 can be covered by the insulation layer 40.
  • the insulation layer 40 is formed by applying a paste-like material by coating using a slot die method, for example.
  • a method for forming the insulation layer 40 is not limited to such a method.
  • the insulation layer 40 may be formed by electrostatic powder coating.
  • the description is made with respect to the energy storage device 1 which includes a so-called winding-type electrode assembly 20.
  • the present invention is also applicable to an energy storage device which includes a so-called stacking type electrode assembly 120 (corresponding to "layered product" in Claims) as shown in Fig. 9, for example.
  • the electrode assembly 120 shown in Fig. 9 is a layered product which is formed of a plurality of positive electrode sheets (corresponding to "first electrode sheet” in Claims) 121 and a plurality of negative electrode sheets (corresponding to "second electrode sheet” in Claims) 122 where the positive electrode sheet 121 and the negative electrode sheet 122 are stacked alternately with a separator 123 interposed therebetween.
  • Each positive electrode sheet includes a first active material non-formed portion 34 and a positive electrode tab 35 which forms a second active material non-formed portion in the same manner as the above-mentioned embodiment, and each negative electrode sheet 122 includes a negative electrode tab 37 in the same manner as the above-mentioned embodiment.
  • the electrode assembly 120 includes ⁇ a positive electrode tab bundle which is formed by stacking the positive electrode tabs 35 formed on the respective positive electrode sheets 121; and a negative electrode tab bundle which is formed by stacking the negative electrode tabs 37 formed on the respective negative electrode sheets 122.
  • the energy storage device of this embodiment can acquire substantially the same advantageous effects as the above-mentioned embodiment such as an effect that a proximal portion of the tab 35 on which a stress is liable to be concentrated due to bending of the positive electrode tab 35 can be reinforced by an insulation layer.
  • first direction in which the edge portion of the positive electrode sheet 21 which forms the first active material non-formed portion 34 extends and "second direction” in which the positive electrode tab 35 projects from the edge portion are orthogonal to each other.
  • second direction may be inclined with respect to the direction orthogonal to the first direction.
  • the present invention is also applicable to the case where the first electrode sheet is a negative electrode sheet.
  • a metal foil of the first electrode sheet may not be always made of only metal, and a conductive coating layer (film) made of a resin or the like may be formed on a surface of metal.
  • the insulation layer formed on the surface of the metal foil of the first electrode sheet may be formed in an overlapping manner on the surface of the edge portion of the active material layer or may be formed on the whole surface of the active material layer by overcoating.
  • the insulation layer may not be always formed on the end surfaces of the metal foil.
  • cutting of the first electrode sheet for forming the first tab may be performed after the insulation layer is formed on the surfaces of the metal foil.
  • the rounded portions may not be always formed on the proximal portion of the first tab.

Abstract

To suppress the occurrence of short-circuiting in an active material non-formed portion in an energy storage device which includes the active material non-formed portion along an edge portion of an electrode sheet on a tab side. An energy storage device (1) includes: a first electrode sheet (21); and a second electrode sheet (22) stacked on the first electrode sheet (21) with a separator (23) interposed between the first electrode sheet (21) and the second electrode sheet (22) and having a polarity different from a polarity of the first electrode sheet, wherein the first electrode sheet (21) includes: a metal foil (24) having an edge portion (34) extending in a first direction (P) in a straight manner, and a first tab (35) projecting from the edge portion in a second direction (Q) which intersects with the first direction; an active material layer (25) formed on a surface of the metal foil (24); and an insulation layer (40) formed on the surface of the metal foil (24), a portion extending along the edge portion (34) and the first tab (35) of the metal foil (24) are formed into an active material non-formed portion where the active material layer (25) is not formed, and the insulation layer (40) is formed on the active material non-formed portion (34, 35).

Description

DESCRIPTION
TITLE OF THE INVENTION: ENERGY STORAGE DEVICE
TECHNICAL FIELD
The present invention relates to an energy storage device having a positive electrode sheet and a negative electrode sheet which are stacked together with a separator interposed therebetween.
BACKGROUND ART
In an energy storage device such as a lithium ion battery, there may be a case where the energy storage device uses an electrode assembly having a positive electrode sheet and a negative electrode sheet which are stacked alternately with a separator interposed therebetween. In general, the positive electrode sheet and the negative electrode sheet are formed by applying an active material layer on both surfaces of a metal foil by coating.
As disclosed in Patent Document 1, there may be a case where tabs are formed on a positive electrode sheet and a negative electrode sheet of an energy storage device such that each of the tabs projects outward in a width direction from a straight edge portion of the sheet on one side in the width direction. At least a portion of the tab is formed as an active material non-formed portion where an active material layer is not formed, and the active material non-formed portion is electrically connected to an external terminal through a current collector.
In this type of energy storage device, there may be a case where, on the positive electrode sheet, an active material non-formed portion is formed not only on the tab but also on a portion along an edge portion of the positive electrode sheet from which the tab projects. There may be also a case where the active material non-formed portion formed along the edge portion of the positive electrode sheet in this manner is disposed so as to opposedly face an active material layer of the negative electrode sheet with a separator interposed therebetween.
PRIOR ART DOCUMENT PATENT DOCUMENT
Patent Document l: Japanese Patent No. 5354042
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
In the energy storage device described above where the active material non-formed portion formed along the edge portion of the positive electrode sheet on a tab side is disposed so as to opposedly face the negative active material layer with the separator interposed therebetween, there is a following possibility. When a state is brought about where a positive active material non-formed portion and a negative active material layer directly and opposedly face each other due to a cause such as positional displacement, shrinkage or breakage of the separator, short-circuiting occurs between the positive active material non-formed portion and the negative active material layer.
The present invention has been made in view of the above, and it is an object of the present invention to suppress the occurrence of short-circuiting in an active material non-formed portion in an energy storage device which includes the active material non-formed portion formed along an edge portion of an electrode sheet on a tab side.
MEANS FOR SOLVING THE PROBLEMS
An energy storage device according to the present invention includes: a first electrode sheet; and a second electrode sheet stacked on the first electrode sheet with a separator interposed between the first electrode sheet and the second electrode sheet and having a polarity different from a polarity of the first electrode sheet,
wherein the first electrode sheet includes^
a metal foil having an edge portion extending in a first direction in a straight manner, and a first tab projecting from the edge portion in a second direction which intersects with the first direction!
an active material layer formed on a surface of the metal foil! and an insulation layer formed on the surface of the metal foil,
a portion extending along the edge portion and the first tab of the metal foil are formed into an active material non-formed portion where the active material layer is not formed, and
the insulation layer is formed on the active material non-formed portion.
With such a configuration, even when a state is brought about where the first electrode sheet and the second electrode sheet directly and opposedly face each other due to positional displacement, shrinkage, breakage or the like of the separator, the occurrence of short-circuiting in the active material non-formed portion of the first electrode sheet can be suppressed. This is because the insulation layer is interposed between the active material non-formed portion of the first electrode sheet and the second electrode sheet.
In the present invention, it is preferable that the insulation layer be formed in a region of the active material non-formed portion which includes a proximal portion of the first tab. With such a configuration, it is possible to reinforce the proximal portion of the first tab by the insulation layer while suppressing the occurrence of short-circuiting at the proximal portion of the first tab.
In the present invention, it is preferable that the first tab be rounded at the proximal portion thereof. With such a configuration, a stress applied to the proximal portion of the first tab is dispersed so that strength of the first tab can be enhanced.
In a case where the energy storage device according to the present invention further includes a current collector which electrically connects the first electrode sheet to an external terminal, the first tab may be connected to the current collector in a bent state. In this case, the proximal portion of the first tab on which a stress is concentrated due to bending is reinforced by the insulation layer so that rigidity and durability of the first tab can be enhanced.
In the present invention, it is preferable that a portion of the insulation layer formed on a surface of the first tab project from an edge portion of the separator in the second direction. Wish such a configuration, even when a state is brought about where the first tab opposedly faces the second electrode sheet without interposing the separator therebetween due to positional displacement, shrinkage, breakage or the like of the separator, the occurrence of short-circuiting in the first tab can be suppressed since the insulation layer is interposed between the metal foil of the first tab and the second electrode sheet,.
In the present invention, it is preferable that the insulation layer be also formed on an end surface of the metal foil in the active material non-formed portion. With such a configuration, the occurrence of
short-circuiting in the active material non-formed portion of the first electrode sheet can be suppressed more effectively. Further, the end surface of the edge portion of the first electrode sheet is covered by the insulation layer and hence, while suppressing the occurrence of short-circuiting at the end surface of the edge portion, the edge portion of the first electrode sheet can be easily disposed by making the edge portion of the first electrode sheet close to the edge portion of the separator positioned outside the edge portion of the first electrode sheet in the second direction. Accordingly, the first electrode sheet can be expanded in the second direction so that battery capacity can be increased.
In the present invention, in the case where the second electrode sheet has an edge portion extending in a straight manner in the first direction and a second tab extending in the second direction from the edge portion, the first tab and the second tab may project toward the same side in the second direction and, at the same time, may be disposed in a spaced-apart manner from each other in the first direction. In this case, this type of energy storage device can acquire the above-mentioned advantageous effects. In the present invention, in the case where the first electrode sheet has a plurality of first tabs disposed in a spaced-apart manner in the first direction, and a winding body is formed by winding the first electrode sheet and the second electrode sheet around an axis parallel to the second direction while overlapping the first electrode sheet and the second electrode sheet with each other with the separator interposed therebetween, the winding body may have a first tab bundle formed by stacking the plurality of first tabs. In this case, rigidity of the proximal portion of the first tab is enhanced by the insulation layer so that it is possible to suppress the deflection of the first tab which warps in a thickness direction of the first electrode sheet at the time of winding the first electrode sheet. Accordingly, at the time of overlapping the plurality of first tabs by winding the first electrode sheet, the hooking engagement between the first tabs minimally occurs so that breakage of each first tab can be suppressed.
In the present invention, in the case where the winding body includes a pair of flat portions extending in a straight manner parallel to each other as viewed in a direction in which the axis extends, and a pair of curved portions connecting the pair of flat portions, the first tab bundle may be provided to the flat portion. In this case, this type of energy storage device can acquire the above-mentioned advantageous effects.
In the case where the energy storage device according to the present invention includes a layered product which is formed of a plurality of first electrode sheets and a plurality of second electrode sheets where the first electrode sheet and the second electrode sheet are stacked alternately with the separator interposed between the first electrode sheet and the second electrode sheet, the layered product may include a first tab bundle formed by stacking the first tabs respectively formed on the plurality of first electrode sheets. In this case, this type of energy storage device can acquire the above-mentioned advantageous effects.
ADVANTAGES OF THE INVENTION
According to the present invention, even when a state is brought about where the first electrode sheet and the second electrode sheet directly and opposedly face each other due to positional displacement, shrinkage, breakage or the like of the separator, the occurrence of short-circuiting in the active material non-formed portion of the first electrode sheet can be suppressed. This is because the insulation layer is interposed between the active material non-formed portion of the first electrode sheet and the second electrode sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view showing an energy storage device according to an embodiment of the present invention.
Fig. 2 is a perspective view with a part broken away showing the inside of the energy storage device taken along a line A- A in Fig. 1.
Fig. 3 is a perspective view of an electrode assembly of the energy storage device shown in Fig. 1.
Fig. 4 is a developed view of the electrode assembly shown in Fig. 3.
Fig. 5 is an enlarged view of Fig. 4 showing a positive electrode tab of a positive electrode sheet and portions around the positive electrode tab. Fig. 6 is a cross- sectional view of a first insulation portion of an insulation layer of the positive electrode sheet and portions around the first insulation portion taken along a line B-B in Fig. 5 as viewed in a longitudinal direction of the positive electrode sheet.
Fig. 7 is a cross-sectional view of a second insulation portion of the insulation layer of the positive electrode sheet and portions around the second insulation portion taken along a line C_C in Fig. 5 as viewed in a longitudinal direction of the positive electrode sheet.
Fig. 8 is a cross- sectional view of the second insulation portion of the insulation layer of the positive electrode sheet and portions around the second insulation portion taken along a line D-D in Fig. 5 as viewed in a projecting direction of the positive electrode tab.
Fig. 9 is an exploded perspective view schematically showing an electrode assembly of an energy storage device according to another embodiment of the present invention.
MODES FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention is described with reference to attached drawings. In this specification, terms which contain "upper" and "lower" used for indicating directions and terms relating to such terms and indicating directions are used for indicating directions in the posture of an energy storage device illustrated in the attached drawings. These directions are not necessarily equal to the directions of the energy storage device in an actual use state.
Fig. 1 shows an energy storage device 1 according to an embodiment of the present invention. The energy storage device 1 is a nonaqueous electrolyte secondary battery such as a lithium ion battery, for example. However, the present invention is also applicable to various energy storage devices including a capacitor besides the lithium ion battery.
As show in Fig. 1, the energy storage device 1 includes a case 2 having an approximately rectangular parallelepiped shape, for example. The case 2 includes a case body 3 having an upper surface opening portion, and a lid body 4 which closes the upper surface opening portion of the case body 3.
As a material for forming the case body 3, metal such as aluminum or an aluminum alloy is used, for example. A whole surface of the case body 3 may be covered by an insulation layer made of a resin (not shown in the drawing), for example.
The lid body 4 is formed of a metal plate having a rectangular shape, for example. The lid body 4 is connected to an opening edge portion of the case body 3 by welding. An external terminal 11 of a positive electrode and an external terminal 12 of a negative electrode are fixed to a surface of the lid body 4.
The respective external terminals 11, 12 are fixed to an upper surface of the lid body 4 by caulking by way of upper gaskets 13 respectively, for example. As a material for forming the external terminals 11, 12, metal such as aluminum, copper or nickel is used, for example.
A gas release vent 8 for releasing a gas generated in the case body 3 to the outside of the case 2, and an electrolyte solution filling port (not shown in the drawing) are provided to the lid body 4. The electrolyte solution filling port is closed by an electrolyte solution filling plug 10.
As shown in Fig. 2, at least one electrode assembly 20 (corresponding to "winding body" in Claims), current collectors 15 which electrically connect the electrode assembly 20 to the external terminals 11, 12 of the positive electrode and the negative electrode, and an electrolyte solution (not shown in the drawing) are stored in the case 2.
The current collector 15 shown in Fig. 2 is a positive electrode current collector connected to the external terminal 11 of the positive electrode, the configuration of the positive electrode current collector 15 is described hereinafter with reference to Fig. 2, and the illustration and the description of a negative electrode current collector connected to the external terminal 12 of the negative electrode are omitted.
Although the negative electrode current collector has the same configuration as the positive electrode current collector 15 described hereinafter, the negative electrode current collector may have the
configuration which differs from the configuration of the positive electrode current collector 15. Further, the positive electrode current collector 15 and the negative electrode current collector may be made of materials which differ from each other. To be more specific, metal such as aluminum is used as a material for forming the positive electrode current collector 15, for example, and metal such as copper is used as a material for forming the negative electrode current collector, for example.
The current collector 15 is fixed to a lower surface of the lid body 4 by caulking by way of a lower gasket 14, for example. The current collector 15 includes, for example, a first flat plate portion 15a fixed to the lid body 4, a connecting portion 15b which extends downward while being curved from an edge portion of the first flat plate portion 15a, and a second flat plate portion 15c continuously formed with the first flat plate portion 15a by way of the connecting portion 15b and disposed below the first flat plate portion 15a in an opposedly facing manner.
The first flat plate portion 15a is electrically connected to the external terminal 11 through a rivet portion (not shown in the drawing) extending downward from the external terminal 11, for example. Tabs 35 described later which are formed on the electrode assembly 20 are joined to a lower surface of the second flat plate portion 15c by ultrasonic welding, for example. With such a configuration, the external terminal 11 is electrically connected to the electrode assembly 20.
Also with reference to Fig. 3 and Fig. 4, the electrode assembly 20 is configured such that a positive electrode sheet (corresponding to "first electrode sheet" in Claims) 21, a negative electrode sheet 22 (corresponding to "second electrode sheet" in Claims), and two separators 23, 23 each formed using a microporous resin sheet, each having an elongated strip shape with a fixed width, are made to overlap with each other, and are wound into an approximately elongated circular shape with a high flatness ratio. Either one of two separators 23, 23 is interposed between one layer of the positive electrode sheet 21 and one layer of the negative electrode sheet 22 disposed adjacently to one layer of the positive electrode sheet 21. The separators 23, 23 are larger than the positive electrode sheet 21 and the negative electrode sheet 22. With such a configuration, an outermost layer of the electrode assembly 20 is formed of either one of the separators 23. An axis of winding (winding axis) of the positive electrode sheet 21, the negative electrode sheet 22 and two separators 23, 23 is conceptually indicated by symbol X in Fig. 3. The electrode assembly 20 is stored in the inside of the case body 3 in a posture where the winding axis X extends substantially in a direction in which a bottom wall portion and the upper surface opening portion of the case body 3 shown in Fig. 1 face each other in an opposed manner (in a vertical direction in Fig. l).
As shown in Fig. 3, respective end portions of the electrode assembly 20 in a direction in which the winding axis X extends form end surface portions 20a, 20b on which edge portions of the positive electrode sheet 21 in a width direction (lateral direction), edge portions of the negative electrode sheet 22 in a width direction (lateral direction), and edge portions of the separators 23, 23 in a width direction (lateral direction) are disposed. The electrode assembly 20 includes^ a pair of flat portions 20c, 20c which are disposed to opposedly face each other with the winding axis X interposed therebetween and extends in a straight manner in parallel to each other as viewed in a direction in which the winding axis X extends! and a pair of curved portions 20d, 20d which extends in a semi- circularly curved manner as viewed in a direction in which the winding axis X extends and connects the pair of flat portions 20c, 20c to each other.
The flat portion 20c is a portion which extends in a straight manner in design. In a state where the electrode assembly 20 is actually stored in the case 2, the flat portion 20c is not always disposed in a completely straight manner, and there may be a case where the flat portion 20c is disposed in a deflected manner although the flat portion 20c may be formed into an approximately linear shape as a whole.
As shown in Fig. 3 and Fig. 4, the positive electrode sheet 21 includes^ a strip-shaped positive electrode metal foil 24; and positive active material layers 25 which are formed on both surfaces of the positive electrode metal foil 24 respectively. Edge portions on both sides in a width direction (lateral direction) of the positive electrode metal foil 24 are formed in a straight extending manner in a longitudinal direction of the positive electrode metal foil 24. On one side in a width direction of the positive electrode metal foil 24 (a lower side in Fig. 3 and Fig. 4), the positive active material layer 25 is formed so as to reach the edge portion of the positive electrode metal foil 24. On the edge portion on the other side in the width direction of the positive electrode metal foil 24 (an upper side in Fig. 3 and Fig. 4), the positive active material layer 25 is not formed, and a first active material non-formed portion 34 is formed where the positive electrode metal foil 24 is exposed. The first active material non-formed portion 34 of the positive electrode metal foil 24 is covered by an insulation layer 40 described layer (see Fig. 5 to Fig. 8). In Fig. 3, the illustration of the insulation layer 40 is omitted.
Although aluminum is used as a material for forming the positive electrode metal foil 24, for example, metal other than aluminum may be used. As a positive active material, for example, lithium manganate (LiM^O , nickel-cobalt-lithium manganate (LiNixCoyMni-x-yO2), lithium cobaltate (L1C0O2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO , lithium manganese phosphate (LiMnPO , materials formed by using substitution additives in these compounds or mixtures of these compounds can be used. However, other transition metal oxides which contain lithium may be also used.
The negative electrode sheet 22 includes^ a strip-shaped negative electrode metal foil 26; and negative active material layers 27 which are formed on both surfaces of the negative electrode metal foil 26 respectively. Edge portions of the negative electrode metal foil 26 on both sides in a width direction (lateral direction) are formed in a straight extending manner in a longitudinal direction of the negative electrode metal foil 26. On both sides in a width direction of the negative electrode metal foil 26 (an upper side and a lower side in Fig. 3 and Fig. 4), the negative active material layers 27 are formed so as to reach the edge portions of the negative electrode metal foil 26. With such a configuration, respective whole surfaces of the negative electrode metal foil 26 are covered by the negative active material layers 27.
Although copper is used as a material for forming the negative electrode metal foil 26, for example, metal other than copper may be used. As a negative active material, graphite is used, for example. However, materials capable of occluding lithium such as other carbon materials, lithium metal, a lithium alloy, lithium titanate (L^ isO^), silicon, silicon monoxide, or tin, or a mixture of these materials may be used.
In the description made hereinafter, a longitudinal direction of the positive electrode sheet 21, a longitudinal direction of the negative electrode sheet 22, and a longitudinal direction of the separator 23 (directions indicated by an arrow P in Fig. 4 to Fig. 8) are simply referred to as
"longitudinal direction P", a lateral direction of the positive electrode sheet 21, a lateral direction of the negative electrode sheet 22, and a lateral direction of the separator 23 (a direction indicated by an arrow Q in Fig. 4 to Fig. 8) are simply referred to as "lateral direction Q", and a thickness direction of the positive electrode sheet 21, a thickness direction of the negative electrode sheet 22, and a thickness direction of the separator 23 (directions indicated by an arrow R in Fig. 5 to Fig. 8) are simply referred to as "thickness direction R". The longitudinal direction P corresponds to the "first direction" in Claims. The lateral direction Q corresponds to "second direction" in Claims, and is a width direction parallel to the winding axis X (see Fig. 3) of the electrode assembly 20.
As shown in Fig. 4, in the lateral direction Q of the positive electrode sheet 21 and the negative electrode sheet 22, a width of the negative electrode sheet 22 is set larger than a width of the positive electrode sheet 21. The negative electrode sheet 22 projects outward from the edge portion of the positive electrode sheet 21 on both sides in the lateral direction Q. A width of the separator 23 is set larger than the width of the negative electrode sheet 22. The separator 23 projects outward from an edge portion of the negative electrode sheet 22 on both sides in the lateral direction Q.
As shown in Fig. 3 and Fig. 4, on the positive electrode metal foil 24, a plurality of positive electrode tabs (corresponding to "first tab" in Claims) 35 which project outward in the lateral direction Q from the
above-mentioned first active material non-formed portion 34 which extends in a straight manner along the edge portion of the positive electrode metal foil 24 on one side (an upper side in Fig. 3 and Fig. 4) in the lateral direction Q are formed at intervals in the longitudinal direction P. The first active material non-formed portion 34 and the plurality of positive electrode tabs 35 are formed of a sheet of positive electrode metal foil 24, and the respective positive electrode tabs 35 are integrally connected to the first active material non-formed portion 34. The positive electrode tab 35 forms a second active material non-formed portion where an active material layer is not formed on a surface of the positive electrode metal foil 24.
As shown in Fig. 5, at a proximal portion 35a of the positive electrode tab 35, rounded portions 35f are formed on corner portions between edge portions of the positive electrode tab 35 in the longitudinal direction P and an edge portion of the first active material non-formed portion 34 in the lateral direction Q. The rounded portions 35f, 35f are formed on both edge portions of the proximal portion 35a in the longitudinal direction P. With such a configuration, a width of the proximal portion 35a in the longitudinal direction P is gradually increased as the proximal portion 35a approaches the first active material non-formed portion 34. Due to the formation of such rounded portions 35f, 35f, the stress concentration applied to the proximal portion 35a of the positive electrode tab 35, particularly, to the corner portions of the proximal portion 35a can be dispersed so that breakage of the positive tab 35 at the proximal portion 35a can be suppressed. That is, the strength of the proximal portion 35a of the positive electrode tab 35 can be enhanced.
As shown in Fig. 3 and Fig. 4, a plurality of negative electrode tabs (corresponding to "second tab" in Claims) 37 are also formed on the negative electrode metal foil 26 in the same manner as the positive electrode tabs 35. The negative electrode tabs 37 are formed in a projecting manner toward the same side as the positive electrode tabs 35 in the lateral direction Q. Most of the portion of the negative electrode tab 37 except for a proximal end portion is formed into an active material non-formed portion where an active material layer is not formed on the surface of the negative electrode metal foil 26.
As shown in Fig. 3, the electrode assembly 20 which is formed by winding the positive electrode sheet 21, the negative electrode sheet 22 and the separators 23, 23 in a state where the positive electrode sheet 21 and the negative electrode sheet 22 are made to overlap with each other with the separator 23, 23 interposed therebetween has a positive electrode tab bundle (corresponding to "first tab bundle" in Claims) 55 which is formed by stacking a plurality of positive electrode tabs 35. The positive electrode tab bundle 55 is formed on one flat portion 20c of the electrode assembly 20.
The negative electrode tabs 37 are disposed in a spaced-apart manner from the positive electrode tabs 35 in the longitudinal direction P and hence, there is no possibility that the positive electrode tabs 35 and the negative electrode tabs 37 overlap with each other. In the electrode assembly 20 in a winding state, the plurality of negative electrode tabs 37 are made to overlap with each other. With such a configuration, a negative electrode tab bundle 57 which forms the second tab bundle is formed.
The positive electrode tab bundle 55 and the negative electrode tab bundle 57 respectively project from one end surface portion 20a (the end surface portion on an upper side in Fig. 3) of the electrode assembly 20. Further, the positive electrode tab bundle 55 and the negative electrode tab bundle 57 respectively project from one (a viewer's side in Fig. 3) of the pair of flat portions 20c, 20c with respect to a center line Y extending in the longitudinal direction when the end surface portion 20a of the electrode assembly 20 is viewed in the direction in which the winding axis X extends.
As shown in Fig. 2, the positive electrode tab bundle 55 which projects from one flat portion 20c of the electrode assembly 20 is connected to the positive electrode current collector 15 in a state where the positive electrode tab bundle 55 is bent in a falling manner toward the other flat portion 20c side in the thickness direction Z (the direction orthogonal to the winding axis X and the center line Y) of the electrode assembly 20.
In such a state, the respective positive electrode tabs 35 which form the positive electrode tab bundle 55 are curved at the proximal portions 35a thereof (portions ranging from proximal ends to intermediate portions), and distal-end-side portions (portions ranging from distal ends 35c to the intermediate portions) 35b of the respective positive electrode tabs 35 face an upper side of the end surface portion 20a of the electrode assembly 20 and, at the same time, are disposed along a lower surface of the second flat plate portion 15c of the positive electrode current collector 15.
The positive electrode tab bundle 55 is joined to the lower surface of the second flat plate portion 15c of the positive electrode current collector 15 by ultrasonic welding, for example. With such a configuration, the respective positive electrode tabs 35 are electrically connected to the external terminal 11 of the positive electrode through the positive electrode current collector 15.
Although not shown in the drawing, the negative electrode tabs 37 are also electrically connected to the external terminal 12 (see Fig. l) of the negative electrode through the negative current collector (not shown in the drawing) in a state where the negative electrode tabs 37 are bent in the same manner as the positive electrode tabs 35.
Hereinafter, the insulation layer 40 of the positive electrode sheet 21 and the configuration relating to the insulation layer 40 are described with reference to Fig. 5 to Fig. 8.
Fig. 5 is an enlarged view showing the positive electrode tab 35 and portions around the positive electrode tab 35 as viewed from one surface side of the positive electrode sheet 21. Fig. 6 is a cross- sectional view of the first active material non-formed portion 34 and portions around the first active material non-formed portion 34 at a portion displaced from the positive electrode tab 35 in the longitudinal direction P taken along a line B-B in Fig. 5 as viewed in the longitudinal direction P. Fig. 7 is a cross- sectional view of the positive electrode tab 35 and portions around the positive electrode tab 35 taken along a line OC in Fig. 5 as viewed in the longitudinal direction P. Fig. 8 is a cross-sectional view of the positive electrode tab 35 and portions around the positive electrode tab 35 taken along a line D-D in Fig. 5 as viewed in a projecting direction (lateral direction Q) of the positive electrode tab 35.
As shown in Fig. 6 and Fig. 7, in the lateral direction Q, the negative active material layer 27 is disposed in a more outwardly projecting manner than the positive active material layer 25 is. With such a configuration, when the energy storage device 1 is a lithium ion battery, lithium ions emitted from the positive active material layer 25 at the time of charging the energy storage device 1 can be easily occluded by the negative active material layer 27. As shown in Fig. 5 to Fig. 8, the insulation layer 40 is formed on the surface of the positive electrode metal foil 24 such that the insulation layer 40 is disposed adjacently to the edge portion of the positive active material layer 25 along one edge portion of the positive active material layer 25 in the lateral direction Q. The insulation layer 40 is formed on both surfaces of the positive electrode metal foil 24. The insulation layer 40 includes a first insulation layer portion 41 formed on the first active material non-formed portion 34 of the positive electrode metal foil 24, and a second insulation layer portion 42 formed on the positive electrode tab 35 which forms the second active material non-formed portion.
As shown in Fig. 5 and Fig. 6, the first insulation layer portion 41 is formed on surfaces of the first active material non-formed portion 34 on both sides in the same manner. On each surface of the first active material non-formed portion 34, the first insulation layer portion 41 is formed along an upper edge portion of the positive active material layer 25 in the lateral direction Q, and covers an upper edge portion of the positive active material layer 25.
The first insulation layer portion 41 is formed in a projecting manner from an upper end surface 24a of the positive electrode metal foil 24 in the lateral direction Q, and covers the upper end surface 24a. The first insulation layer portion 41 is formed over the entire length of the first active material non-formed portion 34 in the longitudinal direction P. With such a configuration, surfaces of the first active material non-formed portion 34 on both sides and the upper end surface 24a of the first active material non-formed portion 34 are completely covered by the first insulation layer portion 41.
As shown in Fig. 5, the second insulation layer portion 42 is formed in a region including the proximal portion 35a of the positive electrode tab 35. To be more specific, the second insulation layer portion 42 is formed on a portion of the positive electrode tab 35 ranging from a proximal end to an intermediate portion. A distal-end-side portion 35b of the positive electrode tab 35 is exposed without being covered by the insulation layer 40 and hence, the distal-end-side portion 35b and the above-mentioned current collector 15 can be connected to each other.
As shown in Fig. 7, the second insulation layer portion 42 is formed on both surfaces of the positive electrode tab 35 in the same manner. On the respective surfaces of the positive electrode tab 35, the second insulation layer portion 42 is integrally connected to an outer side of the first insulation layer portion 41 in the lateral direction Q. In the lateral direction Q, an upper edge portion 42a of the second insulation layer portion 42 is positioned outside an upper edge portion 22a of the negative electrode sheet 22a and an upper edge portion 23a of the separator 23.
As described above, since the proximal portion 35a of the positive electrode tab 35 is covered by the insulation layer 40, the proximal portion 35a can be reinforced by the insulation layer 40 while suppressing the occurrence of short-circuiting. The positive electrode tab 35 is bent for connection with the current collector 15 as described above (see Fig. 2) and hence, a stress is liable to be concentrated on the proximal portion 35a which is curved by bending. However, the proximal portion 35a is reinforced by the insulation layer 40 and hence, rigidity of the positive electrode tab 35 can be enhanced so that durability of the positive electrode tab 35 can be enhanced.
Further, rigidity of the proximal portion 35a of the positive electrode tab 35 is enhanced by the insulation layer 40 and hence, it is possible to suppress the deflection of the positive electrode tab 35 which warps in a thickness direction R of the positive electrode sheet 21 at the time of winding the positive electrode sheet 21. Accordingly, at the time of making the plurality of positive electrode tabs 35 overlap with each other by winding the positive electrode sheet 21, the hooking engagement between the positive electrode tabs 35 minimally occurs so that breaking of each positive electrode tab 35 can be suppressed. Further, as described above, the rounded portions 35f, 35f are formed on the proximal portion 35a and hence, even when tension is applied to the positive electrode sheet 21 at the time of winding the positive electrode sheet 21, the stress concentration to the proximal portion 35a is alleviated so that the strength of the proximal portion 35a is further enhanced.
As shown in Fig. 8, the second insulation layer portion 42 of the insulation layer 40 projects outward from the positive electrode tab 35 on both sides in the longitudinal direction P, and covers side edge surfaces 35d, 35e on both sides of the positive electrode tab 35. With such a configuration, the proximal portion 35a of the positive electrode tab 35 is configured such that surfaces of the positive electrode tab 35 on both sides and side edge surfaces 35d, 35e of the positive electrode tab 35 on both sides are covered by the second insulation layer portion 42.
As a material for forming the insulation layer 40, an insulation material having high electric resistivity is used. As a specific material for forming the insulation layer 40, for example, a mixture of inorganic and/or organic particles and a binder is used. As the inorganic particles, for example, particles made of alumina (AI2O3), S1O2, Zr02, T1O2 or MgO are used, and as the organic particles, for example, polyimide powder is used. As the binder, for example, polyvinylidene fluoride (PVDF),
polytetrafluoroethylene (PTFE), polyimide or polyamide is used.
As shown in Fig. 6 and Fig. 7, the insulation layer 40 is disposed such that the insulation layer 40 faces the negative active material layer 27 with the separator 23 interposed therebetween. Particularly, the second insulation layer portion 42 of the insulation layer 40 projects from the upper edge portion 23a of the separator 23 in the lateral direction Q. Accordingly, even when a portion where the separator 23 is not interposed between the first active material non-formed portion 34 and the proximal portion 35a of the positive electrode tab 35 of the positive electrode sheet 21 and the negative active material layer 27 is formed due to various causes including positional displacement, shrinkage or breakage of the separator 23 so that the positive electrode sheet 21 and the negative electrode sheet 22 are brought into contact with each other by any chance, the insulation layer 40 which covers a metal portion of the positive electrode sheet 21 is interposed between the metal foil 24 at the first active material non-formed portion 34 and the positive electrode tab 35 and the negative active material layer 27 and hence, the occurrence of short-circuiting can be prevented.
As shown in Fig. 6 and Fig. 8, the insulation layer 40 covers not only surfaces of the first active material non-formed portion 34 and the proximal portion 35a of the positive electrode tab 35 on both sides but also the upper end surface 24a of the first active material non-formed portion 34 and side edge surfaces 35d, 35e of the positive electrode tab 35 and hence, the occurrence of short-circuiting can be further effectively suppressed.
Assuming that metal such as copper which is melted at a positive electrode potential is mixed into the positive electrode metal foil 24, such metal is melted on the positive electrode metal foil 24. When such melted metal precipitates on the negative electrode sheet 22 and the precipitate of the metal grows and is brought into contact with the positive electrode sheet 21, short-circuiting occurs.
However, according to this embodiment, as shown in Fig. 6 and Fig. 7, the positive electrode metal foil 24 is covered by the insulation layer 40 and hence, melting of metal on the positive electrode metal foil 24 positioned in the vicinity of the negative electrode sheet 22 can be prevented so that the precipitation of metal on the negative electrode sheet 22 can be suppressed whereby the occurrence of short-circuiting attributed to metal precipitate can be prevented.
Further, the upper end surface 24a of the first active material non-formed portion 34 is covered by the insulation layer 40 and hence, while suppressing short-circuiting at the upper end surface 24a, the upper end surface 24a can be easily disposed close to the upper edge portion 23a of the separator 23 positioned outside the upper end surface 24a in the lateral direction Q. Accordingly, the positive electrode metal foil 24 can be expanded in the lateral direction Q so that battery capacity can be increased.
The positive electrode tab 35 is formed by cutting the positive electrode metal foil 24 into a predetermined shape. To be more specific, the positive electrode tabs 35 can be formed by cutting portions of the positive electrode metal foil 24 except for portions of the positive electrode metal foil 24 which correspond to the positive electrode tabs 35 at one edge portion of the positive electrode metal foil 24 in the lateral direction Q.
The above-mentioned upper end surface 24a of the first active material non-formed portion 34 and side edge surfaces 35d, 35e of the positive electrode tab 35 are formed by cutting the positive electrode metal foil 24 as described above and, thereafter, the insulation layer 40 is formed. In this manner, the formation of the insulation layer 40 is performed after the positive electrode metal foil 24 is cut and hence, the end surface 24a of the first active material non-formed portion 34 and the side edge surfaces 35d, 35e of the positive electrode tab 35 can be covered by the insulation layer 40.
The insulation layer 40 is formed by applying a paste-like material by coating using a slot die method, for example. However, a method for forming the insulation layer 40 is not limited to such a method. For example, the insulation layer 40 may be formed by electrostatic powder coating.
Although the present invention has been described with reference to the above-mentioned embodiment heretofore, the present invention is not limited to the above-mentioned embodiment.
For example, in the above-mentioned embodiment, the description is made with respect to the energy storage device 1 which includes a so-called winding-type electrode assembly 20. However, the present invention is also applicable to an energy storage device which includes a so-called stacking type electrode assembly 120 (corresponding to "layered product" in Claims) as shown in Fig. 9, for example.
The electrode assembly 120 shown in Fig. 9 is a layered product which is formed of a plurality of positive electrode sheets (corresponding to "first electrode sheet" in Claims) 121 and a plurality of negative electrode sheets (corresponding to "second electrode sheet" in Claims) 122 where the positive electrode sheet 121 and the negative electrode sheet 122 are stacked alternately with a separator 123 interposed therebetween. Each positive electrode sheet includes a first active material non-formed portion 34 and a positive electrode tab 35 which forms a second active material non-formed portion in the same manner as the above-mentioned embodiment, and each negative electrode sheet 122 includes a negative electrode tab 37 in the same manner as the above-mentioned embodiment. The electrode assembly 120 includes^ a positive electrode tab bundle which is formed by stacking the positive electrode tabs 35 formed on the respective positive electrode sheets 121; and a negative electrode tab bundle which is formed by stacking the negative electrode tabs 37 formed on the respective negative electrode sheets 122.
Also in such a stacking-type electrode assembly 120, by forming an insulation layer 40 on the first active material non-formed portion 34 and positive electrode tabs 35 of the respective positive electrode sheet 121 in the same manner as the above-mentioned embodiment, the energy storage device of this embodiment can acquire substantially the same advantageous effects as the above-mentioned embodiment such as an effect that a proximal portion of the tab 35 on which a stress is liable to be concentrated due to bending of the positive electrode tab 35 can be reinforced by an insulation layer.
Further, in the above-mentioned embodiment, the description has been made by taking as an example the case where "first direction" in which the edge portion of the positive electrode sheet 21 which forms the first active material non-formed portion 34 extends and "second direction" in which the positive electrode tab 35 projects from the edge portion are orthogonal to each other. However, in the present invention, the second direction may be inclined with respect to the direction orthogonal to the first direction.
In the above-mentioned embodiment, the description has been made by taking as an example the case where the first electrode sheet on which the insulation layer is formed is the positive electrode sheet. However, the present invention is also applicable to the case where the first electrode sheet is a negative electrode sheet.
In the present invention, a metal foil of the first electrode sheet may not be always made of only metal, and a conductive coating layer (film) made of a resin or the like may be formed on a surface of metal.
In the present invention, the insulation layer formed on the surface of the metal foil of the first electrode sheet may be formed in an overlapping manner on the surface of the edge portion of the active material layer or may be formed on the whole surface of the active material layer by overcoating.
In the above-mentioned embodiment, the description has been made by taking as an example a case where the insulation layer is formed not only on the surfaces of the metal foil of the first electrode sheet but also on the end surfaces of the metal foil of the first electrode sheet. However, in the present invention, the insulation layer may not be always formed on the end surfaces of the metal foil. When the insulation layer is not formed on the end surfaces of the metal foil, cutting of the first electrode sheet for forming the first tab may be performed after the insulation layer is formed on the surfaces of the metal foil.
Further, in the above-mentioned embodiment, the description has been made by taking the case where the rounded portions are formed on the proximal portion of the first tab as an example. However, in the present invention, the rounded portions may not be always formed on the proximal portion of the first tab.
DESCRIPTION OF REFERENCE SIGNS
1 energy storage device
11 positive electrode external terminal
15 positive electrode current collector
20 electrode assembly (winding body)
20c flat portion
20d curved portion
21 positive electrode sheet (first electrode sheet)
22 negative electrode sheet (second electrode sheet)
22a edge portion of negative electrode sheet
23 separator
23a edge portion of separator
24 positive electrode metal foil 24a end surface of positive electrode metal foil
25 positive active material layer
34 first active material non-formed portion
35 positive electrode tab (first tab) (second active material non-formed portion)
35a proximal portion of positive electrode tab
35c distal end of positive electrode tab
35d, 35e side edge surface of positive electrode tab
37 negative electrode tab (second tab)
40 insulation layer
41 first insulation layer portion
42 second insulation layer portion
42a edge portion of second insulation layer portion
55 positive electrode tab bundle (first tab bundle)
57 negative electrode tab bundle (second tab bundle)
120 electrode assembly (layered product)
121 positive electrode sheet (first electrode sheet)
122 negative electrode sheet (second electrode sheet)
123 separator
P longitudinal direction of sheet (first direction)
Q lateral direction of sheet (second direction)
X winding axis

Claims

1. An energy storage device comprising: a first electrode sheet; and a second electrode sheet stacked on the first electrode sheet with a separator interposed between the first electrode sheet and the second electrode sheet and having a polarity different from a polarity of the first electrode sheet, wherein
the first electrode sheet includes:
a metal foil having an edge portion extending in a first direction in a straight manner, and a first tab projecting from the edge portion in a second direction which intersects with the first direction!
an active material layer formed on a surface of the metal foil! and an insulation layer formed on the surface of the metal foil, a portion extending along the edge portion and the first tab of the metal foil are formed into an active material non-formed portion where the active material layer is not formed, and
the insulation layer is formed on the active material non-formed portion.
2. The energy storage device according to claim 1, wherein the insulation layer is formed in a region of the active material non-formed portion which includes a proximal portion of the first tab.
3. The energy storage device according to claim 2, wherein the first tab is rounded at the proximal portion thereof.
4. The energy storage device according to claim 2 or claim 3, further comprising a current collector which electrically connects the first electrode sheet to an external terminal, wherein
the first tab is connected to the current collector in a bent state.
5. The energy storage device according to any one of claims 2 to 4, wherein a portion of the insulation layer formed on a surface of the first tab projects from an edge portion of the separator in the second direction.
6. The energy storage device according to any one of claims 1 to 5, wherein the insulation layer is also formed on an end surface of the metal foil in the active material non-formed portion.
7. The energy storage device according to any one of claims 1 to 6, wherein the second electrode sheet has an edge portion extending in a straight manner in the first direction, and a second tab extending in the second direction from the edge portion, and
the first tab and the second tab project toward the same side in the second direction, and are disposed in a spaced-apart manner from each other in the first direction.
8. The energy storage device according to any one of claims 1 to 7, wherein the first electrode sheet has a plurality of the first tabs disposed in a spaced-apart manner in the first direction,
a winding body is formed by winding the first electrode sheet and the second electrode sheet around an axis parallel to the second direction while the first electrode sheet and the second electrode sheet are made to overlap with each other with the separator interposed therebetween, and
the winding body has a first tab bundle formed by stacking the plurality of first tabs.
9. The energy storage device according to claim 8, wherein the winding body includes a pair of flat portions extending in a straight manner parallel to each other as viewed in a direction in which the axis extends, and a pair of curved portions connecting the pair of flat portions to each other, and
the first tab bundle is provided to the flat portion.
10. The energy storage device according to any one of claims 1 to 7, wherein the energy storage device includes a layered product which is formed of a plurality of the first electrode sheets and a plurality of the second electrode sheets where the first electrode sheet and the second electrode sheet are stacked alternately with the separator interposed between the first electrode sheet and the second electrode sheet, and
the layered product includes the first tab bundle formed by stacking the first tabs respectively formed on the plurality of first electrode sheets.
PCT/EP2017/057054 2016-04-08 2017-03-24 Energy storage device WO2017174374A1 (en)

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JP2017188371A (en) 2017-10-12
DE112017001858T5 (en) 2018-12-27
CN108886128B (en) 2023-01-13
CN116259897A (en) 2023-06-13
JP2022023106A (en) 2022-02-07
JP2022023105A (en) 2022-02-07
JP2023126819A (en) 2023-09-12
CN108886128A (en) 2018-11-23

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