WO2018141723A1 - Energy storage system and charge method - Google Patents

Energy storage system and charge method Download PDF

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Publication number
WO2018141723A1
WO2018141723A1 PCT/EP2018/052228 EP2018052228W WO2018141723A1 WO 2018141723 A1 WO2018141723 A1 WO 2018141723A1 EP 2018052228 W EP2018052228 W EP 2018052228W WO 2018141723 A1 WO2018141723 A1 WO 2018141723A1
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WIPO (PCT)
Prior art keywords
active material
energy storage
material layer
negative
reference electrode
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Application number
PCT/EP2018/052228
Other languages
French (fr)
Inventor
Hideki Masuda
Original Assignee
Lithium Energy and Power GmbH & Co. KG
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Publication date
Application filed by Lithium Energy and Power GmbH & Co. KG filed Critical Lithium Energy and Power GmbH & Co. KG
Publication of WO2018141723A1 publication Critical patent/WO2018141723A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • 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 system and a charge method.
  • Nonaqueous electrolyte secondary batteries typified by a lithium ion secondary battery are frequently used in personal computers, electronic devices such as a communication terminal, and automobiles.
  • a nonaqueous electrolyte secondary battery typically includes a pair of electrodes which are electrically separated by a separator and a nonaqueous electrolyte
  • Such a nonaqueous electrolyte secondary battery is configured to perform charge and discharge by transferring ions between the electrodes.
  • capacitors such as a lithium ion capacitor and an electric double layer capacitor have also become widespread as energy storage devices other than the nonaqueous electrolyte secondary battery.
  • a reference electrode is required to accurately measure a potential of an electrode in these energy storage devices.
  • a reference electrode for a negative electrode is disposed between the negative electrode and a separator.
  • a reference electrode is disposed on a negative electrode plate with an insulating member interposed therebetween.
  • Patent Document l JP-A-2016-143452
  • electrodeposition of metal (typically, lithium) dissolved in a nonaqueous solvent occurs, which accelerates the deterioration of the energy storage apparatus.
  • the electrodeposition is particularly likely to occur when charging is performed with a large current.
  • a technique capable of more accurately grasping the potential on the surface of the negative active material layer is required.
  • an object thereof is to provide an energy storage system and a charge method that are capable of reducing the occurrence of electrodeposition on the surface of a negative active material layer during charging.
  • an energy storage system including: an energy storage device, the energy storage device including a negative electrode plate including a negative active material layer, a nonaqueous electrolyte, and a reference electrode disposed in contact with the
  • nonaqueous electrolyte! and an arithmetic unit that estimates a potential on a surface of the negative active material layer from a measured potential of the reference electrode.
  • Another embodiment of the present invention provides a charge method including stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer using the energy storage system.
  • an energy storage system and a charge method that are capable of reducing the occurrence of electrodeposition on the surface of a negative active material layer during charging.
  • Fig. 1 is a schematic view of an energy storage system according to a first embodiment of the present invention.
  • Fig. 2 is a schematic perspective view of an electrode assembly of the energy storage system of Fig. 1.
  • Fig. 3 is a partial sectional view of the electrode assembly of Fig. 2 taken along line A- A.
  • Fig. 4 is a partial sectional view of an electrode assembly of an energy storage system according to a second embodiment of the present invention.
  • Fig. 5 is a partial sectional view of an electrode assembly of an energy storage system according to a third embodiment of the present invention.
  • Fig. 6 is a plan view of an electrode assembly of an energy storage system according to a fourth embodiment of the present invention.
  • Fig, 7(a) is a plan view of a negative electrode plate of the electrode assembly of Fig. 6
  • Fig. 7(b) is a plan view of a separator and the like of the electrode assembly of Fig. 6
  • Fig. 7(c) is a plan view of a positive electrode plate of the electrode assembly of Fig. 6.
  • Fig. 8 is a plan view of an electrode assembly of an energy storage system according to a fifth embodiment of the present invention.
  • Fig. 9(a) is a plan view of a positive electrode plate and the like of the electrode assembly of Fig. 8
  • Fig. 9(b) is a plan view of a separator of the electrode assembly of Fig. 8
  • Fig. 9(c) is a plan view of a negative electrode plate of the electrode assembly of Fig. 8.
  • Fig. 10 is a perspective view schematically illustrating a part of an energy storage device provided in an energy storage system according to a sixth embodiment of the present invention.
  • Fig. 11 is a schematic view of an energy storage apparatus provided in an energy storage system according to an embodiment of the present invention.
  • An energy storage system includes : an energy storage device, the energy storage device including a negative electrode plate including a negative active material layer, a nonaqueous electrolyte, and a reference electrode disposed in contact with the nonaqueous electrolyte! and an arithmetic unit that estimates a potential on a surface of the negative active material layer from a measured potential of the reference electrode.
  • the energy storage system includes the arithmetic unit that estimates the potential on the surface of the negative active material layer from the measured potential of the reference electrode. Thus, it is possible to obtain the potential on the surface of the negative active material with high accuracy. Thus, according to the energy storage system, it is possible to grasp the potential on the surface of the negative active material layer with high accuracy during charging, and stop the charging and control a charge current according to the potential. As a result, it is possible to reduce the occurrence of electrodeposition of lithium or the like.
  • the “lithium or the like” indicates a metal that constitutes an electrolyte salt dissolved in the nonaqueous electrolyte.
  • the “lithium or the like” is typically lithium, but may be another metal.
  • the energy storage device may include a positive electrode plate including a positive active material layer, and the reference electrode may be disposed in a region where the positive active material layer and the negative active material layer are not opposed to each other.
  • the reference electrode When the reference electrode is present between the positive active material layer and the negative active material layer, the flow of ions between the active material layers is blocked in the part where the reference electrode is present. Thus, the flow of ions is concentrated on the negative active material layer around the reference electrode, and electrodeposition is likely to occur in this part. Thus, it is possible to suppress the uneven distribution of the flow of ions and further reduce the occurrence of electrodeposition by disposing the reference electrode in the region where the positive active material layer and the negative active material layer are not opposed to each other.
  • the positive electrode plate may include a positive electrode substrate, the positive active material layer may be formed on a part of the positive electrode substrate, the negative electrode plate may include a negative electrode substrate, the negative active material layer may be formed on a part of the negative electrode substrate, and the reference electrode may be disposed on a surface of the positive electrode substrate or a surface of the negative electrode substrate.
  • the reference electrode may be disposed on the surface of the negative active material layer.
  • the energy storage device may include a separator disposed between the positive electrode plate and the negative electrode plate, and the reference electrode may be disposed on a surface of the separator.
  • the reference electrode may be disposed on an end face of the positive electrode plate or an end face of the negative electrode plate.
  • the reference electrode can be disposed on one of the locations ⁇ the surface of the positive electrode substrate! the surface of the negative electrode substrate! the surface of the positive active material layer! the surface of the negative active material layer! the surface of the separator! the end face of the positive electrode plate! and the end face of the negative electrode plate.
  • the positive electrode plate may have a cut-away part where the positive active material layer is not formed, and the reference electrode may be disposed in the cut-away part.
  • the cut-away part is surrounded by the positive active material layer and thus has a high ion infiltration
  • a change in the potential can be detected from the filtration concentration by disposing the reference electrode in the cut-away part.
  • the reference electrode may be disposed on a surface of a connector that connects the negative electrode plate to an external terminal.
  • the surface of the connector is also one of spaces that have a small influence on the charge- discharge reaction and are empty. Thus, it is possible to improve the accuracy of the estimation of the potential while preventing upsizing of the energy storage device by disposing the reference electrode on the surface of the connector.
  • the energy storage system may further include a control unit that stops charging or controls a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer.
  • the energy storage system further provided with the control unit makes it possible to stop charging or control a charge current according to the obtained potential on the surface of the negative active material layer.
  • a charge method includes stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer using the energy storage system.
  • the charge method is capable of estimating the potential on the surface of the negative active material layer during charging with high accuracy. Thus, it is possible to reduce the occurrence of electrodeposition on the surface of the negative active material layer by, for example, controlling a charge current.
  • An energy storage system 10 illustrated in Fig. 1 includes an energy storage device 11 and a battery charger 12.
  • the energy storage device 11 includes, as external terminals, a positive electrode terminal 11a, a negative electrode terminal lib, and a reference electrode terminal 11c.
  • the battery charger 12 is connected to these external terminals of the energy storage device 11.
  • the energy storage device 11 includes a positive electrode plate, a negative electrode plate, and a nonaqueous electrolyte.
  • a nonaqueous electrolyte secondary battery will be described as an example of the energy storage device 11.
  • the positive electrode plate and the negative electrode plate are typically alternately layered by stacking or winding with a separator interposed therebetween to form an electrode assembly.
  • Figs. 2 and 3 illustrate the structure of a wound-type electrode assembly 15 in the first embodiment.
  • Fig. 2 schematically illustrates the electrode assembly 15, which is a band-shaped layered product, in a wound state.
  • the electrode assembly 15 has a structure in which a positive electrode plate 16, a negative electrode plate 17, and two separators 18, 19 are stacked.
  • the electrode assembly 15 further includes a reference electrode 20 which is disposed on the negative electrode plate 17.
  • Fig. 3 schematically illustrates the elements (the positive electrode plate 16, the first separator 18, the negative electrode plate 17, and the second separator 19) of the electrode assembly 15 in a separated manner. However, adjacent ones of the elements are typically in contact with each other. [0027]
  • the electrode assembly 15 in a wound state in Fig. 2 is stored in a case, and the case is filled with the nonaqueous electrolyte.
  • Fig. 2 illustrates the electrode assembly 15 whose tip part is not wound for the purpose of description. However, the electrode assembly 15 stored inside the case is wound up to the tip part thereof (refer to an electrode assembly 92 of Fig. 10).
  • the positive electrode plate 16, the negative electrode plate 17, the separators 18, 19, and the reference electrode 20 which constitute the electrode assembly 15 of the energy storage device 11 are in contact with the nonaqueous electrolyte.
  • One end part 15a in the axial direction of the electrode assembly 15 of Fig. 2 is connected to the positive electrode terminal 11a of Fig. 1 through a connector (not illustrated).
  • the other end part 15b in the axial direction of the electrode assembly 15 of Fig. 2 is connected to the negative electrode terminal lib of Fig. 1 through a connector (not illustrated).
  • a known aluminum or resin case, which is typically used as a case for secondary battery, can be used as the case described above.
  • the electrode assembly 15 will be described in detail with reference to, mainly, Fig. 3.
  • the positive electrode plate 16 includes a positive electrode substrate 21 and a positive active material layer 22 which is formed on a part of each face of the positive electrode substrate 21.
  • the positive electrode plate 16 may further include an intermediate layer (not illustrated) which is formed between the positive electrode substrate 21 and the positive active material layer 22.
  • the positive electrode substrate 21 has a band shape and has conductivity.
  • a metal such as aluminum, titanium, tantalum, or stainless steel, or an alloy thereof is used as a material of the positive electrode substrate 21.
  • a metal foil such as an aluminum foil can be preferably used as the positive electrode substrate 21.
  • the positive active material layer 22 is formed on a part of the positive electrode substrate 21. Specifically, the positive active material layer 22 is formed in a longitudinal direction of the positive electrode substrate 21 except both faces of one side end (the left side end in Fig. 3) thereof. That is, the positive electrode substrate 21 is exposed in the one end part 15a (refer to Fig. 2) of the electrode assembly 15.
  • the positive active material layer 22 is formed of a so-called positive electrode mixture containing a positive active material.
  • the positive electrode mixture which forms the positive active material layer 22 contains an optional component such as a conductive agent, a binder (binding agent), a thickener, or a filler as needed.
  • Examples of the positive active material include composite oxides represented by Li x MO y (M represents at least one kind of transition metal) (Li x Co02, Li x Ni02, Li x Mn03, Li x Ni a Co(i- a )02, and Li x Ni a MnpCo(i- a -p)02 each having a layered orNaFe02 crystal structure and Li x Mn204 and LixNi a Mn(2-a)04 each having a spinel crystal structure) and polyanion compounds represented by Li w Me x (XOy) z (Me represents at least one kind of transition metal and X represents, for example, P, Si, B, V) (LiFeP04, LiMnP0 4 , LiNiP0 4 , LiCoP0 4 , Li 3 V 2 (P0 4 )3, Li 2 MnSi0 4 , and Li 2 CoP0 4 F).
  • An element or polyanion in these compounds may be partially substitute
  • the negative electrode plate 17 includes a negative electrode substrate 23 and a negative active material layer 24 which is formed on a part of each face of the negative electrode substrate 23.
  • the negative electrode plate 17 may further include an intermediate layer (not illustrated) which is formed between the negative electrode substrate 23 and the negative active material layer 24.
  • the negative electrode substrate 23 may have a structure similar to that of the positive electrode substrate 21.
  • a metal such as copper, nickel, stainless steel, or nickel-plated steel, or an alloy thereof is used as a material of the negative electrode substrate 23, and copper or a copper alloy is preferred. That is, a copper foil is preferably used as the negative electrode substrate 23.
  • the negative active material layer 24 is formed on a part of the negative electrode substrate 23. Specifically, the negative active material layer 24 is formed in a longitudinal direction of the negative electrode substrate 23 except both faces of one side end (the right side end in Fig. 3) thereof. That is, the negative electrode substrate 23 is exposed in the other end part 15b (refer to Fig. 2) of the electrode assembly 15.
  • the negative active material layer 24 is formed of a so-called negative electrode mixture containing a negative active material.
  • the negative electrode mixture which forms the negative active material layer 24 contains an optional component such as a conductive agent, a binder
  • binding agent a thickener, or a filler as needed.
  • Examples of the negative active material include metals or
  • semimetals such as Si and Sn! metal oxides or semimetal oxides such as a Si oxide and a Sn oxide! polyphosphoric acid compounds! and carbon materials such as graphite and amorphous carbon (easily graphitizable carbon or hardly graphitizable carbon).
  • Each of the separators 18, 19 has an insulation property and porosity.
  • a woven fabric, a nonwoven fabric, or a porous resin film is used as a material of the separators 18, 19.
  • a porous resin film is preferred in view of strength
  • a nonwoven fabric is preferred in view of the retention of the nonaqueous electrolyte.
  • polyolefin such as polyethylene or polypropylene is preferred in view of strength
  • polyimide or aramid is preferred in view of resistance to oxidative decomposition.
  • a separator that includes a substrate made of a resin and an inorganic layer which is stacked on the surface of the substrate may be used.
  • the reference electrode 20 is disposed on the surface of the negative electrode substrate 23. Specifically, the reference electrode 20 is stacked on the exposed part of the negative electrode substrate 23 at the end part of the negative electrode plate 17 with an insulating member 25 interposed therebetween.
  • the shape of the reference electrode 20 is not particularly limited and may be a circular shape or a rectangular shape in plan view.
  • the shape of the reference electrode 20 may be, for example, a plate-like shape or a rod-like shape. In this case, a metal foil or a metal wire can be used.
  • the size of the reference electrode 20 is not particularly limited.
  • the total thickness of the reference electrode 20 and the insulating member 25 which covers the reference electrode 20 may be equal to or less than the thickness of the negative active material layer 24. This makes it possible to prevent an increase in the thickness of a location where the reference electrode 20 is disposed in the electrode assembly 15.
  • the reference electrode 20 is electrically connected to the reference electrode terminal 11c (refer to Fig. l), which is an external terminal, through a connector (e.g., a leading wire having an insulated surface, not illustrated).
  • a connector e.g., a leading wire having an insulated surface, not illustrated.
  • the reference electrode 20 is not disposed in an opposed region X between the positive active material layer 22 and the negative active material layer 24. That is, the reference electrode 20 is disposed in a region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other.
  • the insulating member 25 covers the reference electrode 20.
  • the insulating member 25 has an insulation property and porosity. That is, the insulating member 25 transmits the nonaqueous electrolyte (ion), but insulates electricity.
  • the reference electrode 20 is disposed with the insulating member 25 interposed, it is possible to measure an accurate potential in the disposed location. A part of the reference electrode 20 may be exposed without being covered with the insulating member 25 as long as an electrically insulated state between the negative electrode substrate 23 and the reference electrode 20 can be ensured.
  • the insulating member 25 disposed between the reference electrode 20 and the negative electrode substrate 23 may be a nonporous member.
  • the insulating member 25 can be formed of, for example, an insulating particle and a binder.
  • the insulating member 25 may contain another component other than the insulating particle and the binder.
  • the insulating particle may either be an inorganic particle or an organic particle.
  • an inorganic particle is preferred in view of resistance to heat.
  • the inorganic particle include inorganic oxides such as silica, alumina, titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide and inorganic nitrides such as silicon nitride, titanium nitride, and boron nitride.
  • examples of the inorganic particle include silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin cray, kaolinite, boehmite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, aluminosilicate, calcium silicate, magnesium silicate, diatom earth, silica sand, and glass.
  • a binder that is capable of fixing the insulating particle and electrochemically stable in a used range is typically used as the binder described above.
  • the binder include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF)), polyethylene, polypropylene, and polyimide! elastomers such as ethylene-propylene- diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluoro rubber! and polysaccharide polymers.
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene difluoride
  • EPDM ethylene-propylene- diene rubber
  • SBR styrene-butadiene rubber
  • the insulating member 25 may be formed of a woven fabric, a nonwoven fabric, or a porous resin film similarly to the separators 18, 19.
  • a known nonaqueous electrolyte which is typically used in a nonaqueous electrolyte secondary battery is used as the nonaqueous electrolyte described above.
  • a nonaqueous electrolyte that contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent can be used as the nonaqueous electrolyte described above.
  • nonaqueous solvent examples include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).
  • cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC)
  • chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).
  • Examples of the electrolyte salt include lithium salt, sodium salt, potassium salt, magnesium salt, and onium salt. Among these salts, lithium salt is preferred.
  • Examples of the lithium salt include inorganic lithium salts such as LiPF 6 , LiP0 2 F 2 , LiBF 4 , LiC10 4 , and LiN(S0 2 F) 2 , and lithium salts having a fluorohydrocarbon group such as L1SO3CF3,
  • LiN(S0 2 CF 3 ) 2 LiN(S0 2 C 2 F 5 ) 2 , LiN(S0 2 CF 3 ) (S0 2 C 4 F 9 ), LiC(S0 2 CF 3 ) 3 , and LiC(S0 2 C 2 F 5 ) 3 .
  • an ordinary temperature molten salt, an ion liquid, or a polymer solid electrolyte can also be used as the nonaqueous electrolyte.
  • the battery charger 12 of Fig. 1 includes an arithmetic unit 13 and a control unit 14.
  • the battery charger 12 further includes a voltmeter and a charge circuit (not illustrated).
  • the voltmeter measures a potential of the reference electrode terminal 11c which is electrically connected to the reference electrode 20.
  • the voltmeter may be configured to measure a potential difference (voltage) between any two of the positive electrode terminal 11a (positive electrode plate 16), the negative electrode terminal lib (negative electrode plate 17), and the reference electrode terminal 11c (reference electrode 20).
  • the arithmetic unit 13 estimates a potential on a surface Y (refer to Fig. 3) of the negative active material layer 24 of the energy storage device 11 from the measured potential of the reference electrode 20.
  • the estimation of the surface potential can be performed on the basis of a known model such as the Newman model.
  • the estimation can be performed on the basis of parameters such as the electric conductivity and the thickness of the negative electrode substrate 23, the electric conductivity, the thickness, the active material diameter, the porosity, the diffusion coefficient, and the reaction speed constant of the negative active material layer 24, the diffusion coefficient, the electrolyte salt concentration, and the ion conductivity of the nonaqueous electrolyte, and the positional relationship (e.g., distance) between the reference electrode 20 and the negative active material layer 24. These parameters are appropriately set on the basis of the disposed location of the reference electrode.
  • the estimation of the surface potential by the arithmetic unit 13 may be performed on the basis of database on which measured values of the potential of the reference electrode 20 and the potential on the surface Y of the negative active material layer 24
  • the battery charger 12 convers power from a power source to power suitable for charging in the charge circuit in accordance with control of the control unit 14 and outputs the converted power between the positive electrode terminal 11a and the negative electrode terminal lib. Accordingly, the energy storage device 11 is charged with electricity. Further, the control unit 14 stops the charging or controls a charge current on the basis of an estimated value of the potential on the surface Y of the negative active material layer 24 estimated by the arithmetic unit 13.
  • the arithmetic unit 13 and the control unit 14 may include a computer and a computer program.
  • the arithmetic unit 13 and the control unit 14 may include a processor that is partially or entirely composed of a semiconductor chip.
  • the arithmetic unit 13 and the control unit 14 may be separate components, may be an integrated component, or may be integrated with another component of the battery charger 12.
  • a charge method includes stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface Y of the negative active material layer 24 using the energy storage system 10.
  • the charge method may further include measuring a potential of the reference electrode 20 and estimating the potential on the surface Y of the negative active material layer 24 on the basis of the measured potential of the reference electrode 20.
  • the energy storage system 10 is capable of estimating the potential on the surface Y of the negative active material layer 24 from the measured potential of the reference electrode 20 by the arithmetic unit 13. Thus, it is possible to obtain the potential on the surface Y of the negative active material layer 24 with high accuracy. That is, according to the energy storage system 10, it is possible to grasp the potential on the surface Y of the negative active material layer 24 with high accuracy during charging, and stop the charging or control a charge current in accordance with the potential by the control unit 14. As a result, it is possible to reduce the occurrence of electrodeposition of lithium or the like.
  • the charge current can be controlled so that the estimated potential on the surface Y of the negative active material layer 24 does not become 0 V (vs. Li/Li + ) or less.
  • the reference electrode 20 is disposed in the region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other. Thus, it is possible to suppress the uneven distribution of the flow of ions (nonaqueous electrolyte) and further reduce the occurrence of electrodeposition.
  • the reference electrode 20 is disposed on the surface of the negative electrode substrate 23 in a
  • An electrode assembly which includes a positive electrode plate, a negative electrode plate, and a separator is wound in such a manner that a substrate part of each of the positive electrode plate and the negative electrode plate which is not opposed to the separator, that is, the tip part is exposed, and the exposed substrate parts are tied into a bundle and joined to a connector (refer to Fig. 10). That is, in the structure in which the electrode assembly and the connector are joined in this manner, the non-opposed region, which is not opposed to the separator 18, in the negative electrode substrate 23 is in an exposed state.
  • the reference electrode 20 can be easily disposed in such an exposed part of the substrate (negative electrode substrate 23). That is, the structure in which the reference electrode is disposed on the surface of the substrate (the positive electrode substrate or the negative electrode
  • the reference electrode 20 may be disposed on the surface of the negative electrode substrate 23 in a region opposed to the separator 18. In this case, the reference electrode 20 can be disposed at a position closer to the negative active material layer 24. Thus, it is possible to estimate the potential on the surface of the negative active material layer 24 with high accuracy. In this case, it is possible to prevent an increase in the thickness of the location where the reference electrode 20 is disposed in the electrode assembly 15 by, for example, setting the total thickness of the reference electrode 20 and the insulating member 25 which covers the reference electrode 20 to equal to or less than the thickness of the negative active material layer 24.
  • the reference electrode 20 is disposed on the surface of the negative electrode substrate 23 in the energy storage system 10 described above, the reference electrode 20 may alternatively be disposed on the surface of the positive electrode substrate 21. Also in this case, it is possible to estimate the surface potential of the negative active material layer 24 from the potential of the reference electrode 20 by the arithmetic unit 13. However, the reference electrode 20 disposed on the surface of the negative electrode substrate 23 which is close to the negative active material layer 24 as illustrated in Fig. 3 improves the accuracy of the estimation of the surface potential of the negative active material layer 24.
  • Fig. 4 illustrates an electrode assembly 30 provided in an energy storage system according to a second embodiment. As for the
  • a reference electrode 31 is disposed on the surface of a negative active material layer 24. Specifically, the reference electrode 31 is stacked on the surface of an end part of the negative active material layer 24 with an insulating member 32 interposed therebetween.
  • the electrode assembly 30 of Fig. 4 is the same as the electrode assembly 15 of Fig. 3 of the first embodiment except the disposed location of the reference electrode 31 and the insulating member 32.
  • the other constituent members are denoted by reference signs identical to the reference signs of the electrode assembly 15 of Fig. 3, and description thereof will be omitted.
  • the reference electrode 31 is disposed on the surface of the negative active material layer 24.
  • a part other than the disposed location of the reference electrode 31 and the insulating member 32, that is, the material and the like are the same as those of the electrode assembly 15 of the first embodiment.
  • the positive electrode plate, the negative electrode plate, and the reference electrode are electrically connected to corresponding external terminals through connectors similarly to the first embodiment (the same applies to other embodiments described below).
  • the reference electrode 31 is not disposed in an opposed region X between the positive active material layer 22 and the negative active material layer 24. That is, the reference electrode 31 is disposed in a region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other.
  • the reference electrode 31 may alternatively be disposed on the surface of the positive active material layer 22.
  • the reference electrode 31 can be disposed in the region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other.
  • the reference electrode 31 is disposed extremely close to the surface Y of the negative active material layer 24 where the potential is estimated. Thus, it is possible to improve the accuracy of the estimation of the potential on the surface Y of the negative active material layer 24.
  • Fig. 5 illustrates an electrode assembly 40 provided in an energy storage system according to a third embodiment. As for the configurations not shown, the first embodiment described above can be referred to.
  • a reference electrode 41 is disposed on an end face of a positive electrode plate 16. Specifically, the reference electrode 41 is stacked on the end face (the right end face in Fig. 5) of the positive electrode plate 16 at the side where a positive electrode substrate 21 is not exposed. The reference electrode 41 is stacked on the end face with an insulating member 42 interposed therebetween.
  • the electrode assembly 40 of Fig. 5 is the same as the electrode assembly 15 of Fig. 3 of the first embodiment except the disposed location of the reference electrode 41 and the insulating member 42.
  • the other constituent members are denoted by reference signs identical to the reference signs of the electrode assembly 15 of Fig. 3, and description thereof will be omitted.
  • the reference electrode 41 is disposed on the end face of the positive electrode plate 16.
  • a part other than the disposed location of the reference electrode 41 and the insulating member 42, that is, the material and the like are the same as those of the electrode assembly 15 of the first embodiment. Differently from the form of Fig. 5, the entire face of the reference electrode 41 may be covered with the insulating member 42.
  • the reference electrode 41 is not disposed in an opposed region X between the positive active material layer 22 and the negative active material layer 24. That is, the reference electrode 41 is disposed in a region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other.
  • the reference electrode 41 is disposed on the end face of the positive electrode plate 16 which has a width smaller than the width of the negative electrode plate 17 as illustrated in Fig. 5. Accordingly, it is possible to effectively utilize an empty space and prevent upsizing of the energy storage device caused by the placement of the reference electrode 41. Further, in the positive electrode plate 16 which has a width smaller than the width of the negative electrode plate 17, the positive active material at the end face is in a used state.
  • the reference electrode 41 may alternatively be disposed on an end face of the negative electrode plate 17.
  • Figs. 6 and 7 illustrate an electrode assembly 50 provided in an energy storage system according to a fourth embodiment.
  • the electrode assembly 50 has a stacked structure differently from the electrode assemblies of the first to third embodiments in a wound state.
  • the first embodiment described above can be referred to.
  • the electrode assembly 50 includes a negative electrode plate 51, a separator 52, and a positive electrode plate 53 illustrated in Fig. 7 which are stacked in this order. That is, the separator 52 is disposed between the negative electrode plate 51 and the positive electrode plate 53.
  • the negative electrode plate 51 illustrated in Fig 7(a) includes a negative electrode substrate 54 having a plate-like shape and a negative active material layer 55 which is formed on each face of the negative electrode substrate 54.
  • the negative electrode substrate 54 includes a substrate body 56 having a substantially rectangular shape and a tab portion 57 which is formed on one edge (the left side of the upper end face in Fig. 7(a)) of the substrate body 56.
  • the negative active material layer 55 is formed in a substantially rectangular shape and provided on each face of the substrate body 56.
  • the separator 52 illustrated in Fig. 7(b) has a plate-like shape.
  • the separator 52 includes a separator body 58 having a substantially rectangular shape and a tab portion 59 which is formed on one edge (the left side of the upper end face in Fig. 7(b)) of the separator body 58.
  • the tab portion 57 of the negative electrode plate 51 and the tab portion 59 of the separator 52 are formed at the same position so as to overlap each other in a stacked state.
  • the length (the length in the up-down direction in Fig. 7) of the tab portion 59 of the separator 52 is shorter than the length of the tab portion 57 of the negative electrode plate 51.
  • a reference electrode 60 is disposed on one face of the tab portion of the separator 52.
  • the positive electrode plate 53 illustrated in Fig. 7(c) includes a positive electrode substrate 61 having a plate-like shape and a positive active material layer 62 which is formed on each face of the positive electrode substrate 61.
  • the positive electrode substrate 61 includes a substrate body 63 having a substantially rectangular shape and a tab portion 64 which is formed on one edge (the right side of the upper end face in Fig. 7(c)) of the substrate body 63.
  • the positive active material layer 62 is formed in a substantially rectangular shape and provided on each face of the substrate body 63.
  • the electrode assembly 50 as described above in which the negative electrode plate 51, the separator 52, and the positive electrode plate 53 are stacked in this order has a structure as illustrated in Fig. 6 in which the reference electrode 60 is disposed on the surface of the negative electrode substrate 54 with the separator 52, which is an insulating member, interposed therebetween.
  • the reference electrode 60 is disposed in a region where the positive active material layer 62 and the negative active material layer 55 are not opposed to each other.
  • the energy storage system provided with the electrode assembly 50 of the fourth embodiment similarly to the energy storage system of the first embodiment, it is possible to estimate the potential on the surface of the negative active material layer 55 from the measured potential of the reference electrode 60 and reduce the occurrence of electrodeposition on the surface of the negative active material layer during charging.
  • the tab portion 59 is formed on the porous separator 52, and the reference electrode 60 is disposed on the tab portion 59. Accordingly, the tab portion 59 can maintain wettability by a capillary phenomenon. Thus, even when the tab portion 59 is not entirely immersed in the nonaqueous electrolyte, it is possible to obtain the potential of the reference electrode 60 with respect to the nonaqueous electrolyte. Further, the reference electrode 60 disposed on the tab portion 59 of the separator 52 prevents an increase in the thickness of the electrode assembly caused by the placement of the reference electrode 60.
  • Figs. 8 and 9 illustrate an electrode assembly 70 provided in an energy storage system according to a fifth embodiment.
  • the electrode assembly 70 has a stacked structure similarly to the electrode assembly 50 of the fourth embodiment.
  • the first embodiment described above can be referred to.
  • the electrode assembly 70 includes a positive electrode plate 71, a separator 72, and a negative electrode plate 73 which are stacked in this order. That is, the separator 72 is disposed between the positive electrode plate 71 and the negative electrode plate 73.
  • the positive electrode plate 71 illustrated in Fig. 9(a) includes a positive electrode substrate 74 having a plate-like shape and a positive active material layer 75 which is formed on each face of the positive electrode substrate 74.
  • the positive electrode substrate 74 includes a substrate body 76 having a substantially rectangular shape and a tab portion 77 which is formed on one edge (the left side of the upper end face in Fig. 9(a)) of the substrate body 76.
  • the positive active material layer 75 is formed in a substantially rectangular shape and provided on each face of the substrate body 76.
  • the positive electrode plate 71 has a cut-away part 88 where the positive active material layer 75 is not staked.
  • a reference electrode 80 is disposed in the cut-away part 88.
  • the reference electrode 80 which is covered with an insulating member (not illustrated) is disposed on the surface of the positive electrode substrate 74 in the cut-away part 88. Since the reference electrode 80 is disposed on the surface of the positive electrode substrate 74 with the insulating member (not illustrated) interposed therebetween, the positive electrode substrate 74 and the reference electrode 80 are electrically insulated from each other. Using a porous insulating member ensures the ion (nonaqueous electrolyte) conductivity of the insulating member.
  • the separator 72 illustrated in Fig, 9(b) has a plate-like shape.
  • the separator 72 has a substantially rectangular shape in plan view.
  • the negative electrode plate 73 illustrated in Fig. 9(c) includes a negative electrode substrate 81 having a plate-like shape and a negative active material layer 82 which is formed on each face of the negative electrode substrate 81.
  • the negative electrode substrate 81 includes a substrate body 83 having a substantially rectangular shape and a tab portion 84 which is formed on one edge (the right side of the upper end face in Fig. 9(c)) of the substrate body 83.
  • the reference electrode 80 is disposed in a region where the positive active material layer 75 and the negative active material layer 82 are not opposed to each other.
  • the cut-away part 88 is surrounded by the positive active material layer 75 and thus has a high ion infiltration concentration. Thus, a change in the potential can be detected from the filtration concentration by disposing the reference electrode 80 in the cut-away part 88.
  • the reference electrode 80 disposed in the cut-away part 88 prevents an increase in the thickness of the electrode assembly caused by the placement of the reference electrode 80.
  • the cut-away part 88 is formed in the edge part of the positive active material layer 75 having a substantially rectangular shape, the cut-away part may be formed in another part. For example, a corner part of the positive active material layer 75 having a substantially rectangular shape
  • rectangular shape may be cut away, or a central part thereof may be cut away into a hole shape.
  • Fig. 10 illustrates a part of an energy storage device 91 provided in an energy storage system of a sixth embodiment.
  • a reference electrode is disposed on the surface of a connector which connects a negative electrode plate to an external terminal (a negative electrode terminal).
  • Fig. 10 illustrates an electrode assembly 92, a positive electrode terminal 93, a negative electrode terminal 94 and a reference electrode terminal 95 as external terminals, a positive electrode connector 96, a negative electrode connector 97, and a reference electrode 98 in the energy storage device 91.
  • the energy storage device 91 further includes a case and a nonaqueous electrolyte (not illustrated).
  • the electrode assembly 92 is stored in the case, and the nonaqueous electrolyte is injected into the case.
  • the electrode assembly 92 is the same as the electrode assembly 15 of the first embodiment except that no reference electrode is disposed thereon.
  • the positive electrode terminal 93, the negative electrode terminal 94, and the reference electrode terminal 95 are disposed on the outer face of a lid 99.
  • the positive electrode connector 96 electrically connects a positive electrode substrate 100 of a positive electrode plate on one end of the electrode assembly 92 to the positive electrode terminal 93.
  • the negative electrode connector 97 electrically connects a negative electrode substrate 101 of a negative electrode plate on the other end of the electrode assembly 92 to the negative electrode terminal 94.
  • a plate-like member made of metal can be used as the positive electrode connector 96 and the negative electrode connector 97.
  • the reference electrode 98 is covered with a porous insulating member (not illustrated) and disposed on the surface of the negative electrode connector 97. Since the reference electrode 98 is disposed on the surface of the negative electrode connector 97 with the insulating member (not illustrated) interposed therebetween, the negative electrode connector
  • the porous insulating member ensures the ion (nonaqueous
  • the reference electrode 98 is disposed in contact with the nonaqueous electrolyte. Further, the reference electrode 98 is electrically connected to the reference electrode terminal 95 through a leading wire 102 (reference electrode connector). A peripheral face of the leading wire 102 is covered with an insulating member.
  • the first embodiment described above can be referred to.
  • the connector (negative electrode connector 97) is harder, that is, has a higher stiffness than the positive electrode plate, the negative electrode plate, and the separator.
  • disposing the reference electrode 98 on the surface of the connector results in easy placement of the reference electrode 98.
  • the connector has little change with passage of time as compared to the positive electrode plate, the negative electrode plate, and the separator.
  • the present invention is not limited to the above embodiments and can be carried out in various modes with modifications and improvements in addition to the above modes.
  • the energy storage system may be a combination of the above embodiments.
  • the energy storage device is mainly a nonaqueous electrolyte secondary battery, the energy storage device may be another energy storage device.
  • the energy storage device include capacitors (an electric double layer capacitor and a lithium ion capacitor).
  • the configuration of the energy storage device in the energy storage system according to the present invention is not particularly limited to any configuration.
  • Examples of the configuration of the energy storage device include a cylindrical battery, a prismatic battery (rectangular battery), and a flat-type battery.
  • the present invention may be implemented as an energy storage system provided with an energy storage apparatus including a plurality of the above energy storage devices.
  • Fig. 11 illustrates an embodiment of the energy storage apparatus.
  • an energy storage apparatus 110 includes a plurality of energy storage units 120.
  • Each of the energy storage units 120 includes a plurality of energy storage devices 130.
  • the present invention can be preferably used as an energy storage system and a charge method in an automotive power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV).
  • EV electric vehicle
  • HEV hybrid electric vehicle
  • PHEV plug-in hybrid electric vehicle

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Abstract

To provide an energy storage system and a charge method that are capable of reducing the occurrence of electrodeposition on the surface of a negative active material layer during charging. One embodiment of the present invention provides an energy storage system including: an energy storage device, the energy storage device including a negative electrode plate including a negative active material layer, a nonaqueous electrolyte, and a reference electrode disposed in contact with the nonaqueous electrolyte; and an arithmetic unit that estimates a potential on a surface of the negative active material layer from a measured potential of the reference electrode. Another embodiment of the present invention provides a charge method including stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer using the energy storage system.

Description

DESCRIPTION
TITLE OF THE INVENTION: ENERGY STORAGE SYSTEM AND CHARGE METHOD
TECHNICAL FIELD
[0001]
The present invention relates to an energy storage system and a charge method.
BACKGROUND ART
[0002]
Nonaqueous electrolyte secondary batteries typified by a lithium ion secondary battery are frequently used in personal computers, electronic devices such as a communication terminal, and automobiles. A nonaqueous electrolyte secondary battery typically includes a pair of electrodes which are electrically separated by a separator and a nonaqueous electrolyte
interposed between the electrodes. Such a nonaqueous electrolyte secondary battery is configured to perform charge and discharge by transferring ions between the electrodes. Further, capacitors such as a lithium ion capacitor and an electric double layer capacitor have also become widespread as energy storage devices other than the nonaqueous electrolyte secondary battery.
[0003]
A reference electrode is required to accurately measure a potential of an electrode in these energy storage devices. In a lithium ion secondary battery described in Patent Document 1, a reference electrode for a negative electrode is disposed between the negative electrode and a separator. In a battery state monitoring apparatus described in Patent Document 2, a reference electrode is disposed on a negative electrode plate with an insulating member interposed therebetween.
PRIOR ART DOCUMENTS
PATENT DOCUMENTS
[0004]
Patent Document l: JP-A-2016-143452
Patent Document 2- JP-A-2013- 118090
SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION
[0005]
However, there is a limit in accurately measuring the potential on the surface of a negative active material layer in a conventional nonaqueous electrolyte energy storage apparatus provided with a reference electrode. In addition, when the potential on the surface of the negative active material layer becomes a predetermined value or less during charging,
electrodeposition of metal (typically, lithium) dissolved in a nonaqueous solvent occurs, which accelerates the deterioration of the energy storage apparatus. The electrodeposition is particularly likely to occur when charging is performed with a large current. Thus, in order to perform charging with high speed while reducing the occurrence of electrodeposition, a technique capable of more accurately grasping the potential on the surface of the negative active material layer is required.
[0006] The present invention has been made in view of the above
circumstances, and an object thereof is to provide an energy storage system and a charge method that are capable of reducing the occurrence of electrodeposition on the surface of a negative active material layer during charging.
MEANS FOR SOLVING THE PROBLEMS
[0007]
One embodiment of the present invention which has been made for solving the above problems provides an energy storage system including: an energy storage device, the energy storage device including a negative electrode plate including a negative active material layer, a nonaqueous electrolyte, and a reference electrode disposed in contact with the
nonaqueous electrolyte! and an arithmetic unit that estimates a potential on a surface of the negative active material layer from a measured potential of the reference electrode.
[0008]
Another embodiment of the present invention provides a charge method including stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer using the energy storage system.
ADVANTAGES OF THE INVENTION
[0009]
According to the embodiments, it is possible to provide an energy storage system and a charge method that are capable of reducing the occurrence of electrodeposition on the surface of a negative active material layer during charging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
Fig. 1 is a schematic view of an energy storage system according to a first embodiment of the present invention.
Fig. 2 is a schematic perspective view of an electrode assembly of the energy storage system of Fig. 1.
Fig. 3 is a partial sectional view of the electrode assembly of Fig. 2 taken along line A- A.
Fig. 4 is a partial sectional view of an electrode assembly of an energy storage system according to a second embodiment of the present invention.
Fig. 5 is a partial sectional view of an electrode assembly of an energy storage system according to a third embodiment of the present invention.
Fig. 6 is a plan view of an electrode assembly of an energy storage system according to a fourth embodiment of the present invention.
Fig, 7(a) is a plan view of a negative electrode plate of the electrode assembly of Fig. 6, Fig. 7(b) is a plan view of a separator and the like of the electrode assembly of Fig. 6, and Fig. 7(c) is a plan view of a positive electrode plate of the electrode assembly of Fig. 6.
Fig. 8 is a plan view of an electrode assembly of an energy storage system according to a fifth embodiment of the present invention.
Fig, 9(a) is a plan view of a positive electrode plate and the like of the electrode assembly of Fig. 8, Fig. 9(b) is a plan view of a separator of the electrode assembly of Fig. 8, and Fig. 9(c) is a plan view of a negative electrode plate of the electrode assembly of Fig. 8. Fig. 10 is a perspective view schematically illustrating a part of an energy storage device provided in an energy storage system according to a sixth embodiment of the present invention.
Fig. 11 is a schematic view of an energy storage apparatus provided in an energy storage system according to an embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0011]
An energy storage system according to an embodiment of the present invention includes: an energy storage device, the energy storage device including a negative electrode plate including a negative active material layer, a nonaqueous electrolyte, and a reference electrode disposed in contact with the nonaqueous electrolyte! and an arithmetic unit that estimates a potential on a surface of the negative active material layer from a measured potential of the reference electrode.
[0012]
The energy storage system includes the arithmetic unit that estimates the potential on the surface of the negative active material layer from the measured potential of the reference electrode. Thus, it is possible to obtain the potential on the surface of the negative active material with high accuracy. Thus, according to the energy storage system, it is possible to grasp the potential on the surface of the negative active material layer with high accuracy during charging, and stop the charging and control a charge current according to the potential. As a result, it is possible to reduce the occurrence of electrodeposition of lithium or the like. The "lithium or the like" indicates a metal that constitutes an electrolyte salt dissolved in the nonaqueous electrolyte. The "lithium or the like" is typically lithium, but may be another metal.
[0013]
The energy storage device may include a positive electrode plate including a positive active material layer, and the reference electrode may be disposed in a region where the positive active material layer and the negative active material layer are not opposed to each other. When the reference electrode is present between the positive active material layer and the negative active material layer, the flow of ions between the active material layers is blocked in the part where the reference electrode is present. Thus, the flow of ions is concentrated on the negative active material layer around the reference electrode, and electrodeposition is likely to occur in this part. Thus, it is possible to suppress the uneven distribution of the flow of ions and further reduce the occurrence of electrodeposition by disposing the reference electrode in the region where the positive active material layer and the negative active material layer are not opposed to each other.
[0014]
The positive electrode plate may include a positive electrode substrate, the positive active material layer may be formed on a part of the positive electrode substrate, the negative electrode plate may include a negative electrode substrate, the negative active material layer may be formed on a part of the negative electrode substrate, and the reference electrode may be disposed on a surface of the positive electrode substrate or a surface of the negative electrode substrate.
[0015]
The reference electrode may be disposed on the surface of the negative active material layer.
[0016]
The energy storage device may include a separator disposed between the positive electrode plate and the negative electrode plate, and the reference electrode may be disposed on a surface of the separator.
[0017]
The reference electrode may be disposed on an end face of the positive electrode plate or an end face of the negative electrode plate.
[0018]
As described above, the reference electrode can be disposed on one of the locations^ the surface of the positive electrode substrate! the surface of the negative electrode substrate! the surface of the positive active material layer! the surface of the negative active material layer! the surface of the separator! the end face of the positive electrode plate! and the end face of the negative electrode plate. A space that has a small influence on a
charge- discharge reaction and is empty in view of the shape of the positive electrode plate, the negative electrode plate, or the energy storage device itself can be utilized as the disposed location of the reference electrode.
Accordingly, it is possible to improve the accuracy of the estimation of the potential on the surface of the negative active material layer while preventing upsizing of the energy storage device.
[0019] The positive electrode plate may have a cut-away part where the positive active material layer is not formed, and the reference electrode may be disposed in the cut-away part. The cut-away part is surrounded by the positive active material layer and thus has a high ion infiltration
concentration. A change in the potential can be detected from the filtration concentration by disposing the reference electrode in the cut-away part. In addition, it is possible to obtain the potential on the surface of the negative active material layer which is opposed to the positive active material layer from the potential of the cut-away part using a numerical analytical model which reproduces an identical shape. This makes it possible to estimate the surface potential of the negative active material layer with a higher accuracy and sufficiently reduce the occurrence of electrodeposition.
[0020]
The reference electrode may be disposed on a surface of a connector that connects the negative electrode plate to an external terminal. The surface of the connector is also one of spaces that have a small influence on the charge- discharge reaction and are empty. Thus, it is possible to improve the accuracy of the estimation of the potential while preventing upsizing of the energy storage device by disposing the reference electrode on the surface of the connector.
[0021]
The energy storage system may further include a control unit that stops charging or controls a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer. The energy storage system further provided with the control unit makes it possible to stop charging or control a charge current according to the obtained potential on the surface of the negative active material layer.
Thus, it is possible to more effectively reduce the occurrence of
electrodeposition on the surface of the negative active material layer during charging.
[0022]
A charge method according to one embodiment of the present invention includes stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer using the energy storage system. The charge method is capable of estimating the potential on the surface of the negative active material layer during charging with high accuracy. Thus, it is possible to reduce the occurrence of electrodeposition on the surface of the negative active material layer by, for example, controlling a charge current.
[0023]
Hereinbelow, an energy storage system and a charge method using the same according to an embodiment of the present invention will be described in detail.
[0024]
<Energy Storage System: First Embodiment>
An energy storage system 10 illustrated in Fig. 1 according to a first embodiment of the present invention includes an energy storage device 11 and a battery charger 12. The energy storage device 11 includes, as external terminals, a positive electrode terminal 11a, a negative electrode terminal lib, and a reference electrode terminal 11c. The battery charger 12 is connected to these external terminals of the energy storage device 11.
[0025]
(Energy Storage Device)
The energy storage device 11 includes a positive electrode plate, a negative electrode plate, and a nonaqueous electrolyte. Hereinbelow, a nonaqueous electrolyte secondary battery will be described as an example of the energy storage device 11. The positive electrode plate and the negative electrode plate are typically alternately layered by stacking or winding with a separator interposed therebetween to form an electrode assembly. Figs. 2 and 3 illustrate the structure of a wound-type electrode assembly 15 in the first embodiment.
[0026]
Fig. 2 schematically illustrates the electrode assembly 15, which is a band-shaped layered product, in a wound state. As illustrated in Fig. 3, the electrode assembly 15 has a structure in which a positive electrode plate 16, a negative electrode plate 17, and two separators 18, 19 are stacked.
Specifically, the positive electrode plate 16, the first separator 18, the negative electrode plate 17, and the second separator 19, each of which has a band shape, are stacked in this order. The electrode assembly 15 further includes a reference electrode 20 which is disposed on the negative electrode plate 17. Fig. 3 schematically illustrates the elements (the positive electrode plate 16, the first separator 18, the negative electrode plate 17, and the second separator 19) of the electrode assembly 15 in a separated manner. However, adjacent ones of the elements are typically in contact with each other. [0027]
The electrode assembly 15 in a wound state in Fig. 2 is stored in a case, and the case is filled with the nonaqueous electrolyte. Fig. 2 illustrates the electrode assembly 15 whose tip part is not wound for the purpose of description. However, the electrode assembly 15 stored inside the case is wound up to the tip part thereof (refer to an electrode assembly 92 of Fig. 10). The positive electrode plate 16, the negative electrode plate 17, the separators 18, 19, and the reference electrode 20 which constitute the electrode assembly 15 of the energy storage device 11 are in contact with the nonaqueous electrolyte.
[0028]
One end part 15a in the axial direction of the electrode assembly 15 of Fig. 2 is connected to the positive electrode terminal 11a of Fig. 1 through a connector (not illustrated). The other end part 15b in the axial direction of the electrode assembly 15 of Fig. 2 is connected to the negative electrode terminal lib of Fig. 1 through a connector (not illustrated). A known aluminum or resin case, which is typically used as a case for secondary battery, can be used as the case described above. Hereinbelow, the electrode assembly 15 will be described in detail with reference to, mainly, Fig. 3.
[0029]
The positive electrode plate 16 includes a positive electrode substrate 21 and a positive active material layer 22 which is formed on a part of each face of the positive electrode substrate 21. The positive electrode plate 16 may further include an intermediate layer (not illustrated) which is formed between the positive electrode substrate 21 and the positive active material layer 22.
[0030]
The positive electrode substrate 21 has a band shape and has conductivity. A metal such as aluminum, titanium, tantalum, or stainless steel, or an alloy thereof is used as a material of the positive electrode substrate 21. A metal foil such as an aluminum foil can be preferably used as the positive electrode substrate 21.
[0031]
The positive active material layer 22 is formed on a part of the positive electrode substrate 21. Specifically, the positive active material layer 22 is formed in a longitudinal direction of the positive electrode substrate 21 except both faces of one side end (the left side end in Fig. 3) thereof. That is, the positive electrode substrate 21 is exposed in the one end part 15a (refer to Fig. 2) of the electrode assembly 15.
[0032]
The positive active material layer 22 is formed of a so-called positive electrode mixture containing a positive active material. The positive electrode mixture which forms the positive active material layer 22 contains an optional component such as a conductive agent, a binder (binding agent), a thickener, or a filler as needed.
[0033]
Examples of the positive active material include composite oxides represented by LixMOy (M represents at least one kind of transition metal) (LixCo02, LixNi02, LixMn03, LixNiaCo(i-a)02, and LixNiaMnpCo(i-a-p)02 each having a layered orNaFe02 crystal structure and LixMn204 and LixNiaMn(2-a)04 each having a spinel crystal structure) and polyanion compounds represented by LiwMex(XOy)z (Me represents at least one kind of transition metal and X represents, for example, P, Si, B, V) (LiFeP04, LiMnP04, LiNiP04, LiCoP04, Li3V2(P04)3, Li2MnSi04, and Li2CoP04F). An element or polyanion in these compounds may be partially substituted with another element or anion. In the positive active material layer, one kind of these compounds may be solely used, or two or more kinds may be mixed.
[0034]
The negative electrode plate 17 includes a negative electrode substrate 23 and a negative active material layer 24 which is formed on a part of each face of the negative electrode substrate 23. The negative electrode plate 17 may further include an intermediate layer (not illustrated) which is formed between the negative electrode substrate 23 and the negative active material layer 24.
[0035]
The negative electrode substrate 23 may have a structure similar to that of the positive electrode substrate 21. A metal such as copper, nickel, stainless steel, or nickel-plated steel, or an alloy thereof is used as a material of the negative electrode substrate 23, and copper or a copper alloy is preferred. That is, a copper foil is preferably used as the negative electrode substrate 23.
[0036]
The negative active material layer 24 is formed on a part of the negative electrode substrate 23. Specifically, the negative active material layer 24 is formed in a longitudinal direction of the negative electrode substrate 23 except both faces of one side end (the right side end in Fig. 3) thereof. That is, the negative electrode substrate 23 is exposed in the other end part 15b (refer to Fig. 2) of the electrode assembly 15.
[0037]
The negative active material layer 24 is formed of a so-called negative electrode mixture containing a negative active material. The negative electrode mixture which forms the negative active material layer 24 contains an optional component such as a conductive agent, a binder
(binding agent), a thickener, or a filler as needed.
[0038]
Examples of the negative active material include metals or
semimetals such as Si and Sn! metal oxides or semimetal oxides such as a Si oxide and a Sn oxide! polyphosphoric acid compounds! and carbon materials such as graphite and amorphous carbon (easily graphitizable carbon or hardly graphitizable carbon).
[0039]
Each of the separators 18, 19 has an insulation property and porosity. For example, a woven fabric, a nonwoven fabric, or a porous resin film is used as a material of the separators 18, 19. Among these materials, a porous resin film is preferred in view of strength, and a nonwoven fabric is preferred in view of the retention of the nonaqueous electrolyte. As a main component of the separators 18, 19, for example, polyolefin such as polyethylene or polypropylene is preferred in view of strength, and polyimide or aramid is preferred in view of resistance to oxidative decomposition.
Further, these resins may be combined. Further, a separator that includes a substrate made of a resin and an inorganic layer which is stacked on the surface of the substrate may be used.
[0040]
The reference electrode 20 is disposed on the surface of the negative electrode substrate 23. Specifically, the reference electrode 20 is stacked on the exposed part of the negative electrode substrate 23 at the end part of the negative electrode plate 17 with an insulating member 25 interposed therebetween.
[0041]
Metal lithium or another material that is known as a reference electrode can be used as the reference electrode 20. The shape of the reference electrode 20 is not particularly limited and may be a circular shape or a rectangular shape in plan view. The shape of the reference electrode 20 may be, for example, a plate-like shape or a rod-like shape. In this case, a metal foil or a metal wire can be used.
[0042]
Further, the size of the reference electrode 20 is not particularly limited. For example, the total thickness of the reference electrode 20 and the insulating member 25 which covers the reference electrode 20 may be equal to or less than the thickness of the negative active material layer 24. This makes it possible to prevent an increase in the thickness of a location where the reference electrode 20 is disposed in the electrode assembly 15.
[0043]
The reference electrode 20 is electrically connected to the reference electrode terminal 11c (refer to Fig. l), which is an external terminal, through a connector (e.g., a leading wire having an insulated surface, not illustrated).
[0044]
The reference electrode 20 is not disposed in an opposed region X between the positive active material layer 22 and the negative active material layer 24. That is, the reference electrode 20 is disposed in a region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other.
[0045]
The insulating member 25 covers the reference electrode 20. The insulating member 25 has an insulation property and porosity. That is, the insulating member 25 transmits the nonaqueous electrolyte (ion), but insulates electricity. When the reference electrode 20 is disposed with the insulating member 25 interposed, it is possible to measure an accurate potential in the disposed location. A part of the reference electrode 20 may be exposed without being covered with the insulating member 25 as long as an electrically insulated state between the negative electrode substrate 23 and the reference electrode 20 can be ensured. When the surface of the reference electrode 20 is exposed, the insulating member 25 disposed between the reference electrode 20 and the negative electrode substrate 23 may be a nonporous member.
[0046]
The insulating member 25 can be formed of, for example, an insulating particle and a binder. The insulating member 25 may contain another component other than the insulating particle and the binder. [0047]
The insulating particle may either be an inorganic particle or an organic particle. However, an inorganic particle is preferred in view of resistance to heat. Examples of the inorganic particle include inorganic oxides such as silica, alumina, titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide and inorganic nitrides such as silicon nitride, titanium nitride, and boron nitride. In addition, examples of the inorganic particle include silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin cray, kaolinite, boehmite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, aluminosilicate, calcium silicate, magnesium silicate, diatom earth, silica sand, and glass.
[0048]
A binder that is capable of fixing the insulating particle and electrochemically stable in a used range is typically used as the binder described above. Examples of the binder include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF)), polyethylene, polypropylene, and polyimide! elastomers such as ethylene-propylene- diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluoro rubber! and polysaccharide polymers.
[0049]
Alternatively, the insulating member 25 may be formed of a woven fabric, a nonwoven fabric, or a porous resin film similarly to the separators 18, 19. [0050]
A known nonaqueous electrolyte which is typically used in a nonaqueous electrolyte secondary battery is used as the nonaqueous electrolyte described above. A nonaqueous electrolyte that contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent can be used as the nonaqueous electrolyte described above.
[0051]
Examples of the nonaqueous solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).
[0052]
Examples of the electrolyte salt include lithium salt, sodium salt, potassium salt, magnesium salt, and onium salt. Among these salts, lithium salt is preferred. Examples of the lithium salt include inorganic lithium salts such as LiPF6, LiP02F2, LiBF4, LiC104, and LiN(S02F)2, and lithium salts having a fluorohydrocarbon group such as L1SO3CF3,
LiN(S02CF3)2, LiN(S02C2F5)2, LiN(S02CF3) (S02C4F9), LiC(S02CF3)3, and LiC(S02C2F5)3.
[0053]
Further, an ordinary temperature molten salt, an ion liquid, or a polymer solid electrolyte can also be used as the nonaqueous electrolyte.
[0054]
(Battery Charger)
The battery charger 12 of Fig. 1 includes an arithmetic unit 13 and a control unit 14. The battery charger 12 further includes a voltmeter and a charge circuit (not illustrated).
[0055]
The voltmeter measures a potential of the reference electrode terminal 11c which is electrically connected to the reference electrode 20. The voltmeter may be configured to measure a potential difference (voltage) between any two of the positive electrode terminal 11a (positive electrode plate 16), the negative electrode terminal lib (negative electrode plate 17), and the reference electrode terminal 11c (reference electrode 20).
[0056]
The arithmetic unit 13 estimates a potential on a surface Y (refer to Fig. 3) of the negative active material layer 24 of the energy storage device 11 from the measured potential of the reference electrode 20. The estimation of the surface potential can be performed on the basis of a known model such as the Newman model. When the estimation is performed on the basis of a predetermined model, the estimation can be performed on the basis of parameters such as the electric conductivity and the thickness of the negative electrode substrate 23, the electric conductivity, the thickness, the active material diameter, the porosity, the diffusion coefficient, and the reaction speed constant of the negative active material layer 24, the diffusion coefficient, the electrolyte salt concentration, and the ion conductivity of the nonaqueous electrolyte, and the positional relationship (e.g., distance) between the reference electrode 20 and the negative active material layer 24. These parameters are appropriately set on the basis of the disposed location of the reference electrode. The estimation of the surface potential by the arithmetic unit 13 may be performed on the basis of database on which measured values of the potential of the reference electrode 20 and the potential on the surface Y of the negative active material layer 24
corresponding to the potential of the reference electrode 20 in the energy storage device 11 are accumulated. Further, calculated values based on any model may be databased.
[0057]
The battery charger 12 convers power from a power source to power suitable for charging in the charge circuit in accordance with control of the control unit 14 and outputs the converted power between the positive electrode terminal 11a and the negative electrode terminal lib. Accordingly, the energy storage device 11 is charged with electricity. Further, the control unit 14 stops the charging or controls a charge current on the basis of an estimated value of the potential on the surface Y of the negative active material layer 24 estimated by the arithmetic unit 13.
[0058]
The arithmetic unit 13 and the control unit 14 may include a computer and a computer program. The arithmetic unit 13 and the control unit 14 may include a processor that is partially or entirely composed of a semiconductor chip. The arithmetic unit 13 and the control unit 14 may be separate components, may be an integrated component, or may be integrated with another component of the battery charger 12.
[0059]
(Charge Method using Energy Storage System and Advantages of Energy Storage System) A charge method according to an embodiment of the present invention includes stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface Y of the negative active material layer 24 using the energy storage system 10. The charge method may further include measuring a potential of the reference electrode 20 and estimating the potential on the surface Y of the negative active material layer 24 on the basis of the measured potential of the reference electrode 20.
[0060]
The energy storage system 10 is capable of estimating the potential on the surface Y of the negative active material layer 24 from the measured potential of the reference electrode 20 by the arithmetic unit 13. Thus, it is possible to obtain the potential on the surface Y of the negative active material layer 24 with high accuracy. That is, according to the energy storage system 10, it is possible to grasp the potential on the surface Y of the negative active material layer 24 with high accuracy during charging, and stop the charging or control a charge current in accordance with the potential by the control unit 14. As a result, it is possible to reduce the occurrence of electrodeposition of lithium or the like. For example, when the electrolyte salt contained in the nonaqueous electrolyte is a lithium salt, the charge current can be controlled so that the estimated potential on the surface Y of the negative active material layer 24 does not become 0 V (vs. Li/Li+) or less.
[0061]
In the energy storage system 10, the reference electrode 20 is disposed in the region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other. Thus, it is possible to suppress the uneven distribution of the flow of ions (nonaqueous electrolyte) and further reduce the occurrence of electrodeposition.
[0062]
Further, in the form illustrated in Fig. 3, the reference electrode 20 is disposed on the surface of the negative electrode substrate 23 in a
non-opposed region which is not opposed to the separator 18. An electrode assembly which includes a positive electrode plate, a negative electrode plate, and a separator is wound in such a manner that a substrate part of each of the positive electrode plate and the negative electrode plate which is not opposed to the separator, that is, the tip part is exposed, and the exposed substrate parts are tied into a bundle and joined to a connector (refer to Fig. 10). That is, in the structure in which the electrode assembly and the connector are joined in this manner, the non-opposed region, which is not opposed to the separator 18, in the negative electrode substrate 23 is in an exposed state. Thus, also after the connector is joined to the electrode assembly, the reference electrode 20 can be easily disposed in such an exposed part of the substrate (negative electrode substrate 23). That is, the structure in which the reference electrode is disposed on the surface of the substrate (the positive electrode substrate or the negative electrode
substrate) can improve an attachment operability.
[0063]
Alternatively, the reference electrode 20 may be disposed on the surface of the negative electrode substrate 23 in a region opposed to the separator 18. In this case, the reference electrode 20 can be disposed at a position closer to the negative active material layer 24. Thus, it is possible to estimate the potential on the surface of the negative active material layer 24 with high accuracy. In this case, it is possible to prevent an increase in the thickness of the location where the reference electrode 20 is disposed in the electrode assembly 15 by, for example, setting the total thickness of the reference electrode 20 and the insulating member 25 which covers the reference electrode 20 to equal to or less than the thickness of the negative active material layer 24.
[0064]
Although the reference electrode 20 is disposed on the surface of the negative electrode substrate 23 in the energy storage system 10 described above, the reference electrode 20 may alternatively be disposed on the surface of the positive electrode substrate 21. Also in this case, it is possible to estimate the surface potential of the negative active material layer 24 from the potential of the reference electrode 20 by the arithmetic unit 13. However, the reference electrode 20 disposed on the surface of the negative electrode substrate 23 which is close to the negative active material layer 24 as illustrated in Fig. 3 improves the accuracy of the estimation of the surface potential of the negative active material layer 24.
[0065]
<Second Embodiment>
Fig. 4 illustrates an electrode assembly 30 provided in an energy storage system according to a second embodiment. As for the
configurations not shown, the first embodiment described above can be referred to.
[0066]
In the electrode assembly 30 of Fig. 4, a reference electrode 31 is disposed on the surface of a negative active material layer 24. Specifically, the reference electrode 31 is stacked on the surface of an end part of the negative active material layer 24 with an insulating member 32 interposed therebetween. The electrode assembly 30 of Fig. 4 is the same as the electrode assembly 15 of Fig. 3 of the first embodiment except the disposed location of the reference electrode 31 and the insulating member 32. Thus, the other constituent members are denoted by reference signs identical to the reference signs of the electrode assembly 15 of Fig. 3, and description thereof will be omitted.
[0067]
In the electrode assembly 30 of the second embodiment, the reference electrode 31 is disposed on the surface of the negative active material layer 24. A part other than the disposed location of the reference electrode 31 and the insulating member 32, that is, the material and the like are the same as those of the electrode assembly 15 of the first embodiment. Also in the electrode assembly of the second embodiment, the positive electrode plate, the negative electrode plate, and the reference electrode are electrically connected to corresponding external terminals through connectors similarly to the first embodiment (the same applies to other embodiments described below). The reference electrode 31 is not disposed in an opposed region X between the positive active material layer 22 and the negative active material layer 24. That is, the reference electrode 31 is disposed in a region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other.
[0068]
Also in the energy storage system provided with the electrode assembly 30 of the second embodiment, similarly to the energy storage system of the first embodiment, it is possible to estimate the potential on the surface Y of the negative active material layer 24 from the measured potential of the reference electrode 31 and reduce the occurrence of electrodeposition on the surface of the negative active material layer during charging. In the electrode assembly 30 of the second embodiment, the reference electrode 31 may alternatively be disposed on the surface of the positive active material layer 22. However, when the disposed location is the surface of the negative active material layer 24 as illustrated in Fig. 4, the reference electrode 31 can be disposed in the region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other. Further, when the disposed location is the surface of the negative active material layer 24, the reference electrode 31 is disposed extremely close to the surface Y of the negative active material layer 24 where the potential is estimated. Thus, it is possible to improve the accuracy of the estimation of the potential on the surface Y of the negative active material layer 24.
[0069]
<Third Embodiment>
Fig. 5 illustrates an electrode assembly 40 provided in an energy storage system according to a third embodiment. As for the configurations not shown, the first embodiment described above can be referred to.
[0070]
In the electrode assembly 40 of Fig. 5, a reference electrode 41 is disposed on an end face of a positive electrode plate 16. Specifically, the reference electrode 41 is stacked on the end face (the right end face in Fig. 5) of the positive electrode plate 16 at the side where a positive electrode substrate 21 is not exposed. The reference electrode 41 is stacked on the end face with an insulating member 42 interposed therebetween. The electrode assembly 40 of Fig. 5 is the same as the electrode assembly 15 of Fig. 3 of the first embodiment except the disposed location of the reference electrode 41 and the insulating member 42. Thus, the other constituent members are denoted by reference signs identical to the reference signs of the electrode assembly 15 of Fig. 3, and description thereof will be omitted.
[0071]
In the electrode assembly 40 of the third embodiment, the reference electrode 41 is disposed on the end face of the positive electrode plate 16. A part other than the disposed location of the reference electrode 41 and the insulating member 42, that is, the material and the like are the same as those of the electrode assembly 15 of the first embodiment. Differently from the form of Fig. 5, the entire face of the reference electrode 41 may be covered with the insulating member 42. The reference electrode 41 is not disposed in an opposed region X between the positive active material layer 22 and the negative active material layer 24. That is, the reference electrode 41 is disposed in a region where the positive active material layer 22 and the negative active material layer 24 are not opposed to each other. [0072]
Also in the energy storage system provided with the electrode assembly 40 of the third embodiment, similarly to the energy storage system of the first embodiment, it is possible to estimate the potential on the surface Y of the negative active material layer 24 from the measured potential of the reference electrode 41 and reduce the occurrence of electrodeposition on the surface of the negative active material layer during charging. The reference electrode 41 is disposed on the end face of the positive electrode plate 16 which has a width smaller than the width of the negative electrode plate 17 as illustrated in Fig. 5. Accordingly, it is possible to effectively utilize an empty space and prevent upsizing of the energy storage device caused by the placement of the reference electrode 41. Further, in the positive electrode plate 16 which has a width smaller than the width of the negative electrode plate 17, the positive active material at the end face is in a used state. Thus, it is possible to measure a cross section average potential with high accuracy. As a result, it is possible to improve the accuracy of the estimation of the potential on the surface Y of the negative active material layer 24. In the electrode assembly 40 of the third embodiment, the reference electrode 41 may alternatively be disposed on an end face of the negative electrode plate 17.
[0073]
<Fourth Embodiment>
Figs. 6 and 7 illustrate an electrode assembly 50 provided in an energy storage system according to a fourth embodiment. The electrode assembly 50 has a stacked structure differently from the electrode assemblies of the first to third embodiments in a wound state. As for the configurations not shown, the first embodiment described above can be referred to.
[0074]
The electrode assembly 50 includes a negative electrode plate 51, a separator 52, and a positive electrode plate 53 illustrated in Fig. 7 which are stacked in this order. That is, the separator 52 is disposed between the negative electrode plate 51 and the positive electrode plate 53.
[0075]
The negative electrode plate 51 illustrated in Fig 7(a) includes a negative electrode substrate 54 having a plate-like shape and a negative active material layer 55 which is formed on each face of the negative electrode substrate 54. The negative electrode substrate 54 includes a substrate body 56 having a substantially rectangular shape and a tab portion 57 which is formed on one edge (the left side of the upper end face in Fig. 7(a)) of the substrate body 56. The negative active material layer 55 is formed in a substantially rectangular shape and provided on each face of the substrate body 56.
[0076]
The separator 52 illustrated in Fig. 7(b) has a plate-like shape. The separator 52 includes a separator body 58 having a substantially rectangular shape and a tab portion 59 which is formed on one edge (the left side of the upper end face in Fig. 7(b)) of the separator body 58. The tab portion 57 of the negative electrode plate 51 and the tab portion 59 of the separator 52 are formed at the same position so as to overlap each other in a stacked state. The length (the length in the up-down direction in Fig. 7) of the tab portion 59 of the separator 52 is shorter than the length of the tab portion 57 of the negative electrode plate 51. A reference electrode 60 is disposed on one face of the tab portion of the separator 52.
[0077]
The positive electrode plate 53 illustrated in Fig. 7(c) includes a positive electrode substrate 61 having a plate-like shape and a positive active material layer 62 which is formed on each face of the positive electrode substrate 61. The positive electrode substrate 61 includes a substrate body 63 having a substantially rectangular shape and a tab portion 64 which is formed on one edge (the right side of the upper end face in Fig. 7(c)) of the substrate body 63. The positive active material layer 62 is formed in a substantially rectangular shape and provided on each face of the substrate body 63.
[0078]
The electrode assembly 50 as described above in which the negative electrode plate 51, the separator 52, and the positive electrode plate 53 are stacked in this order has a structure as illustrated in Fig. 6 in which the reference electrode 60 is disposed on the surface of the negative electrode substrate 54 with the separator 52, which is an insulating member, interposed therebetween. The reference electrode 60 is disposed in a region where the positive active material layer 62 and the negative active material layer 55 are not opposed to each other.
[0079]
Also in the energy storage system provided with the electrode assembly 50 of the fourth embodiment, similarly to the energy storage system of the first embodiment, it is possible to estimate the potential on the surface of the negative active material layer 55 from the measured potential of the reference electrode 60 and reduce the occurrence of electrodeposition on the surface of the negative active material layer during charging.
Further, the tab portion 59 is formed on the porous separator 52, and the reference electrode 60 is disposed on the tab portion 59. Accordingly, the tab portion 59 can maintain wettability by a capillary phenomenon. Thus, even when the tab portion 59 is not entirely immersed in the nonaqueous electrolyte, it is possible to obtain the potential of the reference electrode 60 with respect to the nonaqueous electrolyte. Further, the reference electrode 60 disposed on the tab portion 59 of the separator 52 prevents an increase in the thickness of the electrode assembly caused by the placement of the reference electrode 60.
[0080]
<Fifth Embodiment
Figs. 8 and 9 illustrate an electrode assembly 70 provided in an energy storage system according to a fifth embodiment. The electrode assembly 70 has a stacked structure similarly to the electrode assembly 50 of the fourth embodiment. As for the configurations not shown, the first embodiment described above can be referred to.
[0081]
The electrode assembly 70 includes a positive electrode plate 71, a separator 72, and a negative electrode plate 73 which are stacked in this order. That is, the separator 72 is disposed between the positive electrode plate 71 and the negative electrode plate 73.
[0082]
The positive electrode plate 71 illustrated in Fig. 9(a) includes a positive electrode substrate 74 having a plate-like shape and a positive active material layer 75 which is formed on each face of the positive electrode substrate 74. The positive electrode substrate 74 includes a substrate body 76 having a substantially rectangular shape and a tab portion 77 which is formed on one edge (the left side of the upper end face in Fig. 9(a)) of the substrate body 76. The positive active material layer 75 is formed in a substantially rectangular shape and provided on each face of the substrate body 76. The positive electrode plate 71 has a cut-away part 88 where the positive active material layer 75 is not staked.
[0083]
A reference electrode 80 is disposed in the cut-away part 88.
Specifically, the reference electrode 80 which is covered with an insulating member (not illustrated) is disposed on the surface of the positive electrode substrate 74 in the cut-away part 88. Since the reference electrode 80 is disposed on the surface of the positive electrode substrate 74 with the insulating member (not illustrated) interposed therebetween, the positive electrode substrate 74 and the reference electrode 80 are electrically insulated from each other. Using a porous insulating member ensures the ion (nonaqueous electrolyte) conductivity of the insulating member.
[0084]
The separator 72 illustrated in Fig, 9(b) has a plate-like shape. The separator 72 has a substantially rectangular shape in plan view. [0085]
The negative electrode plate 73 illustrated in Fig. 9(c) includes a negative electrode substrate 81 having a plate-like shape and a negative active material layer 82 which is formed on each face of the negative electrode substrate 81. The negative electrode substrate 81 includes a substrate body 83 having a substantially rectangular shape and a tab portion 84 which is formed on one edge (the right side of the upper end face in Fig. 9(c)) of the substrate body 83.
[0086]
In the electrode assembly 70 as described above in which the positive electrode plate 71, the separator 72, and the negative electrode plate 73 are stacked in this order, the reference electrode 80 is disposed in a region where the positive active material layer 75 and the negative active material layer 82 are not opposed to each other.
[0087]
Also in the energy storage system provided with the electrode assembly 70 of the fifth embodiment, similarly to the energy storage system of the first embodiment, it is possible to estimate the potential on the surface of the negative active material layer 82 from the measured potential of the reference electrode 80 and reduce the occurrence of electrodeposition on the surface of the negative active material layer during charging. Further, the cut-away part 88 is surrounded by the positive active material layer 75 and thus has a high ion infiltration concentration. Thus, a change in the potential can be detected from the filtration concentration by disposing the reference electrode 80 in the cut-away part 88. Thus, according to the energy storage system provided with the electrode assembly 70 of the fifth embodiment, it is possible to estimate the potential on the surface of the negative active material layer with a higher accuracy. Further, the reference electrode 80 disposed in the cut-away part 88 prevents an increase in the thickness of the electrode assembly caused by the placement of the reference electrode 80.
[0088]
It is preferred that more than half of the periphery of the reference electrode 80 in plan view is surrounded by the positive active material layer 75. It is more preferred that two-thirds or more of the periphery of the reference electrode 80 is surrounded by the positive active material layer 75. Although, in Fig. 9(a), the cut-away part 88 is formed in the edge part of the positive active material layer 75 having a substantially rectangular shape, the cut-away part may be formed in another part. For example, a corner part of the positive active material layer 75 having a substantially
rectangular shape may be cut away, or a central part thereof may be cut away into a hole shape.
[0089]
<Sixth Embodiment>
Fig. 10 illustrates a part of an energy storage device 91 provided in an energy storage system of a sixth embodiment. In the sixth embodiment, a reference electrode is disposed on the surface of a connector which connects a negative electrode plate to an external terminal (a negative electrode terminal). Fig. 10 illustrates an electrode assembly 92, a positive electrode terminal 93, a negative electrode terminal 94 and a reference electrode terminal 95 as external terminals, a positive electrode connector 96, a negative electrode connector 97, and a reference electrode 98 in the energy storage device 91. The energy storage device 91 further includes a case and a nonaqueous electrolyte (not illustrated). The electrode assembly 92 is stored in the case, and the nonaqueous electrolyte is injected into the case.
[0090]
The electrode assembly 92 is the same as the electrode assembly 15 of the first embodiment except that no reference electrode is disposed thereon. The positive electrode terminal 93, the negative electrode terminal 94, and the reference electrode terminal 95 are disposed on the outer face of a lid 99.
[0091]
The positive electrode connector 96 electrically connects a positive electrode substrate 100 of a positive electrode plate on one end of the electrode assembly 92 to the positive electrode terminal 93. The negative electrode connector 97 electrically connects a negative electrode substrate 101 of a negative electrode plate on the other end of the electrode assembly 92 to the negative electrode terminal 94. A plate-like member made of metal can be used as the positive electrode connector 96 and the negative electrode connector 97.
[0092]
The reference electrode 98 is covered with a porous insulating member (not illustrated) and disposed on the surface of the negative electrode connector 97. Since the reference electrode 98 is disposed on the surface of the negative electrode connector 97 with the insulating member (not illustrated) interposed therebetween, the negative electrode connector
97 and the reference electrode 98 are electrically insulated from each other. Using the porous insulating member ensures the ion (nonaqueous
electrolyte) conductivity of the insulating member. That is, the reference electrode 98 is disposed in contact with the nonaqueous electrolyte. Further, the reference electrode 98 is electrically connected to the reference electrode terminal 95 through a leading wire 102 (reference electrode connector). A peripheral face of the leading wire 102 is covered with an insulating member.
[0093]
As for the configurations not shown, the first embodiment described above can be referred to. Also in the energy storage system provided with the energy storage device 91 of the sixth embodiment, similarly to the energy storage system of the first embodiment, it is possible to estimate the potential on the surface of the negative active material layer from the measured potential of the reference electrode 98 and reduce the occurrence of electrodeposition on the surface of the negative active material layer during charging. Further, the connector (negative electrode connector 97) is harder, that is, has a higher stiffness than the positive electrode plate, the negative electrode plate, and the separator. Thus, disposing the reference electrode 98 on the surface of the connector results in easy placement of the reference electrode 98. Further, the connector has little change with passage of time as compared to the positive electrode plate, the negative electrode plate, and the separator. Thus, disposing the reference electrode
98 on the connector results in stable placement of the reference electrode 98. Thus, it is possible to measure the potential with high stability. [0094]
<Other Embodiments>
The present invention is not limited to the above embodiments and can be carried out in various modes with modifications and improvements in addition to the above modes. For example, the energy storage system may be a combination of the above embodiments. Although, in the above embodiments, the energy storage device is mainly a nonaqueous electrolyte secondary battery, the energy storage device may be another energy storage device. Examples of the energy storage device include capacitors (an electric double layer capacitor and a lithium ion capacitor).
[0095]
The configuration of the energy storage device in the energy storage system according to the present invention is not particularly limited to any configuration. Examples of the configuration of the energy storage device include a cylindrical battery, a prismatic battery (rectangular battery), and a flat-type battery. The present invention may be implemented as an energy storage system provided with an energy storage apparatus including a plurality of the above energy storage devices. Fig. 11 illustrates an embodiment of the energy storage apparatus. In Fig. 11, an energy storage apparatus 110 includes a plurality of energy storage units 120. Each of the energy storage units 120 includes a plurality of energy storage devices 130. INDUSTRIAL APPLICABILITY
[0096]
The present invention can be preferably used as an energy storage system and a charge method in an automotive power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV).
DESCRIPTION OF REFERENCE SIGNS
[0097]
10: energy storage system
11, 91: energy storage device
11a, 93: positive electrode terminal
lib, 94: negative electrode terminal
11c, 95: reference electrode terminal
12: battery charger
13: arithmetic unit
14: control unit
15, 30, 40, 50, 70, 92: electrode assembly
15a: one end part
15b: the other end part
16, 53, 71 : positive electrode plate
17, 51, 73: negative electrode plate
18, 19, 52, 72: separator
20, 31, 41, 60, 80, 98: reference electrode
21, 61, 74, 100: positive electrode substrate
22, 62, 75: positive active material layer
23, 54, 81, 101: negative electrode substrate
24, 55, 82: negative active material layer
25, 32, 42: insulating member
56, 63, 76, 83: substrate body 57, 59, 64, 77, 84: tab portion
58: separator body
88: cut-away part
96: positive electrode connector
97: negative electrode connector
99: lid
IO2: leading wire (reference electrode connector) 110: energy storage apparatus
120: energy storage unit
130: energy storage device
X: opposed region
Y: negative active material layer surface

Claims

1. An energy storage system comprising:
an energy storage device, the energy storage device including:
a negative electrode plate including a negative active material layer,
a nonaqueous electrolyte, and
a reference electrode disposed in contact with the nonaqueous electrolyte! and
an arithmetic unit that estimates a potential on a surface of the negative active material layer from a measured potential of the reference electrode.
2. The energy storage system according to claim 1, wherein the energy storage device includes a positive electrode plate including a positive active material layer, and
the reference electrode is disposed in a region where the positive active material layer and the negative active material layer are not opposed to each other.
3. The energy storage system according to claim 2, wherein the positive electrode plate includes a positive electrode substrate, and the positive active material layer is formed on a part of the positive electrode substrate,
the negative electrode plate includes a negative electrode substrate, and the negative active material layer is formed on a part of the negative electrode substrate, and
the reference electrode is disposed on a surface of the positive electrode substrate or a surface of the negative electrode substrate.
4. The energy storage system according to claim 2, wherein the reference electrode is disposed on the surface of the negative active material layer.
5. The energy storage system according to claim 2, wherein the energy storage device includes a separator disposed between the positive electrode plate and the negative electrode plate, and
the reference electrode is disposed on a surface of the separator.
6. The energy storage system according to claim 2, wherein the reference electrode is disposed on an end face of the positive electrode plate or an end face of the negative electrode plate.
7. The energy storage system according to claim 2, wherein the positive electrode plate has a cut-away part where the positive active material layer is not formed, and
the reference electrode is disposed in the cut-away part.
8. The energy storage system according to claim 1 or 2, wherein the reference electrode is disposed on a surface of a connector that connects the negative electrode plate to an external terminal.
9. The energy storage system according to any one of claims 1 to 8, further comprising a control unit that stops charging or controls a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer.
10. A charge method comprising stopping charging or controlling a charge current on the basis of an estimated value of the potential on the surface of the negative active material layer using the energy storage system according to any one of claims 1 to 9.
PCT/EP2018/052228 2017-02-06 2018-01-30 Energy storage system and charge method WO2018141723A1 (en)

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