WO2022163539A1 - 二次電池の充電方法および充電システム - Google Patents

二次電池の充電方法および充電システム Download PDF

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Publication number
WO2022163539A1
WO2022163539A1 PCT/JP2022/002256 JP2022002256W WO2022163539A1 WO 2022163539 A1 WO2022163539 A1 WO 2022163539A1 JP 2022002256 W JP2022002256 W JP 2022002256W WO 2022163539 A1 WO2022163539 A1 WO 2022163539A1
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Prior art keywords
charging
secondary battery
lithium
negative electrode
current density
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English (en)
French (fr)
Japanese (ja)
Inventor
亮平 宮前
聡 蚊野
隆弘 福岡
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to JP2022578337A priority Critical patent/JP7788643B2/ja
Priority to US18/274,342 priority patent/US20240128780A1/en
Priority to EP22745760.3A priority patent/EP4287295A4/en
Priority to CN202280012219.6A priority patent/CN116830356A/zh
Publication of WO2022163539A1 publication Critical patent/WO2022163539A1/ja
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
    • H02J7/90—Regulation of charging or discharging current or voltage
    • H02J7/92—Regulation of charging or discharging current or voltage with prioritisation of loads or sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
    • H02J7/90—Regulation of charging or discharging current or voltage
    • H02J7/933—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/46—Accumulators structurally combined with charging apparatus
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/471—Spacing elements inside cells other than separators, membranes or diaphragms; Manufacturing processes thereof
    • H01M50/474—Spacing elements inside cells other than separators, membranes or diaphragms; Manufacturing processes thereof characterised by their position inside the cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
    • H02J7/80—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries including monitoring or indicating arrangements
    • H02J7/82—Control of state of charge [SOC]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
    • H02J7/90—Regulation of charging or discharging current or voltage
    • H02J7/96—Regulation of charging or discharging current or voltage in response to battery voltage
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to a secondary battery charging method and charging system.
  • Non-aqueous electrolyte secondary batteries represented by lithium-ion secondary batteries, have high energy density and high output, and are used as power sources for mobile devices such as smartphones, power sources for vehicles such as electric vehicles, and natural energy sources such as sunlight. It is considered promising as a storage device for
  • Patent Document 1 proposes a non-aqueous electrolyte secondary battery in which lithium metal is deposited on a negative electrode current collector during charging and dissolved during discharging, with the aim of increasing the capacity of the battery.
  • Patent Document 2 discloses a charging method for a secondary battery that has a positive electrode current collector foil, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode current collector foil in this order, and uses the deposition-dissolution reaction of metallic lithium as the negative electrode reaction.
  • a first current density I1 mA/cm 2
  • metallic lithium is deposited on the surface of the solid electrolyte layer on the side of the negative electrode current collector foil, and the negative electrode is activated.
  • one aspect of the present invention provides a positive electrode that absorbs lithium ions during discharging and releases the lithium ions during charging, a negative electrode that deposits lithium metal during charging and dissolves the lithium metal during discharging, and lithium and a non-aqueous electrolyte having ion conductivity, wherein the secondary battery includes a surface of the negative electrode covered with a protective layer, and the two electrodes are charged along a first charging profile.
  • the present invention relates to a method of charging a secondary battery, in which a second charging step is performed in which charging is performed at a constant current of a second current density I2 larger than the first current density I1.
  • another aspect of the present invention provides a positive electrode that absorbs lithium ions during discharge and releases the lithium ions during charging, a negative electrode that deposits lithium metal during charging, and a negative electrode that dissolves the lithium metal during discharging,
  • a secondary battery comprising a non-aqueous electrolyte having lithium ion conductivity and a protective layer covering the surface of the negative electrode; and a charge control unit for controlling charging of the secondary battery, wherein the charge control unit , controlling charging of the secondary battery by selecting one from among one or more charging profiles including at least a first charging profile, wherein the first charging profile is a constant current of a first current density I1 Charging is started from a first charging step in which charging is performed, and following the first charging step, charging is performed at a constant current of a second current density I2 larger than the first current density I1.
  • the present invention relates to a secondary battery charging system in which two charging steps are performed.
  • FIG. 2 is a flow diagram of a secondary battery charging method according to an embodiment of the present disclosure
  • 1 is a schematic configuration diagram of a secondary battery charging system according to an embodiment of the present disclosure
  • FIG. 1 is a longitudinal sectional view schematically showing a lithium secondary battery used in a secondary battery charging system according to an embodiment of the present disclosure
  • FIG. 4 is an enlarged view of a main part showing an example of the electrode group of FIG. 3
  • FIG. 4 is an enlarged view of a main part showing another example of the electrode group of FIG. 3
  • the depth of discharge is the ratio of the amount of electricity discharged to the amount of electricity that the battery in the fully charged state has.
  • state of charge is the ratio of the amount of electricity remaining in the battery to the amount of electricity that the battery in the fully charged state has.
  • the current density (mA/cm 2 ) is the current density per unit facing area (1 cm 2 ) between the positive electrode and the negative electrode, and the total area of the positive electrode mixture layer (or positive electrode active material layer) facing the negative electrode. It is obtained by dividing the current value applied to the battery by (hereinafter also referred to as the total effective area of the positive electrode). For example, when the positive electrode has positive electrode mixture layers on both sides of the positive electrode current collector, the total effective area of the positive electrode is the total area of the positive electrode mixture layers on both sides (that is, the positive electrode collection of each positive electrode mixture layer on both sides). is the sum of the projected areas on one and the other surface of the conductor).
  • a secondary battery charged by the charging method according to the present disclosure includes a positive electrode that absorbs lithium ions during discharging and releases lithium ions during charging, and a negative electrode that deposits lithium metal during charging and dissolves lithium metal during discharging. and a non-aqueous electrolyte having lithium ion conductivity. That is, the secondary battery mainly means, but is not limited to, a lithium (metal) secondary battery.
  • the negative electrode according to the present embodiment is different from a negative electrode in which electron movement in the negative electrode during charge and discharge is mainly due to lithium ion absorption and release by the negative electrode active material (graphite, etc.).
  • the surface of the negative electrode is covered with a protective layer.
  • the lithium metal deposited on the negative electrode is covered with the protective layer, and contact between the lithium metal and the non-aqueous electrolyte is suppressed.
  • the protective layer also has a function of pressing lithium metal.
  • the protective layer can suppress the growth of dendrites of lithium metal. Therefore, side reactions due to contact between lithium metal and the non-aqueous electrolyte can be suppressed, and deterioration of cycle characteristics due to the above side reactions can be suppressed.
  • the charging control section controls the charging according to the depth of discharge as described below, thereby synergistically suppressing the growth of dendrites.
  • a charging method includes charging a secondary battery along a first charging profile.
  • the first charging profile is selected, for example, when the depth of discharge (DOD) of the secondary battery is greater than or equal to the first threshold.
  • DOD depth of discharge
  • charging begins with a first charging step in which charging is performed at a constant current of a first current density I1, followed by a first charging step with a constant current greater than the first current density I1.
  • a second charging step is carried out in which charging is carried out with a constant current of 2 current densities I2.
  • the first threshold may be set to 0%, or may be set to a small value such as 10% or less, but from the viewpoint of shortening the charging time, it is desirable to set the threshold to a relatively large value.
  • the first threshold is set to 0%, the secondary battery is always charged according to the first charging profile regardless of DOD.
  • the charging profile is a recipe that defines conditions such as the charging method, voltage, and current when the secondary battery is charged.
  • the charging profile defines a schedule for each step of charging the secondary battery to a fully charged state.
  • Each charging step is a step of charging the secondary battery under different charging conditions. Charging conditions are regulated by charging current and/or charging voltage.
  • Each charging step may be a constant current charging step or a constant voltage charging step.
  • the DOD when the DOD is shallow, a sufficient underlying layer of lithium metal exists in the negative electrode, so lithium metal is less likely to deposit in a dendrite form than when the DOD is deep. That is, when the DOC is deep, it is necessary to discharge with a small charging current in order to suppress the deposition of dendritic lithium metal.
  • the DOD is shallow, charging with a smaller charging current is not necessary as the DOD is deeper. Rather, increasing the charging current value shortens the charging time and is practical.
  • charging is started with a small constant current of the first current density I1 based on the first charging profile. After that, charging is performed with a constant current having a second current density I2 larger than the first current density I1. As a result, deposition of dendrite-like lithium metal can be suppressed, and degradation of cycle characteristics can be suppressed.
  • Charging at a constant current of the first current density I1 (first charging step) is performed, for example, until the depth of discharge becomes less than a predetermined second threshold, and when the depth of discharge becomes less than the second threshold, The charging is switched to constant current charging at a second current density I2 (second charging step).
  • the DOD when the DOD is shallow and the DOD is less than the first threshold, it is not necessary to charge at the small first current density I1 in order to suppress the deposition of dendritic lithium metal. Priority may be given to charging at a current density greater than I1 to shorten the charging time. Therefore, when the DOD is less than the first threshold, charging may be performed based on the second charging profile different from the first charging profile. In the second charging profile, charging starts from a third charging step in which charging is performed at a constant current of a third current density I3, which is greater than the first current density I1. As a result, it is possible to both suppress the deposition of dendrite-like lithium metal and shorten the charging time.
  • the first current density I1 is, for example, 3.0 mA/cm 2 or less, and may be 1 mA/cm 2 or less. Considering the balance between charging time and cycle characteristics, the first current density I1 is desirably 0.1 mA/cm 2 or more, and may be 0.5 mA/cm 2 or more.
  • the second current density I2 is greater than the first current density I1, for example 4.0 mA/cm 2 or more.
  • I 1 /I 2 may be, for example, 0.1 or more and 0.5 or less, or 0.2 or more and 0.4 or less.
  • I 1 /I 2 may be, for example, 0.2 or more and 0.9 or less, or may be 0.3 or more and 0.7 or less.
  • the third current density I3 in the second charging profile may be equal to the second current density I2 .
  • charging may be performed until the DOD becomes less than the first threshold, and then the second charging step may be performed. That is, the second threshold may be the same as the first threshold.
  • the second charging profile corresponds to the first charging profile skipping the first charging step if the DOD is less than the first threshold.
  • the secondary battery is charged at the current density I1 until the DOD becomes less than the first threshold, and when the DOD is less than the first threshold, the secondary battery is charged at the second current density I2 . will be charged.
  • charging is substantially controlled based on one charging profile having a plurality of charging steps in which charging start conditions and charging end conditions are set by DOD.
  • a simple control circuit structure with simple control can be employed in realizing the charging method.
  • the DOD threshold (first threshold) that determines the selection of the first charging profile and the second charging profile may be, for example, 50% or more and 90% or less, or 70% or more and 90% or less. good. At a shallow depth of discharge where the DOD is less than 50% (that is, the SOC is 50% or more), there is a sufficient base layer on which lithium metal deposits during charging, so lithium metal is less likely to be isolated. In this case, priority is given to selecting the second charging profile and completing charging as quickly as possible.
  • the first charging profile and the second charging profile may each consist of a plurality of charging steps.
  • the first charging profile may further comprise one or more charging steps performed after the second charging step.
  • the second charging profile may further comprise one or more charging steps performed after the third charging step.
  • the number n of charging steps included in the first charging profile may be greater than the number m of charging steps included in the second charging profile.
  • the last charging step among the charging steps included in the first charging profile and/or the second charging profile may be a constant voltage charging step.
  • the value of the charging current is small at first and gradually increases.
  • the charging current rises in smaller increments than in the second charging profile including m charging steps.
  • the charging current may start to decrease after a period of time in which the charging current gradually increases from the start of charging. Normally, in the step of charging the secondary battery, the battery is charged until it reaches a fully charged state (SOC 100%) along the first charging profile or the second charging profile.
  • FIG. 1 is a flowchart showing an example of charging control by the charging control unit in the secondary battery system of the present disclosure.
  • the illustrated charging control method has a step (S1) of selecting either a first charging profile or a second charging profile before starting charging. Such selection is made based on the DOD detected by the DOD detector before the start of the step of charging the secondary battery (hereinafter also referred to as time T).
  • time T the DOD detected by the DOD detector before the start of the step of charging the secondary battery
  • the charging current can be selectively reduced within a necessary range during the usage period of the secondary battery in which charging and discharging are repeated, and the time required for charging can be shortened as a whole.
  • the second charging profile includes at least two charging steps, and the first charging profile includes more charging steps than the second charging profile. That is, when the second charging profile includes m ( ⁇ 2) charging steps, the first charging profile includes n ( ⁇ 3) charging steps.
  • the second charging profile is selected, and when it is equal to or greater than the first threshold, the second charging profile is selected.
  • 1 charging profile is selected (S2). That is, at time T, when the DOD is shallow (when the SOC of the battery is high), the number of charging steps is small, and when the DOD is deep (when the SOC of the battery is low), the number of charging steps is greater.
  • the charging current may be increased in smaller increments than in the second charging profile. That is, in the first charging profile, charging can be started with a smaller charging current than in the second charging profile. Also, in the charging step performed in the latter half of the first charging profile, charging can be performed with a charging current greater than that of the second charging profile.
  • Current density I 21 is greater than current density I 11 (I 21 >I 11 (I 3 >I 1 )).
  • the first charging profile has a higher number of charging steps than the second charging profile and comprises a charging step S13 at a current density I13 following the charging step S12.
  • Current density I 13 is preferably greater than current density I 12 (I 12 ⁇ I 13 ).
  • the charge quantity of electricity (Q 1 ) in the charging step S11 may be 5% or more and 15% or less of the total charge quantity of electricity charged in the step of charging the secondary battery.
  • total amount of electricity charged in the process of charging the secondary battery is the amount of electricity charged from the start of charging until the secondary battery is fully charged. It changes depending on the DOD or SOC of the battery.
  • the “total charged quantity of electricity” charged along the first profile is also referred to as the total charged quantity of electricity P1.
  • Q1 is 5% or more of the total charged quantity of electricity P1
  • the effect of suppressing the growth of dendrite-like lithium metal increases.
  • Q1 is 15% or less of the total amount of charged electricity, a sufficient effect of suppressing the growth of dendritic lithium metal can be obtained while shortening the charging time.
  • the charging step S11 is set, for example, as the first charging step in the first profile.
  • the charging step S21 is set as, for example, the first charging step in the second profile.
  • the charging step S11, the charging step S12 and the charging step S13 in the first profile may all be constant current charging steps.
  • Both the charging step S21 and the charging step S22 in the second profile may be constant current charging steps.
  • I21 is to I22 (the closer I21 / I22 is to 1), the shorter the charging time when charging the secondary battery with the second profile.
  • the larger I12 is relative to I11 (the smaller I11/ I12 is), the more difficult it is for lithium metal to grow in the form of dendrites. Therefore, it is desirable to satisfy I 21 /I 22 >I 11 /I 12 .
  • I22 may be greater than or equal to 6.0 mA/ cm2 . However, if I 22 is too large, the possibility of lithium metal being isolated during charging gradually increases, so I 22 is preferably 8.0 mA/cm 2 or less. I 21 /I 22 may be, for example, 0.1 or more and 0.8 or less, or 0.4 or more and 0.7 or less.
  • I 12 is desirably 1.0 mA/cm 2 or more, and may be 2.0 mA/cm 2 or more or 4.0 mA/cm 2 or more. However, if I 12 is too large, the possibility of lithium metal being isolated during charging gradually increases, so I 12 is preferably 6.0 mA/cm 2 or less.
  • I 13 is desirably 6.0 mA/cm 2 or more, and may be 8.0 mA/cm 2 or more. However, if I 13 is too large, the possibility of lithium metal being isolated during charging gradually increases, so I 13 is preferably 10.0 mA/cm 2 or less.
  • I 12 /I 13 may be, for example, 0.2 or more and 0.9 or less, or may be 0.3 or more and 0.7 or less.
  • the charge quantity of electricity (Q 2 ) in the charging step S21 may be 5% or more and 15% or less of the total charge quantity of electricity charged in the step of charging the secondary battery.
  • the "total charged quantity of electricity" charged along the second profile is also referred to as the total charged quantity of electricity P2.
  • Q2 is 5% or more of the total charged quantity of electricity P2
  • the effect of suppressing the growth of dendrite-like lithium metal increases.
  • Q2 is 15% or less of the total charged quantity of electricity P2
  • a sufficient effect of suppressing the growth of dendritic lithium metal can be obtained while shortening the charging time.
  • the timing of ending each charging step may be controlled by, for example, the charging time, the amount of charged electricity, the voltage, etc., and is controlled by the ratio of the charged amount of electricity to the total charged amount of electricity P1, P2 in each charging step.
  • it may be controlled by SOC, DOD, or charging rate.
  • SOC or DOD may be estimated by voltage.
  • the SOC may be estimated from the voltage to set the charging end voltage in each charging step.
  • charging step S11 at current density I11 is terminated and charging at current density I12 is completed.
  • Charging step S12 is started.
  • the charging step S12 at the current density I12 is ended and the charging step S13 at the current density I13 is started.
  • the charging at the current density I13 is terminated.
  • the first voltage is, for example, a voltage when a charged amount of electricity equivalent to 15% or less of the total charged amount of electricity P1 is charged
  • the second voltage is, for example, equivalent to 50% or less of the total charged amount of electricity P1.
  • the third voltage is, for example, the voltage when the charged quantity of electricity corresponding to 90% or more of the total charged quantity of electricity P1 is charged in total.
  • the charging at the current density I21 is terminated and the charging at the current density I22 is completed.
  • Charging step S22 is started.
  • the battery voltage reaches the fifth voltage in step S22 of charging at current density I22 charging at current density I22 is terminated.
  • the fourth voltage is, for example, a voltage when a charged quantity of electricity corresponding to 15% or less of the total charged quantity of electricity P2 is charged, and the fifth voltage corresponds to, for example, 90% or more of the total charged quantity of electricity P2. It is the voltage when the amount of charging electricity is charged in total.
  • the second voltage may be equal to the fourth voltage
  • the third voltage may be equal to the fifth voltage. That is, the charging termination condition in charging step S12 and the charging termination condition in charging step S21 may be the same, and the charging termination condition in charging step S13 and the charging termination condition in charging step S22 may be the same. good.
  • the first voltage may be a voltage corresponding to the DOD determination threshold (first threshold) in step S1.
  • the charging is substantially controlled based on one charging profile having a plurality of (three in the example of FIG. 1) charging steps in which the charging start condition and the charging end condition are defined based on the DOD. be.
  • control is simple and a simple control circuit structure can be adopted. That is, when the DOD is less than the threshold, the first charging step performs charging at the current density I1 until the DOD reaches the threshold, and the second charging step performs charging at the current density I2 when the DOD is greater than or equal to the threshold.
  • the charging of the secondary battery may be controlled based on the charging profile including at least the steps.
  • the constant voltage charging step S3 may be performed following the constant current charging step. Such a charging step is performed, for example, until the current reaches a predetermined value. For example, after performing the final charging step with a constant current up to a predetermined charging end voltage, the charging step with a constant voltage may be performed with that voltage. After that, discharge is performed with the limit of discharge up to a predetermined discharge end voltage.
  • the protective layer By covering the surface of the negative electrode, the protective layer suppresses contact between the lithium metal deposited on the negative electrode and the non-aqueous electrolyte, and suppresses the growth of lithium metal dendrites. As a result, side reactions due to contact between the lithium metal and the non-aqueous electrolyte can be suppressed, and deterioration of cycle characteristics due to the side reactions can be suppressed.
  • the protective layer may be, for example, a resin layer containing resin.
  • the resin layer may be a mixed layer of resin and inorganic particles. As a result, favorable lithium ion conductivity is easily obtained in the protective layer, and lithium ions move smoothly between the negative electrode and the non-aqueous electrolyte via the protective layer during charging and discharging.
  • resins include fluorine-containing polymers (fluorine-based resins), polyolefin resins, acrylic resins, silicone resins, epoxy resins, polyimides, polyamideimides, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyethylene oxide, and polystyrene.
  • fluorine-based resins fluorine-based resins
  • polyolefin resins acrylic resins, silicone resins, epoxy resins, polyimides, polyamideimides, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyethylene oxide, and polystyrene.
  • Fluorinated resins include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), copolymers of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and copolymers of VdF and tetrafluoroethylene (TFE). It preferably contains at least one selected from the group consisting of coalescence. Among these, PVdF is more preferable.
  • Inorganic particles are particles containing inorganic materials (eg, metal oxides, metal hydroxides, metal composite oxides, metal nitrides, metal carbides, metal fluorides, etc.). Specific examples of inorganic materials include copper oxide, bismuth oxide, tungsten oxide, indium oxide, and silver oxide.
  • the inorganic particles (inorganic materials) may be used singly or in combination of two or more. Among them, the inorganic particles preferably contain at least one selected from the group consisting of copper oxide particles and bismuth oxide particles.
  • the inorganic particles may have a density of 6 g/cm 3 or more in terms of increasing the strength of the protective layer.
  • the density ratio of the inorganic particles to the resin may be 3.5 or more.
  • the inorganic particles are deposited thinly and densely during the formation of the protective layer, and it is thought that a film with a uniform thickness is formed. Therefore, uneven distribution due to aggregation of the inorganic particles in the plane direction of the protective layer is suppressed, variation in strength in the plane direction of the protective layer is suppressed, and reliability of the strength of the protective layer is improved.
  • PVdF as a resin can easily adjust the density ratio of the inorganic particles to the resin material to 3.5 or more, easily increase the strength of the protective layer, has an appropriate degree of swelling with respect to the solvent of the non-aqueous electrolyte, and , is advantageous in terms of ease of processing. By having an appropriate degree of swelling, it is easy to obtain good lithium ion conductivity in the protective layer.
  • the protective layer preferably contains one or more lithium salts.
  • Lithium ion conductivity can be increased by including a lithium salt in the protective layer.
  • the lithium salt contained in the protective layer may be lithium bis(fluorosulfonyl)imide (LFSI).
  • LFSI is preferable because it can enhance the plasticity of the protective layer and improve the film stability.
  • the content of the lithium salt in the entire protective layer is, for example, 0.1 to 20% by mass.
  • the lithium salt contained in the protective layer is included when the protective layer is formed. Lithium salts contained in the non-aqueous electrolyte may penetrate the protective layer. Also, part of the lithium salt contained in the protective layer may dissolve in the non-aqueous electrolyte. However, even if the lithium salt contained in the non-aqueous electrolyte penetrates into the protective layer, the lithium salt derived from the non-aqueous electrolyte remains on the surface of the protective layer, and the lithium salt contained during the film formation exists deep in the protective layer. do. Therefore, the lithium salt contained in the protective layer can be confirmed by disassembling the secondary battery after charging and discharging, taking out the protective layer, and analyzing the composition.
  • the molecular weight (weight average molecular weight) of the resin may be, for example, 10,000 or more and 2,000,000 or less. When the weight average molecular weight is within the above range, it is easy to obtain a protective layer having good flexibility. When winding the negative electrode in the battery manufacturing process, it is easy to follow the negative electrode, and the coverage of the negative electrode surface with the protective layer is easily maintained.
  • the thickness of the protective layer may be 0.1 ⁇ m or more and 5 ⁇ m or less, or 0.5 ⁇ m or more and 2 ⁇ m or less, from the viewpoint of suppressing contact between the lithium metal and the non-aqueous electrolyte and suppressing dendrite penetration of the protective layer. good too.
  • a function required of the protective layer is to have high lithium ion conductivity.
  • high lithium ion conductivity and film stability of the protective layer generally have a conflicting relationship.
  • a protective layer with high lithium ion conductivity tends to have low film strength, and with repeated charge-discharge cycles, lithium metal deposition becomes uneven, the protective film is easily destroyed, and lithium metal dendrites are protected.
  • the layer may be penetrated, or the protective layer may be torn due to the tension associated with the expansion and contraction of the wound body during charging and discharging.
  • the film stability of the protective layer decreases as the number of cycles increases, so simply providing the protective layer on the negative electrode does not sufficiently exhibit the effect of suppressing the growth of dendrites and sufficiently suppresses the deterioration of cycle characteristics. Sometimes I can't.
  • the secondary battery charging system of the present disclosure by combining the control of the charging current density according to the depth of discharge, the protective layer continues to function while the non-uniform deposition of lithium metal is suppressed. Therefore, the effect of suppressing the growth of dendrites is sufficiently exhibited, and remarkably high cycle characteristics can be realized.
  • the protective layer can be formed, for example, by applying a protective layer forming ink to the surface of the negative electrode current collector and drying the ink. Application can be performed using, for example, a bar coater, an applicator, a gravure coater, or the like.
  • the protective layer forming ink can be prepared, for example, by adding and mixing a resin material, a liquid component, and optionally a lithium salt and inorganic particles.
  • a component capable of dispersing inorganic particles and dissolving the resin material can be used. For example, N-methyl-2-pyrrolidone (NMP), dimethyl ether (DME), tetrahydrofuran (THF), etc. can be done.
  • a space for depositing lithium metal is provided between the negative electrode and the positive electrode.
  • the space can be formed by providing a spacer between the negative electrode and the positive electrode. From the viewpoint of improving productivity, etc., the same material as that of the protective layer may be used for the spacer.
  • the thickness of the protective layer may be partially increased, and the thick portion may be used as a spacer. That is, the spacer may be arranged integrally with the protective layer.
  • a coater e.g., gravure coater
  • a line-shaped protrusion may be formed by applying a line-shaped ink. From the viewpoint of improving productivity, etc., the protective layer and the protrusions may be dried at the same time after forming the protrusions.
  • FIG. 2 is a configuration diagram showing an example of a secondary battery charging system according to an embodiment of the present disclosure.
  • the charging system includes a secondary battery 10 and a charging device 101 .
  • An external power supply 105 that supplies electric power to the charging device 101 is connected to the charging device 101 .
  • the charging device 101 includes a charging control section 102 including a charging circuit.
  • Charging control unit 102 selects one charging profile from one or a plurality of charging profiles including at least the first charging profile, and controls charging of the secondary battery according to the selected charging profile.
  • the charging profile can be selected, for example, based on the depth of discharge (DOD) of the secondary battery before charging is started.
  • DOD depth of discharge
  • the charging control unit selects the first charging profile and controls charging of the secondary battery according to the first charging profile.
  • charging begins with a first charging step in which charging is performed at a constant current of a first current density I1, followed by a first charging step with a constant current greater than the first current density I1.
  • a second charging step is carried out in which charging is carried out with a constant current of 2 current densities I2.
  • the charging control unit selects, for example, the second charging profile and controls charging of the secondary battery along the second charging profile.
  • charging starts from a third charging step in which charging is performed at a constant current of a third current density I3, which is greater than the first current density I1.
  • the charging device 101 includes a voltage detection section 103 that detects the voltage of the secondary battery 10 as a DOD detection section that detects the DOD of the secondary battery.
  • the voltage detection unit 103 includes a calculation unit that detects the voltage of the secondary battery 10 before starting charging of the secondary battery and calculates DOD based on the detected voltage.
  • charging control section 102 selects either the first charging profile or the second charging profile. Then, charging of the secondary battery is controlled according to the selected charging profile. After completing the execution of the first step in the first charging profile, the charging control unit 102 may start the second charging step based on the DOD obtained by the calculating unit.
  • the charging device 101 also includes a current detection unit 104 that detects the current output from the secondary battery.
  • Charging control section 102 controls the charging current so that the current value detected by current detecting section 104 does not greatly deviate from a predetermined value.
  • the charging step switching and termination timing are controlled by the voltage (or DOD (or SOC)) detected by the voltage detection unit 103, but the control method is not limited. For example, at least part of the control may be performed based on charging time, amount of charged electricity, and the like.
  • the negative electrode has a negative electrode current collector.
  • lithium metal is deposited on the surface of the negative electrode by charging. More specifically, lithium ions contained in the non-aqueous electrolyte receive electrons on the negative electrode during charging to become lithium metal, which is deposited on the surface of the negative electrode. Lithium metal deposited on the surface of the negative electrode dissolves as lithium ions in the non-aqueous electrolyte due to discharge.
  • the lithium ions contained in the non-aqueous electrolyte may be derived from the lithium salt added to the non-aqueous electrolyte, or may be supplied from the positive electrode active material during charging. There may be.
  • the negative electrode may include a negative electrode current collector and a sheet-like lithium metal that is in close contact with the surface of the negative electrode current collector.
  • a layer that develops capacity by absorbing and releasing lithium ions with a substance (such as graphite) may also be included.
  • the open circuit potential of the negative electrode at full charge may be 70 mV or less with respect to lithium metal (lithium dissolution deposition potential).
  • lithium metal exists on the surface of the lithium ion storage layer at full charge. That is, the negative electrode develops a capacity due to deposition and dissolution of lithium metal.
  • the protective layer covers the surface of the lithium ion occluding layer when lithium metal is not deposited on the surface of the lithium ion occluding layer, and when lithium metal is deposited on the surface of the lithium occluding layer, the lithium metal is covered. covering the surface.
  • the open-circuit potential of the negative electrode at the time of full charge can be measured by disassembling a fully charged battery in an argon atmosphere, taking out the negative electrode, and assembling a cell using lithium metal as a counter electrode.
  • the non-aqueous electrolyte of the cell may be of the same composition as the non-aqueous electrolyte in the disassembled battery.
  • the lithium ion storage layer is formed by layering a negative electrode mixture containing a negative electrode active material.
  • the negative electrode mixture may contain a binder, a thickener, a conductive agent, etc., in addition to the negative electrode active material.
  • Examples of negative electrode active materials include carbonaceous materials, Si-containing materials, and Sn-containing materials.
  • the negative electrode may contain one type of negative electrode active material, or may contain two or more types in combination.
  • Examples of carbonaceous materials include graphite, graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon).
  • the conductive material is, for example, a carbon material.
  • carbon materials include carbon black, acetylene black, ketjen black, carbon nanotubes, and graphite.
  • binders include fluorine resins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubber-like polymers.
  • fluororesins include polytetrafluoroethylene and polyvinylidene fluoride.
  • the negative electrode current collector may be a conductive sheet.
  • a foil, a film, or the like is used as the conductive sheet.
  • the thickness of the negative electrode current collector is not particularly limited, and is, for example, 5 ⁇ m or more and 300 ⁇ m or less.
  • the material of the negative electrode current collector may be any conductive material other than lithium metal and lithium alloy.
  • the conductive material may be a metallic material such as a metal, an alloy, or the like.
  • the conductive material is preferably a material that does not react with lithium. More specifically, materials that form neither alloys nor intermetallic compounds with lithium are preferred.
  • Such conductive materials include, for example, copper (Cu), nickel (Ni), iron (Fe), alloys containing these metal elements, or graphite in which the basal plane is preferentially exposed.
  • alloys include copper alloys and stainless steel (SUS). Among them, copper and/or copper alloys having high electrical conductivity are preferred.
  • the negative electrode current collector may be copper foil or copper alloy foil.
  • the positive electrode includes, for example, a positive electrode current collector and a positive electrode mixture layer supported by the positive electrode current collector.
  • the positive electrode mixture layer includes, for example, a positive electrode active material, a conductive material, and a binder.
  • the positive electrode mixture layer may be formed only on one side of the positive electrode current collector, or may be formed on both sides.
  • the positive electrode is obtained, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive material, and a binder on both sides of a positive electrode current collector, drying the coating film, and then rolling.
  • a positive electrode active material is a material that absorbs and releases lithium ions.
  • positive electrode active materials include composite oxides containing lithium and a metal Me other than lithium (for example, lithium-containing transition metal oxides containing at least a transition metal as metal Me), transition metal fluorides, polyanions, and fluorinated polyanions. , transition metal sulfides, and the like.
  • lithium-containing transition metal oxides are preferable in terms of low production cost and high average discharge voltage.
  • those having a layered rock salt type crystal structure are preferable.
  • the lithium contained in the lithium-containing transition metal oxide is released from the positive electrode as lithium ions during charging and deposited as lithium metal on the negative electrode or the negative electrode current collector. During discharge, lithium metal is dissolved from the negative electrode to release lithium ions, which are occluded by the composite oxide of the positive electrode.
  • Lithium ions involved in charging and discharging are generally derived from the solute in the non-aqueous electrolyte and the positive electrode active material. In this case, the molar ratio of the total amount mLi of Li contained in the positive and negative electrodes to the amount mMe of metal Me contained in the transition metal oxide containing lithium: mLi/mMe is, for example, 1.2 or less.
  • the transition metal elements contained in the lithium-containing transition metal oxide include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, W, and the like.
  • the lithium-containing transition metal oxide may contain one or more transition metal elements.
  • the transition metal elements may be Co, Ni and/or Mn.
  • the lithium-containing transition metal oxide may contain one or more main group elements as needed. Typical elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, and Bi. A typical element may be Al or the like.
  • lithium-containing transition metal oxides composite oxides containing Co, Ni and/or Mn as transition metal elements and optionally containing Al, and having a layered structure and a rock salt type crystal structure are highly This is preferable in terms of obtaining capacity.
  • Lithium-containing transition metal oxides containing at least Ni as a transition metal are particularly preferable in that they have a high capacity.
  • the molar ratio of the total amount mLi of lithium possessed by the positive electrode and the negative electrode to the amount mM of the metal M other than lithium possessed by the positive electrode: mLi/mM is set to, for example, 1.1 or less. may be
  • Lithium-containing transition metal oxides are represented, for example, by general formula (1): Li a Ni b M 1-b O 2 .
  • General formula (1) satisfies m0.9 ⁇ a ⁇ 1.2 and 0.65 ⁇ b ⁇ 1, for example.
  • M may be at least one element selected from the group consisting of Co, Mn, Al, Ti, Fe, Nb, B, Mg, Ca, Sr, Zr and W, for example.
  • the binder conductive agent, etc., for example, those exemplified for the negative electrode can be used.
  • the shape and thickness of the positive electrode current collector can be selected from the shape and range of the positive electrode current collector.
  • Examples of materials for the positive electrode current collector (conductive sheet) include metal materials containing Al, Ti, Fe, and the like.
  • the metal material may be Al, Al alloy, Ti, Ti alloy, Fe alloy, or the like.
  • the Fe alloy may be stainless steel (SUS).
  • a porous sheet having ion permeability and insulation is used for the separator.
  • porous sheets include thin films, woven fabrics, and non-woven fabrics having microporosity.
  • the material of the separator is not particularly limited, but may be a polymer material.
  • polymeric materials include olefin resins, polyamide resins, and cellulose.
  • olefin resins include polyethylene, polypropylene, and copolymers of ethylene and propylene.
  • a separator may also contain an additive as needed. An inorganic filler etc. are mentioned as an additive.
  • the thickness of the separator is not particularly limited, it is, for example, 5 ⁇ m or more and 20 ⁇ m or less, more preferably 10 ⁇ m or more and 20 ⁇ m or less.
  • Non-aqueous electrolyte A non-aqueous electrolyte having lithium ion conductivity includes, for example, a non-aqueous solvent and lithium ions and anions dissolved in the non-aqueous solvent.
  • the non-aqueous electrolyte may be liquid or gel.
  • a liquid non-aqueous electrolyte is prepared by dissolving a lithium salt in a non-aqueous solvent. Lithium ions and anions are generated by dissolving the lithium salt in the non-aqueous solvent.
  • a gel-like non-aqueous electrolyte contains a lithium salt and a matrix polymer, or a lithium salt, a non-aqueous solvent and a matrix polymer.
  • the matrix polymer for example, a polymer material that gels by absorbing a non-aqueous solvent is used. Examples of polymer materials include fluorine resins, acrylic resins, polyether resins, and the like.
  • anions that are used in non-aqueous electrolytes of lithium secondary batteries can be used as the anion.
  • Specific examples include BF 4 ⁇ , ClO 4 ⁇ , PF 6 ⁇ , CF 3 SO 3 ⁇ , CF 3 CO 2 ⁇ , anions of imides, and anions of oxalate complexes.
  • the anion of the oxalate complex may contain boron and/or phosphorus.
  • examples of the anion of the oxalate complex include bisoxalate borate anion, difluorooxalate borate anion (BF 2 (C 2 O 4 ) ⁇ ), PF 4 (C 2 O 4 ) ⁇ , PF 2 (C 2 O 4 ) 2 ⁇ etc.
  • the non-aqueous electrolyte may contain these anions singly or in combination of two or more.
  • the non-aqueous electrolyte preferably contains at least an anion of an oxalate complex, and more preferably contains an oxalate complex anion containing fluorine (especially a difluorooxalate borate anion).
  • an oxalate complex anion containing fluorine especially a difluorooxalate borate anion.
  • the interaction between the fluorine-containing oxalate complex anion and lithium facilitates the uniform deposition of fine particles of lithium metal. Therefore, it becomes easier to suppress local deposition of lithium metal.
  • the fluorine-containing oxalate complex anion may be combined with other anions. Other anions may be PF 6 - and/or imide class anions.
  • non-aqueous solvents examples include esters, ethers, nitriles, amides, and halogen-substituted products thereof.
  • the non-aqueous electrolyte may contain one of these non-aqueous solvents, or two or more of them. Fluoride etc. are mentioned as a halogen substitution body.
  • the concentration of the lithium salt in the non-aqueous electrolyte is, for example, 0.5 mol/L or more and 3.5 mol/L or less.
  • the anion concentration in the non-aqueous electrolyte may be 0.5 mol/L or more and 3.5 mol/L or less.
  • the concentration of the anion of the oxalate complex in the non-aqueous electrolyte may be 0.05 mol/L or more and 1 mol/L or less.
  • a lithium secondary battery there is a structure in which an electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is housed in an exterior body together with an electrolytic solution.
  • an electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is housed in an exterior body together with an electrolytic solution.
  • electrode groups may be applied.
  • a laminated electrode group in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween may be used.
  • the form of the lithium secondary battery is also not limited, and may be, for example, cylindrical, square, coin, button, laminate, or the like.
  • FIG. 3 is a longitudinal sectional view of a lithium secondary battery 10 that is an example of this embodiment.
  • the lithium secondary battery 10 is a cylindrical battery that includes a cylindrical battery case, a wound electrode group 14 housed in the battery case, and a non-aqueous electrolyte (not shown).
  • the battery case is composed of a case body 15 which is a bottomed cylindrical metal container and a sealing member 16 which seals the opening of the case body 15 .
  • the case body 15 has an annular stepped portion 21 formed by partially pressing the side wall from the outside near the opening.
  • the sealing member 16 is supported by the surface of the step portion 21 on the opening side.
  • a gasket 27 is arranged between the case main body 15 and the sealing member 16 to ensure the airtightness of the battery case. Insulating plates 17 and 18 are arranged at both ends of the electrode group 14 in the winding axial direction in the case main body 15 .
  • the sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25 and a cap 26.
  • the cap 26 is arranged outside the case body 15 and the filter 22 is arranged inside the case body 15 .
  • the lower valve body 23 and the upper valve body 25 are connected to each other at their central portions, and an insulating member 24 is interposed between their peripheral edge portions.
  • the filter 22 and the lower valve body 23 are connected to each other at their peripheral edges.
  • the upper valve body 25 and the cap 26 are connected to each other at their peripheral edge portions.
  • a ventilation hole is formed in the lower valve body 23 .
  • the electrode group 14 is composed of a positive electrode 11 , a negative electrode (negative electrode current collector) 12 and a separator 13 .
  • the positive electrode 11, the negative electrode 12, and the separator 13 interposed therebetween are all belt-shaped, and are spirally wound such that their width directions are parallel to the winding axis.
  • Insulating plates 17 and 18 are arranged at both ends of the electrode group 14 in the axial direction, respectively.
  • FIG. 4 is an enlarged view of a main part showing an example of the electrode group in FIG.
  • FIG. 4 is an enlarged view schematically showing a region X surrounded by a dashed line in FIG. 3, showing a state in which lithium metal is not deposited on the surface of the negative electrode current collector.
  • the positive electrode 11 includes a positive electrode current collector and a positive electrode mixture layer.
  • the positive electrode 11 is electrically connected via a positive electrode lead 19 to a cap 26 that also serves as a positive electrode terminal.
  • One end of the positive electrode lead 19 is connected to, for example, the vicinity of the longitudinal center of the positive electrode 11 (the exposed portion of the positive electrode current collector).
  • the other end of the positive electrode lead 19 extending from the positive electrode 11 is welded to the inner surface of the filter 22 through a through hole formed in the insulating plate 17 .
  • the negative electrode 12 has a negative electrode current collector 32 , and the surface of the negative electrode current collector 32 is covered with a protective layer 40 .
  • the protective layer 40 is a layer containing the block polymer described above.
  • the negative electrode 12 is electrically connected via a negative electrode lead 20 to a case body 15 that also serves as a negative electrode terminal.
  • One end of the negative electrode lead 20 is connected, for example, to the longitudinal end of the negative electrode 12 (the exposed portion of the negative electrode current collector 32 ), and the other end is welded to the inner bottom surface of the case body 15 .
  • lithium metal is deposited on the surface of the negative electrode current collector 32 , and the surface of the lithium metal is covered with the protective layer 40 .
  • FIG. 5 is an enlarged view of a main part showing another example of the electrode group in FIG.
  • FIG. 5 is an enlarged view schematically showing a region X surrounded by a dashed line in FIG. 3, showing a state in which lithium metal is not deposited on the surface of the negative electrode current collector.
  • the same components as those in FIG. 4 are denoted by the same reference numerals, and descriptions thereof are omitted.
  • a spacer 50 is provided between the negative electrode 12 having a protective layer 40 on its surface and the separator 13 .
  • the spacer 50 is formed of a line-shaped convex portion provided along the longitudinal direction of the separator 13 .
  • the height of the spacers 50 (line-shaped protrusions) based on the protective layer 40 is, for example, 10 ⁇ m or more and 100 ⁇ m or less.
  • the width of the spacer 50 (line-shaped convex portion) is 200 ⁇ m or more and 2000 ⁇ m or less.
  • the spacer 50 may be made of the same material as the protective layer 40 and may be integrated with the protective layer 40 .
  • the plurality of line-shaped protrusions may be provided in parallel at predetermined intervals.
  • the lithium metal Since the lithium metal is accommodated in the space 51 between the negative electrode 12 and the separator 13, the apparent volume change of the electrode group due to the deposition of the lithium metal during charge-discharge cycles is reduced. Therefore, the stress applied to the negative electrode current collector 32 is also suppressed. In addition, since pressure is applied from the separator 13 to the lithium metal accommodated between the negative electrode 12 and the separator 13, the deposition state of the lithium metal is controlled, the lithium metal is less likely to be isolated, and a decrease in charge-discharge efficiency is suppressed. be.
  • the cross-sectional shape of the spacer 50 is rectangular. However, embodiments of the present disclosure are not limited to this, and may be, for example, a trapezoid, a rectangle with at least one corner curved, an oval, a portion of an oval, or the like.
  • the spacer 50 is provided between the negative electrode 12 and the separator 13 . However, embodiments of the present disclosure are not limited to this, and spacers may be provided between the positive electrode and the separator, or between the positive and negative electrodes and the separator, respectively.
  • a cylindrical lithium secondary battery having a wound electrode group was described, but the shape of the lithium secondary battery is not limited to this, and depending on the application, it may be cylindrical, coin-shaped, or the like. It can be appropriately selected from various shapes such as a square shape, a sheet shape, and a flat shape.
  • the form of the electrode group is also not particularly limited, and may be a laminated type.
  • known ones can be used without particular limitation.
  • Example 1>> (Preparation of positive electrode) Mixing lithium nickel composite oxide (LiNi 0.9 Co 0.05 Al 0.05 O 2 ), acetylene black, and polyvinylidene fluoride (PVdF) at a mass ratio of 95:2.5:2.5 Then, after adding N-methyl-2-pyrrolidone (NMP), the mixture was stirred to prepare a positive electrode slurry. Next, the positive electrode slurry is applied to the surface of an Al foil as a positive electrode current collector, the coating film is dried, and then rolled to form a positive electrode mixture layer (density: 3.6 g/cm 3 ) on both sides of the Al foil. A positive electrode in which was formed was produced.
  • NMP N-methyl-2-pyrrolidone
  • a strip-shaped electrolytic copper foil (15 ⁇ m thick) was prepared as a negative electrode current collector, and a 25 ⁇ m Li foil was attached on the negative electrode current collector.
  • a protective layer forming ink was applied to both surfaces of the negative electrode and dried to form a protective layer (thickness: 2 ⁇ m).
  • a nonaqueous electrolyte was prepared by dissolving a lithium salt in a mixed solvent.
  • FEC fluoroethylene carbonate
  • EMC ethylmethyl carbonate
  • DMC dimethyl carbonate
  • LiPF 6 , LiN(FSO 2 ) 2 hereinafter referred to as LiFSI
  • LiBF 2 (C 2 O 4 ) hereinafter referred to as LiFOB
  • the concentration of LiPF 6 in the non-aqueous electrolyte was 0.5 mol/L, and the concentration of LiFSI was 0.5 mol/L.
  • the content of LiFOB in the non-aqueous electrolyte was set to 1% by mass.
  • a positive electrode lead made of Al was attached to the positive electrode obtained above, and a negative electrode lead made of Ni was attached to the negative electrode obtained above.
  • the positive electrode and the negative electrode were spirally wound via a polyethylene thin film (separator) to prepare a wound electrode group.
  • the electrode group was housed in a bag-shaped exterior body formed of a laminate sheet having an Al layer, and after the non-aqueous electrolyte was injected, the exterior body was sealed to produce a non-aqueous electrolyte secondary battery.
  • part of the positive electrode lead and the negative electrode lead were each exposed to the outside from the outer package.
  • the voltage at 100% SOC is 4.1 V, and the voltage at 100% DOD is 3.0 V.
  • the current value (1/X)C represents the current value when the amount of electricity corresponding to the rated capacity C is constant-current charged or discharged in X hours.
  • 0.1 C is the current value when the amount of electricity corresponding to the rated capacity C is constant-current charged or discharged in 10 hours.
  • Charge-discharge cycle test A charge/discharge cycle test was performed under the following charge/discharge conditions in an environment of 25° C. using the battery after preliminary charge/discharge. In the charging cycle, charging was performed based on a charging profile including two constant current charging steps along the first charging profile described above.
  • the charge/discharge cycle was repeated 250 times, and the discharge capacity C250 after 250 cycles was determined.
  • the ratio C 250 /C 0 ⁇ 100 (%) of C 250 to the discharge capacity C 0 after preliminary discharge was evaluated as the capacity retention rate.
  • Example 1 a negative electrode without a protective layer was produced to obtain battery B1.
  • B1 after preliminary charge/discharge was subjected to a charge/discharge cycle test under the following charge/discharge conditions in an environment of 25 ° C., and the discharge capacity after 250 cycles was C 250 , and the discharge capacity after preliminary discharge was C 0 .
  • the ratio C 250 /C 0 ⁇ 100 (%) was evaluated as the capacity retention rate.
  • the charging cycle was based on a charging profile that included one constant current charging step.
  • Table 1 shows the evaluation results of the capacity retention rate of each battery. Table 1 also shows the configuration of the protective layer and charging conditions (the number of constant-current charging steps) of the batteries used in Examples and Comparative Examples.
  • Example 1 and Comparative Example 3 the constant current charging step was divided into two steps, a constant current charging step at a first current density I1 and a constant current charging step at a second current density I2.
  • a constant current charging step at a first current density I1 was charged to SOC 100% according to the step (I 1 ⁇ I 2 )
  • the capacity retention rate was improved.
  • the charging method and charging system according to the present invention are suitably used for charging lithium secondary batteries in which lithium metal deposits on the negative electrode current collector during charging and dissolves during discharging.

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PCT/JP2022/002256 2021-01-29 2022-01-21 二次電池の充電方法および充電システム Ceased WO2022163539A1 (ja)

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US18/274,342 US20240128780A1 (en) 2021-01-29 2022-01-21 Secondary battery charging method and charging system
EP22745760.3A EP4287295A4 (en) 2021-01-29 2022-01-21 Method for charging a secondary battery and charging system
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WO2024143118A1 (ja) * 2022-12-26 2024-07-04 パナソニックＩｐマネジメント株式会社 非水電解質二次電池の充電制御方法、非水電解質二次電池の充電制御システム、およびそれらを用いた電源装置

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