WO2011065009A1 - リチウムイオン二次電池の充電方法、及び電池パック - Google Patents
リチウムイオン二次電池の充電方法、及び電池パック Download PDFInfo
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- WO2011065009A1 WO2011065009A1 PCT/JP2010/006905 JP2010006905W WO2011065009A1 WO 2011065009 A1 WO2011065009 A1 WO 2011065009A1 JP 2010006905 W JP2010006905 W JP 2010006905W WO 2011065009 A1 WO2011065009 A1 WO 2011065009A1
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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
- H01M10/42—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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
- H01M2200/00—Safety devices for primary or secondary batteries
- H01M2200/10—Temperature sensitive devices
- H01M2200/103—Fuse
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- 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
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- 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 a technique for shortening the charging time while suppressing deterioration of the lithium ion secondary battery.
- lithium-ion secondary batteries having high voltage and high energy density have been widely used as power sources for electronic devices such as notebook computers, mobile phones, and AV devices, and power tools.
- a carbon material capable of inserting and extracting lithium is generally used as a negative electrode active material.
- a lithium-containing composite oxide LiCoO 2 or the like is used as the positive electrode active material.
- the active material has been densified in order to increase the capacity of the secondary battery.
- the charging current of such a battery is increased, the acceptability of lithium ions is likely to decrease, and as a result, the life of the secondary battery is shortened. Therefore, reducing the charging current to a predetermined value or less is effective in improving the cycle characteristics of the secondary battery.
- the charging current is reduced, the amount of electricity that can be stored in the secondary battery per unit time is reduced, so that the charging time is naturally increased.
- the charging time of the secondary battery is required to be shortened in various fields. If the charging current is simply reduced, the request cannot be met.
- Patent Document 2 after performing constant current-constant voltage charging to a predetermined voltage (4.15 V) close to the rated voltage (4.2 V) of the secondary battery, a relatively small current of 0.2 to 0.5 C is used. Constant current-constant voltage charging has been proposed. However, 1C refers to a current that can charge the amount of electricity corresponding to the nominal capacity of the secondary battery in one hour. 0.2C is 1/5 of that, and 0.5C is 1/2 of that.
- Patent Document 3 in a power supply system including two sets of assembled batteries, one set of assembled batteries is composed of a negative electrode having a high lithium occlusion potential and charged and discharged at a charging depth of 20 to 80%. It has been proposed to allow charging.
- Patent Document 1 when switching the charging current, the internal resistance of the battery is calculated, and the voltage drop corresponding to the internal resistance is added to the initial cutoff voltage (charging end voltage), so that the cutoff voltage is also calculated. Switching.
- the cut-off voltage when the cut-off voltage is set by the method of Patent Document 1, the cut-off voltage may become too high when the internal resistance of the battery increases. In such a case, the secondary battery is overcharged and the cycle characteristics are deteriorated.
- Patent Document 2 it is attempted to suppress the deterioration of the secondary battery by suppressing the charging rate to 0.5 C or less in a region close to a fully charged state.
- the time taken for the entire constant voltage charging becomes longer, and the charging time becomes longer. Therefore, it is difficult to apply to a device for which quick charging is desired.
- Patent Document 3 the deterioration is attempted to be suppressed by keeping the upper limit of the charging depth of the secondary battery low. Reducing the charging depth of the secondary battery is generally effective for suppressing deterioration of the secondary battery. However, the capacity that can actually be used is reduced as the charging depth is lowered. Therefore, the proposal of Patent Document 3 can be applied only to limited applications. For example, it is difficult to apply to a device that is desired to be charged to a fully charged state such as a power tool.
- an object of the present invention is to provide an effective means for shortening the charging time of a lithium ion secondary battery.
- One aspect of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a power generation element including a nonaqueous electrolyte, a case having an opening that accommodates the power generation element, and an opening of the case
- a sealing plate for sealing a lithium ion secondary battery comprising: The sealing plate has an external terminal of the positive electrode or the negative electrode and an internal terminal electrically connected to the positive electrode or the negative electrode, and the internal terminal and the external terminal are electrically connected, and between them Has an electric resistance of 0.1 to 2 m ⁇ , (I) executing two or more constant current charging steps for charging the secondary battery by setting the charging current constant until the charging voltage reaches the end-of-charge voltage Ecsf; (Ii) when a charging voltage reaches the charging end voltage Ecsf, performing a constant voltage charging step of charging the secondary battery until the charging current decreases to a predetermined current at the charging end voltage Ecsf,
- the two or more constant current charging steps include: (A
- a battery pack comprising: at least one lithium ion secondary battery having a sealing plate that seals an opening; and a control unit that controls charging of the lithium ion secondary battery,
- the sealing plate has an external terminal of the positive electrode or the negative electrode and an internal terminal electrically connected to the positive electrode or the negative electrode, and the internal terminal and the external terminal are electrically connected, and between them Has an electric resistance of 0.1 to 2 m ⁇
- the control unit is (I) executing two or more constant current charging steps for charging the secondary battery by setting the charging current constant until the charging voltage reaches the end-of-charge voltage Ecsf; (Ii) When the charging voltage reaches the charging end voltage Ecsf, a constant voltage charging step of charging the secondary battery until the charging current decreases to a predetermined current at the charging
- the charging time can be shortened without greatly impairing the charge / discharge cycle life characteristics of the lithium ion secondary battery.
- FIG. 1 is a functional block diagram of a battery pack to which a method for charging a lithium ion secondary battery according to an embodiment of the present invention is applied. It is sectional drawing of an example of the lithium ion secondary battery contained in a battery pack same as the above. It is sectional drawing of an example of the positive electrode of a lithium ion secondary battery same as the above. It is a flowchart of the charge process of the charging method of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is a flowchart of the charging current correction process of a charging process same as the above. It is a table which shows an example of charging current information.
- the present invention relates to a method for charging a lithium ion secondary battery having a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, a nonaqueous electrolyte, a case having an opening, and a sealing plate for sealing the opening of the case.
- the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte are accommodated in the case.
- the sealing plate seals the opening of the case in a state where the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte are accommodated in the case.
- the case can have various shapes such as a cylindrical shape and a square shape. Although the number of openings in the case is usually one, the present invention is not limited to this. For example, a case having a cylindrical shape or a rectangular tube shape with openings at both ends can be used as the case. In that case, each of the openings at both ends is sealed with a sealing plate. Thus, the present invention can also be applied to a secondary battery having two or more sealing plates.
- the sealing plate has a positive or negative external terminal and an internal terminal electrically connected to the positive or negative electrode.
- the internal terminal and the external terminal are electrically connected, and the electrical resistance between them is 0.1 to 2 m ⁇ .
- the electrical resistance of each sealing plate is 0.1 to 2 m ⁇ .
- this method in a range where the charging voltage is lower than the end-of-charge voltage Ecsf, the secondary battery is charged with a constant current at a plurality of target voltages including the end-of-charge voltage Ecsf, and after the charging voltage reaches the end-of-charge voltage Ecsf, Control is performed so that the secondary battery is charged at a constant voltage with the charge end voltage Ecsf until the charging current decreases to a predetermined current. That is, this method relates to a technique for improving the conventional constant current-constant voltage charging. In the conventional constant current-constant voltage charging, the constant current charging and the constant voltage charging are each one step, but in this method, the constant current charging includes a plurality of steps.
- the secondary battery is charged with a constant current at a considerably large charging rate of 1 to 5 C (generally, the charging rate is less than 1 C) until the minimum target voltage Ecs (1) is reached.
- 1C means the electric current which can charge the electric quantity equivalent to the nominal capacity of a secondary battery in 1 hour.
- a more preferable charging rate is 2 to 5C. More preferably, it is 3 to 5C.
- the life of the secondary battery is generally shortened as described above. Therefore, simply increasing the charging rate cannot reduce the charging time while suppressing the deterioration of the cycle characteristics of the secondary battery.
- the reason why the charging at the high rate as described above is possible with this method is that the electrical resistance between the internal terminal and the external terminal provided on the sealing plate is suppressed to a very low value.
- the ratio of the current Ic (k) to Ic (1) is 0.1 to 0.7.
- the difference ⁇ V between the target voltages Ecs (k) and Ecs (1) is 0.05 to 0.2V.
- the cycle characteristics refer to the relationship between the number of cycles and the discharge capacity when the secondary battery is repeatedly charged and discharged under a predetermined voltage range and under predetermined conditions.
- the number of cycles until the discharge capacity decreases from the initial capacity by a predetermined rate is also referred to as the cycle life of the secondary battery or simply as the life.
- a positive temperature coefficient (PTC) element that cuts off a current when the temperature rises is provided between an internal terminal and an external terminal of a sealing plate of a lithium ion secondary battery.
- the PTC element also has an electrical resistance at room temperature higher than that of a normal conductor (metal such as aluminum).
- the electrical resistance of the sealing plate including the PTC element is usually about 10 to 13 m ⁇ .
- the electrical resistance of the sealing plate (more specifically, the electrical resistance between the internal terminal and the external terminal; the same applies hereinafter) is a very low value of 0.1 to 2 m ⁇ .
- the internal resistance when a lithium ion secondary battery having a nominal capacity of 1.3 to 2.2 Ah is discharged at 1 C in a fully charged state can be suppressed to 10 to 25 m ⁇ .
- the electrical resistance of the sealing plate is large, the internal resistance of the entire secondary battery also increases. As a result, increasing the charging current increases the voltage drop. Therefore, when charging is performed at a high rate as described above, it is necessary to set the charging voltage to be considerably high. However, when the charging voltage of the secondary battery is increased, the deterioration of the secondary battery is promoted accordingly, and the life is shortened. Therefore, by reducing the internal resistance of the secondary battery, it is possible to suppress deterioration of the secondary battery when charged at a high rate.
- the simplest method for suppressing the internal resistance of the secondary battery is to reduce the electrical resistance of the sealing plate. It is of course possible to reduce the internal resistance of the secondary battery by other methods. However, reducing the internal resistance of the secondary battery by other methods may affect the power generation capacity of the battery. According to the present invention, the above-described effects can be obtained without adversely affecting the power generation capacity of the battery.
- the positive electrode has a general formula: LiNi x Co y M 1-xy O 2 (where M is a group 2 element, group 3 element, group 4 element, 7 in the long-period periodic table)
- a lithium-containing composite oxide which is at least one element selected from the group consisting of group elements and group 13 elements and is represented by 0.3 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.4).
- a lithium ion secondary battery (referred to as a Ni-based positive electrode battery) using a lithium nickelate-based lithium-containing composite oxide (referred to as a Ni-based positive electrode material) as a positive electrode material (more specifically, a positive electrode active material) is cobalt acid.
- a lithium ion secondary battery (referred to as a Co-based positive electrode battery) using a lithium-based lithium-containing composite oxide (hereinafter referred to as a Co-based positive electrode material) as a positive electrode material, It is easy to shorten the charging time.
- the Ni-based positive electrode material has a lower potential than the Co-based positive electrode material when compared at the same charge depth.
- the Ni-based positive battery has a lower charging voltage profile than the Co-based positive battery. Therefore, even if a battery of the same capacity is charged with the same current, the time until the charging voltage reaches the minimum target voltage is longer for Ni-based positive batteries than for Co-based positive batteries. As a result, the ratio of the constant current charging area to the entire charging can be increased.
- the Ni-based positive electrode battery charges a larger amount of electricity by constant current charging than the Co-based positive electrode battery. It is possible. Since constant current charging has a larger charging rate (charging current) than constant voltage charging, the charging time can be shortened by increasing the proportion of the constant current charging region in the entire charging.
- the Ni-based positive battery can improve the cycle characteristics only by setting the charging time to the same level as the Co-based positive battery. Therefore, by setting the general formula of the lithium-containing composite oxide used for the positive electrode material as described above, it is possible to easily shorten the charging time while suppressing deterioration in cycle characteristics.
- the minimum target voltage Ecs (1) is set to 3.8 to 4V.
- the target voltage Ecs (1) when charging at a high rate as described above to 4 V or less, it is possible to prevent the lithium ion acceptability of the negative electrode from being lowered. Therefore, it is possible to prevent the cycle characteristics from being deteriorated.
- the target voltage Ecs (1) by setting the target voltage Ecs (1) to 3.8 V or more, the charging time can be shortened more effectively.
- a more preferable range of the target voltage Ecs (1) is 3.8 to 3.9V.
- At least one other target voltage Ecs (k) that is larger than the above-described minimum target voltage Ecs (1) is set to 4 to 4.2V.
- the maximum target voltage Ecs (k) is the end-of-charge voltage.
- the current Ic (k) set corresponding to each of the at least one target voltage Ecs (k) is a current of 0.5 to 2C smaller than the current Ic (1). .
- the current Ic (k) is set to a relatively small current of 0.5 to 2C, so that the lithium ion acceptability of the negative electrode is lowered. Can be suppressed. Therefore, deterioration of cycle characteristics due to charging at a high rate in the high voltage range can be suppressed.
- a more preferable range of the current Ic (k) is 0.5 to 1.5C.
- the frequency of use of the secondary battery is detected, and the current Ic (1) is reduced based on the detected usage frequency so that the current Ic (1) decreases as the usage frequency increases. ) Is corrected.
- the usage frequency of the secondary battery can be detected, for example, by counting the number of times the secondary battery has been charged.
- the current Ic (1) may be reduced by a predetermined amount ⁇ I1 each time the secondary battery is charged / discharged once, or the predetermined amount ⁇ I2 ( ⁇ I2) each time the charge / discharge is repeated several times.
- the current Ic (1) may be reduced by> ⁇ I1).
- the current Ic (1) can be reduced according to the deterioration rate of the secondary battery or electrode calculated from the data relating to the cycle characteristics of the secondary battery acquired in advance.
- the battery deterioration rate for example, capacity reduction rate
- the (n-1) th cycle (where n is an integer of 2 or more)
- the current Ic (1) in the nth cycle can be set to P ⁇ (1 ⁇ Q / 100).
- the rate of decrease of the initial current Ic (1) may be increased, and the rate of decrease of the current Ic (1) may be decreased after the number of cycles has increased to some extent. This is because the polarization voltage tends to have a particularly large initial increase.
- the number of times the secondary battery is charged may be counted by a cycle count function of a battery management device (BMU: Battery Management Unit) built in the battery pack.
- BMU Battery Management Unit
- the present invention provides at least one lithium ion secondary comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, a nonaqueous electrolyte, a case having an opening, and a sealing plate for sealing the opening of the case.
- the present invention relates to a battery pack including a battery and a control unit that controls charging of a lithium ion secondary battery.
- the sealing plate has a positive or negative external terminal and an internal terminal electrically connected to the positive or negative electrode, the internal terminal and the external terminal are electrically connected, and the electrical resistance therebetween is 0.1 to 2 m ⁇ .
- the control unit charges the secondary battery with a plurality of target voltages including the charging end voltage Ecsf, and after the charging voltage reaches the charging end voltage Ecsf, Control is performed so that the secondary battery is charged at a constant voltage with the charge end voltage Ecsf until the charging current decreases to a predetermined current.
- the control unit in the range where the charging voltage is lower than the end-of-charge voltage Ecsf, (a) within the range of 1 to 5C until the charging voltage reaches the minimum target voltage Ecs (1).
- the secondary battery is controlled to be charged with a predetermined current Ic (1).
- the target voltage Ecs (k) is switched so that the secondary battery is charged with the current Ic (k) set to.
- the battery pack includes a counter that counts the number of times the secondary battery is charged, and the control unit determines the current Ic (1) so that the current Ic (1) decreases as the number of times of charging increases based on the number of times of charging. It is preferable to correct (1).
- a fuse is interposed between the internal terminal and the external terminal.
- a fuse By including a fuse between the internal terminal and the external terminal, it becomes possible to cut off the current when an excessive current flows through the secondary battery. Therefore, it is possible to exclude the PTC element from the sealing plate or the like. This makes it easy to reduce the electrical resistance of the sealing plate or the like.
- FIG. 1 is a functional block diagram showing a battery pack to which a method for charging a lithium ion secondary battery according to Embodiment 1 of the present invention is applied.
- the battery pack 10 includes a secondary battery 12, a charge / discharge circuit 14, a voltage detection unit 16 that detects the voltage of the secondary battery 12, and a current detection unit 17 that detects the current of the secondary battery 12.
- the battery pack 10 can be connected to the load device 20 and the external power supply 22.
- the charge / discharge circuit 14 includes a control unit 18.
- the secondary battery 12 of the battery pack 10 may be a single lithium ion secondary battery or an assembled battery in which a plurality of lithium ion secondary batteries are connected in parallel and / or in series.
- the control unit 18 may be provided independently of the charge / discharge circuit 14. A part of the control function of the control unit 18 described later may be provided in the load device 20, or may be provided in a charger or the like for charging the battery pack 10.
- the load device 20 is connected to the secondary battery 12 through the charge / discharge circuit 14.
- the secondary battery 12 is connected to an external power source 22 such as a commercial power source via the charge / discharge circuit 14.
- the voltage detection unit 16 detects an open circuit voltage (OCV: Open Circuit Voltage) and a closed circuit voltage (CCV: Closed Circuit Voltage) of the secondary battery 12, and sends the detected value to the control unit 18.
- OCV Open Circuit Voltage
- CCV Closed Circuit Voltage
- the control unit 18 basically controls the secondary battery 12 to be charged / discharged in a predetermined voltage range.
- a control unit can be composed of a CPU (Central Processing Unit), a microcomputer, an MPU (Micro Processing Unit), a main storage device, an auxiliary storage device, and the like.
- auxiliary storage device nonvolatile memory or the like
- information on the target voltage when the secondary battery 12 is charged with constant current information on the charging current, information on the end-of-charge voltage, information on the end-of-discharge voltage, and charging Information (a charging current correction table or the like) related to a correction amount when correcting the current according to the usage frequency of the secondary battery is stored.
- the information on the charging current includes charging currents (Ic (1) and Ic (k) described later) for each of a plurality of target voltages (Ecs (1) and Ecs (k) described later).
- the lithium ion secondary battery 24 in the illustrated example has a cylindrical shape
- the present invention is not limited to this and is applied to lithium ion secondary batteries having various shapes such as a square shape, a flat shape, and a pin shape. be able to.
- the lithium ion secondary battery 24 includes an electrode group 31 formed by spirally winding a positive electrode 26, a negative electrode 28, and a separator 30 interposed therebetween.
- the electrode group 31 is housed in a bottomed cylindrical metal case 32 having an opening together with a non-aqueous electrolyte (not shown). Inside the case 32, an upper insulating plate 36 and a lower insulating plate 38 are disposed on the upper and lower sides of the electrode group 31, respectively.
- the opening of the case 32 is sealed by the assembly sealing plate 34, and the electrode group 31 and the nonaqueous electrolyte are thereby sealed inside the case 32.
- the assembly sealing plate 34 is placed on a small diameter portion 46 provided on the upper portion of the case 32 in a state where the assembly sealing plate 34 is electrically insulated from the case 32 by an insulating gasket 44. In this state, the assembly sealing plate 34 is crimped by crimping the opening end of the case 32 so that the peripheral edge of the assembly sealing plate 34 is sandwiched between the small diameter portion 46 and the opening end from above the gasket 44. Attach to the opening of the case 32.
- the assembly sealing plate 34 includes a hat-shaped terminal plate 34a, an annular PTC element 34b, a circular (metal) thin plate 34c, an annular gasket 34d, a circular intermediate plate 34f having a convex portion 34e at the center, and a dish-shaped bottom plate. 34g is included.
- Each of the terminal plate 34a, the middle plate 34f, and the bottom plate 34g has at least one vent hole 34h.
- the peripheral edge of the terminal board 34a is in contact with the PTC element 34b.
- the PTC element 34b is in contact with the thin plate 34c.
- the terminal plate 34a and the thin plate 34c are electrically connected via the PTC element 34b.
- a gasket 34d is disposed between the thin plate 34c and the middle plate 34f.
- the gasket 34d provides electrical insulation between the peripheral edge of the thin plate 34c and the peripheral edge of the intermediate plate 34f.
- the central portion of the thin plate 34c and the convex portion 34e of the intermediate plate 34f are welded. Thereby, the thin plate 34c and the middle plate 34f are electrically connected.
- the peripheral edge of the bottom plate 34g is in contact with the peripheral edge of the intermediate plate 34f.
- the bottom plate 34g and the terminal plate 34a are electrically connected.
- the bottom plate 34 g is connected to the positive electrode 26 via the positive electrode lead 40. Therefore, the bottom plate 34 g functions as an internal terminal of the positive electrode 26 provided on the assembly sealing plate 34.
- the terminal plate 34 a functions as an external terminal of the positive electrode 26.
- the negative electrode 28 is connected to the bottom of the case 32 via the negative electrode lead 42, and the entire case 32 functions as an external terminal of the negative electrode 28.
- the bottom plate 34g is connected to the negative electrode 28 via a lead so that the bottom plate 34g functions as an internal terminal of the negative electrode 28 provided on the assembly sealing plate 34, and the terminal plate 34a is connected to the outside of the negative electrode 28. It is also possible to function as a terminal.
- the positive electrode 26 is connected to the case 32 via a lead, and the case 32 functions as an external terminal of the positive electrode 26.
- the battery current becomes too large for some reason, the temperature of the PTC element 34b rises and the resistance of the PTC element 34b increases dramatically. Thereby, the current between the bottom plate 34g and the terminal plate 34a is interrupted. Furthermore, when the battery internal pressure rises for some reason, the central portion of the thin plate 34c is relatively easily broken. When the central portion of the thin plate 34c is broken, the thin plate 34c and the intermediate plate 34f are not in contact with each other, and the current therebetween is interrupted.
- the electrical resistance between the bottom plate 34g of the assembly sealing plate 34 and the terminal plate 34a is suppressed to 0.1 to 2 m ⁇ at room temperature (for example, 25 ° C.).
- the normal electrical resistance of a normal assembly sealing plate is about 12 to 13 m ⁇ .
- the positive electrode 26 includes a positive electrode current collector 26a made of, for example, aluminum foil, and a positive electrode active material layer 26b formed on at least one surface of the positive electrode current collector 26a.
- the positive electrode active material layer 26b is made of a mixture of a positive electrode active material, a conductive material, and a binder.
- the positive electrode active material the general formula: LiNi x Co y M 1- xy O 2 (where, M is in the long period periodic table, Group 2 elements, Group III elements, Group 4 elements, Group 7 elements and 13
- a lithium-containing composite oxide which is at least one element selected from the group consisting of group elements and is represented by 0.3 ⁇ x ⁇ 1.0, 0 ⁇ y ⁇ 0.4).
- this lithium-containing composite oxide is used, the effects of shortening the charge time and improving the charge / discharge cycle life characteristics are remarkably obtained.
- Such a lithium-containing composite oxide can be produced by a known method.
- M When x is 0.3 or more, the effect of reducing the charging voltage by using the Ni-based positive electrode material is remarkably obtained. Similarly, when y is less than 0.4, the effect of reducing the charging voltage is remarkably obtained.
- group 2 elements include Mg and Ca.
- Group 3 elements include Sc and Y.
- group 4 elements include Ti and Zr.
- An example of a Group 7 element is Mn.
- group 13 elements include B and Al. Among these, M is most preferably Al in terms of excellent stability of the crystal structure and ensuring safety.
- a carbon material such as natural graphite, artificial graphite, carbon black, or acetylene black can be used.
- binder polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) can be used.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- a metal foil such as an aluminum foil can be used for the positive electrode current collector.
- the positive electrode is obtained by applying a positive electrode paste obtained by dispersing a mixture of a positive electrode active material, a conductive material, and a binder in a dispersion medium such as N-methyl-2-pyrrolidone on a positive electrode current collector. It can be obtained by drying.
- the negative electrode 28 also includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.
- the negative electrode active material layer is composed of a mixture of a negative electrode active material, a conductive material, and a binder.
- a carbon material capable of inserting and extracting lithium, artificial graphite, or natural graphite can be used.
- a metal foil such as a nickel foil or a copper foil can be used for the negative electrode current collector.
- the conductive material and the binder the same materials as the positive electrode can be used.
- the electrolytic solution includes a non-aqueous solvent and a supporting salt that dissolves in the non-aqueous solvent.
- a lithium salt such as lithium hexafluorophosphate (LiPF 6 ) can be used as the supporting salt.
- cyclic esters such as ethylene carbonate (EC) and propylene carbonate (PC) with chain esters such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC)
- DMC dimethyl carbonate
- DEC diethyl carbonate
- MEC methyl ethyl carbonate
- FIGS. 4 and 5 are flowcharts of processing executed by, for example, the CPU of the control unit.
- step S1 when charging of the secondary battery 12 is started, the voltage E of the secondary battery 12 detected by the voltage detection unit 16 is compared with the minimum target voltage Ecs (1), and E is Ecs ( It is determined whether it is smaller than 1) (step S1).
- step S1 If the voltage E is smaller than the target voltage Ecs (1) (Yes in step S1), the current Ic (1) corresponding to the target voltage Ecs (1) is read from the information on the charging current, and the charging current Ic is set to Ic (1) (step S2).
- the set current Ic (1) is corrected by a charging current correction process to be described later (step S3), whereby the secondary battery 12 is charged with a constant current with the corrected current Ic (1).
- the charging current correction process can be omitted.
- the secondary battery 12 is charged with a constant current with the current Ic (1) set in step S2.
- Ecs (1) is a constant voltage in the range of 3.8 to 4V.
- Ic (1) before correction is a constant current within a range of 1 to 5C.
- step S3 When a predetermined time (for example, 5 ms) elapses after step S3, the process returns to step S1.
- the procedure of steps S1 to S3 is repeatedly executed until the voltage E becomes equal to or higher than the target voltage Ecs (1) (No in step S1).
- step S1 If the voltage E is equal to or higher than the target voltage Ecs (1) (No in step S1), the voltage E is further compared with another target voltage Ecs (k) to determine whether E is smaller than Ecs (k). (Step S4). Ecs (k) is at least one target voltage greater than Ecs (1).
- the Ecs (k) is equal to the end-of-charge voltage Ecsf of the secondary battery 12.
- the maximum one of them is the end-of-charge voltage Ecsf, and the others are voltages larger than Ecs (1) and smaller than Ecsf. is there.
- step S4 If the voltage E is smaller than the target voltage Ecs (k) (Yes in step S4), the current Ic (k) corresponding to the target voltage Ecs (k) is read from the charging current information, and the charging current is read. Ic is set to the current Ic (k) (step S5). As a result, the secondary battery 12 is charged at a constant current with the set current Ic (k).
- Ecs (k) is preferably a voltage within the range of 4 to 4.2V.
- Ic (k) is preferably 0.5 to 2C.
- step S5 When a predetermined time (for example, 5 ms) elapses after step S5, the process returns to step S4.
- the procedure of steps S4 and S5 is repeatedly executed until the voltage E becomes equal to or higher than the target voltage Ecs (k) (No in step S4).
- step S4 When there are a plurality of target voltages Ecs (k) that are larger than the target voltage Ecs (1), the procedures of steps S3 and S4 are executed in order from the smallest. If the voltage E is equal to or higher than the largest target voltage Ecs (k) (that is, the charging end voltage Ecsf) (No in step S4), the constant current charging is terminated and the charging mode is switched to the constant voltage charging mode. Thus, constant voltage charging of the secondary battery 12 at the charging end voltage Ecsf is started (step S6).
- step S6 when there is only one target voltage Ecs (k) larger than the target voltage Ecs (1), if the voltage E is equal to or higher than the target voltage Ecs (k) (that is, the end-of-charge voltage Ecsf) (No in step S4), constant voltage charging of the secondary battery 12 at the charge end voltage Ecsf is started (step S6).
- the charging current Ic is compared with a predetermined charging end current Ice, and it is determined whether Ic is equal to or less than Ice (step S7). If Ic is larger than Ice (No in step S7), the procedure of step S6 is executed again after a predetermined time has elapsed. The procedures of steps S6 and S7 are repeatedly executed until Ic becomes equal to or less than Ice (Yes in step S7).
- the charge termination current Ice can be set to, for example, 50 to 140 mA.
- step S7 If Ic is less than or equal to Ice (Yes in step S7), charging is stopped (step S8), and the process is terminated.
- FIG. 5 is a flowchart of an example of the charging current correction process.
- the control unit 18 includes a charge counter that counts the number of times the secondary battery 12 is charged. And the usage frequency of the secondary battery 12 shall be represented by the frequency
- the present invention is not limited to this, and as described above, the deterioration rate of the secondary battery, for example, the reduction rate of the capacity can also be used as the parameter indicating the usage frequency of the secondary battery 12. Furthermore, the internal resistance of the secondary battery 12 can be measured, and the increase amount can be used as a parameter representing the usage frequency of the secondary battery 12.
- a parameter indicating the usage frequency of the secondary battery 12, that is, the number of times of charging Nc counted by the above-described number of times of charging counter is read (step S11).
- a charging current correction table made up of table data indicating the correspondence relationship between the number of times of charging and the correction amount ⁇ I of the current Ic (1) is collated, and The correction amount ⁇ I is read (step S12).
- FIG. 6 shows an example of the charging current correction table.
- the increase rate of the polarization voltage is initially increased, the amount of increase of ⁇ I1, ⁇ I2, ⁇ I3,... Can be gradually reduced.
- the charging current is constant from Ic (1) every charge cycle by calculating a certain correction amount from the data relating to the secondary battery deterioration rate obtained in advance for the secondary battery 12. You may correct
- the retrieved correction amount ⁇ I is subtracted from the current Ic (1) set in step S2 (step S13).
- the current Ic (1) is corrected to an optimum value according to the usage frequency of the secondary battery 12 or the increase of the polarization voltage.
- the cylindrical lithium ion secondary battery shown in FIG. 2 used for the charging method of the present invention was prepared according to the following procedure.
- the positive electrode paste was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 ⁇ m and dried to form a positive electrode active material layer on both surfaces of the positive electrode current collector. In this way, a plate-like or sheet-like positive electrode was obtained. Thereafter, this positive electrode was rolled and cut to obtain a belt-like positive electrode (thickness 0.110 mm, width 57 mm, length 720 mm).
- LiPF 6 LiPF 6 was dissolved at a concentration of 1 mol / L in a non-aqueous solvent in which EC, MEC, and DMC were mixed at a volume ratio of 1: 1: 8 to perform non-aqueous electrolysis.
- a liquid was prepared.
- the negative electrode lead pulled out from the negative electrode was welded to the inner bottom surface of the case.
- Several types of assembled sealing plates with different electrical resistances were prepared.
- the positive electrode lead pulled out from the positive electrode was welded to the lower surface of each assembly sealing plate.
- the opening end of the case was caulked to the peripheral edge of the assembly sealing plate via a gasket to seal the opening of the case.
- 18650-size cylindrical lithium ion secondary batteries for test (diameter: 18 mm, height: 65 mm, nominal capacity: 1800 mAh) having different electrical resistances of the assembled sealing plates were produced.
- the assembly sealing plate adjusted the electrical resistance between the external terminal (terminal plate) and the internal terminal (bottom plate) mainly by adjusting the thickness of the PTC element.
- Example 1 Among the above-described lithium ion secondary batteries for testing, an assembly sealing plate having an electrical resistance of 1 m ⁇ between the bottom plate and the terminal plate was used.
- the lithium ion secondary battery was charged at a constant current with a current of 2 C (Ic (1)) until the charging voltage reached 3.8 V (Ecs (1)) (first step). After the charging voltage reached 3.8V, constant current charging was performed at a charging current of 1C (Icf) until it reached 4.2V (Ecsf) (second step). After the charging voltage reached 4.2 V, the charging end current was set to 50 mA at that voltage, and the secondary battery was charged at a constant voltage (third step).
- Example 2 In the first step, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 1 except that Ecs (1) was set to 4V.
- Example 3 In the first step, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 1 except that Ic (1) was set to 3C.
- Example 4 In the first step, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 1 except that Ic (1) was set to 5C.
- Example 5 In the first step, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 1 except that Ic (1) was set to 5C and Ecs (1) was set to 4V.
- Example 6 Among the lithium ion secondary batteries for testing described above, those having an electrical resistance of the assembly sealing plate of 1.5 m ⁇ are used.
- Ic (1) is set to 5C and Ecs (1) is set to 4V. Except for the above, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 1.
- Example 7 Among the lithium ion secondary batteries for testing described above, those having an assembly sealing plate with an electric resistance of 2 m ⁇ were used, and in the first step, Ic (1) was set to 5C and Ecs (1) was set to 4V. Except for this, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 1.
- Comparative Example 2 300 cycles of charge / discharge treatment was performed in the same manner as in Comparative Example 1 except that the charge current was set to 5 C in constant current charging.
- Comparative Example 4 300 cycles of charge / discharge treatments were carried out in the same manner as in Comparative Example 3 except that the lithium ion secondary battery for test described above had an assembly sealing plate with an electrical resistance of 12 m ⁇ .
- Example 7 and Comparative Example 3 when Example 7 and Comparative Example 3 are compared, it is understood that a decrease in cycle characteristics can be suppressed by suppressing the electrical resistance of the assembly sealing plate to 2 m ⁇ or less.
- the electric resistance of the sealing plate and the target voltage Ecs (1) for high rate charging are different between Example 7 and Comparative Example 3.
- Example 7 in which the electrical resistance of the sealing plate is 2 m ⁇ , the capacity retention rate at the 300th cycle is 60%.
- Comparative Example 3 in which the electrical resistance of the sealing plate is 2.5 m ⁇ the capacity retention rate is reduced to 50%. This is presumably because in Comparative Example 3, the polarization voltage was increased, and the actual charging voltage was higher than in Example 7, resulting in a decrease in cycle characteristics.
- the charging time tends to be shorter as the current Ic (1) in the first step is larger. Conversely, the smaller the current Ic (1) in the first step, the higher the capacity retention rate tends to be.
- charging is performed when the target voltage (target voltage in the first step) when switching from high rate charging to low rate charging is lower. The time is getting longer. On the other hand, the charge / discharge cycle life characteristics are improved.
- Example 7 is equal to Example 6 in the first step current Ic (1). Nevertheless, the charging time of Example 7 is longer than that of Example 6 because the electric resistance of the sealing plate is larger than that of Example 6 and thus the polarization voltage is increased. As a result, in Example 7, the voltage that can be actually charged at a high rate of 5C is lower than that in Example 6 when compared with, for example, an open circuit voltage.
- Example 8 The six test specimens produced as described above were electrically connected in 2 parallel ⁇ 3 series to produce a battery group. And the battery pack was produced by providing the battery group with BMU (battery management unit).
- BMU battery management unit
- the battery pack produced above was charged with a constant current at 5 C until the charging voltage reached the target voltage of 12 V (first step). After the first step, the battery pack was charged with a constant current at 1 C until the charge voltage reached a charge end voltage of 12.6 V (second step). After the second step, the battery pack was charged at a constant voltage with the end-of-charge voltage until the charge current was reduced to the end-of-charge current of 100 mA (50 mA per battery) (third step).
- the battery pack was discharged at 1 C and the discharge end voltage was 7.5 V (2.5 V per battery).
- the charging / discharging process which made the above 1 cycle of charging / discharging was repeated 300 cycles.
- Example 9 Using the BMU cycle count function of the battery pack, the charge current of the first step was corrected for each cycle according to the battery deterioration rate, for example, the discharge capacity reduction rate.
- the reduction rate of the discharge capacity in Example 8 is about 0.1% ( ⁇ (100 ⁇ 68) ⁇ 300), and this reduction rate was adopted here. More specifically, the charging current of the first step in the nth cycle (n is an integer of 2 or more) was calculated by multiplying 0.998 by the (n-1) th cycle. Except for the above, 300 cycles of charge / discharge treatment were performed in the same manner as in Example 8.
- the ninth and tenth embodiments, in which the charging current in the first step is reduced according to the reduction rate of the discharge capacity, are 300 cycles than the eighth embodiment in which the charging current in the first step is constant regardless of the reduction in the discharge capacity. Eye charging time is longer. In addition, the capacity retention rate of Example 8 is slightly worse than that of Examples 9 and 10. As a result, it has been confirmed that by reducing the charging current as the number of cycles increases, the charging time can be shortened more effectively and the deterioration of cycle characteristics can be suppressed.
- the lithium ion secondary battery employing the charging method and charging / discharging method of the present invention is suitably used as a power source for electronic devices such as portable devices and information devices.
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Abstract
Description
前記封口板が、前記正極または前記負極の外部端子、及び前記正極または前記負極と電気的に接続される内部端子を有するとともに、前記内部端子と前記外部端子とが電気的に接続され、かつその間の電気抵抗が0.1~2mΩであり、
(i)充電電圧が充電終止電圧Ecsfに達するまで、充電電流をそれぞれ一定に設定して前記二次電池を充電する2以上の定電流充電ステップを実行し、
(ii)充電電圧が前記充電終止電圧Ecsfに達すると、前記充電終止電圧Ecsfで、充電電流が所定電流に低下するまで前記二次電池を充電する定電圧充電ステップを実行することを含み、
前記2以上の定電流充電ステップが、
(a)充電電圧が、目標電圧Ecs(1)、ただし、Ecs(1)<Ecsf、に達するまで、1~5Cの電流Ic(1)で前記二次電池を定電流充電し、
(b)充電電圧が前記目標電圧Ecs(1)に達すると、前記目標電圧Ecs(1)よりも大きい目標電圧Ecs(k)、ただし、Ecs(k)≦Ecsf、に達するまで、電流Ic(k)、ただし、Ic(k)<Ic(1)、で前記二次電池を定電流充電することを含む、リチウムイオン二次電池の充電方法に関する。
前記封口板が、前記正極または前記負極の外部端子、及び前記正極または前記負極と電気的に接続される内部端子を有するとともに、前記内部端子と前記外部端子とが電気的に接続され、かつその間の電気抵抗が0.1~2mΩであり、
前記制御部が、
(i)充電電圧が充電終止電圧Ecsfに達するまで、充電電流をそれぞれ一定に設定して前記二次電池を充電する2以上の定電流充電ステップを実行し、
(ii)充電電圧が前記充電終止電圧Ecsfに達すると、前記充電終止電圧Ecsfで、充電電流が所定電流に低下するまで前記二次電池を充電する定電圧充電ステップを実行するとともに、
前記2以上の定電流充電ステップが、
(a)充電電圧が、目標電圧Ecs(1)、ただし、Ecs(1)<Ecsf、に達するまで、1~5Cの電流Ic(1)で前記二次電池を定電流充電し、
(b)充電電圧が前記目標電圧Ecs(1)に達すると、前記目標電圧Ecs(1)よりも大きい目標電圧Ecs(k)、ただし、Ecs(k)≦Ecsf、に達するまで、電流Ic(k)、ただし、Ic(k)<Ic(1)、で前記二次電池を定電流充電することを含む、電池パックに関する。
(実施形態1)
図1に、本発明の実施形態1に係るリチウムイオン二次電池の充電方法が適用される、電池パックを機能ブロック図により示す。
正極活物質としてのLiNi0.8Co0.15Al0.05O2の100重量部と、結着剤としてのPVDFの1.7重量部と、導電材としてのアセチレンブラックの2.5重量部と、適量のN-メチル-2-ピロリドンとを、双腕式練合機にて攪拌し、正極ペーストを得た。
負極活物質としてのグラファイト100重量部と、結着剤としてのPVDF0.6重量部と、増粘剤としてのカルボキシメチルセルロース1重量部と、適量の水とを、双腕式練合機にて攪拌し、負極ペーストを得た。この負極ペーストを厚み8μmの銅箔からなる負極集電体の両面に塗布し、乾燥して、負極集電体の両面に負極活物質層を形成した。このようにして、プレート状ないしはシート状の負極を得た。その後、この負極を圧延及び裁断して、帯状の負極(厚み0.130mm、幅58.5mm、長さ800mm)を得た。
ECと、MECと、DMCとを体積比1:1:8の割合で混合した非水溶媒に、LiPF6を1mol/Lの濃度で溶解して非水電解液を調製した。
上記で得られた正極及び負極と、両電極を隔離するセパレータとを渦巻き状に巻回して電極群を構成した。セパレータには、厚み20μmのポリプロピレン製の微多孔膜を用いた。この電極群をケース(直径:18mm、高さ:65mm)内に挿入した。このとき、電極群の上部及び下部にそれぞれ絶縁部材を配した。上記で得られた非水電解液をケース内に注入した。
上述の試験用のリチウムイオン二次電池の中で、組立封口板の、底板と端子板との間の電気抵抗が1mΩであるものを使用した。そのリチウムイオン二次電池を、充電電圧が3.8V(Ecs(1))に達するまで、2Cの電流(Ic(1))で、定電流充電した(第1ステップ)。充電電圧が3.8Vに達した後、4.2V(Ecsf)に達するまでの間、1C(Icf)の充電電流で、定電流充電した(第2ステップ)。充電電圧が4.2Vに達した後は、その電圧で、充電終止電流を50mAに設定して、二次電池を定電圧充電した(第3ステップ)。
第1ステップで、Ecs(1)を4Vとしたこと以外は、実施例1と同様にして、300サイクルの充放電処理を実行した。
第1ステップで、Ic(1)を3Cとしたこと以外は、実施例1と同様にして、300サイクルの充放電処理を実行した。
第1ステップで、Ic(1)を5Cとしたこと以外は、実施例1と同様にして、300サイクルの充放電処理を実行した。
第1ステップで、Ic(1)を5Cとし、Ecs(1)を4Vとしたこと以外は、実施例1と同様にして、300サイクルの充放電処理を実行した。
上述の試験用のリチウムイオン二次電池の中で、組立封口板の電気抵抗が1.5mΩであるものを使用し、第1ステップで、Ic(1)を5Cとし、Ecs(1)を4Vとしたこと以外は、実施例1と同様にして、300サイクルの充放電処理を実行した。
上述の試験用のリチウムイオン二次電池の中で、組立封口板の電気抵抗が2mΩであるものを使用し、第1ステップで、Ic(1)を5Cとし、Ecs(1)を4Vとしたこと以外は、実施例1と同様にして、300サイクルの充放電処理を実行した。
上述の試験用のリチウムイオン二次電池の中で、組立封口板の、底板と端子板との間の電気抵抗が1mΩであるものを使用した。そのリチウムイオン二次電池を、1Cの充電電流で、充電電圧が4.2Vの充電終止電圧に達するまで定電流充電した。充電電圧が4.2Vに達した後は、その電圧で、充電電流が50mAの充電終止電流に低下するまで定電圧充電した。
定電流充電で、充電電流を5Cとしたこと以外は、比較例1と同様にして、300サイクルの充放電処理を実行した。
上述の試験用のリチウムイオン二次電池の中で、組立封口板の、底板と端子板との間の電気抵抗が2.5mΩであるものを使用した。そのリチウムイオン二次電池を、充電電圧が4V(Ecs(1))に達するまで、5Cの電流(Ic(1))で、定電流充電した(第1ステップ)。充電電圧が4Vに達した後、4.2V(Ecsf)に達するまでの間、1C(Icf)の充電電流で、定電流充電した(第2ステップ)。充電電圧が4.2Vに達した後は、その電圧で、充電終止電流を50mAに設定して、二次電池を定電圧充電した(第3ステップ)。
上述の試験用のリチウムイオン二次電池の中で、組立封口板の電気抵抗が12mΩであるものを使用したこと以外は、比較例3と同様にして、300サイクルの充放電処理を実行した。
上記のようにして作製した6個の試験体を2並列×3直列で電気的に接続して、電池群を作製した。そして、その電池群にBMU(電池管理ユニット)を備えさせることで電池パックを作製した。
上記電池パックのBMUのサイクルカウント機能を利用し、1サイクル毎に第1ステップの充電電流を、電池の劣化割合、例えば放電容量が低下する割合に応じて補正した。実施例8における放電容量の低下割合は、約0.1%(≒(100-68)÷300)であり、ここではこの低下割合を採用した。より具体的には、nサイクル目(nは2以上の整数)の第1ステップの充電電流を、(n―1)サイクル目のそれに0.998を乗じることで算出した。上記以外は、実施例8と同様にして、300サイクルの充放電処理を実行した。
実施例8における放電容量の低下割合(0.2%)に基づいて、50サイクル毎に第1ステップの充電電流を180mA(電池1個あたり90(=1800×0.001×50)mA)ずつ低減した。上記以外は、実施例8と同様にして、300サイクルの充放電処理を実行した。
以上の結果、サイクル数の増大とともに充電電流を低減することにより、より効果的に充電時間を短縮し得るとともに、サイクル特性の低下を抑えられることが確かめられた。
12 二次電池
16 電圧検出部
17 電流検出部
18 制御部
34 組立封口板
Claims (10)
- 正極、負極、前記正極及び前記負極の間に介在されるセパレータ並びに非水電解質を含む発電要素と、前記発電要素を収容する、開口を有するケースと、前記ケースの開口を封口する封口板と、を具備するリチウムイオン二次電池の充電方法であって、
前記封口板が、前記正極または前記負極の外部端子、及び前記正極または前記負極と電気的に接続される内部端子を有するとともに、前記内部端子と前記外部端子とが電気的に接続され、かつその間の電気抵抗が0.1~2mΩであり、
(i)充電電圧が充電終止電圧Ecsfに達するまで、充電電流をそれぞれ一定に設定して前記二次電池を充電する2以上の定電流充電ステップを実行し、
(ii)充電電圧が前記充電終止電圧Ecsfに達すると、前記充電終止電圧Ecsfで、充電電流が所定電流に低下するまで前記二次電池を充電する定電圧充電ステップを実行することを含み、
前記2以上の定電流充電ステップが、
(a)充電電圧が、目標電圧Ecs(1)、ただし、Ecs(1)<Ecsf、に達するまで、1~5Cの電流Ic(1)で前記二次電池を定電流充電し、
(b)充電電圧が前記目標電圧Ecs(1)に達すると、前記目標電圧Ecs(1)よりも大きい目標電圧Ecs(k)、ただし、Ecs(k)≦Ecsf、に達するまで、電流Ic(k)、ただし、Ic(k)<Ic(1)、で前記二次電池を定電流充電することを含む、リチウムイオン二次電池の充電方法。 - 前記電流Ic(k)のIc(1)に対する比が、0.1~0.7である、請求項1記載のリチウムイオン二次電池の充電方法。
- 前記目標電圧Ecs(k)とEcs(1)との差:ΔVが、0.05~0.2Vである、請求項1または2記載のリチウムイオン二次電池の充電方法。
- 前記正極が、一般式:LiNixCoyM1-x-yO2(ただし、Mは、長周期型周期表における、2族元素、3族元素、4族元素、7族元素及び13族元素からなる群より選択される少なくとも1つの元素であり、0.3≦x<1、0<y<0.4)で表される材料を含む、請求項1~3のいずれか1項に記載のリチウムイオン二次電池の充電方法。
- 前記目標電圧Ecs(1)が、3.8~4Vである、請求項1~4のいずれか1項に記載のリチウムイオン二次電池の充電方法。
- 前記目標電圧Ecs(k)が、4~4.2Vである、請求項1~5のいずれか1項に記載のリチウムイオン二次電池の充電方法。
- 前記二次電池の使用頻度を検知し、検知された使用頻度に基づいて、前記使用頻度が高くなるに伴い前記電流Ic(1)が減少するように、前記電流Ic(1)を補正する、請求項1~5のいずれか1項に記載のリチウムイオン二次電池の充電方法。
- 正極、負極、前記正極及び前記負極の間に介在されるセパレータ並びに非水電解質を含む発電要素と、前記発電要素を収容する、開口を有するケースと、前記ケースの開口を封口する封口板とを有する、少なくとも1つのリチウムイオン二次電池と、前記リチウムイオン二次電池の充電を制御する制御部と、を備えた電池パックであって、
前記封口板が、前記正極または前記負極の外部端子、及び前記正極または前記負極と電気的に接続される内部端子を有するとともに、前記内部端子と前記外部端子とが電気的に接続され、かつその間の電気抵抗が0.1~2mΩであり、
前記制御部が、
(i)充電電圧が充電終止電圧Ecsfに達するまで、充電電流をそれぞれ一定に設定して前記二次電池を充電する2以上の定電流充電ステップを実行し、
(ii)充電電圧が前記充電終止電圧Ecsfに達すると、前記充電終止電圧Ecsfで、充電電流が所定電流に低下するまで前記二次電池を充電する定電圧充電ステップを実行するとともに、
前記2以上の定電流充電ステップが、
(a)充電電圧が、目標電圧Ecs(1)、ただし、Ecs(1)<Ecsf、に達するまで、1~5Cの電流Ic(1)で前記二次電池を定電流充電し、
(b)充電電圧が前記目標電圧Ecs(1)に達すると、前記目標電圧Ecs(1)よりも大きい目標電圧Ecs(k)、ただし、Ecs(k)≦Ecsf、に達するまで、電流Ic(k)、ただし、Ic(k)<Ic(1)、で前記二次電池を定電流充電することを含む、電池パック。 - 前記二次電池の充電回数を計数する計数器を備え、前記制御部が、前記充電回数に基づいて、前記充電回数が多くなるに伴い前記電流Ic(1)が減少するように、前記電流Ic(1)を補正する、請求項8記載の電池パック。
- 前記内部端子と前記外部端子との間にヒューズが介在される、請求項8または9記載の電池パック。
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US20110316487A1 (en) | 2011-12-29 |
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