Secondary battery control device, secondary battery system, and method for recovering capacity of secondary battery

Abstract

To enable appropriately restoring a secondary battery capacity.SOLUTION: A control device 500 for a secondary battery 510, which includes a plurality of battery cells 10, includes: an operation mode selection unit 420 which selects, as an operation mode, either a first operation mode Mn or a second operation mode Mr; a first discharge control unit 410 which, when the operation mode selection unit 420 selects the first operation mode Mn, stops the discharge of the secondary battery 510 when either one of terminal voltages among the plurality of the battery cells 10 becomes lower than a first voltage; and a second discharge control unit 412 which, when the operation mode selection unit 420 selects the second operation mode Mr, applies a discharge current to the secondary battery 510 in a manner that a terminal voltage of a battery cell among the plurality of battery cells 10 which satisfies a predetermined deterioration condition becomes lower than a first voltage Vlow, and each terminal voltage of the other battery cells 10 becomes the first voltage Vlow or higher.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a secondary battery control device, a secondary battery system, and a capacity recovery method for a secondary battery. [Background technology]

[0002] As background art in this technical field, the abstract of the following Patent Document 1 states: "The ECU 960 controls the PCU 920 to execute capacity recovery control for recovering the capacity of the battery pack 10. The capacity recovery control includes a discharge mode and a capacity recovery mode. In the discharge mode, the ECU 960 discharges the battery pack 10 to a predetermined over-discharge region. In the capacity recovery mode, the ECU 960 repeatedly executes, in the over-discharge region, a voltage increase of the lithium ion secondary battery by stopping discharge, and a pulse discharge that discharges the lithium ion secondary battery while oscillating the discharge current." Furthermore, paragraph 0080 of the specification of the following Patent Document 2 states, "As explained above, the present invention makes it possible to know the state of the charge / discharge curve of the entire positive electrode and the charge / discharge curve of the entire negative electrode inside the secondary battery non-destructively. This makes it possible to identify the cause of battery deterioration non-destructively and to determine the lifespan with high accuracy. Furthermore, according to the present invention, by applying the results of the reproduction calculation, it is also possible to determine the appropriate usage range of a deteriorated battery with high accuracy and to obtain the amount of decrease in charge / discharge reaction species non-destructively." The descriptions in these documents are included as part of the specification of this application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-106333 A [Patent Document 2] Patent No. 4884404 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned technology, there is a demand for a method for more appropriately restoring the capacity of a secondary battery. The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a secondary battery control device, a secondary battery system, and a capacity recovery method for a secondary battery that can appropriately recover the capacity of a secondary battery. [Means for solving the problem]

[0005] In order to solve the above problems, the control device for a secondary battery of the present invention is a control device for a secondary battery having a plurality of battery cells, and is characterized in comprising: an operation mode selection unit that selects either a first operation mode or a second operation mode as an operation mode; a first discharge control unit that, when the operation mode selection unit selects the first operation mode, stops discharging the secondary battery when the terminal voltage of any of the plurality of battery cells becomes less than a first voltage; and, when the operation mode selection unit selects the second operation mode, applies a discharge current to the secondary battery so that the terminal voltage of any of the plurality of battery cells that satisfies a predetermined deterioration condition becomes less than the first voltage and the terminal voltage of the other battery cells is equal to or greater than the first voltage. Effect of the Invention

[0006] According to the present invention, the capacity of a secondary battery can be appropriately restored. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic cross-sectional view of a bipolar battery cell. [Diagram 2] FIG. 2 is a schematic side view of the electricity storage element. [Diagram 3] FIG. 2 is a schematic block diagram showing a configuration of a battery module. [Figure 4] FIG. 2 is a schematic block diagram showing the configuration of a battery pack. [Diagram 5] FIG. 2 is a block diagram conceptually illustrating an example of a control device. [Figure 6]FIG. 2 is a block diagram of a computer included in the control unit. [Figure 7] FIG. 4 is a block diagram showing the functions of a control unit. [Figure 8] FIG. 4 is a diagram showing the discharge characteristics of a battery cell. [Figure 9] FIG. 4 is a graph showing the capacity recovery rate and the amount of change in positive electrode utilization rate in the first example and the comparative example. [Figure 10] FIG. 11 is a graph showing the capacity recovery rate and the amount of change in positive electrode utilization rate in the second example and the comparative example. [Figure 11] FIG. 13 is a graph showing the capacity recovery rate and the amount of change in positive electrode utilization rate in a third example and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Outline of the embodiment] Lithium ion batteries are a type of non-aqueous electrolyte secondary battery, and because of their high energy density, they are used as batteries for portable devices and, in recent years, electric vehicles. However, it is known that lithium ion batteries deteriorate with use, resulting in a decrease in battery capacity. In lithium-ion batteries, lithium metal oxide is generally used as the active material for the positive electrode, and carbon materials such as graphite are generally used as the active material for the negative electrode. The positive and negative electrodes of lithium-ion batteries are formed by adding a binder, a conductive agent, etc. to a group of minute particles of the active material to form a slurry, which is then applied to a metal foil. In a lithium-ion battery, lithium ions released from the positive electrode active material are absorbed into the negative electrode active material during charging, and lithium ions absorbed into the negative electrode active material are released and absorbed into the positive electrode active material during discharging. In this way, lithium ions move between the electrodes, causing a current to flow between the electrodes of an external circuit.

[0009] In these lithium-ion batteries, (1) Electrical isolation of the positive electrode active material, (2) Electrical isolation of the negative electrode active material, and (3) Fixation of lithium ions moving between electrodes This reduces the capacity. The above factor (3) occurs when lithium ions are solidified as a film on the surface of the negative electrode due to the decomposition of the electrolyte, or when lithium ions are bound within the negative electrode. Of these, the capacity loss caused by lithium ions being bound within the negative electrode can be restored by electrochemical treatment. For example, by raising the potential of the negative electrode above the normal operating range, the lithium ions bound to the negative electrode are released, and the capacity is restored. This is equivalent to over-discharging the battery, and means that the state of charge (SOC) of the battery, which is determined by the operating voltage range of the battery, is reduced below 0%.

[0010] However, over-discharging a secondary battery that is not seriously degraded may promote material degradation of the positive and negative electrodes and decomposition of the electrolyte, and may actually accelerate the degradation of the secondary battery. When a secondary battery pack is composed of one cell, the over-discharge conditions can be set according to the degradation state of the cell. However, when a secondary battery pack is composed of multiple cells connected in series or parallel, cells with different degrees of degradation are mixed, so that the over-discharge conditions may accelerate the degradation of cells that are not seriously degraded. Note that a cell is the smallest constituent unit of a secondary battery pack, and refers to a secondary battery that has a positive electrode, a negative electrode, and an electrolyte.

[0011] It is believed that a technology that applies the contents of the above-mentioned Patent Document 1 can provide a capacity recovery method that can effectively recover the capacity of a lithium-ion secondary battery in a short time. That is, it is believed that after discharging a lithium-ion secondary battery to an overdischarge region, it is possible to repeatedly perform a voltage increase by stopping the discharge and a pulse discharge in which the battery is discharged while oscillating the discharge current. As a result, it is believed that it is possible to shorten the time required for capacity recovery.

[0012] However, there is room for improvement in the method of recovering the capacity of a battery by pulse discharge in the overdischarge region as described above. For example, when a lithium-ion secondary battery pack is composed of multiple cells connected in series or parallel, applying a pulse discharge to all of the cells may accelerate the deterioration of cells that are not seriously deteriorated. Therefore, the embodiment described below solves the above-mentioned problem by selectively restoring the capacity of a cell that has deteriorated significantly in a secondary battery pack in which a plurality of cells are connected.

[0013] [Battery cell structure] First, with reference to Figs. 1 and 2, a structural example of a bipolar battery cell applicable to the embodiment will be described. FIG. 1 is a schematic cross-sectional view of a bipolar battery cell 10. In Fig. 1, a battery cell 10 is a lithium-ion battery cell, and includes an electricity storage element 1, a positive electrode terminal 2, a negative electrode terminal 3, and an exterior material 6. A separator 5 is included in the electricity storage element 1. The exterior material 6 is made of a laminate film or a similar material. The shape of the battery cell 10 is not limited to a rectangular shape as shown in Fig. 1, and may be a cylindrical shape (not shown).

[0014] FIG. 2 is a schematic side view of the electricity storage element 1. As shown in FIG. As shown in FIG. 2, in the electric storage element 1, a plurality of positive electrodes 12 and a plurality of negative electrodes 13 are alternately stacked with a separator 5 interposed therebetween. The electric storage element 1 shown in FIG. 1 corresponds to the area where the positive electrodes 12 and the negative electrodes 13 appear to overlap. The structure of the electric storage element 1 is not limited to the stacked type as shown in FIG. 2. That is, although not shown, the electric storage element 1 may be a wound type fabricated by stacking the positive electrodes 12 and the negative electrodes 13 so as to face each other with the separator 5 therebetween and then winding the stack. The electric storage element 1 further contains an electrolyte (not shown), and the electrolyte is impregnated into the micropores of the positive electrodes 12, the negative electrodes 13, the separator 5, and the like. For example, polypropylene can be used as the separator 5. However, in addition to polypropylene, a microporous film or nonwoven fabric made of polyolefin such as polyethylene can also be used as the separator 5.

[0015] The positive electrode 12 and the negative electrode 13 are each made by applying a mixture of an appropriate electrode active material, a conductive agent, a binder, etc., to a current collector foil of an appropriate metal. Metal tabs are connected to the current collector foils of the positive electrode 12 and the negative electrode 13. The exterior material 6 is sealed so that only the tabs are exposed to the outside of the exterior material 6. As a result, the tabs become the positive electrode terminal 2 and the negative electrode terminal 3 in FIG. 1. Hereinafter, the potentials of the positive electrode 12 and the negative electrode 13 are referred to as the positive electrode potential Ep and the negative electrode potential En. The difference between the two, i.e., "Ep-En", is the voltage between the positive electrode terminal 2 and the negative electrode terminal 3, and this is referred to as the cell voltage V.

[0016] The current collector foil of the positive electrode 12 may be made of aluminum foil having a thickness of 10 to 100 μm, aluminum perforated foil having a thickness of 10 to 100 μm and a pore size of 0.1 to 10 mm, expanded metal, foam metal plate, or the like. In addition to aluminum, stainless steel, titanium, or the like may also be used as the material of the current collector foil. In this embodiment, any current collector can be used without being limited by the material, shape, manufacturing method, or the like.

[0017] The electrode active material of the positive electrode 12 preferably contains a reactive species therein. The reactive species of a lithium ion battery is lithium ions. In this case, the electrode active material of the positive electrode 12 contains a lithium-containing compound capable of reversibly inserting and detaching lithium ions. The type of electrode active material of the positive electrode 12 is not particularly limited, and examples thereof include lithium transition metal phosphates such as lithium cobalt oxide, lithium manganese-substituted cobalt oxide, lithium manganate, lithium nickel oxide, and olivine-type lithium iron phosphate; Li w Ni x Co y Mn z O 2 (wherein w, x, y, and z are 0 or positive values). The electrode active material of the positive electrode 12 may contain one or more of the above materials.

[0018] The current collector foil of the negative electrode 13 may be a copper foil having a thickness of 10 to 100 μm, a perforated copper foil having a thickness of 10 to 100 μm and a pore size of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. The material of the current collector foil may be, other than copper, stainless steel, titanium, or the like. In this embodiment, any current collector may be used without being limited by the material, shape, manufacturing method, or the like.

[0019] The electrode active material of the negative electrode 13 includes a material capable of reversibly inserting and detaching lithium ions. The type of electrode active material of the negative electrode 13 is not particularly limited, but may be, for example, natural graphite, a composite carbonaceous material in which a coating is formed on natural graphite by a dry CVD method or a wet spray method, artificial graphite produced by firing a resin material such as epoxy or phenol or a pitch-based material obtained from petroleum or coal, silicon (Si), graphite mixed with silicon, a non-graphitizable carbon material, lithium titanate Li 4 Ti 5 O 12 , niobium titanium oxide TiNb 2 O 7 The negative electrode active material may contain one or more of the above materials.

[0020] An electrolyte is impregnated in the electricity storage element 1. The electrolyte is not particularly limited, but in the case of a lithium ion battery, for example, an aprotic organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), or ethyl propyl carbonate (EPC) can be used.

[0021] The electrolyte is a mixture of two or more of these organic compounds in a solvent, and is made by adding lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium iodide, lithium chloride, lithium bromide, LiB[OCOCF 3 ] 4 , LiB[OCOCF 2 CF 3 ] 4 , LiPF 4 (CF 3 ) 2 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 CF 2 CF 3 ) 2 or a mixture of two or more of these lithium salts may be dissolved in the lithium salt.

[0022] A solid electrolyte may be used instead of the electrolytic solution. The solid electrolyte is not particularly limited, but examples thereof include ion-conductive polymers such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide. When such a solid polymer electrolyte is used, the separator 5 can be omitted.

[0023] [Configuration of the embodiment] FIG. 3 is a schematic block diagram showing the configuration of a battery module (basic battery unit) 100 applied to this embodiment. 3, a battery module 100 includes three battery cells 10-1, 10-2, and 10-3 connected in series, three voltage sensors 16, and a balancing circuit 20. Each of the three battery cells 10-1 to 10-3 is equivalent to the battery cell 10 shown in FIG. 1, and hereinafter the battery cells 10-1 to 10-3 may be collectively referred to as "battery cell 10." The three voltage sensors 16 output measurement results of cell voltages V1, V2, and V3 (terminal voltages) of these battery cells 10-1 to 10-3.

[0024] The balancing circuit 20 includes three switches 22 and three resistors 24 connected in series to the three switches 22. The series circuits of the switches 22 and the resistors 24 are connected in parallel to the battery cells 10-1 to 10-3, respectively. The battery module 100 outputs the measurement results of the cell voltages V1 to V3 to the control device 500.

[0025] Moreover, the on / off state of each switch 22 is controlled based on control signals SD1, SD2, SD3 supplied from the control device 500. The control device 500 outputs the control signals SD1, SD2, SD3 based on the measurement results of the cell voltages V1 to V3 so as to reduce the difference between the cell voltages V1 to V3, thereby discharging the battery cell 10 with the higher voltage.

[0026] In the following description, a "battery cell" may be simply referred to as a "cell," and a "battery module" may be simply referred to as a "module." In the example shown in Fig. 3, one battery module 100 includes three battery cells 10, but the number of battery cells 10 included in one battery module 100 may be any number greater than or equal to one.

[0027] 3, for the sake of simplicity, a passive balancing circuit including a switch 22 and a resistor 24 is shown as the balancing circuit 20. However, an active balancing circuit (not shown) may be used as the balancing circuit 20. That is, a balancing circuit may be used that charges a cell with a low cell voltage with the charge of a cell with a high cell voltage.

[0028] FIG. 4 is a schematic block diagram showing the configuration of a battery pack 510 applied to this embodiment. 4, battery pack 510 includes positive terminal 502, negative terminal 503, three battery modules 100-1, 100-2, and 100-3, and three switches 110. Battery modules 100-1 to 100-3 are each equivalent to battery module 100 shown in Fig. 3. Thus, battery modules 100-1 to 100-3 may be collectively referred to as "battery module 100."

[0029] The on / off state of each switch 110 is set based on a command supplied from the control device 500. If all the switches 110 are in the on state, the battery modules 100-1 to 100-3 are connected in parallel between the positive terminal 502 and the negative terminal 503 of the battery pack 510. The three battery cells 10 included in each of the three battery modules 100-1 to 100-3 are referred to as battery cells 10-11, 10-12, 10-13, 10-21, 10-22, 10-23, 10-31, 10-32, and 10-33.

[0030] The battery pack 510 notifies the control device 500 of the measurement results of the cell voltages V11, V12, V13, V21, V22, V23, V31, V32, and V33 (terminal voltages) of these battery cells. As described above, the control device 500 also controls the on / off states of the multiple switches 110. This allows the control device 500 to control the flow of current depending on the degree of deterioration of each module 100.

[0031] However, the switch 110 is not an essential component and can be omitted. That is, the battery modules 100-1 to 100-3 may be connected in parallel between the positive terminal 502 and the negative terminal 503. By omitting the switch 110, the cost can be reduced, and the power loss due to the on-resistance of the switch 110 can also be reduced. In the illustrated example, the battery pack 510 includes three battery modules 100-1 to 100-3, but the number of battery modules 100 included in the battery pack 510 is not particularly limited. For example, the battery pack 510 may include only one module 100. The battery pack 510 may include a voltage sensor and a current sensor that measure the voltage and current of each of the battery modules 100-1 to 100-3, and may include a thermometer that measures the internal temperature of the battery pack 510.

[0032] FIG. 5 is a block diagram showing the configuration of the secondary battery system SY according to the first embodiment. 5, the secondary battery system SY includes a battery pack 510 (secondary battery) and a control device 500 (control device for secondary battery). The battery pack 510 is connected to the control device 500 via a positive terminal 502 and a negative terminal 503.

[0033] The control device 500 includes an ammeter 551, a voltmeter 552, a variable resistor 553, a power converter 554, switches 560, 562, and 564, and a control unit 570. The power converter 554 converts DC power discharged by the battery pack 510 into AC power and supplies it to the power system 610. The power converter 554 also converts AC power supplied from the power system 610 into DC power to charge the battery pack 510. Measurement results such as cell voltages V11 to V33 (see FIG. 4) in the battery pack 510 are supplied to the control unit 570. Furthermore, the control unit 570 is also supplied with the measurement results of the ammeter 551 and the voltmeter 552. These measurement results are the current value of the charge / discharge current flowing through the battery pack 510 and the battery voltage Ev.

[0034] Based on the various input data, the control unit 570 outputs control signals to the switches 560, 562, and 564, the variable resistor 553, and the power converter 554. The control unit 570 also outputs various image data to an external display 600. Note that the configuration of the control device 500 is not limited to that shown in Fig. 5, and various circuit configurations that can control the input current to the battery pack 510 based on an input signal from the battery pack 510 can be adopted.

[0035] FIG. 6 is a block diagram of a computer 900 included in the control unit 570. 6, a computer 900 includes a CPU 901, a RAM 902, a ROM 903, a HDD 904, a communication I / F (interface) 905, an input / output I / F 906, and a media I / F 907. The communication I / F 905 is connected to an external communication circuit 915. The input / output I / F 906 is connected to an input / output device 916. The media I / F 907 reads and writes data from a recording medium 917. The ROM 903 stores a control program executed by the CPU, various data, etc. The CPU 901 executes an application program loaded into the RAM 902 to realize various functions.

[0036] FIG. 7 is a block diagram showing the functions of control unit 570, and each block in the diagram indicates a function realized by an application program or the like. That is, the control unit 570 includes a battery state acquisition unit 400, a battery state determination unit 401, a memory unit 403, a battery state calculation unit 404, a timer unit 405, a normal operation control unit 410 (first discharge control unit), a capacity recovery control unit 412 (second discharge control unit), and an operation mode selection unit 420.

[0037] The operation mode selection unit 420 selects either the normal mode Mn (first operation mode) or the capacity recovery mode Mr (second operation mode) as the operation mode of the control device 500. The operation mode may be selected by a manual operation of the user, or may be selected according to the state of the battery pack 510. The normal mode Mn is an operation mode in which the battery pack 510 is caused to perform normal charging and discharging. On the other hand, the capacity recovery mode Mr is an operation mode in which capacity recovery control is performed on some or all of the battery cells 10-11 to 10-33 (see FIG. 4).

[0038] 5, and outputs measurement values ​​such as detected voltage values ​​and current values ​​to the battery state determination unit 401. The timer unit 405 acquires various time information such as the charging time and discharging time of the battery pack 510.

[0039] The storage unit 403 stores various types of information, and supplies the stored information to the battery state determination unit 401, the battery state calculation unit 404, etc. as necessary. The stored information includes the following: A correspondence table between cell voltage V and the charge rate (or amount of electricity) of battery cell 10. - Initial capacity of 10 battery cells. Information input from the battery state determination unit 401.

[0040] The battery state determination unit 401 acquires various states of the battery pack 510 based on various measurement values ​​input from the battery state acquisition unit 400 and time information supplied from the timer unit 405. The acquired states include the amount of electricity of each battery cell 10 in the battery pack 510. The battery state determination unit 401 also stores the battery voltage Ev and the cell voltages V11 to V33 in the storage unit 403 in association with the current time. As a result, the storage unit 403 stores time-series information on the battery voltage Ev and the cell voltages V11 to V33.

[0041] The battery state determination unit 401 compares various determination values ​​input from the battery state calculation unit 404 with various control values ​​input from the storage unit 403. Then, the battery state determination unit 401 determines the state of the battery pack 510, and outputs the result to the normal operation control unit 410 and the capacity recovery control unit 412.

[0042] Battery state calculation unit 404 appropriately corrects the acquired measured values ​​and initial values, calculates physical quantities for determining the battery state, and outputs the calculated physical quantities to battery state determination unit 401. Specifically, it calculates the battery charging rate from a correspondence table between battery voltages and battery charging rates stored in storage unit 403 and the battery voltage input from battery state determination unit 401, and outputs the calculated battery state determination unit 401. It also calculates the current value and application time of a discharge pulse from the battery voltage and the initial capacity of the battery stored in storage unit 403, and outputs the calculated battery state determination unit 401.

[0043] The method of calculating the battery charging rate is not limited to the method shown here, and the battery charging rate can be calculated by any method. In addition, the configuration of control unit 570 is not limited to that shown in FIG. 7, and may be any configuration that can determine the state of battery pack 510, apply a specific discharge current to battery pack 510 for a specific period of time, and maintain the battery in an open circuit state.

[0044] [Operation of the embodiment] <Operation mode selection> In Fig. 7, the operation mode selection unit 420 selects either the normal mode Mn or the capacity recovery mode Mr as the operation mode of the control device 500 based on the user's operation. Also, the operation mode selection unit 420 can automatically select the operation mode based on the determination result of the battery state determination unit 401, regardless of the user's operation. That is, when the battery state determination unit 401 determines that "capacity recovery control is necessary", it selects the capacity recovery mode Mr, and in other cases, it selects the normal mode Mn. The battery state determination unit 401 may determine whether or not capacity recovery control is necessary based on the usage history of the battery pack 510, the current SOC of the battery pack 510, etc.

[0045] <Normal mode Mn> When the normal mode Mn is selected as the operation mode, the normal operation control unit 410 causes power to be input / output between the battery pack 510 and the power system 610 (see FIG. 5) via the power converter 554. That is, when the battery pack 510 is to be discharged, the normal operation control unit 410 causes the power converter 554 to convert the discharged DC power into AC power and supply it to the power system 610. When the battery pack 510 is to be charged, the normal operation control unit 410 causes the power converter 554 to convert the AC power supplied from the power system 610 into DC power and supply it to the battery pack 510.

[0046] In addition, in the normal mode Mn, the normal operation control unit 410 controls all of the cell voltages V11 to V33 to be lower than a predetermined lower limit voltage V low The discharge current of the battery pack 510 is controlled so as to prevent any of the cell voltages V11 to V33 from becoming lower limit voltage V low When the lower limit voltage V falls below the lower limit voltage V, the switch 560 (see FIG. 5) is set to the OFF state, and the discharge of the battery pack 510 is forcibly terminated. low is stored in the storage unit 403.

[0047] <Capacity Recovery Mode Mr> In the capacity recovery mode Mr, the capacity recovery control unit 412 executes the capacity recovery control. During the progress of the capacity recovery control, it is preferable to display on the display 600 a message indicating that the capacity recovery control is being executed to alert the user. The content of the capacity recovery control is not particularly limited, but may be, for example, applying a discharge pulse by a large current to the battery pack 510 and then suspending the battery pack 510 for a certain period of time.

[0048] That is, the capacity recovery control unit 412 recovers the cell capacity that has been reduced by the instantaneous drop in the cell voltage V (see FIG. 1) and the subsequent relaxation. At that time, the cell voltage V is set to the above-mentioned lower limit voltage V low A larger recovery effect can be obtained by lowering the cell voltage V to less than V lowIn order to prevent the battery system from being shut down due to the voltage falling below V, the capacity recovery control sets the lower limit voltage of the cell to V low The application and pause of the discharge pulse may be performed once each, or may be performed repeatedly.

[0049] (Control based on voltage conditions) 3 and 4, when a battery pack 510 includes a battery module 100 in which a plurality of battery cells 10 are connected in series, a discharge current is applied uniformly to each battery cell 10 in the battery module 100. Therefore, when a large-current discharge pulse is applied to the battery pack 510 by capacity recovery control, the cell voltage V is also lowered for battery cells 10 with a small capacity drop, i.e., battery cells 10 with a small degree of degradation. This may actually accelerate degradation of battery cells 10 with a small degree of degradation.

[0050] In order to avoid such a situation, the capacity recovery control unit 412 of the present embodiment controls the cell voltage V of the battery cell 10 with a high degree of deterioration to be lower than the lower limit voltage V low The cell voltage V of the battery cell 10 that is lower than the lower limit voltage V low In other words, the capacity recovery control unit 412 controls the current value of the discharge pulse so that the voltage of the battery cell 10 that is most deteriorated among the multiple battery cells 10 is equal to or higher than the discharge end voltage (V low ) and the terminal voltage of the other battery cells 10 is less than the discharge cut-off voltage (V low ) or more. Generally, a battery cell 10 that is significantly deteriorated has a smaller discharge capacity and a larger internal resistance than other battery cells 10, and therefore experiences a larger voltage drop even when the same discharge current value is applied.

[0051] Therefore, the cell voltage V of the battery cell 10 with the highest degree of deterioration is V x Let the cell voltage V of the battery cell 10 with the least deterioration be V y Then, there exists a combination of discharge current value and discharge time that satisfies the following formula (1). V x <V low <V y …Formula (1) The capacity recovery control unit 412 of this embodiment controls the current value and application time of the pulse discharge so as to satisfy the condition of formula (1).

[0052] The battery state calculation unit 404 executes a step of judging the degree of deterioration of each battery cell 10 (first step of evaluating the deterioration state). Here, the criteria for judging the degree of deterioration are not particularly limited, but for example, the battery pack 510 can be put into an open circuit state at a predetermined charging rate, and the degree of deterioration can be judged based on the cell voltages V11 to V33 at that time. In other words, when the measured cell voltages V11 to V33 are equal to or lower than a predetermined value V dg (not shown) or less, it can be determined that the degree of deterioration is large (in other words, the degree of deterioration satisfies the "predetermined deterioration condition"); otherwise, it can be determined that the degree of deterioration is small. dg may be determined in advance and stored in the storage unit 403, or may be calculated by the battery state calculation unit 404 based on each of the cell voltages V11 to V33. In the following description, a "battery cell 10 with a large degree of degradation" may be referred to as a "deterioration progressing cell".

[0053] (Partial discharge control by balancing circuit 20) As shown in FIG. 4, a battery module 100 such as a lithium ion secondary battery generally includes a balancing circuit 20. Therefore, the capacity recovery control unit 412 of this embodiment can perform partial discharge control only on some of the battery cells 10 by using the balancing circuit 20 before uniformly applying a discharge current to each battery cell 10 included in the battery module 100. This makes it possible to expand the voltage condition shown in formula (1).

[0054] That is, when a user's instruction to "execute partial discharge control" is input to the control unit 570, the capacity recovery control unit 412 closes the switch 22 of the degradation-increasing cell before applying a discharge pulse, thereby selecting and discharging only the degradation-increasing cells, thereby lowering the charge rate of these cells. After this partial discharge control is completed, the capacity recovery control unit 412 opens the switch 22, and applies a discharge current uniformly to each battery cell 10 of the battery module 100.

[0055] By performing this partial discharge control, the cell voltage V of the degradation-progressing cell can be lowered in advance to a greater extent than the other cell voltages V, making it possible to satisfy the voltage condition of equation (1) over a wide range of discharge pulse conditions. Note that partial discharge control is not limited to the passive balancing circuit 20 shown in Fig. 3, and can also be achieved in an active balancing circuit (not shown).

[0056] (Selection of battery module by switch 110) As shown in Fig. 4, in the case of a battery pack 510 in which a plurality of battery modules 100 may be connected in parallel, even if a large current discharge pulse is applied to the battery pack 510, the large current is not necessarily applied to the degradation-compromising cell. Thus, when the user issues a predetermined instruction, the capacity recovery control unit 412 classifies the modules 100 into those that include degradation-compromising cells and those that do not. Then, the capacity recovery control unit 412 turns on the switch 110 only for the modules 100 that include degradation-compromising cells, and turns off the switch 110 for the other modules 100. This makes it possible to select only the modules 100 that include degradation-compromising cells and apply a discharge pulse to them.

[0057] (Positive electrode deterioration prevention treatment) The capacity recovery control section 412 can limit the discharge current value and application time of the discharge pulse not only by the voltage condition of the above-mentioned formula (1) but also by other conditions. For example, even in a deterioration-prone cell, repeated application of a discharge pulse may cause the positive electrode to be overdischarged, accelerating the deterioration of the positive electrode. To prevent this, it is preferable to control the amount of electricity applied by the discharge pulse so that the positive electrode is not overdischarged. This can be achieved by the following method.

[0058] Step #1: Obtain the charge / discharge curve of battery cell 10 First, the charge / discharge curves of the cell voltage V, the positive electrode potential Ep, and the negative electrode potential En (see FIG. 1), i.e., the characteristics of V, Ep, and En for various discharge amounts, are obtained for a prototype of the battery cell 10. Since it is necessary to destroy the battery cell 10 in order to directly measure the positive electrode potential Ep and the negative electrode potential En, the charge / discharge curves are obtained for a prototype battery cell 10 of the same type as that applied to the battery pack 510.

[0059] Step #2: Obtain the charge / discharge curve of the cell voltage V of the deteriorating cell Battery state determination unit 401 stores the relationship between the cell voltage V and the current value for the progressively deteriorating cell in memory unit 403. The charge / discharge amount is obtained by integrating the current value, and from this, battery state calculation unit 404 calculates data on the charge / discharge curve of the cell voltage V of each progressively deteriorating cell. It is desirable that the voltage on the charge / discharge curve has a value close to the open circuit voltage. Any current flow method may be used when calculating the data on the charge / discharge curve.

[0060] For example, there is a method of discharging the progressively deteriorating cell from a fully charged state to a fully discharged state, or a method of charging the progressively deteriorating cell from a fully discharged state to a fully charged state, using a small and constant current. Alternatively, there may be a method of repeatedly discharging the progressively deteriorating cell at a constant current for a fixed period of time, followed by a period of rest, and then repeating this cycle from a fully charged state to a fully discharged state. Alternatively, there may be a method of repeatedly charging the progressively deteriorating cell at a constant current for a fixed period of time, followed by a period of rest, and then repeating this cycle from a fully discharged state to a fully charged state. By using such methods, data on the relationship between the charge / discharge amount and the open circuit voltage can be obtained.

[0061] There is also a method of acquiring the current and voltage waveforms of the deteriorating cell during operation in normal mode Mn, processing them statistically, or performing regression calculation processing (reproduction calculation processing) based on an equivalent circuit, estimating the open circuit voltage, and estimating the relationship between the charge / discharge amount and the open circuit voltage. Note that, although the current application method for calculating the data of the charge / discharge curve described above was described as "discharging from a fully charged state to a fully discharged state" and "charging from a fully discharged state to a fully charged state," the current application method is not necessarily limited to discharging or charging within these ranges. It is desirable that the charge / discharge range be as wide as possible, and it is most desirable to charge / discharge within a range of 100%, but if the subsequent process can be performed smoothly, it is acceptable to charge / discharge within a range of 50% or more from a fully charged state to a fully discharged state. Furthermore, if possible, it is acceptable to use a range of less than 50%.

[0062] Step #3: Obtaining the charge / discharge curves of the positive electrode potential Ep and the negative electrode potential En of the deteriorating cell Next, the battery state calculation unit 404 constructs charge / discharge curves of the positive electrode potential Ep and negative electrode potential En of the progressively deteriorating cell by regression calculation processing (reproduction calculation processing) based on the charge / discharge curve of the prototype stored in advance in the memory unit 403 and the charge / discharge curve of the cell voltage V of the progressively deteriorating cell. The contents of this regression calculation process (reproduction calculation process) are described in the above-mentioned Patent Document 2, but an outline of it will be given below.

[0063] First, the battery state calculation unit 404 calculates the amount of positive electrode active material m p and the amount of negative electrode active material m n and the index C of the positional relationship of the positive electrode discharge curve p and the index C of the positional relationship of the negative electrode discharge curve n and stores it in the memory unit 403. Next, the battery state calculation unit 404 multiplies the discharge amount of the positive electrode 12 (see FIG. 2) by the amount of positive electrode active material m p The discharge amount of the negative electrode 13 (see FIG. 2) is multiplied by the amount of the positive electrode active material m p to obtain calculated values ​​of the positive electrode discharge curve and the negative electrode discharge curve based on the reference mass of the positive electrode 12 and the reference mass of the negative electrode 13.

[0064] FIG. 8 is a diagram showing an example of a charge / discharge curve obtained by calculation for a deterioration-progressing cell. The horizontal axis of Fig. 8 is the discharge amount Q [Ah], with a value of "0" representing a fully charged state and a negative value representing an overcharged state. The vertical axis on the left side of Fig. 8 represents the potential and voltage. The vertical axis on the right side of Fig. 8 represents the potential based on the lithium electrode. Hereinafter, the unit of potential based on the lithium electrode will be expressed as "V vs. Li / Li + " is written as ".

[0065] The calculated values ​​of the positive electrode potential Ep and the negative electrode potential En (see FIG. 1) are called the positive electrode discharge curve calculated value Epc (positive electrode potential curve) and the negative electrode discharge curve calculated value Enc (negative electrode potential curve). The difference between them (Epc-Enc) is called the battery discharge curve calculated value Vc. The battery state calculation unit 404 adjusts m p ,m n ,C p ,C n Then, the adjusted correction parameter m p ,m n ,C p ,C n Based on this, the positive electrode discharge curve calculation value Epc and the negative electrode discharge curve calculation value Enc are recalculated and updated.

[0066] The positive electrode discharge curve calculated value Epc, the negative electrode discharge curve calculated value Enc, and the battery discharge curve calculated value Vc shown in Fig. 8 are examples obtained by such a reproduction calculation process. The illustrated example shows a state in which a capacity difference occurs between the positive electrode and the negative electrode, and the discharge end of the negative electrode discharge curve calculated value Enc coincides with the discharge end of the battery discharge curve calculated value Vc.

[0067] Step #4: Calculate the charge / discharge capacity of a deteriorating cell at a given state of charge Next, the battery state calculation unit 404 calculates the charge / discharge capacity in a predetermined state of charge of the deterioration-progressing cell based on the positive electrode discharge curve calculated value Epc and the negative electrode discharge curve calculated value Enc. More specifically, p0Discharge amount Q corresponding to (first potential) p0 (first discharge amount) and a predetermined negative electrode potential V n0 Discharge amount Q corresponding to (second potential) n0 (the second discharge amount) and the difference between them (Q p0 -Q n0 ) and calculate.

[0068] Here, the negative electrode potential V n0 is the potential at the discharge end of the negative electrode discharge curve calculation value Enc, and should be set at a point where the negative electrode potential rises rapidly. In the example shown in the figure, the negative electrode potential V n0 is 0.4 [V vs. Li / Li + ]. In addition, the positive electrode potential V p0 is a potential slightly higher than the discharge end of the calculated positive electrode discharge curve Epc, and should be set to a potential before the positive electrode potential drops rapidly. In the example shown in the figure, the positive electrode potential V p0 is "0.6V vs. Li / Li + " is set.

[0069] Here, the current flowing through the pulse discharge in the deteriorating cell is (Q p0 -Q n0 ), the positive electrode will be discharged to the over-discharge region, which may accelerate the deterioration of the positive electrode. Therefore, when the remaining capacity of the most deteriorated battery cell 10 is Qm and the amount of electricity supplied by pulse discharge is Qr, the capacity recovery control unit 412 calculates the following: Qm <Qr<Q p0 -Q n0 ...Formula (2) The amount of electricity Qr supplied during the capacity recovery control is set so as to satisfy the following: This makes it possible to suppress the material deterioration of the positive electrode.

[0070] [Example] First Example Various examples and comparative examples of this embodiment will be described below, but first, a first example will be described. In this embodiment, charge and discharge were repeatedly performed on the battery module 100 shown in FIG. 3, and the capacities of the battery cells 10-1, 10-2, and 10-3 were reduced to 80%, 70%, and 80% of their initial capacities, respectively. That is, the battery cell 10-2 became the cell with the highest degree of deterioration, and the battery cells 10-1 and 10-3 became the cells with a small degree of deterioration.

[0071] In this embodiment, before the capacity recovery control, the battery module 100 was discharged at a discharge rate of 1C until the cell voltage V2 of the battery cell 10-2 reached the lower limit voltage V low . That is, discharging using the balancing circuit 20 was not performed on the individual battery cells 10. The state in which the cell voltage V2 was thus made to reach the lower limit voltage V low is called the "capacity recovery preparation state". Note that the "1C discharge rate" means the current density at which the battery capacity is discharged in one hour.

[0072] After the above-described capacity recovery preparation state was established, capacity recovery control was executed. In the capacity recovery control of this embodiment, a discharge pulse of 10 seconds at a discharge rate of 6C was applied to the battery module 100 in the capacity recovery preparation state, and then it was held in an open circuit state for 15 minutes. By this capacity recovery control, the cell voltages V1, V2, and V3 satisfy the voltage condition of Equation (1), that is, "V2 < V low < V1, V3".

[0073] FIG. 9 is a diagram showing the capacity recovery rate and the change amount of the positive electrode utilization rate of the deteriorating cells in the first embodiment and the comparative example. Here, the capacity recovery rate is the percentage of the recovered capacity with respect to the initial capacity. The positive electrode utilization rate corresponds to the amount of the positive electrode active material m p described above, and is a value normalized with m p in the initial state as 100%. A decrease in the positive electrode utilization rate means that the positive electrode has deteriorated. As shown in the figure, in the first embodiment, the capacity recovery rate of the battery cell 10-2 was 2.2%. Also, the change amounts of the positive electrode utilization rates of the battery cells 10-1, 10-2, and 10-3 were -0.8%, 0%, and -0.5%, respectively.

[0074] Next, Comparative Example #1 and Comparative Example #2 will be described. Comparative Example #1 is an example in which, in the above-described state of preparation for capacity recovery, a discharge pulse is applied at a discharge rate of 15C for 4 seconds and then held in an open-circuit state for 15 minutes. In Comparative Example #1, "V1, V2, V3 < V" low holds, and the relationship of the above-described formula (1) does not hold. As shown in FIG. 9, in Comparative Example #1, the capacity recovery rate of the battery cell 10-2 was 2.8%, and a higher capacity recovery rate than that of the first embodiment was obtained. However, in particular, the positive electrode utilization rates of the battery cells 10-1 and 10-3 have greatly decreased, and there is a problem that the deterioration of the battery cells 10-1 and 10-3, which have not deteriorated so much, is promoted.

[0075] Next, Comparative Example #2 is an example in which, in the above-described state of preparation for capacity recovery, a discharge pulse is applied at a discharge rate of 0.5C for 120 seconds and then held in an open-circuit state for 15 minutes. In Comparative Example #2, "V" low < V1, V2, V3" holds, and the relationship of the above-described formula (1) does not hold. As shown in the figure, in Comparative Example #2, the capacity recovery rate of the battery cell 10-2 was 0.4%, and the capacity recovery rate was lower than that of the first embodiment. As described above, according to the first embodiment, the capacity of the battery cell 10-2 can be effectively recovered while suppressing a decrease in the positive electrode utilization rate.

[0076] <Second Embodiment> Next, the second embodiment will be described. Also in this embodiment, as in the first embodiment, charging and discharging are repeated for the battery module 100 shown in FIG. 3, and the capacities of the battery cells 10-1, 10-2, and 10-3 are reduced to 80%, 70%, and 80% of the initial capacity, respectively. Next, partial discharge control was performed on the battery cell 10-2, which is a cell with progressing deterioration, using the balancing circuit 20. That is, the switch 22 corresponding to the battery cell 10-2 was closed, and the battery cell 10-2 was discharged to the lower limit voltage V low until.

[0077] Next, for the battery module 100, as capacity recovery control, after applying a discharge pulse at a discharge rate of 15C for 4 seconds, it was held in an open - circuit state for 15 minutes. In this embodiment, since only the battery cell 10 - 2 was discharged and then capacity recovery control was performed, in this case as well, the voltage condition of Equation (1), that is, "V2 < V low <V1, V3" is satisfied. FIG. 10 is a diagram showing the capacity recovery rate and the change amount of the positive - electrode utilization rate of the deteriorated - progression cells in the second embodiment and the comparative example. Comparative example #1 in the figure is the same as that shown in FIG. 9. According to this embodiment, a higher capacity recovery rate can be achieved compared to Comparative example #1, and the decrease in the positive - electrode utilization rate is also less. Thus, according to the second embodiment, while further suppressing the decrease in the positive - electrode utilization rate, a larger capacity recovery rate can be realized.

[0078] <Third Embodiment> Next, the third embodiment will be described. In this embodiment, the battery pack 510 shown in FIG. 4 was repeatedly charged and discharged, and the capacities of the battery modules 100 - 1, 100 - 2, and 100 - 3 were decreased to 80%, 70%, and 80% of the initial capacity, respectively. Among the nine battery cells 10 - 11 to 10 - 33 in FIG. 4, only the capacity of the battery cell 10 - 22 was decreased to 70% of the initial capacity, and the capacities of the other eight battery cells 10 were maintained at 80% of the initial capacity.

[0079] In this embodiment, the switch 22 (see FIG. 3) for the battery cell 10 - 22 was closed to lower only the battery cell 10 - 22 to the lower - limit voltage V lowPartial discharge control was performed until discharge was achieved. When the partial discharge control was completed, all of the switches 110 were closed, and as charge recovery control, a discharge pulse was applied at a discharge rate of 15C for 4 seconds and held in an open circuit state for 15 minutes. In this embodiment, since all of the switches 110 are closed, not only the control device 500 but also the battery modules 100-1 and 100-3 charge the battery module 100-2. Accordingly, the relationship of "V22 < V11, V12, V13, V31, V32, V33 < V21, V23" holds for the cell voltages of each battery cell 10. Accordingly, even if the currents flowing through the battery modules 100-1 to 100-3 are non-uniform, the voltage condition of Equation (1), i.e., "V22 < V low <(the voltage of other cells)" is satisfied.

[0080] Next, Comparative Example #3 will be described. In Comparative Example #3, partial discharge control was not performed, and the battery modules 100-1 to 100-3 were brought into a "charge recovery preparation state". That is, in each of the battery modules 100-1 to 100-3, the lowest cell voltage V of the battery cells 10 included therein was made to coincide with the lower limit voltage V low . Thereafter, all of the switches 110 were closed, and as charge recovery control, a discharge pulse was applied at a discharge rate of 15C for 4 seconds and held in an open circuit state for 15 minutes.

[0081] FIG. 11 is a diagram showing the charge recovery rate and the change amount of the positive electrode utilization rate of the deteriorated advancing cells in the third embodiment and Comparative Example #3. Note that the change amount of the positive electrode utilization rate is in module units. As shown in the figure, according to this embodiment, a larger charge recovery rate can be obtained than that of Comparative Example #3.

[0082] [Effects of the Embodiment] As described above, according to the embodiment, the secondary battery control device (500) includes an operation mode selection unit 420 that selects either the first operation mode (Mn) or the second operation mode (Mr) as an operation mode, and a control unit 422 that controls a voltage level of the secondary battery (510) when the operation mode selection unit 420 selects the first operation mode (Mn) and when the terminal voltage (V1 to V3, V11 to V33) of any of the multiple battery cells 10 included in the secondary battery (510) becomes equal to or lower than a first voltage (V low a first discharge control unit (410) that stops discharging the secondary battery (510) when the terminal voltage of one of the plurality of battery cells 10 that satisfies a predetermined deterioration condition becomes less than a first voltage (V low ) and the terminal voltage of the other battery cells 10 becomes less than the first voltage (V low and a second discharge control unit (412) that applies a discharge current to the secondary battery (510) so that the charge-discharge current becomes equal to or greater than the charge-discharge current of the secondary battery (510).

[0083] According to another aspect, the above-described embodiment is a capacity recovery method for a secondary battery (510) including a plurality of battery cells 10, the method including: a first step of evaluating a deterioration state of each of the plurality of battery cells 10; and a second step of evaluating a voltage of a battery cell 10 that is more deteriorated than a discharge end voltage (V low ) and the terminal voltage of the other battery cells 10 is less than the discharge cut-off voltage (V low and a second step of applying a discharge current to the secondary battery (510) so that the capacity of the secondary battery (510) is equal to or greater than the first step.

[0084] This makes it possible to keep the terminal voltage of the battery cells 10 that do not satisfy the deterioration conditions relatively high, and by suppressing deterioration of the battery cells 10 that do not satisfy the deterioration conditions, the capacity of the secondary battery can be appropriately restored.

[0085] In addition, the second discharge control unit (412) controls the discharge of the battery cells 10 whose terminal voltages are equal to or lower than a predetermined value (V dg ) or lower than the terminal voltage of the other battery cells, the terminal voltage of the battery cell is a first voltage (V low) and the terminal voltage of the other battery cells 10 becomes less than the first voltage (V low It is more preferable that the second discharge control unit (412) further includes a partial discharge function for selecting and discharging a battery cell 10 that satisfies a deterioration condition before applying a discharge current to the secondary battery (510) when the operation mode selection unit 420 selects the second operation mode (Mr). This makes it possible to maintain the terminal voltage of the battery cells 10 that do not satisfy the deterioration conditions at a higher level, thereby further suppressing the deterioration of these cells.

[0086] Furthermore, the secondary battery (510) comprises a basic battery unit (100) including a plurality of battery cells 10, the basic battery units (100) being connected in parallel, and further comprising a switch 110 for switching whether or not to apply current to each basic battery unit (100), and when the operation mode selection unit 420 selects the second operation mode (Mr), the second discharge control unit (412) more preferably turns on the switch 110 corresponding to the basic battery unit (100) including the battery cell 10 that satisfies the deterioration condition, and turns off the other switches 110, before applying the discharge current. This makes it possible to prevent a discharge current from being applied to a basic battery unit (100) that does not include a battery cell 10 that satisfies the deterioration condition, thereby making it possible to further suppress deterioration of the battery cells 10 included in the basic battery unit (100).

[0087] In addition, the secondary battery control device (500) acquires a positive electrode potential curve (Epc) and a negative electrode potential curve (Enc) based on the charge curve or discharge curve of the battery cell 10 that satisfies the deterioration condition, and calculates a predetermined first potential (V p0 ) corresponding to the first discharge amount (Q p0 ) and a predetermined second potential (V n0 ) corresponding to the second discharge amount (Q n0), and the second discharge control unit (412) acquires the first discharge amount (Q p0 ) and the second discharge amount (Q n0 ) and the difference (Q p0 -Q n0 It is more preferable to determine the amount of electricity Qr to be supplied to the battery cells 10 that satisfy the deterioration condition so that the amount of electricity Qr to be supplied to the battery cells 10 that satisfy the deterioration condition is less than the deterioration condition. This makes it possible to determine the amount of electricity Qr passed through the current based on the positive electrode potential curve (Epc) and the negative electrode potential curve (Enc), thereby making it possible to suppress material deterioration of the positive electrode of the battery cell 10 that satisfies the deterioration condition.

[0088] [Variations] The present invention is not limited to the above-mentioned embodiment, and various modifications are possible. The above-mentioned embodiment is exemplified to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the configurations described. In addition, other configurations may be added to the configuration of the above-mentioned embodiment, and it is also possible to replace a part of the configuration with another configuration. In addition, the control lines and information lines shown in the figure show those that are considered necessary for explanation, and do not necessarily show all the control lines and information lines necessary on the product. In reality, it may be considered that almost all the configurations are connected to each other. Possible modifications of the above-mentioned embodiment are, for example, as follows.

[0089] (1) The hardware of control unit 570 in the above embodiment can be realized by a general computer. Therefore, a program for executing the various processes described above may be stored on a storage medium or distributed via a transmission line.

[0090] (2) In the above embodiment, each of the above-mentioned processes has been described as software-based processes using a program. However, some or all of the processes may be replaced with hardware-based processes using an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), etc.

[0091] (3) The various processes executed in the above-described embodiments may be executed by a server computer via a network (not shown), and the various data stored in the above-described embodiments may also be stored in the server computer. [Explanation of symbols]

[0092] 10 Battery Cells 100 Battery module (basic battery unit) 110 Switch 404 Battery status calculation unit 410 Normal operation control unit (first discharge control unit) 412 Capacity recovery control section (second discharge control section) 420 Operation mode selection section 500 Control device (control device for secondary battery) 510 Battery pack (secondary battery) Mn Normal mode (first operating mode) Mr Capacity Recovery Mode (Second Operation Mode) Qm remaining capacity Qr Electric current SY Secondary Battery System Enc Calculated negative electrode discharge curve (negative electrode potential curve) Epc Calculated positive electrode discharge curve (positive electrode potential curve) Q n0 Discharge amount (second discharge amount) Q p0 Discharge amount (first discharge amount) V n0 Negative electrode potential (second potential) V p0 Positive electrode potential (first potential) Vlow Lower limit voltage (first voltage) V1~V3, V11~V33 Cell voltage (terminal voltage)

Claims

1. A control device for a secondary battery having a plurality of battery cells, an operation mode selection unit that selects either a first operation mode or a second operation mode as an operation mode; a first discharge control unit that stops discharging the secondary battery when a terminal voltage of any one of the plurality of battery cells becomes lower than a first voltage when the operation mode selection unit selects the first operation mode; a second discharge control unit that applies a discharge current to the secondary battery so that, when the operation mode selection unit selects the second operation mode, a terminal voltage of one of the plurality of battery cells that satisfies a predetermined deterioration condition becomes lower than the first voltage, and a terminal voltage of the other battery cells becomes equal to or higher than the first voltage. A control device for a secondary battery.

2. The second discharge control unit applies a discharge current to the secondary battery so that a terminal voltage of a battery cell among the plurality of battery cells, the terminal voltage of which is equal to or lower than a predetermined value or lower than other battery cells, becomes lower than the first voltage, and the terminal voltage of the other battery cells becomes equal to or higher than the first voltage.

2. The secondary battery control device according to claim 1,

3. The second discharge control unit is When the operation mode selection unit selects the second operation mode, the battery cell that satisfies the deterioration condition is selectively discharged before the discharge current is applied to the secondary battery.

2. The secondary battery control device according to claim 1,

4. the secondary battery includes a basic battery unit including a plurality of the battery cells, the basic battery units being connected in parallel, and further including a switch for switching whether or not a current is applied to each of the basic battery units; The second discharge control unit is When the operation mode selection unit selects the second operation mode, before applying the discharge current, the switch corresponding to the basic battery unit including the battery cell that satisfies the deterioration condition is turned on, and the other switches are turned off.

3. The secondary battery control device according to claim 1, wherein the secondary battery control device is a power supply device.

5. a battery state calculation unit that obtains a positive electrode potential curve and a negative electrode potential curve based on the charge curve or the discharge curve of the battery cell that satisfies the deterioration condition, and obtains a first discharge amount corresponding to a predetermined first potential on the positive electrode potential curve and a second discharge amount corresponding to a predetermined second potential on the negative electrode potential curve, The second discharge control unit is The amount of electricity to be supplied to the battery cell that satisfies the deterioration condition is determined so that the amount of electricity of the discharge current to be supplied exceeds the remaining capacity of the battery cell that is most deteriorated and is less than the difference between the first discharge amount and the second discharge amount.

4. The secondary battery control device according to claim 1, wherein the secondary battery control device is a power supply control device.

6. A secondary battery including a plurality of battery cells; an operation mode selection unit that selects either a first operation mode or a second operation mode as an operation mode; a first discharge control unit that stops discharging the secondary battery when a terminal voltage of any one of the plurality of battery cells becomes lower than a first voltage when the operation mode selection unit selects the first operation mode; a second discharge control unit that applies a discharge current to the secondary battery so that, when the operation mode selection unit selects the second operation mode, a terminal voltage of one of the plurality of battery cells that satisfies a predetermined deterioration condition becomes lower than the first voltage, and a terminal voltage of the other battery cells becomes equal to or higher than the first voltage. A secondary battery system comprising:

7. A capacity recovery method for a secondary battery having a plurality of battery cells, comprising: A first step of evaluating a deterioration state of each of the plurality of battery cells; a second step of applying a discharge current to the secondary battery so that the voltage of the battery cell that is most deteriorated among the plurality of battery cells becomes less than a discharge end voltage of the battery cell during normal use, and the terminal voltage of the other battery cells becomes equal to or higher than the discharge end voltage. A capacity recovery method for a secondary battery.

8. In the first step, the deterioration state of each of the battery cells is evaluated based on a terminal voltage.

8. The method for restoring capacity of a secondary battery according to claim 7.

9. In the second step, the battery cell that is more deteriorated is selectively discharged before the discharge current is applied to the secondary battery.

9. The method for restoring capacity of a secondary battery according to claim 7 or 8.

Images