Battery management device, battery management method, and control program product

Abstract

The invention relates to a battery management apparatus, a battery management method, and a control program product. A battery management device according to the present disclosure includes: a temperature detection unit configured to detect a temperature of a lithium ion secondary battery; a high-frequency signal supply unit configured to supply a high-frequency signal of 0.1 MHz or more to the lithium ion secondary battery; an impedance detection unit configured to detect a value of a real part of AC impedance from the lithium ion secondary battery to which the high-frequency signal has been supplied; a calculation unit configured to calculate an amount of Li deposition in the lithium ion secondary battery from a value of a real part of the detected AC impedance; and a control unit configured to control an allowable charging power of the lithium ion secondary battery and control an upper limit temperature of the lithium ion secondary battery based on the calculated Li deposition amount in the lithium ion secondary battery.

Description

Technical Field

[0001] This disclosure relates to a battery management device, a battery management method, and a control program. Background Technology

[0002] To prevent performance degradation in lithium-ion secondary batteries, there is a need to suppress the deposition of metallic Li (lithium) in the batteries (hereinafter referred to as Li deposition). However, methods for non-destructively detecting Li deposition in lithium-ion secondary batteries are unknown.

[0003] To address the above requirements, as disclosed in Patent Document 1, the inventors have developed a method for detecting the real part of the AC impedance of a lithium-ion secondary battery using a high-frequency signal and calculating the amount of Li deposited in the lithium-ion secondary battery based on the difference between the current value of the real part of the AC impedance and the initial value.

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2022-108602 Summary of the Invention

[0005] Since Li deposition progresses with increasing charging power, an allowable charging power is set for each type of lithium-ion secondary battery to suppress Li deposition. Note that even within the same type of product, there are variations (e.g., standard deviation σ) in the rate of Li deposition progression in lithium-ion secondary batteries. In prior art lithium-ion secondary batteries, to prevent the advancement of Li deposition, the allowable charging power is set (fixed) excessively low for each type of product, within a range of, for example, ±6σ, thus resulting in increased charging time.

[0006] This disclosure is made in view of the foregoing, and the purpose of this disclosure is to provide a battery management device, battery management method and control program that enables efficient charging of lithium-ion secondary batteries.

[0007] The battery management device according to this disclosure includes: a temperature detection unit configured to detect the temperature of a lithium-ion secondary battery; a high-frequency signal supply unit configured to supply a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery; an impedance detection unit configured to detect the real part of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal has been supplied; a calculation unit configured to calculate the amount of Li deposited in the lithium-ion secondary battery based on the detected real part of the AC impedance; and a control unit configured to control the allowable charging power of the lithium-ion secondary battery and control the upper limit temperature of the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery, the upper limit temperature being a standard temperature used to determine whether the lithium-ion secondary battery may reach an overheated state. The battery management device according to this disclosure calculates the amount of Li deposited in the lithium-ion secondary battery based on the real part of the AC impedance detected from the lithium-ion secondary battery to which the high-frequency signal has been supplied, and feeds back the calculation result to control the allowable charging power of the lithium-ion secondary battery. Therefore, the battery management device according to this disclosure can set the permissible charging power of the lithium-ion secondary battery to an appropriate value based on the amount of Li deposition, without setting it to an excessively low value, and thus can efficiently charge the lithium-ion secondary battery. Furthermore, the battery management device according to this disclosure controls the upper limit temperature of the lithium-ion secondary battery (used as a standard temperature to determine whether the lithium-ion secondary battery may reach an overheating state) based on the amount of Li deposition by considering the reduction in the overheat resistance of the lithium-ion secondary battery due to Li deposition, thereby accurately preventing the lithium-ion secondary battery from overheating.

[0008] The high-frequency signal supply unit can provide a high-frequency signal of 0.5MHz or higher to the lithium-ion secondary battery.

[0009] When the temperature of the lithium-ion secondary battery reaches the upper limit, the control unit can limit the charging of the lithium-ion secondary battery.

[0010] The control unit can control the allowable charging power of the lithium-ion secondary battery so that the allowable charging power decreases as the calculated amount of Li deposited in the lithium-ion secondary battery increases, and control the upper limit temperature of the lithium-ion secondary battery so that the upper limit temperature decreases as the calculated amount of Li deposited in the lithium-ion secondary battery increases.

[0011] The control unit can control the upper limit temperature of each of the multiple stacked battery cells based on the amount of Li deposition in a corresponding cell among the multiple stacked battery cells constituting a lithium-ion secondary battery.

[0012] The control unit can control the upper limit temperature of each battery cell, so that the upper limit temperature decreases as the calculated amount of Li deposition in the corresponding battery cell increases.

[0013] The temperature detection unit may include at least one thermistor configured to detect the temperature of at least one of a plurality of battery cells, and the temperature detection unit may estimate the temperature of each of the plurality of battery cells based on the detection results performed by the at least one thermistor and the cell voltage of the corresponding one of the plurality of battery cells.

[0014] In the battery management method according to this disclosure, the battery management device: supplies a high-frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery; detects the real part of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal has been supplied; calculates the amount of Li deposited in the lithium-ion secondary battery based on the detected real part of the AC impedance; controls the permissible charging power of the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery; and controls an upper limit temperature of the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery, the upper limit temperature being a standard temperature used to determine whether the lithium-ion secondary battery may reach an overheated state. In the battery management method according to this disclosure, the amount of Li deposited in the lithium-ion secondary battery is calculated based on the real part of the AC impedance detected from the lithium-ion secondary battery to which the high-frequency signal has been supplied, and the permissible charging power of the lithium-ion secondary battery is controlled based on the calculation result. Therefore, in the battery management method according to this disclosure, the permissible charging power of the lithium-ion secondary battery can be set to an appropriate value based on the amount of Li deposited, without setting it to an excessively low value, and thus the lithium-ion secondary battery can be charged efficiently. Furthermore, in the battery management method according to this disclosure, by taking into account the reduction in the overheat resistance of the lithium-ion secondary battery due to Li deposition, the upper limit temperature of the lithium-ion secondary battery (used as a standard temperature to determine whether the lithium-ion secondary battery may reach an overheating state) is controlled according to the amount of Li deposition, thereby accurately preventing the lithium-ion secondary battery from overheating.

[0015] According to the control program of this disclosure, a computer: supplies a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery; detects the real part of the AC impedance from the lithium-ion secondary battery from which the high-frequency signal has been supplied; calculates the amount of Li deposited in the lithium-ion secondary battery based on the detected real part of the AC impedance; controls the permissible charging power of the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery; and controls the upper limit temperature of the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery, the upper limit temperature being a standard temperature used to determine whether the lithium-ion secondary battery may reach an overheated state. The control program of this disclosure calculates the amount of Li deposited in the lithium-ion secondary battery based on the real part of the AC impedance detected from the lithium-ion secondary battery from which the high-frequency signal has been supplied, and feeds back the calculation result to control the permissible charging power of the lithium-ion secondary battery. Therefore, the control program of this disclosure can set the permissible charging power of the lithium-ion secondary battery to an appropriate value based on the amount of Li deposited, without setting it to an excessively low value, and thus can efficiently charge the lithium-ion secondary battery. Furthermore, the control procedure of this disclosure controls the upper limit temperature of the lithium-ion secondary battery (used as a standard temperature to determine whether the lithium-ion secondary battery may reach an overheating state) based on the amount of Li deposition by taking into account the reduction in the overheating resistance of the lithium-ion secondary battery due to Li deposition, thereby accurately preventing the lithium-ion secondary battery from overheating.

[0016] According to this disclosure, a battery management device, a battery management method, and a control program can be provided to efficiently charge lithium-ion secondary batteries.

[0017] The above and other objects, features and advantages of this disclosure will be more fully understood from the detailed description and accompanying drawings given below. Attached Figure Description

[0018] Figure 1 This is a block diagram illustrating an example configuration of a battery management system according to this disclosure;

[0019] Figure 2 This is a graph showing the relationship between the change in SOH of the secondary battery and the real part Z of the AC impedance when a 1MHz high-frequency signal is supplied to the secondary battery.

[0020] Figure 3 This is a graph showing the relationship between the frequency of the AC signal supplied to the secondary battery and the real part of the AC impedance detected from the secondary battery.

[0021] Figure 4 This is a graph showing the relationship between the frequency of the AC signal supplied to the secondary battery and the real part of the AC impedance detected from the secondary battery; and

[0022] Figure 5 This is a flowchart illustrating the operations performed by the battery management device according to this disclosure. Detailed Implementation

[0023] Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the following embodiments. Furthermore, for clarity, the following description and drawings have been appropriately simplified.

[0024] <First Embodiment>

[0025] Figure 1 This is a block diagram illustrating an example configuration of the battery management system according to the first embodiment. Figure 1 As shown, the battery management system 1 includes a battery management device 10 and a secondary battery 20 managed by the battery management device 10.

[0026] The secondary battery 20 is a lithium-ion secondary battery and includes a cell stack consisting of multiple stacked battery cells and a housing for accommodating the cell stack.

[0027] Each battery cell includes a positive electrode, a negative electrode, and an ion transport medium disposed between the positive and negative electrodes to conduct charge carrier ions. A separator may also be disposed between the positive and negative electrodes. Resins such as polyethylene or polypropylene are used as separators.

[0028] For example, sulfides containing transition metal elements, oxides containing lithium, and other materials containing transition metal elements are used as positive electrode active materials. Specifically, materials with a basic composition such as Li (1-x) MnO2 (where 0) <x<1)、Li (1-x) Lithium-manganese composite oxides of Mn₂O₄, with basic formulas such as Li (1-x) Lithium cobalt composite oxide of CoO2, with a basic composition such as Li (1-x) NiO2 is a lithium-nickel composite oxide with a basic composition such as Li (1-x) Ni a Co b Mn c Lithium-nickel-cobalt-manganese composite oxides containing O2 (where a+b+c=1) are used as positive electrode active materials. Note that materials containing other elements in the above basic formula can also be used as positive electrode active materials. For example, Al (aluminum) is used as the current collector in the positive electrode.

[0029] For example, composite oxides containing lithium, carbon materials, etc., are used as negative electrode active materials. Specifically, inorganic compounds such as lithium, lithium alloys, and tin compounds, carbon materials capable of sealing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers are used as negative electrode active materials. Examples of carbon materials used as negative electrode active materials include coke, glassy carbon, graphite, non-graphitizable carbon, pyrolytic carbon, and carbon fibers, and graphite such as artificial graphite or natural graphite is preferred. Furthermore, examples of composite oxides used as negative electrode active materials include lithium-titanium composite oxides and lithium-vanadium composite oxides. For example, Cu (copper) is used as a current collector for the negative electrode.

[0030] For example, an ion-conducting medium can be used as an electrolyte by dissolving a carrier salt. For example, lithium salts such as LiPF6 and LiBF4 can be used as carrier salts. For example, one or a mixture of carbonates, esters, ethers, nitriles, furans, sulfolane, and dioxolane can be used as a solvent for the electrolyte. Examples of carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butyl carbonate, and ethylene chloride carbonate, and chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl n-butyl carbonate, methyl tert-butyl carbonate, diisopropyl carbonate, and tert-butyl carbonate. Alternatively, solid ion-conducting polymers, inorganic solid electrolytes, mixtures of organic polymer electrolytes and inorganic solid electrolytes, and inorganic solid powders bonded by organic adhesives can be used as ion-conducting media.

[0031] The battery management device 10 manages the charging of the secondary battery 20 to be managed. For example, the battery management device 10 detects the amount of Li deposition in the secondary battery 20 in a non-destructive manner and, based on the detection result, feeds back and controls the allowable charging power (upper limit of charging power) Pa of the secondary battery 20. In addition, the battery management device 10 detects the temperature of the secondary battery 20 and, based on the detection result, feeds back and controls an upper limit temperature Ta, which is a standard temperature used to determine whether the secondary battery 20 may reach an overheated state.

[0032] The battery management device 10 includes a high-frequency signal supply unit 11, an impedance detection unit 12, a calculation unit 13, a control unit 14, a storage unit 15, and a temperature detection unit 16.

[0033] The high-frequency signal supply unit 11 supplies a high-frequency signal to the secondary battery 20. The impedance detection unit 12 detects the real part Z of the AC impedance from the secondary battery 20, which has been supplied with a high-frequency signal.

[0034] It should be noted that in the secondary battery 20, metallic Li is deposited on the electrode surface of each cell through repeated charging. Li deposition is accelerated by increasing charging power to increase the charging rate, and thus degrades the state of health (SOH) of the secondary battery 20. Note that when assuming the initial capacity of the secondary battery 20 is 100%, the SOH of the secondary battery 20 is a percentage of its current capacity. Therefore, it is desirable to set a maximum permissible charging power Pa for the secondary battery 20, which allows the secondary battery 20 to be charged efficiently in the shortest possible charging time while suppressing Li deposition.

[0035] Note that when a high-frequency AC signal (high-frequency signal) that cannot follow the diffusion, reaction, and movement of lithium ions is supplied to the secondary battery 20, due to the skin effect, the current of the high-frequency signal flows along the edge of the conductor in each of the battery cells. In other words, the current of the high-frequency signal flows through the electrode surface of each of the battery cells, where Li deposition easily occurs due to the skin effect. Furthermore, even when the Li metal is electrically disconnected from the negative electrode and enters a floating state after Li deposition, current flows on the Li metal through inductive coupling and electric field coupling. Therefore, for example, as the amount of Li deposition decreases, the conductivity of the electrode surface in each of the battery cells decreases, and thus the real part Z of the AC impedance increases. Conversely, as the amount of Li deposition increases, the conductivity of the electrode surface in each of the battery cells increases, and thus the real part Z of the AC impedance decreases. Note that since a large amount of current is concentrated on the Li metal with high conductivity, the magnetic field changes around the Li deposition region, and thus eddy currents are generated. These eddy currents cause losses in the current collector foil and the conductive parts of the electrodes. However, the overall battery loss decreases. Therefore, as the amount of Li deposited increases, the change in the magnetic field increases. As a result, eddy currents increase, and therefore the value of the real part Z decreases. Therefore, the amount of Li deposited in the secondary battery 20 can be calculated based on the value of the real part Z of the AC impedance detected from the secondary battery 20 which has been supplied with a high-frequency signal. If the amount of Li deposited is known, the SOH of the secondary battery 20 can be estimated.

[0036] Figure 2 This is a graph showing the relationship between the state of harmonics (SOH) of the secondary battery 20 and the change in the real part Z of the AC impedance (the difference between the detected value and the initial value) when a 1MHz high-frequency signal is supplied to the secondary battery 20. (See graph for example.) Figure 2 As indicated by the triangle in the diagram, under normal charging conditions with low charging power, the amount of Li deposition is low even with repeated charging. Therefore, even if the degradation of SOH is advanced due to other factors (i.e., the detected value of the real part Z of the AC impedance remains high), the change in the real part Z of the AC impedance remains small. On the other hand, as... Figure 2The circles in the diagram indicate that, under high-power fast charging conditions, the amount of Li deposition increases during repeated charging. Therefore, the degradation of the State of Electron Oxide (SOH) is accelerated, and consequently, the change in the real part Z of the AC impedance increases (i.e., the detected value of the real part Z of the AC impedance is low). Note that when battery degradation due to Li deposition is the primary factor, the amount of Li deposition can be derived from the SOH. Alternatively, the SOH can originate from the amount of Li deposition.

[0037] Figure 3 and Figure 4 Each of the graphs is a diagram showing the relationship between the frequency of the AC signal supplied to the secondary battery 20 and the real part of the AC impedance detected by the secondary battery 20. Figure 3 The value of the real part Z of the AC impedance is shown when an AC signal from 1 kHz to 100 kHz is supplied to the secondary battery 20. Figure 4 The real part Z of the AC impedance is shown when an AC signal from 100 kHz to 100 MHz is supplied to the secondary battery 20.

[0038] like Figure 3 As shown, when an AC signal of approximately 1 kHz is supplied to the secondary battery 20, the real part Z of the AC impedance is at its minimum. The impedance component at this time indicates the ohmic resistance component. Furthermore, as... Figure 3 and Figure 4 As shown, the higher the frequency of the AC signal supplied to the secondary battery 20, the more current is concentrated on the surface of each electrode in the cell due to the skin effect, and therefore the value of the real part Z of the AC impedance increases.

[0039] Therefore, the high-frequency signal supply unit 11 supplies a high-frequency AC signal (i.e., a high-frequency signal) to the secondary battery 20, using which the real part Z of the AC impedance, sufficiently higher than the ohmic resistance component, can be detected. For example, the high-frequency signal supply unit 11 supplies a high-frequency signal of 0.1 MHz or higher to the secondary battery 20. Figure 3 and 4 In the example shown, the high-frequency signal supply unit 11 supplies a high-frequency signal of 0.5 MHz or higher to the secondary battery 20. Therefore, due to the skin effect, the current from the high-frequency signal flows through the electrode surface (Li deposition region) of each cell in the secondary battery 20. Consequently, the impedance detection unit 12 can detect the real part Z of the AC impedance corresponding to the amount of Li deposition.

[0040] The calculation unit 13 calculates the amount of Li deposition in the secondary battery 20 based on the value of the real part Z of the AC impedance detected by the impedance detection unit 12. More specifically, the calculation unit 13 calculates the amount of Li deposition in the secondary battery 20 based on the difference between the current value of the real part Z of the AC impedance detected by the impedance detection unit 12 and the initial value of the real part Z of the AC impedance of the secondary battery 20. Information about the initial value of the real part Z of the AC impedance of the secondary battery 20 to be managed is stored, for example, in the storage unit 15.

[0041] For example, calculation unit 13 calculates a smaller amount of Li deposition as the detected value of the real part Z of the AC impedance becomes larger, and at the same time, it calculates a larger amount of Li deposition as the detected value of the real part Z of the AC impedance becomes smaller.

[0042] Note that information regarding the initial value of the real part Z of the AC impedance for each type of secondary battery can be stored in the storage unit 15. Furthermore, mapping information indicating the relationship between the difference (change) between the initial value and the current value (detected value) of the real part Z of the AC impedance for each type of secondary battery and the amount of Li deposition can be stored in the storage unit 15. This mapping information is, for example, information obtained in advance through experiments and can be appropriately updated based on information detected from the secondary battery 20 to be managed. In this case, the calculation unit 13 extracts the amount of Li deposition corresponding to the value of the real part Z of the AC impedance detected by the impedance detection unit 12 from the mapping information stored in the storage unit 15.

[0043] The control unit 14 controls the allowable charging power Pa of the secondary battery 20 based on the amount of Li deposition calculated by the calculation unit 13. For example, when the calculated amount of Li deposition is low, the control unit 14 either maintains the allowable charging power Pa or controls it in a way that increases it, because the progression of Li deposition is suppressed. Furthermore, the control unit 14 controls the allowable charging power Pa in a way that decreases as the calculated amount of Li deposition increases, because it is necessary to suppress the progression of Li deposition. Note that the control unit 14 can switch the allowable charging power Pa in a stepwise manner according to the calculated amount of Li deposition.

[0044] By doing so, the battery management device 10 according to this disclosure can set a maximum possible allowable charging power Pa for the secondary battery 20, which enables the secondary battery 20 to be efficiently charged in the shortest possible charging time while suppressing Li deposition. That is, the battery management device 10 according to this disclosure can set the allowable charging power Pa of the secondary battery 20 to an appropriate value according to the amount of Li deposition, without setting it to an excessively low value, and thus can charge the secondary battery 20 efficiently.

[0045] Temperature detection unit 16 detects the temperature of secondary battery 20. For example, temperature detection unit 16 detects the temperature of at least one of the plurality of battery cells constituting secondary battery 20 using at least one thermistor T1. Furthermore, temperature detection unit 16 calculates the resistance value of each of the plurality of battery cells based on the cell voltage of the corresponding cell. Then, temperature detection unit 16 calculates the difference between the heat generation of each of the plurality of battery cells and the heat generation of the battery cell with the thermistor T1 attached, based on the difference between the calculated resistance value of each of the plurality of battery cells and the resistance value of the battery cell with the thermistor T1 attached, and estimates the temperature of each of the plurality of battery cells based on the calculation results.

[0046] When the temperature of the secondary battery 20 detected by the temperature detection unit 16 reaches the upper limit temperature Ta, the control unit 14 determines that the secondary battery 20 may have reached an overheated state and limits (e.g., stops) the charging of the secondary battery 20. The upper limit temperature Ta is the standard temperature used to determine whether the secondary battery 20 may have reached an overheated state.

[0047] Note that the overheating resistance of the secondary battery 20 is known to decrease as Li deposition progresses. Therefore, the control unit 14 controls not only the allowable charging power Pa of the secondary battery 20, but also the upper limit temperature Ta of the secondary battery 20. The upper limit temperature Ta is used as a standard temperature to determine whether the secondary battery 20 may reach an overheating state based on the amount of Li deposition in the secondary battery 20.

[0048] For example, when the calculated Li deposition amount is small, the control unit 14 maintains the upper limit temperature Ta of the secondary battery 20 by itself because the overheating resistance of the secondary battery 20 is maintained at a high value. Conversely, the control unit 14 decreases the upper limit temperature Ta of the secondary battery 20 because the overheating resistance of the secondary battery 20 decreases as the calculated Li deposition amount increases. Note that as the Li deposition amount increases, the control unit 14 can gradually reduce the upper limit temperature Ta of the secondary battery 20 to initial values ​​such as 130 degrees, 120 degrees, and 110 degrees.

[0049] By doing so, the battery management device 10 according to this disclosure can accurately prevent overheating of the secondary battery 20. Note that the control unit 14 can individually control the upper limit temperature Ta of the plurality of battery cells constituting the secondary battery 20 based on the corresponding amount of Li deposition in the plurality of battery cells. In this case, the control unit 14 controls the upper limit temperature Ta of the battery cells such that it decreases as the calculated amount of Li deposition in the battery cells increases.

[0050] (Operation of battery management device 10)

[0051] Next, we will refer to Figure 5Describe the operations performed by the battery management device 10. Figure 5 This is a flowchart illustrating the operations performed by the battery management device 10.

[0052] First, the battery management device 10 supplies a high-frequency AC signal (high-frequency signal) to the secondary battery 20, which is not susceptible to the diffusion, reaction, and movement of lithium ions in each battery cell (step S101). For example, the battery management device 10 supplies a high-frequency signal of 0.1 MHz or higher to the secondary battery 20. Then, the battery management device 10 detects the value of the real part Z of the AC impedance from the secondary battery 20, which has been supplied with the high-frequency signal (step S102).

[0053] Then, the battery management device 10 calculates the amount of Li deposited in the secondary battery 20 based on the detected value of the real part Z of the AC impedance (step S103). For example, the battery management device 10 extracts the amount of Li deposited corresponding to the detected value of the real part Z of the AC impedance from the mapping information stored in the storage unit 15. Basically, the battery management device 10 calculates a smaller amount of Li deposited as the detected value of the real part Z of the AC impedance increases, and at the same time, it calculates a larger amount of Li deposited as the detected value of the real part Z of the AC impedance decreases.

[0054] Subsequently, the battery management device 10 controls the allowable charging power Pa of the secondary battery 20 based on the calculated Li deposition amount (step S104). For example, when the calculated Li deposition amount is small, the battery management device 10 maintains the allowable charging power Pa by itself or controls it to increase because the propagation of Li deposition is suppressed. Furthermore, the battery management device 10 controls the allowable charging power Pa to decrease as the calculated Li deposition amount increases, because it is necessary to suppress the propagation of Li deposition.

[0055] Furthermore, the battery management device 10 controls the upper limit temperature Ta of the secondary battery 20 based on the calculated Li deposition amount, which is used as a standard temperature to determine whether the secondary battery 20 may reach an overheated state (step S105). For example, when the calculated Li deposition amount is small, the battery management device 10 maintains the upper limit temperature Ta of the secondary battery 20 by itself because the overheating resistance of the secondary battery 20 remains high, while the battery management device 10 lowers the upper limit temperature Ta of the secondary battery 20 because the overheating resistance of the secondary battery 20 decreases as the calculated Li deposition amount increases.

[0056] As described above, the battery management device 10 according to this disclosure can set a maximum possible allowable charging power Pa for the secondary battery 20, which enables the secondary battery 20 to be efficiently charged in the shortest possible charging time while suppressing Li deposition. That is, the battery management device 10 according to this disclosure can set the allowable charging power Pa of the secondary battery 20 to an appropriate value according to the amount of Li deposition, without setting it to an excessively low value, and thus can efficiently charge the secondary battery 20.

[0057] Furthermore, the battery management device 10 of this disclosure controls the upper limit temperature Ta of the lithium-ion secondary battery (used as a standard temperature for determining whether the lithium-ion secondary battery may reach an overheating state) based on the amount of Li deposition by taking into account the reduction in the overheating resistance of the lithium-ion secondary battery due to Li deposition, thereby accurately preventing the lithium-ion secondary battery from overheating.

[0058] In this disclosure, an example has been described where the temperature detection unit 16 detects the secondary battery 20 using a thermistor T1 and the cell voltage. However, this disclosure is not limited thereto. For example, the temperature detection unit 16 may be configured to detect the battery temperature of the thermistor T1 instead of the temperature of the secondary battery 20. In this case, as the amount of Li deposition increases, the control unit 14 gradually reduces the battery temperature of the thermistor T1 to initial values ​​such as 60 degrees, 55 degrees, and 50 degrees, thereby gradually reducing the upper limit temperature Ta of the secondary battery 20.

[0059] Furthermore, in this disclosure, some or all of the processes performed by the battery management device 10 can be implemented by having the central processing unit (CPU) execute a computer program.

[0060] The program described above includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more of the functions described in the embodiments. The program may be stored on a non-transitory computer-readable medium or tangible storage medium. By way of example, and not limitation, a non-transitory computer-readable medium or tangible storage medium may include random access memory (RAM), read-only memory (ROM), flash memory, solid-state drives (SSDs) or other types of memory technologies, CD-ROMs, digital versatile discs (DVDs), Blu-ray discs or other types of optical disc storage, magnetic cartridges, magnetic tapes, and disk storage or other types of magnetic storage devices. The program may be transmitted on a transient computer-readable medium or communication medium. By way of example, and not limitation, a transient computer-readable medium or communication medium may include electrical, optical, acoustic, or other forms of propagation signals.

[0061] Although this disclosure has been described with reference to embodiments, it is not limited to the embodiments described above. Various changes to the configurations and details of this disclosure, as will be understood by those skilled in the art, are possible within the scope of this disclosure. Furthermore, each of the embodiments may be suitably combined with at least one of the other embodiments.

[0062] As will be apparent from the present disclosure as described herein, embodiments of the present disclosure may vary in many ways. Such variations should not be considered as departing from the spirit and scope of the present disclosure, and all such modifications that will be apparent to those skilled in the art are intended to be included within the scope of the appended claims.

Claims

1. A battery management device, comprising: A temperature detection unit is configured to detect the temperature of a lithium-ion secondary battery. A high-frequency signal supply unit is configured to provide a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery; An impedance detection unit is configured to detect the real part of the AC impedance from the lithium-ion secondary battery that has been supplied with the high-frequency signal; A calculation unit is configured to calculate the amount of Li deposited in the lithium-ion secondary battery from the value of the real part of the detected AC impedance; as well as The control unit is configured to: control the allowable charging power of the lithium-ion secondary battery and control the upper limit temperature of the lithium-ion secondary battery based on the calculated amount of Li deposition in the lithium-ion secondary battery, the upper limit temperature being used as a standard temperature for determining whether the lithium-ion secondary battery may reach an overheated state.

2. The battery management device according to claim 1, wherein, The high-frequency signal supply unit supplies the lithium-ion secondary battery with a high-frequency signal of 0.5 MHz or higher.

3. The battery management device according to claim 1, wherein, When the temperature of the lithium-ion secondary battery reaches the upper limit temperature, the control unit restricts the charging of the lithium-ion secondary battery.

4. The battery management device according to claim 1, wherein, The control unit controls the allowable charging power of the lithium-ion secondary battery such that the allowable charging power decreases as the calculated amount of Li deposited in the lithium-ion secondary battery increases, and controls the upper limit temperature of the lithium-ion secondary battery such that the upper limit temperature decreases as the calculated amount of Li deposited in the lithium-ion secondary battery increases.

5. The battery management device according to claim 1, wherein, The control unit controls the upper limit temperature of each of the plurality of stacked battery cells based on the amount of Li deposition in a corresponding battery cell among the plurality of stacked battery cells constituting the lithium-ion secondary battery.

6. The battery management device according to claim 5, wherein, The control unit controls the upper limit temperature of each battery cell in the battery cells such that the upper limit temperature decreases as the calculated amount of Li deposition in the corresponding battery cell increases.

7. The battery management device according to claim 5, wherein, The temperature detection unit includes at least one thermistor, which is configured to detect the temperature of at least one of the plurality of battery cells. The temperature detection unit estimates the temperature of each of the plurality of battery cells based on the results of detection performed by the at least one thermistor and the cell voltage of a corresponding battery cell among the plurality of battery cells.

8. A battery management method executed by a battery management device, the battery management method comprising: Supplying a high-frequency signal of 0.1MHz or higher to the lithium-ion secondary battery; The real part of the AC impedance is detected from the lithium-ion secondary battery that has been supplied with the high-frequency signal; The amount of Li deposited in the lithium-ion secondary battery is calculated from the real part of the detected AC impedance; The allowable charging power of the lithium-ion secondary battery is controlled based on the calculated amount of Li deposition in the lithium-ion secondary battery. as well as The upper limit temperature of the lithium-ion secondary battery is controlled based on the calculated amount of Li deposition in the battery. This upper limit temperature is used as a standard temperature to determine whether the lithium-ion secondary battery may reach an overheated state.

9. A control program product for enabling a computer to: Supplying a high-frequency signal of 0.1MHz or higher to the lithium-ion secondary battery; The real part of the AC impedance is detected from the lithium-ion secondary battery that has been supplied with the high-frequency signal; The amount of Li deposited in the lithium-ion secondary battery is calculated from the real part of the detected AC impedance. The allowable charging power of the lithium-ion secondary battery is controlled based on the calculated amount of Li deposition in the lithium-ion secondary battery. as well as The upper limit temperature of the lithium-ion secondary battery is controlled based on the calculated amount of Li deposition in the battery. This upper limit temperature is used as a standard temperature to determine whether the lithium-ion secondary battery may reach an overheated state.

Images