Battery management device, battery management method, and control program

Abstract

To provide a battery management device, a battery management method, and a control program that enable efficient charging of lithium-ion secondary batteries. [Solution] The battery management device according to the present disclosure includes: a temperature detection unit for detecting the temperature of a lithium-ion secondary battery; a high-frequency signal supply unit for supplying a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery; an impedance detection unit for detecting the real value of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal has been supplied; a calculation unit for calculating the amount of Li deposited in the lithium-ion secondary battery from the detected real value of the AC impedance; and a control unit for controlling the allowable charging power for the lithium-ion secondary battery and the upper limit temperature of the lithium-ion secondary battery, which is a temperature that serves as a criterion for determining whether or not the lithium-ion secondary battery is at risk of overheating.

Description

Technical Field

[0001] The present disclosure relates to a battery management device, a battery management method, and a control program.

Background Art

[0002] In order to prevent deterioration of the performance of a lithium-ion secondary battery, it is required to suppress the precipitation of metallic Li (lithium) in the lithium-ion secondary battery (hereinafter referred to as Li precipitation). However, a method for non-destructively detecting Li precipitation in a lithium-ion secondary battery has not been known.

[0003] On the other hand, 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 precipitation in the lithium-ion secondary battery based on the difference between the current value and the initial value of the real part of the AC impedance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, since Li precipitation progresses as the charging power increases, the allowable charging power is set for each type of lithium-ion secondary battery from the viewpoint of suppressing Li precipitation. Here, the progress rate of Li precipitation in a lithium-ion secondary battery has variations (for example, standard deviation σ) for each individual product even within the same type. In conventional lithium-ion secondary batteries, for example, the allowable charging power for each type has been set (fixed) too low so that Li precipitation does not progress in products included in the range of ±6σ, resulting in a problem of lengthening the charging time.

[0006] This disclosure is made in view of the above background and aims to provide a battery management device, a battery management method, and a control program that can achieve efficient charging of lithium-ion secondary batteries. [Means for solving the problem]

[0007] The battery management device according to this disclosure comprises: a temperature detection unit for detecting the temperature of the lithium-ion secondary battery; a high-frequency signal supply unit for supplying a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery; an impedance detection unit for detecting the real part value of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied; a calculation unit for calculating the amount of Li deposited in the lithium-ion secondary battery from the detected real part value of the AC impedance; and a control unit for controlling the allowable charging power for the lithium-ion secondary battery and for controlling the upper limit temperature of the lithium-ion secondary battery, which is a temperature that serves as a criterion for determining whether or not the lithium-ion secondary battery is at risk of overheating. The battery management device according to this disclosure calculates the amount of Li deposited in the lithium-ion secondary battery from the real part value of the AC impedance detected from the lithium-ion secondary battery to which the high-frequency signal is supplied, and provides feedback control of the allowable charging power for the lithium-ion secondary battery based on the calculated result. As a result, the battery management device according to this disclosure can set the allowable charging power for lithium-ion secondary batteries to an appropriate value according to the amount of Li deposition, without setting it excessively low, thereby enabling efficient charging of lithium-ion secondary batteries. Furthermore, the battery management device according to this disclosure can accurately prevent overheating of lithium-ion secondary batteries by controlling the upper limit temperature of the lithium-ion secondary battery (the temperature that serves as a criterion for determining whether or not the lithium-ion secondary battery is at risk of reaching an overheated state) according to the amount of Li deposition, taking into account the decrease in the lithium-ion secondary battery's resistance to overheating due to Li deposition.

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

[0009] The control unit may limit the charging of the lithium-ion secondary battery when the temperature of the lithium-ion secondary battery reaches the upper limit temperature.

[0010] The control unit may control 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 also control the lithium-ion secondary battery so that the upper limit temperature decreases.

[0011] The control unit may control the upper limit temperature of each of the stacked battery cells constituting the lithium-ion secondary battery based on the amount of Li deposited in each of the stacked battery cells.

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

[0013] The temperature detection unit may have one or more thermistors for detecting the temperature of one or more of the plurality of battery cells, and may estimate the temperature of each of the plurality of battery cells based on the detection results of the one or more thermistors and the cell voltage of each of the plurality of battery cells.

[0014] In the battery management method according to this disclosure, a battery management device supplies a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery, detects the real part value of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied, calculates the amount of Li deposited in the lithium-ion secondary battery from the detected real part value of the AC impedance, controls the allowable charging power for 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, which is the temperature at which it is determined whether or not the lithium-ion secondary battery is at risk of overheating, based on the calculated amount of Li deposited in the lithium-ion secondary battery. The battery management method according to this disclosure calculates the amount of Li deposited in the lithium-ion secondary battery from the real part value of the AC impedance detected from the lithium-ion secondary battery to which the high-frequency signal is supplied, and feedback controls the allowable charging power for the lithium-ion secondary battery based on the calculated result. As a result, the battery management method according to this disclosure can set the allowable charging power for the lithium-ion secondary battery to an appropriate value according to the amount of Li deposited without setting it excessively low, thereby enabling efficient charging of the lithium-ion secondary battery. Furthermore, the battery management method described herein can accurately prevent overheating of a lithium-ion secondary battery by controlling the upper limit temperature of the lithium-ion secondary battery (the temperature that serves as a criterion for determining whether or not the lithium-ion secondary battery is at risk of overheating) according to the amount of Li deposited, taking into account the decrease in the lithium-ion secondary battery's resistance to overheating due to Li deposition.

[0015] The control program according to this disclosure causes a computer to perform the following processes: supplying a high-frequency signal to the lithium-ion secondary battery such that, compared to the real part value of the AC impedance detected when a 1 kHz AC signal is supplied to the lithium-ion secondary battery, the real part value of the AC impedance is detected to be 10 times or more due to the skin effect; detecting the real part value of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal has been supplied; calculating the amount of Li deposited in the lithium-ion secondary battery from the detected real part value of the AC impedance; controlling the allowable charging power for the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery; and controlling the upper limit temperature of the lithium-ion secondary battery, which is the temperature at which it is determined whether or not the lithium-ion secondary battery is at risk of overheating, based on the calculated amount of Li deposited in the lithium-ion secondary battery. The control program according to this disclosure calculates the amount of Li deposited in the lithium-ion secondary battery from the real part value of the AC impedance detected from the lithium-ion secondary battery to which the high-frequency signal has been supplied, and feedback-controls the allowable charging power for the lithium-ion secondary battery based on the calculated result. As a result, the control program according to this disclosure can set the allowable charging power for the lithium-ion secondary battery to an appropriate value according to the amount of Li deposition, without setting it excessively low, thereby enabling efficient charging of the lithium-ion secondary battery. Furthermore, the control program according to this disclosure can accurately prevent overheating of the lithium-ion secondary battery by controlling the upper limit temperature of the lithium-ion secondary battery (the temperature that serves as a criterion for determining whether or not the lithium-ion secondary battery is at risk of overheating) according to the amount of Li deposition, taking into account the decrease in the lithium-ion secondary battery's resistance to overheating due to Li deposition. [Effects of the Invention]

[0016] This disclosure provides a battery management device, a battery management method, and a control program that enable efficient charging of lithium-ion secondary batteries. [Brief explanation of the drawing]

[0017] [Figure 1] It is a block diagram showing a configuration example of a battery management system according to the present disclosure. [Figure 2] It is a diagram showing the relationship between the SOH of a secondary battery and the change amount of the real part Z of the AC impedance when a high-frequency signal of 1 MHz is supplied to the secondary battery. [Figure 3] It is a diagram showing the relationship between the frequency of an AC signal supplied to a secondary battery and the real part of the AC impedance detected from the secondary battery. [Figure 4] It is a diagram showing the relationship between the frequency of an AC signal supplied to a secondary battery and the real part of the AC impedance detected from the secondary battery. [Figure 5] It is a flowchart showing the operation of a battery management device according to the present disclosure.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings are simplified as appropriate.

[0019] <Embodiment 1> FIG. 1 is a block diagram showing a configuration example of a battery management system according to Embodiment 1. As shown in FIG. 1, the battery management system 1 includes a battery management device 10 and a secondary battery 20 managed by the battery management device 10.

[0020] The secondary battery 20 is a lithium-ion secondary battery and is composed of a cell stack including a plurality of stacked battery cells and a case housing the cell stack.

[0021] Each battery cell comprises a positive electrode, a negative electrode, and an ion transport medium provided between the positive and negative electrodes for conducting carrier ions. A separator may be further provided between the positive and negative electrodes. The separator is made of a resin such as polyethylene or polypropylene.

[0022] For example, positive electrode active materials include sulfides containing transition metal elements and oxides containing lithium and transition metal elements. Specifically, positive electrode active materials have the basic composition formula Li (1-x) MnO2 (but 0 <x<1)やLi (1-x) Lithium manganese composite oxides such as Mn2O4, with the basic composition formula being Li (1-x) Lithium cobalt composite oxides such as CoO2, with the basic composition formula being Li (1-x) Lithium nickel composite oxides such as NiO2, or the basic composition formula Li (1-x) Ni a Co b Mn c Lithium nickel cobalt manganese composite oxides such as O2 (where a+b+c=1) are used. Note that the positive electrode active material may include other elements in addition to the basic composition formula described above. For the positive electrode current collector, for example, aluminum (Al) is used.

[0023] For example, composite oxides containing lithium or carbon materials are used as the negative electrode active material. Specifically, the negative electrode active material may be an inorganic compound such as lithium, lithium alloys, or tin compounds, a carbon material capable of intercalating and deintercalating lithium ions, a composite oxide containing multiple elements, or a conductive polymer. Examples of carbon materials used for the negative electrode active material include coke, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, or carbon fibers, but graphites such as artificial graphite or natural graphite are preferred. Examples of composite oxides used for the negative electrode active material include lithium titanium composite oxide and lithium vanadium composite oxide. For the current collector of the negative electrode, for example, Cu (copper) is used.

[0024] The ion-conducting medium is used as an electrolyte, for example, by dissolving a supporting salt. Lithium salts such as LiPF6 and LiBF4 are used as supporting salts. The solvent for the electrolyte is one or a mixture of several of the following: carbonates, esters, ethers, nitriles, furans, sulforanes, and dioxolanes. Examples of carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, and linear carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate. Alternatively, the ion-conducting medium may be a solid ion-conducting polymer, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, or an inorganic solid powder bound together by an organic binder.

[0025] The battery management device 10 manages the charging of the secondary battery 20 under management. For example, the battery management device 10 non-destructively detects the amount of Li deposition in the secondary battery 20 and, based on the detection result, provides feedback control of the allowable charging power (upper limit of charging power) Pa for the secondary battery 20. The battery management device 10 also detects the temperature of the secondary battery 20 and, based on the detection result, provides feedback control of the upper limit temperature Ta, which is the temperature at which it is determined whether or not the secondary battery 20 is at risk of overheating.

[0026] 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.

[0027] The high-frequency signal supply unit 11 supplies a high-frequency signal to the secondary battery 20. The impedance detection unit 12 detects the value of the real part Z of the AC impedance from the secondary battery 20 to which the high-frequency signal has been supplied.

[0028] Incidentally, in the secondary battery 20, metallic Li is deposited on the electrode surface of each battery cell as charging is repeated. Li deposition progresses as the charging power is increased to speed up the charging process, degrading the State of Health (SOH) of the secondary battery 20. The SOH of the secondary battery 20 is the ratio of the current capacity to the initial capacity of the secondary battery 20, which is set to 100%. Therefore, it is desirable to set the allowable charging power Pa of the secondary battery 20 to be as high as possible, which allows for efficient charging in the shortest possible charging time while suppressing Li deposition.

[0029] Here, if an AC signal (high-frequency signal) with a frequency too high for the diffusion, reaction, and movement of lithium ions in each cell of the secondary battery 20 is supplied to the secondary battery 20, the current of the high-frequency signal flows along the edges of the conductors of each cell due to the skin effect. In other words, the current of the high-frequency signal flows along the electrode surface of each cell where Li is easily deposited due to the skin effect. Furthermore, even when the Li metal is electrically disconnected from the negative electrode and becomes a floating state after Li deposition, current flows on the Li metal due to inductive coupling and electric field coupling. Therefore, for example, the less Li is deposited, the lower the electrical conductivity of the electrode surface of each cell, and the larger the real part Z of the AC impedance. Conversely, the more Li is deposited, the higher the electrical conductivity of the electrode surface of each cell, and the smaller the real part Z of the AC impedance. Here, since a lot of current concentrates in the highly conductive Li metal, the magnetic field changes around the Li deposition region, and eddy currents are generated as a result. These eddy currents cause losses in the conductive parts of the current collector foil and electrodes, but reduce the overall loss of the battery. Therefore, as the amount of Li deposited increases, the change in the magnetic field becomes larger, and consequently the eddy currents increase, so the value of the real part Z decreases. For this reason, the amount of Li deposited in the secondary battery 20 can be calculated from the value of the real part Z of the AC impedance detected from the secondary battery 20 to which a high-frequency signal is supplied. If the amount of Li deposited is known, it is also possible to estimate the SOH of the secondary battery 20.

[0030] Figure 2 shows the relationship between the State of Health (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 1 MHz high-frequency signal is supplied to the secondary battery 20. As indicated by the triangles in Figure 2, in the case of normal charging with low charging power, even if charging is repeated, the amount of Li deposition is small, so even if the deterioration of SOH progresses due to other factors, the change in the real part Z of the AC impedance remains small (i.e., the detected value of the real part Z of the AC impedance is maintained at a high value). In contrast, as indicated by the circles in Figure 2, in the case of rapid charging with high charging power, the amount of Li deposition increases with repeated charging, and consequently, the deterioration of SOH progresses, and the change in the real part Z of the AC impedance becomes large (i.e., the detected value of the real part Z of the AC impedance becomes low). Note that if battery degradation due to Li deposition is the dominant factor among the factors of battery degradation, the amount of Li deposition can be derived from SOH. Alternatively, SOH can be derived from the amount of Li deposition.

[0031] Figures 3 and 4 show the relationship between the frequency of the AC signal supplied to the secondary battery 20 and the real part of the AC impedance detected from the secondary battery 20. Figure 3 shows the value of the real part Z of the AC impedance when an AC signal from 1 kHz to 100 kHz is supplied to the secondary battery 20. Figure 4 shows the value of the real part Z of the AC impedance when an AC signal from 100 kHz to 100 MHz is supplied to the secondary battery 20.

[0032] As shown in Figure 3, when an AC signal near 1 kHz is supplied to the secondary battery 20, the real part Z of the AC impedance is at its minimum value. The impedance component at this time represents the ohmic resistance component. Furthermore, as shown in Figures 3 and 4, as the frequency of the AC signal supplied to the secondary battery 20 increases, the real part Z of the AC impedance increases because the current flow concentrates on the electrode surface of each cell due to the skin effect.

[0033] 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 such that a value of the real part Z of the AC impedance is detected that is sufficiently high compared to the ohmic resistance component. 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. In the examples of Figures 3 and 4, the high-frequency signal supply unit 11 supplies a high-frequency signal of 0.5 MHz or higher to the secondary battery 20. As a result, the current of the high-frequency signal flows through the electrode surface (Li deposition region) of each battery cell of the secondary battery 20 due to the skin effect. As a result, the impedance detection unit 12 can detect the real part Z of the AC impedance according to the amount of Li deposition.

[0034] The calculation unit 13 calculates the amount of Li deposited in the secondary battery 20 from 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 deposited 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 on the initial value of the real part Z of the AC impedance of the secondary battery 20 being managed is stored, for example, in the storage unit 15.

[0035] For example, the calculation unit 13 calculates a smaller Li deposition amount the larger the real part Z value of the detected AC impedance, and calculates a larger Li deposition amount the smaller the real part Z value of the detected AC impedance.

[0036] The memory unit 15 may also store information on the initial value of the real part Z of the AC impedance for each type of secondary battery. Furthermore, the memory unit 15 may store map information representing the relationship between the current value (detected value) and the difference (change amount) between the initial value and the amount of Li deposition of the real part Z of the AC impedance for each type of secondary battery. This map information is, for example, information obtained in advance through experiments, but may be updated as appropriate based on information detected from the secondary battery 20 under management. 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 map information stored in the memory unit 15.

[0037] The control unit 14 controls the allowable charging power Pa for the secondary battery 20 based on the amount of Li deposition calculated by the calculation unit 13. For example, if the calculated amount of Li deposition is small, the control unit 14 maintains the allowable charging power Pa at its current level or controls it to be higher, as the progress of Li deposition is suppressed. If the calculated amount of Li deposition is large, the control unit 14 controls the allowable charging power Pa to be lowered, as it is necessary to suppress the progress of Li deposition. The control unit 14 may also switch the allowable charging power Pa in stages according to the calculated amount of Li deposition.

[0038] As a result, the battery management device 10 according to this disclosure can set the highest possible allowable charging power Pa for the secondary battery 20, enabling efficient charging in the shortest possible charging time while suppressing Li deposition. In other words, the battery management device 10 according to this disclosure can set the allowable charging power Pa for the secondary battery 20 to an appropriate value according to the amount of Li deposition, without setting it excessively low, thereby enabling efficient charging of the secondary battery 20.

[0039] The temperature detection unit 16 detects the temperature of the secondary battery 20. For example, the temperature detection unit 16 detects the temperature of one or more of the multiple battery cells that make up the secondary battery 20 using one or more thermistors T1. The temperature detection unit 16 also calculates the resistance value of each of the multiple battery cells from the cell voltage of each of the multiple battery cells. Then, the temperature detection unit 16 calculates the difference between the heat generated by each of the multiple battery cells and the heat generated by the battery cell to which thermistor T1 is attached, based on the difference between the calculated resistance values ​​of each of the multiple battery cells and the resistance value of the battery cell to which thermistor T1 is attached, and estimates the temperature of each of the multiple battery cells from the calculation result.

[0040] 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 there is a risk of the secondary battery 20 overheating and restricts (including stopping) the charging of the secondary battery 20. The upper limit temperature Ta is the temperature that serves as the criterion for determining whether or not there is a risk of the secondary battery 20 overheating.

[0041] It is known that the resistance of the secondary battery 20 to overheating decreases as Li deposition progresses. Therefore, the control unit 14 not only controls the allowable charging power Pa for the secondary battery 20 based on the amount of Li deposition in the secondary battery 20, but also controls the upper limit temperature Ta of the secondary battery 20, which is the temperature at which it is determined whether or not the secondary battery 20 is at risk of reaching an overheating state.

[0042] For example, if the calculated amount of Li deposited is small, the control unit 14 maintains the upper limit temperature Ta of the secondary battery 20 as it is, because the resistance to overheating of the secondary battery 20 is maintained at a high value. However, as the calculated amount of Li deposited increases, the resistance to overheating of the secondary battery 20 decreases, so the control unit 14 lowers the upper limit temperature Ta of the secondary battery 20. In addition, the control unit 14 may gradually lower the upper limit temperature Ta of the secondary battery 20 as the amount of Li deposited increases, for example, from the initial value of 130 degrees, 120 degrees, and 110 degrees.

[0043] As a result, the battery management device 10 according to this disclosure can accurately prevent overheating of the secondary battery 20. The control unit 14 may individually control the upper limit temperature Ta of each of the multiple battery cells constituting the secondary battery 20 based on the amount of Li deposited in each of the multiple battery cells. In this case, the control unit 14 controls the upper limit temperature Ta of the battery cell to decrease as the calculated amount of Li deposited in the battery cell increases.

[0044] (Operation of battery management device 10) Next, we will explain the operation of the battery management device 10 using Figure 5. Figure 5 is a flowchart showing the operation of the battery management device 10.

[0045] First, the battery management device 10 supplies the secondary battery 20 with an AC signal (high-frequency signal) of such a high frequency that the diffusion, reaction, and movement of lithium ions in each battery cell cannot keep up (step S101). For example, the battery management device 10 supplies the secondary battery 20 with a high-frequency signal of 0.1 MHz or higher. Then, the battery management device 10 detects the value of the real part Z of the AC impedance from the secondary battery 20 to which the high-frequency signal has been supplied (step S102).

[0046] Subsequently, the battery management device 10 calculates the amount of Li deposited in the secondary battery 20 from 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 map information stored in the storage unit 15. Basically, the larger the detected value of the real part Z of the AC impedance, the smaller the value of Li deposited that the battery management device 10 calculates, and the smaller the detected value of the real part Z of the AC impedance, the larger the value of Li deposited that the battery management device 10 calculates.

[0047] Subsequently, the battery management device 10 controls the allowable charging power Pa for the secondary battery 20 based on the calculated amount of Li deposition (step S104). For example, if the calculated amount of Li deposition is small, the battery management device 10 maintains the allowable charging power Pa at its current level or controls it to be higher, as the progress of Li deposition is suppressed. If the calculated amount of Li deposition is large, it is necessary to suppress the progress of Li deposition, so the battery management device 10 controls it to be lowered.

[0048] Furthermore, the battery management device 10 controls the upper limit temperature Ta of the secondary battery 20, which is the temperature at which it determines whether or not the secondary battery 20 is at risk of overheating, based on the calculated amount of Li deposited (step S105). For example, if the calculated amount of Li deposited is small, the battery management device 10 maintains the upper limit temperature Ta of the secondary battery 20 as it is, because the resistance to overheating of the secondary battery 20 is maintained at a high value. However, as the calculated amount of Li deposited increases, the resistance to overheating of the secondary battery 20 decreases, so the upper limit temperature Ta of the secondary battery 20 is lowered.

[0049] Thus, the battery management device 10 according to this disclosure can set the allowable charging power Pa of the secondary battery 20 to the highest possible value, which allows for efficient charging in the shortest possible charging time while suppressing Li deposition. In other words, 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 excessively low, thereby enabling efficient charging of the secondary battery 20.

[0050] Furthermore, the battery management device 10 according to this disclosure can accurately prevent overheating of a lithium-ion secondary battery by controlling the upper limit temperature Ta of the lithium-ion secondary battery (a temperature that serves as a criterion for determining whether or not the lithium-ion secondary battery is at risk of reaching an overheated state) according to the amount of Li deposition, taking into consideration the decrease in the lithium-ion secondary battery's resistance to overheating due to Li deposition.

[0051] In this disclosure, the case in which the temperature detection unit 16 detects the secondary battery 20 using the thermistor T1 and each cell voltage has been described as an example, but the invention is not limited thereto. For example, instead of detecting the temperature of the secondary battery 20, the temperature detection unit 16 may be configured to detect the battery temperature of the thermistor T1. In this case, the control unit 14 gradually lowers the upper limit temperature Ta of the secondary battery 20 by gradually lowering the battery temperature of the thermistor T1 to, for example, an initial value of 60 degrees, 55 degrees, and 50 degrees, as the amount of Li deposition increases.

[0052] Furthermore, this disclosure can be realized by having a Central Processing Unit (CPU) execute a computer program to perform some or all of the processing of the battery management device 10.

[0053] The program described above includes, when loaded into a computer, a set of instructions (or software code) for causing the computer to perform one or more of the functions described in the embodiments. The program may be stored in a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include Random-Access Memory (RAM), Read-Only Memory (ROM), flash memory, Solid-State Drive (SSD), or other memory technologies, CD-ROM, Digital Versatile Disc (DVD), Blu-ray® disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include temporary computer-readable medium or a communication medium that includes electrically, optically, acoustically, or otherwise propagating signals.

[0054] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate. [Explanation of Symbols]

[0055] 1. Battery Management System 10 Battery management device 11. High-frequency signal supply unit 12 Impedance detection unit 13 Calculation Section 14 Control Unit 15 Storage section 16 Temperature detection unit 20 Secondary battery T1 Thermistor

Claims

1. A temperature detection unit for detecting the temperature of a lithium-ion secondary battery, A high-frequency signal supply unit that supplies a high-frequency signal of 0.1 MHz or higher to the lithium-ion secondary battery, An impedance detection unit that detects the real part value of the AC impedance from a lithium-ion secondary battery to which the aforementioned high-frequency signal is supplied, A calculation unit that calculates the amount of Li deposited in the lithium-ion secondary battery from the real value of the detected AC impedance, A control unit controls the allowable charging power for the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery, and also controls the upper limit temperature of the lithium-ion secondary battery, which is the temperature at which it is determined whether or not the lithium-ion secondary battery is at risk of overheating. A battery management device equipped with this device.

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

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

4. The control unit controls 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 also controls the lithium-ion secondary battery so that the upper limit temperature decreases. The battery management device according to claim 1.

5. The control unit controls the upper limit temperature of each of the stacked battery cells constituting the lithium-ion secondary battery based on the amount of Li deposited in each of the stacked battery cells. The battery management device according to claim 1.

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

7. The temperature detection unit has one or more thermistors that detect the temperature of one or more of the plurality of battery cells. Based on the detection results of one or more thermistors and the cell voltages of each of the plurality of battery cells, the temperature of each of the plurality of battery cells is estimated. The battery management device according to claim 5.

8. A high-frequency signal of 0.1 MHz or higher is supplied to a lithium-ion secondary battery. The real part of the AC impedance is detected from the lithium-ion secondary battery to which the aforementioned high-frequency signal is supplied. From the real part value of the detected AC impedance, the amount of Li deposited in the lithium-ion secondary battery is calculated. Based on the calculated amount of Li deposited in the lithium-ion secondary battery, the permissible charging power for the lithium-ion secondary battery is controlled. Based on the calculated amount of Li deposited in the lithium-ion secondary battery, the upper limit temperature of the lithium-ion secondary battery is controlled, which is the temperature at which it is determined whether or not the lithium-ion secondary battery is at risk of overheating. Battery management method for a battery management device.

9. A process for supplying a high-frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery, A process for detecting the real part value of the AC impedance from a lithium-ion secondary battery to which the aforementioned high-frequency signal is supplied, A process to calculate the amount of Li deposited in the lithium-ion secondary battery from the real part value of the detected AC impedance, A process to control the allowable charging power for the lithium-ion secondary battery based on the calculated amount of Li deposited in the lithium-ion secondary battery, A process to control the upper limit temperature of the lithium-ion secondary battery, which is the temperature at which it is determined whether or not the lithium-ion secondary battery is at risk of overheating, based on the calculated amount of Li deposited in the lithium-ion secondary battery, A control program that causes a computer to execute a command.

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