Battery Management Device

Abstract

To provide a battery management device that can suppress the risk of prolonged charging times. [Solution] The battery management device 10 according to this disclosure includes an acquisition unit 16 that acquires a degradation evaluation value for evaluating the progress of the high-rate degradation state of a lithium-ion secondary battery; a high-frequency signal supply unit 11 that supplies a high-frequency signal with a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; a detection unit that detects 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 13 that calculates the amount of Li deposited in the lithium-ion secondary battery from the detected real value of the AC impedance; and a control unit 14 that lowers the upper limit degradation evaluation value of the lithium-ion secondary battery, which is a criterion for determining whether or not the lithium-ion secondary battery is likely to reach a high-rate degradation state, as the calculated amount of Li deposited increases.

Description

Technical Field

[0001] The present disclosure relates to a battery management device.

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, 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 calculating the amount of Li precipitation in a lithium-ion secondary battery based on the difference between the current value and the initial value of the real part of the AC impedance of the lithium-ion secondary battery by detecting the real part of the AC impedance of the lithium-ion secondary battery using a high-frequency signal.

[0004] In a lithium-ion secondary battery, when charging and discharging are continuously performed at a large current (high-rate current), high-rate deterioration such as Li precipitation may occur. High-rate deterioration is a deterioration phenomenon in which the internal resistance of a lithium-ion secondary battery increases due to, for example, the concentration distribution of lithium ions inside the electrode body being biased. The ECU disclosed in Patent Document 2 calculates a "deterioration evaluation value ΣD" for evaluating the progress of high-rate deterioration of a lithium-ion secondary battery based on the bias of the lithium-ion concentration distribution. Then, the ECU executes control (high-rate deterioration suppression control) for suppressing the high-rate deterioration of the lithium-ion secondary battery according to the calculated deterioration evaluation value ΣD. For example, when the deterioration evaluation value ΣD exceeds the upper limit deterioration evaluation value (threshold value TH), the ECU suppresses charging of the lithium-ion secondary battery by reducing the allowable charging power (charging power control upper limit value (charging power upper limit value Win)) to the lithium-ion secondary battery.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 7347451 [Patent Document 2] Patent No. 7207343 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, the higher the upper limit degradation evaluation value, the less the charging of the lithium-ion secondary battery is suppressed, and the easier it is for Li to precipitate. Therefore, from the perspective of suppressing Li precipitate, an upper limit degradation evaluation value is set for each type of lithium-ion secondary battery. Here, the rate of Li precipitate progression in lithium-ion secondary batteries varies from product to product (e.g., standard deviation σ) even within the same type. In conventional lithium-ion secondary batteries, for example, the upper limit degradation evaluation value for each type was set excessively low (fixed) to prevent Li precipitate from progressing in products within the ±6σ range, which led to the problem of longer charging times.

[0007] This disclosure was made in view of the above-mentioned problems and provides a battery management device that can suppress the risk of prolonged charging time. [Means for solving the problem]

[0008] The battery management device related to this disclosure is An acquisition unit that acquires a degradation evaluation value to evaluate the degree of progression of high-rate degradation in lithium-ion secondary batteries, A high-frequency signal supply unit that supplies a high-frequency signal with a frequency of 0.1 MHz or higher to the lithium-ion secondary battery, A 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, The system includes a control unit that lowers the upper limit degradation evaluation value of the lithium-ion secondary battery, which is a criterion for determining whether or not the lithium-ion secondary battery is likely to reach a high-rate degradation state, as the calculated amount of Li deposition increases.

[0009] Furthermore, in the battery management device described above, the high-frequency signal supply unit may supply the lithium-ion secondary battery with a high-frequency signal of 0.5 MHz or higher.

[0010] Furthermore, in the battery management device described above, the control unit may restrict charging of the lithium-ion secondary battery when the degradation evaluation value of the lithium-ion secondary battery during charging reaches the upper limit degradation evaluation value.

[0011] Furthermore, in the battery management device described above, the control unit may control the lithium-ion secondary battery so that the allowable charging power decreases as the calculated amount of Li deposition in the lithium-ion secondary battery increases, and also control the lithium-ion secondary battery so that the upper limit degradation evaluation value decreases.

[0012] Furthermore, in the battery management device described above, the acquisition unit acquires a degradation evaluation value for evaluating the degree of progression of the high-rate degradation state of the lithium-ion secondary battery based on the behavior of the lithium-ion secondary battery's resistance, which temporarily occurs due to an uneven distribution of lithium ions within the lithium-ion secondary battery. When the control unit detects the temporary increase in the resistance of the lithium-ion secondary battery, it controls the charging of the lithium-ion secondary battery, The control unit may be controlled such that the upper limit degradation evaluation value decreases as the calculated amount of Li deposition in the lithium-ion secondary battery increases. [Effects of the Invention]

[0013] According to this disclosure, the risk of increased charging time can be suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] It is a block diagram showing a configuration example of a battery management device according to the first embodiment. [Figure 2] It is a diagram showing the relationship between the SOH of a secondary battery and the amount of change in the real part Z of the AC impedance when a 1 MHz high-frequency signal 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 a battery management method according to the first embodiment. [Figure 6] It is a block diagram showing a configuration example of a battery management system according to the second embodiment.

Embodiments for Carrying Out the Invention

[0015] 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.

[0016] (First Embodiment) FIG. 1 is a block diagram showing a configuration example of a battery management system according to the first embodiment. As shown in FIG. 1, the battery management system 100 includes a battery management device 10 and a secondary battery 20 managed by the battery management device 10.

[0017] <Configuration of Secondary Battery 20> First, the secondary battery 20 that is the management target will be described. The secondary battery 20 is a lithium-ion secondary battery and is composed of a cell stack consisting of a plurality of stacked battery cells and a case that houses the cell stack. Each battery cell includes 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.

[0018] 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.

[0019] 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.

[0020] 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 more of the following: carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes. Examples of carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, as well as 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.

[0021] Incidentally, in the secondary battery 20, repeated charging causes metallic Li to deposit on the electrode surface of each battery cell. 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.

[0022] Note that the State of Health (SOH) of the secondary battery 20 refers to the ratio of the current full charge capacity to the initial full charge capacity of the secondary battery 20, which is set to 100%. Therefore, it is desirable to control the high-rate charging and discharging of the secondary battery 20 while suppressing Li deposition.

[0023] <Configuration of Battery Management Device 10> Next, we will describe the battery management device 10 that manages the secondary battery 20. As shown in Figure 1, the battery management device 10 comprises 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 an acquisition unit 16, and manages the charging of the secondary battery 20 to be managed. The battery management device 10 calculates the amount of Li deposition in the secondary battery 20 and provides feedback control of the upper limit degradation evaluation value of the secondary battery 20 based on the calculation result. The upper limit degradation evaluation value of the secondary battery 20 is a criterion for determining whether or not the secondary battery 20 is likely to reach a high-rate degradation state.

[0024] Here, the battery management device 10 includes, as hardware, a storage unit 15 such as RAM (Random Access Memory) and ROM (Read Only Memory) that stores various programs and data, as well as a processing unit such as a CPU (Central Processing Unit) (not shown). In other words, the battery management device 10 has the functionality of a computer and performs various processes based on the above-mentioned programs.

[0025] Therefore, in Figure 1, the functional blocks constituting the battery management device 10—the high-frequency signal supply unit 11, impedance detection unit 12, calculation unit 13, control unit 14, storage unit 15, and acquisition unit 16—can be configured in hardware terms with a CPU (Central Processing Unit), memory, and other circuits, and in software terms with programs loaded into memory. In other words, each of the above functional blocks can be implemented in various forms using computer hardware, software, or combinations thereof.

[0026] The high-frequency signal supply unit 11 supplies a high-frequency signal to the secondary battery 20 for detecting the amount of Li deposition. More specifically, the high-frequency signal supply unit 11 supplies a high-frequency signal of 0.1 MHz or higher to the secondary battery 20. Preferably, the high-frequency signal is such that, compared to the value of the real part Z of the AC impedance detected when a 1 kHz AC signal is supplied to the secondary battery 20, the real part of the AC impedance is detected to be 10 times or more due to the skin effect. Specifically, the frequency of the high-frequency signal is preferably 0.5 MHz or higher.

[0027] When a high-frequency signal having such a frequency is supplied to the secondary battery 20, the diffusion, reaction, and movement of lithium ions in each battery cell of the secondary battery 20 cannot keep up. Therefore, the current of the high-frequency signal flows along the electrode surface of each battery cell, where Li is easily deposited, due to the skin effect.

[0028] If the SOH deteriorates without Li deposition from the initial state, i.e., a state where the amount of Li deposition is approximately 0 (zero), the real part Z of the AC impedance does not change. When Li is deposited, the real part Z of the AC impedance decreases. On the other hand, as the amount of Li deposition increases, the electrical conductivity of the electrode surface of each battery cell increases, so the value of the real part Z of the AC impedance decreases. 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 current collector foil and the conductive parts of the electrodes, but reduce the overall loss of the battery. Therefore, as the amount of Li deposition increases, the change in the magnetic field becomes larger, and as a result the eddy currents increase, so the value of the real part Z decreases. For this reason, the amount of Li deposition in the secondary battery 20 can be calculated from the change in the real part Z of the AC impedance detected from the secondary battery 20 to which a high-frequency signal is supplied (the difference between the detected value and the initial value). Furthermore, the SOH of the secondary battery 20 can also be estimated based on the amount of Li deposition.

[0029] Here, Figure 2 is a graph showing 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.

[0030] As shown by the triangles in Figure 2, in the case of normal charging with low charging power, the amount of Li deposition is small even if charging is repeated, 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. In other words, the detected value of the real part Z of the AC impedance is maintained at a high value.

[0031] On the other hand, as shown by the circles in Figure 2, in the case of rapid charging with high charging power, the amount of Li deposited 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. That is, 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 deposited can be derived from SOH. Alternatively, SOH can be derived from the amount of Li deposited.

[0032] Here, Figures 3 and 4 are graphs 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 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.

[0033] 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. This impedance component represents the ohmic resistance component. Furthermore, as shown in Figures 3 and 4, the higher the frequency of the AC signal supplied to the secondary battery 20, the greater the real part Z of the AC impedance becomes due to the skin effect, which concentrates the current flow on the electrode surface of each cell.

[0034] 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.

[0035] The impedance detection unit 12 detects the real part Z of the AC impedance from the secondary battery 20 to which a high-frequency signal is supplied. As described above, the current of the high-frequency signal supplied from the high-frequency signal supply unit 11 to the secondary battery 20 flows through the electrode surface (Li deposition region) of each battery cell of the secondary battery 20 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 over the Li metal due to inductive coupling and electric field coupling. Therefore, the impedance detection unit 12 can detect the real part Z of the AC impedance according to the amount of Li deposition.

[0036] 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. Specifically, the calculation unit 13 calculates a smaller amount of Li deposited the larger the detected value of the real part Z of the AC impedance and the smaller the difference from the initial value. On the other hand, the calculation unit 13 calculates a larger amount of Li deposited the smaller the detected value of the real part Z of the AC impedance and the larger the difference from the initial value.

[0037] For example, the memory unit 15 stores the initial value of the real part Z of the AC impedance of the secondary battery 20 being managed. The memory unit 15 may also store map information that shows the relationship between the current value (detected value) and the initial value of the real part Z of the AC impedance of each type of secondary battery, and the amount of Li deposition.

[0038] This map information is, for example, information obtained in advance through experiments, but it may be updated as appropriate with information detected from the secondary battery 20 under management. When using the map information, 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 storage unit 15.

[0039] The acquisition unit 16 acquires a degradation evaluation value ΣD to evaluate the degree of high-rate degradation of the secondary battery 20. The acquisition unit 16 can acquire the degradation evaluation value ΣD by calculating it using the voltage, current, and temperature of the secondary battery 20. The acquisition unit 16 may be equipped with sensors to detect the voltage, current, and temperature of the secondary battery 20. Alternatively, the acquisition unit 16 may acquire the voltage, current, and temperature of the secondary battery 20 from an integrated ECU or battery ECU (Electronic Control Unit) via an in-vehicle network. The acquisition unit 16 may also acquire the temperature of the secondary battery 20 from a thermistor. Specifically, the acquisition unit 16 may acquire a degradation evaluation value to evaluate the degree of high-rate degradation of the secondary battery 20 based on the behavior of increased resistance in the secondary battery 20 that occurs temporarily due to an uneven distribution of lithium ion concentration inside the secondary battery 20.

[0040] The control unit 14 executes control (high-rate degradation suppression control) to suppress high-rate degradation of the secondary battery 20 according to the degradation evaluation value ΣD acquired by the acquisition unit 16. If the degradation evaluation value ΣD exceeds the upper limit degradation evaluation value of the secondary battery 20, the control unit 14 reduces the allowable charging power to the secondary battery 20.

[0041] As a result, the battery management device 10 according to this disclosure can set the highest possible upper limit degradation evaluation value 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 upper limit degradation evaluation value of the secondary battery 20 to an appropriate value according to the amount of Li deposition, without setting it excessively low. Therefore, the risk of prolonged charging time can be suppressed. Furthermore, efficient charging of the secondary battery 20 can be achieved.

[0042] <Battery management method> Next, with reference to Figure 5, the operation of the battery management method, or battery management device 10, according to this embodiment will be described. Figure 5 is a flowchart of the battery management method according to the first embodiment.

[0043] First, the battery management device 10 obtains a degradation evaluation value ΣD (step S101). For example, the battery management device 10 obtains this value by detecting the voltage, current, and temperature of the secondary battery 20 and calculating the degradation evaluation value ΣD using the detected voltage, current, and temperature.

[0044] Next, 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 S102). For example, the high-frequency signal supply unit 11 supplies the secondary battery 20 with a high-frequency signal of 0.1 MHz or higher.

[0045] Next, the battery management device 10 detects the value of the real part Z of the AC impedance from the secondary battery 20 to which a high-frequency signal is supplied (step S103).

[0046] Next, 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 S104). 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] Finally, the battery management device 10 controls the upper limit degradation evaluation value of the secondary battery 20 based on the calculated amount of Li deposition (step S105). For example, if the calculated amount of Li deposition is small, the battery management device 10 controls the upper limit degradation evaluation value to either maintain it at its current level or increase it, because the progress of Li deposition is being suppressed. If the calculated amount of Li deposition is large, the battery management device 10 controls the upper limit degradation evaluation value of the secondary battery 20 to decrease, because it is necessary to suppress the progress of Li deposition.

[0048] Thus, the battery management device 10 according to this disclosure can set the highest possible upper limit degradation evaluation value 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 upper limit degradation evaluation value of the secondary battery 20 to an appropriate value according to the amount of Li deposition, without setting it excessively low. Therefore, the risk of prolonged charging time can be suppressed. Furthermore, efficient charging of the secondary battery 20 can be achieved.

[0049] Furthermore, the control unit 14 controls the upper limit degradation evaluation value of the secondary battery 20 based on the amount of Li deposition calculated by the calculation unit 13. Specifically, the control unit 14 controls the upper limit degradation evaluation value of the secondary battery 20 to decrease as the amount of Li deposition calculated by the calculation unit 13 increases, as it becomes necessary to suppress the progression of Li deposition. As a result, when the upper limit degradation evaluation value of the secondary battery 20 decreases, the degradation evaluation value ΣD is more likely to exceed the upper limit degradation evaluation value of the secondary battery 20. Therefore, the control unit 14 reduces the allowable charging power to the secondary battery 20. This suppresses high-rate charging and discharging of the secondary battery 20. As a result, Li deposition in the secondary battery 20 can be suppressed.

[0050] Furthermore, the control unit 14 may limit the charging of the secondary battery 20 if the degradation evaluation value ΣD of the secondary battery 20 during charging reaches the upper limit degradation evaluation value. Specifically, the control unit 14 may stop charging the secondary battery 20. This stops charging of the lithium-ion secondary battery that may reach a high-rate state, thereby protecting the lithium-ion secondary battery from high-rate degradation.

[0051] Furthermore, the control unit 14 may control the secondary battery 20 so that the allowable charging power decreases as the amount of Li deposition calculated by the calculation unit 13 increases, and also so that the upper limit degradation evaluation value of the secondary battery 20 decreases. This allows for control of the allowable charging power and the upper limit degradation evaluation value in accordance with the increase in the amount of Li deposition, thereby strengthening protection against high-rate degradation.

[0052] Furthermore, in this embodiment, the acquisition unit 16 acquires a degradation evaluation value that evaluates the degree of progression of the high-rate degradation state of the secondary battery 20 based on the behavior of the secondary battery 20's resistance temporarily increasing due to an uneven distribution of lithium ion concentration inside the secondary battery 20. When the control unit 14 detects the temporary increase in the resistance of the secondary battery 20, it controls the charging of the secondary battery 20, and the control unit 14 should control the upper limit degradation evaluation value to decrease as the amount of Li deposition calculated by the calculation unit 13 increases. This makes it possible to strengthen protection against high-rate degradation while limiting the charging of a lithium-ion secondary battery that may reach a high-rate state while its resistance increases for a short time.

[0053] <Embodiment 2> Figure 6 is a block diagram showing an example configuration of the battery management system 200 according to Embodiment 2. The battery management system 200 comprises n battery management devices 10, each corresponding to n (where n is an integer of 2 or more) secondary batteries 20, a control device 40, and a network 50. The n battery management devices 10 and the control device 40 are configured to communicate with each other via the network 50. Hereinafter, the n secondary batteries 20 will also be referred to as secondary batteries 20_1 to 20_n, and the n battery management devices 10 will also be referred to as battery management devices 10_1 to 10_n.

[0054] The secondary batteries 20_1 to 20_n are installed in vehicles 30_1 to 30_n, respectively. The battery management devices 10_1 to 10_n are also installed in vehicles 30_1 to 30_n together with the secondary batteries 20_1 to 20_n. All of the vehicles 30_1 to 30_n are electric vehicles or hybrid vehicles powered by secondary batteries.

[0055] The control device 40 switches the control settings for the upper limit degradation evaluation value for each of the secondary batteries 20_1 to 20_n, according to the status of the upper limit degradation evaluation value limits set for each of the secondary batteries 20_1 to 20_n managed by the battery management devices 10_1 to 10_n. Specifically, the control device 40 learns the settings for the upper limit degradation evaluation value set for each of the secondary batteries 20_1 to 20_n, managed by the battery management devices 10_1 to 10_n, and updates the settings for the upper limit degradation evaluation value set for each of the secondary batteries 20_1 to 20_n based on the learning results. In other words, the control device 40 updates the settings for the upper limit degradation evaluation value set for each of the secondary batteries 20_1 to 20_n using a trained model generated by machine learning using the settings for the upper limit degradation evaluation value.

[0056] For example, if a predetermined number of secondary batteries 20 managed by a predetermined number of battery management devices 10_1 to 10_n have a lower-than-expected upper limit degradation evaluation value set after a predetermined period of use, the initial value of the upper limit degradation evaluation value may be too high. In such a case, the control device 40 controls all secondary batteries 20_1 to 20_n managed by battery management devices 10_1 to 10_n to lower the upper limit degradation evaluation value. This suppresses the progression of Li deposition in each secondary battery 20_1 to 20_n. The control device 40 may also set the initial value of the upper limit degradation evaluation value set for newly shipped secondary batteries 20 to a low value, similar to the case of secondary batteries 20_1 to 20_n.

[0057] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. Furthermore, the present invention may be implemented by combining the above embodiments or examples thereof as appropriate. [Explanation of symbols]

[0058] 100, 200 Battery Management System 10, 10_1~10_n Battery management device 11. High-frequency signal supply unit 12 Impedance detection unit 13 Calculation Section 14 Control Unit 15 Storage section 16 Acquisition Department 20, 20_1~20_n secondary battery 30_1~30_n Vehicles 40 Control device 50 Networks

Claims

1. An acquisition unit that acquires a degradation evaluation value to evaluate the degree of progression of high-rate degradation in lithium-ion secondary batteries, A high-frequency signal supply unit that supplies a high-frequency signal with a frequency of 0.1 MHz or higher to the lithium-ion secondary battery, A 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, The system includes a control unit that lowers the upper limit degradation evaluation value of the lithium-ion secondary battery, which is a criterion for determining whether or not the lithium-ion secondary battery is likely to reach a high-rate degradation state, as the calculated amount of Li deposition increases. Battery management 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 charging of the lithium-ion secondary battery when the degradation evaluation value of the lithium-ion secondary battery during charging reaches the upper limit degradation evaluation value. The battery management device according to claim 1 or 2.

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 degradation evaluation value decreases. The battery management device according to claim 1 or 2.

5. The acquisition unit acquires a degradation evaluation value for evaluating the degree of progression of the high-rate degradation state of the lithium-ion secondary battery, based on the behavior of the lithium-ion secondary battery's resistance temporarily increasing due to the bias in the lithium-ion concentration distribution inside the lithium-ion secondary battery. When the control unit detects the temporary increase in the resistance of the lithium-ion secondary battery, it controls the charging of the lithium-ion secondary battery, The control unit controls the system so that the upper limit degradation evaluation value decreases as the calculated amount of Li deposition in the lithium-ion secondary battery increases. The battery management device according to claim 1 or 2.

Images