Vehicles, ECUs, systems, and detection devices

Abstract

To provide a vehicle, ECU, system, and detection device that can suppress the risk of reduced accuracy in measuring the amount of Li deposited in lithium-ion secondary batteries. [Solution] The vehicle 300 according to this disclosure comprises a lithium-ion secondary battery and a detection device 10. The detection device 10 comprises 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, an acquisition unit 16 that acquires vehicle state information indicating the state of the vehicle 300, and a determination unit 17 that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information. If the determination unit 17 determines that the state of the vehicle 300 is in a predetermined state, the detection unit detects the real value of the AC impedance.

Description

Technical Field

[0001] The present disclosure relates to a vehicle, an ECU, a system, and a detection 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 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] Depending on the state of the vehicle, the impedance measurement accuracy may decrease. Therefore, the measurement accuracy of the amount of Li precipitation in the lithium-ion secondary battery may decrease.

[0006] The present disclosure has been made in view of the above-described problems, and provides a vehicle, an ECU, a system, and a detection device capable of suppressing the risk of a decrease in the measurement accuracy of the amount of Li precipitation in a lithium-ion secondary battery.

Means for Solving the Problems

[0007] The vehicle related to this disclosure is A vehicle equipped with a lithium-ion secondary battery and a detection device, The detection device is 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 the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle status information indicating the status of the vehicle, The system includes a determination unit that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information, If the determination unit determines that the vehicle is in a predetermined state, the detection unit may detect the value of the real part of the AC impedance.

[0008] Furthermore, in the vehicle described above, the vehicle status information is vehicle noise information indicating vehicle noise that may affect the impedance measurement accuracy of the lithium-ion secondary battery, and the determination unit may determine, based on the vehicle noise information, whether or not the effect of the vehicle noise on the impedance measurement accuracy of the lithium-ion secondary battery is minor.

[0009] Furthermore, in the vehicle described above, the vehicle is equipped with a motor that drives the wheels, and the determination unit may determine that the state of the vehicle is a predetermined state when the motor is stopped.

[0010] Furthermore, in the vehicle described above, the vehicle is equipped with an AC / DC converter that converts AC current from an external AC power source into DC current. The determination unit may determine that the vehicle is in a predetermined state if the switching frequency of the AC / DC converter is within a specific range while the lithium-ion secondary battery is supplied with power by the DC current.

[0011] Furthermore, in the vehicle described above, the determination unit may determine that the state of the vehicle is in a predetermined state if the temperature of the lithium-ion secondary battery is within a specific range.

[0012] Furthermore, in the vehicle described above, the determination unit may determine that the state of the vehicle is in a predetermined state if the State of Charge (SOC) of the lithium-ion secondary battery is within a specific range.

[0013] Furthermore, in the vehicle described above, the determination unit may determine that the state of the vehicle is in a predetermined state if the voltage of the battery cells of the lithium-ion secondary battery is within a specific range.

[0014] Furthermore, in the vehicle described above, the determination unit may determine that the state of the vehicle is in a predetermined state if the vehicle is driven after the lithium-ion secondary battery has been charged by being supplied with power from an external DC power source using a DC current.

[0015] The ECU relating to this disclosure is An ECU that can be installed in a vehicle equipped with a lithium-ion secondary battery, The aforementioned ECU is 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 the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle status information indicating the status of the vehicle, The system includes a determination unit that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information, If the determination unit determines that the vehicle is in a predetermined state, the detection unit detects the value of the real part of the AC impedance.

[0016] The system related to this disclosure is A system that can be mounted on a vehicle, Lithium-ion rechargeable batteries, A detection device, The detection device A high-frequency signal supply unit that supplies a high-frequency signal with a frequency of 0.1 MHz or more to the lithium-ion secondary battery, A detection unit that detects the value of the real part of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle state information indicating the state of the vehicle, A determination unit that determines whether or not the state of the vehicle is a predetermined state based on the vehicle state information, [[ID=I1]] When the determination unit determines that the state of the vehicle is a predetermined state, the detection unit detects the value of the real part of the AC impedance.

[0017] The detection device according to the present disclosure A detection device that can be mounted on a vehicle equipped with a lithium-ion secondary battery, A high-frequency signal supply unit that supplies a high-frequency signal with a frequency of 0.1 MHz or more to the lithium-ion secondary battery, A detection unit that detects the value of the real part of the AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle state information indicating the state of the vehicle, A determination unit that determines whether or not the state of the vehicle is a predetermined state based on the vehicle state information, When the determination unit determines that the state of the vehicle is a predetermined state, the detection unit detects the value of the real part of the AC impedance. [[ID=2I]]

Advantages of the Invention

[0018] According to the present disclosure, it is possible to suppress the possibility that the measurement accuracy of the Li precipitation amount in the lithium-ion secondary battery decreases.

Brief Description of the Drawings

[0019] [Figure 1] It is a block diagram showing the configuration of a vehicle according to the first embodiment. [Figure 2]This figure shows the relationship between the State of Health (SOH) of a secondary battery and the 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] This diagram shows 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. [Figure 4] This diagram shows 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. [Figure 5] This is a flowchart showing the detection method according to the first embodiment. [Figure 6] This block diagram shows the configuration of the ECU according to the second embodiment. [Modes for carrying out the invention]

[0020] Specific embodiments of the present invention will be described in detail below 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 have been simplified as appropriate.

[0021] (First embodiment) Figure 1 is a block diagram showing an example configuration of the system according to the first embodiment. As shown in Figure 1, the system 200 can be mounted on a vehicle 300. The system 200 comprises a detection device 10 and a secondary battery 20. The detection device 10 can detect the impedance of the secondary battery 20.

[0022] Vehicle 300 can be equipped with an inverter 30, a motor 40, wheels 41, and a charger 50. Vehicle 300 may also be equipped with a motor ECU and a charger ECU (not shown). The motor ECU controls the inverter 30 and the motor 40. The charger ECU controls the charger 50. The secondary battery 20 supplies direct current to the inverter 30. The inverter 30 is preferably a three-phase inverter. The inverter 30 converts the direct current to alternating current and supplies the alternating current to the motor 40. The motor 40 uses this supplied alternating current to rotate the wheels 41. The charger 50 is equipped with an AC / DC converter 51 and may be equipped with diodes and capacitors as appropriate. The charger 50 is supplied with a single-phase alternating current of 100V or 200V from an external AC power source, such as a household power supply. The AC / DC converter 51 converts this supplied alternating current to direct current. The charger 50 supplies this converted DC current to the secondary battery 20. The secondary battery 20 is charged by receiving power in the form of AC current from an external AC power source. This type of charging is called normal charging. On the other hand, the secondary battery 20 can also be charged by receiving power in the form of DC current from an external power supply facility such as a charging station. This type of charging is called fast charging. The charging speed of fast charging is higher than that of normal charging.

[0023] <Configuration of secondary battery 20> First, let's explain the secondary battery 20 that is the target of detection. 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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%.

[0029] <Configuration of detection device 10> Next, the detection device 10 will be described. As shown in Figure 1, the detection 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, an acquisition unit 16, and a determination unit 17. The detection device 10 may further include a temperature detection unit 18. The detection device 10 detects the impedance of the secondary battery 20 to be detected. The detection device 10 calculates the amount of Li deposited in the secondary battery 20.

[0030] Here, the detection 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 detection device 10 has the functionality of a computer and performs various processes based on the above-mentioned programs.

[0031] Therefore, the functional blocks constituting the detection device 10 in Figure 1—the high-frequency signal supply unit 11, impedance detection unit 12, calculation unit 13, control unit 14, acquisition unit 16, determination unit 17, and temperature detection unit 18—can be configured in hardware terms with a CPU (Central Processing Unit), memory, and other circuits, and in software terms with a program loaded into memory. In other words, each of the above functional blocks can be realized in various forms by computer hardware, software, or combinations thereof. The detection device 10 can preferably be mounted on a circuit board, for example, and may be built into an ECU (Electronic Control Unit). The detection device 10 may also be a standalone device that can be attached to and detached from the vehicle 300. The impedance detection unit 12 may include a resonant circuit.

[0032] 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.

[0033] 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.

[0034] The less Li is deposited, the lower the electrical conductivity of the electrode surface of each battery cell, resulting in a larger real part Z value of the AC impedance. On the other hand, the more Li is deposited, the higher the electrical conductivity of the electrode surface of each battery cell, resulting in a smaller real part Z value 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 current collector foil and the conductive parts of the electrodes, but reduce the overall loss of the battery. Therefore, the more Li is deposited, the greater the change in the magnetic field and the larger the eddy currents, resulting in a smaller real part Z value. Thus, the amount of Li deposited 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 deposited.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The acquisition unit 16 acquires vehicle status information indicating the state of the vehicle 300. The vehicle status information is, for example, vehicle noise information indicating vehicle noise that may affect the impedance measurement accuracy of the secondary battery 20. The vehicle noise information includes, for example, the stopping of the motor 40, the switching frequency of the inverter 30 and AC / DC converter 51, the temperature of the secondary battery 20, SOC (State of Charge), the voltage of the battery cells, and the usage history.

[0042] The acquisition unit 16 may acquire vehicle status information from an ECU mounted on the vehicle 300 via an in-vehicle network. The ECUs are, for example, an integrated ECU, a motor ECU, a battery ECU, and a charger ECU. For example, the acquisition unit 16 may acquire the stopped state of the motor 40 and the switching high frequency of the inverter 30 from the motor ECU mentioned above. The acquisition unit 16 may acquire the switching high frequency of the AC / DC converter 51 from the charger ECU mentioned above. The acquisition unit 16 may acquire the temperature, SOC, and usage history of the secondary battery 20 from the battery ECU mentioned above. For example, the acquisition unit 16 may acquire the temperature of the secondary battery 20 from the temperature detection unit 18. The acquisition unit 16 may also measure the current flowing through the secondary battery 20, and the battery ECU mentioned above may calculate the SOC of the secondary battery 20 based on this measured current. As for the method of calculating SOC, a method using current integration (Coulomb count) or a method using open circuit voltage estimation can be used.

[0043] The determination unit 17 determines, based on the vehicle status information, whether the state of the vehicle 300 is in a predetermined state. If the vehicle status information is vehicle noise information, the determination unit 17 determines, based on the vehicle noise information, whether the influence of the vehicle noise on the impedance measurement accuracy of the secondary battery 20 is minor.

[0044] Specifically, the determination unit 17 may determine that the state of the vehicle 300 is a predetermined state if the motor 40 is stopped. The determination unit 17 may determine that the state of the vehicle 300 is a predetermined state based on whether the motor 40 is stopped or not, depending on the shutdown of the inverter 30, the switching high frequency of the inverter 30, or the rotational speed of the motor 40.

[0045] More specifically, the determination unit 17 may determine that the state of the vehicle 300 is in a predetermined state if the inverter 30 is shut down, the inverter 30 has stopped generating switching high frequencies, or the rotational speed of the motor 40 is below a predetermined value.

[0046] Similarly, the determination unit 17 may determine that the state of the vehicle 300 is a predetermined state if the switching control of the inverter 30 is stopped. The determination unit 17 may also determine that the state of the vehicle 300 is a predetermined state if the shift range of the vehicle 300 is in the N range (neutral range). The determination unit 17 may also determine that the state of the vehicle 300 is a predetermined state if the vehicle 300 is being charged or supplied with power via a plug-in method. Here, charging via a plug-in method includes, for example, the normal charging and rapid charging described above. Power supply via a plug-in method includes, for example, power supply from the vehicle 300 to home appliances (V2L: Vehicle to Load) and power supply from the vehicle 300 to a building (V2H: Vehicle to Home). The determination unit 17 may also determine that the state of the vehicle 300 is a predetermined state if the air conditioning control device of the vehicle 300 is performing pre-air conditioning control. Furthermore, if the air conditioning control device of vehicle 300 is performing pre-air conditioning control, the engine of vehicle 300 may be running or stopped.

[0047] Furthermore, the determination unit 17 may determine that the state of the vehicle 300 is a predetermined state if, while the secondary battery 20 is supplied with power by the DC current converted by the AC / DC converter 51, the switching frequency of the AC / DC converter 51 is within a specific range. This specific range should be determined so as not to cause interference between the switching high frequency of the AC / DC converter 51 and the high-frequency signal from the high-frequency signal supply unit 11.

[0048] Furthermore, the determination unit 17 may determine that the state of the vehicle 300 is a predetermined state if the temperature of the secondary battery 20 is within a specific range. The resistance value of the battery cells of the secondary battery 20 changes with the temperature of the secondary battery 20. When the resistance value of the battery cells of the secondary battery 20 is high, the impedance measurement accuracy of the secondary battery 20 tends to be higher. Therefore, the specific range of temperature for the secondary battery 20 should be determined based on the relationship between the temperature and resistance value of the battery cells of the secondary battery 20, so that the impedance measurement accuracy of the secondary battery 20 maintains the required accuracy.

[0049] Furthermore, the determination unit 17 may determine that the state of the vehicle 300 is in a predetermined state if the state of charge (SOC) of the secondary battery 20 is within a specific range. The resistance value of the battery cells of the secondary battery 20 changes depending on the SOC of the secondary battery 20. As described above, when the resistance value of the battery cells of the secondary battery 20 is high, the impedance measurement accuracy of the secondary battery 20 tends to be higher. Therefore, the specific range of the SOC of the secondary battery 20 should be determined based on the relationship between the SOC and resistance value of the battery cells of the secondary battery 20, so that the impedance measurement accuracy of the secondary battery 20 maintains the required accuracy.

[0050] Furthermore, the determination unit 17 may determine that the vehicle is in a predetermined state if the voltage of the battery cells of the secondary battery 20 is within a specific range. The impedance measurement accuracy of the secondary battery 20 changes depending on the voltage of the battery cells of the secondary battery 20. The relationship between the impedance measurement accuracy of the secondary battery 20 and the voltage of the battery cells of the secondary battery 20 can be determined by conducting experiments. Therefore, the specific range of the voltage of the battery cells of the secondary battery 20 should be determined so that the impedance measurement accuracy of the secondary battery 20 maintains the required accuracy.

[0051] Furthermore, the determination unit 17 may determine that the state of the vehicle 300 is in a predetermined state if the vehicle 300 is driven after the secondary battery 20 has been charged by being supplied with power from an external DC power source. The resistance value and electromotive force of the battery cells of the secondary battery 20 change depending on the usage history of the secondary battery 20, which affects the impedance measurement accuracy of the secondary battery 20. The impedance measurement accuracy of the secondary battery 20 can be improved by defining the usage history of the secondary battery 20, specifically the resistance value and voltage of the battery cells of the secondary battery 20. Specifically, the usage history of the secondary battery 20 is defined as the current flowing through the secondary battery 20 being within ±B1 amperes within a predetermined period A1 seconds. A1 and B1 are any values ​​greater than or equal to 0 (zero).

[0052] The specific ranges for the switching frequency of the AC / DC converter 51, the temperature of the secondary battery 20, the SOC, and the voltage of the battery cells may be calculated from the principles, or they may be determined experimentally or empirically.

[0053] The control unit 14 starts or stops the detection of the impedance of the secondary battery 20 by the impedance detection unit 12, according to the determination result of the determination unit 17. If the vehicle status information is vehicle noise information and the determination unit 17 determines that the effect of the vehicle noise on the impedance measurement accuracy of the secondary battery 20 is minor, the control unit 14 starts the detection of the impedance of the secondary battery 20 by the impedance detection unit 12. If the determination unit 17 determines that the effect of the vehicle noise on the impedance measurement accuracy of the secondary battery 20 is not minor, the control unit 14 stops the detection of the impedance of the secondary battery 20 by the impedance detection unit 12.

[0054] 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.

[0055] 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.

[0056] For example, the memory unit 15 stores the initial value of the real part Z of the AC impedance of the secondary battery 20 that is to be detected. 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.

[0057] 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 to be detected. 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.

[0058] The temperature detection unit 18 detects the temperature of the secondary battery 20. For example, the temperature detection unit 18 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.

[0059] <Detection and control method> Next, with reference to Figure 5, the operation of the detection method, or detection device 10, according to this embodiment will be described. Figure 5 is a flowchart of the detection method according to the first embodiment.

[0060] First, the detection 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 high-frequency signal supply unit 11 supplies the secondary battery 20 with a high-frequency signal of 0.1 MHz or higher.

[0061] Next, the detection device 10 acquires vehicle status information (step ST102). Vehicle status information includes, for example, vehicle noise information. Vehicle noise information includes, for example, the stop status of the motor 40, the switching frequency of the inverter 30 and AC / DC converter 51, the temperature of the secondary battery 20, the SOC, the voltage of the battery cells, and the usage history.

[0062] Next, the detection device 10 determines whether the state of the vehicle 300 is in a predetermined state based on the vehicle state information (step ST103).

[0063] If the detection device 10 determines that the state of the vehicle 300 is not in a predetermined state (step ST103: NO), it returns to step ST102 and the detection device 10 acquires the vehicle state information again.

[0064] If the detection device 10 determines that the vehicle is in a predetermined state (step ST103: YES), it 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 S104).

[0065] Finally, the detection device 10 calculates the amount of Li deposited in the secondary battery 20 from the real part Z value of the detected AC impedance (step S105). For example, the detection device 10 extracts the amount of Li deposited corresponding to the real part Z value of the detected AC impedance from the map information stored in the storage unit 15. Basically, the larger the real part Z value of the detected AC impedance, the smaller the amount of Li deposited calculated by the detection device 10, and the smaller the real part Z value of the detected AC impedance, the larger the amount of Li deposited calculated.

[0066] In this way, the detection device 10 detects the real part Z of the AC impedance from the secondary battery 20 to which a high-frequency signal is supplied when the vehicle 300 is in a predetermined state. Since the vehicle is in a predetermined state, the measurement conditions are constant, and the detection device 10 can suppress a decrease in the detection accuracy of the real part Z of the AC impedance. Therefore, the risk of a decrease in the measurement accuracy of the amount of Li deposited in the secondary battery 20 can be suppressed.

[0067] Furthermore, if the vehicle status information is vehicle noise information, the detection device 10 determines, based on the vehicle noise information, whether the impact of the vehicle noise on the impedance measurement accuracy of the secondary battery 20 is minor or not. If the impact of the vehicle noise on the impedance measurement accuracy of the secondary battery 20 is minor, the detection device 10 detects the real part Z value of the AC impedance from the secondary battery 20 to which the high-frequency signal is supplied. Therefore, the detection accuracy of the real part Z value of the AC impedance of the detection device 10 can be maintained. Thus, the decrease in the measurement accuracy of the amount of Li deposited in the secondary battery 20 can be suppressed.

[0068] Furthermore, in one specific example of this embodiment, the detection device 10 determines that the state of the vehicle 300 is a predetermined state when the motor 40 is stopped. When the motor 40 is stopped, the inverter 30 is also stopped and generates almost no switching high frequency. Therefore, interference between the switching high frequency of the inverter 30 and the high frequency signal from the high frequency signal supply unit 11 can be suppressed. Consequently, the detection accuracy of the real part Z value of the AC impedance of the detection device 10 can be maintained.

[0069] Furthermore, in one specific example of this embodiment, the detection device 10 determines that the state of the vehicle 300 is a predetermined state if the switching frequency of the AC / DC converter 51 is within a specific range while the secondary battery 20 is supplied with power by the DC current converted by the AC / DC converter 51. In such a case, interference between the switching high frequency of the AC / DC converter 51 and the high frequency signal from the high frequency signal supply unit 11 can be avoided. Therefore, the detection accuracy of the real part Z value of the AC impedance of the detection device 10 can be maintained.

[0070] Furthermore, in one specific example of this embodiment, the detection device 10 determines that the state of the vehicle 300 is a predetermined state when the temperature of the secondary battery 20 is within a specific range. The higher the resistance value of the battery cells of the secondary battery 20, the better the detection accuracy of the real part Z of the AC impedance of the detection device 10. Therefore, by determining the relationship between the temperature of the secondary battery 20 and the resistance value of the battery cells of the secondary battery 20, the influence of the temperature of the secondary battery 20 on the detection accuracy of the real part Z of the AC impedance of the detection device 10 can be calculated based on that relationship. It is preferable to set the specific range of the temperature of the secondary battery 20 so as to satisfy the required detection accuracy of the real part Z of the AC impedance of the detection device 10.

[0071] Furthermore, in one specific example of this embodiment, the detection device 10 determines that the state of the vehicle 300 is in a predetermined state if the State of Charge (SOC) of the secondary battery 20 is within a specific range. The higher the resistance value of the secondary battery 20, the better the detection accuracy of the detection device 10 in detecting the real part Z of the AC impedance. Therefore, by determining the relationship between the SOC of the secondary battery 20 and the resistance value of the battery cells of the secondary battery 20, the influence of the SOC of the secondary battery 20 on the detection accuracy of the detection device 10 in detecting the real part Z of the AC impedance can be calculated based on that relationship. It is preferable to set a specific range for the SOC of the secondary battery 20 so as to satisfy the required detection accuracy of the real part Z of the AC impedance of the detection device 10.

[0072] Furthermore, in one specific example of this embodiment, the detection device 10 determines that the state of the vehicle 300 is a predetermined state if the voltage of the battery cells of the secondary battery 20 is within a specific range. The voltage of the battery cells of the secondary battery 20 changes the amplitude, frequency, and resistance of the voltage waveform of the resonant circuit of the impedance detection unit 12, affecting the detection accuracy of the real part Z of the AC impedance of the detection device 10. Therefore, it is advisable to set a specific range for the voltage of the battery cells of the secondary battery 20 by conducting experiments to satisfy the required detection accuracy of the real part Z of the AC impedance of the detection device 10.

[0073] Furthermore, in one specific example of this embodiment, the detection device 10 determines that the vehicle 300 is in a predetermined state when the vehicle 300 is driven after the secondary battery 20 has been charged by power supplied by a DC current from an external DC power source. In such a case, the usage history of the secondary battery 20 becomes constant, and the influence of the usage history of the secondary battery 20 on the resistance value and electromotive force is suppressed. Therefore, the changes in the resistance value and electromotive force of the battery cells of the secondary battery 20 are reduced. Consequently, the detection accuracy of the real part Z value of the AC impedance of the detection device 10 can be maintained.

[0074] (Second embodiment) Figure 6 is a block diagram showing an example configuration of an ECU according to the second embodiment. As shown in Figure 6, the ECU 100 can be mounted on a vehicle 300. The ECU 100 is a battery ECU that controls a secondary battery 20. The ECU 100 has the same configuration as the detection device 10 shown in Figure 1. Similar to the detection device 10, the ECU 100 detects the impedance of the secondary battery 20 that is the target of detection. Also, similar to the detection device 10, the ECU 100 calculates the amount of Li deposited in the secondary battery 20. Similar to the detection device 10, the ECU 100 detects the real part Z value of the AC impedance from the secondary battery 20 to which a high-frequency signal is supplied when the state of the vehicle 300 is in a predetermined state. Since the state of the vehicle is in a predetermined state, the measurement conditions are constant, and the ECU 100 can suppress a decrease in the detection accuracy of the real part Z value of the AC impedance. Therefore, the risk of a decrease in the measurement accuracy of the amount of Li deposited in the secondary battery 20 can be suppressed.

[0075] 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]

[0076] 10 Detection device 11. High-frequency signal supply unit 12 Impedance detection unit 13 Calculation Section 14 Control Unit 15 Storage section 16 Acquisition Department 17 Judgment section 18 Temperature detection unit 20 Secondary battery 30 Inverters 40 motors 41 wheels 50 charger 51 AC / DC Converter 200 Systems 300 vehicles T1 Thermistor

Claims

1. A vehicle equipped with a lithium-ion secondary battery and a detection device, The detection device is 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 the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle status information indicating the status of the vehicle, The system includes a determination unit that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information, If the determination unit determines that the vehicle is in a predetermined state, the detection unit detects the value of the real part of the AC impedance. vehicle.

2. The aforementioned vehicle status information is vehicle noise information indicating vehicle noise that may affect the impedance measurement accuracy of the lithium-ion secondary battery, The determination unit determines, based on the vehicle noise information, whether the vehicle noise has a minor effect on the impedance measurement accuracy of the lithium-ion secondary battery. The vehicle according to claim 1.

3. The aforementioned vehicle is equipped with a motor that drives the wheels, The determination unit determines that the state of the vehicle is in a predetermined state when the motor is stopped. The vehicle according to claim 1 or 2.

4. The aforementioned vehicle is equipped with an AC / DC converter that converts alternating current from an external AC power source into direct current. The determination unit determines that the vehicle is in a predetermined state if the switching frequency of the AC / DC converter is within a specific range while the lithium-ion secondary battery is supplied with power by the DC current. The vehicle according to claim 1 or 2.

5. The determination unit determines that the vehicle is in a predetermined state if the temperature of the lithium-ion secondary battery is within a specific range. The vehicle according to claim 1 or 2.

6. The determination unit determines that the vehicle is in a predetermined state if the State of Charge (SOC) of the lithium-ion secondary battery is within a specific range. The vehicle according to claim 1 or 2.

7. The determination unit determines that the vehicle is in a predetermined state if the voltage of the battery cells of the lithium-ion secondary battery is within a specific range. The vehicle according to claim 1 or 2.

8. The determination unit determines that the vehicle is in a predetermined state when the vehicle is driven after the lithium-ion secondary battery has been charged by being supplied with power from an external DC power source. The vehicle according to claim 1 or 2.

9. An ECU that can be installed in a vehicle equipped with a lithium-ion secondary battery, The aforementioned ECU is 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 the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle status information indicating the status of the vehicle, The system includes a determination unit that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information, If the determination unit determines that the vehicle is in a predetermined state, the detection unit detects the value of the real part of the AC impedance. ECU.

10. A system that can be mounted on a vehicle, Lithium-ion rechargeable batteries, A detection device is provided, The detection device is 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 the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle status information indicating the status of the vehicle, The system includes a determination unit that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information, If the determination unit determines that the vehicle is in a predetermined state, the detection unit detects the value of the real part of the AC impedance. system.

11. A detection device that can be mounted on a vehicle equipped with a lithium-ion secondary battery, 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 the lithium-ion secondary battery to which the high-frequency signal is supplied, An acquisition unit that acquires vehicle status information indicating the status of the vehicle, The system includes a determination unit that determines whether the state of the vehicle is in a predetermined state based on the vehicle state information, If the determination unit determines that the vehicle is in a predetermined state, the detection unit detects the value of the real part of the AC impedance. Detection device.

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