Vehicle, ECU, system, and detection apparatus

Abstract

A vehicle, an ECU, a system, and a detection apparatus capable of reducing the possibility of the deterioration of the accuracy of the measurement of the Li deposition amount in a lithium-ion secondary battery are provided. A vehicle (300) includes a lithium-ion secondary battery and a detection apparatus (10). The detection apparatus (10) includes: a high-frequency signal supply unit (11) configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; an acquisition unit (16) configured to acquire vehicle state information indicating a state of the vehicle (300); and a determination unit (17) configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information.

Description

VEHICLE, ECU, SYSTEM, AND DETECTION APPARATUS

[0001] The present disclosure relates to a vehicle, an ECU, a system, and a detection apparatus.

[0002] It has been desired to suppress the deposition of metal Li (lithium) (hereinafter referred to as Li deposition) in a lithium-ion secondary battery in order to prevent the performance of the lithium-ion secondary battery from deteriorating. However, no technique for nondestructively detecting Li deposition in a lithium-ion secondary battery has been known.

[0003] For this matter, as disclosed in Patent Literature 1, the inventors of the present application have developed a technique for detecting the real part of the AC (Alternating-Current) impedance of a lithium-ion secondary battery by using a high-frequency signal, and then calculating the amount of Li deposition (hereinafter also referred to as an Li deposition amount) in the lithium-ion secondary battery based on a difference between the current value (i.e., the value at the present time) of the real part of the AC impedance and the initial value thereof.

[0004] PTL 1: Japanese Patent No. 7347451

[0005] In a vehicle, the accuracy of the measurement of an impedance may deteriorate depending on the state of the vehicle. As a result, the accuracy of the measurement of the Li deposition amount in the lithium-ion secondary battery may deteriorate.

[0006] The present disclosure has been made in view of the above-described problem and provides a vehicle, an ECU, a system, and a detection apparatus capable of reducing the possibility of the deterioration of the accuracy of the measurement of the Li deposition amount in a lithium-ion secondary battery.

[0007] A vehicle according to the present disclosure is a vehicle including a lithium-ion secondary battery and a detection apparatus, in which 　　the detection apparatus includes: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit may detect the value of the real part of the AC impedance.

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

[0009] Further, in the above-described vehicle, the vehicle may include a motor configured to drive a wheel, and the determination unit may determine that the state of the vehicle is the predetermined state when the motor is stopped.

[0010] Further, in the above-described vehicle, the vehicle may include an AC / DC converter configured to convert an AC current supplied from an external AC power supply into a DC current, and 　　the determination unit may determine that the state of the vehicle is the predetermined state when a switching frequency of the AC / DC converter is within a specific range while the lithium-ion secondary battery is being supplied with power by the DC current.

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

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

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

[0014] Further, in the above-described vehicle, the determination unit may determine that the state of the vehicle is the predetermined state when the vehicle has traveled after the lithium-ion secondary battery is charged by being supplied with power by the DC current supplied from an external DC power supply.

[0015] An ECU according to the present disclosure is an ECU capable of being mounted in a vehicle including a lithium-ion secondary battery, in which 　　the ECU includes: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

[0016] A system according to the present disclosure is a system capable of being mounted in a vehicle, and including: 　　a lithium-ion secondary battery; and 　　a detection apparatus, in which 　　the detection apparatus includes: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

[0017] A detection apparatus according to the present disclosure is a detection apparatus capable of being mounted in a vehicle including a lithium-ion secondary battery, and including: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

[0018] According to the present disclosure, it is possible to reduce the risk of the deterioration of the accuracy of the measurement of the Li deposition amount in a lithium-ion secondary battery.

[0019] Fig. 1 is a block diagram showing a configuration of a vehicle according to a first embodiment;Fig. 2 shows a relationship between the SOH of a secondary battery and the amount of change in the real part Z of an AC impedance that occurs when a high-frequency signal having a frequency of 1 MHz is supplied to the secondary battery;Fig. 3 shows a relationship between the frequency of an AC signal supplied to the secondary battery and the real part of the AC impedance detected from the secondary battery;Fig. 4 shows a 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;Fig. 5 is a flowchart showing a detection method according to the first embodiment; andFig. 6 is a block diagram showing a configuration of an ECU according to a second embodiment.

[0020] Specific embodiments to which the present invention is applied will be described hereinafter in detail with reference to the drawings. However, the present invention is not limited to the below-shown embodiments. Further, in order to clarify the description, the following description and the drawings are simplified as appropriate.

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

[0022] The vehicle 300 may include an inverter 30, a motor 40, a wheel(s) 41, and a charger 50. The vehicle 300 may include 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 a DC (Direct-Current) current to the inverter 30. The inverter 30 is preferably a three-phase inverter. The inverter 30 converts the DC current into an AC (Alternating-Current) current and supplies the obtained AC current to the motor 40. The motor 40 rotates and drives the wheel(s) 41 by using the supplied AC current. The charger 50 includes an AC / DC converter 51, and preferably also includes a diode or a capacitor as appropriate. The charger 50 is supplied with a single-phase AC current of 100V or 200V from an external AC power supply such as a household power supply. The AC / DC converter 51 converts the supplied AC current into a DC current. The charger 50 supplies the obtained DC current to the secondary battery 20. The secondary battery 20 is charged by receiving power by the AC current from the external AC power supply. Such charging is called normal charging. However, the secondary battery 20 can be charged by receiving power by a DC current from, for example, an external power supply facility such as a charging station. Such charging is called quick charging. The charging speed of quick charging is higher than that of normal charging.

[0023] <Configuration of Secondary Battery 20> 　　Firstly, the secondary battery 20, of which the Li deposition amount or the like is detected, will be described. The secondary battery 20 is a lithium-ion secondary battery, and is formed by a cell stack composed of a plurality of battery cells stacked on one another, and a case for housing the cell stack. Each battery cell includes a positive electrode, a negative electrode, and an ion conduction medium provided between the positive and negative electrodes for conducting carrier ions therebetween. Further, a separator may be provided between the positive and negative electrodes. A resin such as polyethylene or polypropylene is used for the separator.

[0024] For the positive electrode active material, for example, a sulfide containing a transition metal element or an oxide containing lithium and a transition metal element is used. Specifically, as the positive electrode active material, for example, a lithium manganese complex oxide having a basic composition formula Li(1-x)MnO2(where 0<x<1), Li(1-x)Mn2O4, or the like, a lithium cobalt complex oxide having a basic composition formula Li(1-x)CoO2or the like, a lithium nickel complex oxide having a basic composition formula Li(1-x)NiO2or the like, or a lithium nickel cobalt manganese complex oxide having a basic composition formula Li(1-x)NiaCobMncO2(where a+b+c=1) or the like may be used. Note that a material containing another element(s) in addition to the material expressed by one of the above-described basic composition formulas may be used as the positive electrode active material. For example, Al (aluminum) or the like is used as the current collector of the positive electrode.

[0025] For the negative electrode active material, for example, a complex oxide containing lithium or a carbon material may be used. Specifically, as the negative electrode active material, for example, lithium, a lithium alloy, or an inorganic compound such as a tin compound, a carbon material capable of storing and releasing lithium ions, a complex oxide containing a plurality of elements, or a conductive polymer may be used. Examples of carbon materials used for the negative electrode active material include coke, glassy carbon, graphite, hardly graphitizable carbon, pyrolytic carbon, and carbon fiber. Further, graphite such as artificial graphite or natural graphite is preferred. Further, examples of complex oxides used for the negative electrode active material include lithium titanium complex oxide and lithium vanadium complex oxide. For example, Cu (copper) or the like is used as the current collector of the negative electrode.

[0026] The ion-conducting medium is used as an electrolyte by, for example, dissolving a supporting salt in a solvent. For example, a lithium salt such as LiPF6or LiBF4is used as the support salt. For example, one of carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, or a mixture of some of them is used as the solvent of the electrolyte. Examples of carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, and chain carbonates such as dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate. Alternatively, for example, 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 by an organic binder may be used for the ion-conducting medium.

[0027] It should be noted that as the secondary battery 20 is repeatedly recharged, metal Li is deposited on the surface of the electrode of each battery cell. The more the charging power is increased in order to increase the charging speed, the more the Li deposition progresses, and hence the more the State of Health (SOH) of the secondary battery 20 deteriorates.

[0028] Note that the SOH of the secondary battery 20 is a percentage of the current fully-charged capacity (i.e., the fully-charged capacity at the present time) of the secondary battery 20 to the initial fully-charged capacity thereof.

[0029] <Configuration of Detection Apparatus 10> 　　Next, the detection apparatus 10 will be described. As shown in Fig. 1, the detection apparatus 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, an acquisition unit 16, and a determination unit 17. The detection apparatus 10 may also include a temperature detection unit 18. The detection apparatus 10 detects the impedance of the secondary battery 20, of which the Li deposition amount or the like is detected. The detection apparatus 10 calculates the Li deposition amount in the secondary battery 20.

[0030] Note that as hardware, the detection apparatus 10 includes, in addition to the storage unit 15 such as a RAM (Random Access Memory) and / or a ROM (Read Only Memory) in which various programs and data are stored, an arithmetic unit such as a CPU (Central Processing Unit) (not shown). That is, the detection apparatus 10 has a function as a computer, and performs various processes based on the aforementioned various programs and the like.

[0031] Therefore, the functional blocks of the high-frequency signal supply unit 11, the impedance detection unit 12, the calculation unit 13, the control unit 14, the acquisition unit 16, the determination unit 17, and the temperature detection unit 18, which constitute the detection apparatus 10 in Fig. 1, can be formed, as hardware, by a CPU (Central Processing Unit), a memory, and other circuits, and / or can be implemented, as software, by programs and the like loaded in a memory. That is, the above-described functional blocks can be implemented in various forms by computer hardware, software, or combinations thereof. The detection apparatus 10 is preferably mounted on a circuit board, and is preferably incorporated into, for example, an ECU (Electronic Control Unit). Note that the detection apparatus 10 may be a single apparatus that can be attached to and detached from the vehicle 300. The impedance detection unit 12 may include a resonance circuit.

[0032] The high-frequency signal supply unit 11 supplies a high-frequency signal for detecting the Li deposition amount to the secondary battery 20. Specifically, the high-frequency signal supply unit 11 supplies a high-frequency signal having a frequency of 0.1 MHz or higher to the secondary battery 20. This high-frequency signal is preferably such a high-frequency signal that the value of the real part of the AC impedance which is 10 times of or larger than the value of the real part Z of the AC impedance that is detected when an AC signal having a frequency of 1 kHz is supplied to the secondary battery 20 is detected by the skin effect. Specifically, the frequency of this 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, the reaction, and the transfer of lithium ions cannot follow the frequency in each battery cell of the secondary battery 20. Therefore, the current of this high-frequency signal flows along the surface of the electrode of each battery cell on which Li is likely to be deposited due to the skin effect.

[0034] The smaller the Li deposition amount is, the lower the electrical conductivity on the surface of the electrode of each battery cell becomes, and hence the larger the value of the real part Z of the AC impedance becomes. Conversely, the larger the Li deposition amount is, the higher the electrical conductivity on the surface of the electrode of each battery cell becomes, and hence the smaller the value of the real part Z of the AC impedance becomes. Note that since a large amount of current concentrates in the Li metal, which has a high conductivity, the magnetic field changes in and around the area where Li has been deposited, and as a result, an eddy current is formed there. Although this eddy current causes losses in the conductive parts of the current collector foil and the electrode, it reduces the overall loss in the battery. Therefore, the larger the Li deposition amount becomes, the more the change in the magnetic field increases, and as a result, the larger the eddy current becomes, and the smaller the value of the real part Z becomes. Therefore, it is possible to calculate the Li deposition amount in the secondary battery 20 based on the amount of change in the real part Z of the AC impedance detected from the secondary battery 20 supplied with the high-frequency signal (i.e., based on the difference between the detected value of the real part Z and the initial value thereof). Further, the SOH of the secondary battery 20 can also be estimated based on the Li deposition amount.

[0035] Here, Fig. 2 is a graph showing a relationship between the SOH of the secondary battery 20 and the amount of change in the real part Z of the AC impedance (i.e., the difference between the detected value of the real part Z and the initial value thereof) when a high-frequency signal having a frequency of 1 MHz is supplied to the secondary battery 20.

[0036] As indicated by triangular marks in Fig. 2, in the case of normal charging in which the charging power is small, since the Li deposition amount is small even when the charging is repeated, the amount of change in the real part Z of the AC impedance remains at a small value even when the deterioration of the SOH progresses due to other factors. That is, the detected value of the real part Z of the AC impedance is kept at a high value.

[0037] In contrast, as indicated by circular marks in Fig. 2, in the case of quick charging in which the charging power is large, since the Li deposition amount increases when the charging is repeated. As a result, the deterioration of the SOH progresses, and the amount of change in the real part Z of the AC impedance increases. That is, the detected value of the real part Z of the AC impedance is low. Note that in the case where the deterioration of the battery caused by the Li deposition dominates among the deterioration factors of the battery, the Li deposition amount can be derived from the SOH. Alternatively, the SOH can be derived from the Li deposition amount.

[0038] Here, each of Figs. 3 and 4 is a graph showing a 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. Fig. 3 shows the value of the real part Z of the AC impedance when AC signals having frequencies from 1 kHz to 100 kHz are supplied to the secondary battery 20. Fig. 4 shows the value of the real part Z of the AC impedance when AC signals having frequencies from 100 kHz to 100 MHz are supplied to the secondary battery 20.

[0039] As shown in Fig. 3, when an AC signal having a frequency equal to or close to 1 kHz is supplied to the secondary battery 20, the real part Z of the AC impedance has the minimum value. This impedance component indicates an ohmic resistance component. Further, as shown in Figs. 3 and 4, the higher the frequency of the AC signal supplied to the secondary battery 20 becomes, the more the flow of current concentrates in the surface of the electrode of each cell by the skin effect, and hence the more the value of the real part Z of the AC impedance increases.

[0040] Therefore, the high-frequency signal supply unit 11 supplies, to the secondary battery 20, an AC signal having such a high frequency (i.e., such a high-frequency signal) that a value of the real part Z of the AC impedance sufficiently higher than the ohmic resistance component is detected.

[0041] The acquisition unit 16 acquires vehicle state information indicating the state of the vehicle 300. The vehicle state information is, for example, vehicle noise information indicating a vehicle noise that could affect the accuracy of the measurement of the impedance of the secondary battery 20. The vehicle noise information is, for example, information indicating the stop of the motor 40, the high switching frequency of the AC / DC converter 51 or the inverter 30, the temperature of the secondary battery 20, the SOC (State Of Charge) thereof, the voltage of the battery cells, or the history of the use (hereinafter also referred to as a usage history) thereof.

[0042] Note that the acquisition unit 16 may acquire vehicle state information from an ECU mounted in the vehicle 300 through an in-vehicle network. The ECU is, for example, an integrated ECU, a motor ECU, a battery ECU, or a charger ECU. For example, the acquisition unit 16 may acquire the stopped state of the motor 40 and / or the high switching frequency of the inverter 30 from the aforementioned motor PCU. The acquisition unit 16 may acquire the high switching frequency of the AC / DC converter 51 from the aforementioned charger ECU. The acquisition unit 16 may acquire the temperature, the SOC, and the usage history of the secondary battery 20 from the aforementioned battery ECU. The acquisition unit 16 may acquire, for example, the temperature of the secondary battery 20 from the temperature detection unit 18. Further, the acquisition unit 16 may measure the current flowing through the secondary battery 20, and the aforementioned battery ECU may calculate the SOC of the secondary battery 20 based on the measured current. Note that as the method for calculating the SOC, for example, a method using current integration (Coulomb count) or a method using the estimation of an Open Circuit Voltage may be used.

[0043] The determination unit 17 determines whether or not the state of the vehicle 300 is a predetermined state based on the vehicle state information. In the case where the vehicle state information is vehicle noise information, the determination unit 17 determines whether or not the effect of the vehicle noise on the accuracy of the measurement of the impedance of the secondary battery 20 is small based on the vehicle noise information.

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

[0045] More specifically, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the inverter 30 is shut down, when the inverter 30 stops generating the high switching frequency, or when the rotational speed of the motor 40 is equal to or lower than a predetermined value.

[0046] Similarly, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the switching control of the inverter 30 is stopped. Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the shift range of the vehicle 300 is an N range (neutral range). Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the vehicle 300 is being charged by a plug-in method, or is being supplied with electricity. Note that the charging by the plug-in method includes, for example, the normal charging and the quick charging described above. Further, the supply of electricity by the plug-in method includes, for example, the supply of electricity from the vehicle 300 to a household electrical appliance (V2L: Vehicle to Load) and the supply of electricity from the vehicle 300 to a building (V2H: Vehicle to Home). Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when an air conditioning control apparatus of the vehicle 300 is performing pre-air conditioning control. Note that when the air conditioning control apparatus of the vehicle 300 is performing the pre-air conditioning control, the engine of the vehicle 300 may be running or stopped.

[0047] Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the switching frequency of the AC / DC converter 51 is within a specific range while the secondary battery 20 is being supplied with power by the DC current converted by the AC / DC converter 51. This specific range is preferably determined so that no interference occurs between the high switching frequency of the AC / DC converter 51 and the high-frequency signal from the high-frequency signal supply unit 11.

[0048] Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the temperature of the secondary battery 20 is within a specific range. The resistance value of the battery cell (i.e., each battery cell) of the secondary battery 20 changes depending on the temperature of the secondary battery 20. When the resistance value of the battery cells of the secondary battery 20 is high, the accuracy of the measurement of the impedance of the secondary battery 20 tends to improve. Therefore, the specific range of the temperature of the secondary battery 20 is preferably determined based on the relationship between the temperature of the battery cells of the secondary battery 20 and the resistance value thereof so that the accuracy of the measurement of the impedance of the secondary battery 20 is kept within a desired range.

[0049] Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the 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 accuracy of the measurement of the impedance of the secondary battery 20 tends to improve. Therefore, the specific range of the SOC of the secondary battery 20 may be determined based on the relationship between the SOC of the battery cells of the secondary battery 20 and the resistance value thereof so that the accuracy of the measurement of the impedance of the secondary battery 20 is kept within a desired range.

[0050] Further, the determination unit 17 may determine that the state of the vehicle is the predetermined state when the voltage of the battery cells of the secondary battery 20 is within a specific range. The accuracy of the measurement of the impedance of the secondary battery 20 changes depending on the voltage of the battery cells of the secondary battery 20. The relationship between the accuracy of the measurement of the impedance of the secondary battery 20 and the voltage of the battery cells of the secondary battery 20 can be obtained by conducting an experiment. Therefore, the specific range of the voltage of the battery cells of the secondary battery 20 is preferably determined so that the accuracy of the measurement of the impedance of the secondary battery 20 is kept within a desired range.

[0051] Further, the determination unit 17 may determine that the state of the vehicle 300 is the predetermined state when the vehicle 300 has traveled after the secondary battery 20 is charged by being supplied with power by the DC current supplied from an external DC power supply. The resistance value and the electromotive voltage of the battery cells of the secondary battery 20 change according to the usage history of the secondary battery 20, so that the usage history affects the accuracy of the measurement of the impedance of the secondary battery 20. The accuracy of the measurement of the impedance of the secondary battery 20 can be improved by specifying the usage history of the secondary battery 20, in particular, specifying the resistance value and the voltage of the battery cells of the secondary battery 20. Specifically, the usage history of the secondary battery 20 is that the current that has flowed through the secondary battery 20 is within ±B1 amperes within a predetermined period A1 (seconds). Each of A1 and B1 is an arbitrary value equal to or larger than 0 (zero).

[0052] Note that the specific ranges of the switching frequency of the AC / DC converter 51, the temperature of the secondary battery 20, the SOC thereof, and the voltage of the battery cells thereof described above may be theoretically calculated, or may be obtained experimentally or empirically.

[0053] The control unit 14 makes (e.g., instructs) the impedance detection unit 12 start or stop detecting the impedance of the secondary battery 20 according to the results of the determinations made by the determination unit 17. When the vehicle state information is vehicle noise information and the determination unit 17 determines that the effect of the vehicle noise on the accuracy of the measurement of the impedance of the secondary battery 20 is small, the control unit 14 makes the impedance detection unit 12 start detecting the impedance of the secondary battery 20. When the determination unit 17 determines that the effect of the vehicle noise on the accuracy of the measurement of the impedance of the secondary battery 20 is not small, the control unit 14 makes the impedance detection unit 12 stop the detection of the impedance of the secondary battery 20.

[0054] The impedance detection unit 12 detects the value of the real part Z of the AC impedance from the secondary battery 20 supplied with the high-frequency signal. 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 surface of the electrode (Li deposition area) of each battery cell of the secondary battery 20 by the skin effect. Further, even when the Li metal is electrically disconnected from the negative electrode after the Li deposition and hence becomes a floating state, the current flows on the Li metal through the inductive coupling and the electric-field coupling. Therefore, the impedance detection unit 12 can detect the real part Z of the AC impedance corresponding to the Li deposition amount.

[0055] The calculation unit 13 calculates the Li deposition amount in the secondary battery 20 based on the difference between the current value (i.e., the value at the present time) 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 the Li deposition amount in such a manner that the larger the detected value of the real part Z of the AC impedance is, i.e., the smaller the difference from the initial value is, the smaller the calculated Li deposition amount is. Conversely, the calculation unit 13 calculates the Li deposition amount in such a manner that the smaller the detected value of the real part Z of the AC impedance is, i.e., the larger the difference from the initial value is, the larger the calculated Li deposition amount is.

[0056] Note that, for example, the initial value of the real part Z of the AC impedance of the secondary battery 20, of which the Li deposition amount or the like is detected, is stored in the storage unit 15. Further, map information representing, for each type of various secondary batteries, a relationship between the difference (amount of change) between the current value (detected value) of the real part Z of the AC impedance of the secondary battery and the initial value thereof and the Li deposition amount of the secondary battery may be stored in the storage unit 15.

[0057] This map information is, for example, information obtained in advance by an experiment or the like, and may be updated as appropriate by information detected from the secondary battery 20, of which the Li deposition amount or the like is detected. When the map information is used, the calculation unit 13 extracts, from the map information stored in the storage unit 15, the Li deposition amount corresponding to the value of the real part Z of the AC impedance detected by the impedance detection unit 12.

[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 battery cells among a plurality of battery cells constituting the secondary battery 20 by using one or more thermistors T1.

[0059] <Detection Control Method> 　　Next, a detection method according to this embodiment, i.e., operations performed by the detection apparatus 10, will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the detection method according to the first embodiment.

[0060] Firstly, the detection apparatus 10 supplies, to the secondary battery 20, an AC signal (high-frequency signal) having a frequency so high that the diffusion, the reaction, and the transfer of lithium ions cannot follow the frequency in each battery cell (Step S101). For example, the high-frequency signal supply unit 11 supplies, to the secondary battery 20, a high-frequency signal having a frequency of 0.1 MHz or higher.

[0061] Next, the detection apparatus 10 acquires vehicle state information (Step ST102). The vehicle state information is, for example, vehicle noise information. The vehicle noise information is, for example, information indicating the stop of the motor 40, the high switching frequency of the AC / DC converter 51 or the inverter 30, the temperature of the secondary battery 20, the SOC thereof, the voltage of the battery cells, or the usage history thereof.

[0062] Next, the detection apparatus 10 determines whether or not the state of the vehicle 300 is a predetermined state based on the vehicle state information (Step ST103).

[0063] When the detection apparatus 10 determines that the state of the vehicle 300 is not the predetermined state (Step ST103: No), the process returns to the step ST102, and the detection apparatus 10 acquires vehicle state information again.

[0064] When the detection apparatus 10 determines that the state of the vehicle is the predetermined state (Step ST103: Yes), it detects the value of the real part Z of the AC impedance from the secondary battery 20 supplied with the high-frequency signal (Step S104).

[0065] Lastly, the detection apparatus 10 calculates the Li deposition amount in the secondary battery 20 from the detected value of the real part Z of the AC impedance (Step S105). For example, the detection apparatus 10 extracts the Li deposition amount 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 detection apparatus 10 calculates the Li deposition amount in such a manner that the larger the detected value of the real part Z of the AC impedance is, the smaller the calculated Li deposition amount is, and the smaller the detected value of the real part Z of the AC impedance is, the larger the calculated Li deposition amount is.

[0066] As described above, when the state of the vehicle 300 is the predetermined state, the detection apparatus 10 detects the value of the real part Z of the AC impedance from the secondary battery 20 supplied with the high-frequency signal. Since the state of the vehicle is the predetermined state, the measurement conditions become constant, so that the detection apparatus 10 can prevent the accuracy of the detection of the value of the real part Z of the AC impedance from deteriorating. Therefore, it is possible to reduce the risk of the deterioration of the accuracy of the measurement of the Li deposition amount in the secondary battery 20.

[0067] Further, in the case where the vehicle state information is vehicle noise information, the detection apparatus 10 determines whether or not the effect of the vehicle noise on the accuracy of the measurement of the impedance of the secondary battery 20 is small based on the vehicle noise information. When the effect of the vehicle noise on the accuracy of the measurement of the impedance of the secondary battery 20 is small, the detection apparatus 10 detects the value of the real part Z of the AC impedance from the secondary battery 20 supplied with the high-frequency signal. Therefore, the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 can be maintained. Therefore, it is possible to prevent the accuracy of the measurement of the Li deposition amount in the secondary battery 20 from deteriorating.

[0068] Further, in a specific example of this embodiment, the detection apparatus 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 stops and substantially does not generate a high switching frequency. Therefore, the interference between the high switching frequency of the inverter 30 and the high-frequency signal supplied by the high-frequency signal supply unit 11 can be suppressed. Therefore, the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 can be maintained.

[0069] Further, in a specific example of this embodiment, the detection apparatus 10 determines that the state of the vehicle 300 is the predetermined state when the switching frequency of the AC / DC converter 51 is within a specific range while the secondary battery 20 is being supplied with power by the DC current converted by the AC / DC converter 51. In such a case, it is possible to prevent the high switching frequency of the AC / DC converter 51 from interfering with the high-frequency signal supplied by the high-frequency signal supply unit 11. Therefore, the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 can be maintained.

[0070] Further, in a specific example of this embodiment, the detection apparatus 10 determines that the state of the vehicle 300 is the 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 is, the more the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 is improved. Therefore, it is possible to obtain the relationship between the temperature of the secondary battery 20 and the resistance value of the battery cells of the secondary battery 20, and then to calculate the effect of the temperature of the secondary battery 20 on the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 based on the obtained relationship. The specific range of the temperature of the secondary battery 20 is preferably set so that the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 meets the required accuracy.

[0071] Further, in a specific example of this embodiment, the detection apparatus 10 determines that the state of the vehicle 300 is the predetermined state when the SOC of the secondary battery 20 is within a specific range. The higher the resistance value of the secondary battery 20, the more the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 is improved. Therefore, it is possible to obtain the relationship between the SOC of the secondary battery 20 and the resistance value of the battery cells of the secondary battery 20, and then to calculate the effect of the SOC of the secondary battery 20 on the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 based on the obtained relationship. The specific range of the SOC of the secondary battery 20 is preferably set so that the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 meets the required accuracy.

[0072] Further, in a specific example of this embodiment, the detection apparatus 10 determines that the state of the vehicle 300 is the predetermined state when 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 and the frequency of the voltage waveform of the resonance circuit of the impedance detection unit 12 and the resistance value and the like of the battery cells, and affects the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10. Therefore, the specific range of the voltage of the battery cells of the secondary battery 20 is preferably set by performing an experiment so that the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 meets the required accuracy.

[0073] Further, in a specific example of this embodiment, the detection apparatus 10 determines that the state of the vehicle 300 is the predetermined state when the vehicle 300 has traveled after the secondary battery 20 is charged by being supplied with power by the DC current supplied from an external DC power supply. In such a case, the usage history of the secondary battery 20 becomes constant, so that the effect of the usage history of the secondary battery 20 on the resistance value and the electromotive voltage is suppressed. Therefore, the changes in the resistance value and the electromotive voltage of the battery cells of the secondary battery 20 are reduced. Therefore, the accuracy of the detection of the value of the real part Z of the AC impedance by the detection apparatus 10 can be maintained.

[0074] (Second Embodiment) 　　Fig. 6 is a block diagram showing an example of a configuration of an ECU according to a second embodiment. As shown in Fig. 6, an ECU 100 can be mounted in a vehicle 300. The ECU 100 is a battery ECU for controlling a secondary battery 20. The ECU 100 has the same configuration as that of the detection apparatus 10 shown in Fig. 1. Similarly to the detection apparatus 10, the ECU 100 detects the impedance of the secondary battery 20, of which the Li deposition amount or the like is detected. Further, similarly to the detection apparatus 10, the ECU 100 calculates the Li deposition amount in the secondary battery 20. Similarly to the detection apparatus 10, when the state of the vehicle 300 is a predetermined state, the ECU 100 detects the value of the real part Z of the AC impedance from the secondary battery 20 supplied with the high-frequency signal. Since the state of the vehicle is the predetermined state, the measurement conditions become constant, so that the ECU 100 can prevent the accuracy of the detection of the value of the real part Z of the AC impedance from deteriorating. Therefore, it is possible to reduce the risk of the deterioration of the accuracy of the measurement of the Li deposition amount in the secondary battery 20.

[0075] Note that the present invention is not limited to the above-described embodiments, and they can be modified as appropriate without departing from the scope and spirit of the invention. Further, the present invention may be implemented by combining two of more of the above-described embodiments and examples thereof as appropriate.

[0076] This application is based upon and claims the benefit of priority from Japanese patent application No. 2025-017560, filed on February 5, 2025, the disclosure of which is incorporated herein in its entirety by reference.

[0077] 10　　DETECTION APPARATUS 11　　HIGH-FREQUENCY SIGNAL SUPPLY UNIT 12　　IMPEDANCE DETECTION UNIT 13　　CALCULATION UNIT 14　　CONTROL UNIT 15　　STORAGE UNIT 16　　ACQUISITION UNIT 17　　DETERMINATION UNIT 18　　TEMPERATURE DETECTION APPARATUS 20　　SECONDARY BATTERY 30　　INVERTER 40　　MOTOR 41　　WHEEL 50　　CHARGER 51　　AC / DC CONVERTER 200　　SYSTEM 300　　VEHICLE T1　　THERMISTOR

Claims

1. A vehicle comprising a lithium-ion secondary battery and a detection apparatus, wherein 　　the detection apparatus comprises: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

2. The vehicle according to claim 1, wherein 　　the vehicle state information is vehicle noise information indicating a vehicle noise that could affect accuracy of measurement of the impedance of the lithium-ion secondary battery, and 　　the determination unit determines whether or not the effect of the vehicle noise on the accuracy of the measurement of the impedance of the lithium-ion secondary battery is small based on the vehicle noise information.

3. The vehicle according to claim 1 or 2, wherein 　　the vehicle comprises a motor configured to drive a wheel, and 　　the determination unit determines that the state of the vehicle is the predetermined state when the motor is stopped.

4. The vehicle according to claim 1 or 2, wherein 　　the vehicle comprises an AC / DC converter configured to convert an AC current supplied from an external AC power supply into a DC current, and 　　the determination unit determines that the state of the vehicle is the predetermined state when a switching frequency of the AC / DC converter is within a specific range while the lithium-ion secondary battery is being supplied with power by the DC current.

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

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

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

8. The vehicle according to claim 1 or 2, wherein the determination unit determines that the state of the vehicle is the predetermined state when the vehicle has traveled after the lithium-ion secondary battery is charged by being supplied with power by the DC current supplied from an external DC power supply.

9. An ECU capable of being mounted in a vehicle comprising a lithium-ion secondary battery, wherein 　　the ECU comprises: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

10. A system capable of being mounted in a vehicle, and comprising: 　　a lithium-ion secondary battery; and 　　a detection apparatus, wherein 　　the detection apparatus includes: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

11. A detection apparatus capable of being mounted in a vehicle comprising a lithium-ion secondary battery, and comprising: 　　a high-frequency signal supply unit configured to supply a high-frequency signal having a frequency of 0.1 MHz or higher to the lithium-ion secondary battery; 　　a detection unit configured to detect a value of a real part of an AC impedance from the lithium-ion secondary battery supplied with the high-frequency signal; 　　an acquisition unit configured to acquire vehicle state information indicating a state of the vehicle; and 　　a determination unit configured to determine whether or not the state of the vehicle is a predetermined state based on the vehicle state information, and 　　when the determination unit determines that the state of the vehicle is the predetermined state, the detection unit detects the value of the real part of the AC impedance.

Images