Battery unit, battery monitoring device and program

Abstract

A storage battery 10 comprises: a positive electrode layer; a negative electrode layer; and a separator that is disposed between the positive electrode layer and the negative electrode layer. The separator is provided in a form containing a substance that has a dielectric constant which changes according to the temperature. A battery unit 30 comprises: a calculation unit 31 that applies AC signals to a positive electrode terminal 14 and a negative electrode terminal 15 of the storage battery 10, and calculates a dielectric constant or a capacitor capacity on the basis of the response signals; and a temperature monitoring unit 32 that monitors the internal temperature of the storage battery 10 on the basis of the dielectric constant or the capacitor capacity which has been calculated by the calculation unit 31.

Description

Storage battery, battery unit, and battery monitoring device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2022-139443 filed on September 1, 2022, the contents of which are incorporated herein by reference.

[0002] The disclosure in this specification relates to a storage battery, a battery unit, and a battery monitoring device.

[0003] Various techniques for monitoring the internal temperature of secondary batteries, such as lithium-ion batteries, have been proposed. For example, one known technique includes an external surface temperature detector that detects the external surface temperature of the battery, a current detector that detects the charge / discharge current of the battery, and an internal resistance estimator that estimates the internal resistance of the battery, and estimates the internal temperature of the battery based on the external surface temperature, charge / discharge current, and internal resistance of the battery (see, for example, Patent Document 1). Another known technique involves providing temperature sensors only in specific positions (e.g., both end positions and the center position) of all battery cells in a battery pack having multiple battery cells, and estimating the temperatures of battery cells without temperature sensors by linearly interpolating the temperature detection values ​​of the temperature sensors.

[0004] Japanese Patent Application Laid-Open No. 2018-170144

[0005] However, existing technologies do not directly detect the internal temperature of a storage battery, but estimate the internal temperature using the detected value of the battery's outer surface temperature, etc., which results in a detection delay due to the time required for heat to transfer from the inside of the storage battery to the outer surface. Therefore, for example, when a temperature change occurs inside the storage battery, there is a concern that there will be a delay before the temperature change can be detected. For example, in storage batteries, thermal runaway can occur due to some factor, and when thermal runaway occurs, prompt and appropriate action is desired.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a storage battery, a battery unit, and a battery monitoring device that enable early detection of internal temperature.

[0007] The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. The objectives, features, and advantages disclosed in this specification will become more apparent by referring to the following detailed description and the accompanying drawings.

[0008] Means 1 is a storage battery comprising a positive electrode layer, a negative electrode layer, and a separator provided between the positive electrode layer and the negative electrode layer, wherein the separator is provided in a form containing a material whose dielectric constant changes depending on temperature.

[0009] In the storage battery, the separator is provided in a form containing a material whose dielectric constant changes with temperature, so that the internal temperature of the storage battery can be detected by measuring the dielectric constant or its correlation value. In this case, for example, when a temperature change occurs inside the storage battery, the temperature change can be directly detected as a change in the dielectric constant inside the battery. As a result, a storage battery that allows for early detection of the internal temperature can be realized.

[0010] In the second means, a ferroelectric material is used as the substance. In this case, by adding the ferroelectric material to the separator, the dielectric constant can be increased, and the temperature detection sensitivity can be improved.

[0011] In the third aspect, the separator melts when the temperature inside the battery reaches a predetermined melting temperature, and a ferroelectric material is used as the material, the Curie temperature of which, at or near the melting temperature of the separator, is the dielectric constant of which is at its maximum.

[0012] In a storage battery, when the internal temperature rises and thermal runaway occurs, the following process occurs in this order: separator melting, positive electrode thermal decomposition, internal gas generation, and thermal runaway. In this case, when the internal temperature of the storage battery rises and reaches or near the separator melting temperature, a sudden change in the battery's dielectric constant (sudden change in capacitor capacitance) occurs. Here, by understanding the sudden change in dielectric constant, it is possible to quickly identify situations in which the battery may experience thermal runaway.

[0013] Means 4 includes the storage battery according to any one of means 1 to 3, a calculation unit that applies an AC signal to the positive electrode layer and the negative electrode layer and calculates a dielectric constant or a capacitor capacitance based on a response signal, and a temperature monitoring unit that monitors an internal temperature of the storage battery based on the dielectric constant or the capacitor capacitance calculated by the calculation unit.

[0014] In a storage battery configured to change its dielectric constant with temperature, the capacitance between the positive and negative electrode layers changes with temperature. On the other hand, electrochemical impedance measurement (AC impedance method) can be used to apply an AC signal to the positive and negative electrode layers to obtain the impedance frequency characteristics, and calculate the capacitance of the storage battery based on the impedance frequency characteristics. In this case, the AC signal is applied to the positive and negative electrode layers to calculate the dielectric constant or capacitance, and the calculated dielectric constant or capacitance can be used to monitor the battery, thereby enabling the internal temperature of the storage battery to be appropriately determined.

[0015] In means 5, in the storage battery, the separator melts when the temperature inside the battery reaches a predetermined melting temperature, and a ferroelectric material is used as the material, whose Curie temperature at which the dielectric constant is maximized is the melting temperature of the separator or a temperature close to that temperature, and the temperature monitoring unit determines, based on the dielectric constant or capacitor capacity calculated by the calculation unit, that the internal temperature of the storage battery has risen to a predetermined temperature set as the melting temperature of the separator or a temperature close to that temperature.

[0016] In the above configuration, it is possible to determine whether the internal temperature of the battery has risen to the separator melting temperature or a temperature close to that temperature based on the dielectric constant or capacitance of the battery, thereby enabling early detection of the risk of thermal runaway in the battery and allowing appropriate measures to be taken, such as notifying the user.

[0017] In means 6, in the storage battery, the material includes a plurality of materials having different Curie temperatures at which the dielectric constant reaches a maximum value, and a unique correlation between temperature and dielectric constant or capacitor capacity is determined within a predetermined temperature range including the Curie temperatures of each of the materials, and the temperature monitoring unit uses the correlation to estimate the internal temperature of the storage battery based on the dielectric constant or capacitor capacity calculated by the calculation unit.

[0018] In a storage battery in which multiple substances with different Curie temperatures are added to the separator, it is possible to determine a unique correlation between temperature and the dielectric constant or capacitance within a predetermined temperature range that includes the Curie temperatures of the substances. In other words, it is possible to quantify the change in the dielectric constant or capacitance corresponding to the internal temperature of the storage battery. Then, by using this correlation, it is possible to estimate the internal temperature of the storage battery based on the dielectric constant or capacitance.

[0019] Means 7 includes a temperature determination unit that determines whether the internal temperature of the storage battery and the external temperature outside the storage battery are the same, and a correction value calculation unit that, when it is determined that the temperature of the storage battery and the external temperature are the same, calculates a correction value to correct the correlation by comparing the external temperature under that condition with the internal temperature of the storage battery estimated by the temperature monitoring unit.

[0020] For example, if a storage battery is left unused for a long period of time, the internal temperature of the storage battery will be the same as the external temperature. In this case, by comparing the internal temperature (estimated temperature) of the storage battery with the external temperature, it is possible to grasp the deviation in the correlation between temperature and the dielectric constant or capacitor capacitance. In this regard, with the above-described configuration, a correction value for correcting the correlation is calculated, and the correlation is appropriately corrected using the correction value, thereby improving the accuracy of temperature estimation in the storage battery.

[0021] Means 8 is a battery monitoring device applicable to a storage battery comprising a positive electrode layer, a negative electrode layer, and a separator provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form containing a substance whose dielectric constant changes depending on temperature, the battery monitoring device comprising: a calculation unit that applies an AC signal to the positive electrode layer and the negative electrode layer and calculates the dielectric constant or capacitor capacitance based on the response signal; and a temperature monitoring unit that monitors the internal temperature of the storage battery based on the dielectric constant or capacitor capacitance calculated by the calculation unit.

[0022] In a storage battery configured to change its dielectric constant with temperature, the capacitance between the positive and negative electrode layers changes with temperature. On the other hand, electrochemical impedance measurement (AC impedance method) can apply an AC signal to the positive and negative electrode layers to obtain the impedance frequency characteristics, and calculate the capacitance of the storage battery based on the impedance frequency characteristics. In this case, applying an AC signal to the positive and negative electrode layers to calculate the dielectric constant or capacitance can be used to monitor the battery, thereby enabling the internal temperature of the storage battery to be appropriately determined. Furthermore, the internal temperature can be detected quickly.

[0023] Means 9 is a battery monitoring device that is applicable to the storage battery according to any one of Means 1 to 3, and includes an AC signal application unit that applies, to the positive electrode layer and the negative electrode layer of the storage battery, AC signals having a frequency higher than an AC frequency corresponding to a zero crossing point at which an imaginary part becomes zero in a complex impedance characteristic of the storage battery; a calculation unit that calculates the dielectric constant of the separator based on a response signal in a state in which the AC signal is applied by the AC signal application unit; and a temperature monitoring unit that monitors an internal temperature of the storage battery based on the dielectric constant calculated by the calculation unit.

[0024] In a storage battery with a ferroelectric material added to the separator, the dielectric constant of the ferroelectric material changes with changes in the battery's temperature. It has also been discovered that applying an AC signal with a frequency higher than the AC frequency corresponding to the zero-crossing point (the real component where the imaginary part becomes zero) in the complex impedance characteristic to the battery results in a value corresponding to the dielectric constant of the ferroelectric material as the real part of the complex impedance. In this case, by calculating the dielectric constant of the ferroelectric material from the real part of the complex impedance, it is possible to estimate the temperature of the battery from the dielectric constant.

[0025] In consideration of this, an AC signal having a frequency higher than the AC frequency corresponding to the zero-cross point in the complex impedance characteristics of the battery is applied to the positive electrode layer and the negative electrode layer of the storage battery, and the dielectric constant of the separator is calculated based on the response signal obtained under this condition.The internal temperature of the storage battery is then monitored based on the calculated dielectric constant.This makes it possible to appropriately grasp the internal temperature of the storage battery.

[0026] In the means 10, the AC signal applying section applies an AC signal in a frequency range of 20 to 800 kHz as the AC signal.

[0027] In a storage battery, the AC frequency corresponding to the zero crossing point in the complex impedance characteristic is, for example, about 1 to 10 kHz, so the frequency of the AC signal used to calculate the dielectric constant of the separator is set to 20 to 800 kHz. In this case, it is possible to properly grasp the state in which the dielectric constant of the separator changes with temperature.

[0028] In means 11, the AC signal application unit applies an AC signal of a first frequency for measuring the complex impedance characteristics near the zero crossing point, and an AC signal of a second frequency higher than the first frequency, and the calculation unit calculates the internal resistance of the storage battery based on the response signal when the AC signal of the first frequency is applied, and calculates the dielectric constant of the separator based on the response signal when the AC signal of the second frequency is applied.

[0029] The AC signal applying unit applies an AC signal of a first frequency for measuring complex impedance characteristics near a zero-crossing point and an AC signal of a second frequency higher than the first frequency. The internal resistance of the storage battery is calculated based on a response signal when the AC signal of the first frequency is applied, while the dielectric constant of the separator is calculated based on a response signal when the AC signal of the second frequency is applied. In this case, the calculation of the internal resistance and the dielectric constant can be performed appropriately by selectively using an AC frequency suitable for calculating the internal resistance of the storage battery and an AC frequency suitable for calculating the dielectric constant of the separator.

[0030] In means 12, in the storage battery, the separator melts when the temperature inside the battery reaches a predetermined melting temperature, and the calculation unit increases the frequency of calculating the dielectric constant when the temperature of the storage battery is higher than a predetermined temperature that is lower than the melting temperature, compared to when the temperature is lower than the predetermined temperature.

[0031] In a configuration in which a material (ferroelectric) whose dielectric constant changes with temperature is added to the separator, the temperature characteristics of the dielectric constant can be used to determine whether the internal temperature of the storage battery has reached or approached the separator's melting temperature. On the other hand, calculating the dielectric constant from the complex impedance calculation results raises concerns about increased computational load and power consumption. In consideration of this, the frequency of calculating the dielectric constant is increased when the temperature of the storage battery is higher than a predetermined temperature lower than the melting temperature compared to when the temperature is lower than the predetermined temperature. This allows the frequency of calculating the dielectric constant to be relatively low during the storage battery's normal state, thereby reducing computational load and power consumption, while temporarily increasing the sensitivity of detecting temperature increases when there is a risk of thermal runaway.

[0032] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 10 is a diagram showing the relationship between frequency f and real part Re_Z; FIG. 11 is a diagram showing an equivalent circuit of the storage battery; FIG. 12 is a diagram showing the configuration of a control device in a third embodiment; FIG. 13 is a flowchart showing the temperature monitoring process of the storage battery in the third embodiment; FIG. 14 is a diagram showing the relationship between real part Re_Z and relative dielectric constant εr; and FIG. 15 is a flowchart showing the temperature monitoring process of the storage battery in a modified example.

[0033] Hereinafter, embodiments will be described with reference to the drawings. In this embodiment, a lithium ion battery is used as the secondary battery, and a specific configuration using the lithium ion battery will be described. In each of the following embodiments, identical or equivalent parts are denoted by the same reference numerals in the drawings, and the same description of the parts with the same reference numerals is used.

[0034] First Embodiment Fig. 1 is a perspective view of a lithium ion battery 10 according to this embodiment, and Fig. 2 is a perspective view of a wound body 21 that constitutes the lithium ion battery 10. In the following description, the lithium ion battery 10 will be simply referred to as the battery 10.

[0035] In FIG. 1 , a storage battery 10 includes a housing 11 and a wound body 21 housed in the housing 11. The housing 11 has a flattened rectangular parallelepiped shape and is made of, for example, a metal material or a resin material. The housing 11 includes a main body 12 and a cover 13 that can be attached to the opening side of the main body 12, and the main body 12 and cover 13 form a closed space that houses the wound body 21. The wound body 21 is housed in the housing 11 in a state impregnated with an electrolyte. The housing 11 includes a positive terminal 14 and a negative terminal 15 for external connection, and a safety valve 16 that opens to release the internal pressure of the housing 11 when the internal pressure of the housing 11 rises to a predetermined level.

[0036] As shown in Fig. 2, the wound body 21 is configured by laminating a positive electrode layer 22, a negative electrode layer 23, and a separator 24. Specifically, the positive electrode layer 22, the negative electrode layer 23, and the separator 24 are each formed in a sheet shape, and these are laminated together to form a laminate sheet. The laminate sheet made of the positive electrode layer 22, the negative electrode layer 23, and the separator 24 is then wound into a flat shape to form the wound body 21. In the laminate sheet, the positive electrode layer 22, the separator 24, the negative electrode layer 23, and the separator 24 are stacked in this order to form four layers, and by winding this laminate sheet, the separator 24 is interposed between the positive electrode layer 22 and the negative electrode layer 23.

[0037] The positive electrode layer 22 is formed of a positive electrode active material layer made of, for example, a lithium transition metal oxide. Examples of the positive electrode active material that can be used include Li(CoNiMn)O, LiNiO, LiMnO, LiCoO, and LiFePO. The negative electrode layer 23 is formed of, for example, a carbon-based material.

[0038] The separator 24 is an insulating sheet having ion conductivity. Specifically, the separator is formed of a polyolefin layer such as polypropylene (PP), polyethylene (PE), or a combination of these compounds.

[0039] The wound body 21 is provided with a positive electrode current collector 26 made of aluminum foil or the like, and a negative electrode current collector 27 made of copper foil or the like. When the wound body 21 is housed in the housing 11, the positive electrode current collector 26 is electrically connected to the positive electrode terminal 14, and the negative electrode current collector 27 is electrically connected to the negative electrode terminal 15.

[0040] However, there is a concern that the internal temperature of the storage battery 10 may rise excessively, resulting in thermal runaway. In this case, as the internal temperature rises, melting of the separator 24, thermal decomposition of the positive electrode layer 22, generation of internal gas, and thermal runaway occur in this order. If there is a risk of thermal runaway, it is desirable to quickly detect the rise in internal temperature of the storage battery 10. Therefore, in this embodiment, a ferroelectric substance is added to the separator 24 of the storage battery 10 as a substance whose dielectric constant changes with temperature. By measuring the dielectric constant, the internal temperature of the storage battery 10 can be detected. In this embodiment, barium titanate (BaTiO3) is used as the ferroelectric substance.

[0041] FIG. 3 is a diagram showing the temperature characteristic of the dielectric constant of a ferroelectric. As shown in FIG. 3, a ferroelectric has the characteristic that the dielectric constant reaches a maximum value at a plurality of specific temperatures (Curie temperatures). In this embodiment, the separator 24 is provided with a predetermined temperature characteristic by incorporating a ferroelectric material. A ferroelectric material is attached to one or both of the front and back surfaces of the sheet-like separator 24. Specifically, it is conceivable to attach particulate ferroelectric material to the sheet surface of the separator 24 by coating. It is also possible to embed (contain) a ferroelectric material inside the separator 24.

[0042] Here, the separator 24 melts when the temperature inside the battery reaches a predetermined melting temperature (around 120 to 140°C). In contrast, the ferroelectric material added to the separator 24 has one of its Curie temperatures, at which the dielectric constant reaches a maximum, at or near the melting temperature of the separator 24. In FIG. 3 , of the multiple maximum values, "A" is the maximum value corresponding to the melting temperature of the separator 24. In this case, when thermal runaway occurs in the storage battery 10, a sudden change in the dielectric constant of the storage battery 10 (a sudden change in the capacitor capacitance) occurs when the internal temperature of the storage battery 10 rises and reaches or near the melting temperature of the separator 24.

[0043] FIG. 4 is a diagram showing a schematic configuration of a battery unit 30 including a storage battery 10. In FIG. 4, the battery unit 30 includes a calculation unit 31 connected to the positive and negative terminals 14 and 15 of the storage battery 10 and calculating the capacitor capacity of the storage battery 10 based on electrical information input from these terminals 14 and 15, a temperature monitoring unit 32 monitoring the internal temperature of the storage battery 10 based on the capacitor capacity calculated by the calculation unit 31, and a notification unit 33 providing a notification to a user or the like based on the monitoring results of the temperature monitoring unit 32. These units are processing functions realized by a control device 40 including a microcomputer or the like. In the control device 40, the microcomputer includes a CPU (arithmetic unit) and a storage device (various memories) and realizes various functions by executing programs stored in the storage device. The various functions may be realized by electronic circuits, which are hardware, or by both hardware and software. The control device 40 corresponds to a "battery monitoring device."

[0044] When monitoring the temperature of the storage battery 10, the calculation unit 31 applies an AC signal to the positive electrode terminal 14 and the negative electrode terminal 15 and calculates the capacitor capacitance based on the response signal. In this embodiment, an electrochemical impedance measurement method (AC impedance method) is used, in which an AC voltage is applied to the positive electrode terminal 14 and the negative electrode terminal 15, and the capacitance of the storage battery 10 is calculated based on the frequency characteristics of the complex impedance obtained from the AC voltage and the AC current, which is the response signal. Note that an AC current can also be applied as the AC signal. The dielectric constant can also be calculated by using the correlation between the capacitor capacitance and the dielectric constant.

[0045] Furthermore, the temperature monitoring unit 32 determines, based on the capacitor capacity, whether the internal temperature of the storage battery 10 has risen to a predetermined temperature (e.g., 120°C) corresponding to the melting temperature of the separator 24. The notification unit 33 notifies, based on the monitoring result by the temperature monitoring unit 32, by voice, screen display, lamp display, or the like, that there is a risk of thermal runaway occurring in the storage battery 10.

[0046] FIG. 5 is a flowchart showing the temperature monitoring process for the storage battery 10, which is executed by the control device 40 at predetermined intervals.

[0047] 5, in step S11, the capacitance of the capacitor of the storage battery 10 is calculated. At this time, as described above, the AC impedance method is used to apply AC signals to the positive terminal 14 and the negative terminal 15, and the capacitance of the capacitor is calculated based on the response signal.

[0048] Then, in step S12, it is determined whether the internal temperature of the storage battery 10 has risen to a predetermined temperature (e.g., 120°C) corresponding to the melting temperature of the separator 24, depending on whether the capacitor capacity calculated in step S11 is greater than a predetermined value. At this time, if the capacitor capacity of the storage battery 10 is a capacitor capacity corresponding to the dielectric constant that is the maximum value in the temperature characteristic of the dielectric constant, it is determined that the internal temperature of the storage battery 10 has risen to a temperature corresponding to the melting temperature of the separator 24, and the result of step S12 is affirmative, and the process proceeds to step S13. In step S13, a user or the like is notified that there is a risk of thermal runaway in the storage battery 10.

[0049] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0050] In the storage battery 10, the separator 24 is provided in a form containing a material (ferroelectric) whose dielectric constant changes with temperature. Therefore, the internal temperature of the storage battery 10 can be detected by measuring the dielectric constant or the capacitance of the capacitor, which is its correlated value. In this case, when a temperature change occurs inside the storage battery 10, the temperature change can be directly detected as a change in the dielectric constant inside the battery. As a result, a storage battery 10 can be realized that allows for early detection of the internal temperature.

[0051] The storage battery 10 of this embodiment does not require a change in the electrode material of the existing configuration of the storage battery 10, and can remain unchanged. The electrode material affects the energy capacity, power density, and degradation of these performance characteristics over time of the storage battery, and requires extensive development work to tune it. Therefore, adding a new substance to the electrode material requires another extensive development work to maintain the same performance. In contrast, the above-mentioned disadvantages can be avoided by adding a ferroelectric to the separator 24 as described above.

[0052] By adding a ferroelectric material to the separator 24, the dielectric constant can be increased, and the temperature detection sensitivity can be improved.

[0053] The separator 24 is configured to include a ferroelectric material whose Curie temperature, at which the dielectric constant reaches a maximum value, is at or near the melting temperature of the separator 24. In this case, by detecting a sudden change in the dielectric constant, it is possible to quickly detect a situation in which thermal runaway of the storage battery 10 may occur.

[0054] By applying an AC signal to the positive electrode layer 22 and the negative electrode layer 23 to calculate the capacitor capacitance (or dielectric constant), and using the calculated capacitor capacitance for battery monitoring, it is possible to appropriately determine the internal temperature of the storage battery 10. Furthermore, based on the calculated capacitor capacitance, it is determined whether the internal temperature of the storage battery 10 has risen to a predetermined temperature set as the melting temperature of the separator 24 or a temperature close to that temperature. This allows early detection of the risk of thermal runaway in the storage battery 10, allowing appropriate measures to be taken, such as notifying the user.

[0055] In comparison with existing technologies, in those technologies, information regarding the heat inside the battery had to be obtained from a temperature sensor outside the battery or a sensor that detects the pressure and composition of gas released outside the battery during thermal runaway. In contrast, in this embodiment, information regarding the heat inside the battery can be suitably obtained from the capacitor capacity of the storage battery 10 without an external temperature sensor or gas sensor.

[0056] Second Embodiment In the second embodiment, as described above, a ferroelectric material is added to the separator 24 of the storage battery 10. In particular, in this embodiment, a change in the dielectric constant or a change in the capacitance of the capacitor corresponding to the internal temperature of the storage battery 10 is quantified, and the internal temperature of the storage battery 10 is estimated based on the dielectric constant information or capacitance information obtained from the storage battery 10.

[0057] Here, the ferroelectric material added to the separator 24 contains multiple materials with different Curie temperatures at which the dielectric constant reaches a maximum. As a result, as shown in FIG. 6A, in the storage battery 10, the dielectric constant reaches a maximum at temperatures T1 to T3, which differ for each material. In this case, the temperatures T1 to T3 at which the maximum values ​​occur should preferably be equally spaced. However, the temperature intervals on the low-temperature side may be narrower than those on the high-temperature side. Alternatively, the temperature intervals on the low-temperature side may be wider than those on the high-temperature side. The maximum values ​​of the dielectric constant may occur at two or four or more temperatures.

[0058] As shown in Fig. 6(b), the magnitude of the maximum value is made different for each material, and the temperature characteristics are smoothed (flattened), and then the temperature characteristics of the composite dielectric constant are combined to obtain the temperature characteristics of the composite dielectric constant. This adjustment results in the relationship shown in Fig. 6(c).

[0059] 6(c), a unique correlation between temperature and dielectric constant is established within a predetermined temperature range RT that includes the temperatures T1 to T3. The temperature range RT may be a range that includes the operating temperature range in which the storage battery 10 operates. The temperature range RT may also be a range that includes the operating temperature range in which the storage battery 10 operates and the melting temperature of the separator 24. Because the dielectric constant and the capacitor capacitance are proportional to each other, a unique correlation between temperature and capacitor capacitance may be established.

[0060] By mixing additives such as shifters or depressors into the ferroelectric, it is possible to shift the maximum value of the dielectric constant to the lower temperature side or flatten the maximum value. As a shifter, for example, it is possible to use one in which Ba2+ in barium titanate is replaced with Sr2+, Ca2+, etc., or Ti4+ is replaced with Sn4+, Zr4+, etc. As a depressor, it is possible to use CaTiO3, MgTiO3, etc.

[0061] In the battery unit 30 of this embodiment, in Fig. 4, the calculation unit 31 calculates the dielectric constant of the storage battery 10. The temperature monitoring unit 32 uses the relationship shown in Fig. 6(c) to estimate the internal temperature of the storage battery 10 based on the dielectric constant calculated by the calculation unit 31. In addition, in this embodiment, the control device 40 calculates a correction value for correcting the relationship shown in Fig. 6(c) under conditions where the internal temperature and external temperature of the storage battery 10 are the same. Although not shown, the control device 40 further includes a temperature determination unit and a correction value calculation unit in addition to the configuration shown in Fig. 4.

[0062] FIG. 7 is a flowchart showing the correction value calculation process in the temperature monitoring process of this embodiment, and this process is executed by the control device 40 at a predetermined interval.

[0063] 7 , in step S21, it is determined whether the internal temperature of the storage battery 10 and the external temperature outside the storage battery 10 are the same (temperature determination unit). The external temperature may be a temperature detected by, for example, a temperature sensor attached to the outside of the storage battery 10 (external surface of the housing) or a temperature sensor provided in the environment in which the storage battery 10 is installed. For example, when the storage battery 10 is left unused for a long period of time, the internal temperature of the storage battery 10 and the external temperature become the same, and step S21 is determined as positive. If step S21 is determined as positive, the process proceeds to step S22.

[0064] In step S22, as described above, the AC impedance method is used to calculate the dielectric constant of the storage battery 10. In the following step S23, the internal temperature of the storage battery 10 is estimated based on the dielectric constant calculated in step S22 using the relationship shown in Fig. 6(c).

[0065] Then, in step S24, the current external temperature is compared with the estimated internal temperature of the storage battery 10 to determine whether the two temperatures match, specifically, whether the difference between the two temperatures is within a predetermined range. If the current external temperature and the estimated internal temperature of the storage battery 10 do not match, the process proceeds to step S25, where a correction value for correcting the relationship shown in FIG. 6(c) is calculated. This correction value is calculated, for example, as an offset correction value, and the estimated internal temperature estimated using the relationship shown in FIG. 6(c) is corrected using the correction value at the next and subsequent temperature estimations. The correction value may be stored and held in a backup memory such as an EEPROM. Alternatively, the relationship shown in FIG. 6(c) may be updated using the correction value.

[0066] According to the present embodiment described above in detail, in the storage battery 10, by adding a plurality of substances with different Curie temperatures to the separator 24, it is possible to determine a unique correlation between temperature and dielectric constant (or capacitor capacitance) within a predetermined temperature range including between the respective Curie temperatures. Then, by using this correlation, it is possible to estimate the internal temperature of the storage battery 10 based on the dielectric constant.

[0067] In the configuration of this embodiment, when a temperature change occurs inside the battery, the temperature change can be directly detected. Therefore, unlike existing technology that uses a temperature sensor outside the battery, there is no need to wait for heat to be transferred from inside the battery to the outside, and deviations and time delays in temperature detection can be suppressed.

[0068] For example, if the storage battery 10 is left unused for a long period of time, the internal temperature of the storage battery 10 and the external temperature will become the same. In this case, by comparing the internal temperature (estimated temperature) of the storage battery 10 with the external temperature, it is possible to grasp the deviation in the correlation between temperature and dielectric constant. In this regard, since the temperature comparison is performed as described above and then a correction value for correcting the correlation is calculated, the accuracy of the temperature estimation in the storage battery 10 can be improved.

[0069] In the storage battery 10, wiring is generally connected to the positive terminal 14 and the negative terminal 15, and the terminal voltage and current flowing therethrough are measured as appropriate. In view of this, by utilizing existing measurement functions, the dielectric constant or capacitance of the storage battery 10 can be easily calculated. In other words, the temperature inside the battery can be suitably estimated using an existing configuration.

[0070] Incidentally, when a battery module is configured with a plurality of storage batteries 10 (in other words, when a battery pack is configured with a plurality of battery cells serving as storage batteries 10), a function for measuring the terminal voltage and current flow is provided for each storage battery 10. In this case, by making it possible to calculate the dielectric constant or capacitance of all storage batteries 10 in the battery module, it becomes possible to detect the voltage, current, and internal temperature of all storage batteries (all cells).

[0071] Third Embodiment The relative permittivity εr of the ferroelectric material added to the separator 24 of the storage battery 10 changes in response to changes in the temperature of the storage battery 10. For example, as shown in FIG. 8 , it is conceivable that εr is 1500 when the temperature of the storage battery 10 is 25° C., and εr is 5000 when the temperature of the storage battery 10 is 110° C. In this case, if the relative permittivity εr of the ferroelectric material of the separator 24 can be known during use of the storage battery 10, the temperature of the storage battery 10 can be determined. It is preferable that the temperature range corresponding to the εr of the ferroelectric material added to the separator 24 includes the melting temperature of the separator 24 or a temperature near that melting temperature. Note that the dielectric constant ε can also be used as a parameter instead of the relative permittivity εr.

[0072] Furthermore, impedance measurement is performed on the storage battery 10 by applying an AC signal with a frequency of, for example, about 1 to 10 kHz. In this case, the internal resistance of the storage battery 10 is calculated from the real part where the imaginary part becomes 0 (the real part at the zero crossing point) in a complex impedance plane plot (Cole-Cole plot) that shows the frequency characteristics of the storage battery 10. The real part at the zero crossing point mainly represents the solution resistance, which is the resistance when charge moves in the solution in the storage battery 10.

[0073] Here, according to the present inventors, it has been confirmed that in the frequency range (1 to 10 kHz) used to calculate the internal resistance of the storage battery 10, no difference occurs between the imaginary part and the real part of the impedance even if the relative dielectric constant εr of the ferroelectric substance of the separator 24 is different. In contrast, it has been confirmed that in a frequency range higher than the frequency range used to calculate the internal resistance, a difference occurs between the imaginary part and the real part of the impedance when the relative dielectric constant εr of the ferroelectric substance of the separator 24 is different.

[0074] 9 is a diagram showing an example of a complex impedance plane plot of the storage battery 10. In FIG. 9, (a) shows the impedance characteristics when the frequency is changed in the range of 0.1 Hz to 1 MHz, and (b) shows an enlarged view of the impedance characteristics of the X portion in (a), which includes the vicinity of the zero crossing point. FIG. 9 shows two characteristics when the relative dielectric constant εr is set to 1500 and 5000.

[0075] 9(b), i.e., at the X portion of FIG. 9(a), there is no difference in the impedance characteristics whether εr = 1500 or 5000, and the real part Re_Z calculated as the zero-crossing point is also the same. The real part Re_Z of the impedance decreases as the applied frequency increases. In contrast, in FIG. 9(a), in the region higher than the X portion, there is a difference in the impedance characteristics between εr = 1500 and εr = 5000, and the impedance measurement points at each frequency are different.

[0076] 9(a), the relationship shown in FIG. 10 can be derived as the relationship between frequency f and real part Re_Z. In FIG. 10, in frequency range Y, the real part Re_Z differs between when εr = 1500 and when εr = 5000. Frequency range Y is a frequency range from 20 to 800 kHz. In other words, by applying an AC signal of a predetermined frequency within frequency range Y to storage battery 10, a value corresponding to the relative permittivity εr of the ferroelectric substance in separator 24 can be derived as the real part Re_Z of the impedance.

[0077] For example, when an AC signal of frequency fa (e.g., 40 kHz) within frequency range Y is applied to storage battery 10, if the relative dielectric constant εr is 1500, the real part Re_Z will be A1, and if the relative dielectric constant εr is 5000, the real part Re_Z will be A2. Furthermore, if the relative dielectric constant εr is between 1500 and 5000, the real part Re_Z will be an intermediate value between A1 and A2.

[0078] In this embodiment, a control device 50 shown in FIG. 12 applies an AC signal having a frequency higher than the AC frequency corresponding to the zero-crossing point in the complex impedance characteristic of the storage battery 10, calculates the relative permittivity εr of the separator 24 based on a response signal obtained when the AC signal is applied, and monitors the internal temperature of the storage battery 10 based on the relative permittivity εr. In this case, the control device 50 analyzes the voltage fluctuation, which is the response signal, and calculates the real part Re_Z of the impedance. Furthermore, using the relationship shown in FIG. 10, the control device 50 calculates the relative permittivity εr of the ferroelectric material from the real part Re_Z and monitors the battery temperature based on the relative permittivity εr. The control device 50 is configured with a microcomputer having a CPU (arithmetic unit) and a storage device (various memories), and realizes various functions by executing programs stored in the storage device.

[0079] In this embodiment, the equivalent circuit of the storage battery 10 is assumed to have the configuration shown in FIG. 11 . In FIG. 11 , L is the inductance of the wound body 21 including the positive electrode current collector 26 and the negative electrode current collector 27. R1 is the resistance of the electrolyte, and C1 is the ferroelectric (barium titanate) capacitor component. R1 and C1 are connected in parallel. R2 is the combined resistance of the reaction resistance of the positive electrode active material (resistance during intercalation) and the reaction resistance of the negative electrode active material, and C2 is the combined capacitance of the electric double layer formed at the interface between the positive electrode active material and the electrolyte and the electric double layer formed at the interface between the negative electrode and the electrolyte. R2 and C2 are connected in parallel. Zcpe is the pseudocapacitance (constant phase element) impedance and is defined by the following equation:

[0080] j is the imaginary unit, ω is the angular frequency, p is the CPE exponent, and T is the CPE constant.

[0081] In FIG. 12 , the control device 50 includes an AC signal application unit 51, a response signal measurement unit 52, and a battery monitoring unit 53. The AC signal application unit 51 includes an oscillator that generates an AC signal of a predetermined frequency, and applies the AC signal of the predetermined frequency to the positive and negative terminals of the storage battery 10. In this embodiment, the AC signal application unit 51 applies an AC signal of a predetermined frequency in a frequency range of 1 to 10 kHz to the storage battery 10 when calculating the internal resistance of the storage battery 10, and applies an AC signal of a predetermined frequency in a frequency range of 20 to 800 kHz to the storage battery 10 when monitoring the temperature of the storage battery 10. In the following description, the frequency range of 1 to 10 kHz used when calculating the internal resistance of the storage battery 10 is referred to as a first frequency range Y1, and the frequency range of 20 to 800 kHz used when monitoring the temperature of the storage battery 10 is referred to as a second frequency range Y2. The AC signal may be a sine wave signal, a rectangular wave, a triangular wave, or the like.

[0082] When an AC signal of a predetermined frequency is applied to the storage battery 10 by the AC signal application unit 51, the response signal measurement unit 52 measures voltage fluctuations, which are information reflecting the impedance of the storage battery 10, as the response signal.

[0083] The battery monitoring unit 53 calculates the internal resistance and the relative dielectric constant εr of the storage battery 10 as battery parameters indicating the state of the storage battery 10, based on the response signal (voltage fluctuation) measured by the response signal measuring unit 52. Specifically, in the battery monitoring unit 53, when an AC signal of a predetermined frequency in the first frequency range Y1 is applied, the resistance calculating unit 53a calculates the real part Re_Z of the impedance as the internal resistance of the storage battery 10, based on the voltage fluctuation measured by the response signal measuring unit 52 and the amplitude of the AC current flowing through the storage battery 10 when the AC signal is applied.

[0084] Furthermore, when an AC signal of a predetermined frequency in the second frequency range Y2 is applied, the dielectric constant calculation unit 53b calculates the real part Re_Z of the impedance based on the voltage fluctuation measured by the response signal measurement unit 52 and the amplitude of the AC current flowing through the storage battery 10 when the AC signal is applied, and calculates the relative dielectric constant εr of the ferroelectric material from the real part Re_Z. Furthermore, the temperature monitoring unit 53c monitors whether the storage battery 10 is overheated based on the relative dielectric constant εr.

[0085] FIG. 13 is a flowchart showing the temperature monitoring process for the storage battery 10, which is executed by the control device 50 at predetermined intervals.

[0086] 13 , in step S21, it is determined whether or not an implementation condition for monitoring the temperature of the storage battery 10 is currently satisfied. This implementation condition is a condition for calculating the relative dielectric constant εr of the storage battery 10, and may be a condition that is satisfied at a predetermined period, for example, while the vehicle is running (while the IG is on) or after the vehicle has stopped running (after the IG is off). The predetermined period may be, for example, every few seconds, every few hundred milliseconds, or every few tens of milliseconds.

[0087] If the temperature monitoring implementation condition is not met, the process proceeds to step S22. In step S22, it is determined whether it is time to calculate the impedance. For example, immediately after the vehicle's IG is turned on, the impedance calculation condition is met, and a positive result is given in step S22. If a positive result is given in step S22, the process proceeds to step S23, where an AC signal of a predetermined frequency in the first frequency range Y1 is applied to the storage battery 10. Thereafter, in step S24, a voltage fluctuation in response to the AC signal is obtained as a response signal, and in the subsequent step S25, a real part Re_Z of the impedance is calculated based on the voltage fluctuation as the internal resistance of the storage battery 10.

[0088] If step S21 is positive, the process proceeds to step S26, where an AC signal of a predetermined frequency in the second frequency range Y2 is applied to the storage battery 10. Then, in step S27, a voltage fluctuation with respect to the AC signal is acquired as a response signal. In the following step S28, the real part Re_Z of the impedance is calculated based on the voltage fluctuation, and the relative dielectric constant εr of the ferroelectric material is calculated based on the real part Re_Z. At this time, the relationship between the real part Re_Z of the impedance and the relative dielectric constant εr may be defined as shown in FIG. 14 , and the relative dielectric constant εr of the ferroelectric material may be calculated from the real part Re_Z using this relationship.

[0089] Then, in step S29, it is determined whether the relative dielectric constant εr calculated in step S28 is greater than a predetermined threshold value Th. The threshold value Th is defined as a value corresponding to the melting temperature of the separator 24. In step S29, it is determined whether the internal temperature of the storage battery 10 has risen to the melting temperature of the separator 24 (e.g., 120°C) or a temperature close to the melting temperature (e.g., 110°C). If the relative dielectric constant εr is greater than the threshold value Th, it is determined that the internal temperature of the storage battery 10 has risen to a temperature equivalent to the melting temperature of the separator 24, and the result of step S29 is affirmative, and the process proceeds to step S30. In step S30, a user or the like is notified that there is a risk of thermal runaway in the storage battery 10.

[0090] According to the third embodiment described above, the following effect is achieved in addition to the effects already described.

[0091] An AC signal having a frequency higher than the AC frequency corresponding to the zero crossing point in the complex impedance characteristic is applied to the storage battery 10, and the relative dielectric constant εr of the separator 24 is calculated based on a response signal obtained in this state. Then, the internal temperature of the storage battery 10 is monitored based on the calculated relative dielectric constant εr. This makes it possible to appropriately grasp the internal temperature of the storage battery 10.

[0092] The AC signal applying unit 51 applies an AC signal of a first frequency (a frequency within a first frequency range Y1) for measuring complex impedance characteristics near a zero-crossing point, and an AC signal of a second frequency (a frequency within a second frequency range Y2) higher than the first frequency. The internal resistance of the storage battery 10 is calculated based on a response signal when the AC signal of the first frequency is applied, while the relative dielectric constant εr of the separator 24 is calculated based on a response signal when the AC signal of the second frequency is applied. In this case, the calculation of the internal resistance and the relative dielectric constant εr can be performed appropriately by selectively using an AC frequency suitable for calculating the internal resistance of the storage battery 10 and an AC frequency suitable for calculating the relative dielectric constant εr of the separator 24.

[0093] (Other Embodiments) The above-described embodiments may be modified as follows, for example.

[0094] The ferroelectric material added to the separator 24 of the storage battery 10 may have a dielectric constant that reaches a maximum value at a predetermined cryogenic temperature (for example, -10°C). In this case, the control device 40 (temperature monitoring unit) determines that the internal temperature of the storage battery 10 has dropped to the cryogenic temperature based on the dielectric constant or the capacitor capacity. This makes it possible to monitor the frequency of use of the storage battery 10 at cryogenic temperatures, for example, as the usage state of the storage battery 10.

[0095] In the third embodiment, the frequency of the AC signal is set to 1 to 10 kHz when calculating the internal resistance of the storage battery 10, and the frequency of the AC signal is set to 20 to 800 kHz when monitoring the temperature of the storage battery 10, but this can be changed. For example, when monitoring the temperature of the storage battery 10, the frequency of the AC signal may be set higher than when calculating the internal resistance of the storage battery 10, for example, 10 kHz or higher.

[0096] The frequency of calculating the relative dielectric constant εr may be increased when the temperature of the storage battery 10 is higher than a predetermined temperature that is lower than the melting temperature of the separator 24, compared to when the temperature is lower than the predetermined temperature. Specifically, the control device 50 may execute the process shown in FIG. 15. FIG. 15 is a partial modification of the flowchart shown in FIG. 13, and the same processes are denoted by the same step numbers.

[0097] 15 , in step S28, the relative permittivity εr of the ferroelectric substance is calculated based on the voltage fluctuation in response to the AC signal. Then, in step S31, it is determined whether the relative permittivity εr calculated in step S28 is greater than a predetermined first threshold value Th1. The first threshold value Th1 is set as a value corresponding to a predetermined temperature (e.g., 70°C) lower than the melting temperature (120°C) of the separator 24. The first threshold value Th1 may be equal to or higher than the upper limit temperature of the storage battery 10 during normal use. If the relative permittivity εr is equal to or less than the first threshold value Th1, the process is terminated. If the relative permittivity εr is greater than the first threshold value Th1, the process proceeds to step S32.

[0098] In step S32, it is determined that the frequency of calculation of the relative dielectric constant εr in the next and subsequent temperature monitoring processes will be higher than that in normal times (i.e., when εr≦Th1). For example, it is preferable to set the frequency of calculation of the relative dielectric constant εr to n times (n is 2 or more) the normal frequency. This increases the frequency of calculation of the relative dielectric constant εr in the next temperature monitoring process in response to a positive determination in step S21.

[0099] Then, in step S33, it is determined whether the relative dielectric constant εr is greater than a predetermined second threshold value Th2. The second threshold value Th2 is set to a value greater than the first threshold value Th1 and corresponding to the melting temperature of the separator 24. If the relative dielectric constant εr is greater than the second threshold value Th2, it is determined that the internal temperature of the storage battery 10 has risen to a temperature equivalent to the melting temperature of the separator 24, and the process proceeds to step S34. In step S34, a user or the like is notified that there is a risk of thermal runaway in the storage battery 10.

[0100] According to the above configuration, the frequency of calculating the relative dielectric constant εr is relatively low when the storage battery 10 is in a normal state, thereby reducing the computational load and power consumption, while the detection sensitivity of temperature rise can be temporarily increased if there is a concern about thermal runaway.

[0101] In addition to barium titanate, other ferroelectric materials that can be used include lead titanate, potassium niobate, lithium niobate, lead niobate, strontium barium niobate, lithium tantalate, sodium potassium tartrate (Rochelle salt), potassium dihydrogen phosphate, and glycine trisulfide. Furthermore, in addition to ferroelectric materials, paraelectric materials can also be used as materials whose dielectric constant changes with temperature. For example, paraelectric materials such as magnesium titanate, calcium titanate, titanium oxide (especially rutile type), strontium titanate, forsterite (2MgO.SiO2), and steatite (MgO.SiO2) can be used.

[0102] In the above embodiments, the present disclosure has been described as being applied to a can-type lithium-ion battery, but it may also be applied to a laminated lithium-ion battery. Furthermore, it may also be applied to batteries other than lithium-ion batteries, such as nickel-metal hydride batteries.

[0103] The controller and methods described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the controller and methods described herein may be implemented by a special-purpose computer configured with a processor configured with one or more dedicated hardware logic circuits. Alternatively, the controller and methods described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium.

[0104] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0105] The technical concepts extracted from the above-described embodiments are described below. [Configuration 1] A storage battery (10) including a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, wherein the separator is provided in a form containing a material whose dielectric constant changes depending on temperature. [Configuration 2] The storage battery according to Configuration 1, wherein a ferroelectric is used as the material. [Configuration 3] The storage battery according to Configuration 1, wherein the separator melts when the interior of the battery reaches a predetermined melting temperature, and wherein the material used is a ferroelectric whose Curie temperature, at which the dielectric constant reaches a maximum, is at or near the melting temperature of the separator. [Configuration 4] A battery unit comprising: the storage battery according to any one of Configurations 1 to 3; a calculation unit (31) that applies AC signals to the positive electrode layer and the negative electrode layer and calculates the dielectric constant or capacitor capacitance based on the response signal; and a temperature monitoring unit (32) that monitors the internal temperature of the storage battery based on the dielectric constant or capacitor capacitance calculated by the calculation unit. [Configuration 5] The battery unit according to Configuration 4, wherein in the storage battery, the separator melts when the interior of the battery reaches a predetermined melting temperature, the material is a ferroelectric whose Curie temperature at which its dielectric constant is maximized is at or near the melting temperature of the separator, and the temperature monitoring unit determines whether the internal temperature of the storage battery has risen to the predetermined temperature set as the melting temperature of the separator or near that temperature based on the dielectric constant or capacitor capacity calculated by the calculation unit. [Configuration 6] The battery unit according to Configuration 4, wherein the material includes a plurality of materials each having a different Curie temperature at which its dielectric constant is maximized, and a unique correlation between temperature and dielectric constant or capacitor capacity is set within a predetermined temperature range including the Curie temperatures of the respective materials, and the temperature monitoring unit uses the correlation to estimate the internal temperature of the storage battery based on the dielectric constant or capacitor capacity calculated by the calculation unit.a temperature monitoring unit (32) configured to monitor the internal temperature of the battery based on the dielectric constant or the capacitance of the capacitor calculated by the calculation unit; and a temperature determination unit (33) configured to determine whether the internal temperature of the battery is equal to the external temperature outside the battery and to calculate a correction value for correcting the correlation between the external temperature and the internal temperature of the battery when it is determined that the external temperature is equal to the internal temperature of the battery. [Configuration 8] A battery monitoring device (40) for use in a battery (10) comprising: a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form containing a material whose dielectric constant changes with temperature, the battery monitoring device comprising: a calculation unit (31) configured to apply AC signals to the positive electrode layer and the negative electrode layer and to calculate a dielectric constant or a capacitance of a capacitor based on a response signal; and a temperature monitoring unit (32) configured to monitor the internal temperature of the battery based on the dielectric constant or the capacitance of the capacitor calculated by the calculation unit. [Configuration 9] A battery monitoring device (50) applicable to the storage battery according to any one of Configurations 1 to 3, comprising: an AC signal application unit that applies, to the positive electrode layer and the negative electrode layer of the storage battery, an AC signal having a frequency higher than an AC frequency corresponding to a zero-cross point where the imaginary part of a complex impedance characteristic of the storage battery becomes zero, a calculation unit that calculates the dielectric constant of the separator based on a response signal in a state in which the AC signal is applied by the AC signal application unit, and a temperature monitoring unit that monitors an internal temperature of the storage battery based on the dielectric constant calculated by the calculation unit. [Configuration 10] The battery monitoring device according to Configuration 9, wherein the AC signal application unit applies an AC signal in a frequency range of 20 to 800 kHz as the AC signal.[Configuration 11] The battery monitoring device of Configuration 9 or 10, wherein the AC signal application unit applies an AC signal of a first frequency for measuring complex impedance characteristics near the zero-crossing point and an AC signal of a second frequency higher than the first frequency, and the calculation unit calculates the internal resistance of the storage battery based on the response signal when the AC signal of the first frequency is applied, and calculates the dielectric constant of the separator based on the response signal when the AC signal of the second frequency is applied. [Configuration 12] The battery monitoring device of any of Configurations 9 to 11, wherein the separator melts when the temperature of the storage battery reaches a predetermined melting temperature, and the calculation unit increases the calculation frequency of the dielectric constant when the temperature of the storage battery is higher than a predetermined temperature that is lower than the melting temperature, compared to when the temperature is lower than the predetermined temperature.

Claims

1. A storage battery (10) comprising a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form containing a material whose dielectric constant changes depending on temperature; a calculation unit (31) that applies an AC signal to the positive electrode layer and the negative electrode layer and calculates a dielectric constant or a capacitance based on a response signal; a temperature monitoring unit (32) that monitors an internal temperature of the storage battery based on the dielectric constant or the capacitor capacity calculated by the calculation unit; A battery unit comprising:

2. In the storage battery, the separator melts when the inside of the battery reaches a predetermined melting temperature, As the substance, a ferroelectric material is used whose Curie temperature at which the dielectric constant is maximized is the melting temperature of the separator or a temperature close to the melting temperature, 2. The battery unit according to claim 1, wherein the temperature monitoring unit determines whether the internal temperature of the storage battery has risen to a predetermined temperature defined as a melting temperature of the separator or a temperature close to the melting temperature, based on the dielectric constant or the capacitor capacity calculated by the calculation unit.

3. In the storage battery, the material includes a plurality of materials having different Curie temperatures at which the dielectric constant is maximized, and a unique correlation between temperature and the dielectric constant or the capacitance of the capacitor is determined within a predetermined temperature range including the Curie temperatures of the respective materials; The battery unit according to claim 1 , wherein the temperature monitoring unit estimates an internal temperature of the storage battery based on the dielectric constant or the capacitor capacity calculated by the calculation unit using the correlation.

4. a temperature determination unit that determines whether an internal temperature of the storage battery is equal to an external temperature outside the storage battery; a correction value calculation unit that, when it is determined that a situation is occurring in which the temperature of the storage battery and the external temperature are the same, calculates a correction value for correcting the correlation by comparing the external temperature in that situation with the internal temperature of the storage battery estimated by the temperature monitoring unit; The battery unit according to claim 3 .

5. A battery unit described in any one of claims 1 to 4, wherein a ferroelectric is used as the substance in the storage battery.

6. In the storage battery, the separator melts when the inside of the battery reaches a predetermined melting temperature, 5. The battery unit according to claim 1, wherein the substance used is a ferroelectric material whose Curie temperature at which the dielectric constant is at a maximum value is the melting temperature of the separator or a temperature close to the melting temperature.

7. A battery monitoring device (40) for use in a storage battery (10) comprising a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form containing a material whose dielectric constant changes depending on temperature, a calculation unit (31) that applies an AC signal to the positive electrode layer and the negative electrode layer and calculates a dielectric constant or a capacitance based on a response signal; A battery monitoring device comprising: a temperature monitoring unit (32) that monitors an internal temperature of the storage battery based on the dielectric constant or capacitor capacity calculated by the calculation unit.

8. A battery monitoring device (50) for use in a storage battery (10) comprising a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form containing a material whose dielectric constant changes with temperature, an AC signal application unit that applies, to the positive electrode layer and the negative electrode layer of the storage battery, an AC signal having a frequency higher than an AC frequency corresponding to a zero cross point at which an imaginary part becomes zero in a complex impedance characteristic of the storage battery; a calculation unit that calculates the dielectric constant of the separator based on a response signal when an AC signal is applied by the AC signal application unit; a temperature monitoring unit that monitors an internal temperature of the storage battery based on the dielectric constant calculated by the calculation unit; A battery monitoring device comprising:

9. 9. The battery monitoring device according to claim 8, wherein the AC signal application unit applies an AC signal in a frequency range of 20 to 800 kHz as the AC signal.

10. the AC signal application unit applies an AC signal of a first frequency for measuring a complex impedance characteristic in the vicinity of the zero crossing point, and an AC signal of a second frequency higher than the first frequency, 9. The battery monitoring device of claim 8, wherein the calculation unit calculates an internal resistance of the storage battery based on the response signal when the AC signal of the first frequency is applied, and calculates a dielectric constant of the separator based on the response signal when the AC signal of the second frequency is applied.

11. In the storage battery, the separator melts when the inside of the battery reaches a predetermined melting temperature, 9. The battery monitoring device according to claim 8, wherein the calculation unit increases the frequency of calculation of the dielectric constant when the temperature of the storage battery is higher than a predetermined temperature that is lower than the melting temperature, compared to when the temperature is lower than the predetermined temperature.

12. A program applied to a storage battery (10) comprising a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form including a material whose dielectric constant changes with temperature, the program being executed by a processor, A calculation process of applying an AC signal to the positive electrode layer and the negative electrode layer and calculating a dielectric constant or a capacitance based on a response signal; a temperature monitoring process for monitoring an internal temperature of the storage battery based on the dielectric constant or the capacitor capacity calculated by the calculation process; A program that executes the following.

13. A program applied to a storage battery (10) comprising a positive electrode layer (22), a negative electrode layer (23), and a separator (24) provided between the positive electrode layer and the negative electrode layer, the separator being provided in a form including a material whose dielectric constant changes with temperature, the program being executed by a processor, an AC signal application process for applying, to the positive electrode layer and the negative electrode layer of the storage battery, an AC signal having a frequency higher than an AC frequency corresponding to a zero crossing point at which an imaginary part becomes zero in a complex impedance characteristic of the storage battery; a calculation process of calculating a dielectric constant of the separator based on a response signal in a state in which an AC signal is applied by the AC signal application process; a temperature monitoring process for monitoring an internal temperature of the storage battery based on the dielectric constant calculated by the calculation process; A program that executes the following.