Estimation device, estimation method, and computer program

Abstract

To provide an estimation apparatus, an estimation method, and a computer program for estimating signs of abnormalities in power storage elements.SOLUTION: An estimation apparatus (2) has a first deriving unit (21) that derives estimation information including changes in the shape and / or pressure of a power storage element (12) having an anode, which deposits Li during charging and releases the Li into the electrolyte during discharge, and an outer body, and an estimation unit (21) that estimates the state of the power storage element (12) based on the estimated information derived.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an estimation device, an estimation method, and a computer program for estimating the state of an energy storage element.

Background Art

[0002] Energy storage elements that can store electrical energy and supply energy as a power source when needed are being used. Energy storage elements are applied to portable devices, power supply devices, transportation devices including automobiles and railways, industrial devices including those for aviation, space, and construction, and the like.

[0003] In order to achieve a higher capacity of the energy storage element (hereinafter also referred to as a battery), a higher capacity of the negative electrode is required. In the lithium secondary battery of Patent Document 1, it is disclosed that Li (lithium) metal is included as a negative electrode active material. By using Li metal for the negative electrode, the discharge capacity of the negative electrode is significantly improved from 372 mAh / g when using graphite to 3860 mAh / g. When a negative electrode containing Li metal is used, the potential of the negative electrode is always 0 V vs. Li / Li + and is lower than that when using graphite, and the battery voltage can be increased. Accordingly, the positive electrode can also exhibit a capacity at a lower potential, and the energy density of the battery is dramatically improved.

[0004] However, the battery gradually deteriorates as charging and discharging are repeated. Therefore, it is an important issue to easily and accurately estimate the SOH (State of Health: capacity retention rate, etc.) and the presence or absence of abnormalities of the battery when determining whether the battery can be used and how to use it.

[0005] On the one hand, in recent years, against the backdrop of environmental issues, the electrification in the aircraft industry has been progressing rapidly. For batteries used in aircraft, not only high energy density but also high safety and reliability are required. As a new communication system, HAPS (High-altitude platform station) has been proposed. An aircraft used for such applications, once taking off, will not return to the ground for a long time. Therefore, in case of an abnormality in the battery, it is necessary to take appropriate measures. However, it is difficult to take measures after the abnormality occurs. In addition, a battery containing Li metal as a negative electrode active material has a high energy density and is thus promising as one of the batteries for the aircraft.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] A battery containing Li metal as a negative electrode active material has a high energy density as described above, but Li may deposit in a dendrite shape during charging, piercing through the separator and causing a short circuit. That is, it may become an "abnormal state of the battery" with problems in safety and life characteristics. Different from a conventional lithium-ion secondary battery using graphite as a negative electrode active material, it is difficult to judge the abnormality of the battery based on current, voltage, and temperature. For measures such as controlling the charge and discharge of the battery by remote operation, it is necessary to detect the abnormality at an early stage. An object of the present invention is to provide an estimation device, an estimation method, and a computer program for estimating the state of a power storage element.

Means for Solving the Problems

[0008] An estimation device according to one aspect of the present invention includes a first derivation unit that derives estimation information including changes in the shape and / or pressure of a power storage element having a negative electrode that deposits Li during charging and releases the Li into an electrolytic solution during discharging, and an outer package, and an estimation unit that estimates the state of the power storage element based on the derived estimation information.

[0009] An estimation method according to one aspect of the present invention derives estimation information including changes in the shape and / or pressure of a power storage element having a negative electrode that deposits Li during charging and releases the Li into an electrolytic solution during discharging, and an outer package, and estimates the state of the power storage element based on the derived estimation information.

[0010] A computer program according to one aspect of the present invention causes a computer to execute a process of deriving estimation information including changes in the shape and / or pressure of a power storage element having a negative electrode that deposits Li during charging and releases the Li into an electrolytic solution during discharging, and an outer package, and estimating the state of the power storage element based on the derived estimation information.

Advantages of the Invention

[0011] According to the above aspect, the state of the power storage element can be estimated.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Mode for Carrying Out the Invention

[0013] (Outline of Embodiment) In this specification, the "power storage element" may be at least a battery, a battery cell (or cell), a battery module, or a battery pack. Further, the power storage element may be an electric double layer capacitor, a capacitor, or the like. In the case of a carbon negative electrode containing graphite or the like as an active material, the active material has a layered structure, and the expansion of the active material due to the intercalation of Li (lithium) during charging and the contraction of the active material due to the release of Li during discharging occur as theorized. As the number of cycles increases, a new interface is generated due to the expansion and contraction of the active material, and an SEI (Solid Electrolyte Interphase) film is formed on this interface, increasing the thickness of the negative electrode and the thickness of the energy storage element (cell). However, the thickness increase rate at the end of the life is about 10% at maximum.

[0014] Figure 1 is a graph showing the relationship between the cumulative amount of energized electricity of the energy storage element and the thickness increase rate. In Figure 1, a is an energy storage element having a negative electrode containing Li metal as an active material (capacity per unit area of the positive and negative electrodes: 6 mAh / cm 2 ), b is an energy storage element having a negative electrode containing an active material of 50% graphite and 50% Si (silicon) (capacity per unit area of the positive and negative electrodes: 4.7 mAh / cm 2 ), c is an energy storage element having a negative electrode containing an active material of 20% graphite and 80% SiO (capacity per unit area of the positive and negative electrodes: 7.5 mAh / cm 2 ), d is an energy storage element having a negative electrode containing an active material of 40% graphite and 60% SiO (capacity per unit area of the positive and negative electrodes: 7.4 mAh / cm 2 ). Here, O is oxygen. In Figure 1, the horizontal axis represents the cumulative amount of electricity (mAh), and the vertical axis represents the thickness increase rate (%). From Figure 1, it can be seen that the thickness increase rate over time of the energy storage element having the Li metal negative electrode a is the largest. The thickness of the energy storage element is due to the increase in the thickness of the negative electrode.

[0015] Figure 2 is an explanatory diagram for explaining the process of thickness increase in the Li metal negative electrode. The negative electrode plate is formed by forming an active material layer 62 made of Li metal on a base material foil 61 which is a plate-like metal foil made of a metal such as copper or an alloy of copper or the like.

[0016] During charging, Li is deposited on the active material layer 62, and a deposited Li layer 63 is formed. A film 64 made of decomposition products of electrolyte components, etc., called an SEI film, is formed on the surface of the deposited Li layer 63 (Fig. 2A). During discharging, the Li in the deposited Li layer 63 is released into the electrolyte, but not all of it dissolves, and a part of Li63a remains on the active material layer 62, making the surface of the active material layer 62 non-uniform (Fig. 2B).

[0017] When Li is deposited on the active material layer 62 during charging, since it is formed on the non-uniform surface of the active material layer 62, the deposited Li layer 63 is formed in a state with irregularities. The film 64 is formed on the deposited Li layer 63 with such irregularities (Fig. 2C). When charge and discharge are repeated, the degree of irregularities increases, and the deposited Li layer 63 and the film 64 are formed (Fig. 2D).

[0018] Li is surrounded by the film 64, and this Li becomes dead Li63b that does not participate in the battery reaction (Fig. 2E). The film 64 containing the dead Li63b has a gap between the surface of the active material layer 62 and other films 64 as shown in Fig. 2E. During discharging, a part of the film 64 containing the dead Li is released into the electrolyte in a state containing the dead Li63b. A part of the film 64 containing the dead Li remains on the surface of the active material layer 62 with its root part attached to the active material layer 62 during discharging. It means that a porous film 64 is formed on the surface of the active material layer 62.

[0019] During charging, the Li ions in the electrolyte enter through the gap part of the film 64 with low resistance and are deposited on the surface of the active material layer 62. Li metal is deposited unevenly on the active material layer 62, and dendrites 63c are generated. The thickness of the deposits of the dendrites 63c and the porous film 64 containing the dead Li63b increases (Fig. 2F).

[0020] As described above, in the case of the carbon negative electrode storage element, the increase rate of the thickness of the storage element is at most 10%. However, in the case of the Li metal negative electrode, due to the increase in the thickness of the deposit of the porous film 64, dendrite 63c grows, and thereby, the increase in the thickness of the deposit of the porous film 64 is further accelerated. Thus, along with the rapid increase in the thickness of the negative electrode, dendrite 63c grows rapidly and breaks through the separator, resulting in a short circuit. Since the thickness increases rapidly and a short circuit occurs, unlike a conventional lithium-ion secondary battery using graphite as a negative electrode active material, it is impossible to detect an abnormality and predict a short circuit from current, voltage, and temperature information.

[0021] The inventors of the present invention have found that by monitoring the shape change of the storage element, that is, the change in thickness, the state of the storage element can be estimated, and an abnormality, that is, a sign of a short circuit, can be detected (determined). FIG. 3 is an image diagram showing the relationship between time and the thickness of the storage element. When deviating from the first relationship between the amount of electricity and the thickness increase rate shown in a etc. of FIG. 1, that is, when the thickness increase rate with respect to time is large, it is an abnormal state, and there is a very high possibility of a short circuit due to the growth of Li dendrites. By monitoring the thickness of the storage element, the state of the storage element can be estimated and a sign of an abnormality can be detected.

[0022] The estimation device according to the embodiment includes a first derivation unit that derives estimation information including a change in the shape and / or pressure of a storage element having a negative electrode on which Li is deposited during charging and releases the Li into an electrolytic solution during discharging, and an outer package, and an estimation unit that estimates the state of the storage element based on the derived estimation information.

[0023] Here, examples of the negative electrode include a metal negative electrode containing a metal such as Li metal or Na (sodium). Here, the change in shape and / or pressure refers to the displacement amount related to the shape change such as the thickness of the power generation element, the displacement amount of the exterior body that houses the power generation element, the change in the force (reaction force) by which the exterior body expands outward, the change in the pressure applied to at least one surface of the power storage element, or the change in the pressure applied to at least a part of the exterior body, or a combination thereof. The power generation element is formed by laminating a positive electrode plate, a separator, and a negative electrode plate, or by winding a positive electrode plate and a negative electrode plate flatly with a separator in between. The displacement amount may be the displacement amount in the thickness direction (the direction intersecting the long side surface) of the power generation element or the exterior body, or may be the displacement amount of, for example, a tapered portion of the laminated film exterior body where the terminal protrudes.

[0024] The change in the shape and / or pressure of the power storage element can be obtained by means of a thickness sensor, a pressure sensor, imaging by a camera, or the like. Examples of the thickness sensor include an X-ray CT (computed tomography) device, a laser displacement sensor, or a strain sensor (strain gauge). The pressure sensor may measure the compressive force (constraint force) of a pair of end plates that sandwich the stacked power storage elements in a state of compressing them in the stacking direction. When the internal pressure of the power storage element increases, the compressive force between the end plates increases. The pressure sensor may measure the reaction force of individual power storage elements or the pressure applied to at least one surface of the power storage element. Regardless of whether the power storage element is in a completely constrained state, a free state, or an intermediate state between them, the shape change can be obtained to detect signs of abnormality in the power storage element.

[0025] The exterior body may include a laminated film or may be made of a metal can. The laminated film is a film in which resin film layers are laminated and adhered (laminated) on both sides of a metal layer, and aluminum, nickel, or the like can be used for the metal layer.

[0026] According to the above configuration, by deriving estimation information including changes in the shape and / or pressure of the energy storage element, changes in the shape and / or pressure of the negative electrode can be estimated, and based on the estimation information, the state (degree of abnormality) of the energy storage element can be estimated. Based on the state of the energy storage element, the omen of abnormality can be accurately detected.

[0027] In the above-described estimation device, the estimation information may be information on changes in the shape and / or pressure of the energy storage element caused by deposits on the negative electrode including a SEI film containing dead Li that does not participate in the reaction and Li dendrites.

[0028] As described above, since the thickness of the deposits of the porous SEI film including dendrites and dead Li increases rapidly, the state of the energy storage element can be accurately estimated based on the information on these deposits.

[0029] In the above-described estimation device, the negative electrode may have an active material containing Li metal.

[0030] In the case of a negative electrode having an active material containing Li metal, the amount of change in shape is large, and the change may occur suddenly. By deriving changes in the shape and / or pressure of the energy storage element, the amount of change in the shape of the negative electrode can be grasped, and the state of the energy storage element can be accurately estimated.

[0031] In the above-described estimation device, when the estimation information is input, the estimation information derived by the first derivation unit may be input to a learning model that outputs information related to the state of the energy storage element, and the state of the energy storage element may be estimated.

[0032] According to the above configuration, the state of the energy storage element can be easily and accurately estimated.

[0033] In the above-described estimation device, a determination unit may be provided that determines the presence or absence of an omen of abnormality based on the state of the energy storage element estimated by the estimation unit.

[0034] According to the above configuration, it is possible to accurately determine the sign of an abnormality such as a short circuit based on the state of the energy storage element.

[0035] The estimation device according to the embodiment includes a first derivation unit that derives estimation information including a change in the shape and / or pressure of an energy storage element having a negative electrode on which Li is deposited during charging and releases the Li into an electrolytic solution during discharging, and an exterior body, and a determination unit that inputs the estimation information derived by the first derivation unit into a learning model that outputs information related to the sign of an abnormality of the energy storage element to determine the presence or absence of the sign of an abnormality of the energy storage element.

[0036] According to the above configuration, it is possible to easily and accurately determine the presence or absence of a sign of an energy storage element.

[0037] In the above-described estimation device, a power supply control unit that stops energization at least during charging may be provided for the energy storage element specified based on the state estimated by the estimation unit or the sign of the abnormality determined by the determination unit.

[0038] According to the above configuration, it is possible to prevent the occurrence of an abnormality by not energizing at least during charging the energy storage element in which a sign of an abnormality such as a short circuit is detected.

[0039] In the above-described estimation device, a discharge control unit that discharges the energy storage element whose energization has been stopped by the power supply control unit may be provided.

[0040] According to the above configuration, when it becomes difficult to operate only with the energy storage element in use, the operation can be executed by discharging the energy storage element whose energization has been stopped after restoring it.

[0041] In the above-described estimation device, a second derivation unit that derives the resistance of a plurality of energy storage elements whose energization has been stopped by the power supply control unit may be provided, and the discharge control unit may discharge the energy storage element selected based on the resistance derived by the second derivation unit.

[0042] It is presumed that the state of a rapid increase in the thickness of the negative electrode, which is the main factor of the change, remains unchanged among the power storage elements in which power supply has been stopped based on the change in the shape and / or pressure of the power storage element. The resistance of the power storage element is the sum of the resistances of not only the amount of dendrites but also the positive electrode, negative electrode, electrolytic solution, current collector, etc., and there are variations for each power storage element. When power storage elements are connected in series, it is considered that the greater the resistance of the power storage element, the greater the amount of heat generated and the higher the temperature of the power storage element. Dendrites formed in a state where the temperature of the power storage element is high tend to be less likely to cause a short circuit. When the temperature of the power storage element is high, the form of deposition of Li metal changes, that is, the dendrites become granular instead of resinous and are less likely to grow tall. Among several conceivable selection methods for power storage elements, for example, by selecting a power storage element with a high resistance among those in which power supply has been stopped, the possibility of a short circuit occurring during use can be reduced, and the operation can be executed safely.

[0043] The estimation method according to the embodiment derives estimation information including changes in the shape and / or pressure of a power storage element having a negative electrode in which Li is deposited during charging and the Li is released into the electrolytic solution during discharging, and an exterior body, and estimates the state of the power storage element based on the derived estimation information.

[0044] According to the above configuration, the state of the power storage element can be accurately estimated based on the estimation information.

[0045] The computer program according to the embodiment causes a computer to execute a process of deriving estimation information including changes in the shape and / or pressure of a power storage element having a negative electrode in which Li is deposited during charging and the Li is released into the electrolytic solution during discharging, and an exterior body, and estimating the state of the power storage element based on the derived estimation information.

[0046] According to the above configuration, the state of the power storage element can be accurately detected based on the estimation information.

[0047] (Embodiment 1) FIG. 4 is a block diagram showing the configuration of the charge-discharge system 30 and the server 40 according to Embodiment 1. The charge-discharge system 30 is provided in, for example, transportation equipment including automobiles and railways, industrial equipment including aviation, space, and construction, etc., and examples include those with a large depth during one discharge of the battery module 1.

[0048] The charge-discharge system 30 includes a battery module 1, a control device 2, a voltage sensor 6, a current sensor 7, a temperature sensor 8, a thickness sensor 9, a pressure sensor 10, and a camera 20.

[0049] In the battery module 1, lithium secondary batteries (hereinafter referred to as cells) 12 as a plurality of power storage elements are connected in series. The control device 2 controls the entire charge-discharge system 30. The control device 2 includes a control unit 21, a storage unit 22, an input unit 23, and a communication unit 24. The server 40 includes a control unit 41 and a communication unit 42. The control unit 21 of the control device 2 is connected to the control unit 41 via the communication unit 24, the network NW, and the communication unit 42. The load 3 is connected to the battery module 1 via terminals 31, 32. When charging, a charger is connected to the battery module 1.

[0050] The control units 21 and 41 are each constituted by, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), etc., and control the operations of the control device 2 and the server 40, respectively.

[0051] The storage unit 22 stores various programs and data. In the storage unit 22, an abnormality degree estimation program 221 (hereinafter referred to as program 221), a power supply control program 222 (hereinafter referred to as program 222), and a discharge control program 223 (hereinafter referred to as program 223) are stored. Programs 221, 222, and 223 are provided in a state of being stored in computer-readable recording media 25, 26, 27 such as a CD-ROM, a DVD-ROM, and a USB (universal serial bus) memory, and are stored in the storage unit 22 by being installed in the control device 2. Alternatively, programs 221, 222, and 223 may be acquired from an external computer (not shown) connected to the communication network and stored in the storage unit 22.

[0052] The storage unit 22 also stores a history DB (database) 224. FIG. 5 is an explanatory diagram showing an example of the record layout of the history DB 224. The history DB 224 stores, for each cell 12 and for each estimated time point in charging, current, voltage, temperature, SOC (State of Charge), pressure, thickness, image data, displacement amount obtained by processing the image data, and degree of abnormality. FIG. 5 shows the history of cell 12 with IDNo.1. The history DB 224 stores a No. column, a current column, a voltage column, a temperature column, an SOC column, a pressure column, a thickness column, an image data column, an image column of the displacement amount column, and a degree of abnormality column. The history DB 224 may further store a time (date and time) column.

[0053] The "No." column stores the No. (number of times) of the abnormality degree estimation process. Since a short circuit is caused by the growth of dendrites during charging, the estimation process may be performed at predetermined intervals during charging. The "Current" column stores the history of the current acquired from the current sensor 7 at the time of estimation. The "Voltage" column stores the voltage acquired from the voltage sensor 6 at the time of estimation. The "Temperature" column stores the temperature acquired from the temperature sensor 8 at the time of estimation. The "SOC" column stores the SOC at the time of estimation. The SOC is derived by the current integration method or the like. The "Pressure" column stores the pressure acquired from the pressure sensor 10 at the time of estimation. The "Thickness" column stores the thickness acquired from the thickness sensor 9 at the time of estimation. The "Image Data" column stores the image data acquired by the camera 20 at the time of estimation. The "Displacement Amount" column stores the displacement amount from the initial state obtained by processing the image data by an image processing program (not shown) stored in the storage unit 22. The "Abnormality Degree" column stores the abnormality degree derived based on the rule base described later. The abnormality degree is represented in four levels from 0 to 3. "0" indicates a normal state with no sign of abnormality, and the thickness of the cell 12 increases as the numerical value increases. When it reaches "3", it is necessary to take measures to prevent the occurrence of an abnormal state. The abnormality degree is estimated based on thresholds such as pressure, thickness, and displacement amount. The threshold values are obtained for pressure, thickness, displacement amount, etc. when the probability of a short circuit caused by dendrites is high, and are set smaller than the obtained pressure, thickness, and displacement amount to surely prevent a short circuit. Based on the rule base described later, the abnormality degree is estimated at the time of estimation based on the actually measured and derived pressure, thickness, and displacement amount. The abnormality degree is not limited to the case of four levels. The history DB 224 may store a "Presence / Absence of Sign" column that stores the presence or absence of a sign instead of the "Abnormality Degree" column, or may store the "Presence / Absence of Sign" column in addition to the "Abnormality Degree" column.

[0054] The relationship DB 225 stores a rule-based model. FIG. 6 is an explanatory diagram showing an example of a rule-based model for estimating the degree of abnormality. In FIG. 6A, for the sake of convenience, four cases from No. 1 to No. 4 will be described. In the case of No. 1, the pressure is less than the threshold value, the thickness is less than the threshold value, the displacement amount is less than the threshold value, and the degree of abnormality is "0". Similarly, in the case of No. 2, the degree of abnormality is "1", in the case of No. 3, the degree of abnormality is "2", and in the case of No. 4, the degree of abnormality is "3". Here, the case of deriving a four-level degree of abnormality using pressure, thickness, and displacement amount will be described, but it is not limited to this case. Any one of pressure, thickness, and displacement amount may be used, or current, voltage, temperature, SOC, or time, etc. may be used. Further, a value obtained by calculating these quantities (for example, the time change rate of thickness, etc.) may be used. Note that the displacement amount may be, for example, the deformation amount of one cell 12 measured by the camera 20, or the deformation amount of the entire battery module 1 including the cell 12. The thickness may be, for example, the thickness of one cell 12 measured by the thickness sensor 9, or the thickness of the entire battery module 1 including the cell 12.

[0055] FIG. 6B shows an example of a rule-based model using thickness, the time change rate of thickness, pressure, and the time change rate of pressure. In case No. 1 shown in FIG. 6B, the thickness, the time change rate of thickness, pressure, and the time change rate of pressure are all less than the threshold value, and the degree of abnormality is "0". In cases No. 2 to No. 5, any one of the thickness, the time change rate of thickness, pressure, and the time change rate of pressure is greater than or equal to the threshold value, and the others are less than the threshold value, and the degree of abnormality is "1". In cases No. 6 to No. 11, any two of the thickness, the time change rate of thickness, pressure, and the time change rate of pressure are greater than or equal to the threshold value, and the others are less than the threshold value, and the degree of abnormality is "2". In cases No. 12 to No. 15, any one of the thickness, the time change rate of thickness, pressure, and the time change rate of pressure is less than the threshold value, and the others are greater than or equal to the threshold value, and the degree of abnormality is "3". In case No. 16, the thickness, the time change rate of thickness, pressure, and the time change rate of pressure are all greater than or equal to the threshold value, and the degree of abnormality is "3". Thus, the degree of abnormality can be determined according to the comparison between the thickness, the time change rate of thickness, pressure, and the time change rate of pressure and the threshold value.

[0056] The relational DB 225 may store the first relationship between the time in the normal state as shown in FIG. 3 and the thickness of the cell. In this case, the state of the cell 12 is estimated based on whether the second relationship between the time and the change in the thickness of the cell 12 to be estimated deviates from the first relationship, and the presence or absence of a sign is determined based on whether the thickness exceeds the threshold value of the sign, etc.

[0057] The communication units 24 and 42 have a function of communicating with other devices via the network NW and can transmit and receive required information.

[0058] In the present embodiment, either the control device 2 or the server 40 functions as the estimation device of the present invention. Further, the entire system including the control device 2 and the server 40 is the estimation device of the present invention, and the control device 2 may function as the first derivation unit and the server 40 may function as the estimation unit. Note that when the server 40 does not function as the estimation device, the charge and discharge system 30 may not be connected to the server 40. The control device 2 may be a battery ECU (Electronic Control Unit).

[0059] The voltage sensor 6 is connected in parallel to the battery module 1 and outputs a detection result corresponding to the overall voltage of the battery module 1. The voltage sensor 6 is connected to the positive electrode terminal 12b and the negative electrode terminal 12c of each cell 12, which will be described later, measures the voltage V1 between the positive electrode terminal 12b and the negative electrode terminal 12c of each cell 12, and detects the voltage V, which is the sum value of V1 of each cell 12.

[0060] The current sensor 7 is connected in series to the battery module 1 and outputs a detection result corresponding to the current of the battery module 1. The thickness sensor 9 consists of an X-ray CT device, a laser displacement sensor, a strain sensor, or the like. The thickness sensor 9 measures the thickness of the cells 12 of the battery module 1 in the stacking direction.

[0061] The pressure sensor 10 measures the compressive force of a pair of end plates 17, which will be described later, that sandwich the battery module 1 in a state of compressing it in the stacking direction. When the internal pressure of the cell 12 increases due to deterioration, the compressive force between the end plates 17 increases. The pressure sensor 10 may measure the force spreading outside the battery module 1 or the pressure applied to at least one surface of the battery module 1. The internal pressure of each individual cell 12 may be measured by the pressure sensor 10. The bulge of the cell 12 arranged at the outermost position on one side of the battery module 1 may be used. The bulge (deformation) of the end plate 17 may be measured. The gap between the cells 12 may be measured. Also, the compressive force (compression force) of the end plate 17 of the cell 12 may be measured, and the compressive force may be used as a substitute for the bulge amount. Examples of the method for measuring the compressive force include methods such as pushing in the end plate 17 to measure the repulsive force and removing the fixing bolt to measure the repulsive force. The camera 20 images a portion where the terminal protrudes from the power generation element 12a and is tapered, of the exterior body 12f of each cell 12, which will be described later.

[0062] FIG. 4 shows a case where one set of battery modules 1 is provided, but a plurality of sets of battery modules 1 may be connected in series. The battery module 1 includes a plurality of battery circuits 11. Each battery circuit 11 includes one cell 12 and is a circuit through which current flows when the battery module 1 charges and discharges. The plurality of battery circuits 11 are connected in series. When the battery module 1 charges and discharges, current flows through the plurality of battery circuits 11, and the plurality of cells 12 charge and discharge.

[0063] The battery circuit 11 includes a first circuit 13, a cell 12 provided on the first circuit 13, and a first switch 14 provided on the first circuit 13 and connected in series with the cell 12. The cell 12 is connected to an adjacent battery circuit 11 via the first circuit 13 and the first switch 14. The first switch 14 is configured using a FET (field effect transistor). The first switch 14 is provided on the first circuit 13 such that the forward direction of its body diode is the charging direction of the battery module 1. The first switch 14 conducts the first circuit 13 when it is on and makes the first circuit 13 non-conductive in the discharge direction of the battery module 1 when it is off. Specifically, when the first switch 14 is on, the cell 12 is connected to other battery circuits 11 through the first circuit 13 and can charge and discharge. When the first switch 14 is off, no current flows in the discharge direction through the cell 12, but current flows in the charging direction through the body diode of the first switch 14.

[0064] The battery circuit 11 further includes a second circuit 15 connected in parallel to the cell 12 and the first switch 14 to another battery circuit 11, and a second switch 16 provided in the second circuit 15. The second switch 16 is configured using an FET. The first switch 14 and the second switch 16 are connected in the battery circuit 11 so as to have opposite polarities to each other. The second switch 16 is provided in the second circuit 15 such that the forward direction of its body diode is the discharge direction of the battery module 1. In a certain battery circuit 11, when the first switch 14 is turned off and the second switch 16 is turned on, the charging current does not flow to the cell 12, and the second circuit 15 serves as a bypass and bypasses the cell 12, and the charging current flows to other battery circuits.

[0065] The second switch 16 renders the second circuit 15 in a conductive state when it is on, and renders the second circuit 15 in a non-conductive state in the charging direction of the battery module 1 when it is off. When the first switch 14 is on and the second switch 16 is off, the cell 12 is connected to other battery circuits 11 through the first circuit 13.

[0066] FIG. 7 is a cross-sectional view of the battery module 1, and FIG. 8 is a perspective view of the cell 12. The cell 12 includes a power generation element 12a, a positive electrode terminal 12b, a negative electrode terminal 12c, and an exterior body 12f composed of laminate films 12d and 12e. The exterior body 12f is formed by overlapping two laminate films 12d and 12e and welding the peripheral portions. The positive electrode terminal 12b and the negative electrode terminal 12c protruding from the power generation element 12a are drawn out to the outside through the welded portion of the exterior body 12f. For example, the laminate films 12d and 12e are laminated in this order with a PE welding layer, a PET layer, an aluminum layer, a PET layer, and a PE welding layer from the inside where the power generation element 12a is disposed toward the outside. The configuration of the lamination is not limited to this case. A plurality of cells 12 are sandwiched between a pair of end plates 17, 17 in a state of being compressed in the stacking direction.

[0067] The power generation element 12a is formed by laminating a positive electrode plate, a separator, and a negative electrode plate, and is housed in the exterior body 12f. The negative electrode plate corresponds to the negative electrode in the present invention. The power generation element 12a may be obtained by winding a positive electrode plate and a negative electrode plate flatly with a separator interposed therebetween, or may be obtained by laminating a plurality of positive electrode plates and negative electrode plates with a separator interposed therebetween.

[0068] The positive electrode plate is one in which an active material layer is formed on a positive electrode base material foil which is a plate-shaped (sheet-shaped) or long-strip-shaped metal foil made of a metal such as aluminum, titanium, tantalum, stainless steel or an alloy thereof. The negative electrode plate is one in which an active material layer is formed on a negative electrode base material foil which is a plate-shaped (sheet-shaped) or long-strip-shaped metal foil made of a metal such as copper, nickel, stainless steel, nickel-plated steel or an alloy thereof. The separator is a microporous sheet made of a synthetic resin.

[0069] As the positive electrode active material, for example, it can be appropriately selected from known positive electrode active materials. As the positive electrode active material for a lithium secondary battery, a material that can usually occlude and release Li ions is used. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2-type crystal structure, lithium transition metal oxides having a spinel-type crystal structure, and the like. Here, Fe is iron. As the lithium transition metal composite oxide having an α-NaFeO2-type crystal structure, for example, Li[Li x Ni 1-x O2 (0 ≦ x < 0.5), Li[Li x Ni γ Co (1-x-γ) O2 (0 ≦ x < 0.5, 0 < γ < 1), Li[Li x Co (1-x) O2 (0 ≦ x < 0.5), Li[Li x Ni γ Mn (1-x-γ) O2 (0 ≦ x < 0.5, 0 < γ < 1), Li[Li x Ni γ Mn β Co (1-x-γ-β) O2 (0 ≦ x < 0.5, 0 < γ, 0 < β, 0.5 < γ + β ≦ 1), Li[Li xNi γ Co β Al (1-x-γ-β) O2 (0 ≦ x < 0.5, 0 < γ, 0 < β, 0.5 < γ + β < 1), etc. Here, Ni is nickel, Co is cobalt, and Al is aluminum. As the lithium transition metal oxide having a spinel crystal structure, Li x Mn2O4, Li x Ni γ Mn (2-γ) O4, etc. may be mentioned. These materials may be coated with other materials on the surface. In the positive electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used. In the positive electrode active material layer, one of these compounds may be used alone, or two or more of them may be mixed and used. The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but as the lower limit, 50% by mass is preferable, 80% by mass is more preferable, and 90% by mass is even more preferable. As the upper limit of the content, 99% by mass is preferable, and 98% by mass is more preferable.

[0070] The positive electrode mixture for forming the active material layer of the positive electrode plate contains optional components such as a conductive agent, a binder, a thickener, and a filler as necessary. Examples of the conductive agent include carbonaceous materials such as carbon black, metals, and conductive ceramics. Examples of the binder include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), and thermoplastic resins such as polyethylene, polypropylene, and polyimide. Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. Examples of the filler include polyolefins such as polypropylene and polyethylene.

[0071] As the negative electrode active material used in the negative electrode active material layer, it is preferable to contain Li metal. Since the negative electrode active material contains Li metal, it has surplus Li ions, and can transfer Li ions from the negative electrode plate to the positive electrode plate to exhibit the required discharge capacity. Li metal includes not only Li alone but also Li alloys. Examples of the Li alloy include LiAl alloy and the like. The negative electrode plate containing Li metal can be manufactured by cutting Li metal into a predetermined shape or forming it into a predetermined shape. In this case, the negative electrode substrate made of stainless steel may be connected only to the end of the Li metal plate.

[0072] Furthermore, the negative electrode active material layer may contain elements such as Na, K (potassium), Ca (calcium), Fe, Mg (magnesium), Si, N (nitrogen), etc. The negative electrode active material may contain Li metal and Si or SiO. As the lower limit of the content of Li metal in the above negative electrode active material, 80% by mass is preferable, 90% by mass is more preferable, and 95% by mass is even more preferable. The upper limit of the content may be 100% by mass.

[0073] An electrolytic solution is injected into the exterior body 12f. The electrolytic solution includes a non-aqueous solvent, and a sulfur-based cyclic compound, a fluorinated cyclic carbonate, a chain carbonate, and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the sulfur-based cyclic compound include compounds having a sultone structure or a cyclic sulfate structure. Examples of the fluorinated cyclic carbonate include fluoroethylene carbonate and the like. Examples of the chain carbonate include ethyl methyl carbonate, dimethyl carbonate, and the like.

[0074] The negative electrode active material of the cell 12 may contain Li metal and the positive electrode active material may be a lithium-excess type. According to such a cell 12, a high discharge capacity can be exhibited.

[0075] The positive electrode active material is Li x (Ni a Co b Mn c)It may be a ternary system such as NCM (mixed cathode active material of Ni + Co + Mn system) represented by O2 (a + b + c = 1, 0 < x < 1.1), or it may be a Li-excess type.

[0076] The positive electrode terminals 12b and negative electrode terminals 12c of adjacent cells 12 of the battery module 1 are electrically connected by a bus bar (not shown), whereby a plurality of cells 12 are connected in series. Positive electrode leads and negative electrode leads (not shown) for extracting electric power are provided at the positive electrode terminals 12b and negative electrode terminals 12c of the cells 12 at both ends of the battery module 1. The exterior body 12f of the cell 12 may be made of a metal can.

[0077] A specific example of the cell 12 will be described. [Fabrication of positive electrode plate] As the positive electrode active material, a lithium transition metal composite oxide having an α-NaFeO2 type crystal structure and represented by Li 1+α Me 1-α O2 (Me is a transition metal) is used. Here, the molar ratio Li / Me of Li and Me is 1.33, and Me consists of Ni and Mn and contains them in a molar ratio of Ni:Mn = 1:2.

[0078] Using N-methylpyrrolidone (NMP) as a dispersion medium, a positive electrode paste containing the positive electrode active material, acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 92.5:4.5:3.0 is prepared. The positive electrode paste is applied to both sides of an aluminum foil with a thickness of 15 μm as a positive electrode substrate, dried, pressed, cut, and a positive electrode plate with a positive electrode active material layer arranged in a rectangular shape with a width of 30 mm and a length of 40 mm is prepared. The thickness of the positive electrode active material layer is about 110 μm on one side, and the positive electrode mixture contains 26 mg / cm 2 per unit area. The positive electrode plate is dried under reduced pressure at 120 °C for 14 hours or more before use.

[0079] [Fabrication of negative electrode plate] On both sides of an 8-μm copper foil serving as a negative electrode substrate, a metallic lithium foil (average thickness: 100 μm, pure metallic lithium with 100% by mass of metallic lithium) was laminated as a negative electrode active material layer and pressed. Thereby, a negative electrode plate having negative electrode active material layers laminated on both sides of the negative electrode substrate was obtained. The above negative electrode plate has a rectangular shape with a width of 30 mm and a length of 42 mm.

[0080] [Preparation of Electrolyte Solution] LiPF6 was dissolved in a mixed solvent in which fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) were mixed at a volume ratio of FEC:DMC = 30:70 to prepare a solution having a concentration of 1 mol dm -3 . Further, 2% by mass of 1,3-propene sultone was added to the above solution to obtain an electrolyte solution.

[0081] [Preparation of Cell 12] A laminated power generation element 12a was produced by alternately laminating a plurality of the above positive electrode plates and a plurality of the above negative electrode plates one by one through a microporous polyolefin membrane serving as a separator.

[0082] The power generation element 12a was covered with two laminated films 12d and 12e so that the open ends of the positive electrode terminal 12b and the negative electrode terminal 12c respectively connected to the positive electrode plate and the negative electrode plate in advance were exposed to the outside, and sealed except for the portion serving as the liquid injection hole. After injecting the electrolyte solution, the liquid injection hole was hermetically sealed. The cell 12 was produced as described above.

[0083] The configuration of the cell 12 is not limited to the above case. Lithium may be attached to the negative electrode plate.

[0084] Hereinafter, specifically, a method for estimating the degree of abnormality of the cell 12 will be described. FIG. 9 is a flowchart showing the procedure of the estimation process of the degree of abnormality of the cell 12 by the control unit 21. The control unit 21 derives history information (S1). The control unit 21 stores the current obtained from the current sensor 7 at the estimation time in the history DB 224. The control unit 21 stores the voltage obtained from the voltage sensor 6 at the estimation time in the history DB 224. The control unit 21 stores the temperature obtained from the temperature sensor 8 at the estimation time in the history DB 224. The control unit 21 stores the SOC derived at the estimation time in the history DB 224. The control unit 21 stores the pressure obtained from the pressure sensor 10 at the estimation time in the history DB 224. The control unit 21 stores the thickness obtained from the thickness sensor 9 at the estimation time in the history DB 224. The control unit 21 stores the image data obtained by the camera 20 at the estimation time in the history DB 224. The control unit 21 stores the displacement amount from the initial state, obtained by processing the image data with the image processing program stored in the storage unit 22, in the history DB 224.

[0085] The control unit 21 reads out the estimation information required for estimating the degree of abnormality from the history DB 224 (S2). The control unit 21 reads out the relation DB 225 (S3).

[0086] The control unit 21 estimates the degree of abnormality (S4) and determines whether there is a sign (S5). When the rule base of FIG. 6 is stored in the relation DB 225, the control unit 21 estimates the degree of abnormality based on whether the pressure, thickness, and displacement amount read out from the history DB 224 are each less than the threshold value. When the degree of abnormality is "3", the control unit 21 determines that there is a sign. When the relation DB 225 stores the first relation between the normal state time and the cell thickness, the control unit 21 estimates the state of the cell 12 based on whether the second relation between the time and the change in thickness deviates from the first relation (S4), and determines the presence or absence of a sign based on whether the thickness exceeds the sign threshold value, etc. (S5). The control unit 21 stores the degree of abnormality or the presence or absence of a sign in the history DB 224. When the control unit 21 determines that there is a sign (S5: YES), it notifies that there is a sign (S6). The control unit 21 transmits information indicating that there is a sign of abnormality to the server 40 or to the user's terminal device through the communication unit 24. When there is no sign (S5: NO), the control unit 21 ends the process. After estimating the presence or absence of an abnormality omen for the entire battery module 1, the control unit 21 may identify the cell 12 with the omen.

[0087] According to the present embodiment, by deriving estimation information including changes in the shape and / or pressure of the cell 12, it means that changes in the shape and / or pressure of the negative electrode have been obtained. Based on the estimation information, the state of the cell 12 can be accurately estimated, and an omen of an abnormality such as a short circuit can be accurately detected.

[0088] FIG. 10 is a flowchart showing the procedure of the energization control process of the cell 12 by the control unit 21. The control unit 21 determines whether there is an omen of an abnormality in the target cell 12 (S11). The control unit 21 determines whether the degree of abnormality is "3". If there is no omen (S11: NO), the control unit 21 ends the process.

[0089] If there is an omen (S11: YES), the control unit 21 determines whether the SOC at the time of estimating the cell 12 with the omen is equal to or higher than the threshold value a (S12). If the SOC is not equal to or higher than the threshold value a (S12: NO), the control unit 21 ends the process. As will be described later, there may be a case where the cell 12 whose energization has been stopped during charging is restored and discharged, and it is necessary for the SOC to be equal to or higher than the threshold value a at the time of stopping.

[0090] If the SOC is equal to or higher than the threshold value a (S12: YES), the control unit 21 identifies the cell 12 to stop energization, and turns off the corresponding first switch 14 of this cell 12 (S13). The control unit 21 turns on the second switch 16 (S14) and ends the process. The second circuit 15 becomes conductive, and the cell 12 with the omen is in a state of being disconnected from the other battery circuits 11 and cannot be charged.

[0091] FIG. 11 is a schematic circuit diagram showing the battery module 1 when charging is performed by stopping the energization of the second cell 12. In FIG. 11, the current flowing during charging is indicated by a solid arrow. Assume that there is a sign of abnormality in the second cell 12 from the top in FIG. 11. In the battery circuit 11 including this cell 12, the first switch 14 is turned off, and the cell 12 is in a state of being disconnected from other battery circuits 11. The second switch 16 is turned on, and the second circuit 15 is in a conductive state. In the battery circuit 11 including the normal cell 12, the first switch 14 is on, and the cell 12 is connected to other battery circuits 11 via the first circuit 13. The second switch 16 is off, and the second circuit 15 is in a non-conductive state.

[0092] In the battery circuit 11 including the normal cell 12, current flows through the cell 12 and the first circuit 13, and the cell 12 performs charging. In the battery circuit 11 including the cell 12 with a sign, current does not flow through the cell 12 and the first circuit 13, but current flows through the second circuit 15. That is, no current flows through the cell 12 with a sign, and the second circuit 15 serves as a bypass and current flows through the second circuit 15. As a whole of the battery module 1, current flows, and the normal cell 12 performs charging. Since the cell 12 with a sign cannot be charged, further growth of dendrites and occurrence of a short circuit are prevented.

[0093] When discharging the cell 12 with a sign, the second switch 16 is turned off and the first switch 14 is turned on. Hereinafter, the case of discharging by returning the cell 12 whose energization has been stopped will be described. FIG. 12 is a flowchart showing the procedure of the discharge control process of the cell 12 by the control unit 21. The control unit 21 determines whether to return (S21). The control unit 21 determines whether it is difficult to operate only with the cells 12 in use, etc. If the control unit 21 does not return (S21: NO), the process ends.

[0094] When returning (S21: YES), the control unit 21 reads the history DB 224 and derives the resistance of the cell 12 that has stopped energization (S22). The control unit 21 reads the initial current and voltage of the charging times of the target cell 12 stored in the history DB 224 and derives the resistance.

[0095] The control unit 21 selects a cell 12 that performs discharge (S23). The control unit 21 selects a cell 12 with a large resistance among the cells 12 for which the resistance has been derived. As described above, when the resistance of the cell 12 is large, the calorific value is large and a short circuit is less likely to occur. The control unit 21 may select a cell 12 with a high SOC at the time of stopping energization. When the SOC is high, sufficient discharge can be performed.

[0096] The control unit 21 determines whether the load can be disconnected (S24). When the control unit 21 cannot disconnect (S24: NO), the process ends. When the control unit 21 can disconnect (S24: YES), the control unit 21 disconnects the load (S25). The control unit 21 turns off the corresponding second switch 16 of the cell 12 (S26). The control unit 21 turns on the first switch 14 (S27). The second circuit 15 is in a non-conductive state, the first circuit 13 is in a conductive state, the cell 12 is in a state connected to another battery circuit 11, and discharge becomes possible.

[0097] The control unit 21 connects the load to the battery module 1 (S28). The control unit 21 starts discharging (S29) and ends the process.

[0098] According to the present embodiment, when it becomes difficult to operate only with the cell 12 in use, the operation can be executed by returning and discharging the cell 12 during which energization has stopped.

[0099] (Embodiment 2) Embodiment 2 will be described by taking the HAPS aircraft 50 as an example of the aircraft. The aircraft may be an eVTOL (electric vertical takeoff and landing aircraft), but is not limited thereto. The aircraft includes a power generation device and a power storage element, and preferably does not have an internal combustion engine. FIG. 13 is a perspective view of the appearance of the HAPS aircraft 50, and FIG. 14 is a block diagram showing the configuration of the HAPS aircraft 50. In FIG. 13, the same parts as those in FIG. 4 are denoted by the same reference numerals and detailed descriptions thereof are omitted. In FIG. 14, the solar panel 54 is omitted. The HAPS aircraft 50 includes a wing portion 51, a plurality of propellers 52, a plurality of leg portions 53, a plurality of solar panels 54, a battery module 1, a control device 2, a motor 4, a wireless relay station 5, and wheels 55. The propeller 52 is connected to the motor 4. The configuration of the HAPS aircraft 50 is not limited to this example. The battery module 1, the control device 2, and the wireless relay station 5 are housed in the leg portion 53. Alternatively, these may be provided in the wing portion 51.

[0100] The HAPS aircraft 50 equipped with the wireless relay station 5 can simultaneously connect with a large number of terminal devices in a wide area, and by cooperating between the HAPS aircraft 50, artificial satellites, and ground stations, a high-speed communication infrastructure can be constructed. Even in the event of a disaster, a stable communication environment can be maintained.

[0101] The solar panel 54 is formed by arranging and connecting a plurality of modules each having a plurality of silicon-based solar cells, for example. The battery module 1 is formed by connecting a plurality of cells 12 in series and / or in parallel, for example. A plurality of battery modules 1 may be connected in series to form a bank, or the banks may be connected in parallel. The cell 12 and the battery module 1 have the same configuration as the cell 12 and the battery module 1 according to Embodiment 1.

[0102] The control device 2 has the same configuration as the control device 2 in the first embodiment, and further has a motor drive unit 28. In the storage unit 22, an abnormality degree estimation program 221, a power supply control program 222, a discharge control program 223, a history DB 224, and a relationship DB 225 are stored.

[0103] FIG. 15 is an explanatory diagram showing an example of the record layout of the history DB 224. The history DB 224 in the second embodiment stores a solar panel power generation amount column and a consumed energy column in addition to the columns of the history DB 224 in the first embodiment. The solar panel power generation amount column stores the power generation amount of the solar panel 54. The consumed energy column stores the consumed energy amount of the entire HAPS aircraft 50.

[0104] The input unit 23 receives the detection results of the current and voltage of the solar panel 54 and the battery module 1. The communication unit 24 has a function of communicating with other devices such as the wireless relay station 5, and transmits and receives required information. The motor drive unit 28 controls the rotational drive of each motor 4 of each propeller 52.

[0105] An inverter circuit and a switching unit (not shown) are connected to the load 3. The battery module 1 and the solar panel 54 are connected to the switching unit. The inverter circuit converts the DC current input by switching between the battery module 1 and the solar panel 54 by the switching unit into an AC current and outputs it to the load 3. In FIG. 14, a state where the battery module 1 is connected to the load 3 is shown.

[0106] The wireless relay station 5 includes a communication unit 56. The communication unit 56 has an antenna, a transceiver, an amplifier, etc., and transmits and receives wireless signals with relay stations on the ground or at sea. Through the relay station, the wireless relay station 5 is connected to the network NW of the mobile communication network. A server 40 and a terminal device 60 are connected to the network NW. The motor 4 rotationally drives the propeller 52. Alternatively, the motor 4 may drive an aircraft propulsion device or an aircraft ascent device other than the form shown in FIG. 13.

[0107] The HAPS aircraft 50 configured as described above rises by lift while turning within a predetermined horizontal region after leaving the ground obliquely upward, and ascends to the airspace A. Examples of the airspace A include airspaces within the stratosphere at an altitude of 11 km to 50 km. Among them, an airspace at an altitude of 20 km is preferable. After ascending to the airspace A, the HAPS aircraft 50 horizontally moves to the horizontal position B and stays at the position B.

[0108] At night, since power cannot be generated by the solar panel 54, the battery module 1 supplies power. The battery module 1 supplies power for driving the motor 4 to fly, and also supplies power to the control unit 21, the input unit 23, the communication unit 24, the wireless relay station 5, etc., which are required even when the HAPS aircraft 50 is gliding within the airspace A. Since power is supplied by the battery module 1 until power is generated by the solar panel 54, the depth of discharge at night increases. For example, the battery module 1 performs charge and discharge within the range of SOC 10% to 100%.

[0109] In the present embodiment, similar to the first embodiment, based on the pressure, thickness, and displacement amount of the cell 12, the degree of abnormality of the cell 12 is estimated using the rule base stored in the relationship DB 225. The degree of abnormality may be estimated based on any one of the pressure, thickness, and displacement amount, or may be estimated based on at least one of the current, voltage, temperature, solar panel power generation amount, and energy consumption in addition to the pressure, thickness, and displacement amount.

[0110] When it is determined that there is a sign of abnormality based on the degree of abnormality of cell 12, the first switch 14 of that cell 12 is turned off, and the second switch 16 is turned on to stop the energization during charging. This prevents a short circuit in the cell 12. The HAPS aircraft 50 is required to simultaneously connect with a large number of terminal devices over a wide area for a predetermined period, such as for half a year, to construct a high-speed communication infrastructure. According to this embodiment, the life can be extended, and stable discharge can be performed at night over a longer period, enabling stable flight operation and maintaining a stable communication environment.

[0111] When the control unit 21 determines that it is difficult to continue flying with only the cells 12 in use, among the cells 12 where the energization during charging has been stopped, it selects a cell 12 with a high resistance and a high SOC, turns off the second switch 16 of the cell 12, and turns on the first switch 14 to resume the energization during discharge. This can avoid a crash and land the HAPS aircraft 50.

[0112] (Embodiment 3) FIG. 16 is a block diagram showing the configuration of the charge / discharge system 30 and the server 40 according to Embodiment 3. The server 40 of Embodiment 3 includes a storage unit 43. The storage unit 43 includes a storage device such as a hard disk drive. In the storage unit 43, various computer programs executed by the control unit 41, various data used by the computer programs, data acquired from the outside, etc. are stored. An example of the computer program stored in the storage unit 43 is a model generation program for generating the learning model 430. Further, the storage unit 43 may store training data including image data of the cell 12 and label data indicating the degree of abnormality. These data may be acquired from the control device 2 via the communication unit 42. The history DB 224 of the control device 2 of Embodiment 3 does not store the displacement amount based on the image data. Since the degree of abnormality is estimated by inputting the image data into the learning model 430, it is not necessary to perform image processing to derive the displacement amount.

[0113] FIG. 17 is a schematic diagram showing the configuration of the learning model 430 in Embodiment 3. The learning model 430 in Embodiment 3 is a learning model based on CNN (Convolutional Neural Networks), R-CNN (Region-based CNN), etc., and includes an input layer 431, an intermediate layer 432, and an output layer 433. The learning model 430 is trained to output the degree of abnormality for the input of the image data of the cell 12. The learning model 430 is generated by, for example, the server 40 and stored in the storage unit 22 of the control device 2.

[0114] Image data is input to the input layer 431 of the learning model 430. The intermediate layer 432 is composed of, for example, a convolutional layer 432a, a pooling layer 432b, and a fully connected layer 432c. A plurality of convolutional layers 432a and pooling layers 432b may be provided alternately. The convolutional layer 432a and the pooling layer 432b extract the features of the image data input through the input layer 431 by operations using the nodes of each layer. The fully connected layer 432c combines the data from which the feature portions have been extracted by the convolutional layer 432a and the pooling layer 432b into one node and outputs a feature variable converted by an activation function. The feature variable is output to the output layer 433 through the fully connected layer 432c.

[0115] The output layer 433 includes one or more nodes. The output layer 433 converts the feature variable input from the fully connected layer 432c of the intermediate layer 432 into a probability using the softmax function, and outputs, from each node, the probability indicating each degree of abnormality from 0 to 3, for example.

[0116] For example, the output layer 433 may be composed of four nodes from the first node to the fourth node, and the probability that the degree of abnormality is 0 from the first node, the probability that the degree of abnormality is 1 from the second node, the probability that the degree of abnormality is 2 from the third node, and the probability that the degree of abnormality is 3 from the fourth node may be output. The output layer 433 For example, degree of abnormality 0... 0.04 Degree of abnormality 1... 0.90 Degree of abnormality 2…0.05 Degree of abnormality 3…0.01 Output as follows. The number of nodes constituting the output layer 433 and the calculation results assigned to each node are not limited to the above example, and can be designed as appropriate. The output layer 433 may include one node and output the probability of a sign. In this case, the training data includes the image data of the cell 12 and the label data indicating the presence or absence of a sign.

[0117] The control unit 21 of the control device 2 can estimate the degree of abnormality by referring to the calculation results obtained from the learning model 430, for example, by selecting the node with the highest probability.

[0118] The internal parameters (weights and biases between nodes) that determine the configuration of the learning model 430 are learned, for example, in the server 40 by using an appropriate learning algorithm.

[0119] FIG. 18 is a flowchart showing the procedure of the generation process of the learning model 430 by the control unit 41. As a preparation stage for generating the learning model 430, the control unit 41 collects the image data of the taper portion of the cell 12 and the label data indicating the degree of abnormality of the cell 12, and stores the collected data in the storage unit 43 as training data (S31). In this preparation stage, by collecting a sufficient number of image data and label data, the estimation accuracy of the degree of abnormality can be improved. As learning progresses, the estimation result by the learning model 430 and the image data used for the estimation process may be acquired and used as training data.

[0120] The control unit 41 generates a learning model 430 that outputs the probability of the degree of abnormality when image data is input using the training data (S32). Specifically, the control unit 41 inputs the training data to the input layer 431, obtains the probability of the degree of abnormality from the output layer 433 through the calculation process in the intermediate layer 432. The control unit 41 compares the estimation results of the degrees of abnormality output from the output layer 433 with the information on the degrees of abnormality labeled for the image data in the training data, that is, the correct values, and optimizes the parameters used in the arithmetic processing in the intermediate layer 432 so that the output values from the output layer 433 approach the correct values. The parameters are, for example, weights (coupling coefficients), coefficients of activation functions, etc. The method for optimizing the parameters is not particularly limited. For example, the control unit 41 optimizes various parameters using the error backpropagation method. The control unit 41 performs the above processing on the image data of each training data to generate a learning model 430. The control unit 41 stores the generated learning model 430 in the storage unit 43 and ends a series of processing. Not only image data but also pressure and thickness may be input and learned in the input layer 431. Further, current, voltage, temperature, SOC, etc. may be input. When the charge / discharge system is provided in the HAPS aircraft 50, the solar panel power generation amount and the consumed energy may be input.

[0121] The control device 2 downloads the learning model 430 generated in the server 40. The control device 2 can estimate the degree of abnormality in the cell 12 by inputting the image data acquired at the time of estimation to the learning model 430.

[0122] FIG. 19 is a flowchart showing the procedure of the estimation process of the degree of abnormality of the cell 12 by the control unit 21. The control unit 21 derives history information (S41). The control unit 21 reads out estimation information from the history DB 224 (S42). Here, image data is read out as the estimation information.

[0123] The control unit 21 inputs the image data as the estimation information to the learning model 430 (S43). The control unit 21 estimates the degree of abnormality based on the probability of the degree of abnormality output by the learning model 430 (S44). The control unit 21 acquires the degree of abnormality with the highest probability and estimates a sign. The control unit 21 determines whether there is a sign (S45). When the degree of abnormality is "3", the control unit 21 determines that there is a sign. When the control unit 21 determines that there is a sign (S45: YES), it notifies that there is a sign (S46). The control unit 21 transmits information indicating that there is a sign of abnormality to the server 40 or to the user's terminal device through the communication unit 24. When the learning model 430 outputs the probability of there being a sign, the control unit 21 determines that there is a sign when the probability of there being a sign output by the learning model 430 is, for example, 50% or more. When the control unit 21 determines that there is no sign (S45: NO), it ends the process.

[0124] According to this embodiment, the state of the cell 12 can be easily and accurately estimated, and the sign of abnormality of the cell 12 can be determined. In Embodiment 3, an example of supervised learning using a CNN was shown, but it is also possible to estimate the state of the cell 12 using unsupervised learning or regression, etc.

[0125] The above embodiments are not restrictive. The scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the claims. The power storage element is not limited to a lithium secondary battery. The power storage element may be another secondary battery or a capacitor.

Explanation of Signs

[0126] 1 Battery module (power storage element) 12 Cells (power storage elements) 12a Power generation element 12b Positive electrode terminal 12c Negative electrode terminal 12f Exterior body 14 First switch 16 Second switch 2 Control device 25, 26, 27 Recording medium 21, 41 Control unit 22, 43 Storage unit 221 Abnormality degree estimation program 222 Energization control program 223 Discharge control program 224 History DB 23 Input section 24, 42 Communication section 28 Motor drive section 3 Load 4 Motor 5 Wireless relay station 30 Charge / discharge system 40 Server 50 HAPS aircraft 51 Wing section 52 Propeller 53 Leg section 54 Solar panel 55 Wheel

Claims

1. A first deriving unit that derives estimation information including the thickness or the rate of change of the thickness of a power storage element over time, the power storage element having a negative electrode on which Li (lithium) is deposited during charging and releases the Li into an electrolytic solution during discharging, and an exterior body; An estimating unit that estimates the state of the power storage element including the presence or absence of a sign of abnormality of the power storage element based on the derived estimation information; A determination unit that determines the presence or absence of a sign of abnormality of the power storage element based on the state of the power storage element estimated by the estimating unit; A power supply control unit that stops energization at least during charging of the power storage element identified based on the state estimated by the estimating unit; A discharge control unit that discharges the power storage element whose energization has been stopped by the power supply control unit; A second deriving unit that derives the resistance of a plurality of power storage elements whose energization has been stopped by the power supply control unit; The discharge control unit discharges a power storage element selected based on the resistance derived by the second deriving unit, an estimation device.

2. A first deriving unit that derives estimation information including the thickness or the rate of change of the thickness of a power storage element over time, the power storage element having a negative electrode on which Li (lithium) is deposited during charging and releases the Li into an electrolytic solution during discharging, and an exterior body; An estimating unit that estimates the state of the power storage element including the presence or absence of a sign of abnormality of the power storage element based on the derived estimation information; A determination unit that determines the presence or absence of a sign of abnormality of the power storage element based on the state of the power storage element estimated by the estimating unit; A power supply control unit that stops energization at least during charging of the power storage element identified based on the sign of abnormality determined by the determination unit; A discharge control unit that discharges the power storage element whose energization has been stopped by the power supply control unit; A second deriving unit that derives the resistance of a plurality of power storage elements whose energization has been stopped by the power supply control unit; The discharge control unit discharges a power storage element selected based on the resistance derived by the second deriving unit, an estimation device.

3. The estimation information is information on a change in the thickness of the power storage element caused by a SEI (Solid Electrolyte Interphase) film including dead Li not involved in the reaction and / or a deposit on the negative electrode including Li dendrites, the estimation device according to claim 1 or 2.

4. The negative electrode has an active material containing Li metal, the estimation device according to any one of claims 1 to 3.

5. The estimating unit is When the estimated information is input, the estimated information derived by the first derivation unit is input to a learning model that outputs information related to the state of the power storage element, and the state of the power storage element is estimated. The estimation device according to any one of claims 1 to 4.

6. The estimation unit estimates the state of the power storage element based on whether or not a second relationship between a change in the thickness of the power storage element corresponding to the estimated information and time deviates from a first relationship between the thickness of the normal power storage element and time. The estimation device according to any one of claims 1 to 4.

7. A first derivation unit that derives estimated information including the thickness of a power storage element having a negative electrode in which Li is deposited during charging and the Li is released into an electrolytic solution during discharging and an exterior body; A determination unit that inputs the estimated information derived by the first derivation unit to a learning model that outputs information related to a sign of abnormality of the power storage element, and determines whether or not there is a sign of abnormality of the power storage element; A power supply control unit that stops energization at least during charging for the power storage element specified based on the sign of abnormality determined by the determination unit; A discharge control unit that discharges the power storage element whose energization has been stopped by the power supply control unit; A second derivation unit that derives the resistance of a plurality of power storage elements whose energization has been stopped by the power supply control unit; The discharge control unit discharges the power storage element selected based on the resistance derived by the second derivation unit. The estimation device.

8. Derive estimated information including a change in the thickness or the rate of change of the thickness of a power storage element having a negative electrode in which Li is deposited during charging and the Li is released into an electrolytic solution during discharging and an exterior body, Based on the derived estimated information, estimate the state of the power storage element including whether or not there is a sign of abnormality of the power storage element, Based on the estimated state of the power storage element, determine whether or not there is a sign of abnormality of the power storage element, For the power storage element specified based on the estimated state, stop energization at least during charging, Derive the resistance of a plurality of power storage elements whose energization has been stopped, An estimation method of discharging the power storage element whose energization has been stopped, selected based on the derived resistance.

9. Derive estimated information including a change in the thickness or the rate of change of the thickness of a power storage element having a negative electrode in which Li is deposited during charging and the Li is released into an electrolytic solution during discharging and an exterior body, Based on the derived estimated information, estimate the state of the power storage element including whether or not there is a sign of abnormality of the power storage element, Based on the estimated state of the energy storage element, determine the presence or absence of signs of abnormality in the energy storage element. For the energy storage element identified based on the determined sign of abnormality, stop energization at least during charging. Derive the resistances of a plurality of energy storage elements for which energization has been stopped. An estimation method of discharging the energy storage element for which energization has been stopped and which is selected based on the derived resistance.

10. Derive estimation information including a change in the thickness or the rate of change of the thickness over time of an energy storage element having a negative electrode in which Li is deposited during charging and releases the Li into the electrolytic solution during discharging, and an exterior body. Based on the derived estimation information, estimate the state of the energy storage element including the presence or absence of signs of abnormality in the energy storage element. Based on the estimated state of the energy storage element, determine the presence or absence of signs of abnormality in the energy storage element. For the energy storage element identified based on the estimated state, stop energization at least during charging. Derive the resistances of a plurality of energy storage elements for which energization has been stopped. Discharge the energy storage element for which energization has been stopped and which is selected based on the derived resistance. A computer program for causing a computer to execute the process.

11. Derive estimation information including a change in the thickness or the rate of change of the thickness over time of an energy storage element having a negative electrode in which Li is deposited during charging and releases the Li into the electrolytic solution during discharging, and an exterior body. Based on the derived estimation information, estimate the state of the energy storage element including the presence or absence of signs of abnormality in the energy storage element. Based on the estimated state of the energy storage element, determine the presence or absence of signs of abnormality in the energy storage element. For the energy storage element identified based on the determined sign of abnormality, stop energization at least during charging. Derive the resistances of a plurality of energy storage elements for which energization has been stopped. Discharge the energy storage element for which energization has been stopped and which is selected based on the derived resistance. A computer program for causing a computer to execute the process.

Images