JP2022041144A - Cut out gear and power storage element - Google Patents

Abstract

To provide a cut out gear and a power storage element capable of detecting an internal short circuit at an early stage and interrupting the current path according to the detection result.SOLUTION: A power storage element 100 having an electrode terminal 310 and an electrode body having a conductive tab 211, with the electrode body connected to the electrode terminal via the conductive tab, has a cut out part (semiconductor switching element 152) that interrupts the current path between the electrode terminal and the electrode body based on a sensor output from a temperature sensor that measures the temperature of the conductive tab.SELECTED DRAWING: Figure 16

Description

The present invention relates to a shutoff device and a power storage element.

In recent years, power storage elements such as lithium-ion batteries have been used in a wide range of fields such as power supplies for mobile terminals such as notebook personal computers and smartphones, renewable energy power storage systems, and power supplies for IoT devices.

For example, a porous separator that is filled with an electrolytic solution and allows ions to move is sandwiched between the positive electrode and the negative electrode of a lithium ion battery. The separator prevents the positive electrode and the negative electrode from coming into contact with each other, and prevents a short circuit (internal short circuit) from occurring between the positive electrode and the negative electrode (see, for example, Patent Document 1). Not limited to lithium-ion batteries, when an internal short circuit occurs in a power storage element, heat is generated inside the battery, which may cause the battery to fail.

Japanese Unexamined Patent Publication No. 2019-140100

Since heat is generated inside the battery due to the internal short circuit, it is possible to detect the internal short circuit by, for example, measuring the temperature of the battery surface and detecting the temperature rise of the battery surface. However, since it takes a certain amount of time for the heat generated by the internal short circuit to be transferred to the battery surface, it is difficult to detect the internal short circuit in real time by this method.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a breaking device and a power storage element capable of detecting an internal short circuit at an early stage and cutting off a current path according to a detection result.

The blocking device includes an electrode terminal and an electrode body having a conductive tab, and measures the temperature of the conductive tab with respect to a power storage element in which the electrode body is connected to the electrode terminal via the conductive tab. A blocking unit for blocking the current path between the electrode terminal and the electrode body is provided based on the sensor output from the temperature sensor.

The power storage element is a power storage element including an electrode terminal and an electrode body having a conductive tab, and the electrode body is connected to the electrode terminal via the conductive tab, and the temperature of the conductive tab. Equipped with a temperature sensor to measure.

According to the present application, an internal short circuit can be detected at an early stage, and the current path can be cut off according to the detection result.

It is an external perspective view of a power storage element. It is an exploded perspective view of a power storage element. It is an exploded perspective view of the electrode body which constitutes a power storage element. It is a partial cross-sectional view near a terminal. It is a block diagram explaining the internal structure of a detection device. It is a circuit diagram which shows the equivalent circuit of a power storage element. It is a circuit diagram which shows the equivalent circuit of the power storage element in the state where an internal short circuit occurs. It is a circuit diagram which shows the equivalent circuit of the power storage element after synthesis. It is a schematic diagram which shows the structural example of the thermal circuit model in Embodiment 1. It is a flowchart explaining the detection procedure of an internal short circuit in Embodiment 1. FIG. It is a schematic diagram which shows the structural example of the thermal circuit model in Embodiment 2. It is a flowchart explaining the detection procedure of an internal short circuit in Embodiment 3. It is a flowchart explaining the detection procedure of an internal short circuit in Embodiment 4. It is a flowchart explaining the detection procedure of an internal short circuit in Embodiment 5. It is a flowchart explaining the procedure of detecting a sign of an internal short circuit. It is a partial cross-sectional view of the power storage element in Embodiment 7. It is a perspective view which shows the mounting example of a circuit breaker. It is a flowchart explaining the procedure of the process which a control circuit executes. It is an external perspective view which shows the laminated type power storage element. It is an exploded perspective view which shows the laminated type power storage element.

The blocking device includes an electrode terminal and an electrode body having a conductive tab, and measures the temperature of the conductive tab with respect to a power storage element in which the electrode body is connected to the electrode terminal via the conductive tab. A blocking unit for blocking the current path between the electrode terminal and the electrode body is provided based on the sensor output from the temperature sensor.
When an internal short circuit occurs in the power storage element, the temperature of the conductive tab rises more rapidly than that of the electrode body or the container for accommodating the electrode body. When the temperature rise of the conductive tab is recognized, the cutoff device can prevent the power storage element from becoming hot by cutting off the current path between the electrode terminal and the electrode body.

The blocking device includes a detection unit that detects an internal short circuit in the electrode body based on the sensor output, and the blocking unit is located between the electrode terminal and the electrode body according to the detection result of the detection unit. The current path may be cut off. According to this configuration, the detection unit can detect the internal short circuit at an early stage by referring to the temperature of the conductive tab, and if the internal short circuit is detected, the current path between the electrode terminal and the electrode body can be cut off. ..

In the breaking device, the detection unit may include an observer that estimates the short-circuit resistance of the internal short circuit based on the sensor output. According to this configuration, the short-circuit resistance of the internal resistance that cannot be directly observed can be estimated through the state variables obtained from the observer.

In the cutoff device, the detection unit may estimate the short-circuit resistance of the internal resistance by using a state estimation algorithm based on the sensor output and a thermal circuit model simulating the thermal phenomenon of the power storage element. According to this configuration, the short-circuit resistance of the internal resistance that cannot be directly observed can be estimated by using the state estimation algorithm.

In the breaking device, the thermal circuit model may be a model in which the electrode body, the conductive tab, and the short-circuited portion are included in the nodes, and the temperature and heat capacity at each node and the thermal resistance between the nodes are included in the parameters. .. According to this configuration, a thermal phenomenon in the power storage element can be described using a simple model.

In the cutoff device, the state estimation algorithm obtains the time transition of each state variable using a state equation representing the time transition of the state variable including the temperature and short circuit resistance of each node, and observes the state variable and the temperature sensor. A procedure may be included in which the likelihood of state estimation is obtained using an observation equation that describes the relationship with the observed amount including temperature, and the estimated value of the state variable is updated according to the probability of the obtained state estimation. According to this configuration, the short-circuit resistance of the internal resistance that cannot be directly observed can be estimated in time series through the state variables that are updated sequentially.

In the blocking device, the state estimation algorithm may include a particle filter, an ensemble Kalman filter, an extended Kalman filter, or an unscented Kalman filter. According to this configuration, a particle filter, an ensemble Kalman filter, an extended Kalman filter, or an unscented Kalman filter can be used to sequentially update state variables and estimate the short-circuit resistance of internal resistance that cannot be directly observed in time series. ..

In the blocking device, the electrode body may be a laminated electrode body. According to this configuration, since the positive electrode plates (or the negative electrode plates) of the power storage elements are connected only via the conductive tabs, the temperature of the conductive tabs rises rapidly when an internal short circuit occurs. When the temperature rise of the conductive tab is recognized, the cutoff device can prevent the power storage element from becoming hot by cutting off the current path between the electrode terminal and the electrode body.

The power storage element is a power storage element including an electrode terminal and an electrode body having a conductive tab, and the electrode body is connected to the electrode terminal via the conductive tab, and the temperature of the conductive tab. Equipped with a temperature sensor to measure. Since the power storage element includes a temperature sensor that measures the temperature of the conductive tab, it is possible to observe a state of change relatively quickly when an internal short circuit occurs.

The power storage element may include a blocking portion that cuts off the current path between the electrode terminal and the electrode body based on the sensor output from the temperature sensor. According to this configuration, when an internal short circuit of the power storage element is detected, the current path between the electrode terminal and the electrode body is cut off, so that it is possible to prevent the power storage element from becoming hot.

Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments thereof.
(Embodiment 1)
1 is an external perspective view of the power storage element 100, FIG. 2 is an exploded perspective view of the power storage element 100, FIG. 3 is an exploded perspective view of an electrode body 200 constituting the power storage element 100, and FIG. 4 is a partial cross-sectional view near a terminal. .. The power storage element 100 is, for example, a lithium ion secondary battery. The power storage element 100 stores power supplied from an external charging device, and supplies the stored power to a predetermined load. The power storage element 100 is a power source for automobiles (or mobile objects) such as an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV), an aviation power source, a space power source, and a power source for electronic devices. , Used as a power source for power storage.

The power storage element 100 includes an electrode body 200 (see FIG. 2) housed in a container 110, and electrode terminals 310 and 320 connected to an external charging device and a load. One electrode terminal 310 is a positive electrode terminal, and the other electrode terminal 320 is a negative electrode terminal. The electrode body 200 is electrically connected to the electrode terminals 310 and 320 via conductive tabs (positive electrode tab 211 and negative electrode tab 221 described later).

The container 110 is composed of a rectangular parallelepiped container main body 111 and a lid 112 that closes the opening of the container main body 111. The container body 111 and the lid 112 are formed of a weldable metal such as stainless steel, aluminum, and an aluminum alloy. Alternatively, the container body 111 and the lid 112 may be made of resin. The container body 111 is sealed by the lid 112 after accommodating the electrode body 200 and the like. An electrolytic solution (not shown) is sealed inside the container 110. As the electrolyte, for example, an electrolyte in which a supporting salt is contained in an organic solvent is used. As the organic solvent, for example, aprotic solvents such as carbonates, esters and ethers are used. As the supporting salt, for example, lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ are preferably used. The electrolyte may contain, for example, various additives such as a gas generating agent, a film forming agent, a dispersant, and a thickener. The lid 112 may include an injection port for injecting an electrolytic solution into the container 110, a gas discharge valve for discharging gas inside the container when the internal pressure of the container 110 rises, and the like.

The electrode terminals 310 and 320 of the power storage element 100 are attached to the lid 112 of the container 110 by caulking or the like. Specifically, the electrode terminals 310 and 320 each have a shaft portion (rivet portion) extending downward, and these shaft portions are the upper gasket 120, the lid 112, the lower gasket 130, and the current collector 140. It is inserted into the through hole of the and crimped. As a result, the electrode terminals 310 and 320 are attached to the lid 112 of the container 110 together with the upper gasket 120, the lid 112, the lower gasket 130, and the current collector 140.

Here, the upper gasket 120 is a flat plate-shaped sealing member arranged between the lid 112 of the container 110 and the electrode terminals 310 and 320. The lower gasket 130 is a sealing member arranged between the lid 112 of the container 110 and the current collector 140. The upper gasket 120 and the lower gasket 130 are formed of an insulating resin material such as polypropylene (PP), polyethylene (PE), or polyphenylene sulfide resin (PPS).

The current collector 140 is a rectangular flat plate-shaped conductive member that electrically connects the electrode terminals 310 and 320 and the conductive tabs (positive electrode tab 211 and negative electrode tab 221) of the electrode body 200. The current collector 140 is formed of a material such as aluminum, an aluminum alloy, copper, or a metal such as a copper alloy. The current collector 140 on the positive electrode side is connected to the electrode terminal 310 by caulking or the like, and is also connected to the positive electrode tab 211 included in the electrode body 200 by welding or the like. Similarly, the current collector 140 on the negative electrode side is connected to the electrode terminal 320 by caulking or the like, and is also connected to the negative electrode tab 221 provided in the electrode body by welding or the like. Alternatively, the current collector 140 may be connected to the electrode terminals 310, 320 using techniques such as welding or screw fastening, and the positive electrode tab 211 and negative electrode tab 221 may be connected using techniques such as caulking and screw fastening. May be connected to.

The electrode body 200 is a laminated body of a positive electrode plate 210, a negative electrode plate 220, and a separator 230. The electrode body 200 shown as an example in FIG. 3 is shown to be composed of a laminated body in which a separator 230, a negative electrode plate 220, a separator 230, a positive electrode plate 210, and the like are repeatedly laminated in this order.

The positive electrode plate 210 is composed of a base material and a positive electrode active material layer formed on the base material. The base material of the positive electrode plate 210 is a current collector foil. The current collector foil is formed of a known material such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, and Al—Cd alloy. The positive electrode active material layer contains a positive electrode active material, a conductive auxiliary agent, and a binder. As the positive electrode active material, a substance capable of occluding and releasing lithium ions is used. As the positive electrode active material, polyanionic compounds such as LiMPO ₄ , LiMSiO ₄ , LiMBO ₃ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), LiMn ₂ O ₄ and LiMn. _1.5 Ni _0.5 O ₄ etc. spinnel type lithium manganese oxide, LiMO ₂ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co etc., lithium excess type composite oxide Includes) and other lithium transition metal oxides are used. As the conductive auxiliary agent, for example, carbon black such as acetylene black (AB) or other carbon material (graphite or the like) is preferably used. For the binder, for example, a material such as polyvinylidene fluoride (PVDF) is used.

The positive electrode plate 210 includes a positive electrode tab 211. The positive electrode tab 211 is a rectangular conductive tab protruding from one side of the positive electrode plate 210. The positive electrode tab 211 is integrally formed with the base material (current collector foil). The positive electrode tabs 211 of each positive electrode plate 210 are bundled together to form a tab bundle.

The negative electrode plate 220 is composed of a base material and a negative electrode active material layer formed on the base material. The base material of the negative electrode plate 220 is a current collector foil. For the current collector foil, the same material as the current collector foil constituting the base material of the positive electrode plate 210 is used. The negative electrode active material layer contains a negative electrode active material, a conductive auxiliary agent, and a binder. As the negative electrode active material, a substance capable of storing and releasing lithium ions is used. Negative electrode active materials include lithium metals, lithium alloys (lithium-metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys). Alloys that can store and release lithium, carbon materials (eg graphite, non-graphitizable carbon, easily graphitized carbon, low temperature fired carbon, amorphous carbon, etc.), silicon oxides, metal oxides, lithium metal oxides (Li) ₄ Ti ₅ O ₁₂ etc.), polyphosphate compounds, and compounds of transition metals such as Co ₃ O ₄ and Fe ₂ P, which are generally called conversion negative electrodes, and Group 14 to Group 16 elements. As the conductive auxiliary agent and the binder, the same material as the conductive auxiliary agent and the binder constituting the positive electrode active material layer is used.

The negative electrode plate 220 includes a negative electrode tab 221. The negative electrode tab 221 is a rectangular conductive tab that protrudes from one side of the negative electrode plate 220 at a position that does not overlap with the positive electrode tab 211. The negative electrode tab 221 is integrally formed with the base material (current collector foil). The negative electrode tabs 221 of each negative electrode plate 220 are bundled together to form a tab bundle.

The separator 230 is a rectangular sheet having microporous properties. As the material of the separator 230, for example, a woven fabric insoluble in an organic solvent, a non-woven fabric, a synthetic resin microporous film made of a polyolefin resin such as polyethylene, or the like is used. The separator 230 may be configured by laminating a plurality of microporous membranes having different materials, weight average molecular weights, pore ratios, etc., and various plasticizers, antioxidants, flame retardants, etc. may be laminated on these microporous membranes. It may be configured to contain an appropriate amount of an additive, or may be one in which an inorganic oxide such as silica is coated on one side or both sides of these microporous membranes.

In the first embodiment, a lithium ion secondary battery having a laminated electrode body 200 as the power storage element 100 has been described. Alternatively, the power storage element 100 may be a lithium ion secondary battery having a wound electrode body. Further, the power storage element 100 may be a cylindrical lithium ion battery or a laminated lithium ion battery. Further, the power storage element 100 may be an all-solid-state lithium-ion battery using a solid as an electrolyte, or a metallic lithium secondary battery using metallic lithium as a negative electrode. Further, the power storage element 100 may be a battery other than a lithium ion secondary battery such as a zinc air battery, a sodium ion battery or a lead battery, or a capacitor such as an electric double layer capacitor.

Not limited to the above-mentioned power storage element 100, the positive and negative electrode plates in the power storage element are provided apart from each other so as not to come into contact with each other. As a result, a short circuit (internal short circuit) between the positive and negative electrodes is avoided. In such a power storage element, if foreign matter is mixed in the container, or if the separator is damaged, the insulation between the positive and negative electrode plates cannot be maintained, and an internal short circuit may occur. When an internal short circuit occurs in the power storage element, heat is generated inside the battery, which leads to battery failure.

Since heat is generated inside the battery due to the internal short circuit, it is possible to detect the internal short circuit by, for example, measuring the temperature of the battery surface and detecting the temperature rise of the battery surface. However, since it takes a certain amount of time for the heat generated by the internal short circuit to be transferred to the battery surface, it is difficult to detect the internal short circuit in real time by this method. Moreover, it is difficult to actually measure the resistance of the internal short circuit, and there is no technique for grasping the resistance of the internal short circuit.

Therefore, in the first embodiment, in the detection device 10 described below, a simulation is executed with reference to the temperature of the conductive tab provided in the electrode body 200 of the power storage element 100, and the power storage element 100 is based on the execution result of the simulation. Detects an internal short circuit. For example, the detection device 10 estimates the short-circuit resistance of the internal short circuit by simulation, and if the estimated short-circuit resistance is less than the threshold value, it is determined that the internal short circuit in the power storage element 10 has been detected. Alternatively, the maximum temperature reached of the conductive tab is obtained in advance under various assumed usage conditions (current value during charging or discharging, energization time, etc.), and the tab temperature during actual operation is determined in advance. When the temperature becomes higher than the desired maximum temperature reached by a certain percentage or by a certain temperature or more, the detection device 10 may determine that an internal short circuit has been detected. Furthermore, the temperature of the conductive tab under various presumed usage conditions (current value during charging or discharging, energization time, etc.) is obtained by experiment or simulation, and the relationship between the usage conditions and the tab temperature is clarified in advance. If the tab temperature during actual operation is higher than the tab temperature under the applicable usage conditions by a certain percentage or by a certain temperature or more, the detection device 10 may determine that an internal short circuit has been detected. ..

Hereinafter, the configuration of the detection device 10 for executing the simulation will be described.
FIG. 5 is a block diagram illustrating an internal configuration of the detection device 10. The detection device 10 is a dedicated or general-purpose computer including a calculation unit 11, a storage unit 12, an input unit 13, and an output unit 14. In the example of FIG. 5, the detection device 10 is provided outside the power storage element 100. Specifically, the detection device 10 may be a power storage element monitoring device (BMU: Battery Management Unit) provided outside the power storage element 100, or may be a computer such as a server installed in a remote location. .. Alternatively, the detection device 10 may be built in the power storage element 100.

The arithmetic unit 11 is an arithmetic circuit including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU included in the arithmetic unit 11 executes various computer programs stored in the ROM and the storage unit 12, and controls the operation of each of the above-mentioned hardware units to make the entire device function as the detection device of the present application. Specifically, the calculation unit 11 uses the sensor output of the temperature sensor 250 for measuring the temperature of the conductive tabs (positive electrode tab 211, negative electrode tab 221) and the thermal circuit model MD1 for simulating the thermal phenomenon of the power storage element 100. The short-circuit resistance in the power storage element 100 is estimated by using the state estimation algorithm based on the above. The calculation unit 11 detects an internal short circuit of the power storage element 100 based on the estimation result of the short circuit resistance.

The arithmetic unit 11 is not limited to the above configuration, and may be any processing circuit or arithmetic circuit including a plurality of CPUs, a multi-core CPU, a GPU (Graphics Processing Unit), a microcomputer, a volatile or non-volatile memory, and the like. There may be. Further, the calculation unit 11 may have functions such as a timer for measuring the elapsed time from the instruction to give the measurement start instruction to the time when the measurement end instruction is given, a counter for counting the number, a clock for outputting date and time information, and the like.

The storage unit 12 is a storage device such as a flash memory. Various computer programs and data are stored in the storage unit 12. The computer program stored in the storage unit 12 includes, for example, a state estimation program PG for causing the calculation unit 11 to execute an operation based on the state estimation algorithm. The data stored in the storage unit 12 includes parameters used in the state estimation program PG, parameters used in the short-circuit equivalent circuit model and thermal circuit model MD1 described later, and data temporarily generated by calculation by the calculation unit 11. Etc. are included. The state estimation program PG is provided, for example, by a non-temporary recording medium M in which a computer program is readablely recorded. The recording medium M is a portable memory such as a CD-ROM, a USB memory, or an SD (Secure Digital) card. The arithmetic unit 11 reads a desired computer program from the recording medium M using a reading device (not shown in the figure), and stores the read computer program in the storage unit 12. Alternatively, the computer program may be provided by communication.

The input unit 13 includes an interface for connecting the temperature sensor 250, and acquires the sensor output from the temperature sensor 250. The temperature sensor 250 is an existing sensor such as a thermocouple or a thermistor. The temperature sensor 250 is connected to any one or more of the positive electrode tabs 211 and the negative electrode tabs 221 constituting the conductive tabs. Alternatively, the temperature sensor 250 may be connected to a current collector 140 to which a conductive tab is attached. In the first embodiment, the number of temperature sensors 250 is one. Alternatively, the number of temperature sensors 250 may be plural. The temperature sensor 250 may be connected to the input unit 13 by wire or may be connected to the input unit 13 wirelessly.

The output unit 14 includes an interface for connecting an external device. An example of an external device is a display device 20 such as a liquid crystal display. Alternatively, the external device may be a terminal device (not shown) such as a computer or smartphone used by the user. The calculation unit 11 outputs the detection result of the internal short circuit from the output unit 14 to the external device. In addition to the detection result of the internal short circuit, the calculation unit 11 may output the estimated value of the short circuit resistance from the output unit 14 to the external device.

The detection device 10 may include a notification unit such as an LED lamp or a buzzer in order to notify the user of the detection result of the internal short circuit.

Hereinafter, the content of the arithmetic processing executed by the detection device 10 will be described.
In the first embodiment, an equivalent circuit of the power storage element 100 is introduced in order to calculate the current at the time of an internal short circuit. FIG. 6 is a circuit diagram showing an equivalent circuit of the power storage element 100. In a general laminated liquid lithium-ion battery, each layer is electrically connected in parallel. Therefore, the equivalent circuit of the power storage element 100 is represented by, for example, a parallel circuit as shown in FIG. The equivalent circuit shown in FIG. 6 represents a five-layer laminated battery. The number of layers is appropriately set according to the number of the positive electrode plate 210 and the negative electrode plate included in the electrode body 200 of the power storage element 100.

Each layer of the power storage element 100 is divided into a positive electrode tab 211, a battery unit, and a negative electrode tab 221. The battery unit includes a positive electrode plate 210, a separator 230, a negative electrode plate 220, an electrolytic solution, and the like. In the equivalent circuit, the positive electrode tab 211 is represented as the positive electrode tab resistance (resistance value r _ptab ), and the negative electrode tab 221 is represented as the negative electrode tab resistance (resistance value r _ntab ). The battery unit is represented by an equilibrium potential (voltage value E _eq ) and an internal resistance (resistance value r _e ). Here, the internal resistance of the battery unit includes the ohmic resistance of the electrode, the reaction resistance of the electrode, and the ohmic resistance of the electrolyte.

In the equivalent circuit shown in FIG. 6, for simplification, each layer of the power storage element 100 is divided into three parts, a positive electrode tab 211, a battery part, and a negative electrode tab 221. However, it may be further divided. Further, in the equivalent circuit of FIG. 6, it is assumed that the external short-circuit layers are in the same state, but different states may be set for each external short-circuit layer.

FIG. 7 is a circuit diagram showing an equivalent circuit of the power storage element 100 in a state where an internal short circuit has occurred. The equivalent circuit shown as an example in FIG. 7 represents an equivalent circuit in which the fifth layer is an internal short-circuit layer and the first to fourth layers are external short-circuit layers. The internal short circuit is represented by a short circuit resistance (resistance value R _s ) connected in parallel to the battery unit. The same applies when an internal short circuit occurs in another layer.

Since each layer (1st to 4th layers) of the external short-circuit layer can be regarded as the same in the equivalent circuit, each element of the external short-circuit layer can be described by synthesizing them. FIG. 8 is a circuit diagram showing an equivalent circuit of the energy storage element 100 after synthesis. The synthetic positive electrode tab resistance (r _{ptab, ex} ), the synthetic internal resistance (r _{e, ex} ), and the synthetic negative electrode tab resistance (r _{ntab, ex} ) in the external short-circuit layer are described as in Equation 1.

Here, n represents the total number of layers. In this example, n = 5. Since each layer is parallel, the equilibrium potential is E _eq .

The current flowing through the external short-circuit layer is I _ex , the current flowing through the internal short-circuit layer is I _in , and the current flowing through the short-circuit portion is _Is . I _ex is the sum of the currents flowing through all the external short-circuit layers, and the current per layer is I _ex / (n-1). In the example of FIG. 8, the internal resistance of the battery in the internal short-circuit layer is expressed as r _{e, in in} order to distinguish it from the internal resistance (re _{, ex} ) of the battery in the external short-circuit layer.

In the equivalent circuit shown in FIG. 8, when the conservation law of current is applied, the equation 2 is obtained.

When Kirchhoff's law is applied in a closed circuit including an external short-circuit layer, a tab portion of the internal short-circuit layer, and a short-circuit portion, the number 3 is obtained.

When Kirchhoff's law is applied in a closed circuit consisting of an internal short-circuit layer and a short-circuit portion, the equation 4 is obtained.

When the equations 2 to 4 are solved, the current I _in flowing through the internal short-circuit layer, the current I _ex flowing through the external short-circuit layer, and the current Is _flowing through the short-circuit portion are obtained as equations 5 to 7, respectively.

In numbers 5 to 7, all resistances other than the short-circuit resistance R _s are known because they are determined by the design values (material characteristics, shape). On the other hand, the short-circuit resistance R _s cannot be determined by design and cannot be measured.

In the first embodiment, a thermal circuit model MD1 that simulates the thermal phenomenon of the power storage element 100 is introduced in order to calculate the temperature at the time of an internal short circuit. FIG. 9 is a schematic diagram showing a configuration example of the thermal circuit model MD1 according to the first embodiment. The thermal circuit model MD1 is a model for simulating the thermal phenomenon of the power storage element 100 by using the temperature of a plurality of regions that divide the power storage element 100 and the thermal resistance between the regions as parameters. In the thermal circuit model MD1 illustrated in FIG. 9, the power storage element 100 is divided into seven regions (regions 1 to 7). Regions 1 to 7 include an internal short-circuit layer, an external short-circuit layer, a positive electrode tab connected to the internal short-circuit layer, a positive electrode tab connected to the external short-circuit layer, a negative electrode tab connected to the internal short-circuit layer, a negative electrode tab connected to the external short-circuit layer, and a short-circuit portion. Corresponds to each. In the thermal circuit model MD1, the temperatures in the regions 1 to 7 are expressed as T ₁ to T ₇ , and the thermal resistance between the regions i and the region j is expressed as R _ij (i, j = 1 to 7). For example, temperature T ₁ represents the temperature of the internal short-circuit layer (battery temperature), temperature T ₂ represents the temperature of the external short-circuit layer (battery temperature), and thermal resistance R ₁₂ represents the thermal resistance between the internal short-circuit layer and the external short-circuit layer. .. The temperature in the other regions and the thermal resistance between the other regions are also as shown in FIG.

From the thermal circuit model MD1 shown in FIG. 9, the heat conduction equations of temperatures T ₁ to T ₇ are expressed as Equation 8.

Here, C _pi is the specific heat of the region i, V _i is the volume of the region i, and ρ _i is the density of the region i. _Q1 to _Q7 represent heat generation (Joule heat generation and electrochemical reaction heat) due to energization. In the heat conduction equation shown in Equation 8, for the sake of simplicity, it is assumed that there is no heat release to the outside of the battery and all the heat generated by the short-circuit current is used to raise the temperature of the battery. Alternatively, a heat conduction equation that considers heat release to the outside of the battery may be used.

Eq. 9 is obtained by rearranging the terms of Eq. 8 and rewriting the time derivative on the left side to the difference. In the number 9, Δt represents the time step width of the calculation, and the superscripts k and k + 1 represent the number of steps (time steps).

In the number 9, α _j = Δt / ρ _j C _pj V _j , and if arranged, the number 10 can be obtained.

In the equation 10, the calorific value Q ₁ ^k to Q ₇ ^k in each region is expressed as follows.

Here, the current I _in flowing through the internal short-circuit layer, the current I _ex flowing through the external short-circuit layer, and the current Is _flowing through the short-circuit portion are described as the numbers 5 to 7, respectively. In equations 5-7 and 11, the only unknown parameter is the short circuit resistance R _s . In order to clearly indicate that the calorific value Q ₁ ^k to Q ₇ ^k is a function of the short-circuit resistance R _s , if Q _i ^k = Q _i ^k (R _s ) is expressed, the number tens is rewritten as follows.

In order to estimate the short-circuit resistance R _s , the short-circuit resistance R _s is added as a state quantity (= latent variable) to the equation 12. The detection device 10 may have the arithmetic unit 11 function as an observer and solve the eight state variables shown in Equation 13 by eight equations.

In addition, a disturbance term may be added in order to estimate the state while suppressing the disturbance of the system or observation. The disturbance term is not essential, but it may be preferable to give it to improve the progress of the calculation. The equation with the disturbance term added is described as shown in Equation 14. In the number 14, v _T1 ^k to v _T7 ^k and v _Rsk ^are disturbance terms.

The number 14 is rewritten as the following equation.

Here, x _k is a vector having a state quantity as an element (state vector), and v _k is a vector having a disturbance quantity as an element (disturbance vector). f represents the non-linear difference equation shown in Equation 14.

In the first embodiment, it is assumed that the temperature sensor 250 is attached to the positive electrode tab 211. However, even if an internal short circuit occurs, it is not possible to know in which layer the internal short circuit occurred. Therefore, even if an internal short circuit occurs, it is not clear whether the measured value of the temperature sensor 250 represents the temperature of the positive electrode tab 211 connected to the internal short circuit layer or the temperature of the positive electrode tab 211 connected to the external short circuit layer. do not have. However, since the temperature rise of the tab of the external short-circuit layer is milder than the temperature rise of the tab of the internal short-circuit layer, it is safer to regard the measured value of the temperature sensor 250 as the temperature of the positive electrode tab 211 connected to the external short-circuit layer. A margin can be secured. In the following, it is assumed that the measured value of the temperature sensor 250 is the temperature of the positive electrode tab 211 connected to the external short-circuit layer.

The observation equation is expressed as the number 16.

Here, y _k is an observed value, c ^T is an observed vector, and w _k is an observed disturbance. Since the temperature T ₄ ^k of the positive electrode tab 211 connected to the external short-circuit layer is the fourth component of x _k , c ^T is expressed by the following equation. The T on the right shoulder of c represents transposition.

In the above-mentioned observation equation, it is assumed that there is only one observed value. Alternatively, there may be multiple observations.

The detection device 10 according to the first embodiment sequentially calculates the time update of the time series model represented by the state equation of the equation 15 and the observation equation of the equation 16 by using the particle filter, and obtains the internal resistance R _s . .. The detection device 10 detects an internal short circuit in the power storage element 100 based on the obtained internal resistance R _s .

The procedure for detecting an internal short circuit will be described below.
FIG. 10 is a flowchart illustrating a procedure for detecting an internal short circuit in the first embodiment. The calculation unit 11 of the detection device 10 gives an initial value of k = 1 (step S101). The calculation unit 11 may give the environmental temperature as the initial value of the temperature and give a temporary value preset as the initial value of the short-circuit resistance.

Next, the arithmetic unit 11 generates N particles for each state variable (step S102). Here, a number of about ¹⁰² to ¹⁰⁶ is usually used for N.

Next, the arithmetic unit 11 generates a random number corresponding to v _k for i = 1, 2, ..., N (step S103).

The calculation unit 11 updates the state of the particles to the state of the particles in the next time step by executing the calculation based on the number 18 for all N particles (step S104).

The calculation unit 11 acquires the sensor output of the temperature sensor 250 through the input unit 13 (step S105), and calculates the particle weight P _k ⁽ⁱ⁾ for all N particles based on the observation equation (step S106). .. The particle weight is the probability (likelihood) that the observed value y _k is observed when the state vector x _k of the particle i is obtained, and is described by the following equation.

The calculation unit 11 normalizes the particle weight P _k ⁽ⁱ⁾ calculated in step S106 based on the following equation (step S107).

The calculation unit 11 calculates a vector obtained by taking a weighted average of the weight of the particles and the state vector as an estimated value by the particle filter (step S108). The arithmetic expression is as shown in Equation 21. By this calculation, the estimated value of the temperature of each region and the estimated value of the short-circuit resistance can be obtained.

Next, the calculation unit 11 estimates the presence or absence of an internal short circuit in the power storage element 100 based on the estimated value of the short circuit resistance. For example, the arithmetic unit 11 determines whether or not the estimated value of the short-circuit resistance is less than the threshold value (step S109). The threshold is set arbitrarily.

When the estimated value of the short circuit resistance is not less than the threshold value (S109: NO), it is estimated that no internal short circuit has occurred in the power storage element 100. When it is estimated that no internal short circuit has occurred, the arithmetic unit 11 resamples (stratified sampling) the particles for the estimation of the next time step (step S110). The arithmetic unit 11 assumes that the state vector x _k ⁽ⁱ⁾ in the time step k is restored and extracted in proportion to p _k ⁽ⁱ⁾ , and may determine the state vector in the time step k + 1. After resampling the particles, the arithmetic unit 11 returns the process to step S102.

When the estimated value of the short circuit resistance is less than the threshold value (S109: YES), it is estimated that an internal short circuit has occurred in the power storage element 100. When it is estimated that an internal short circuit has occurred, the arithmetic unit 11 notifies the occurrence of the internal short circuit (step S111). For example, the arithmetic unit 11 generates character information indicating that an internal short circuit has occurred, outputs the character information to the display device 20 from the output unit 14, and causes the display device 20 to display the character information. Alternatively, the arithmetic unit 11 may notify the terminal device (not shown) of the character information indicating that an internal short circuit has occurred from the output unit 14. Further, the calculation unit 11 may urge the user to stop or replace the power storage element 100, or may ask the user to decide whether to stop or replace the power storage element 100.

As described above, the detection device 10 according to the first embodiment detects the internal short circuit of the power storage element 100 based on the sensor output of the temperature sensor 250 that measures the temperature of the conductive tab. When an internal short circuit occurs in the power storage element 100, the temperature of the conductive tab rises more rapidly than that of the container 110 or the electrode body 200. Therefore, the detection device 10 estimates the short circuit resistance based on the temperature of the conductive tab. Allows early detection of internal short circuits.

The mounting position of the temperature sensor 250 is not limited to the conductive tab as long as the temperature inside the battery can be accurately measured with almost no time lag. For example, the temperature sensor 250 may be attached to the electrode terminals 310, 320 (more preferably, the rivet portion of the electrode terminals 310, 320). Alternatively, the temperature sensor 250 may be attached to a current collector 140 or a bus bar (not shown). Alternatively, the temperature sensor 250 may be attached to the outer surface of the container 110 that houses the electrode body 200. When the electrode body 200 is in contact with the inner surface of the container 110 while being covered with the insulating bag, the temperature of the container 110 rises rapidly as the temperature of the electrode body 200 rises. Therefore, the internal short circuit can be detected at an early stage by estimating the short circuit resistance based on the temperature of the container 110. In particular, when the electrode body 200 is in contact with the long side surface inside the container 110 via the insulating bag, the temperature sensor 250 may be attached to the long side surface outside the container 110.

The detection device 10 in the first embodiment estimates the short-circuit resistance by using a particle filter. The particle filter is a filter method for a state-space model having non-linearity and non-Gaussian property, and can target a more general state-space model without assuming linearity or Gaussian property. Further, the particle filter has a relatively simple algorithm and can be easily mounted on the detection device 10.

(Embodiment 2)
In the second embodiment, a configuration is described in which a temperature sensor 250 is attached to a tab bundling portion in which a plurality of positive electrode tabs 211 (or a plurality of negative electrode tabs 221) are bundled, and an internal short circuit is detected based on the sensor output of the temperature sensor 250. do.

In the second embodiment, the temperature sensor 250 is attached to a tab bundling portion in which a plurality of positive electrode tabs 211 (or a plurality of negative electrode tabs 221) are bundled. In the second embodiment, it is assumed that the temperature of the tab of the internal short-circuit layer and the temperature of the tab of the external short-circuit layer are the same.

FIG. 11 is a schematic diagram showing a configuration example of the thermal circuit model MD2 according to the second embodiment. The thermal circuit model MD2 is a model for simulating the thermal phenomenon of the power storage element 100 by using the temperature of a plurality of regions that divide the power storage element 100 and the thermal resistance between the regions as parameters. In the thermal circuit model MD2 exemplified in FIG. 11, the power storage element 100 is divided into five regions (regions 1 to 5). Regions 1 to 5 correspond to an internal short-circuit layer, an external short-circuit layer, a positive electrode tab, a negative electrode tab, and a short-circuit portion, respectively. In the thermal circuit model MD2, the temperatures in the regions 1 to 5 are expressed as T ₁ to T ₅ , and the thermal resistance between the regions i and the region j is expressed as R _ij (i, j = 1 to 5). For example, temperature T ₁ represents the temperature of the internal short-circuit layer (battery temperature), temperature T ₂ represents the temperature of the external short-circuit layer (battery temperature), and thermal resistance R ₁₂ represents the thermal resistance between the internal short-circuit layer and the external short-circuit layer. .. The temperature in the other regions and the thermal resistance between the other regions are also as shown in FIG.

From the thermal circuit model MD2 shown in FIG. 11, the heat conduction equations of temperatures T ₁ to T ₅ are expressed as Equation 22.

Here, C _pi is the specific heat of the region i, V _i is the volume of the region i, and ρ _i is the density of the region i. _Q1 to Q5 represent heat generation ₍ Joule heat generation and electrochemical reaction heat) due to energization. In the heat conduction equation shown in Equation 22, for the sake of simplicity, it is assumed that there is no heat release to the outside of the battery and all the heat generated by the short-circuit current is used to raise the temperature of the battery. Alternatively, a heat conduction equation that considers heat release to the outside of the battery may be used.

The number 23 is obtained by rearranging the terms of the number 22 and rewriting the time derivative on the left side into the difference. In the number 23, Δt represents the time step width of the calculation, and the superscripts k and k + 1 represent the number of steps (time steps).

In the number 23, if α _j = Δt / ρ _j C _pj V _j is set and arranged, the number 24 can be obtained.

In the number 24, the calorific value Q ₁ ^k to Q ₅ ^k in each region is expressed as follows.

Here, the current I _in flowing through the internal short-circuit layer, the current I _ex flowing through the external short-circuit layer, and the current Is _flowing through the short-circuit portion are described as the numbers 5 to 7, respectively, as described in the first embodiment. Will be done. In equations 5-7 and 25, the only unknown parameter is the short circuit resistance R _s . In order to clearly indicate that the calorific value Q ₁ ^k to Q ₅ ^k is a function of the short-circuit resistance R _s , if Q _i ^k = Q _i ^k (R _s ), the equation 24 is rewritten as follows.

In order to estimate the short-circuit resistance R _s , the short-circuit resistance R _s is added as a state quantity (= latent variable) to the equation 26. The detection device 10 may have the arithmetic unit 11 function as an observer and solve the six state variables shown in Equation 27 by six equations.

In addition, a disturbance term may be added in order to suppress disturbances in the system and observations. The disturbance term is not essential, but it is preferable to give it in order to improve the progress of the calculation. The equation with the disturbance term added is described as shown in Equation 28. In the number 28, v _T1 ^k to v _T5 ^k and v _Rsk ^are disturbance terms.

The number 28 is rewritten as the following equation.

Here, x _k is a vector having a state quantity as an element (state vector), and v _k is a vector having a disturbance quantity as an element (disturbance vector). f represents the non-linear difference equation shown in Equation 28.

In the observation, a part of the state quantity is observed. In the following, it is assumed that the measured value of the temperature sensor 250 is the temperature of the binding portion in which the positive electrode tabs 211 are bundled.

The observation equation is expressed as the number 30.

Here, y _k is an observed value, c ^T is an observed vector, and w _k is an observed disturbance. Since the temperature T ₃ ^k of the binding portion of the positive electrode tab 211 is the third component of x _k , c ^T is expressed by the following equation. The T on the right shoulder of c represents transposition.

In the above-mentioned observation equation, it is assumed that there is only one observed value. Alternatively, there may be multiple observations.

Similar to the first embodiment, the detection device 10 sequentially calculates the time update of the time series model represented by the state equation of the number 29 and the observation equation of the number 30 using the particle filter, and determines the internal resistance R _s . Ask. The detection device 10 detects an internal short circuit in the power storage element 100 based on the obtained internal resistance R _s .

As described above, in the second embodiment, since the temperature sensor 250 is provided in the tab binding portion where the plurality of positive electrode tabs 211 (or the plurality of negative electrode tabs 221) are bundled, the temperature sensor 250 can be easily attached. In the second embodiment, the thermal circuit model MD2 is simplified and the number of parameters is reduced, so that the calculation becomes easy.

(Embodiment 3)
In the third embodiment, a state estimation algorithm using an ensemble Kalman filter will be described. That is, the detection device 10 in the third embodiment sequentially calculates the time update of the time series model represented by the state equation of the equation 15 and the observation equation of the equation 16 using the ensemble Kalman filter, and obtains the internal resistance R _s . .. The detection device 10 detects an internal short circuit of the power storage element 100 based on the obtained internal resistance R _s .

FIG. 12 is a flowchart illustrating a procedure for detecting an internal short circuit in the third embodiment. The calculation unit 11 of the detection device 10 gives an initial value of k = 1 (step S121). The calculation unit 11 may give the environmental temperature as the initial value of the temperature and give a temporary value preset as the initial value of the short-circuit resistance. Let the variances of the disturbance term v _k in the equation of state and the disturbance term w _k in the observation equation be Q _k and R _k , respectively.

Next, the arithmetic unit 11 generates N particles for each state variable (step S122). Here, a number of about ¹⁰² to ¹⁰⁶ is usually used for N.

Next, the arithmetic unit 11 generates a random number corresponding to v _k for i = 1, 2, ..., N (step S123). It is assumed that v _k follows a normal distribution and the variance is known.

The calculation unit 11 updates the state of the particles to the state of the particles in the next time step by executing the calculation based on the number 18 for all N particles (step S124).

The calculation unit 11 calculates the difference x _k ⁽ⁱ⁾ _bar between the state vector of each particle of i = 1, 2, ..., N and the average value of the state vector of all particles (step S125). x _k ⁽ⁱ⁾ _bar is represented by the number 33.

The calculation unit 11 calculates the covariance matrix P _k of the state quantity predicted values for all the particles (step S126). The covariance matrix P _k is represented by the number 34.

The calculation unit 11 acquires the sensor output of the temperature sensor 250 through the input unit 13 (step S127). The acquired sensor output of the temperature sensor 250 gives the observed value y _k ⁱ of each particle in the time step k.

The calculation unit 11 calculates the observation error r _k ⁱ in the time step k of the i-th particle (step S128). Here, w _k is an observation disturbance. The observation error r _k ⁱ is represented by the number 35.

The calculation unit 11 calculates the Kalman gain K _k in the time step k (step S129). The Kalman gain K _k is represented by the equation 36.

The calculation unit 11 calculates the estimated value x _k ⁽ⁱ⁾ _hat of the i-th particle (step S130). The estimated value x _k ⁽ⁱ⁾ _hat is represented by the number 37. That is, the arithmetic unit 11 corrects the first predicted value of the number 32 by using the observation error r _k ⁱ of the number 35 and the Kalman gain K _k of the number 36.

The calculation unit 11 calculates the average value x _k _hat of each particle (step S131). The average value x _k _hat of each particle represents the state vector estimated value obtained by the ensemble Kalman filter, and is calculated by the following equation.

The estimated value (mean value x _k _hat of each particle) obtained by the number 38 includes an estimated value of the temperature of each region and an estimated value of the short-circuit resistance. The calculation unit 11 estimates the presence or absence of an internal short circuit in the power storage element 100 based on the estimated value of the short circuit resistance. For example, the arithmetic unit 11 determines whether or not the estimated value of the short-circuit resistance is less than the threshold value (step S132). The threshold is set arbitrarily.

When the estimated value of the short circuit resistance is not less than the threshold value (S132: NO), it is estimated that no internal short circuit has occurred in the power storage element 100. If it is estimated that no internal short circuit has occurred, the calculation unit 11 returns the process to step S122 and executes the calculation in the next time step.

When the estimated value of the short circuit resistance is less than the threshold value (S132: YES), it is estimated that an internal short circuit has occurred in the power storage element 100. When it is estimated that an internal short circuit has occurred, the arithmetic unit 11 notifies the occurrence of the internal short circuit (step S133). For example, the arithmetic unit 11 generates character information indicating that an internal short circuit has occurred, outputs the character information to the display device 20 from the output unit 14, and causes the display device 20 to display the character information. Alternatively, the arithmetic unit 11 may notify the terminal device (not shown) of the character information indicating that an internal short circuit has occurred from the output unit 14. Further, the calculation unit 11 may urge the user to stop or replace the power storage element 100, or may ask the user to decide whether to stop or replace the power storage element 100.

The detection device 10 in the third embodiment estimates the short-circuit resistance by using the ensemble Kalman filter. The ensemble Kalman filter is a filter method for a state-space model having non-linearity and non-Gaussian property, and can target a more general state-space model. The ensemble Kalman filter has a relatively simple algorithm and can be easily implemented in the detection device 10.

(Embodiment 4)
In the fourth embodiment, a state estimation algorithm using an extended Kalman filter will be described. That is, the detection device 10 in the fourth embodiment sequentially calculates the time update of the time series model represented by the state equation of the equation 15 and the observation equation of the equation 16 using the extended Kalman filter, and obtains the internal resistance R _s . .. The detection device 10 detects an internal short circuit of the power storage element 100 based on the obtained internal resistance R _s .

FIG. 13 is a flowchart illustrating a procedure for detecting an internal short circuit in the fourth embodiment. The calculation unit 11 of the detection device 10 gives an initial value of k = 1 (step S141). The calculation unit 11 may give the environmental temperature as the initial value of the temperature and give a temporary value preset as the initial value of the short-circuit resistance. Let the variances of the disturbance term v _k in the equation of state and the disturbance term w _k in the observation equation be Q _k and R _k , respectively. Assume an initial variance-covariance matrix P.

The calculation unit 11 calculates the pre-state estimated value x ⁻ _{k + 1} _ hat by the following equation (step S142).

The arithmetic unit 11 derives the Jacobian determinant of the nonlinear transformation f by the following procedure (step S143). For example, when the nonlinear transformation f is expressed as the number 41 for the three-component vector represented by the number 40, the Jacobian is calculated by the number 42. The arithmetic unit 11 may derive the Jacobian in advance and store it in the storage unit 12.

The arithmetic unit 11 calculates the prior error covariance matrix P ⁻ _{k + 1} by the following equation (step S144). Here, the state transition matrix _Ak is represented by the number 44.

The calculation unit 11 calculates the Kalman gain g _k (step S145). The Kalman gain g _k is represented by the number 45.

The calculation unit 11 acquires the sensor output of the temperature sensor 250 through the input unit 13 (step S146). The acquired sensor output of the temperature sensor 250 gives the observed value y _k in the time step k.

The arithmetic unit 11 calculates the post-state estimated value x _{k + 1} _hat and the post-error covariance matrix P _k by the following equations (step S147).

The estimated value obtained by the number 46 (posterior state estimated value x _{k + 1} _hat) includes an estimated value of the temperature in each region and an estimated value of the short-circuit resistance. The calculation unit 11 estimates the presence or absence of an internal short circuit in the power storage element 100 based on the estimated value of the short circuit resistance. For example, the arithmetic unit 11 determines whether or not the estimated value of the short-circuit resistance is less than the threshold value (step S148). The threshold is set arbitrarily.

When the estimated value of the short circuit resistance is not less than the threshold value (S148: NO), it is estimated that no internal short circuit has occurred in the power storage element 100. If it is estimated that no internal short circuit has occurred, the calculation unit 11 returns the process to step S142 and executes the calculation in the next time step.

When the estimated value of the short circuit resistance is less than the threshold value (S148: YES), it is estimated that an internal short circuit has occurred in the power storage element 100. When it is estimated that an internal short circuit has occurred, the arithmetic unit 11 notifies the occurrence of the internal short circuit (step S149). For example, the arithmetic unit 11 generates character information indicating that an internal short circuit has occurred, outputs the character information to the display device 20 from the output unit 14, and causes the display device 20 to display the character information. Alternatively, the arithmetic unit 11 may notify the terminal device (not shown) of the character information indicating that an internal short circuit has occurred from the output unit 14. Further, the calculation unit 11 may urge the user to stop or replace the power storage element 100, or may ask the user to decide whether to stop or replace the power storage element 100.

The detection device 10 in the fourth embodiment estimates the short-circuit resistance by utilizing the extended Kalman filter. The extended Kalman filter is a method that enables the application of a Kalman filter by linearly approximating a nonlinear model near a representative value such as an average value. The extended Kalman filter has a small calculation load and can be realized by an inexpensive device.

(Embodiment 5)
In the fifth embodiment, a state estimation algorithm using an unscented Kalman filter will be described. That is, the detection device 10 in the fifth embodiment sequentially calculates the time update of the time series model represented by the state equation of the equation 15 and the observation equation of the equation 16 using the unscented Kalman filter, and determines the internal resistance R _s . Ask. The detection device 10 detects an internal short circuit of the power storage element 100 based on the obtained internal resistance R _s .

FIG. 14 is a flowchart illustrating a procedure for detecting an internal short circuit in the fifth embodiment. The calculation unit 11 of the detection device 10 gives an initial value of k = 1 (step S161). The calculation unit 11 may give the environmental temperature as the initial value of the temperature and give a temporary value preset as the initial value of the short-circuit resistance. Let Q _k and R _k be the variances of the disturbance term v _k in the equation of state and the disturbance term w _k in the observation equation, respectively. Assume an initial variance-covariance matrix P.

The calculation unit 11 generates a calculation point called a sigma point by using the estimated value x ⁻ _k obtained in a certain calculation step and the variance-covariance matrix P _k (step S162). When the generated (2n + 1) sigma points are numbered like the number 47, the j (j is an integer satisfying −n ≦ j ≦ n) th sigma point is expressed as the number 48.

However, sig (j) is a function that gives -1 when j <0, 0 when j = 0, and +1 when 0 <j. κ is a positive adjustment parameter.

The weight w _j of each sigma point is w _j = κ / 2 (n + κ) when j ≠ 0, and w ₀ = κ / (n + κ) when j = 0.

The arithmetic unit 11 updates the states of all sigma points, the pre-state estimated values, and the pre-error covariance matrix as in the following equation (step S163).

Since the calculation unit 11 has updated the pre-state estimated value and the pre-error covariance matrix, the sigma point is recalculated by the following equation (step S164).

The arithmetic unit 11 updates the sigma point of the observation according to the following equation (step S165).

The calculation unit 11 calculates the pre-observed estimated value y ⁻ _{k + 1} _ hat by the following equation (step S166).

The arithmetic unit 11 calculates the covariance matrix P ^- _{yy, k + 1} of the prior observation error by the following equation (step S167).

The arithmetic unit 11 calculates the covariance matrix P ^- _{xy, k + 1} of the prior state / observation error by the following equation (step S168).

The calculation unit 11 calculates the Kalman gain g _k by the following equation (step S169).

The calculation unit 11 acquires the sensor output of the temperature sensor 250 through the input unit 13 (step S170). The acquired sensor output of the temperature sensor 250 gives the observed value y _{k +} 1 in the time step k + 1.

The arithmetic unit 11 multiplies the Kalman gain g _k by the difference between the observed value y _{k + 1} and the pre-observed estimated value y ⁻ _{k + 1} _ hat to estimate the state in the time step k + 1 (step S171).

The arithmetic unit 11 calculates the covariance matrix P _{k + 1} of the post-observation error by the following equation (step S172).

The post-observation estimate (x _{k + 1} _hat) obtained by the number 56 includes an estimate of the temperature in each region and an estimate of the short-circuit resistance. The calculation unit 11 estimates the presence or absence of an internal short circuit in the power storage element 100 based on the estimated value of the short circuit resistance. For example, the arithmetic unit 11 determines whether or not the estimated value of the short-circuit resistance is less than the threshold value (step S173). The threshold is set arbitrarily.

When the estimated value of the short circuit resistance is not less than the threshold value (S173: NO), it is estimated that no internal short circuit has occurred in the power storage element 100. If it is estimated that no internal short circuit has occurred, the arithmetic unit 11 returns the process to step S162 and executes the arithmetic in the next time step.

When the estimated value of the short circuit resistance is less than the threshold value (S173: YES), it is estimated that an internal short circuit has occurred in the power storage element 100. When it is estimated that an internal short circuit has occurred, the arithmetic unit 11 notifies the occurrence of the internal short circuit (step S174). For example, the arithmetic unit 11 generates character information indicating that an internal short circuit has occurred, outputs the character information to the display device 20 from the output unit 14, and causes the display device 20 to display the character information. Alternatively, the arithmetic unit 11 may notify the terminal device (not shown) of the character information indicating that an internal short circuit has occurred from the output unit 14. Further, the calculation unit 11 may urge the user to stop or replace the power storage element 100, or may ask the user to decide whether to stop or replace the power storage element 100.

The detection device 10 in the fifth embodiment estimates the short-circuit resistance by using an unscented Kalman filter. The unscented Kalman filter provides a plurality of sample points called sigma points around the mean value, and estimates the covariance matrix based on these statistical properties. Fragrance-free Kalman filters perform better than extended Kalman filters in the problem of strong non-linearity.

(Embodiment 6)
In the sixth embodiment, a configuration in which the detection device 10 detects a sign of an internal short circuit based on the short circuit resistance R _s will be described.

FIG. 15 is a flowchart illustrating a procedure for detecting a sign of an internal short circuit. The arithmetic unit 11 of the detection device 10 sequentially estimates the short-circuit resistance R _s in the power storage element 100 by using the same procedure as in the first to fifth embodiments (step S201).

The calculation unit 11 determines whether or not the estimated short-circuit resistance R _s is lower than the reference value by a predetermined ratio (step S202). As the reference value, the average value of the short-circuit resistance R _s when no internal short circuit has occurred is set. The ratio set as the threshold value is appropriately set. For example, if a sign of an internal short circuit is detected when the short circuit resistance R _s drops by 10% or more from the reference value, the threshold value is set to 10%.

When the estimated short-circuit resistance R _s is not lower than the reference value by a predetermined ratio (S202: NO), the calculation unit 11 returns the process to step S201 and continues the estimation of the short-circuit resistance R _s .

The calculation unit 11 estimates that a sign of an internal short circuit has occurred when the estimated short-circuit resistance R _s is lower than the reference value by a predetermined ratio (S202: YES). When the calculation unit 11 determines that a sign of an internal short circuit has occurred, the calculation unit 11 notifies the sign of an internal short circuit (step S203). For example, the arithmetic unit 11 generates character information indicating that a sign of an internal short circuit has been detected, and outputs the character information to the display device 20 from the output unit 14 so that the display device 20 displays the information. Alternatively, the arithmetic unit 11 may notify the terminal device (not shown) of the character information indicating that the sign of the internal short circuit has been detected from the output unit 14. Further, the calculation unit 11 may urge the user to stop or replace the power storage element 100, or may ask the user to decide whether to stop or replace the power storage element 100.

In the sixth embodiment, the sign of an internal short circuit is detected by determining whether or not the estimated internal resistance R _s is lower than the reference value by a predetermined ratio. Alternatively, the arithmetic unit 11 may detect a sign of an internal short circuit based on whether or not the estimated internal resistance R _s has continuously decreased a set number of times (for example, 5 times) as a criterion.

In the first to sixth embodiments, an internal short circuit including a sign is detected based on the sensor output of the temperature sensor 250 that measures the temperature of the conductive tab. However, when the motor sports vehicle is running or a heavy machine is driven with a large torque. When a large current is output from the power storage element 100, such as when used, the conductive tab may reach a high temperature. In this case, although the conductive tab reaches a high temperature, it is within the range of normal use and is not an abnormality such as an internal short circuit. In order to distinguish between the case where the conductive tab reaches a high temperature due to normal use and the case where the conductive tab reaches a high temperature due to an internal short circuit, heat transfer calculation based on the current flowing through the power storage element 100 is performed at the same time. You may. The detection device 10 compares the temperature of the conductive tab measured by the temperature sensor 250 with the temperature of the conductive tab estimated from the current of the power storage element 100, and if the two values are close to each other, the temperature rises due to an internal short circuit. However, it can be judged that the temperature rise during normal use. On the other hand, when the temperature rise that cannot occur from the current flowing through the power storage element 100 is measured, the detection device 10 may determine that an internal short circuit may have occurred.

(Embodiment 7)
In the seventh embodiment, a configuration will be described in which the current path between the electrode terminal 310 and the conductive tab (positive electrode tab 211 or negative electrode tab 221) is cut off when an internal short circuit of the power storage element 100 is detected.

The power storage element 100 according to the seventh embodiment cuts off the current path between the electrode terminal 310 and the conductive tab (positive electrode tab 211 or negative electrode tab 221) when the detection device 10 detects an internal short circuit of the power storage element 100. Equipped with a circuit breaker.

16 is a partial cross-sectional view of the power storage element 100 according to the seventh embodiment, and FIG. 17 is a perspective view showing an example of mounting a circuit breaker. The power storage element 100 includes a control board 150, a control circuit 151, and a semiconductor switching element 152 (hereinafter referred to as FET 152) in addition to the configuration described in the first embodiment. These are mounted, for example, in a space provided between the lid 112 of the power storage element 100 and the current collector 140. In the seventh embodiment, the current collector 140 is divided into a first current collector 140a and a second current collector 140b. The first current collector 140a and the second current collector 140b are arranged with a gap. A positive electrode tab 211 is connected to the first current collector 140a, and a terminal electrode 310 is connected to the second current collector 140b.

The control board 150 is provided on the first current collector 140a and the second current collector 140b. The control board 150 is provided with rectangular notches 150a and 150b. The control circuit 151 is mounted on the control board 150. The FET 152 is mounted on the exposed surface of the first current collector 140a exposed from the notch 150a.

The control circuit 151 acquires a detection result from the above-mentioned detection device 10, and turns on / off the FET 152 according to the acquired detection result. In the seventh embodiment, the control circuit 151 and the detection device 10 are separated for convenience. Alternatively, the control circuit 151 and the detection device 10 may be integrated.

The FET 152 is, for example, a power MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) for switching. The gate terminal 152G of the FET 152 is connected to the control circuit 151 via a printed wiring (not shown) formed on the control board 150. The drain terminal 152D is connected on the exposed surface of the first current collector 140a exposed from the notch 150a. The source terminal 152S straddles the gap between the first current collector 140a and the second current collector 140b, and is connected to the exposed surface of the second current collector 140b exposed from the notch 150b of the control board 150. ..

The control circuit 151 can connect the drain terminal 152D and the source terminal 152S by applying a predetermined voltage (gate voltage) to the gate terminal 152G of the FET 152. As a result, the current path between the electrode terminal 310 and the positive electrode tab 211 is connected. On the other hand, if the gate voltage is set to zero, the control circuit 151 can cut off between the drain terminal 152D and the source terminal 152S. As a result, the current path between the electrode terminal 310 and the positive electrode tab 211 is cut off.

In the seventh embodiment, the FET 152 is interposed in the current path between the electrode terminal 310 and the positive electrode tab 211. Alternatively, the FET 152 may be interposed in the current path between the electrode terminal 320 and the negative electrode tab 221.

In the seventh embodiment, for the sake of simplification, a configuration in which only one FET 152 is mounted has been described. Alternatively, the power storage element 100 may further include an FET 152 in which the drain terminal 152D is connected to the second current collector 140b and the source terminal 152S is connected to the first current collector 140a.

In the seventh embodiment, the configuration in which the power storage element 100 is provided with the FET 152 as a circuit breaker for blocking the current path between the electrode terminal 310 and the conductive tab (positive electrode tab 211 or negative electrode tab 221) has been described. Alternatively, a mechanical switch whose on / off is controlled by the control circuit 151, a switch using a bimetal that is deformed by raising the temperature from the control circuit 151, a fuse that blows by raising the temperature from the control circuit 151, etc. Any circuit breaker may be used. Further, when the power storage element 100 includes a plurality of electrode bodies 200, the control circuit 151 may cut off only the current path connected to the electrode body 200 in which the internal short circuit has occurred.

FIG. 18 is a flowchart illustrating a procedure of processing executed by the control circuit 151. The control circuit 151 acquires the detection result from the detection device 10 and determines whether or not an internal short circuit has occurred in the power storage element 100 (step S301).

When the control circuit 151 determines that an internal short circuit has not occurred in the power storage element 100 (S301: NO), the control circuit 151 maintains the ON state of the FET 152 (step S302), and returns the process to step S301.

When the control circuit 151 determines that an internal short circuit has occurred in the power storage element 100 (S301: YES), the control circuit 151 turns off the FET 152 to establish a current path between the electrode terminal 310 and the positive electrode tab 211. Shut off (step S303).

As described above, in the seventh embodiment, when the internal short circuit of the power storage element 100 is detected in the detection device 10, the control circuit 151 has the electrode terminal 310 and the conductive tab (positive electrode tab 211 or negative electrode tab 221). Since the current path between them is cut off, it is possible to prevent the power storage element 100 from becoming hot.

In the seventh embodiment, a configuration in which the current path is cut off by using the FET 152 has been described. Alternatively, a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor), a thyristor, or a bipolar transistor may be used. Further, bimetal may be used for the conductive tab so that the conductive tab is distorted and cut by raising the temperature. Further, the current path may be cut off by removing the restraint by the mechanical spring. Further, the current path may be cut off by fusing.

In the seventh embodiment, when the detection device 10 detects an internal short circuit of the power storage element 100, the control circuit 151 cuts off the current path. Alternatively, when the detection device 10 detects a sign of an internal short circuit of the power storage element 100, the control circuit 151 may cut off the current path. Since the operating device or the running vehicle may suddenly stop due to the current path being cut off, the control circuit 151 cuts off the current path after confirming that the device or the vehicle equipped with the power storage element 100 is stopped. You may.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims, not the above-mentioned meaning, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

For example, in the first to seventh embodiments, the storage element 100 provided with the laminated electrode body 200 has been described as an example to explain the method for detecting an internal short circuit, but the target for detecting the internal short circuit is a wound type electrode. It may be a power storage element provided with a body. However, in the laminated type electrode body 200, the positive electrode plates (or the negative electrode plates) are electrically connected to each other only via the positive electrode tab 211 (or the negative electrode tab 221), whereas in the wound type electrode body. The positive electrode plates (or the negative electrode plates) are connected to each other via not only the tab but also the winding portion. Therefore, the winding type electrode body has an aspect that even if the conductive tab is cut, the short circuit continues through the winding portion. The effect of the present application is more effectively exhibited in the power storage element 100 provided with the laminated electrode body 200 than in the power storage element provided with the winding type electrode body.

The power storage element in the embodiment may be a laminated type power storage element. FIG. 19 is an external perspective view showing the laminated type power storage element 500, and FIG. 20 is an exploded perspective view showing the laminated type power storage element 500. The power storage element 500 includes an exterior body 510 made of a laminated film, and positive electrode lead terminals 520 and negative electrode lead terminals 530 protruding outward from both ends in the longitudinal direction of the power storage element 500, respectively. A power generation element 540 and an electrolytic solution (not shown) are housed inside the exterior body 1. The power generation element 540 shown as an example in FIG. 20 has a structure in which a strip-shaped positive electrode and a negative electrode are wound to form an elongated cylinder.

The exterior body 510 is formed in a tubular shape by stacking two laminated films so as to face each other and welding them at their respective ends. The welded portions at both ends of the power storage element 500 are welded so as to sandwich the positive electrode lead terminal 520 and the negative electrode lead terminal 530, respectively. The exterior body 510 has, for example, a laminated structure in which a PE (polyethylene) welding layer, a PET (polyethylene terephthalate) layer, an aluminum layer, a PET layer, and a PE layer are laminated in this order.

The positive electrode lead terminal 520 is joined to the positive electrode of the power generation element 540 inside the exterior body 510. The positive electrode lead terminal 520 is composed of, for example, a clad material (laminated body) in which an aluminum layer and a titanium layer are rolled and joined.

The negative electrode lead terminal 530 is bonded to the negative electrode of the power generation element 540 inside the exterior body 510. The negative electrode lead terminal 530 is composed of, for example, a laminated body including a copper layer and titanium layers provided on both sides of the copper layer.

In the power storage element 500 described above, the temperature sensor 250 is attached to the positive electrode lead terminal 520 (or the negative electrode lead terminal). The detection device 10 may acquire the sensor output of the temperature sensor 250 and detect the internal short circuit of the power storage element 500 based on the acquired sensor output. The method for detecting an internal short circuit is the same as the detection method described in the first to sixth embodiments. Similar to the seventh embodiment, the power storage element may include a circuit breaker that cuts off the current path via the positive electrode lead terminal 520 (or the negative electrode lead terminal 530) when an internal short circuit of the power storage element 500 is detected. ..

10 Detection device 11 Calculation unit 12 Storage unit 13 Input unit 14 Output unit 100 Power storage element 110 Container 150 Control board 151 Control circuit 152 Semiconductor switching element 200 Electrode body 210 Positive electrode plate 211 Positive electrode tab 220 Negative electrode plate 221 Negative electrode tab 250 Temperature sensor 230 Separator 310 Electrode terminal 320 Electrode terminal PG State estimation program MD1, MD2 Thermal circuit model

Claims (10)

From a temperature sensor that has an electrode terminal and an electrode body having a conductive tab and measures the temperature of the conductive tab with respect to a power storage element in which the electrode body is connected to the electrode terminal via the conductive tab. A breaking device provided with a breaking portion that cuts off a current path between the electrode terminal and the electrode body based on the sensor output of the above. A detector for detecting an internal short circuit in the electrode body based on the sensor output is provided.
The cutoff device according to claim 1, wherein the cutoff unit cuts off a current path between the electrode terminal and the electrode body according to the detection result of the detection unit. The cutoff device according to claim 2, wherein the detection unit includes an observer for estimating the short-circuit resistance of the internal short circuit based on the sensor output. The second or third aspect of the present invention, wherein the detection unit estimates the short-circuit resistance of the internal resistance by using a state estimation algorithm based on the sensor output and a thermal circuit model simulating the thermal phenomenon of the power storage element. Breaking device. The cutoff according to claim 4, wherein the thermal circuit model includes the electrode body, the conductive tab, and a short-circuited portion at the nodes, and includes the temperature and heat capacity at each node and the thermal resistance between the nodes as parameters. Device. The state estimation algorithm is
Obtain the time transition of each state variable using the equation of state that expresses the time transition of the state variable including the temperature and short-circuit resistance of each node.
The likelihood of state estimation is obtained using an observation equation that describes the relationship between the state variable and the observed amount including the temperature observed by the temperature sensor.
The blocking device according to claim 5, further comprising a procedure for updating the estimated value of the state variable according to the likelihood of the obtained state estimation. The blocking device according to any one of claims 4 to 6, wherein the state estimation algorithm includes a particle filter, an ensemble Kalman filter, an extended Kalman filter, or an unscented Kalman filter. The blocking device according to any one of claims 1 to 7, wherein the electrode body is a laminated electrode body. A power storage element having an electrode terminal and an electrode body having a conductive tab, and connecting the electrode body to the electrode terminal via the conductive tab.
A power storage element including a temperature sensor that measures the temperature of the conductive tab. The power storage element according to claim 9, further comprising a blocking unit that cuts off a current path between the electrode terminal and the electrode body based on the sensor output from the temperature sensor.

Images