阅读说明：本技术 模拟方法、模拟装置以及计算机程序 (Simulation method, simulation device, and computer program ) 是由 冈部洋辅 山手茂树 于 2020-01-29 设计创作，主要内容包括：本发明提供一种模拟方法、模拟装置以及计算机程序。在模拟方法中,接受与蓄电器件有关的模拟条件,基于接受到的模拟条件,计算短路电流来模拟从蓄电器件向外部的热现象。(The invention provides a simulation method, a simulation device and a computer program. In the simulation method, a simulation condition relating to the electric storage device is received, and a short-circuit current is calculated based on the received simulation condition to simulate a thermal phenomenon from the electric storage device to the outside.)

1. A simulation method, characterized in that,

receiving a simulation condition relating to the power storage device,

based on the received simulation conditions, a short-circuit current is calculated to simulate a thermal phenomenon from the power storage device to the outside.

2. The simulation method of claim 1,

the simulation condition includes a site of occurrence of an internal short circuit in the power storage device,

simulating the thermal phenomenon accompanying the internal short circuit.

3. The simulation method according to claim 1 or 2,

the electricity storage device includes a wound electrode body,

the short-circuit current is calculated in a state where the wound electrode body is virtually unrolled.

4. The simulation method of claim 1,

the simulation condition includes information associated with a resistance value in an external short circuit of the power storage device,

simulating the thermal phenomenon accompanying the external short circuit.

5. The simulation method according to any one of claims 1 to 4,

the simulation conditions include a heating portion, heat, and ambient temperature when the power storage device is heated from the outside,

simulating the thermal phenomenon accompanying heating of the power storage device.

6. A simulation method, characterized in that,

receiving a simulation condition relating to the power storage device,

the simulation condition includes a heating portion when the power storage device is heated from outside,

based on the received simulation conditions, a thermal phenomenon from the power storage device to the outside accompanying heating of the power storage device is simulated.

7. The simulation method according to claim 1 or 6,

the relationship between the temperature and the amount of heat generated by the differential thermal analysis of the power storage device is formulated,

the heat generation rate in the material decomposition reaction of the electricity storage device is calculated based on the relational expression between the temperature and the heat generation amount obtained by the formulation.

8. A simulation method, characterized in that,

receiving a simulation condition relating to the power storage device,

the generation of gas accompanying the material decomposition reaction of the electric storage device is simulated based on the received simulation conditions.

9. The simulation method of claim 8,

calculating at least one of a generation rate of the gas and a generation rate of heat based on a reaction rate of the material decomposition reaction.

10. The simulation method of claim 9,

the generation rate of the gas is calculated to be proportional to the reaction rate of the material decomposition reaction.

11. A simulation method, characterized in that,

receiving a simulation condition relating to the first power storage device,

calculating a short-circuit current based on the received simulation condition to simulate a thermal phenomenon from the first power storage device to the outside,

simulating a thermal phenomenon from the second power storage device to the outside accompanying heating of the second power storage device caused by the thermal phenomenon from the first power storage device to the outside.

12. A simulation method, characterized in that,

receiving a simulation condition relating to the first power storage device,

the simulation condition includes a heating portion when the first power storage device is heated from outside,

simulating a thermal phenomenon from the first power storage device to the outside accompanying heating of the first power storage device based on the received simulation condition,

simulating a thermal phenomenon from the second power storage device to the outside accompanying heating of the second power storage device caused by the thermal phenomenon from the first power storage device to the outside.

13. The simulation method according to any one of claims 1 to 12,

receiving a simulated condition transmitted from an external terminal after user authentication using the external terminal,

transmitting a simulation result based on the received simulation condition or a simulation program based on the simulation condition to the external terminal.

14. A simulation device is characterized by comprising:

a receiving unit that receives a simulation condition relating to the power storage device;

a simulation execution unit that calculates a short-circuit current based on the received simulation condition to simulate a thermal phenomenon from the power storage device to the outside; and

and an output unit that outputs a simulation program based on a simulation result of the simulation execution unit or based on the simulation condition.

15. A computer program for causing a computer to execute:

a user interface for prompting acceptance of a simulation condition related to the power storage device,

based on the received simulation conditions, a short-circuit current is calculated to simulate a thermal phenomenon from the power storage device to the outside.

Technical Field

The present invention relates to a simulation method, a simulation apparatus, and a computer program for computer installation.

Background

In recent years, MBD (model-based development) has been actively introduced into various industries including the automobile industry, and product development by simulation has been pervasive (for example, see patent document 1).

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 11-14507

Disclosure of Invention

Problems to be solved by the invention

In the model-based development, for example, a case where thermal safety is simulated for a specific power storage device that is one of the development elements is considered. Various conditions need to be set according to physical and chemical phenomena occurring inside the power storage device. In the event of safety of the electric storage device, a plurality of physical phenomena such as chemical reaction, heat transfer, electric current, electrochemistry, and hydrodynamics are related to each other, and the mechanism and the physical property value are not known in many cases. Therefore, it is difficult for a technician who is not familiar with the battery to simulate the safety of the power storage device. However, in view of recent remarkable development progress of electric vehicles, renewable energy sources, smart grids, and the like, expectations for high-performance and high-safety power storage devices are high, and it is important to sufficiently utilize the simulated safety design.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a simulation method, a simulation apparatus, and a computer program that enable even a technician who is not familiar with a battery to easily simulate a thermal phenomenon of an electric storage device.

Means for solving the problems

In the simulation method, a simulation condition relating to the electric storage device is received, and a short-circuit current is calculated based on the received simulation condition to simulate a thermal phenomenon from the electric storage device to the outside.

The simulation device is provided with: a receiving unit that receives a simulation condition relating to the power storage device; a simulation execution unit that calculates a short-circuit current based on the received simulation condition to simulate a thermal phenomenon from the power storage device to the outside; and an output unit that outputs a simulation program based on a simulation result of the simulation execution unit or based on the simulation condition.

The computer program is for causing a computer to execute: a user interface for presenting the reception of simulation conditions relating to the electric storage device calculates a short-circuit current based on the received simulation conditions, and simulates a thermal phenomenon from the electric storage device to the outside.

Effects of the invention

According to the above configuration, even a technician who is not familiar with the battery can easily simulate the thermal phenomenon of the power storage device.

Drawings

Fig. 1 is a schematic diagram illustrating an overall configuration of a simulation system according to an embodiment.

Fig. 2 is a block diagram illustrating an internal configuration of the server apparatus.

Fig. 3 is a conceptual diagram illustrating an example of the battery table.

Fig. 4 is a block diagram illustrating an internal structure of a client device.

Fig. 5 is a schematic diagram showing an example of an acceptance screen for accepting a simulation condition.

Fig. 6 is a schematic explanatory view for explaining a simulation technique.

Fig. 7 is a flowchart illustrating a procedure of processing performed by the server apparatus and the client apparatus.

Fig. 8 is an explanatory diagram for explaining the components of the electric storage device according to embodiment 3.

Fig. 9 is a view showing an electrode body of the type having electrode tabs of a wound unit.

Fig. 10 is an explanatory view for explaining the appearance of the short-circuited part under the penetration short-circuit in the wound electrode assembly.

Fig. 11 is an explanatory view explaining the appearance of the short-circuit portion in the wound electrode assembly under the partial short-circuit.

Fig. 12 is a schematic diagram showing a system (battery pack) including a plurality of power storage devices.

Fig. 13 is a graphic display (moving image display) for visualizing a situation where a plurality of power storage devices discharge gas in a chain manner in the system of fig. 12.

Detailed Description

In the simulation method, a simulation condition relating to the electric storage device is received, and a short-circuit current is calculated based on the received simulation condition to simulate a thermal phenomenon from the electric storage device to the outside. The outside may be, for example, a case of a power storage system in which a power storage device or a plurality of power storage devices are housed, a battery housing unit of a vehicle, or a space outside a building in which the power storage device is housed.

According to this configuration, the thermal phenomenon from the power storage device to the outside can be simulated based on the received simulation condition. Examples of the thermal phenomenon from the power storage device to the outside include joule heat and a heat generation phenomenon due to a material decomposition reaction accompanying an internal short circuit or an external short circuit, a heat generation phenomenon due to a material decomposition reaction when the power storage device is heated from the outside, and generation of gas accompanying heat generation of the power storage device. The present simulation method calculates the heat generation rate of the power storage device, the gas generation rate, and the like based on the simulation conditions.

In the simulation method, the simulation condition transmitted from the external terminal may be received after user authentication using the external terminal, and the execution result of the simulation based on the received simulation condition may be transmitted to the external terminal. According to this configuration, even when the user is not well versed in the theory showing the operation of the power storage device, the user can be provided with the simulation result or the simulation program of the thermal phenomenon occurring outside the power storage device by merely receiving the simulation condition.

The simulation condition may include a site of occurrence of an internal short circuit in the electric storage device, and the simulation method may simulate the thermal phenomenon accompanying the internal short circuit. The simulation condition may further include information related to a resistance value of the short-circuit portion. The information related to the resistance value of the short-circuited portion may include the name (e.g., nickel or iron) and shape (e.g., circle, quadrangle, or size thereof) of the substance in which the internal short-circuit has occurred, the mode of the internal short-circuit (e.g., collision, nail penetration, or mixing of foreign substances), and the like, and it is preferable that the resistance value of the short-circuited portion can be calculated from the information. The information related to the resistance value of the short-circuited portion may directly indicate the resistance value of the short-circuited portion, such as the contact resistance between the short-circuited portion and a member (e.g., a positive electrode collector foil) constituting the electric storage device, instead of the indirect information described above. According to this configuration, by providing the occurrence point of the internal short circuit, it is possible to simulate a thermal phenomenon associated with the internal short circuit at a different occurrence point.

The power storage device may include a wound electrode body, and in the simulation method, the short-circuit current may be calculated in a state where the wound electrode body is virtually unwound. According to this configuration, since the short-circuit current is calculated in consideration of the structure of the winding unit, it is possible to accurately simulate the thermal phenomenon corresponding to the through short circuit or the partial short circuit.

The simulation condition may include information related to a resistance value in an external short circuit of the power storage device, and in the simulation method, the thermal phenomenon accompanying the external short circuit may be simulated. According to this configuration, by providing information relating to the resistance value in the external short circuit, it is possible to simulate a thermal phenomenon associated with the external short circuit.

In a simulation method according to another embodiment, a simulation condition regarding an electric storage device is received, the simulation condition including a heating portion when the electric storage device is heated from outside, and a thermal phenomenon from the electric storage device to outside accompanying heating of the electric storage device is simulated based on the received simulation condition. The simulated conditions may further comprise heat of external heating. The simulated conditions may further include ambient temperature. According to this configuration, by providing the heating portion when the power storage device is heated from the outside, the thermal phenomenon accompanying heating can be simulated.

In the simulation method, the thermal phenomenon may be simulated by a joint analysis of an electrochemical reaction in the electric storage device and an exothermic reaction in a material decomposition reaction of the electric storage device. Since the heat generation reaction and joule heat generation of the battery are not independent physical phenomena but occur in association with each other through a physical phenomenon such as heat transfer, the phenomenon occurring inside the battery can be accurately reflected by performing joint analysis to simulate the operation of the battery.

In the simulation method, the relationship between the temperature and the amount of heat generated by the differential thermal analysis of the electric storage device may be formulated, and the rate of heat generation in the material decomposition reaction of the electric storage device may be calculated based on the relationship between the temperature and the amount of heat generated by the formulation. According to this configuration, since the relationship between the temperature and the amount of heat generation obtained by the differential thermal analysis is formulated, the time and the amount of heat generation are converted into the relationship between the temperature and the amount of heat generation.

In the simulation method according to another embodiment, simulation conditions relating to the electric storage device are received, and generation of gas accompanying a material decomposition reaction of the electric storage device is simulated based on the received simulation conditions. When an event such as an internal short circuit occurs in the electric storage device and the safety mechanism does not function properly, a material decomposition reaction may proceed and high-temperature gas may be ejected from the inside of the electric storage device. In the present simulation method, generation of gas accompanying the material decomposition reaction can be simulated.

In the simulation method, at least one of the generation rate of the gas and the generation rate of heat may be calculated based on a reaction rate of the material decomposition reaction. The rate of generation of the gas may be calculated to be proportional to the reaction rate of the material decomposition reaction. According to this structure, at least one of the generation rate of gas and the generation rate of heat can be calculated based on the reaction rate of the material decomposition reaction.

The simulation device is provided with: a receiving unit that receives a simulation condition relating to the power storage device; a simulation execution unit that calculates a short-circuit current based on the received simulation condition to simulate a thermal phenomenon from the power storage device to the outside; and an output unit that outputs a simulation program based on a simulation result of the simulation execution unit or based on the simulation condition.

According to this configuration, the thermal phenomenon from the power storage device to the outside can be simulated based on the received simulation condition. The thermal phenomenon from the power storage device to the outside includes, for example, a heat generation phenomenon caused by a material decomposition reaction accompanying an internal short circuit or an external short circuit, a heat generation phenomenon caused by a material decomposition reaction when the power storage device is heated from the outside, and generation of gas accompanying heat generation of the power storage device. The simulation apparatus calculates the heat generation rate of the electric storage device, the gas generation rate, and the like based on the simulation conditions.

The computer program causes a computer to execute: a user interface for presenting the acceptance of simulation conditions relating to the electric storage device executes calculation of a short-circuit current based on the accepted simulation conditions to simulate a thermal phenomenon from the electric storage device to the outside.

According to this configuration, the thermal phenomenon from the power storage device to the outside can be simulated based on the received simulation condition. The thermal phenomenon from the power storage device to the outside includes, for example, a heat generation phenomenon due to a material decomposition reaction accompanying an internal short circuit or an external short circuit, a heat generation phenomenon due to a material decomposition reaction in the case of heating the power storage device from the outside, and generation of gas accompanying heat generation of the power storage device. The computer program calculates the heat generation rate of the electric storage device, the gas generation rate, and the like based on the simulation conditions.

Hereinafter, the present invention will be specifically described based on the drawings showing the embodiment.

(embodiment mode 1)

Fig. 1 is a schematic diagram illustrating an overall configuration of a simulation system according to an embodiment. The simulation system according to the present embodiment includes a server device 100 and a client device 200 that are communicably connected to each other via a communication network N. The server apparatus 100 simulates a thermal phenomenon occurring from the power storage device to the outside in response to a request from the client apparatus 200, and provides the simulation result to the client apparatus 200. Here, the power storage device to be simulated includes a rechargeable power storage element (cell) such as a lead storage battery or a lithium ion battery, or a capacitor. The power storage device to be simulated may include a module in which a plurality of cells are connected in series, a group (series-connected battery pack) in which a plurality of modules are connected in series, a domain (parallel-connected battery pack) in which a plurality of groups are connected in parallel, and the like.

The client apparatus 200 is a terminal apparatus such as a personal computer, a smart phone, and a tablet terminal used by a user. Software (application program) for accessing the server device 100 is installed in the client device 200. When receiving an access from the client apparatus 200, the server apparatus 100 performs user authentication based on, for example, a user ID and a password, and provides an appropriate service to the client apparatus 200 when the user authentication is successful.

The server apparatus 100 according to the present embodiment transmits an interface screen for accepting various inputs by the user of the client apparatus 200 to the client apparatus 200 after user authentication. The interface screen includes, for example, an acceptance screen for accepting a simulation condition. The server apparatus 100 transmits the simulation result executed based on the received condition to the client apparatus 200.

The simulation result transmitted from the server apparatus 100 to the client apparatus 200 includes numerical data, graphs, and the like obtained as a result of execution of the simulation. The simulation result transmitted from the server apparatus 100 to the client apparatus 200 may include a mathematical model obtained as a result of execution of the simulation or a simulation program based on simulation conditions.

In the present embodiment, the simulation conditions are received by the client apparatus 200, and the received simulation conditions and the like are transmitted to the server apparatus 100 to execute the simulation. Alternatively, the simulation conditions may be received by the server device 100, and the simulation may be executed based on the received simulation conditions or the like, and the simulation result may be displayed by the server device 100.

Fig. 2 is a block diagram illustrating the internal configuration of the server apparatus 100. The server device 100 includes a control unit 101, a storage unit 102, a communication unit 103, an operation unit 104, and a display unit 105.

The control Unit 101 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU of the control unit 101 expands and executes various computer programs stored in the ROM or the storage unit 102 on the RAM, thereby causing the entire device to function as the simulation device of the present application. The server apparatus 100 is only one embodiment of the simulation apparatus, and may be any information processing apparatus that can be communicatively connected to the client apparatus 200.

The control Unit 101 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 nonvolatile memory, and the like. The control unit 101 may have a function of a timer for measuring an elapsed time from when the measurement start instruction is given to when the measurement end instruction is given, a counter for counting the number of times, a clock for outputting date and time information, and the like.

The storage unit 102 includes a storage device using an hdd (hard Disk drive), an ssd (solid State drive), or the like. The storage unit 102 stores various computer programs executed by the control unit 101, data necessary for executing the computer programs, and the like. The computer program stored in the storage unit 102 includes a simulation program for simulating a thermal phenomenon occurring from the power storage device to the outside. The simulation program is, for example, executing a binary file. The theoretical expression that forms the basis of the simulation program is described by an algebraic equation or a differential equation that represents a thermal phenomenon that occurs from the power storage device to the outside. The simulation program may be a single computer program or a program group including a plurality of computer programs. The simulation program may be selected from MATLAB (registered trademark), Amesim (registered trademark), Twin Bui₁der (registered trademark), MATLAB&Examples of the software include commercially available numerical analysis software and programming languages such as Simulink (registered trademark), Simplorer (registered trademark), ANSYS (registered trademark), Abaqus (registered trademark), Modelica (registered trademark), VHDL-AMS (registered trademark), C-speech, C + +, and Java (registered trademark). The numerical analysis software may be a circuit simulator called 1D-CAE, or a simulation based on a finite element method, a finite volume method, or the like of a 3D shape. A Reduced-Model (ROM: Reduced-Order Model) based on these can also be used.

The program stored in the storage section 102 may be provided by a nonvolatile recording medium M in which the program is recorded in a readable manner. The recording medium M is a portable memory such as a CD-ROM, a USB (Universal Serial Bus) memory, an SD (Secure Digital) card, a micro SD card, a compact flash (registered trademark), or the like. In this case, the control unit 101 reads the program from the recording medium M using a reading device not shown, and installs the read program in the storage unit 102. The program stored in the storage unit 102 can be provided by communication via the communication unit 103. In this case, the control unit 101 acquires the program through the communication unit 103, and installs the acquired program in the storage section 102.

The storage unit 102 may store a mathematical model obtained as a result of the simulation. The mathematical model is, for example, an execution code executed by a programming language or numerical analysis software. The mathematical model may also be a library file or definition information referenced by a programming language or numerical analysis software.

The storage unit 102 may have a battery table in which information of a power storage device (e.g., a secondary battery) is stored in association with a user ID. Fig. 3 is a conceptual diagram illustrating an example of the battery table. The battery table stores, for example, a battery ID for identifying a battery, a user ID for identifying a user, and battery information in association with each other. The battery information registered in the battery table includes, for example, information on the positive electrode and the negative electrode, information on the electrolytic solution, information on the current collector, and the like. The information on the positive electrode and the negative electrode means information on the positive electrode and the negative electrode such as the name, thickness, width, depth, and open circuit potential of the active material. The information on the electrolyte and the current collector refers to information on ion species, transport number, diffusion coefficient, conductivity, and the like. The battery list may include a link for referring to information such as physical properties, operating states, and circuit configurations of the power storage device. The information stored in the battery table may be registered by the administrator of the server apparatus 100 or may be registered by the user via the client apparatus 200. The information stored in the battery gauge is used as part of the simulation conditions when simulating the thermal phenomenon of the power storage device.

The communication unit 103 includes an interface for communicating with the client apparatus 200 via the communication network N. When information to be transmitted to the client apparatus 200 is input from the control unit 101, the communication unit 103 transmits the input information to the client apparatus 200, and outputs information from the client apparatus 200 received via the communication network N to the control unit 101.

The operation unit 104 includes an input interface such as a keyboard and a mouse, and receives an operation by a user. The display unit 105 includes a liquid crystal display device and the like, and displays information to be notified to the user. In the present embodiment, the server device 100 is configured to include the operation unit 104 and the display unit 105, but the operation unit 104 and the display unit 105 are not essential, and may be configured to receive an operation by a computer connected to the outside of the server device 100 and output information to be notified to the outside computer.

Fig. 4 is a block diagram illustrating the internal structure of the client apparatus 200. The client apparatus 200 is a personal computer, a smartphone, a tablet terminal, or the like, and includes a control unit 201, a storage unit 202, a communication unit 203, an operation unit 204, and a display unit 205.

The control unit 201 is constituted by a CPU, ROM, RAM, and the like. The CPU of the control unit 201 executes the control of the entire apparatus by expanding and executing various computer programs stored in the ROM or the storage unit 202 on the RAM.

The control unit 201 is not limited to the above configuration, and may be any processing circuit or arithmetic circuit including a plurality of CPUs, a multicore CPU, a microcomputer, or the like. The control unit 201 may have a function of a timer for measuring an elapsed time from when the measurement start instruction is given to when the measurement end instruction is given, a counter for counting the number of times, a clock for outputting date and time information, and the like.

The storage unit 202 is configured by a nonvolatile memory such as an eeprom (electronic Erasable Programmable read only memory), and stores various computer programs and data. The computer program stored in the storage unit 202 includes a general-purpose or dedicated application program for transmitting and receiving information to and from the server device 100. An example of a general-purpose application is a web browser. When the server apparatus 100 is accessed using a web browser, user authentication using a user ID and an authentication code is preferably performed, and communication between the server apparatus 100 and the client apparatus 200 may be permitted only when the user authentication is successful.

The communication unit 203 includes an interface for communicating with the server apparatus 100 via the communication network N. When information to be transmitted to the server apparatus 100 is input from the control unit 201, the communication unit 203 transmits the input information to the server apparatus 100 and outputs information from the server apparatus 100 received via the communication network N to the control unit 201.

The operation unit 204 includes an input interface such as a keyboard, a mouse, and a touch panel, and receives an operation by a user. The display unit 205 includes a liquid crystal display device and the like, and displays information to be notified to the user. In the present embodiment, the client apparatus 200 is configured to include the operation unit 204, but an input interface such as a keyboard or a mouse may be connected to the client apparatus 200.

A configuration for simulating a thermal phenomenon associated with an internal short circuit of the power storage device in the server apparatus 100 will be described below.

When simulating a thermal phenomenon associated with an internal short circuit of the power storage device, the server apparatus 100 receives, as simulation conditions, information related to a position where the internal short circuit occurs and a resistance value of a short-circuited portion. In this case, the server apparatus 100 may cause the display unit 205 of the client apparatus 200 to display an acceptance screen for accepting the simulation condition, and may accept the simulation condition through the displayed acceptance screen.

Fig. 5 is a schematic diagram showing an example of an acceptance screen for accepting a simulation condition. The reception screen 210 shown in fig. 5 includes: a selection column 211 for selecting a battery to be simulated; an input field 212 for inputting information related to the resistance value of the short-circuit portion; and a designation column 213 for designating a site where the internal short circuit occurs. A pull-down menu 211a is arranged in the selection field 211, and the type of battery to be simulated is received through the pull-down menu 211 a. An input box 212a is arranged in the input field 212, and receives input of a resistance value by, for example, numeric value input using the operation unit 204. In the designation field 213, a schematic perspective view of the power storage device (cell) and an icon 213a showing the occurrence location of the internal short circuit are displayed in order to receive the occurrence location of the internal short circuit. Alternatively, a perspective view of the module, group or domain may be displayed, and the short-circuit portion may be received in the displayed view. The reception screen 210 receives the occurrence location of the internal short circuit by a moving operation (drag operation) using the icon 213a of the operation unit 204.

When the send button 214 is operated on the reception screen 210, the input simulation conditions (information on the battery, information on the resistance value of the short-circuited portion, and the occurrence location of the internal short circuit) are sent from the client apparatus 200 to the server apparatus 100. The server apparatus 100 performs a simulation of the power storage device based on the simulation conditions transmitted from the client apparatus 200.

Hereinafter, a method of simulating the power storage device will be described.

Fig. 6 is a schematic explanatory view for explaining the simulation method. The server apparatus 100 according to the present embodiment simulates the operation of the power storage device based on joule heat generation and a heat generation reaction due to material decomposition. In addition, the heat generation may include enthalpy reaction heat (reversible reaction heat) and electrochemical reaction heat (irreversible reaction heat) associated with the electrochemical reaction.

For the electrochemical reaction, the server device 100 can use, for example, a Newman model. The Newman model is an electrochemical model that assumes a close arrangement of spheres of a single diameter that are homogeneous in the electrodes of the positive and negative electrodes. The Newman model is described by Nernst-Planck equation, charge storage equation, diffusion equation, Butler-Volmer equation, and Nernst equation described below.

The Nernst-Planck formula is an equation for solving the electrolyte, the ion electrophoresis in the porous electrode, and the ion diffusion, and is represented by the following formula. With respect to various parameters shown in the following equations 1 to 4, values in the bulk and values in the porous body can be appropriately converted as a function of the porosity of the constituent material.

[ mathematical formula 1]

Here, i_lIs liquid phase current density (A/m)²)，σ_l，effIs a liquid phase conductivity (S/m),is the liquid phase potential (V), R is the gas constant (J/(K.mol)), T is the temperature (K), F is the Faraday constant (C/mol), F is the activity coefficient, C_lIs the ion concentration (mol/m) of the electrolyte³) T + is the cation transference number, i_totReaction Current Density per volume (A/m)³)。

The charge storage formula is a formula representing electron conduction in the active material and the collector foil, and is represented by the following formula.

[ mathematical formula 2]

In this case, the amount of the solvent to be used,is a solid phase potential (V), σ_sIs solid phase conductivity (S/m), i_sIs in solid phase and has a current density (A/m)²)，i_totReaction Current Density per volume (A/m)³)。

The diffusion equation is an equation representing diffusion of the active material in the active particles, and is represented by the following formula.

[ mathematical formula 3]

Here, C_sIs the active substance concentration (mol/m) in the solid phase³) T is timeEngraving(s), D_sIs the diffusion coefficient (m) in the solid phase²/s)。

The Butler-Volmer formula is a formula representing an activation overvoltage in a charge transfer reaction occurring at an interface between a solid phase and a liquid phase, and the Nernst formula is a formula defining an open circuit potential, and is represented by the following formula.

[ mathematical formula 4]

η＝φ_s-φ_l-E_eq

Here, i_iocTo reflect the current density (A/m)²)，i₀For exchanging the current density (A/m)²)，α_a、α_cEta is the activation overvoltage (V), E_eqTo balance the potentials (V), E₀Is a standard equilibrium potential (V), a_oxAs oxidant concentration (mol/m)³)，a_redIs the concentration (mol/m) of the reducing agent³). Exchange current density i₀For example, it can be defined as a function of the ion concentration of the electrolyte and the concentration of the active material. Instead of the theoretical formula described in equation 4, a numerical value based on the experimental result may be used. For example, in the open circuit potential of the lithium ion secondary battery, measured data of the state of charge (SOC) and the open circuit potential (OCP or OCV) may be used instead of the Nernst equation.

Equation 5 represents a relational expression between the active material concentration in the solid phase on the surface of the active particle and the active material flux involved in the charge transfer reaction. r is₀Denotes the radius (m), J of the active particle_sIs flux (mol/m) of active substance²s). In other words, J_sIs the amount of active material per unit area per unit time that disappears by the charge transfer reaction.

[ math figure 5]

Equation 6 is the flux J for the active substance_sWith reaction current density i_locThe relationship (c) is described in the following equation.

[ mathematical formula 6]

i_loc＝zFJ_s

Equation 7 is for the reaction current density i_locAnd reaction current density per unit volume i_totThe relationship (c) is described in the following equation.

[ math figure 7]

i_tot＝S_vi_loc

In the present embodiment, a Newman model is shown as an example of a model representing an electrochemical phenomenon of an electric storage device. Instead, a single particle model in which an electrode is expressed by a single active particle, a polynomial model in which an open-circuit potential and an internal resistance represented by an NTGK model are expressed as functions of temperature and a state of charge (SOC), or an equivalent circuit model may be used. The single particle model is described in detail in non-patent literature, "Cycle Life Modeling of Lithium-Ion Batteries, Gang Ning and Branko N.Popov, Journal of The Electrochemical Society, 151(10) A1584-A1591 (2004)".

Next, the exothermic reaction caused by the decomposition of the material will be described. It is known that substances constituting an electricity storage device start a reaction such as decomposition of the material due to temperature rise. For example, in a lithium ion battery, when the temperature of the positive electrode material and the negative electrode material reaches about 200 to 300 ℃, the materials start to decompose and generate gas together with heat. In order to express the reaction rate having such temperature dependence, the reaction can be expressed by the arrhenius reaction formula below.

[ mathematical formula 8]

Q＝ρH_pr

Where r is the reaction rate (1/s), k₀Is a reaction rate constant (1/s), E_aThe activation energy (J/mol), R is a gas constant (J/(K. mol)), T is a temperature (K), and x is_fFor the reactivity, p, q, C₀Is a constant. Q is (W/m)³) ρ is the density (kg/m)³)，H_pIs the heat of reaction (J/kg).

When an internal short circuit occurs in the power storage device, a current flows from the entire power storage device to the short-circuited portion. Joule heat is generated by the current accompanying the internal short circuit. The exothermic reaction such as decomposition of the material proceeds by the generation of joule heat. When the temperature rises due to this heat generation reaction, the resistance changes, and therefore the magnitude of the current flowing into the short-circuited portion also changes. As described above, joule heating and material decomposition heating reactions are not independent physical phenomena, but proceed in association with each other via physical phenomena such as heat transfer.

Therefore, the server apparatus 100 according to the present embodiment analyzes the heat generation reaction accompanying material decomposition in combination with joule heat generation, and simulates a thermal phenomenon from the power storage device to the outside, for example, in consideration of a change in resistance due to temperature rise.

The following describes operations of the server apparatus 100 and the client apparatus 200.

Fig. 7 is a flowchart illustrating a procedure of processing performed by the server apparatus 100 and the client apparatus 200. The control unit 201 of the client apparatus 200 receives data for a display screen transmitted from the server apparatus 100 after the user authentication, and displays an acceptance screen 210 for accepting the simulation condition on the display unit 205 (step S101). The control unit 201 receives the simulation condition through the reception screen 210 displayed on the display unit 205 (step S102). Specifically, the control unit 201 receives selection of the type of the battery, information related to the resistance value of the short-circuit portion in the internal short circuit, and the occurrence location of the internal short circuit.

Next, the control unit 201 determines whether or not the transmission instruction of the simulation condition is received (step S103). When the transmission button 214 is operated on the reception screen 210 shown in fig. 5, the control unit 201 determines that the transmission instruction is received. When the transmission instruction is not received (no in S103), the control unit 201 waits until the transmission instruction is received.

When determining that the transmission instruction has been received (yes in S103), the control unit 201 transmits the simulation condition received in step S102 from the communication unit 203 to the server apparatus 100 (step S104).

The server apparatus 100 receives the simulation condition transmitted from the client apparatus 200 via the communication unit 103 (step S105). The control unit 101 of the server apparatus 100 executes a simulation based on the condition received by the communication unit 103 (step S106). At this time, the control unit 101 simulates a thermal phenomenon of the power storage device by executing a simulation program corresponding to the operation of the simulation target. The simulation conditions input by the user are applied when the simulation program is executed.

When an internal short circuit occurs in the power storage device, a current flows from the entire power storage device to the short-circuited portion. Joule heat is generated by the current accompanying the internal short circuit. The heat generation reaction such as material decomposition proceeds by the generation of joule heat. The control unit 101 combines the joule heat reaction with the heat generation reaction by material decomposition, calculates the electromotive force and internal resistance in the electric storage device by a Newman model, for example, and calculates the reaction rate in the heat generation reaction by an arrhenius type reaction equation shown in mathematical formula 5. As described above, the control unit 101 can perform current calculation in consideration of the change in resistance due to temperature rise, and can simulate a thermal phenomenon in the power storage device in association with a phenomenon in which energization is stopped due to temperature rise or a material generates heat due to a decomposition reaction of a material due to the progress of a heat generation reaction. For example, it is also possible to assume that the material decomposition reaction proceeds to a certain extent, and the electric conduction is stopped because the electric conductivity is lost.

When the simulation is completed, the control unit 101 transmits the simulation result to the client apparatus 200 via the communication unit 103 (step S107). The simulation result transmitted in step S107 may be numerical data, or may be a graph, contour map, moving image, or the like generated from numerical data. The simulation result transmitted in step S107 may be a mathematical model obtained as a result of the simulation. The mathematical model is not a simple theoretical model, but a model obtained by performing simulation on a selected power storage device and adjusting various parameters. The mathematical model is provided in the form of library, module, or the like used in commercially available numerical analysis software or programming languages, such as MATLAB (registered trademark), Amesim (registered trademark), Twin Builder (registered trademark), MATLAB & Simulink (registered trademark), simlorer (registered trademark), ANSYS (registered trademark), Abaqus (registered trademark), Modelica (registered trademark), VHDL-AMS (registered trademark), C-speech, C + +, Java (registered trademark), or the like.

The client apparatus 200 receives the simulation result transmitted from the server apparatus 100 via the communication unit 203 (step S108). The control unit 201 of the client apparatus 200 causes the display unit 205 to display the received simulation result (step S109).

As described above, in the present embodiment, the server apparatus 100 can simulate a thermal phenomenon that occurs from the power storage device to the outside in consideration of the heat generation reaction and the joule heat generation due to the material decomposition of the power storage device. Even if the user is unfamiliar with the physical phenomenon in the electric storage device, the user can acquire the simulation result regarding the thermal phenomenon of the electric storage device without complicated simulation setting by inputting the type of the electric storage device, the position where the internal short circuit occurs, and the information regarding the resistance value of the short circuit portion from the client apparatus 200.

In the present embodiment, the configuration in which the thermal phenomenon in the case where the internal short circuit occurs in the power storage device is simulated has been described, but the thermal phenomenon in the case where the external short circuit occurs can also be simulated. In this case, the server apparatus 100 receives, via the client apparatus 200, an input of information related to a resistance value in an external short circuit (for example, a numerical value directly indicating the resistance value in the external short circuit; instead, information indirectly indicating the resistance value in the external short circuit (specifically, information that causes the occurrence of an external short circuit (an external short circuit between the positive electrode terminal and the negative electrode terminal by a tool such as a wrench, a short circuit outside the battery due to insulation (covering) damage of the wiring, a short circuit outside the battery due to a collision, an external short circuit due to a switch failure, or the like))) and simulates a thermal phenomenon based on the information related to the resistance value of the received external short circuit. Specifically, the control unit 101 of the server device 100 calculates the current flowing from the positive terminal to the negative terminal of the battery by an external short circuit. The control unit 101 can simulate the electric storage device and a thermal phenomenon occurring from the electric storage device to the outside by analyzing the joule heat associated with the electric current and the exothermic reaction such as decomposition of the material due to the generation of the joule heat in combination.

(embodiment mode 2)

In embodiment 2, a thermal phenomenon in the case where the power storage device is heated from the outside is simulated. The power storage device may be heated due to an abnormality in the surrounding environment (e.g., when a mobile body on which the power storage device is mounted collides, or when a cooling device in the power storage device facility fails). There is a need to simulate in advance what operation the power storage device exhibits in such a situation and what thermal phenomenon appears to the outside.

When the electric storage device has a rectangular parallelepiped shape (prismatic cell), the operation may be different depending on whether the side surface or the upper surface of the electric storage device is heated. The same applies to the case where the power storage device is a pouch cell or a cylindrical cell. In a system (battery pack) including a plurality of power storage devices, the power storage device located inside and the power storage device located outside may operate differently due to a difference in distance from a heat source or an influence of heat accumulation. Therefore, in the simulation, the heating portion that heats the power storage device by the heat source is received.

The server apparatus 100 receives simulation conditions including a heating location, a heat amount, and an ambient temperature when the power storage device is externally heated, via the client apparatus 200. The heating locations may also be accepted via a user interface including a graphical display similar to fig. 5. The server apparatus 100 simulates a thermal phenomenon based on the received simulation conditions. Specifically, the control unit 101 of the server apparatus 100 can simulate a thermal phenomenon occurring from the power storage device to the outside by analyzing a material decomposition reaction by heat supplied from the outside using an equation of an arrhenius-type reaction.

(embodiment mode 3)

In embodiment 3, a configuration in which a simulation is performed for an internal short circuit of a wound unit (a unit that houses a wound electrode body in a container) will be described.

Fig. 8 is an explanatory diagram for explaining the components of the power storage device 1 according to embodiment 3. The electric storage device 1 according to embodiment 3 includes a wound electrode body 10v, a positive electrode terminal 11, a positive electrode collector 11a, a negative electrode terminal 12, and a negative electrode collector 12a, and is housed in a hollow rectangular parallelepiped container 20, for example. The electrode assembly 10v is configured by, for example, disposing a separator made of a porous resin film between a strip-shaped negative electrode and a strip-shaped positive electrode disposed offset in the width direction of the negative electrode, and winding them, thereby forming a wound electrode assembly 10v, wherein the strip-shaped negative electrode has a negative electrode active material provided on a negative electrode current collector foil made of a copper foil, and the strip-shaped positive electrode has a positive electrode active material provided on a positive electrode current collector foil made of an aluminum foil.

The positive electrode collector 11a electrically connects the positive electrode terminal 11 to the positive electrode (active material non-formation portion, positive electrode current collector foil) of the electrode assembly 10 v. The negative electrode current collector 12a electrically connects the negative electrode terminal 12 to the negative electrode (active material non-formation portion, negative electrode current collector foil) of the electrode assembly 10 v. The positive electrode collector 11a is electrically connected to the positive electrode of the electrode body 10v at least 1 point, and the negative electrode collector 12a is electrically connected to the negative electrode of the electrode body 10v at least 1 point. Various types of positions of the positive electrode collector 11a and the negative electrode collector 12a can be considered within a range where the electrical connection between the positive electrode and the negative electrode of the electrode assembly 10v is not changed. In the example of fig. 8, the winding center of the electrode body 10v is oriented in the X-axis direction on the drawing. Alternatively, the winding center of the electrode body 10v may be oriented in the Y-axis direction or the Z-axis direction of the paper.

Fig. 9 shows an electrode body of the type having electrode tabs of a wound unit. The negative electrode is provided with a plurality of negative electrode tabs 12b (active material non-forming portions) at intervals on one side of a strip-shaped negative electrode current collector foil extending in the longitudinal direction. The positive electrode is provided with a plurality of positive electrode tabs 11b (active material non-forming portions) at intervals on one side of a strip-shaped positive electrode current collector foil extending in the longitudinal direction. A separator is disposed between the negative electrode and the positive electrode, and the wound electrode body is formed by winding them. The plurality of negative electrode tabs 12b and the plurality of positive electrode tabs 11b are bundled and electrically connected to a negative electrode current collector and a positive electrode current collector, not shown.

Although not shown, in the laminated unit (unit in which the laminated electrode body in which a plurality of sheet-shaped current collecting foils are laminated is housed in a container), only the electrodes other than the short-circuited layer are short-circuited via the tab at the time of short-circuiting. In contrast, in the wound unit, there are two types of current flowing from the short-circuit layer through the tab (positive tab 11b or negative tab 12b) and current flowing from the bent portion located in the middle of the adjacent electrode. Therefore, the calculation method used in the lamination unit cannot be used in the winding unit.

Therefore, in the present embodiment, the short-circuit current is calculated by assuming that the wound electrode body is in a state of being expanded and expanded. Typical examples of the simulation of the internal short circuit include a through short circuit typified by a nail penetration test and a partial short circuit typified by a nickel sheet mixing test. The details will be described below.

In the present embodiment, a case where the short-circuit current in both the through short circuit and the partial short circuit is calculated in the shape of the unwound wound electrode assembly will be described in detail.

Fig. 10 is an explanatory view illustrating a portion where a short-circuited portion appears under a penetration short-circuit in the wound electrode assembly shown in fig. 9. Fig. 10 shows a shape and a size of the wound electrode assembly 10, the positive electrode tab 11b, and the negative electrode tab 12b (shown by dotted lines) in a modified form for the sake of explanation. Fig. 10 shows an example in which a conductor such as a nail penetrates through the wound electrode body in a wound unit wound 3 times, that is, in all 6 layers. The developed model is a three-dimensional model in which the positive electrode current collector foil, the positive electrode active material, the separator, the negative electrode active material, and the negative electrode current collector foil are arranged from the front side toward the back side of the paper surface. The positive electrode tab 11b is present on the same plane as the positive electrode current collector foil (at the same position in the depth direction), and is electrically connected to the strip-shaped positive electrode current collector foil of the developed electrode body 10 at 6 locations. Similarly, the negative electrode tab 12b is present in the same plane as the negative electrode current collector foil (at the same position in the depth direction), and is located at 6 places in the strip-shaped negative electrode of the developed electrode assembly 10The collector foils are electrically connected. The positive electrode tab 11b and the negative electrode tab 12b are not directly electrically connected. The portion connecting the plurality of positive electrode tabs 11b (the plurality of negative electrode tabs 12b) in the lateral direction of the paper surface is a virtual conductive path showing the electrical connection of the plurality of tabs by the bundling of the tabs as shown in fig. 9. As shown in fig. 10, in the case of a through short, when the wound electrode body is unwound, a plurality of short-circuited portions appear in the longitudinal direction of the cell. In the present embodiment, by calculating the current flowing from the tab (positive tab 11b or negative tab 12b) or the adjacent electrode to each short-circuited portion, the short-circuit phenomenon occurring inside the winding unit can be appropriately expressed, and the thermal phenomenon occurring from the winding unit to the outside can be accurately simulated. The wound electrode body includes a portion in which the electrode is bent, which is referred to as a bent portion 10a shown in fig. 10, but physical properties (for example, electrical conductivity, porosity, liquid phase conductivity, and the like) different from those of the flat portion 10b may be provided at this portion. As for a virtual conductive path showing electrical connection by binding of the tab, an appropriate physical property value (for example, an electronic conductivity of 1.0 × 10) may be given in consideration of the ease of convergence of calculation¹⁰S/m, etc.).

The example of the through short circuit shown in fig. 10 shows a case where a short circuit occurs in the center of the wound electrode assembly, but if the simulation method is used, the short circuit position is not limited to the center of the wound electrode assembly, and can be calculated by the same modeling method even in the vicinity of the tab or the vicinity of the bent portion 10a, for example.

Fig. 11 is an explanatory view explaining the appearance of the short-circuit portion in the wound electrode assembly under the partial short-circuit. Fig. 11 shows a shape and a size of the wound electrode assembly 10, the positive electrode tab 11b, and the negative electrode tab 12b (shown by dotted lines) in a modified form for the purpose of illustration. The example of fig. 11 shows a state in which a conductor such as a nickel sheet short-circuits a part of the wound electrode body. The developed model is a three-dimensional model in which the positive electrode current collector foil, the positive electrode active material, the separator, the negative electrode active material, and the negative electrode current collector foil are arranged from the front side toward the back side of the paper surface. In this case, when the wound electrode body is unwound, 1 short-circuited portion occurs in the length direction of the cell. In the present embodiment, the slave tab (positive electrode tab 11 b) is calculatedOr negative electrode tab 12b) or the adjacent electrode to each short-circuit portion, the short-circuit phenomenon occurring inside the winding unit can be appropriately represented, and the thermal phenomenon occurring from the winding unit to the outside can be accurately simulated. The wound electrode body includes a portion in which the electrode is bent, which is referred to as a bent portion 10a shown in fig. 11, but physical properties (for example, electrical conductivity, porosity, liquid phase conductivity, and the like) different from those of the flat portion 10b may be provided at this portion. As for a virtual conductive path showing electrical connection by binding of the tab, an appropriate physical property value (for example, an electronic conductivity of 1.0 × 10) may be given in consideration of the ease of convergence of calculation¹⁰S/m, etc.).

The example of the partial short circuit shown in fig. 11 shows a case where a short circuit occurs in the outermost peripheral layer in the center of the wound electrode body, but if this simulation method is used, the short circuit position is not limited to the center of the wound electrode body, and the outermost peripheral layer is not necessarily required. Further, there may be a plurality of short-circuit positions. For example, in the case of short-circuiting of the wound layer 2, even in the case where nickel pieces are mixed in a plurality of portions, the calculation can be performed by the same modeling method by performing the simulation in the corresponding developed shape.

The above description has been made on the method for calculating the short-circuit current, but the heat transfer and heat generation reaction may be performed in accordance with the actual shape. That is, it is not necessary to virtually expand the plane as described above.

As described in the present embodiment, the safety simulation of the wound unit is performed by combining the simulation of the short-circuit current in the shape in which the wound electrode body is spread and the simulation of the heat transfer and the heat generation reaction according to the shape of the real object, and thus calculation for more accurately representing the real object can be performed.

(embodiment mode 4)

In embodiment 4, the heat generation rate in the material decomposition reaction of the electric storage device is calculated.

In the server apparatus 100 according to embodiment 4, an arrhenius-type reaction equation of the above-described equation 5 known as a Dahn model is used as an equation describing the exothermic reaction of the material decomposition reaction. Control unit of server device 100101 calculating the reaction rate x using an arrhenius type reaction equation of mathematical formula 5_f。

The reaction rate x is calculated by using an Arrhenius-type reaction formula of mathematical formula 5_fWhen the heat generation density Q is high, the reaction rate constant k is required₀Activating energy E_aConstants p, q, C₀The value of (c). In the method disclosed in japanese patent application laid-open No. 2006-10648, the graph of the relationship between temperature and heat generation amount obtained by the differential thermal analysis is converted into the relationship between time and heat generation amount, and then fitting is performed to obtain the above parameters. In contrast, the present embodiment discloses a method of acquiring each parameter by directly using a graph showing a relationship between temperature and a heat generation amount obtained by differential thermal analysis.

First, the control unit 101 obtains a temperature-heat generation amount relational expression by fitting the temperature-heat generation amount data obtained by the differential thermal analysis with a lorentz function, a gaussian function, or the like. A fitting based on a lorentzian function or a gaussian function is performed using suitable optimization tools.

Next, the control unit 101 converts the heat generation density q (t) obtained as a function of temperature into the heat generation density q (t) expressed as a function of time using an equation of the differential chain law shown in the following expression. In the following mathematical formula 6, a factor represented by a time partial differential of the temperature T is calculated in the process of calculation.

[ mathematical formula 9]

As described above, in the present embodiment, the heat generation density q (t) expressed as a function of time is calculated by directly using the graph of the relationship between the temperature and the amount of heat generation, and therefore, it is possible to save the labor for converting the relationship between the temperature and the amount of heat generation into the relationship between the time and the amount of heat generation.

(embodiment 5)

In embodiment 5, a method for simulating gas generation will be described.

If an event such as an internal short circuit occurs in the electric storage device and the safety mechanism does not function properly, the material decomposition reaction may proceed and gas may be ejected from the inside of the electric storage device. For example, in the case of a liquid-type lithium ion battery, oxygen desorbed from the positive electrode active material by temperature increase reacts with the electrolyte to generate gas. Generally, a housing of an electric storage device is provided with a safety mechanism such as a rupture valve that operates under pressure, and the rupture valve opens when the internal pressure rises due to gas generated inside the housing, and the gas is discharged to the outside.

Since this gas has a high temperature, it causes burning in the adjacent cells and burning of the structural members. Further, since the gas discharged from the power storage device sometimes includes harmful gas such as carbon monoxide, prediction of the ambient temperature in consideration of the temperature, flow rate, and gas concentration is important in designing safety of the power storage device and the entire product including the power storage device.

Therefore, the server device 100 according to embodiment 5 simulates gas generation based on the exothermic reaction of the material decomposition reaction. By calculating various amounts involved in the generation of gas, for example, by serving as boundary conditions for thermal fluid simulation, it is possible to apply to thermal design and safety design of electric vehicles, power generation equipment, and the like.

As reactions involved in the generation of gas, for example, gas generation by oxygen desorbed from the positive electrode active material and the electrolyte, and gas generation by thermal decomposition of an organic auxiliary agent contained in the electrode are known. For convenience, numbers 1, 2, …, i, … are assigned to these reactions. In practice, it is difficult to analyze and examine in detail the basic reaction process associated with the gas generation of the battery. Therefore, a method of separating the reaction by referring to a differential thermal analysis (DSC) chart, a result of gas amount measurement, or the like may be used.

The control part 101 passes V_tot＝∑v_ix_fiCalculating the total positive gas volume V_tot. Here, v_iIs the standard volume, x, of the gas produced in the case of complete reaction i_fiIs the reaction rate of reaction i.

Control unit 101 calculates the power storage deviceThe pressure inside the frame. It is assumed that the gas inside the frame is an ideal gas. The control part 101 adjusts the internal pressure P of the cell_inIs calculated as P_in＝P₀×(V_tot/V_gap)×(T/T₀). Here, P is₀The initial internal pressure (Pa) of the battery device case is usually 1 (atm). V_gapVolume (m) of gas existing region inside the housing of the electric storage device³) T is the gas temperature (K), T₀The reference temperature (K) is shown.

The rupture valve of the power storage device is configured to satisfy P_th＜P_inIs opened in case of the condition(s). Here, P is_thIs the threshold value of the internal pressure at which the rupture valve opens. After the burst valve is opened, gas generated by the reaction is discharged from the opened burst valve to the outside.

The control part 101 passes q_norm，tot＝∑v_ir_iTo calculate the positive gas generation volume velocity q_norm，tot. Here, q is_norm，totFor positive gas generation volume velocity (m)³/s)，v_iIs the volume (m) of the positive gas produced by the ith reaction³)，r_iThe reaction rate (1/s), r, of the ith reaction_i＝(d/dt)x_fiI.e. the time differential of the reaction rate in reaction i.

The area of the opening of the rupture valve is S (m)²) At the time, the velocity of the gas ejected from the opening of the rupture valve passes through v in consideration of thermal expansion_vent＝q_norm，tot/S×(T/T₀) To calculate. Here, v_ventIs the gas velocity (m/s) of the gas ejected from the opening of the rupture valve. This value may be used as a boundary condition of the velocity of the gas discharged from the opening of the rupture valve as it is, or a parabolic velocity distribution may be given. When a turbulent model such as a k-epsilon model or a k-omega model is used as a calculation model of a fluid, a value in which convergence is taken into consideration may be provided for a term specific to the turbulent model such as turbulent energy or a turbulent extinction ratio.

The control unit 101 also calculates the heat generation rate based on the heat generation reaction together with the gas ejection rate. The method of calculating the heat generation rate may be the same as that described in embodiment 1.

The heat generated by the exothermic reaction is appropriately proportioned to the ejected gas and the electricity storage device. As the proportional distribution ratio at this time, as an example, a method of proportionally distributing the gas and the electricity storage device at a ratio of heat capacities thereof on the assumption that the gas and the electricity storage device instantaneously reach a thermal equilibrium may be adopted. Alternatively, a proportional distribution ratio of the heat to the ejected gas and the electricity storage device may be given in a manner matching the experimental results.

The disclosed embodiments are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims, and includes all modifications within the meaning and range equivalent to the scope of the claims.

For example, although embodiments 1 to 5 have been described with a single power storage device as an example, simulation can be performed also for a system (such as a battery pack) including a plurality of power storage devices. Fig. 12 is a schematic view showing a system (battery pack) including a plurality of power storage devices, and fig. 13 is a graphic display (moving image display) for visualizing a state where the plurality of power storage devices discharge gas in a chain manner in the system of fig. 12. For example, the following chain events of gas ejection can also be simulated: the temperature of the electric storage device a is raised by a factor such as an internal short circuit, and the gas discharged from the electric storage device a raises the temperature of the electric storage device B, and the electric storage device B discharges the gas in a chain (see fig. 13).

Briefly, the simulation method is as follows:

1) receiving a simulation condition concerning a first power storage device, calculating a short-circuit current based on the received simulation condition, simulating a thermal phenomenon from the first power storage device to the outside,

2) simulating a thermal phenomenon from the second power storage device to the outside accompanying heating of the second power storage device caused by the thermal phenomenon from the first power storage device to the outside.

As another embodiment, the following simulation method is also considered:

1) receiving a simulation condition concerning a first power storage device, the simulation condition including a heating portion when the first power storage device is heated from outside, and simulating a thermal phenomenon from the first power storage device to outside accompanying heating of the first power storage device based on the received simulation condition,

2) simulating a thermal phenomenon from the second power storage device to the outside accompanying heating of the second power storage device caused by the thermal phenomenon from the first power storage device to the outside.

These simulation methods can also be realized as a simulation apparatus or a computer program.

By these simulation methods, the situation of prolonged burning can be visualized for a system including a plurality of power storage devices. It is possible to grasp which power storage device exhibits what thermal phenomenon in time series, which power storage device is associated with which power storage device to exhibit thermal phenomenon, and the like.

In the present specification, the simulation object is described mainly focusing on the thermal influence of the electric storage device on the outside, but may focus on the inside of the electric storage device. For example, the gas discharged from the power storage device has an effect of suppressing the temperature rise of the power storage device. Therefore, the state of the inside of the power storage device can be calculated with exactly the same idea.

Various effective utilization methods can be considered in the security simulation described in the present specification. For example, when the power storage device is exposed to a desired thermal condition, whether or not the rupture valve is open can be determined by the simulation method of the present application, based on the generation of gas and the increase in internal pressure caused by the decomposition of the material. The simulation method of the present application can be effectively used even in a study of whether or not ignition of a peripheral power storage device is caused, assuming that the burst valve is opened and gas is ejected. Further, for example, the effects of heat insulating materials, refractories, and the like for preventing the ignition can be confirmed by calculation, and this becomes a means for strongly advancing product design based on the concept of model development.

In embodiment 1, a mode in which simulation is performed by communication between a server and a client is exemplified, but a mode in which a server administrator provides a simulation program to a client user by a method of a storage medium such as a DVD-ROM, and simulation is performed locally at a client terminal may be used. As the providing method, a download form via communication is possible.

Description of the symbols

100 a server device;

101 a control unit;

102 a storage section;

103 a communication unit;

104 an operation section;

105 a display unit;

200 a client device;

201 a control unit;

202 a storage section;

203 a communication unit;

204 an operation part;

205 a display section;

n communication network.