CN111448450A - Method and apparatus for evaluating thermal stability of battery - Google Patents
Method and apparatus for evaluating thermal stability of battery Download PDFInfo
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- CN111448450A CN111448450A CN201780097577.0A CN201780097577A CN111448450A CN 111448450 A CN111448450 A CN 111448450A CN 201780097577 A CN201780097577 A CN 201780097577A CN 111448450 A CN111448450 A CN 111448450A
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- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000010438 heat treatment Methods 0.000 claims abstract description 172
- 238000006243 chemical reaction Methods 0.000 claims abstract description 123
- 238000005259 measurement Methods 0.000 claims abstract description 112
- 238000007306 functionalization reaction Methods 0.000 claims description 47
- 238000011156 evaluation Methods 0.000 claims description 35
- 238000009529 body temperature measurement Methods 0.000 claims description 10
- 238000012935 Averaging Methods 0.000 claims description 8
- 125000000524 functional group Chemical group 0.000 claims 4
- 238000012360 testing method Methods 0.000 abstract description 16
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- 230000006870 function Effects 0.000 description 37
- 239000000376 reactant Substances 0.000 description 16
- 238000012545 processing Methods 0.000 description 8
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- 230000000630 rising effect Effects 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- 238000007707 calorimetry Methods 0.000 description 4
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000005001 laminate film Substances 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910000652 nickel hydride Inorganic materials 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/04—Construction or manufacture in general
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Provided is a method for evaluating thermal stability of a battery, which can more accurately predict the behavior of an exothermic reaction of the battery by improving the estimation accuracy of parameters of an exothermic reaction model formula. The method for evaluating thermal stability of a battery comprises: a measurement step of measuring a time lapse of the temperature of the battery by performing an acceleration rate heat measurement test including a heating step (S1), a standby step (S2), a search step (S3), and a heat release step (S4) using an adiabatic calorimeter; and a parameter estimation step (S6) for estimating parameters of the exothermic reaction model equation of the battery by using the temperature rise rate of the battery determined from the measurement data of at least the search step and the exothermic step.
Description
Technical Field
The present invention relates to a method and an apparatus for evaluating thermal stability of a battery.
Background
When a battery becomes abnormal, such as overcharging, overdischarging, external short-circuiting, or internal short-circuiting, an exothermic reaction may occur in which a power generating element (reactant) constituting the battery is thermally decomposed and releases heat. By predicting the behavior of the exothermic reaction of the battery, a battery with higher reliability can be designed.
In order to predict the behavior of the exothermic reaction of the battery, it is effective to model the exothermic behavior of the battery. For example, non-patent document 1 below discloses a thermal stability evaluation method for predicting the behavior of the exothermic reaction of a battery by estimating parameters of an exothermic reaction model equation by performing an acceleration Rate calorimetric test using ARC (accelerated Rate Calorimeter, registered trademark) which is an adiabatic Calorimeter. In the accelerated rate calorimetry test, the temperature of the battery is increased by external heating in order to accelerate the exothermic reaction of the battery. The temperature increase rate of the battery can be determined from the slope of a graph obtained by measuring the time course of the temperature increase of the battery. The obtained temperature increase rate of the battery can be used to estimate parameters of the exothermic reaction model equation of the battery.
Documents of the prior art
Non-patent document
Non-patent document 1: townsend, D.I., and Tou, J.C., Thermal Hazard Evaluation by and evaluating Rate Calorimeter, Thermochimica Acta, 37(1980)1-30.
Disclosure of Invention
Problems to be solved by the invention
In the above non-patent document 1, when the temperature increase rate of the battery becomes equal to or higher than the threshold value, it is determined that the exothermic reaction of the battery has started. Therefore, the behavior of the exothermic reaction of the battery is predicted using only a graph of the time course of the temperature rise of the battery from the time point at which the temperature rise speed of the battery becomes equal to or more than the threshold value.
However, there are the following periods: a period during which the temperature increase rate becomes greater than 0 (zero) before the temperature increase rate of the battery becomes equal to or greater than the threshold value. That is, the battery undergoes an exothermic reaction before the rate of temperature rise of the battery reaches a threshold value. In the above non-patent document 1, there are the following problems: since the exothermic reaction until the temperature increase rate of the battery reaches the threshold value is ignored, the estimation accuracy of the parameter of the exothermic reaction model equation is poor.
The purpose of the present invention is to provide a method and device for evaluating thermal stability of a battery, which can predict the behavior of an exothermic reaction of the battery more accurately by improving the accuracy of estimation of parameters of an exothermic reaction model formula.
Means for solving the problems
The method for evaluating thermal stability of a battery according to the present invention for achieving the above object uses an adiabatic calorimeter having a storage container for storing a battery. The method for evaluating thermal stability of a battery includes a first measurement step, a second measurement step, a third measurement step, and a parameter estimation step. In the first measurement step, a heating step of heating the internal temperature of the storage container to a predetermined temperature and a standby step of waiting for a predetermined time after the heating step are performed to measure a time passage of the temperature of the battery. In the second measurement step, after the first measurement step, a search step is performed for performing adiabatic control for bringing the battery into an adiabatic state to determine whether or not the temperature increase rate of the battery is equal to or greater than a threshold value, and the heating step, the standby step, and the search step are repeated until the temperature increase rate of the battery becomes equal to or greater than the threshold value to measure the time lapse of the temperature of the battery. In the third measurement step, when the temperature increase rate of the battery becomes equal to or greater than the threshold value, the heat release step for performing the adiabatic control until the end of the heat release reaction of the battery is performed, and the time passage of the temperature of the battery is measured. In the parameter estimation step, the parameter of the exothermic reaction model equation of the battery is estimated using the temperature increase rate of the battery obtained from the measurement data of at least the search step and the exothermic step.
The thermal stability evaluation device for a battery according to the present invention for achieving the above object includes an adiabatic calorimeter, a control unit, and a parameter estimation unit. The heat-insulating calorimeter is provided with a storage container for storing a battery, a heating unit for heating the interior of the storage container, a first temperature measuring unit for measuring the internal temperature of the storage container, and a second temperature measuring unit for measuring the temperature of the battery. The control part controls the work of the heat insulation calorimeter to be in the following modes: a heating mode for heating the inside temperature of the holding container to a predetermined temperature; a standby mode for waiting a predetermined time after the heating mode; a search mode for performing adiabatic control for setting the battery in an adiabatic state to determine whether or not a temperature increase rate of the battery is equal to or greater than a threshold value; and a heat radiation mode for repeating the heating mode, the standby mode, and the search mode until a temperature increase rate of the battery becomes a threshold value or more, and performing the adiabatic control until an exothermic reaction of the battery is completed when the temperature increase rate of the battery becomes the threshold value or more. The parameter estimation unit estimates a parameter of an exothermic reaction model equation of the battery using measurement data of a temperature increase rate of the battery obtained from measurement data of the second temperature measurement unit in at least the search mode and the heat release mode.
Drawings
Fig. 1 is a schematic diagram showing the overall structure of a thermal stability evaluation device for a battery according to an embodiment of the present invention.
Fig. 2 is a block diagram showing a schematic configuration of the thermal stability evaluation device of the battery shown in fig. 1.
Fig. 3 is a graph showing the time course of the temperature of the battery measured by the thermal stability evaluation device of the battery according to the embodiment of the present invention.
Fig. 4 is a flowchart illustrating a procedure of a method for evaluating thermal stability of a battery according to an embodiment of the present invention.
Fig. 5 is a flowchart showing a procedure of the functionalization process shown in fig. 4.
Fig. 6 is a partially enlarged graph of the second measurement step in the graph showing the time transition of the temperature of the battery shown in fig. 3.
Detailed Description
Embodiments of the present invention will be described below with reference to the drawings. The following description is not intended to limit the technical scope or meaning of the terms described in the claims. The dimensional ratios in the drawings are exaggerated for convenience of explanation and may be different from actual ratios.
The thermal stability evaluation device and the thermal stability evaluation method for a battery according to the present embodiment evaluate the thermal stability of a battery by estimating parameters of an exothermic reaction model equation of the battery using measurement data of an accelerated rate calorimetry test.
Here, the battery to be evaluated for thermal stability in the present embodiment is broadly defined to include a power device capable of storing electric power or supplying electric power. Specific examples of the battery include primary batteries such as lithium ion batteries, nickel hydride batteries, and lithium batteries, secondary batteries, and power generation batteries such as fuel cells. In the above, since the lithium ion secondary battery has a higher possibility of an internal short circuit due to the closer proximity of the positive electrode and the negative electrode than other batteries, the thermal stability can be appropriately evaluated by the thermal stability evaluation device for a battery and the thermal stability evaluation method for a battery according to the present embodiment.
First, the thermal stability evaluation device 10 of the battery according to the present embodiment will be described with reference to fig. 1 and 2.
< apparatus for evaluating thermal stability of Battery >
As shown in fig. 1, the thermal stability evaluation device 10 for a battery has an adiabatic calorimeter 100 and a control unit 200.
In the present embodiment, a coin cell (coin cell)1 for testing having the same material structure as that of a battery (actual battery cell) to be actually used is used as a battery for measurement. By using the coin-type battery cell 1 for testing, the thermal stability of the battery can be evaluated without trial production of an actual battery cell. This can significantly reduce the trial production cost of the actual battery cell, and can shorten the period required for evaluating the thermal stability of the battery. In the following description, the coin-type battery cell 1 for testing will be simply referred to as "battery 1".
(adiabatic calorimeter 100)
As shown in fig. 1, the heat-insulated calorimeter 100 includes a sample container 110 for housing a battery 1, a storage container 120 for storing the sample container 110, a heating unit 130 for heating the inside of the storage container 120 and the battery 1, and a temperature measuring unit 140. The adiabatic calorimeter 100 may also have a pressure sensor or the like for measuring the pressure inside the storage container 120.
The sample container 110 has a spherical portion 111 for accommodating the battery 1 and an introduction tube 112 for introducing the battery 1 into the spherical portion 111.
The holding container 120 is provided to surround the periphery of the sample container 110, and serves to insulate the inside of the sample container 110 from the outside.
The heating unit 130 includes a first heating unit 131 that heats the battery 1 in the sample container 110 and a second heating unit 132 that heats the inside of the storage container 120.
The first heating unit 131 is provided in the vicinity of the spherical portion 111 of the sample container 110. As the first heating section 131, for example, a known radiation Heater (Radiant Heater) can be used.
The second heating unit 132 heats the inside of the heat-insulated storage container 120. As the second heating section 132, for example, a known sleeve Heater (socket Heater) in which the heat radiating section 132a and the heat insulating material 132b are integrated can be used. The heat insulator 132b is composed of a side wall, an upper wall, and a lower wall provided so as to cover the entire inner surface of the inside of the storage container 120. The side walls, the upper wall, and the lower wall are provided with a plurality of heat radiating portions 132a, respectively. The heat radiating portion 132a heats the side wall, the upper wall, and the lower wall of the heat insulator 132b, and heats the environment inside the storage container 120 by heat conducted from the side wall, the upper wall, and the lower wall.
The temperature measuring unit 140 has a first temperature measuring unit 141 that measures the temperature of the battery 1 in the sample container 110, and a second temperature measuring unit 142 that measures the internal temperature of the storage container 120. As the temperature measuring unit 140, a known thermocouple can be used.
The first temperature measuring unit 141 measures the temperature of the battery 1, which changes due to self-heating caused by the exothermic reaction of the battery 1 by external heating by the heating unit 130.
The second temperature measuring unit 142 measures the internal temperature of the storage container 120. Specifically, the second temperature measuring unit 142 measures the temperature of at least 3 or more locations of the side wall, the upper wall, and the lower wall of the heat insulator 132b of the second heating unit 132. The second temperature measuring unit 142 detects an average value of the plurality of measured temperatures as the internal temperature (ambient temperature) of the storage container 120. The temperature of the side wall, the upper wall, and the lower wall is substantially equal to the internal temperature of the storage container 120.
(control unit 200)
As shown in fig. 2, the control unit 200 includes a control unit 210, a data generation unit 220, a storage unit 230, a display unit 240, an arithmetic processing unit 250, an input unit 260, and an evaluation unit 270.
The control unit 210 controls the heating unit 130 based on the measurement data of the temperature measurement unit 140. Specifically, the control unit 210 includes: a ROM (read only memory) that stores various programs and various data; and a CPU that controls each unit of the adiabatic calorimeter 100 according to a program stored in the ROM. The control unit 210 is electrically connected to the data generation unit 220, and acquires the measurement data of the temperature measurement unit 140 from the data generation unit 220. The control unit 210 is electrically connected to the heating unit 130 of the heat-insulating calorimeter 100, and transmits a control signal to the heating unit 130 to control the internal temperature in the sample container 110 and the temperature of the battery 1.
More specifically, the control unit 210 controls the heating unit 130 to switch between (a) the heating mode, (b) the standby mode, (c) the search mode, and (d) the heat release mode. The modes are explained below.
(a) The heating mode is a mode for heating the internal temperature of the holding container 120 to a predetermined temperature. Here, the "predetermined temperature" is a temperature at which the exothermic reaction of the battery 1 does not progress, and can be set to, for example, about 40 to 60 ℃. The control unit 210 mainly controls the second heating unit 132 to raise the internal temperature of the storage container 120. The control unit 210 can control each of the plurality of heat radiating units 132a of the second heating unit 132 independently, and uniformly heat the internal temperature of the storage container 120.
(b) The standby mode is a mode of waiting for a predetermined time (standby time) after the heating mode. Here, the "standby time" is the time taken until the internal temperature of the storage container 120 becomes stable and constant and the internal temperature of the storage container 120 and the temperature of the battery 1 become equal, and is a time determined in advance through experiments. The standby time can be set to, for example, about 5 minutes to 10 minutes. The control unit 210 mainly controls the second heating unit 132 to keep the internal temperature of the storage container 120 constant.
(c) The search mode is a mode in which adiabatic control is performed to put the battery 1 into an adiabatic state to determine whether or not the temperature increase rate of the battery 1 is equal to or greater than a threshold value. Here, the "heat-insulated state" refers to a heat equilibrium state in which heat does not move between the battery 1 and the surroundings of the battery 1 (the environment inside the storage container 120). In the adiabatic control, the internal temperature of the storage container 120 is set to be substantially the same as the temperature of the battery 1. The "substantially the same temperature" is not limited to the case where the internal temperature of the storage container 120 and the temperature of the battery 1 are completely the same temperature, and includes the case where the temperature difference between the internal temperature of the storage container 120 and the temperature of the battery 1 is within a predetermined range (for example, within 0.05 ℃).
The "threshold value" of the temperature increase rate of the battery 1 is preferably set to a value as small as possible, and can be set to, for example, about 0.02 ℃/min. In the present embodiment, the temperature rise of the battery 1 is measured at intervals of a predetermined time, and the temperature rise of the battery 1 is divided by the predetermined time, and the obtained value is used as the temperature rise rate of the battery 1. Here, the "predetermined time" for measuring the change in the rise temperature of the battery 1 can be appropriately adjusted according to the measurement resolution (sensitivity) of the thermocouple of the temperature measurement unit 140. As the measurement resolution of the thermocouple is higher, the minimum measurement unit of the measurement values that can be measured is smaller, and the temperature rise of the battery 1 can be measured at shorter time intervals, so that the temperature rise rate of the battery 1 can be measured with higher accuracy.
In the search mode, since the adiabatic control is performed, the temperature increase rate of the battery 1 is caused only by self-heating of the exothermic reaction of the battery 1. That is, the temperature increase rate of the battery 1 in the search mode does not include a contribution from the external heating of the heating unit 130.
(d) The heat release mode is a mode in which the adiabatic control is performed until the heat release reaction of the battery 1 is completed when the temperature increase rate of the battery 1 becomes equal to or higher than a threshold value. The adiabatic control in the heat release mode is the same as that in the search mode.
The data generation unit 220 is electrically connected to the temperature measurement unit 140, the control unit 210, the storage unit 230, and the display unit 240. The data generator 220 marks measurement data points of the temperature of the battery 1 acquired from the first temperature measurement unit 141 over time based on a control signal from the controller 210, and generates a graph showing the time course of the temperature of the battery 1 shown in fig. 3. The data generating unit 220 transmits measurement data such as data of a graph showing a time transition of the temperature of the battery 1 shown in fig. 3 and measurement data of the internal temperature of the storage container 120 acquired from the second temperature measuring unit 142 to the control unit 210 and the display unit 240.
The storage unit 230 is configured by a ROM that stores various programs and various data, a RAM that temporarily stores programs and data as an operation area, and the like. The storage unit 230 stores the measurement data generated by the data generation unit 220, and data of an exothermic reaction model equation of the battery.
The display unit 240 is, for example, a liquid crystal display, and displays various data such as a graph (see fig. 3) indicating a time transition of the temperature of the battery 1 generated by the data generation unit 220.
The arithmetic processing unit 250 includes a functionalization unit 251 and a parameter estimation unit 252. The functionalization unit 251 and the parameter estimation unit 252 are constituted by a CPU or the like, and control of each unit, various arithmetic processing, and the like are executed in accordance with various programs stored in the storage unit 230. The arithmetic processing unit 250 uses the measurement data stored in the storage unit 230 and the exothermic reaction model equation of the battery for arithmetic processing.
The functionalization unit 251 functionalizes the temperature increase rate of the battery 1 caused only by the exothermic reaction of the battery 1, using the data of the graph (see fig. 3) indicating the time passage of the temperature of the battery 1 stored in the storage unit 230. Specifically, the functionalization unit 251 determines a first function, and determines a second function based on the first function. The first function is a function representing the time dependence and the temperature dependence of the battery 1 for the temperature increase speed of the battery 1. The second function is a function representing the temperature dependence of the battery 1 with respect to the rising temperature caused only by the exothermic reaction of the battery 1. The details of the first function and the second function will be described later.
The parameter estimation unit 252 estimates the parameter of the exothermic reaction model equation of the battery using the second function.
The input unit 260 is connected to the control unit 210 and the arithmetic processing unit 250. The input unit 260 includes input means such as a keyboard, a mouse, and operation buttons. The measurer can operate and input information such as the setting of the heating temperature of the heating unit 130 and the method of the functionalization process by the arithmetic processing unit 250 via the input unit 260.
The evaluation unit 270 evaluates the thermal stability of the battery actually used (actual battery cell) using the exothermic reaction model equation of the battery into which the parameter estimated by the parameter estimation unit 252 is substituted. The evaluation unit 270 is constituted by an arithmetic device such as a computer.
Next, an exothermic reaction model formula of a battery used for predicting the behavior of an exothermic reaction of the battery will be described.
< model formula of exothermic reaction of Battery >
First, since self-heating due to the exothermic reaction of the battery in an adiabatic state contributes to the temperature rise of the entire battery, the heat balance shown in the following formula 1 is established. In the following description of the respective formulae, "battery" means a reactant composed of power generating elements such as electrodes and separators that generate an exothermic reaction. That is, the "battery" does not include a case in which an exothermic reaction does not occur and an extra gap.
[ numerical formula 1]
In formula 1, the values represented by the symbols are as follows.
c: heat capacity per unit mass of the battery (reactant);
t: absolute temperature of the cell (reactant);
t: time;
q0: the amount of heat generated per unit mass of the battery (reactant);
[ X ]: residual rate of battery (reactant);
mr: the rate of temperature rise due to the exothermic reaction of the cell (reactants) alone.
In addition, when the rate formula of the exothermic reaction of the battery follows the arrhenius equation, the following formula 2 is established.
[ numerical formula 2]
In formula 2, the values represented by the symbols are as follows.
h (T): the reaction rate at temperature T;
h0: a frequency factor;
e: activating energy;
r: gas constant.
If the heat generation behavior of the battery is represented by the following n-times single reactions, the following formula 3 is established.
[ numerical formula 3]
The exothermic reaction model equation of the battery shown in the following equation 4 can be derived from the above equations 1, 2 and 3.
[ numerical formula 4]
In the thermal stability evaluation device 10 for a battery and the thermal stability evaluation method for a battery according to the present embodiment, the parameter q of the above formula 4 is estimated0、h0And E, to evaluate the thermal stability of the battery.
When the temperature of the battery becomes T from the start of the exothermic reaction of the battery until the end of the reaction0→T→TfThe remaining rate of the battery becomes [ X ]]0→[X]→[X]fIn this case, the following formula 5 and the following formula 6 are established. Here, the residual rate of the battery at the end of the reaction of the battery [ X ]]fApproximately equal to 0 (zero). In the method for evaluating thermal stability of a battery according to the present embodiment, since the temperature of the battery is increased by external heating of the heating unit 130 in order to accelerate the exothermic reaction of the battery, it is necessary to consider not only the influence of self-heating of the battery but also the influence of external heating.
[ numerical formula 5]
c(Tf-T0-ΔText)＝cΔTABf＝q0([X]0-[X]f)≈q0[X]0… (formula 5)
[ numerical formula 6]
c(Tf-T)＝q0([X]-[X]f)≈q0[X]… (formula 6)
In the above formulas 5 and 6, the values represented by the symbols are as follows.
T0: a reaction start temperature;
Tf: the reaction end temperature;
ΔTABf＝Tf-T0-ΔText: the maximum value of the rise temperature of the cell caused only by the exothermic reaction of the cell (reactant);
ΔText: a maximum value of an increase temperature of the battery due to external heating;
[X]0: initial value of remaining rate of battery (reactant);
[X]f: residual rate of the battery (reactant) at the end of the reaction.
Based on the above equations 5 and 6, the following equations 7 and 8 are established.
[ number formula 7]
[ number formula 8]
Substituting the above-mentioned formula 7 and the above-mentioned formula 8 into the above-mentioned formula 4,
[ numerical formula 9]
When formula 9 is rewritten, formula 10 will be described below.
[ numerical formula 10]
When the logarithm of both sides of the above formula 10 is taken, the following formula 11 is obtained.
[ numerical formula 11]
Here, in the above formula 11, k*Is the virtual 0-order reaction rate constant.
Evaluation of thermal stability of the battery according to the present embodimentIn the method, the maximum value Δ T of the temperature rise of the battery due to only the exothermic reaction of the battery is calculated using the above-described equations 8 and 11, the first function and the second function described laterABfAnd reaction completion temperature T of the batteryfTo estimate the parameter q of equation 40、h0And E. Can use substituted parameter q0、h0And E, formula 4, to evaluate thermal stability of the battery.
Next, a method for evaluating thermal stability of the battery according to the present embodiment will be described with reference to fig. 4 and 5.
< method for evaluating thermal stability of Battery >
Fig. 4 is a flowchart showing the procedure of the thermal stability evaluation method of the battery using the thermal stability evaluation device 10 of the battery. The respective steps of the method for evaluating thermal stability of a battery will be described below.
The method for evaluating thermal stability of a battery includes a first measurement step (first S1 and S2), a second measurement step (S1 to S3), a third measurement step (S4), a functionalization step (S5), a parameter estimation step (S6), and a thermal stability evaluation step (S7).
In the first to third measurement steps (S1 to S4), an accelerated rate heat measurement test was performed to obtain a graph of the time course of the temperature of the battery shown in fig. 3. In fig. 3, the area of "first measurement" indicates data obtained in the first measurement step, the area of "second measurement" indicates data obtained in the second measurement step, and the area of "third measurement" indicates data obtained in the third measurement step.
(first measurement step)
In the first measurement step, control unit 210 performs a heating step (first S1) and a standby step (first S2) to measure the time lapse of the temperature of the battery. In the first measurement step, the heating step (first S1) and the standby step (first S2) are performed once each.
Specifically, in the heating step (S1), the control unit 210 mainly controls the second heating unit 132 to set the heating mode in which the internal temperature of the storage container 120 is heated to a predetermined temperature. As the temperature of the internal temperature of the preservation container 120 rises, the temperature of the battery rises as shown in fig. 3. In fig. 3, "heating (first time)" of the first measurement region indicates data obtained in the heating step (first S1) set as the heating mode for the first time, and "standby (first time)" indicates data obtained in the standby step (first S2) set as the standby mode for the first time.
Next, in the standby step (S2), the control unit 210 controls the heating unit 130 to switch from the heating mode to the standby mode. In the standby mode, the control unit 210 mainly controls the second heating unit 132 to wait for a predetermined time (standby time) until the internal temperature of the storage container 120 becomes constant. The measurer experimentally obtains in advance the time until the internal temperature of the storage container 120 is constant and the temperature of the battery is equal to the internal temperature of the storage container 120, and sets the time as the standby time.
(second measurement step)
In the second measurement step, the control unit 210 performs a search step (S3) of performing adiabatic control for bringing the battery into an adiabatic state to determine the temperature increase rate m of the batteryTWhether or not it is above a threshold. In the second measurement step, the temperature rise rate m of the battery is measuredTUntil the temperature becomes equal to or higher than the threshold value, the heating step (S1), the standby step (S2), and the search step (S3) are repeated to measure the time course of the temperature of the battery.
Specifically, in the search step (S3), the control unit 210 controls the heating unit 130 to set the search mode, and calculates the temperature increase rate m of the battery from the slope of the graph showing the time transition of the temperature of the battery, which is generated by the data generation unit 220 and is shown in fig. 3T. The control unit 210 automatically performs the temperature increase rate m of the battery at predetermined time intervalsTAnd (4) calculating. At a temperature rise rate m of the batteryTIf the temperature is lower than the threshold value (S3: NO), the heating step (S1), the standby step (S2), and the search step (S3) are repeated. In fig. 3, "heating" in the second measurement area means data obtained in the second heating step (S1) and the second and subsequent heating modes, and "waiting" means data obtained in the second heating stepThe data obtained in the standby step (S2) which is set to the standby mode for the second time and the subsequent times. The "search" in fig. 3 indicates data obtained in the search step (S3) in the search mode.
In the search step (S3), the control unit 210 controls the first heating unit 131 and the second heating unit 132 based on the measurement data of the first temperature measurement unit 141 and the second temperature measurement unit 142, and performs adiabatic control for bringing the battery into an adiabatic state. More specifically, when the internal temperature of the storage container 120 is higher than the temperature of the battery, the control unit 210 controls the first heating unit 131 to increase the temperature of the battery, and controls the temperature of the battery to be substantially the same as the internal temperature of the storage container 120. When the exothermic reaction of the battery progresses so that the temperature of the battery becomes higher than the internal temperature of the storage container 120, the control unit 210 controls the second heating unit 132 to increase the internal temperature of the storage container 120, and controls the internal temperature of the storage container 120 to be substantially the same as the temperature of the battery. In this manner, the controller 210 performs adiabatic control so that the internal temperature of the storage container 120 is substantially equal to the temperature of the battery 1.
(third measurement step)
At a temperature rise rate m of the batteryTWhen the value is equal to or higher than the threshold value (S3: "yes"), the control unit 210 executes the third measurement step. In the third measurement step, the control unit 210 performs a heat release step (S4) for performing adiabatic control until the heat release reaction of the battery is completed, and measures the time lapse of the temperature of the battery. Note that the heat-insulating control in the heat-releasing step (S4) is the same as in the searching step (S3), and therefore, the description thereof is omitted.
Specifically, in the heat radiation step (S4), the control unit 210 controls the heating unit 130 to set the heat radiation mode. The "heat release" in the third measurement region in fig. 3 is data obtained in the heat release step (S4) in the heat release mode. In the heat release process (S4), as shown in fig. 3, after the exothermic reaction of the battery progresses so that the temperature of the battery rapidly rises due to self-heating, the reaction ends and the temperature becomes constant. The temperature at the end of the reaction was measured as the reaction end temperature of the cellTf。
In the first measurement step, since the exothermic reaction of the battery does not progress, the temperature of the battery is increased only by external heating. In the second measurement process, since the exothermic reaction of the battery progresses, the temperature of the battery rises by self-heating and external heating. In the third measurement step, the exothermic reaction of the battery further progresses and adiabatic control is performed, so that the temperature of the battery rises only by self-heating.
Referring to fig. 3, the reaction start temperature (temperature at which the second measurement step is started) T of the battery is measured0Reaction completion temperature T at which exothermic reaction of the battery is completed by the third measurement stepfThe rising temperature (T) of the batteryf-T0) Becomes the maximum value DeltaT of the rising temperature caused by the exothermic reaction of the batteryABfPlus a maximum value DeltaT of the rise temperature of the battery caused by external heatingextThe resulting value (. DELTA.T)ABf+ΔText)。
(functionalization step)
In the functionalization step (S5), the functionalization portion 251 uses the measurement data of the second measurement step and the third measurement step to adjust the temperature rise rate m of the battery due to the exothermic reaction of the battery aloneTFunctionalization is performed. Specifically, the functionalization unit 251 uses the temperature increase rate m of the battery in which the search step (S3) and the heat release step (S4) of the third measurement step are repeatedly performed a plurality of times in the second measurement stepTTo increase the temperature rise rate m of the battery caused only by the exothermic reaction of the batteryTFunctionalization is performed.
Fig. 5 is a flowchart showing the procedure of the functionalization process (S5). As shown in fig. 5, the functionalization step (S5) includes a first functionalization step (S51) and a second functionalization step (S52).
(first functionalization step)
In the first functionalization step (S51), the functionalization unit 251 calculates the temperature rise rate m of the battery in the second measurement step and the third measurement stepTDetermining a first function m representing the time T dependence and the temperature T dependence of the batteryT(t，T)。
Here, since the adiabatic control is performed in the search step (S3) in the second measurement step and the heat release step (S4) in the third measurement step, the contribution of external heating is not included in the temperature rise of the battery. Therefore, the temperature increase rate of the battery in the search step (S3) and the heat release step (S4) can be directly used as the temperature increase rate m due to the heat release reaction of the battery aloneT. Therefore, the functional unit 251 can determine the temperature increase rate m indicating the battery using the slopes of the graphs of the search step (S3) and the heat release step (S4) shown in fig. 3TAnd a first function m of the time T dependence of (a) and the temperature T dependence of the batteryT(t，T)。
On the other hand, in the heating step (S1) and the standby step (S2) in the second measurement step, the contribution of external heating is included because no adiabatic control is performed. Therefore, the functionalization unit 251 performs a process of removing the contribution of the external heating from the heating step (S1) and the standby step (S2) in the second measurement step.
In order to eliminate the contribution from the external heating, the function unit 251 calculates the temperature increase rate m of the battery in the heating step (S1) and the standby step (S2) of the second measurement stepTThe temperature increase rate m of the battery in the heating step (S1) of the second measurement step and the search step (S3) before and after the standby step (S2)TTo perform averaging.
In the present embodiment, the function unit 251 sets the temperature increase rate m of the battery in the heating step (S1) and the standby step (S2) in the second measurement stepTThe temperature rise rate m of the battery at the start time (time) and the end time (time) of the search step (S3) before and after the heating step (S1) and the standby step (S2) in the second measurement stepTIs added and averaged.
Fig. 6 is a partially enlarged graph of the second measurement step in the graph showing the time transition of the temperature of the battery shown in fig. 3. The end time of the ith search step (S3) in the search steps (S3) repeatedly executed a plurality of times in the second measurement step is set as ti，2And the ending temperature is set to Ti，2. The start time of the (i + 1) th search step (S3) is ti+1，1And the starting temperature is set to Ti+1，1. At this time, the start time of the heating step (S1) and the standby step (S2) at the i-th time between the search step at the i-th time (S3) and the search step at the i + 1-th time (S3) is ti，2A starting temperature of Ti，2T is the end timei+1，1End temperature Ti+1，1。
The temperature rise rate m of the battery for the heating process (S1) and the standby process (S2) of the ith timeTi(1，2)Represents the time ti(1，2)Dependence and temperature T of the batteryi(1，2)The first function of the dependency is set as the end time t of the ith search step (S3)i，2Temperature rise rate m of the batteryT(3)(ti，2，Ti，2) And start time t of the i +1 th search step (S3)i+1，1Temperature rise rate m of the batteryT(3)(ti+1，1，Ti+1，1) The sum-average of (a) is represented by the following formula 12.
[ numerical formula 12]
The number of times the heating step (S1) and the standby step (S2) are repeated in the second measurement step is j times. The data of the temperature increase rates m of the batteries representing the heating step (S1) and the standby step (S2) are determined using the data of the temperature increase rates of the batteries in all the search steps (S3) from the 1 st time (i ═ 1) to the j th time (i ═ j)TAnd a first function m of the time T dependence of (a) and the temperature T dependence of the batteryT(t，T)。
(second functionalization step)
Next, in the second functionalization step (S52), the functionalization unit 251 uses the first function mT(T, T) for the rise temperature DeltaT caused only by the exothermic reaction of the batteryABA second function representing the temperature T dependency of the battery is determined. In particular, by applying a first function mT(T, T) is integrated over time T to obtainDefinitely means the rising temperature deltat caused only by the exothermic reaction of the batteryABOf the battery, a second function Δ T of the temperature T dependence of the batteryAB(T)。
In the description of the above-described functionalization process (S5), the temperature increase rate of the battery is functionalized using the data of the temperature increase rate of the battery for all the search processes (S3) which are repeatedly performed a plurality of times, but the method of using the data of all the search processes is not limited as long as the data of at least the first and last search processes are used. For example, the first function may be determined by averaging the temperature rise rates of the batteries in the second measurement step as a whole using the temperature rise rates of the batteries in the first and last search steps.
(parameter estimation Process)
In the parameter estimation step (S6), the parameter estimation unit 252 sets the reaction completion temperature T as shown in the following formula 13fSubstituting the second function Δ TAB(T) setting the obtained value as the maximum value DeltaT of the temperature rise caused only by the exothermic reaction of the batteryABf。
[ numerical formula 13]
ΔTAB(Tf)＝ΔTABf… (formula 13)
Using a first function mT(T, T), second function Δ TAB(T) maximum value of temperature rise DeltaT due to exothermic reaction of battery aloneABfAnd reaction completion temperature T of the batteryfThe parameter q of the exothermic reaction model equation of the battery represented by the above equation 4 is estimated from the above equation 8 and the above equation 110、h0、E。
(evaluation step)
In the evaluation step (S7), the evaluation unit 270 substitutes the estimated parameter q for the parameter q0、h0And E (equation 4) to evaluate the thermal stability of the actually used battery (actual battery cell).
Specifically, the evaluation unit 270 evaluates the parameter q based on the parameter q0、h0E and the exothermic reaction model equation (equation 4) of the cell to predict, for example, the actualResults of the heating test of the battery cell. In the heating test, the actual battery cell (reactant) was put into a constant temperature bath, and the temperature T of the constant temperature bath was measuredaThe actual cell temperature T at the time of change. Can estimate the parameter q by substituting it0、h0And the result of the actual cell heating test was predicted from the exothermic reaction model equation (equation 4) for the cell with the value of E and the following equation 14. In the following description of formula 14, "actual cell" means a reactant composed of a power generating element such as an electrode or a separator that generates an exothermic reaction. That is, the "actual battery cell" does not include a laminate film, a can or the like, and an extra gap, which do not generate an exothermic reaction.
[ numerical formula 14]
In formula 14, the values represented by the symbols are as follows.
M: the mass of the actual cell (reactant);
c: heat capacity per unit mass of the actual cell (reactant);
k: the thermal conductivity of the boundary surface of the actual battery cell (reactant) with the outside;
a: the boundary surface area of the actual cell (reactant) with the outside;
Ta: the temperature of the thermostatic bath (outside temperature).
As described above, the thermal stability of the actual battery cell can be evaluated by estimating the parameters of the exothermic reaction model formula (formula 4) using the coin-type battery cell for testing. As a result, the design can be optimized to obtain thermal stability without trial production of actual battery cells, and therefore, the development cost of actual battery cells can be significantly reduced.
As described above, the present embodiment described above achieves the following effects.
The method for evaluating thermal stability of a battery according to the present embodiment includes a first measurement step (first S1 and S2), a second measurement step (S1 to S3), a third measurement step (S4), and a parameter estimation step (S6). In the first measurement step, a heating step (first S1) for heating the internal temperature of the storage container 120 to a predetermined temperature and a standby step (first S2) for waiting for a predetermined time after the heating step are performed to measure the time course of the temperature of the battery. In the second measurement step, after the first measurement step, a search step (S3) is performed for performing adiabatic control for bringing the battery into an adiabatic state to determine whether or not the temperature increase rate of the battery is equal to or greater than a threshold value, and the heating step, the standby step, and the search step are repeated until the temperature increase rate of the battery becomes equal to or greater than the threshold value (S3: NO), thereby measuring the time lapse of the temperature of the battery. In the third measurement step, when the temperature increase rate of the battery is equal to or higher than the threshold value (yes in S3), a heat release step for performing adiabatic control until the heat release reaction of the battery is completed is performed, and the time transition of the temperature of the battery is measured. In the parameter estimation step (S6), the parameters of the exothermic reaction model equation of the battery are estimated using the temperature increase rate of the battery determined from the measurement data of at least the search step and the exothermic step.
According to the method for evaluating thermal stability of a battery, the parameter is estimated in consideration of the exothermic reaction of the battery in the second measurement step before the temperature increase rate of the battery reaches the threshold value. Therefore, the estimation accuracy of the parameters can be improved. This makes it possible to predict the behavior of the exothermic reaction of the battery more accurately.
Before the parameter estimation step (S6), a functionalization step (S5) is further provided, in which the temperature increase rate of the battery due to only the exothermic reaction of the battery is functionalized using the temperature increase rates of the battery in at least the first and last search steps of the search steps performed a plurality of times in the second measurement step. Thus, the accuracy of parameter estimation can be further improved by using the temperature increase rate of the battery in the search step in which no contribution from external heating is made by adiabatic control and by functionalizing the temperature increase rate of the battery.
The functionalization step (S5) includes a first functionalization step (S51) in which a first function representing the time dependency and the temperature dependency of the battery is determined with respect to the temperature increase rate of the battery in the first functionalization step (S51). This allows the time dependence of the temperature rise rate of the battery and the temperature dependence of the battery to be taken into account, and therefore the accuracy of parameter estimation can be further improved.
The functionalization step (S5) further includes a second functionalization step in which a second function indicating the temperature dependence of the battery is determined with respect to the temperature rise of the battery due to only the exothermic reaction of the battery, using the first function determined in the first functionalization step. Thereby, the relationship between the rising temperature due to only the exothermic reaction of the battery, in which the contribution of external heating is not present, and the temperature of the battery including the contribution of external heating can be obtained as a function. Therefore, the behavior of the exothermic reaction of the battery from which the contribution of the external heating is removed can be predicted more accurately.
In the parameter estimation step (S6), the maximum value of the temperature rise of the battery due to the exothermic reaction of the battery alone is determined using the reaction completion temperature at which the exothermic reaction of the battery ends, which is measured in the third measurement step, and the second function. This makes it possible to more accurately determine the temperature of the battery, which increases only by the exothermic reaction of the battery, from the measurement data including the contribution of the external heating.
In the functionalization step (S5), the contribution of external heating is removed from the heating step (S1) and the standby step (S2) in the second measurement step. Thereby, the contribution made by the external heating can be removed from the measurement data including the contributions of the self-heating and the external heating of the battery. Therefore, the behavior of the exothermic reaction of the battery from which the contribution of the external heating is removed can be predicted more accurately.
In the functionalization step (S5), the temperature increase rates of the batteries in the heating step and the standby step in the second measurement step are averaged by the temperature increase rates of the batteries in the search step or the heat release step before and after the heating step and the standby step in the second measurement step, thereby removing the contribution due to the external heating. Thus, by a simple method of averaging measurement data of the search step or the heat release step that does not include the contribution of the external heating, the contribution of the external heating can be eliminated from the measurement data of the heating step and the standby step that include the contribution of the external heating.
The thermal stability evaluation device 10 for a battery according to the present embodiment includes the adiabatic calorimeter 100, a control unit 210, and a parameter estimation unit 252. The heat-insulating calorimeter 100 includes a storage container 120 for storing a battery, a heating unit 130 for heating the inside of the storage container 120, a first temperature measuring unit 141 for measuring the internal temperature of the storage container 120, and a second temperature measuring unit 142 for measuring the temperature of the battery. The control unit 210 controls the operation of the adiabatic calorimeter 100 in the following mode: a heating mode for heating the inside temperature of the holding container 120 to a predetermined temperature; a standby mode for waiting a predetermined time after the heating mode; a search mode for performing adiabatic control for setting the battery in an adiabatic state to determine whether or not a temperature increase rate of the battery is equal to or greater than a threshold value; and a heat release mode for repeating the heating mode, the standby mode, and the search mode until the temperature increase rate of the battery becomes equal to or greater than a threshold value, and performing adiabatic control until the heat release reaction of the battery is completed when the temperature increase rate of the battery becomes equal to or greater than the threshold value. The parameter estimation unit 252 estimates the parameter of the exothermic reaction model equation of the battery using the temperature increase rate of the battery obtained from the measurement data of the second temperature measurement unit 142 in at least the search mode and the heat release mode.
According to the thermal stability evaluation device 10 for a battery, the parameter is estimated in consideration of the exothermic reaction of the battery until the temperature increase rate of the battery reaches the threshold value. Therefore, the estimation accuracy of the parameters can be improved. This makes it possible to predict the behavior of the exothermic reaction of the battery more accurately.
The apparatus further includes a functionalization unit 251 for functionalizing the temperature increase rate of the battery due to only the exothermic reaction of the battery by using the temperature increase rates of the battery in the search patterns repeated a plurality of times, the search patterns being at least the first and last search patterns. Thus, the accuracy of parameter estimation can be further improved by using the temperature increase rate of the battery in the search mode in which no contribution from external heating is caused by adiabatic control and by functionalizing the temperature increase rate of the battery.
The functionalization unit 251 determines a first function indicating the time dependency and the temperature dependency of the battery with respect to the temperature increase rate of the battery. This allows the time dependence of the temperature rise rate of the battery and the temperature dependence of the battery to be taken into account, and therefore the accuracy of parameter estimation can be further improved.
The functionalization unit 251 determines a second function indicating the temperature dependence of the battery with respect to the temperature rise of the battery due to only the exothermic reaction of the battery, using the first function. Thereby, the relationship between the rising temperature due to only the exothermic reaction of the battery, in which the contribution of external heating is not present, and the temperature of the battery including the contribution of external heating can be obtained as a function. Therefore, the behavior of the exothermic reaction of the battery from which the contribution of the external heating is removed can be predicted more accurately.
The parameter estimation unit 252 determines the maximum value of the temperature rise of the battery due to the exothermic reaction of the battery alone, using the reaction completion temperature at which the exothermic reaction of the battery is completed and the second function. Thus, the temperature of the battery, which rises only by the exothermic reaction of the battery, can be more accurately determined from the measurement data including the contribution of the external heating.
In addition, in the functionalization portion 251, the contribution by the external heating is removed from the heating mode and the standby mode which are repeated a plurality of times, the second time and the subsequent times among the heating mode and the standby mode. Thereby, the contribution made by the external heating can be removed from the measurement data including the contributions of the self-heating and the external heating of the battery. Therefore, the behavior of the exothermic reaction of the battery from which the contribution of the external heating is removed can be predicted more accurately.
In addition, in the functionalization unit 251, the temperature increase rates of the battery in the second and subsequent heating modes and the standby mode are averaged by the temperature increase rates of the battery in the search mode or the heat release mode before and after the heating mode and the standby mode, thereby removing the contribution by the external heating. Thus, it is possible to eliminate the contribution due to the external heating from the measurement data in the heating mode and the standby mode including the contribution due to the external heating by a simple method of averaging the measurement data in the search mode or the heat radiation mode not including the contribution due to the external heating.
Although the method for evaluating thermal stability of a battery and the apparatus for evaluating thermal stability of a battery according to the present invention have been described above with reference to the embodiments, the present invention is not limited to the embodiments described above, and can be modified as appropriate based on the descriptions of the claims.
For example, in the above-described embodiment, as a method of eliminating the contribution of the external heating in the second measurement step, the heating in the second measurement step and the addition average of the temperature increase rates of the battery at the start time and the end time of the search step before and after the standby step are used for averaging, but the present invention is not limited to this. For example, the averaging can be performed using a multiplication averaging or the like. The average value of the temperature increase rates of the batteries at the start time and the end time is not limited, and the average value of the temperature increase rates of the batteries in all the regions of the preceding and following search steps may be used.
In the above-described embodiment, in the second and third measurement steps, the search step is performed after the heating step and the standby step, and the heat radiation step is performed thereafter. In the case where the heat releasing step is performed after the heating step and the standby step, the temperature increase rate of the battery in the heat releasing step can be used as a function of the heating step and the standby step.
In the above-described embodiment, the thermal stability of the actual battery cell was evaluated by estimating the parameters of the exothermic reaction model equation of the battery based on the measurement data obtained by performing the accelerated rate calorimetry test using the coin-type battery cell for test, but the present invention is not limited thereto, and the accelerated rate calorimetry test may be performed using the actual battery cell.
The structure of the adiabatic calorimeter is not limited to the structure described in the above embodiment as long as the acceleration rate heat measurement test can be performed. For example, the heating unit may be configured not to include a first heating unit that heats the battery, but to include only a second heating unit that heats the inside of the storage container.
Description of the reference numerals
1: a battery; 10: a thermal stability evaluation device; 100: a thermally insulated calorimeter; 110: a sample container; 111: a spherical portion; 112: an introducing pipe; 120: a storage container; 130: a heating section; 131: a first heating section; 132: a second heating section; 140: a temperature measuring part; 141: a first temperature measuring section; 142: a second temperature measuring section; 200: a control unit; 210: a control unit; 220: a data generation unit; 230: a storage unit; 240: a display unit; 250: an arithmetic processing unit; 251: a functionalization unit; 252: a parameter estimation unit; 260: an input section; 270: an evaluation unit.
Claims (14)
1. A method for evaluating thermal stability of a battery using an adiabatic calorimeter having a storage container for storing the battery, the method comprising:
a first measurement step of measuring a time lapse of the temperature of the battery by performing a heating step of heating the internal temperature of the storage container to a predetermined temperature and a standby step of waiting for a predetermined time after the heating step;
a second measurement step of performing, after the first measurement step, a search step of performing adiabatic control for bringing the battery into an adiabatic state to determine whether or not a temperature increase rate of the battery is equal to or greater than a threshold value, and measuring a time lapse of the temperature of the battery by repeating the heating step, the standby step, and the search step until the temperature increase rate of the battery becomes equal to or greater than the threshold value;
a third measurement step of, when the temperature increase rate of the battery becomes equal to or higher than the threshold value, performing an exothermic step for performing the adiabatic control until the exothermic reaction of the battery is completed, and measuring a time lapse of the temperature of the battery; and
and a parameter estimation step of estimating a parameter of the exothermic reaction model equation of the battery using a temperature increase rate of the battery obtained from measurement data of at least the search step and the exothermic step.
2. The method for evaluating thermal stability of a battery according to claim 1,
prior to the parameter estimation process,
the method further includes a functionalization step of functionalizing a temperature increase rate of the battery due to only an exothermic reaction of the battery using temperature increase rates of the battery in at least first and last search steps of the search steps performed a plurality of times in the second measurement step.
3. The method for evaluating thermal stability of a battery according to claim 2,
the functionalization step includes a first functionalization step of determining a first function indicating a time dependency and a temperature dependency of the battery with respect to a temperature rise rate of the battery.
4. The method for evaluating thermal stability of a battery according to claim 3,
the functionalization step further includes a second functionalization step of determining a second function indicating temperature dependence of the battery with respect to an increase temperature of the battery due to only an exothermic reaction of the battery, using the first function determined in the first functionalization step.
5. The method for evaluating thermal stability of a battery according to claim 4,
in the parameter estimation process, the parameter estimation process is performed,
determining a maximum value of the temperature rise of the battery due to only the exothermic reaction of the battery, using the reaction completion temperature at which the exothermic reaction of the battery is completed, measured in the third measuring step, and the second function.
6. The method for evaluating thermal stability of a battery according to any one of claims 2 to 5,
in the step of converting the functional group into a functional group,
the contribution of external heating is removed from the heating step and the standby step in the second measurement step.
7. The method for evaluating thermal stability of a battery according to claim 6,
in the step of converting the functional group into a functional group,
the temperature increase rates of the battery in the heating step and the standby step in the second measurement step are averaged by the temperature increase rates of the battery in the search step or the heat release step before and after the heating step and the standby step, thereby removing the contribution of the external heating.
8. A thermal stability evaluation device for a battery includes:
an adiabatic calorimeter having a storage container for storing a battery, a heating unit for heating the inside of the storage container, a first temperature measuring unit for measuring the internal temperature of the storage container, and a second temperature measuring unit for measuring the temperature of the battery;
a control unit that controls the operation of the adiabatic calorimeter in the following mode: a heating mode for heating the inside temperature of the holding container to a predetermined temperature; a standby mode for waiting a predetermined time after the heating mode; a search mode for performing adiabatic control for setting the battery in an adiabatic state to determine whether or not a temperature increase rate of the battery is equal to or greater than a threshold value; and a heat release mode for repeating the heating mode, the standby mode, and the search mode until a temperature increase rate of the battery becomes equal to or greater than the threshold value, and performing the adiabatic control until an exothermic reaction of the battery is completed when the temperature increase rate of the battery becomes equal to or greater than the threshold value; and
and a parameter estimation unit that estimates a parameter of an exothermic reaction model equation of the battery using a temperature increase rate of the battery obtained from measurement data of the second temperature measurement unit in at least the search mode and the heat release mode.
9. The thermal stability evaluation device of a battery according to claim 8,
the apparatus further includes a function unit that uses the temperature increase rates of the battery in the search pattern repeated a plurality of times, at least for the first time and the last time, to convert the temperature increase rate of the battery due to only an exothermic reaction of the battery.
10. The thermal stability evaluation device of a battery according to claim 9,
the function unit determines a first function indicating a time dependency and a temperature dependency of the battery with respect to a temperature increase rate of the battery.
11. The thermal stability evaluation device of a battery according to claim 10,
the function unit determines a second function indicating temperature dependence of the battery with respect to a temperature rise of the battery caused only by an exothermic reaction of the battery, using the first function.
12. The thermal stability evaluation device of a battery according to claim 11,
the parameter estimating unit determines a maximum value of the temperature rise of the battery due to the exothermic reaction of the battery alone, using the reaction end temperature at which the exothermic reaction of the battery ends, measured by the second temperature measuring unit, and the second function.
13. The device for evaluating thermal stability of a battery according to any one of claims 9 to 12,
the functional unit removes a contribution from external heating from the heating mode and the standby mode that are repeated a plurality of times, the heating mode and the standby mode being the second time and subsequent times.
14. The thermal stability evaluation device of a battery according to claim 13,
the functionalization unit eliminates the contribution of the external heating by averaging the temperature increase rates of the battery in the search mode or the heat release mode before and after the heating mode and the standby mode with respect to the temperature increase rates of the battery in the heating mode and the standby mode for the second time and subsequent times.
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| JP2003519782A (en) * | 1999-12-29 | 2003-06-24 | スリーエム イノベイティブ プロパティズ カンパニー | Method and apparatus for characterizing high energy electrochemical cells using power functions obtained by calorimetry |
| JP2006250771A (en) * | 2005-03-11 | 2006-09-21 | Sumitomo Chemical Co Ltd | Evaluation method of heat stability of matter |
| CN1987508A (en) * | 2006-12-26 | 2007-06-27 | 天津力神电池股份有限公司 | Predicting method for lithiumion cell heat safety performance |
| CN103293484A (en) * | 2013-06-06 | 2013-09-11 | 天津力神电池股份有限公司 | Method for quickly evaluating performance of lithium ion batteries by testing quantities of released heat |
| CN103837834A (en) * | 2014-02-18 | 2014-06-04 | 清华大学 | Testing method of thermal runaway characteristic of battery |
| CN106645274A (en) * | 2016-09-19 | 2017-05-10 | 中国计量大学 | Method for measuring and calculating dynamic heat capacity of adiabatic reaction calorimetry samples |
| CN107389723A (en) * | 2017-07-31 | 2017-11-24 | 中国计量大学 | A kind of adiabatic reaction starting point based on difference variation judges and temperature method for tracing |
-
2017
- 2017-12-20 CN CN201780097577.0A patent/CN111448450A/en active Pending
- 2017-12-20 WO PCT/JP2017/045769 patent/WO2019123577A1/en active Application Filing
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003519782A (en) * | 1999-12-29 | 2003-06-24 | スリーエム イノベイティブ プロパティズ カンパニー | Method and apparatus for characterizing high energy electrochemical cells using power functions obtained by calorimetry |
| JP2006250771A (en) * | 2005-03-11 | 2006-09-21 | Sumitomo Chemical Co Ltd | Evaluation method of heat stability of matter |
| CN1987508A (en) * | 2006-12-26 | 2007-06-27 | 天津力神电池股份有限公司 | Predicting method for lithiumion cell heat safety performance |
| CN103293484A (en) * | 2013-06-06 | 2013-09-11 | 天津力神电池股份有限公司 | Method for quickly evaluating performance of lithium ion batteries by testing quantities of released heat |
| CN103837834A (en) * | 2014-02-18 | 2014-06-04 | 清华大学 | Testing method of thermal runaway characteristic of battery |
| CN106645274A (en) * | 2016-09-19 | 2017-05-10 | 中国计量大学 | Method for measuring and calculating dynamic heat capacity of adiabatic reaction calorimetry samples |
| CN107389723A (en) * | 2017-07-31 | 2017-11-24 | 中国计量大学 | A kind of adiabatic reaction starting point based on difference variation judges and temperature method for tracing |
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