Thermal runaway pinpoint heating test

Abstract

A method and apparatus allows for testing an electrochemical cell. The apparatus includes a heat source, a chamber, and a diffuser coupling the heat source to the chamber. The heat source applies heat through the diffuser to a pinpoint portion of the electrochemical cell. The application of heat induces a thermal runaway condition in the electrochemical cell due to a localized internal short circuit. It is then determined whether the electrochemical cell valves, bursts, or explodes in response to application of the heat source to the thermal runaway pinpoint portion of the electrochemical cell.

Description

[Technical Field]

[0001] Priority claims This application claims priority to U.S. Patent Application No. 17 / 486,133, filed September 27, 2021 (Docket No. RPS920210077-US-NP / 2707.077US1), which is incorporated herein by reference in its entirety.

[0002] The embodiments described herein relate generally to testing electrochemical cells / batteries, and in one embodiment, but not by way of limitation, to thermal runaway pinpoint heating testing on electrochemical cells or batteries by simulating an internal short circuit without affecting the health of the electrochemical cell or battery. [Background technology]

[0003] There are four types of serious internal short circuits that can occur in an electrochemical cell. These types are current collector (positive & negative) short circuit, negative current collector-cathode short circuit, positive current collector-anode short circuit, and anode-cathode short circuit. Of these types, the greatest risk of cell failure occurs with current collector (positive & negative) short circuit. Regardless of the type of failure, the failure is due to thermal runaway. If the cell is misused or not properly designed, thermal runaway can occur, which can result in catastrophic events such as cell rupture or explosion. There are several factors that can lead to such internal short circuits, including material defects, manufacturing defects, contamination, dendrite growth, metal plating, external misuse, exposure to temperature extremes, etc.

[0004] An example of a material defect is a situation in which the separator in an electrochemical cell is damaged, compressed, or perforated. This damage, compression, or perforation can lead to a short circuit between the anode and cathode, depending on the separator design and materials. This results in a single point of contact between the anode and cathode. Separator degradation can occur due to exposure to high temperatures and / or due to incorrectly specified materials.

[0005] Several tests currently exist that can determine whether a particular electrochemical cell design has an unacceptable likelihood of internal short circuiting and subsequent thermal runaway conditions and failure. However, these tests have drawbacks.

[0006] The first test is called the nail penetration test. In the nail penetration test, a nail is driven into an electrochemical cell in an attempt to create an internal short circuit. However, the test is not consistent because there are many variables involved. These variables include the speed at which the nail penetrates the electrochemical cell, the sharpness or bluntness of the nail, and the conductivity of the nail. Also, the process by which a commercial electrochemical cell in the field progresses to thermal runaway due to an internal short circuit involves very different physical processes than those produced by the nail penetration test.

[0007] The nail penetration test is therefore not a useful test for the type of internal short circuit that develops over time in the field. Thermal runaway associated with nail penetration occurs within approximately 200 to 500 milliseconds, not over time as in the field. The nail penetration test results in variable results and does not reflect a fault condition that results in thermal runaway as a result of an internal short circuit. Perhaps most critically, the nail penetration test does not create a single point of contact between the anode and cathode.

[0008] There are also several heating tests that can test designs for the susceptibility of electrochemical cells to internal short circuits and thermal runaway conditions. Examples include heating tape, thermal chambers, sand baths, ceramic heaters, infrared light (focused), photonic light (laser), and open flames. However, these current heating tests do not simulate any of the types of internal short circuits that occur in the field. That is, again, and perhaps most critically, these current heating tests do not create a single-contact electrical short.

[0009] An existing test for electrochemical cells that creates an internal short circuit is the forced internal short circuit (FISC) test. The FISC test is designed to simulate an internal short circuit that occurs at a single contact point between the anode and cathode. The FISC test can detect problems with electrochemical cells caused by material defects, manufacturing defects, contamination, dendrite growth, and lithium plating. The FISC test allows for a single contact point between the anode and cathode without introducing inaccuracies, doubts, and other factors that can cause erroneous results. However, a drawback of the FISC test is that it does not evaluate venting performance and the structural integrity of the electrochemical cell can under thermal runaway conditions.

[0010] Additionally, the FISC test requires that the electrochemical cell be fully charged. It further requires disassembly of the cell and placement of metal particles (specially tailored metal particles placed in one or two locations based on the cell design) in the cell. The FISC test must also be performed in a special environment with special non-conductive tools. The FISC test must be completed in less than 30 minutes to prevent electrolyte evaporation. The FISC test further requires that the cell be placed in a sealed bag and then conditioned in a chamber.

[0011] Another existing test, the NREL / NASA (National Renewable Energy Laboratory; National Aeronautics and Space Administration) internal short-circuit instigator, also creates a single contact point between the anode and cathode upon request. Furthermore, the NREL / NASA test does not crush, pierce, bend, warp, or deform the cell, nor does it compromise cell integrity. Additionally, the NREL / NASA test can be created by cell manufacturers, can be independently started at any state of charge, is suitable for cylindrical, prismatic, and pouch cell designs, and presents minimal risk (handling and starting) in the test laboratory. However, the NREL / NASA test is somewhat artificial because battery cells must be fabricated with elements specifically required for the test, such as copper pads, separators with copper packs, wax phase change materials, and aluminum pads. Additionally, similar to the FISC test, the NREL / NASA test does not evaluate venting performance, and electrochemical cells can be constructed for integrity under thermal runaway conditions.

[0012] To ensure adequate testing of electrochemical cells' reliability, their safety features, and functionality under thermal runaway conditions, only test methods that simulate real-world single-contact internal short circuits should be considered. As noted above, FISC and NREL / NASA tests can create single-contact internal short circuits, but these tests have drawbacks. Test methods that compromise the integrity of the electrochemical cell (e.g., crushing, penetration, deformation, and heating) do not represent any type of internal, electrically or electrochemically induced short circuit failure. Summary of the Invention [Means for solving the problem]

[0013] The drawings are not necessarily drawn to scale, and like numerals may describe similar components in different figures. Like numerals with different suffixes may represent different instances of similar components. Some embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1A] FIG. 1 is a block diagram illustrating the operation and features of an electrochemical cell thermal runaway pinpoint heating test system. [Figure 1B] FIG. 1 is a block diagram illustrating the operation and features of an electrochemical cell thermal runaway pinpoint heating test system. [Figure 2] 1 illustrates one embodiment of an electrochemical cell thermal runaway pinpoint heating system. [Figure 3] 1 illustrates another embodiment of an electrochemical cell thermal runaway pinpoint heating test system. [Figure 4] 1 illustrates the difference in heating area of ​​an electrochemical cell using one embodiment disclosed herein and a prior art standard heating method. DETAILED DESCRIPTION OF THE INVENTION

[0015] To overcome the shortcomings of existing electrochemical cell safety tests, what is needed is a test that provides a qualitative and quantitative means of measuring the likelihood of electrochemical cell failure under thermal runaway conditions, and a test that can evaluate vent performance and characterize the health of the electrochemical cell under thermal runaway conditions. While thermal runaway and valve actuation are expected, can rupture should not occur. If can rupture does occur, there is a problem with the cell design and / or materials. One embodiment of the present disclosure addresses these shortcomings of existing electrochemical cell tests and meets these needs.

[0016] An embodiment can dynamically progress through all protection mechanisms built into the cell, something prior methods cannot do. For example, the cell's central gas vent, pressure relief valve, and other features can be observed during testing. That is, failure of these mechanisms leading to metal can collapse, jelly roll release, and casing rupture can actually be observed in embodiments of the thermal runaway pinpoint heating test. Embodiments can uncover defects in electrochemical cell design that may raise safety concerns for users, prove that the cell's safety mechanisms (e.g., current interrupt devices (CIDs)) operate as intended under thermal runaway conditions, and create internal short circuits without affecting cell integrity, as in tests that puncture, deform, bend, and / or crush the cell.

[0017] The thermal runaway pinpoint heating test has several advantages: It provides precise temperature control. The test is applied directly to the final cell product without any additional preparation as in some existing tests. The test allows for real-time data collection and visual observation. The test provides a quantitative measurement, and it is adaptable, simple, safe, reliable, fast, inexpensive, and reproducible.

[0018] FIGS. 1A and 1B illustrate the steps, operations, and features of a thermal runaway pinpoint heating test for an electrochemical cell. At 110, a heat source is applied to a portion of the electrochemical cell. One such electrochemical cell that can be used for the test is a lithium-ion battery. These electrochemical cells can be used in many products, such as computer laptops and electric vehicles. In one embodiment, the portion of the electrochemical cell, as illustrated at 112, comprises an electrochemical cell area that is less than 1% of the total area of ​​the electrochemical cell. In other embodiments, the heated portion can be less than or greater than 1% of the total area of ​​the electrochemical cell. The difference in total cell heating area for one embodiment of the present disclosure and prior standard heating methods is illustrated in FIG. 4. FIG. 4 illustrates four heating ranges (center side, corner side, bottom center side, and terminal side) and the difference in heating area 410. This heating of the electrochemical cell induces a thermal runaway condition in the electrochemical cell due to a localized internal short circuit. FIG. 2 illustrates a heat source 210 applied to a limited, concentrated, or pinpoint portion of an electrochemical cell 200. 2, in this particular embodiment, the heat source is directed at a specific portion or point 220 of the electrochemical cell 200, and the heat source is positioned in close proximity to, but not in physical contact with, the electrochemical cell 200 at a specific angle from the casing of the electrochemical cell. The heat source can be anything, such as a flame, a hot air heater, an electric heater, and / or a laser (113).

[0019] As shown at 115, a localized internal short circuit is caused by localized shrinkage of the separator / insulating layer 250 disposed between the negative electrode 240 and the positive electrode 260. In one embodiment, the localized internal short circuit involves a single negative electrode, a single positive electrode, and a single insulating layer (115A). In another embodiment, the localized internal short circuit involves no more than three negative electrodes, no more than three positive electrodes, and no more than two insulating layers (115B). In yet another embodiment, the localized internal short circuit consists of a number of negative electrodes, positive electrodes, and insulating layers that involve less than 1% of the total number of negative electrodes, positive electrodes, and insulating layers in the battery (115C). As shown at 116, a jelly roll internal short circuit can occur when the anode shrinks beyond the shrunken separator, causing a single point of failure with the cathode.

[0020] After a heat source is directed at the electrochemical cell in operation 110, it is then observed at 120 whether the electrochemical cell valves, bursts, or ruptures in response to the application of the heat source to a portion of the electrochemical cell.

[0021] In one embodiment, the system 300 of FIG. 3 can be used to apply a heat source to an electrochemical cell and to observe and determine whether the electrochemical cell has valved, split, or ruptured. The system 300 includes a chamber 310, a hot air generator 320, and a diffuser 330 that couples the hot air generator 320 to the chamber 310. The hot air generator has a temperature controller 325. The chamber 310 is fabricated from metal walls 311 and explosion-proof windows 312 and further includes an exhaust vent 313. Within the chamber 310 are a metal platform 314 and a sample holder 315. In one embodiment, the sample holder 315 includes one or more thermocouples. The sample holder 315 holds the electrochemical cell in place, and the thermocouples provide accurate temperature information for the sample electrochemical cell. The electrochemical cell to be tested is positioned within the chamber 310. The operations of FIGS. 1A and 1B are then performed on the electrochemical cell being tested. That is, the hot air generator applies heat to a pinpoint portion of the electrochemical cell through the diffuser. As previously described, this causes the electrochemical cell to go into thermal runaway due to a localized internal short circuit. The electrochemical cell is then observed through an explosion-proof window to determine whether the electrochemical cell has valved, split open, or exploded in response to the application of the heat source to a portion of the electrochemical cell.

[0022] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings illustrate, by way of example, specific embodiments that may be practiced. These embodiments are also referred to herein as "examples." Such examples may include elements in addition to those shown or described. However, examples that include the elements shown or described are also contemplated. Moreover, examples using any combination or permutation of those elements (or one or more aspects thereof) shown or described, whether with respect to the particular example (or one or more aspects thereof) or with respect to other examples (or one or more aspects thereof) shown or described herein, are also contemplated.

[0023] The publications, patents, and patent documents referenced in this document are incorporated herein by reference in their entirety, as if individually incorporated by reference. In the event of inconsistent usage between this document and those documents so incorporated by reference, the usage in the incorporated references is supplemental to that of this document, and in the event of an irreconcilable conflict, the usage in this document will control.

[0024] In this document, the words "a" or "an" are used, as is common in patent documents, to include one or more and are independent of any other instances or uses of "at least one" or "one or more." In this document, the word "or" is used to refer to a non-exclusive or, unless otherwise indicated, "A or B" includes "A and not B," "B and not A," and "A and B." In the appended claims, the words "including" and "in which" are used as plain English synonyms of the respective words "comprising" and "wherein." Also, in the following claims, the words "comprising" and "comprising" are open-ended, i.e., systems, apparatus, articles, or processes that include elements in addition to those listed after such words in a claim are still considered to fall within the scope of that claim. Moreover, in the following claims, the words "first," "second," and "third," etc. are used merely as labels and are not intended to suggest a numerical order to their objects.

[0025] The foregoing description is intended to be illustrative, not limiting. For example, the above examples (or one or more aspects thereof) may be used in combination with others. Other embodiments may be employed, such as by one of ordinary skill in the art upon reviewing the foregoing description. The Abstract is intended to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the foregoing Detailed Description, various features may be grouped together to simplify the disclosure. However, a claim may not recite every feature disclosed herein, as an embodiment may feature a subset of the above features. Moreover, an embodiment may include fewer features than those disclosed in a particular example. As such, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as an individual embodiment. The scope of the embodiments disclosed herein should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. [Explanation of symbols]

[0026] 200 electrochemical cells 210 Heat source 220 part 240 negative electrode 250 Separator / insulating layer 260 positive electrode 300 System 310 Chamber 311 metal wall 312 Explosion-proof window 313 Exhaust port 314 Metal Platform 315 Sample holder 320 Hot Air Generator 325 Temperature Controller 330 Diffuser 410 Heating area

Claims

1. 1. A process for testing an electrochemical cell, comprising: applying a heat source to a portion of the electrochemical cell through a diffuser that couples the heat source to the interior of the chamber through a wall of the chamber, the diffuser not physically contacting the electrochemical cell, thereby inducing a thermal runaway condition in the electrochemical cell due to a localized internal short circuit; determining whether the electrochemical cell has valved, burst, or ruptured in response to the application of the heat source to the portion of the electrochemical cell; wherein the portion of the electrochemical cell comprises an area of ​​the electrochemical cell that is less than 1% of the total area of ​​the electrochemical cell.

2. 10. The process of claim 1, wherein the localized internal short circuit comprises a single point of contact between the positive and negative electrodes.

3. 10. The process of claim 1, wherein the localized internal short circuit occurs in an internal or external jelly roll layer of the electrochemical cell.

4. The process of claim 1 , wherein the portion comprises a pinpoint portion.

5. 10. The process of claim 1, wherein the localized internal short circuit comprises a single negative electrode, a single positive electrode, and a single insulating layer.

6. 10. The process of claim 1, wherein the localized internal short circuit comprises no more than three negative electrodes, no more than three positive electrodes, and no more than two insulation layers.

7. 10. The process of claim 1, wherein the localized internal short circuit comprises a number of anodes, cathodes and insulation layers comprising less than 1% of the total number of anodes, cathodes and insulation layers in the battery.

8. 10. The process of claim 1, wherein the localized internal short circuit comprises a localized contraction of an insulating layer disposed between the negative electrode and the positive electrode.

9. The process of claim 1 , wherein the heat source comprises one or more of a flame, a hot air heater, an electric heater, and a laser.

10. A heat source and a chamber; a diffuser that couples the heat source to the interior of the chamber through a wall of the chamber; A system comprising: The system is operable to test an electrochemical cell, the testing comprising: positioning the electrochemical cell within the chamber; applying the heat source through the diffuser to a portion of the electrochemical cell without the diffuser physically contacting the electrochemical cell, thereby inducing a thermal runaway condition in the electrochemical cell due to a localized internal short circuit; determining whether the electrochemical cell has valved, burst, or ruptured in response to the application of the heat source to the portion of the electrochemical cell; The system wherein the portion of the electrochemical cell comprises an area of ​​the electrochemical cell that is less than 1% of a total area of ​​the electrochemical cell.

11. The system of claim 10 comprising a device for receiving the electrochemical cell, the device comprising a thermocouple.

12. The system of claim 10 , wherein the chamber comprises an explosion-proof window.

13. The system of claim 10 , wherein the portion comprises a pinpoint portion.

14. 11. The system of claim 10, wherein the localized internal short circuit comprises a single negative electrode, a single positive electrode, and a single insulating layer.

15. 11. The system of claim 10, wherein the localized internal short circuit includes no more than three negative electrodes, no more than three positive electrodes, and no more than two insulation layers.

16. 11. The system of claim 10, wherein the localized internal short circuit comprises a number of negative electrodes, positive electrodes and insulating layers comprising less than 1% of the total number of negative electrodes, positive electrodes and insulating layers in the electrochemical cell.

17. 11. The system of claim 10, wherein the localized internal short circuit comprises a localized contraction of an insulating layer disposed between the negative electrode and the positive electrode.

18. The system of claim 10 , wherein the heat source comprises one or more of a flame, a hot air heater, an electric heater, and a laser.

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