Trigger cell for triggering thermal runaway in the battery

Abstract

A system for testing thermal runaway in a battery cell includes a first layer of a first dielectric material at least partially wrapped around the battery cell, and a wire at least partially wrapped around the first layer of the first dielectric material. The system further includes a second layer of a second dielectric material at least partially wrapped around the wire, and a power supply configured to supply power to the wire. In this example, the first layer of the first dielectric material includes a polyimide film, and the second layer of the second dielectric material includes mica. The system further includes a temperature sensor in contact with the first layer, the second layer, and / or the battery cell. A controller receives a temperature reading from the temperature sensor and controls the power supplied to the wire by the power supply, at least partially based on the temperature reading.

Description

Technical Field

[0001]

[0001] This disclosure generally relates to battery technology, and more particularly to techniques for testing thermal runaway in a battery pack.

Background Art

[0002]

[0002] A battery is a common power source that provides direct current (DC) to a load, for example. A battery has a positive terminal or cathode and a negative terminal or anode. Multiple batteries can be connected in series and / or in parallel to form a high-voltage and / or high-power DC power source.

[0003]

[0003] A rechargeable battery can be charged and discharged, and such charge and discharge cycles can occur multiple times over the life of the battery. For example, when a battery is discharged during use, it can be recharged using an applied current, during which the original composition of the battery electrodes can be fully or at least partially restored by the reverse current. Examples of such rechargeable batteries include lead-acid batteries and lithium-ion batteries.

[0004]

[0004] Batteries can be used in many applications, such as in household electronic devices, wearable devices, computers, electric and non-electric vehicles, and / or many other devices or systems that use DC power. Several important issues remain regarding the operation of battery packs.

Brief Description of the Drawings

[0005] [Figure 1]

[0005] illustrates a flowchart that depicts a method of forming a trigger cell for triggering or causing thermal runaway in a battery cell and operating the trigger cell, according to an embodiment of the present disclosure. [Figure 2A]

[0006] Collectively illustrates trigger cells at various stages of formation and operation according to the method system of FIG. 1, according to an embodiment of the present disclosure. [Figure 2B] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2C] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2D1] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2D2] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2E1] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2E2] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2F1] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2F2] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2G1] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2G2] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2H1] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2H2] Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 2I]Figure 1 illustrates a collection of trigger cells at various stages of formation and operation according to the method system of the embodiments of this disclosure. [Figure 3A]

[0007] An example graph illustrating the temperature fluctuations over time when the trigger cell shown in Figure 2I is operated according to an embodiment of this disclosure is provided. [Figure 3B]

[0008] A graph illustrating the fluctuations in the power supplied to the heating wire of the trigger cell in Figure 2I during the operation of the trigger cell according to an embodiment of this disclosure is provided. [Modes for carrying out the invention]

[0006]

[0009] The drawings illustrate various embodiments of the present disclosure for illustrative purposes only and are not necessarily drawn to scale. Numerous variations, configurations, and other embodiments will become apparent from the following embodiments for carrying out the invention.

[0007]

[0010] A set of methods and systems for forming and operating a trigger cell capable of triggering thermal runaway in a battery cell is disclosed. Triggering thermal runaway in a battery cell allows testing the battery cell during a thermal runaway event. Such testing may include, for example, measuring parameters associated with thermal runaway in the battery cell and certifying the battery cell's thermal runaway handling capability. While the trigger cell may be advantageously used to test lithium-ion battery cells, the battery cell under test may be of another type, such as a lead-acid battery cell or a hydrogen cell.

[0008]

[0011] In one embodiment, a system for testing thermal runaway in a battery cell includes a trigger cell, which comprises a first layer of a first dielectric material at least partially wrapped around the battery cell, and a wire at least partially wrapped around the first layer of the first dielectric material. In the example, the wire comprises one or more metals. The wire is, for example, a nichrome wire, which comprises an alloy of nickel and chromium. Various exemplary layouts of the wire around the first layer of the first dielectric material are described below. The system further includes a second layer of a second dielectric material at least partially wrapped around the wire, and a power supply configured to supply power to the wire. In the example, the power supply is configured to supply power to the wire in order to heat the wire and induce thermal runaway in the battery cell. In the example, the first layer of the first dielectric material comprises a polyimide film, and the second layer of the second dielectric material comprises mica. In the example, the second layer of the second dielectric material has a lower thermal conductivity than the first layer of the first dielectric material.

[0009]

[0012] In one embodiment, the system further includes a temperature sensor in contact with at least one of the first layer, the second layer, and a battery cell. In some examples, a controller receives a temperature reading from the temperature sensor and controls the power supplied to the wire by a power source based at least in part on the temperature reading. In some such examples, the controller is configured to control the power supplied to the wire by a power source to maintain a constant or near-constant rise in the temperature reading. Numerous variations and embodiments will become apparent in light of this disclosure. General Overview

[0010]

[0013] As described above in this specification, several important issues remain regarding the operation of battery packs, such as lithium-ion battery packs. One challenge in lithium-ion battery technology is thermal management. The possibility of thermal runaway during use, handling, and / or transport of lithium-ion batteries is a continuing concern. Thermal runaway occurs when a series of self-sustaining exothermic side reactions lead to complete cell failure, and in some cases fire and / or explosion. A battery cell experiencing thermal runaway may emit hot gases, flames, and high-speed jets of molten particulate matter called ejecta. Lithium-ion batteries are susceptible to thermal runaway due to the chemical properties of lithium-ion technology. While significant progress has been made over time to improve cell performance (e.g., reduced capacity degradation, increased available power, etc.), the challenges of thermal runaway and its propagation remain. For example, the materials and structure of individual battery cells or battery packs can lead to localized hot spots or heating that result in cell failure. Also, excessive restraint of battery cells can result in large pressure gradients that lead to failure of mechanical components such as plates and fasteners around the battery cells. Similarly, failing to allow ejected material to escape can lead to the momentary formation of localized hot spots that can trigger thermal runaway in nearby battery cells. Therefore, the battery pack should be tested for thermal runaway conditions.

[0011]

[0014] Therefore, techniques for forming a trigger cell capable of triggering or inducing thermal runaway in a battery cell are described herein. For example, triggering thermal runaway in a battery cell allows testing the battery cell during a thermal runaway event and / or measuring parameters associated with thermal runaway in the battery cell, thereby enabling testing the thermal runaway handling capability of the battery cell. For example, a trigger cell is constructed to test the safety and robustness of a battery cell during a thermal runaway event. The battery cell on which the thermal runaway trigger mechanism is formed may be any suitable type of battery cell, such as a lithium-ion battery cell, a lead-acid battery cell, or a hydrogen cell.

[0012]

[0015] In the example, the trigger cell includes a first dielectric material that is at least partially wrapped around one or more sides of the battery cell. For example, in the orientation illustrated in the various figures described below, for example, as illustrated in Figure 2A, the top surface of the battery cell has a cathode, the bottom surface of the battery cell has an anode, and one or more sides (for example, on which the first dielectric material is wrapped) extend from the top surface to the bottom surface. In the example, the first dielectric material is wrapped around the sides of the battery cell using a suitable adhesive. In the example, the first dielectric material has relatively low electrical conductivity and relatively high thermal conductivity. For example, as described below, a wire is wrapped around the first dielectric material, and the low electrical conductivity ensures that adjacent windings of the wire are not electrically short-circuited by the first dielectric material. In the example, the heat generated by the wire is intended to reach the battery cell to heat the battery cell and trigger a thermal runaway in the battery cell. Therefore, in this example, the first dielectric material has a relatively high thermal conductivity to allow heat from the wire to reach the battery cell, for example, as described below. In this example, the first dielectric material may be able to withstand high temperatures such as at least 300°C, or at least 400°C, or at least 500°C, or at least 600°C, without substantially melting. High-temperature resistance prevents or at least reduces the opportunity for the dielectric material to melt during heating of the battery cell to trigger thermal runaway. In this example, the first dielectric material is a polyimide film such as insulating tape, for example, Kapton® tape.

[0013]

[0016] In one embodiment, a wire is applied on and around a first dielectric material, where the wire meanders around the first dielectric material and at least partially wraps around the first dielectric material. In an example, the wire is fixed on the first dielectric material using a suitable adhesive. Various exemplary layouts of the wire are described below. For example, FIG. 2D1 described below illustrates an exemplary first layout of the wire, and FIG. 2D2 described below illustrates an exemplary second layout of the wire.

[0014]

[0017] In an example, the lead or end section of the wire exits near the bottom surface of a battery cell comprising an anode. For example, during a malfunction of the battery cell (during a thermal runaway state or for another reason etc.), gas can be released by the battery cell, which is herein called the "outgassing" of the battery cell. For example, a pressure relief valve or membrane can be on or near the cathode or positive terminal of the battery cell, for example, on or near the top surface of the battery cell, where the pressure relief valve or membrane can rupture during an outgassing event etc., thereby releasing such gas. For example, an outgassing event can occur during a thermal runaway triggered by a trigger cell. For ventilation of such gas from or near the top surface of the battery cell, the end section of the wire exits from or near the bottom surface comprising the negative or anode terminal of the battery cell, as illustrated in FIGS. 2D1 and 2D2, for example, to avoid or reduce the chance of the end section of the wire coming into contact with the outgas. In one embodiment, the wire comprises a conductive material with a relatively high resistivity, and thus the wire can generate sufficient heat to trigger a thermal runaway in the battery cell. From this, the wire functions as a heating element in the trigger cell. In an example, a nichrome wire can be used, where nichrome comprises an alloy of, for example, nickel, chromium, and / or one or more other metals.

[0015]

[0018] In one embodiment, a temperature sensor is attached to the trigger cell. In an example, the temperature sensor exits, for example, near the bottom surface of the battery cell with an anode, due to the possibility of an outgassing event from the top surface of the battery cell, as described above. In an example, a thermocouple (such as a 30-gauge thermocouple) is used as the temperature sensor, but any other suitable type of temperature sensor may also be used.

[0016]

[0019] In an example, at least a portion of one or more sides of the battery cell is wound using a second dielectric material. From this, the second dielectric material wraps around the wire and secures the wire in place. In an example, the second dielectric material has a relatively low thermal conductivity. For example, the thermal conductivity of the second dielectric material is less than the thermal conductivity of the first dielectric material. The low thermal conductivity of the second dielectric material ensures that most of the heat generated by the wire remains confined within the second dielectric material and is transmitted to the battery cell through the first dielectric material with a relatively high thermal conductivity, thereby ensuring that the thermal runaway process is triggered. In an example, a dielectric material with a pressure-sensitive adhesive (PSA) such as mica with PSA is used as the second dielectric material.

[0017]

[0020] In one embodiment, during the operation of a trigger cell, a power supply applies a voltage V across the wires of the trigger cell to generate a current I in the wires. In this example, a controller adjusts the power delivered to the wires based on feedback of temperature T measured by, for example, a temperature sensor attached to the battery cell. The power supplied to the wires heats the wires (for example, a wire with relatively high resistance acts as a heating element), which then heats the battery cell and triggers thermal runaway in the battery cell. The power supply can control the power supplied to the wires of the trigger cell by, for example, adjusting the voltage V and / or current I applied to the wires of the trigger cell. The controller receives feedback of temperature T from the temperature sensor and adjusts the power supply based on temperature T. For example, the controller aims to ensure a relatively smooth rise in the temperature T of the battery cell (e.g., a constant or substantially constant temperature gradient) and therefore adjusts the power delivered to the wires. The controller aims to maintain a constant or substantially constant rise in temperature T to mimic a real battery cell thermal runaway condition in which the temperature can rise at a constant or substantially constant gradient. When a battery cell heats up to a certain level, it begins a self-heating process, which indicates the start of a thermal runaway condition. Once the self-heating process begins, the controller reduces the power supplied to the wires, and if thermal runaway occurs, it stops supplying any power.

[0018]

[0021] According to some embodiments of this disclosure, these various methods may be used individually or in combination to test a battery cell by triggering a thermal runaway event within the battery cell. Numerous variations and embodiments will become apparent based on this disclosure.

[0019]

[0022] Where used herein, the term “approximately” indicates that the listed values ​​may change to some extent or may otherwise be within acceptable tolerances, provided that the change does not result in a nonconformity of the process or device. For example, for some elements, the term “approximately” may refer to a variation of ±0.1%, while for other elements, the term “approximately” may refer to a variation of ±1%, ±10%, or any point within that range. Also, where used herein, a term defined in the singular is intended to include a term defined in the plural, and vice versa.

[0020]

[0023] Any reference to a numerical range in this specification explicitly includes each number (including fractions and positive integers) that is encompassed by that range. For example, a reference to a range of “at least 50” or “at least about 50” in this specification includes all positive integers and real numbers greater than or equal to 50, and a reference to a range of “less than 50” or “less than about 50” in this specification includes all positive integers and real numbers less than or equal to 49.

[0021]

[0024] As used herein, the terms “substantially” or “substantial” are equally applicable when used in a negative sense to refer to the complete or near-complete absence of an action, characteristic, feature, state, structure, item, or result. For example, a “substantially” flat surface would be either perfectly flat or nearly flat, with the same effect as if it were perfectly flat. method system

[0022]

[0025] Figure 1 illustrates a flowchart illustrating a method 100 for forming and operating a trigger cell 200 to trigger or cause thermal runaway of a battery cell 204, according to an embodiment of the present disclosure. Figures 2A, 2B, 2C, 2D1, 2D2, 2E1, 2E2, 2F1, 2F2, 2G1, 2G2, 2H1, 2H2, and 2I collectively illustrate the trigger cell 200 at various stages of formation and operation according to the method system 100 of Figure 1, according to an embodiment of the present disclosure. Figures 1 and 2A-2I are discussed together.

[0023]

[0026] As described, the trigger cell 200 is intended to trigger thermal runaway in a battery cell, for example, to test the battery cell during a thermal runaway event and / or to measure parameters associated with thermal runaway in the battery cell. For example, one challenge in battery technology (e.g., lithium-ion battery technology) is thermal management. The possibility of thermal runaway during use, handling, and / or transport of batteries such as lithium-ion batteries is a current concern. Thermal runaway occurs when a series of self-sustaining exothermic side reactions lead to complete failure of the cell, and possibly fire and / or explosion. A battery cell experiencing thermal runaway may emit hot gases, flames, and high-speed jets of molten particulate matter called ejecta. Lithium-ion batteries are susceptible to thermal runaway due to the chemical properties of lithium-ion technology. For example, the materials and structure of individual battery cells or battery packs can lead to localized hot spots or heating that result in cell failure. Also, excessive restraint of battery cells can result in large pressure gradients that lead to failure of mechanical components such as plates and fasteners around the battery cell. Similarly, preventing ejected material from escaping can lead to the momentary formation of localized hot spots that could trigger thermal runaway in nearby battery cells.

[0024]

[0027] Accordingly, Method 100 in Figure 1 illustrates an exemplary process for triggering thermal runaway in such a battery cell, for example, to test the thermal runaway handling capability of the battery cell. For example, as described below herein, a trigger cell 200 is constructed to test the safety and robustness of a battery cell against thermal runaway. The trigger cell 200 is a trigger mechanism for triggering thermal runaway in a battery cell, for example, to test the temperature at which thermal runaway occurs, to test whether the battery cell can withstand a certain temperature, and / or, in this example, to test one or more other parameters associated with thermal runaway in the battery cell 204.

[0025]

[0028] In method 100, 104, at least a portion of one or more sides 207 of the battery cell 204 is wrapped with a first layer 212 of dielectric material. In this example, the dielectric material 212 has a relatively high thermal conductivity (compared to, for example, the thermal conductivity of the dielectric material 250 described below). In this example, as illustrated, for example in Figure 2A, the top surface 205 of the battery cell 204 is the cathode, the bottom surface 206 of the battery cell 204 is the anode, and one or more sides 207 extend from the top surface 205 to the bottom surface 206.

[0026]

[0029] In the example shown in Figure 2A, the battery cell 204 is cylindrical in shape. Therefore, the battery cell 204 has a single side surface 207 extending between the top surface 205 and the bottom surface 206. However, in other examples, the battery 204 can have a different shape. For example, the top surface 205 and bottom surface 206 of the battery cell 204 may be square, rectangular, triangular, or oval in shape. In some such examples, multiple sides may extend between the top and bottom surfaces. More generally, the battery cell 204 may be of appropriate size and may have any appropriate shape or form factor that may be specific to the application.

[0027]

[0030] In one embodiment, the battery cell 204 may be any suitable type of battery cell. For example, the battery cell 204 may be a lithium-ion battery cell, but it may be another suitable type such as a lead-acid battery cell or a hydrogen cell. In one embodiment, the battery cell 204 contains an electrolyte in a corresponding container, although the electrolyte is not illustrated in Figure 2A. The battery cell may be contained within an enclosure such as a plastic enclosure or a metal enclosure. Such an enclosure may house or contain other components in addition to the battery cell 204.

[0028]

[0031] Figure 2B illustrates an example of a first layer 212 of dielectric material adjacent to a battery cell 204, and Figure 2C illustrates a first layer 212 of dielectric material wrapped around a side 207 of the battery cell 204. In the example, the dielectric material 212 is fixed to the side 207 via an adhesive. In the example, the dielectric material 212 is an insulating tape such as Kapton® tape or a polyimide film. In some cases, the first layer 212 of dielectric material completely covers the side 207, while in other cases, the first layer 212 of dielectric material may only partially cover the side 207 (for example, covering substantially all of the main central portion of the side 207 but not the edges near 205 and 206). In yet another case, the first layer 212 of dielectric material may cover the side 207 like a barber pole, with alternating covered and uncovered portions of the side 207.

[0029]

[0032] In this example, the thermal conductivity of the dielectric material 212 is at least 0.3 W / mK (watts / meter-kelvin), or at least 0.4 W / mK, at least 0.6 W / mK, at least 0.8 W / mK, or at least 1 W / mK. From this, heat can be transferred through the first layer 212 of the dielectric material to the battery cell under test, as will be described below.

[0030]

[0033] In this example, the dielectric material 212 may be able to withstand high temperatures such as at least 300°C, or at least 400°C, or at least 500°C, or at least 600°C, without substantially melting. This high-temperature resistance prevents, or at least reduces, the opportunity for the dielectric material 212 to melt during thermal runaway of the battery cell 204. Furthermore, the dielectric material 212 will prevent short circuits of the heating wires applied later, as described below.

[0031]

[0034] It should be noted that the dielectric material 212 is not wrapped around the battery cell 204 during normal or regular operation of the battery cell 204, or is otherwise part of the battery cell 204. Rather, the dielectric material 212 is wrapped around the battery cell 204 for the purpose of forming a trigger cell 200 while testing the battery cell 204 for thermal runaway.

[0032]

[0035] The dielectric material 212 can provide several advantages. For example, the dielectric material 212 can form both a heat path to the battery cell 204 and an electrical barrier layer between the battery cell 204 and the subsequently added heating wire 220. Thus, heat from the wire 220 can be effectively transferred to the battery cell 204 due to the relatively high thermal conductivity of the dielectric material 212, and the loops of the wire 220 cannot be electrically short-circuited due to the electrical insulating properties of the dielectric material 212. For example, if any outer jacket or layer of the battery cell 204 melts during testing, the first layer 212 of the dielectric material can prevent its molten material from short-circuiting a portion of the subsequently applied heating wire, as illustrated in Figure 108.

[0033]

[0036] Method 100 then proceeds to steps 104 through 108. In step 108, the wire 220 is applied to and around the first layer 212 of the dielectric material, where the wire 220 meanders around the dielectric material 212 and at least partially wraps around the first layer 212 of the dielectric material. In the example, the lead or end section of the wire 220 emerges near the bottom surface 206 of the battery cell 204 having an anode. In the example, the wire 220 is secured to the first layer 212 of the dielectric material using an adhesive or other suitable fastener.

[0034]

[0037] Figure 2D1 illustrates one exemplary shape of wire 220a wound around dielectric material 212, and Figure 2D2 illustrates another exemplary shape of wire 220b wound around dielectric material 212. Referring to Figure 2D1, wire 220a has end sections or leads 221a and 222a that emerge near the bottom surface 206, which has the negative terminal or anode terminal of the battery cell 204. Thus, end sections 221a and 222a are closer to the anode than to the cathode of the battery cell.

[0035]

[0038] During a malfunction of a battery cell (such as during a thermal runaway condition or for other reasons), gas may be released by the battery cell, which is referred to herein as “outgassing” of the battery cell. For example, a pressure relief valve or membrane may be on or near the cathode or positive terminal of the battery cell 204, for example, on or near the top surface of the battery cell 204, where the pressure relief valve or membrane may rupture during an outgassing event, thereby releasing such gas. For example, an outgassing event may occur during a thermal runaway triggered by the trigger cell 200. To allow such gas to escape from or near the top surface of the battery cell 204, the end sections of the wire or leads 221a and 222a exit from or near the bottom surface 206, which has the negative terminal or anode terminal of the battery cell 204, as illustrated in Figure 2D1, to avoid or reduce the opportunity for leads 221a, 222a to come into contact with the outgassing.

[0036]

[0039] As further shown in Figure 2D1, the wire 220a comprises a plurality of extending sections 226 and a plurality of loop sections 225. For example, the extending section 226 extends from near the bottom surface 206 (e.g., anode) of the battery cell 204 toward the top surface 205 (e.g., cathode) of the battery cell 204. Near the top surface 205, the wire 220a loops back or turns in the loop section 225, where it extends from near the top surface 205 of the battery cell 204 toward the bottom surface 206 of the battery cell 204. Such extending and loopback portions of the wire 220a continue so that the wire 220a covers a large area of ​​the dielectric material 212.

[0037]

[0040] In the example, in or near the loop section 225, a dielectric material adhesive tape 224 (for example, it may be the same as or different from the dielectric material 212) is used to attach the ends of individual extending sections to the first layer 212 of the dielectric material. For example, Figure 2D1 further illustrates a magnified view of a section of wire 220a and shows two such examples of adhesive tape 224. The adhesive tape 224 holds the wire 220a in place and, for example, attaches the wire 220a to the dielectric material 212. In another example, other suitable methods may be used to fix the wire 220a in place to the dielectric material 212.

[0038]

[0041] Referring here to Figure 2D2, another exemplary shape of the wire 220b wound around the dielectric material 212 is illustrated. Similar to that shown in Figure 2D1, the wire 220b shown in Figure 2D2 has end sections or leads 221b and 222b that emerge near the bottom surface 206, which has the negative or anode terminal of the battery cell 204. The relevant explanations above regarding lead positioning and outgassing are equally applicable here as well.

[0039]

[0042] As further illustrated in Figure 2D2, the wire 220b has a vertical spiral or spring shape and is wound around the battery cell 204. For example, starting from end 221b, the wire 220b forms multiple loops around the battery cell 204, traversing from near the bottom surface 206 toward the top surface 205 of the battery cell 204, as illustrated. Once the loops reach near the top surface 205 of the battery cell 204, section 229 of the wire 220b extends from near the top surface 205 of the battery cell 204 to end section 222b near the bottom surface 206 of the battery cell 204.

[0040]

[0043] In one embodiment, to avoid an electrical short circuit between section 229 of wire 220b and the loop of wire 220b, section 229 of wire 220b and the loop of wire 220b are separated by a dielectric adhesive tape 228, such as a polyimide film tape, for example, Kapton® tape. Although the tape 228 is illustrated as translucent in Figure 2D2 to show the loop of wire 220b directly beneath the tape 228, in actual implementations of the trigger cell 200, the tape 228 may not be translucent in this example.

[0041]

[0044] In one embodiment, wires 220a and / or 220b are made of a conductive material with relatively high resistivity so that when current flows through wires 220a and / or 220b, or when heat is applied to wires 220a and / or 220b in a different manner, wires 220a and / or 220b can generate sufficient heat to trigger thermal runaway in the battery cell 204. Nichrome wire may be used in an example.

[0042]

[0045] Nichrome comprises a family of alloys, for example, nickel and chromium, and / or iron. In some examples, nichrome may also contain one or more other elements. Nichrome is also called NiCr, nickel-chromium, or chromium-nickel. Nichrome is used as a resistive wire in heating applications and can be used, for example, as a heating element. Nichrome alloys, for example, consist of 80 mass% nickel and 20 mass% chromium, but other combinations of nickel and chromium (and / or one or more other metals) are also possible. In the example, wires 220a and / or 220b have an electrical resistivity of, for example, at least 80 μΩ-cm, or at least 100 μΩ-cm, or at least 110 μΩ-cm. In the example, 30 gauge nichrome wire may be used. In another example, thin copper wire and / or other suitable wires may also be used, which can be used as a heating element.

[0043]

[0046] Figures 2D1 and 2D2 illustrate two exemplary layouts of the wire, but the wire 220 can have several other layouts suitable for heating the battery cell 204, for example, insofar as the wire 220 is at least partially wound around the dielectric material 212 and is capable of heating the battery cell 204. In another example, the wire 220 may be replaced by another suitable heating device. For example, a flexible printed circuit board (PCB) containing heating elements may be used instead of the wire 220. For example, the flexible PCB may be wound around the dielectric material 212 and the battery cell 204. Conductive traces on the flexible PCB can, in this example, function as heating elements for heating the battery cell.

[0044]

[0047] Referring again to Figure 1, method 100 then proceeds to steps 108 through 112. In step 112, the temperature sensor 230 is attached to the trigger cell 200. In this example, the temperature sensor 230 is located near the bottom surface 206 of the battery cell 204, which has an anode, due to a possible outgassing event from the top surface 205 of the battery cell 204, for example, as described above. In this example, a thermocouple (such as a 30-gauge thermocouple) is used as the temperature sensor, but any other suitable type of temperature sensor may be used.

[0045]

[0048] For example, Figure 2E1 illustrates an exemplary location of the temperature sensor 230 relative to wire 220a, and Figure 2E2 illustrates an exemplary location of the temperature sensor 230 relative to wire 220b. In one example, the temperature sensor 230 may be located on the bottom surface 206 of the battery cell 204, as illustrated in the example in Figure 2E2. Thus, the temperature sensor 230 may be in contact with one or more of the battery cell 204 (as shown in Figure 2E2), the dielectric material 212, and the dielectric material 250 (described below).

[0046]

[0049] In the example, as illustrated in Figures 2F1 and 2F2, dielectric material adhesive tape 231 can be applied to the end sections of wires 221 and 222 and the end section of thermocouple 230 to fix them together (for example, so that they do not move substantially relative to each other), thereby reducing the chance of accidental electrical short circuits between them. The adhesive tape 231 can be any suitable tape, such as polyimide film tape, for example, Kapton® tape.

[0047]

[0050] Referring again to Figure 1, method 100 proceeds from 112 to 116. In 116, at least a portion of one or more sides of the battery cell 204 is wrapped using the second layer 250 of dielectric material such that the wire 220 is between the first layer 212 of dielectric material and the second layer 250 of dielectric material. For example, Figure 2G1 illustrates the second dielectric material 250 adjacent to a battery cell 204 having wire 222a, and Figure 2G2 illustrates the second dielectric material 250 wrapped around the battery cell 204 having wire 222a. Similarly, Figure 2H1 illustrates the second dielectric material 250 adjacent to a battery cell 204 having wire 222b, and Figure 2H2 illustrates the second dielectric material 250 wrapped around the battery cell 204 having wire 222b.

[0048]

[0051] In Figures 2G2 and 2H2, the dielectric material 250 is illustrated as translucent to show the wires and thermocouples beneath it; however, in the actual implementation of the trigger cell 200, the dielectric material 250 may not be translucent in the example.

[0049]

[0052] In this example, the dielectric material 250 has a relatively low thermal conductivity. For example, the thermal conductivity of the dielectric material 250 is less than that of the dielectric material 212. The low thermal conductivity of the dielectric material 250 ensures that most of the heat generated by the wire 220a and / or 220 remains trapped or is otherwise directed inward and transferred to the battery cell 204 through the first layer 212 of the dielectric material, which has a relatively high thermal conductivity. Thus, the second layer 250 of the dielectric material acts as a thermal barrier, not only preventing or reducing heat from escaping from the wire 220 to the battery cell 204, but also holding the wire 220 firmly in place.

[0050]

[0053] In the example, a dielectric material with pressure-sensitive adhesive (PSA) is used for the dielectric material 250, so that the dielectric material 250 can be easily wrapped around the battery cell 204. An exemplary material is mica, such as mica with PSA. For example, the thermal conductivity of the dielectric material 250 (e.g., perpendicular to the plane of the dielectric material 250) may be, for example, at most 0.2 W / mK, or at most 0.3 W / mK, or at most 0.5 W / mK, or at most 1 W / mK, or at most 2 W / mK. For example, muscovite mica has a thermal conductivity of about 0.3 W / mK (e.g., perpendicular to the plane of the mica sheet). As described above, for example, the thermal conductivity of the dielectric material 250 is less than that of the dielectric material 212.

[0051]

[0054] In some cases, the second layer 250 of dielectric material completely covers the wire 220 and the underlying first layer 212 of dielectric material, while in other cases, the second layer 250 of dielectric material may only partially cover the wire 220 and / or the underlying first layer 212 of dielectric material. As described, one advantage of the second layer 250 of dielectric material is that it traps heat to induce thermal runaway in the battery cell under test, and thus complete covering serves this purpose.

[0052]

[0055] The system 200 resulting from Figure 2G2 and / or 2H2 is a trigger cell that can be used to test for thermal runaway of the battery cell 204. Either the trigger cell of Figure 2G2 or 2H2 may be used, where the difference between these two trigger cells is the way the wire 220 is wrapped around the battery cell 204. As described, two exemplary ways of wrapping the wire 220 around the battery cell 204 are illustrated in Figures 2A–2H2, but in another example, the wire 220 may be wrapped in another suitable way.

[0053]

[0056] Therefore, processes 104, 108, 112, and 116 of Method 100 describe the formation of an exemplary trigger cell for triggering thermal runaway in the battery cell 204. Subsequent process 120 of Method 100 describes the operation of the trigger cell.

[0054]

[0057] Referring again to Figure 1, method 100 proceeds from 116 to 120. In 120, a voltage V (e.g., by power supply 272) is applied across the wire 220 of the trigger cell 200, generating a current I in the wire 220, and the controller 270 triggers a thermal runaway in the battery cell by adjusting the power delivered to the wire 220 based on feedback of temperature T measured by, for example, a temperature sensor attached to the battery cell 204. Figure 2I illustrates an exemplary arrangement of the controller 270 and power supply 272. The power supply 272 can control the power supplied to the wire 220 of the trigger cell 200 by, for example, adjusting the voltage V and / or current I applied to the wire 220 of the trigger cell 200. The controller 270 receives temperature T from temperature sensor 230 and adjusts the power supply 272 based on temperature T.

[0055]

[0058] Although not illustrated, in some examples, the controller 270 includes, or is coupled to, a communication chip for communicating with, for example, the temperature sensor 230. In one embodiment, the controller 270 includes a microprocessor coupled to a computer-readable storage medium such as memory or a data storage device. In one embodiment, the computer-readable storage medium stores instructions or code, when executed by the microprocessor, that cause the microprocessor to perform an operation to adjust the power supply unit 272 based on temperature T, as described herein. In another example, the controller 270 may be implemented using a suitable hardware circuit configuration.

[0056]

[0059] In one example, process 120 for triggering thermal runaway is performed when the battery cell 204 is inoperable. In another example, process 120 for triggering thermal runaway is performed when the battery cell 204 is operational, for example, when it is supplying power to a load. In the example, when the battery cell 204 is supplying power to a load and process 120 is performed, the operation of the battery cell 204 may contribute to some additional heating from internal losses in addition to heating by the wire 220. In yet another example, the battery cell 204 may be undergoing a charging process, for example, when process 120 for triggering thermal runaway is performed. In yet another example, when process 120 for triggering thermal runaway is performed, the charge state of the battery cell 204 may be in the range of 0% to 100%. Thus, process 120 for triggering thermal runaway can be performed in any operating, non-operating, and / or charged state of the battery cell 204 in the example.

[0057]

[0060] Figure 3A illustrates a graph 304 showing the temperature fluctuations over time when the trigger cell 200 of Figure 2I is in operation according to an embodiment of the present disclosure. Figure 3B illustrates a graph 308 showing the fluctuations in the power supplied to the heating wire 220 of the trigger cell 200 of Figure 2I during operation of the trigger cell 200 according to an embodiment of the present disclosure.

[0058]

[0061] Referring to Graphs 304 and 308, before time t0, no power is applied to the wire 220 of the trigger cell 200, and the temperature T is the ambient temperature. From time t0 onward, power is applied to the wire 220 of the trigger cell 200, resulting in an increase in temperature T. For example, since the wire 220 is a heating element with relatively high resistivity, the temperature of the wire 220 rises along with the power supplied to the wire 220.

[0059]

[0062] As illustrated in graphs 304 and 308, the controller 270 aims to ensure a relatively smooth rise in the temperature T of the battery cell 204 (e.g., a constant or substantially constant temperature slope), and therefore adjusts the power delivered to the wire 220. Hence, the power delivery graph 308 is not smooth and has peaks and valleys. The controller 270 aims to maintain a constant or substantially constant rise in temperature T, for example, to simulate a real battery cell thermal runaway condition, where the temperature may rise at a constant or substantially constant slope.

[0060]

[0063] Up to time t1 (see graph 308), the average power increases, and the power supplied to wire 220 heats wire 220, which in turn raises the temperature inside battery cell 204. From time t1, controller 270 starts to decrease the average power, for example, because from time t1 onwards, battery cell 204 begins a self-heating process that indicates the start of a thermal runaway state. Self-heating continues until time t2, and the power gradually decreases from time t1 to time t2. At time t2, thermal runaway occurs inside battery cell 204, which is indicated by a rapid increase in temperature T.

[0061]

[0064] It should be noted that the process in Method 100 in Figure 1 is shown in a specific order for the sake of clarity. However, one or more of the processes may be performed in a different order or not at all, according to some embodiments (i.e., they may be optional). Based on this disclosure, numerous variations of Method 100 and the techniques described herein will become apparent. Further exemplary embodiments

[0062]

[0065] The following examples illustrate further embodiments, from which numerous substitutions and configurations will become apparent.

[0063]

[0066] Example 1. A system for testing thermal runaway in a battery cell, comprising: a first layer of a first dielectric material at least partially wrapped around the battery cell; a wire comprising one or more metals at least partially wrapped around the first layer of the first dielectric material; a second layer of a second dielectric material at least partially wrapped around the wire; and a power supply configured to supply power to the wire.

[0064]

[0067] Example 2. The system according to Example 1, further comprising a temperature sensor in contact with the first layer, the second layer, and / or the battery cell.

[0065]

[0068] Example 3. The system according to Example 2, further comprising a controller configured to receive temperature readings from a temperature sensor and to control the power supplied to a wire by a power supply, at least in part, based on the temperature readings.

[0066]

[0069] Example 4. The system as in Example 3, wherein the controller is configured to control the power supplied to the wire by a power source, the power supplied to the wire generates heat, and the controller controls the power supply so that the temperature reading from the temperature sensor maintains a substantially constant rate of change.

[0067]

[0070] Example 5. The system according to Example 3 or 4, wherein the controller is configured to stop supplying power to the power supply or reduce the amount of power supplied to the wires in response to thermal runaway being triggered in the battery cell.

[0068]

[0071] Example 6. The system described in any one of Examples 1-5, wherein the power supply is configured to provide power to the wires to heat them up and cause thermal runaway in the battery cells.

[0069]

[0072] Example 7. The system according to any one of Examples 1 to 6, wherein the wire comprises a first extending section extending from near the anode of the battery cell to near the cathode of the battery cell, a second extending section extending from near the cathode of the battery cell to near the anode of the battery cell, and a loopback section connecting the first extending section and the second extending section.

[0070]

[0073] Example 8. The system according to any one of Examples 1 to 7, wherein the wire has a first end section and a second end section that are closer to the anode of the battery cell and further away from the cathode of the battery cell.

[0071]

[0074] Example 9. The system according to any one of Examples 1 to 8, wherein the wire is arranged in a vertical spiral around a battery cell, the vertical spiral having a first end near the anode of the battery cell and a second end near the cathode of the battery cell, the first end section of the wire is coupled to the first end of the vertical spiral to the power source such that the first end section of the wire is closer to the anode than to the cathode, the second end section of the wire is coupled to the second end of the vertical spiral to the power source, and the second end section of the wire is positioned at least partially above the vertical spiral and separated from the vertical spiral by a third layer of dielectric material.

[0072]

[0075] Example 10. The system described in any one of Examples 1-9, wherein the wire is a nichrome wire comprising nickel and chromium.

[0073]

[0076] Example 11. The system according to any one of Examples 1 to 10, wherein the second layer of the second dielectric material has a lower thermal conductivity than the first layer of the first dielectric material.

[0074]

[0077] Example 12. The system according to any one of Examples 1 to 11, wherein the first layer of the first dielectric material comprises a polyimide film, and the second layer of the second dielectric material comprises mica.

[0075]

[0078] Example 13. A method for forming and operating a thermal runaway trigger cell for a battery cell, the method comprising: wrapping a first layer of a first dielectric material at least partially around the surface of a battery cell, wherein the surface extends from the cathode to the anode of the battery cell; wrapping a wire at least partially around the first layer of the first dielectric material; wrapping a second layer of a second dielectric material at least partially around the wire; and coupling the wire to a power source.

[0076]

[0079] Example 14. The method according to Example 13, further comprising positioning a temperature sensor in contact with at least one of the first layer, the second layer, and the battery cell.

[0077]

[0080] Example 15. The method according to Example 13 or 14, further comprising supplying power from a power source to the wire to heat it and cause thermal runaway in the battery cell.

[0078]

[0081] Example 16. The method according to any one of Examples 13-15, further comprising: positioning a temperature sensor in contact with at least one of the first layer, the second layer, and the battery cell; supplying power from a power source to the wire to heat the wire and cause thermal runaway in the battery cell; and adjusting the power from the power source to the wire based at least partially on the output of the temperature sensor.

[0079]

[0082] Example 17. The method of Example 16, wherein the power from the power source to the wire is regulated such that (i) at least a portion of the temperature rise has a constant or substantially constant slope, and (ii) the power supply is reduced or removed in response to thermal runaway occurring in the battery cell, or both.

[0080]

[0083] Example 18. A system for testing a battery cell, comprising a wire having one or more metals, at least partially wrapped around the battery cell; an electrical barrier layer between the wire and the battery cell; and a thermal barrier layer on the wire.

[0081]

[0084] Example 19. The system according to Example 18, further comprising a thermocouple for measuring the temperature rise of the battery cells.

[0082]

[0085] Example 20. The system according to Example 19, further comprising a power supply unit for supplying power to a wire and a controller for adjusting the power supplied to the wire, at least in part, based on temperature readings from a thermocouple.

[0083]

[0086] The foregoing description of exemplary embodiments has been presented for illustrative and explanatory purposes only. It is not intended to be exhaustive or to limit this disclosure to the very forms disclosed. Many modifications and variations are possible based on this disclosure. The scope of this disclosure is intended to be limited not by the forms for carrying out the invention, but rather by the claims appended herein. Future applications claiming priority to this application may assert the disclosed subject matter in different ways and may generally include any set of one or more limitations as variously disclosed or otherwise demonstrated herein.

Claims

1. This is a system for testing thermal runaway in battery cells. A first layer of a first dielectric material, at least partially wrapped around the battery cell, A wire comprising one or more metals, at least partially wound around a first layer of the first dielectric material, A second layer of a second dielectric material, at least partially wrapped around the wire, A power supply configured to supply power to the aforementioned wire A system equipped with these features.

2. The temperature sensor in contact with the first layer, the second layer, and / or the battery cell. The system according to claim 1, further comprising the following:

3. A controller configured to receive temperature readings from the temperature sensor and to control the power supplied to the wire by the power supply based at least partially on the temperature readings. The system according to claim 2, further comprising the above.

4. The system according to claim 3, wherein the controller is configured to control the power supplied to the wire by the power supply, the power supplied to the wire generates heat, and the controller controls the power supply so that the temperature reading from the temperature sensor maintains a substantially constant rate of change.

5. The system according to claim 3, wherein the controller is configured to stop supplying power to the power supply or reduce the amount of power supplied to the wire in response to the thermal runaway being triggered in the battery cell.

6. The system according to claim 1, wherein the power supply is configured to supply power to the wire in order to heat the wire and cause thermal runaway in the battery cell.

7. The aforementioned wire is A first extending section extending from near the anode of the battery cell to near the cathode of the battery cell, A second extending section extending from near the cathode of the battery cell to near the anode of the battery cell, A loopback section connecting the first extended section and the second extended section The system according to claim 1, comprising:

8. The system according to claim 1, wherein the wire has a first end section and a second end section that are closer to the anode of the battery cell and further away from the cathode of the battery cell.

9. The wire is arranged in a vertical spiral around the battery cell. The vertical helix has a first end near the anode of the battery cell and a second end near the cathode of the battery cell. The first end section of the wire is connected to the power supply such that the first end section of the wire is closer to the anode than to the cathode. The second end section of the wire connects the second end of the vertical spiral to the power supply. The second end section of the wire is positioned at least partially above the vertical helix and is separated from the vertical helix by a third layer of dielectric material. The system according to claim 1.

10. The system according to claim 1, wherein the wire is a nichrome wire comprising nickel and chromium.

11. The system according to claim 1, wherein the second layer of the second dielectric material has a lower thermal conductivity than the first layer of the first dielectric material.

12. The system according to claim 1, wherein the first layer of the first dielectric material comprises a polyimide film, and the second layer of the second dielectric material comprises mica.

13. A method for forming and operating a thermal runaway trigger cell for a battery cell, wherein the method is: A first layer of a first dielectric material is wrapped at least partially around the surface of the battery cell, wherein the surface extends from the cathode to the anode of the battery cell. The first dielectric material is wrapped at least partially around the first layer, The method involves winding at least a portion of a second layer of the second dielectric material around the wire, Connecting the aforementioned wire to the power supply and A method that includes [a certain feature].

14. The temperature sensor is positioned to be in contact with at least one of the first layer, the second layer, and the battery cell. The method according to claim 13, further comprising the above.

15. To heat the wire and cause thermal runaway in the battery cell by supplying power to the wire from the power source. The method according to claim 13, further comprising the above.

16. The temperature sensor is positioned to be in contact with at least one of the first layer, the second layer, and the battery cell, Power is supplied from the power source to the wire in order to heat the wire and cause thermal runaway in the battery cell, Adjusting the power from the power supply to the wire based at least partially on the output of the temperature sensor. The method according to claim 13, further comprising the above.

17. Adjusting the power from the power source to the wire is, The method according to claim 16, comprising: (i) adjusting the power from the power source to the wire such that at least a portion of the temperature rise has a constant or substantially constant slope, and (ii) the power supply is reduced or removed in response to thermal runaway occurring in the battery cell, or both.

18. A system for testing battery cells, A wire comprising one or more metals, at least partially wrapped around the battery cell, The electrical barrier layer between the wire and the battery cell, The thermal barrier layer on the wire and A system equipped with these features.

19. Thermocouple for measuring the temperature rise of the battery cell The system according to claim 18, further comprising the following:

20. A power supply unit for supplying power to the aforementioned wire, A controller for adjusting the power supplied to the wire based at least partially on the temperature reading from the thermocouple. The system according to claim 19, further comprising the above.

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