WO2021059206A1

WO2021059206A1 - Detection and capture of fluorine containing toxic byproducts of electrochemical cell packs

Info

Publication number: WO2021059206A1
Application number: PCT/IB2020/058962
Authority: WO
Inventors: Bamidele O. FAYEMI; Tyler S. MATTHEWS; Steven Y. Yu
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2019-09-27
Filing date: 2020-09-24
Publication date: 2021-04-01
Anticipated expiration: 2022-03-27
Also published as: TW202130403A

Abstract

A system includes an electrochemical cell pack. The electrochemical cell pack includes a housing having an interior space; a plurality of electrochemical cells disposed within the interior space; and a thermal management fluid disposed within the interior space such that the electrochemical cell is in thermal communication with the thermal management fluid. The system further includes a vent assembly comprising a flow control mechanism and a filter assembly disposed downstream of the flow control mechanism. The flow control mechanism is configured to enable fluid communication between the interior space of the housing and the filter assembly upon a condition within the interior space exceeding a predetermined threshold value. The filter assembly comprises an absorbent or adsorbent filter configured to remove one or more fluorine containing toxic components from a fluid stream passing through the vent assembly.

Description

DETECTION AND CAPTURE OF FLUORINE CONTAINING TOXIC BYPRODUCTS OF ELECTROCHEMICAL CELL PACKS

FIELD The present disclosure relates to the capture of byproducts generated during use of electrochemical cell packs.

SUMMARY

In some embodiments, a system is provided. The system includes an electrochemical cell pack. The electrochemical cell pack includes a housing having an interior space; a plurality of electrochemical cells disposed within the interior space; and a thermal management fluid disposed within the interior space such that the electrochemical cell is in thermal communication with the thermal management fluid. The system further includes a vent assembly comprising a flow control mechanism and a filter assembly disposed downstream of the flow control mechanism. The flow control mechanism is configured to enable fluid communication between the interior space of the housing and the filter assembly upon a condition within the interior space exceeding a predetermined threshold value. The filter assembly comprises an absorbent or adsorbent filter configured to remove one or more fluorine containing toxic components from a fluid stream passing through the vent assembly.

The above summary of the present disclosure is not intended to describe each embodiment of the present disclosure. The details of one or more embodiments of the disclosure are also set forth in the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. l is a schematic diagram of a system for detecting and capturing toxic byproducts of an electrochemical cell pack according to some embodiments of the present disclosure.

FIG. 2 is a schematic cross-sectional view of an adsorbent filter according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Electrochemical cells (e.g., lithium-ion batteries) are in widespread use worldwide in a vast array of electronic and electric devices ranging from hybrid and electric vehicles to power tools, portable computers, and mobile devices.

Direct contact liquid cooling of electrochemical cells has been identified as a means of improving thermal performance. Desired properties for direct contact cooling fluids include low electrical conductivity, and low or non-flammability (i.e. no flash point). Many fluorinated hydrocarbons, such as partially or fully fluorinated fluorocarbons, fluoroethers, fluoroketones, and fluoroolefms have such desired properties.

Thermal stability at typical use temperatures is also desirable for the reliability of the cooling fluid over the intended life of the electrochemical cell. However, some electrochemical cells, such as Li-ion cells, may undergo a process known as thermal runaway upon overheating, overcharging, or mechanical penetration. Once the threshold for thermal runway is reached, the electrochemical cell may go through rapid self-heating, venting, and ignition of high temperature, flammable cell components (e.g., electrolyte) in the presence of oxygen. Electrochemical cell surface temperatures during thermal runaway may exceed 500°C. In direct contact cooled cells, this implies that the cooling fluid may be subjected to these elevated temperatures for some duration of time. At such temperatures, certain fluorinated fluids may decompose to form toxic decomposition products such as hydrogen fluoride and carbonyl fluoride. In automotive applications, vehicle operators, passengers, or first responders can potentially be exposed to these materials when systems vent to relieve overpressure. Consequently, systems and methods for (i) controlling the vent path and capturing toxic decomposition products from the exhaust stream during pressure relief; (ii) determining whether toxic byproducts have been vented from battery pack and/or whether the toxic byproduct filter is still active (i.e. filtration capacity is not exhausted); and/or (iii) alerting the vehicle operator of the potential occurrence of electrochemical cell thermal runaway in cases where there are no obvious signs, are desirable.

Generally, the present disclosure relates to such systems and methods. Benefits and characteristics of the systems and methods may include:

• Reliable detection and capture of toxic materials under conditions of high pressure, temperature and/or other adverse conditions.

• Fully automated detection and capture without sensory input or visual inspection by the operator of a device being powered by the electrochemical cell

As used herein, "fluoro-" (for example, in reference to a group or moiety, such as in the case of "fluoroalkylene" or "fluoroalkyl" or "fluorocarbon") or "fluorinated" means (i) partially fluorinated such that there is at least one carbon-bonded hydrogen atom, or (ii) perfluorinated.

As used herein, "perfluoro-" (for example, in reference to a group or moiety, such as in the case of "perfluoroalkylene" or "perfluoroalkyl" or "perfluorocarbon") or "perfluorinated" means completely fluorinated such that, except as may be otherwise indicated, there are no carbon-bonded hydrogen atoms replaceable with fluorine.

As used herein, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

As used herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

In some embodiments, the present disclosure relates to system for detecting and capturing toxic byproducts of an electrochemical cell pack. With reference to FIG. 1, the system 10 may include one or more electrochemical cell packs 20 fluidically and operably coupled to a vent assembly 30 that includes a series of components configured to detect and capture toxic byproducts produced within the electrochemical cell pack 20.

In some embodiments, the electrochemical cell packs 20 may include a housing 35 that contains a plurality of electrochemical cells 40. A thermal management fluid may be disposed within the housing such that the fluid is in thermal communication with one or more (up to all) of the electrochemical cells. Thermal communication may be achieved via direct contact immersion, or indirect thermal contact. In embodiments in which direct contact immersion is employed, the thermal management fluid may surround and directly contact any portion (up to totally surround and directly contact) one or more (up to all) of the electrochemical cells. In some embodiments, the electrochemical cells may be rechargeable batteries (e.g., rechargeable lithium-ion batteries).

In some embodiments, the thermal management fluid may be disposed within the interior volume of the housing 35 such that substantially the entire volume (e.g., at least 80%, at least 90%, at least 95%, or at least 99%) of the interior volume of the housing 35 that is not occupied by electrochemical cells 35 (or any other solid components within the housing) is occupied by the thermal management fluid.

In some embodiments (not depicted), the electrochemical cell pack may be a component of a fluidic circuit configured to control the temperature of the thermal management fluid. For example, the interior volume of the housing 35 may be in fluid communication with a fluidic circuit that also includes one or more heat exchangers and one or more pumps. The one or more pumps may cause the thermal management fluid to move through the fluidic circuit, passing through the interior volume of the housing 35, where it collects heat generated from operation of the electrochemical cells. The thermal management fluid may then be routed to a heat exchanger, which removes the heat from the thermal management fluid before returning it to the fluidic circuit. It is to be appreciated that this arrangement of the components is one possible configuration for controlling the temperature of the thermal management fluid, and is not meant to be limiting. Alternatively, in some embodiments, the thermal management fluid may remain in the electrochemical cell packs and not be a part of an active temperature control system (i.e., the thermal management fluid may not be in fluid communication with a pump and/or heat exchanger).

In some embodiments, the vent assembly 30 may include flow control mechanisms 45 and a filter assembly 55 disposed downstream of the flow control mechanism 45. Generally, the flow control mechanism may include any device configured to permit or block flow of fluid from the interior volume of the housing 35 to the filter assembly 55 based on conditions present within or near the electrochemical cell pack 20. For example, in some embodiments, the flow control mechanism 45 may include a valve or burst disc configured to actuate (i.e., move from a closed position to an open position such that fluid can flow from the interior volume of the housing 35 to the filter assembly 55) upon a condition (e.g., temperature and/or pressure) within or near the electrochemical cells exceeding a predetermined threshold value. In this manner, upon a thermal runaway event of the electrochemical cell (and associated elevated temperatures and/or pressures), a fluid pathway between the interior volume of the housing 35 to the filter assembly 55 may be achieved. While FIG. 1 depicts only a single flow control mechanism 45, it is to be appreciated that the system 10 may include any number of additional flow control mechanisms 45 that are fluidically coupled to the same or different filter assemblies 55.

In some embodiments, the filter assembly 55 may include an adsorbent filter 65 that is configured to selectively remove/capture one or more toxic components (e.g., hydrogen fluoride and carbonyl fluoride) from a fluid passing through the vent assembly 30. It is to be appreciated that an absorbent filter could be as an alternative to, or in addition to the adsorbent filter 65. In some embodiments, the filter media of the adsorbent filter 65 may include aluminum oxide, silicon oxide, and titanium metal/oxide or combinations of these materials. Alternatively, or additionally, any other suitable adsorbent filter media for filtering toxic byproducts such as hydrogen fluoride and carbonyl fluoride may be employed. In some embodiments, the adsorbent filter 65 may be configured to have a high surface area to volume/weight ratio, and to minimize the pressure drop across its inlet to outlet openings, while maintaining high filtration efficiency.

In some embodiments, the filter assembly 55 may further include either or both of a fire barrier 75 and a particulate filter 85 disposed upstream of the adsorbent filter 65. Generally, the fire barrier 75 may be configured to prevent flames from penetrating through to the remaining components of the filter assembly 55, and the particulate filter 85 may be configured to remove particulate matter (e.g., soot, metals, polymers) from the fluid stream being discharged from the interior space of the housing 35, thereby preventing or mitigating fouling of the filter media of the adsorbent filter 65.

In some embodiments, at a position along the vent assembly 30 that is upstream of the adsorbent filter 65 (and upstream or downstream of either or both of the fire barrier 75 and particulate filter 85), the vent assembly 30 may be constructed of or include a heat dissipating material (e.g., a section of metal tubing). In this manner, heat may be removed from the fluid passing through the vent assembly 30 prior to entering the adsorbent filter 65.

In some embodiments, the vent assembly 30 may additionally include a mechanism for detecting the presence of fluorine containing toxic byproducts such as hydrogen fluoride and carbonyl fluoride in the fluid passing through the vent path 30. In some embodiments, the mechanism may include a material that undergoes a change in physical properties upon exposure to fluorine (hereinafter referred to as a “sensing material”) and a sensor in communication with the sensing material that is configured to measure such physical property. For example, suitable sensing materials include those that undergo a change in electrical resistance upon exposure to fluorine containing toxic byproducts such as hydrogen fluoride and carbonyl fluoride. Examples of such sensing materials include titanium, aluminum, niobium, hafnium, tungsten, or combinations thereof. In such an embodiment, the sensor may be in electrical communication with the sensing material and configured to measure the electrical resistance of the sensing material.

Generally, the sensing material may be disposed within the vent assembly 30 at any of one or more locations that allow for the sensing material to contact the fluid passing the vent path 30. For example, the sensing material may be disposed within any or all of the components of the filter assembly 55 or at positions along the vent path that are upstream of the filter assembly 55.

In some embodiments, the sensing material may be disposed within the vent assembly 30 such that it physically contacts the fluid stream but does not (or at least not substantially) restrict the flow of the fluid stream. For example, the sensing material may be formed as a porous mesh disposed with the flow path or as a coating disposed on one or more surfaces along the flow path of the vent assembly 30.

Referring now to FIG. 2, an example of a sensing material disposed within the vent assembly 30 according to some embodiments of the present disclosure is depicted. As shown, adsorbent filter 65’ may include, for example, filter media 90 extending along a length of the adsorbent filter 65’ and having an inner wall 115 that defines an internal passageway 95 that, upon actuation or release of the flow control mechanism 45, is in fluid communication with the interior volume of the housing 35 (not shown). The adsorbent filter 65’ may further include a sensing material 105 in the form of a porous layer or porous coating that is disposed (continuously or discontinuously) on the inner wall 115.

In such an embodiment, as fluid enters the adsorbent filter 65’, it will travel radially through the porous layer 105 before entering the filter media 90 where toxic byproducts may be captured.

In any of the above-described embodiments, the system may further include a programmable controller that is coupled to one or more of the sensors measuring the physical properties of the sensing material. In this regard, in response to a detection of a change in physical properties, the programmable controller may be configured to notify an operator of the system that toxic byproducts are being released from the electrochemical cell pack 20.

Fluids

In some embodiments, the thermal management fluids may include or consist essentially of fluorinated compounds. In some embodiments, the thermal management fluids may have an electrical conductivity (at 25 degrees Celsius) of less than about le-5 S/cm, less than about le-6 S/cm, less than le-7 S/cm, or less than about le-10 S/cm. In some embodiments, the thermal management fluids may have a dielectric constant that is less than about 25, less than about 15, or less than about 10, as measured in accordance with ASTM D 150 at room temperature. In some embodiments, the thermal management fluids may have any one of, any combination of, or all of the following additional properties: sufficiently low melting point (e.g., < -40 degrees C or -35 degrees C) and high boiling point (e.g., > 80 degrees C for single phase heat transfer), high thermal conductivity (e.g., > 0.05 W/m-K), high specific heat capacity (e.g., > 800 J/kg-K), low viscosity (e.g., < 2 cSt at room temperature), and non-flammability (e.g., no closed cup flashpoint) or low flammability (e.g., flash point > 100 F). In some embodiments, fluorinated compounds having such properties may include or consist of any one or combination of fluoroethers, fluorocarbons, fluoroketones, fluorosulfones, or fluoroolefms. In some embodiments fluorinated compounds having such properties may include or consist of partially fluorinated compounds, perfluorinated compounds, or a combination thereof. In some embodiments, the thermal management fluid may include fluorinated compounds in an amount of at least 20%, at least 50 wt. %, at least 75 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. %, based on the total weight of the thermal management fluid.

In some embodiments, the thermal management fluids of the present disclosure may be relatively chemically unreactive, thermally stable, and non-toxic. The working fluids may have a low environmental impact. In this regard, the working fluids of the present disclosure may have a zero, or near zero, ozone depletion potential (ODP) and a global warming potential (GWP, lOOyr ITH) of less than 500, 300, 200, 100 or less than 10

In some embodiments, the electrochemical cell packs of the present disclosure may be may be configured to store and supply electrical power to any electrical system, such as in a Battery Electric Vehicle (BEV), a Plug-in Hybrid Electric Vehicle (PHEV), a hybrid electric vehicle (HEV), an Uninterruptible Power Supply (UPS) system, a residential electrical system, an industrial electrical system, a stationary energy storage system, or the like.

Various modifications and alterations to this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the illustrative embodiments set forth herein and that such examples and embodiments are presented by way of example only with the scope of the disclosure intended to be limited only by the claims set forth herein as follows. All references cited in this disclosure are herein incorporated by reference in their entirety.

Claims

What is claimed:

1. A system comprising: an electrochemical cell pack comprising: a housing having an interior space; a plurality of electrochemical cells disposed within the interior space; and a thermal management fluid disposed within the interior space such that the electrochemical cell is in thermal communication with the thermal management fluid; and a vent assembly comprising a flow control mechanism and a filter assembly disposed downstream of the flow control mechanism; wherein the flow control mechanism is configured to enable fluid communication between the interior space of the housing and the filter assembly upon a condition within the interior space exceeding a predetermined threshold value; wherein the filter assembly comprises an absorbent or adsorbent filter configured to remove one or more fluorine containing toxic components from a fluid stream passing through the vent assembly.

2. The system of claim 1, the filter assembly further comprising either or both of a fire barrier and a particulate filter disposed upstream of the absorbent or adsorbent filter.

3. The system of any one of the previous claims, the vent assembly further comprising a mechanism for detecting the presence of fluorine containing toxic byproducts.

4. The system of claim 3, the mechanism comprising a sensing material that undergoes a change in one or more physical properties upon exposure to fluorine and a sensor in communication with the sensing material that is configured to measure the physical properties.

5. The system of claim 4, wherein the sensing material undergoes a change in electrical resistance upon exposure to fluorine containing materials.

6. The system of claim 5, wherein the sensing material comprises titanium.

7. The system of any one of the previous claims, the absorbent or adsorbent filter comprising a filter media extending along a length of the filter and having an inner wall that defines an internal passageway in fluid communication with the interior volume of the housing, and wherein the sensing material is disposed as a porous layer on the inner wall.

8. The system of any one of the previous claims, wherein the thermal management fluid comprises a fluorinated material.

9. The system of any one of the previous claims, wherein the thermal management fluid has an electrical conductivity (at 25 degrees Celsius) of less than le-5 S/cm.

10. The system of any one of the previous claims, wherein the thermal management fluid comprises a fluoroether, fluorocarbon, fluoroketone, fluorosulfone, or fluoroolefins.

11. The system of any one of the previous claims, wherein the thermal management fluid comprises fluorinated compounds in an amount of at least 20 wt. %, based on the total weight of the thermal management fluid.

12. An electrical power system comprising: the system of any one of claims 1-11; and an electrical load, wherein the electrochemical cell pack is electrically coupled to the electrical load.

13. The electrical power system of claim 12, wherein the electrical load is a motor for propelling an electric vehicle.