System and method for quantitative measurement of gas generated by battery cell or battery cell component as function of time during testing

Abstract

Systems and methods for quantitatively measuring gases generated by a battery cell or battery cell component as a function of time during a test. A method for measuring a gas generated by at least a portion of a battery cell includes disposing a test sample in a chamber. The test sample includes one of a battery cell including a terminal and a gas port and a test fixture including a terminal and a gas port and housing at least a portion of the battery cell. The method includes connecting a gas port of a test sample to a node; supplying a carrier gas to the node at a known pressure and flow rate; sampling the gas at or downstream of the node using at least one of a mass spectrometer and a gas analyzer; and determining a concentration of the gas in the test sample using at least one of a mass spectrometer and a gas analyzer.

Description

[0001] Introduction

[0002] The information provided in this section is for the purpose of presenting the context of the present disclosure generally. The work of the presently named inventors, to the extent it is described in this section and to the aspects that may not otherwise be counted as prior art descriptions at the time of filing, is neither expressly nor implicitly admitted to be prior art to the present disclosure.

[0003] The present disclosure relates to battery cells, and more particularly to systems and methods for qualitatively measuring gases in battery cells during operation and / or heating of the battery cells.

[0004] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, include one or more electric machines and a battery system that includes one or more battery cells, modules, and / or battery packs. A power control system is used to control charging and / or discharging of the battery system during charging and / or driving.

[0005] A battery cell includes an enclosure housing surrounding a battery cell stack that includes one or more cathode electrodes, anode electrodes, and separators and electrolytes. The cathode electrode includes a cathode active material layer disposed on a cathode current collector. The anode electrode includes an anode active material layer disposed on an anode current collector.

[0006] When a battery cell is exposed to certain conditions such as formation cycling, overcharging, or elevated temperatures, gas-generating reactions occur within the battery cell. Since the battery cell stack is located inside a sealed enclosure, it is difficult to determine the type of gas generated, the concentration of the gas, and / or the timing of the gas generated. Summary of the Invention

[0007] A method for measuring gases generated by at least a portion of a battery cell includes disposing a test sample in a chamber. The test sample includes one of a battery cell that includes terminals and a gas port and a test fixture that includes terminals and a gas port and houses at least a portion of the battery cell. The method includes connecting the gas port of the test sample to a node; supplying a carrier gas to the node at a known pressure and flow rate; sampling the gas at or downstream of the node using at least one of a mass spectrometer and a gas analyzer; and determining the concentration of the gas in the test sample using at least one of a mass spectrometer and a gas analyzer.

[0008] Among other features, the check valve includes a first port connected to the battery cell and a second port connected to the node. During testing, the carrier gas is supplied at a first flow rate that is greater than or equal to ten times the second flow rate of the gas generated by the test sample.

[0009] The carrier gas includes a mixture of a reference gas having a predetermined concentration and an inert gas.

[0010] Among other features, at least one of the mass spectrometer and the gas analyzer includes a mass spectrometer. The mass spectrometer is calibrated using the reference gas as an internal standard. During testing, the test sample is heated to a predetermined temperature. During testing, the test sample is heated based on a temperature profile as a function of time.

[0011] Among other features, the method includes charging the test sample to a predetermined voltage before testing. The method includes supplying current to and / or drawing current from the test sample during testing. The method includes sampling the voltage of the battery cell as a function of time during testing.

[0012] Among other features, the method includes connecting the mass spectrometer to the node using a capillary. The method includes purging the chamber with a purge gas during testing. The method includes monitoring at least one of the chamber temperature, the battery cell temperature, the battery cell pressure, and the chamber pressure as a function of time during testing.

[0013] A system for measuring gases in a battery cell includes a chamber that includes a cavity configured to receive a test sample, where the test sample includes one of a battery cell that includes terminals and a gas port and a test fixture that includes terminals and a gas port and houses at least a portion of the battery cell. The check valve includes a first port connected to the gas port of the battery cell and a second port connected to the node. A first gas source supplies a carrier gas to the node, the carrier gas including a reference gas having a predetermined concentration and an inert gas. At least one of a mass spectrometer and a gas analyzer is configured to sample the gas at the node and determine the concentration of one or more gases in the battery cell as a function of time using the mass spectrometer.

[0014] Among other features, the carrier gas is supplied at a first flow rate that is greater than or equal to ten times the second flow rate of the gas generated by the test sample during testing. At least one of the mass spectrometer and the gas analyzer includes a mass spectrometer. The mass spectrometer is calibrated using the reference gas as an internal standard.

[0015] Among other features, the heater performs one of the following: heating the test sample to a predetermined temperature during testing and heating the test sample based on a temperature profile as a function of time during testing.

[0016] Among other features, the voltage / current sensor / source is configured to perform at least one of the following: charge the test sample to a predetermined voltage before testing, supply current to and draw current from the test sample during testing, and monitor at least one of the current and voltage of the test sample as a function of time during testing.

[0017] Among other features, the system includes at least one of the following: a chamber pressure sensor that monitors the pressure in the chamber as a function of time during testing, and a test sample pressure sensor configured to monitor the pressure in one of the enclosures of the battery cell and in the test fixture.

[0018] A method for measuring gas generated by at least a portion of a battery cell includes: disposing a test sample in a chamber, where the test sample includes one of the following:

[0019] a battery cell including terminals and a gas port; and a test fixture including terminals and a gas port and accommodating at least a portion of the battery cell; connecting the gas port of the test sample to a node; supplying a carrier gas to the node at a known pressure and flow rate; sampling the gas at or downstream of the node using at least one of a mass spectrometer and a gas analyzer; and determining the concentration of the gas in the test sample using at least one of a mass spectrometer and a gas analyzer.

[0020] Further includes a check valve that includes a first port connected to the battery cell and a second port connected to the node.

[0021] Wherein, during testing, the carrier gas is supplied at a first flow rate that is greater than or equal to ten times a second flow rate of the gas generated by the test sample.

[0022] Wherein the carrier gas includes a mixture of a reference gas having a predetermined concentration and an inert gas.

[0023] Wherein: at least one of the mass spectrometer and the gas analyzer includes a mass spectrometer, and the mass spectrometer is calibrated using the reference gas as an internal standard.

[0024] Wherein, during testing, the test sample is heated to a predetermined temperature.

[0025] Wherein, during testing, the test sample is heated based on a temperature profile as a function of time.

[0026] Further includes charging the test sample to a predetermined voltage before testing.

[0027] Further includes at least one of supplying current to and drawing current from the test sample during testing.

[0028] Further comprising sampling the voltage of the battery cell as a function of time during testing.

[0029] Further comprising connecting a mass spectrometer to the node using a capillary.

[0030] Further comprising purging the chamber with a purge gas during testing.

[0031] Further comprising monitoring at least one of the chamber temperature, the battery cell temperature, the battery cell pressure, and the chamber pressure as a function of time during testing.

[0032] A system for measuring gases in a battery cell, comprising: a chamber including a cavity configured to receive a test sample, wherein the test sample includes one of the following: a battery cell including terminals and a gas port; and a test fixture including terminals and a gas port and housing at least a portion of the battery cell; a check valve including a first port connected to the gas port of the battery cell and a second port connected to the node; a first gas source supplying a carrier gas to the node, the carrier gas including a reference gas having a predetermined concentration and an inert gas; and at least one of a mass spectrometer and a gas analyzer configured to sample the gas at the node and determine the concentration of one or more gases in the battery cell as a function of time using the mass spectrometer.

[0033] Wherein, during testing, the carrier gas is supplied at a first flow rate that is greater than or equal to ten times a second flow rate of the gas generated by the test sample.

[0034] Wherein: at least one of the mass spectrometer and the gas analyzer includes a mass spectrometer, and the mass spectrometer is calibrated using the reference gas as an internal standard.

[0035] Further comprising a heater to perform one of the following: heating the test sample to a predetermined temperature during testing, and heating the test sample based on a temperature profile as a function of time during testing.

[0036] Further comprising a voltage / current sensor / source configured to perform at least one of the following: charging the test sample to a predetermined voltage before testing; supplying current to and drawing current from the test sample during testing; and monitoring at least one of the current and voltage of the test sample as a function of time during testing.

[0037] Further comprising at least one of the following: a chamber pressure sensor monitoring the pressure in the chamber as a function of time during testing; and a test sample pressure sensor configured to monitor the pressure in one of the enclosures of the battery cell and in the test fixture.

[0038] Additional applicable fields of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. Description of the Drawings

[0039] The present disclosure will be more fully understood in light of the detailed description and the drawings, in which:

[0040] Figure 1A is a side cross-sectional view of an example of a battery cell including a battery cell stack that includes an A anode electrode, a C cathode electrode, and an S separator disposed within a battery enclosure;

[0041] Figure 1B is a side cross-sectional view of a test fixture that houses at least a portion of a battery cell according to the present disclosure;

[0042] Figure 2A and Figure 2B is a functional block diagram and a schematic diagram of an example of a gas test system for a battery cell according to the present disclosure;

[0043] Figure 3 is for operating according to the present disclosure Figure 2A and Figure 2B is a flowchart of an example of a method for a gas test system;

[0044] Figure 4 is a graph illustrating an example of a setpoint temperature and a battery cell temperature as a function of time according to the present disclosure; and

[0045] Figure 5 is a graph illustrating an example of a gas concentration percentage, a voltage, and a battery temperature as a function of time according to the present disclosure.

[0046] In the drawings, reference numbers may be reused to identify similar and / or identical elements. Detailed Description

[0047] Although the testing of the battery cell according to the present disclosure is described in the context of a battery cell for a vehicle, the battery cell may be used in other applications such as stationary applications.

[0048] The present disclosure relates to a gas test system and method configured to quantitatively measure gases generated within a test sample that includes a battery cell or a test fixture that includes at least a portion of a battery cell. The test sample may be tested in real time while controlling operating parameters to predetermined operating conditions (e.g., corresponding to heating, formation, and / or cycling).

[0049] For example, the test sample can be heated to a predetermined temperature based on a time-varying temperature profile or not heated during the test. The gas generated by the test sample is entrained in a carrier gas. In some examples, the carrier gas includes a reference gas and an inert gas having a known or predetermined concentration. The gas from the test sample and the reference gas are sampled by a mass spectrometer and / or a gas analyzer. For example, during a test using the reference gas concentration as a reference, the mass spectrometer quantitatively measures one or more gases as a function of time.

[0050] In some examples, the battery cell includes a stack of battery cell units enclosed in a flexible battery enclosure, such as a pouch cell. In other examples, the battery cell includes a stack of battery cell units enclosed in a prismatic, cylindrical, coin-shaped, or other type of battery enclosure made of a hard metal with a heat-resistant seal. In other examples, one or more assemblies of the cathode electrode, anode electrode, and / or separator are arranged in a test fixture that includes a gas port, terminals, and a device for applying pressure to the one or more assemblies of the cathode electrode, anode electrode, and / or separator. In still other examples, individuals or combinations of components of the battery cell, such as the anode electrode, cathode electrode, separator, and / or electrolyte, can be placed in the test fixture / enclosure. The components can be preconditioned, for example, by cycling or charging, and then disassembled and reassembled in the test fixture.

[0051] In some embodiments, the mass spectrometer samples the carrier gas and the battery cell gas at a downstream location of the test sample using a mass spectrometer sampling line, such as a capillary. The gas mixture including the carrier gas is supplied at a constant flow rate and pressure such that when the test sample generates gas, the pressure and flow remain almost constant. The precise metering of the reference gas (in the carrier gas) allows the mass spectrometer to quantify other gases sampled from the test sample, such as hydrogen, carbon dioxide, ethylene, ethane, methane, or other gases.

[0052] The battery test system allows for real-time quantitative measurement of calibration gases, direct comparison from one test to another, and prevention of electrolyte contamination of the mass spectrometer. For example, during operations such as heating, formation, cycling, and / or other operating conditions that generate gas within the battery cell, the gas from the battery cell can be measured in-situ. While any form of battery cell with a gas port can be used, a battery cell (or test fixture) with a hard enclosure allows for exhaust gas analysis at higher battery cell temperatures and pressures.

[0053] Now refer to Figure 1A, the battery cell 10 includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 arranged in a battery cell stack 12 in a predetermined sequence, where C, S, and A are integers greater than zero. The battery cell stack 12 is arranged in an enclosure 50. The C cathode electrodes 20-1, 20-2,... and 20-C include cathode active material layers 24 arranged on one or both sides of a cathode current collector 26.

[0054] The A anode electrodes 40-1, 40-2,... and 40-A include anode active material layers 42 arranged on one or both sides of an anode current collector 46. In some examples, the A anode electrodes 40 and the C cathode electrodes 20 exchange lithium ions during charging / discharging, although other chemistries may be used. In some examples, one or both of the cathode active material layer 24 and / or the anode active material layer 42 include a dry coating that includes one or more active materials, one or more optional conductive additives, and / or one or more optional binder materials that are applied (e.g., cast, laminated, deposited, etc.) to the current collector.

[0055] In some examples, the cathode current collector 26 and / or the anode current collector 46 include a metal foil, a metal mesh, a perforated metal, a three-dimensional (3D) metal foam, and / or an expanded metal. In some examples, the current collector is made of one or more materials selected from the group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and / or their alloys.

[0056] External tabs 28 and 48 are respectively connected to the current collectors of the C cathode electrodes 20 and the A anode electrodes 40, and may be arranged on the same or different sides of the battery cell stack 12. The external tabs 28 and 48 are connected to the terminals 60 and 62 of the battery cell. In some examples, the enclosure 50 includes a gas port 64.

[0057] In Figure 1B , the test fixture 80 includes a cover 82 and a bottom 84, optional terminals 88 and 90 for providing connection to a portion 91 of the battery cell, and a gas port 92 for gas sampling during testing. In some examples, the portion 91 of the battery cell is arranged in the bottom 84, and the cover 82 optionally applies pressure to the portion 91 of the battery cell (or uses another pressure generating device).

[0058] Now refer to Figure 2A and Figure 2B , the gas test system 100 for a battery cell includes a chamber 110 that includes a cavity 113 enclosed by a lid 111. In Figure 2AIn this case, the heater 114 can be used to control the temperature of the chamber 110 and the test sample 120. The chamber temperature sensor 134 senses the temperature of the chamber 110. The test sample temperature sensor 138 senses the temperature of the test sample 120 (e.g., a battery cell or a test fixture including at least a portion of the battery cell). As can be appreciated, the heater 114 can be controlled in response to feedback from the chamber temperature sensor 134 and / or the test sample temperature sensor 138.

[0059] The test sample 120 is disposed inside the cavity of the chamber 110. The test sample 120 includes a gas port 124 and optionally includes positive and negative terminals 122. In some examples, the gas port 124 can be connected to a connector 128, such as a quick disconnect, via a gas line.

[0060] The voltage and current sensor / source 132 (e.g., a potentiostat) is connected to the positive and negative terminals 122. The voltage and current sensor / source 132 senses the voltage across the positive and negative terminals 122 of the test sample 120 (if used). The voltage and current sensor / source 132 can also apply and / or vary the voltage and current across the positive and negative terminals 122 of the test sample 120 as a function of time (or an event or an operating parameter) during the test.

[0061] In some examples, a purge gas source 150 supplies a purge gas (e.g., an inert gas such as argon (Ar)) to purge the chamber 110 via a pressure regulator 151, a flow controller 152, and a gate valve 154. A gate valve 190 is connected to the chamber 110 to provide a chamber exhaust port for discharging the purge gas. The chamber pressure sensor 158 senses the pressure inside the chamber 110.

[0062] In some examples, a check valve 178 is disposed between the test sample 120 and the node 179. In some examples, the check valve 178 opens when the pressure difference between the battery cell side and the sampling side of the check valve 178 is greater than a predetermined pressure difference. In some examples, the predetermined pressure difference is less than or equal to 1 psi (e.g., 1 / 3 psi).

[0063] The gas source 170 supplies a carrier gas. In some examples, the carrier gas includes a predetermined mixture of an inert gas and a reference gas, and the carrier gas is connected to the node 179 through a pressure regulator 172 and a flow controller 174. The node 179 is also connected to a sampling line 186 (e.g., a capillary), and the sampling line 186 (e.g., a capillary) is connected to an exhaust port, a mass spectrometer 188, and an optional gas analyzer 184. In some examples, the gas analyzer 184 includes a Fourier transform infrared spectroscopy (FTIR) gas analyzer, a gas chromatography (GC) gas analyzer, a gas sensor such as a hydrogen sensor, and / or a volatile organic compound (VOC) sensor. As can be appreciated, gas sampling can be performed by the mass spectrometer 188 and / or one or more gas analyzers 184.

[0064] The mass spectrometer 188 samples the carrier gas from the gas source 170 (e.g., including an inert gas and a reference gas at a known concentration) and the gas generated by a test sample (e.g., a battery cell or a part of a battery cell). The mass spectrometer measures the concentration of the gas in the known reference gas and the gas from the battery cell. Examples of the sampled gas include molecular hydrogen (H 2 ), carbon dioxide (CO 2 ), methane (CH 4 ), ethane (C 2 H 6 ), ethylene (C 2 H 4 ), molecular oxygen (O 2 ), carbon monoxide (CO), helium (He), argon (Ar), etc. In some examples, the reference gas includes any gas that is not one of the battery cell gases to be sampled by the mass spectrometer 188. For example, the reference gas can include helium (He). For example, the inert gas can include argon (Ar).

[0065] In Figure 2B, the flow of gas during testing is shown. The gas source 170 supplies a known gas mixture at a controlled pressure and flow rate. The reference gas is delivered in the known gas mixture at a predetermined concentration. In some examples, the known gas mixture has a flow rate greater than the flow rate of the gas generated by the battery cell. In some examples, the flow rate of the known gas mixture is at least 10 times greater than the flow rate of the gas generated by the battery cell. For consistency, the carrier gas flow rate is maintained constant from one battery cell test to another battery cell test to allow comparison.

[0066] The gas from the battery cell is entrained by the known gas mixture. The flow rate of the known gas mixture is significantly greater than the flow rate of the gas from the battery cell. The mass spectrometer 188 uses a vacuum to sample a small amount of the known gas mixture and the gas from the battery cell. The purge gas source 150 can be used to evacuate the gas from the interior of the chamber 110.

[0067] The volume flow rate of the gas used (cc / min) = concentration (%) * carrier gas flow rate (cc / min) is used to calculate the volume flow rate of each calibration gas. The volume flow rate can be integrated to calculate the total volume of each gas generated over a time interval.

[0068] Now referring to Figure 3 , a method for testing a battery cell is shown. At 208, the battery cell is optionally pre-treated and / or the voltage of the battery cell is set to a predetermined voltage. At 210, the chamber is optionally purged. At 212, a gas mixture including a reference gas with a known concentration and an inert gas is supplied.

[0069] At 214, the method determines whether the test has started. If 214 is true, the method optionally monitors the voltage of the battery cell. At 222, gas from the battery cell is optionally sampled using a mass spectrometer and / or a gas analyzer. At 230, the battery is optionally heated to a predetermined temperature, heated based on a temperature profile, and / or charged or discharged using a predetermined charge / discharge profile. At 234, the concentration of the gas from the battery cell is determined as a function of time using a mass spectrometer and / or a gas analyzer. At 238, the method determines whether the test has ended. If false, the method returns to 218.

[0070] Now referring to Figure 4 and Figure 5 , an example of heating and gas concentration data collected during the test of a battery cell is shown. In Figure 4 , the temperature profile of the battery cell under test is shown. During the test, the heater increases the temperature based on the set point temperature Ts. The temperature T of the battery cell increases in response.

[0071] In Figure 5 , the battery cell is initially charged to a predetermined voltage V. As the temperature T of the battery cell increases, the separator melts and causes a short circuit, which causes the voltage to drop to near zero. The timing and concentration of various gases (e.g., CO 2 , CH 4 , C 2 H 4 and H 2 ) are detected in real time. For example, as the temperature increases, the concentration of CO 2 increases significantly. The concentration of H 2 also increases.

[0072] The gas test system for a battery cell according to the present disclosure quantitatively measures the gas generated by the battery cell. The gas test system uses a battery cell having a gas port that allows gas to pass from the battery cell when the pressure within the battery cell builds up. The battery cell may include a pouch cell or a hard case cell.

[0073] Voltage and current sensors / sources (such as a voltage regulator) monitor the cell voltage and / or charge / discharge the battery cell. An optional check valve prevents the carrier gas from flowing back into the battery cell and avoids electrolyte drying out. An optional pressure sensor measures the pressure of the gas released from the gas port of the battery cell.

[0074] When heating is involved, a heater heats the chamber and the battery cell. In some examples, in the case of thermal runaway, the chamber is flushed with an inert gas (e.g., Ar) to entrain gases / particles. Testing of a hard case battery cell having a gas port is enabled up to a predetermined temperature (e.g., ~300 °C). A temperature sensor such as a thermocouple measures the cell temperature.

[0075] The foregoing description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses. The broad teachings of the present disclosure may be implemented in a variety of forms. Thus, while the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited since other modifications will become apparent upon study of the drawings, the specification, and the appended claims. It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure. Additionally, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure may be implemented in and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more of the embodiments with each other are still within the scope of the present disclosure.

[0076] The spatial and functional relationships between components (e.g., between modules, circuit components, semiconductor layers, etc.) are described using various terms including: "connected", "joined", "coupled", "adjacent", "close", "on top", "above", "below", and "disposed". Unless explicitly described as "direct", when describing the relationship between a first and a second component in the foregoing disclosure, the relationship can be a direct relationship in which no other intervening components exist between the first and second components, but can also be an indirect relationship in which one or more intervening components (spatially or functionally) exist between the first and second components. As used herein, the phrase "at least one of A, B, and C" should be interpreted to mean logic (A or B or C), using non-exclusive logical OR, and should not be interpreted to mean "at least one of A, at least one of B, and at least one of C".

[0077] In the figures, the arrow direction indicated by the arrows generally indicates the information flow (such as data or instructions) of interest to the illustration. For example, when element A and element B exchange multiple types of information, but the information transmitted from element A to element B is relevant to the illustration, the arrow can point from element A to element B. This one-way arrow does not mean that no other information is transmitted from element B to element A. In addition, for the information sent from element A to element B, element B can send a request for that information or receive an acknowledgement from element A.

Claims

1. A method for measuring gas generated by at least a portion of a battery cell, comprising: Place the test sample in the chamber. The test sample includes one of the following: a battery cell, including terminals and a gas port; and a test fixture including terminals and gas ports and receiving at least a portion of a battery cell; Connect the gas port of the test specimen to the node; Supplying carrier gas to the node at a known pressure and flow rate; sampling the gas at or downstream of the node using at least one of a mass spectrometer and a gas analyzer; and The concentration of the gas in the test sample is determined using at least one of a mass spectrometer and a gas analyzer. 2 . The method of claim 1 , further comprising a check valve including a first port connected to the battery cell and a second port connected to the node.

3. The method according to claim 1, wherein: The carrier gas is supplied during the test at a first flow rate greater than or equal to ten times a second flow rate of the gas generated by the test sample.

4. The method according to claim 1, wherein: The carrier gas includes a mixture of a reference gas and an inert gas having a predetermined concentration.

5. The method according to claim 4, wherein: At least one of the mass spectrometer and the gas analyzer comprises a mass spectrometer, and The mass spectrometer was calibrated using the reference gas as an internal standard.

6. The method according to claim 1, wherein: During the test, the test specimen is heated to a predetermined temperature.

7. The method according to claim 1, wherein: During testing, the test specimen is heated based on a temperature profile as a function of time.

8. The method of claim 1, further comprising charging the test sample to a predetermined voltage before testing. 9 . The method of claim 1 , further comprising at least one of supplying current to and drawing current from the test sample during testing.

10. The method of claim 1, further comprising sampling the voltage of the battery cell as a function of time during the test.

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