Electrochemical state of health estimation method

Abstract

An electrochemical state of health (SoH) estimation method. The method includes receiving an in-operation voltage and / or current signal from the fuel cell stack during operation of the fuel cell stack under one or more operating conditions. The method further includes comparing an in-operation voltage-current relationship based on the operating voltage or current signal under the operating condition (s) to a start of life (BOL) voltage-current relationship under the same or substantially same operating condition (s) to obtain a voltage-current comparison under the operating condition (s). The method also includes estimating a SoH parameter in response to the voltage-current comparison.

Description

Technical Field

[0001] The present disclosure relates to an electro - chemical state - of - health estimation method. The electro - chemical state - of - health estimation method can measure the state of health simultaneously with the operation of a polymer electrolyte fuel cell stack. Background Art

[0002] One type of electrochemical cell is a device that can generate electrical energy from a chemical reaction (e.g., a fuel cell). Fuel cells have shown promise as an alternative power source for vehicles and other transportation applications. Fuel cells operate using renewable energy carriers such as hydrogen. Fuel cells also operate without toxic emissions or greenhouse gases. A single fuel cell includes a membrane - electrode assembly (MEA) and two flow - field plates. A single fuel cell typically delivers 0.5 to 1.0 V. Single fuel cells can be stacked together to form a fuel cell stack with a higher voltage and power. One type of fuel cell is a proton - exchange membrane fuel cell (PEMFC). Summary of the Invention

[0003] According to one embodiment, an electro - chemical state - of - health (SoH) estimation method is disclosed. The method includes receiving in - operation voltage and / or current signals from a fuel cell stack during operation of the fuel cell stack under one or more operating conditions. The method also includes comparing an in - operation voltage - current relationship based on the in - operation voltage and / or current signals under the (one or more) operating conditions with a beginning - of - life (BOL) voltage - current relationship under the (one or more) same or substantially the same operating conditions to obtain a voltage - current comparison under the (one or more) operating conditions. The method also includes estimating an SoH parameter in response to the voltage - current comparison.

[0004] According to one embodiment, an electro - chemical state - of - health (SoH) estimation method is disclosed. The method includes receiving in - operation voltage and / or current signals from a cell stack during operation of the fuel cell stack under one or more operating conditions. The method also includes comparing an in - operation voltage - current relationship based on the in - operation voltage and / or current signals under the (one or more) operating conditions with a beginning - of - life (BOL) voltage - current relationship under the (one or more) same or substantially the same operating conditions to obtain a voltage - current comparison under the (one or more) operating conditions. The method also includes receiving an impedance calculation based on a response to an alternating - current (AC) signal sent to the fuel cell stack. The method also includes estimating an SoH parameter in response to the voltage - current comparison and the impedance calculation.

[0005] According to yet another embodiment, an electro - chemical state - of - health (SoH) estimation method is disclosed. The method includes receiving in - operation voltage and / or current signals from a fuel cell stack during operation of the fuel cell stack under one or more operating conditions. The method also includes comparing an in - operation voltage - current relationship based on the operating voltage or current signal under the (one or more) operating conditions with a beginning - of - life (BOL) voltage - current relationship under the (one or more) same or substantially the same operating conditions to obtain a voltage - current comparison under the (one or more) operating conditions. The method also includes estimating an SoH parameter in response to the voltage - current comparison. The method further includes transmitting the SoH parameter to a diagnostic system of the fuel cell stack. Description of the Drawings

[0006] Figure 1 A schematic side view of certain components of a proton - exchange membrane fuel cell is depicted.

[0007] Figure 2 A flowchart depicting a method for analyzing impedance response to determine the state - of - health (SoH) of a fuel cell system (e.g., a fuel cell stack or an individual fuel cell) is shown.

[0008] Figure 3A 、 Figure 3B and Figure 3C respectively depict a first graph, a second graph, and a third graph of the normalized electro - chemical active surface area (ECSA) as a function of the fuel cell voltage loss (V) at current densities of 0.05 A / cm 2 、1 A / cm 2 and 3 A / cm 2 under specific operating conditions of 80 °C, 100% relative humidity, and 200 kPa pressure, respectively.

[0009] Figure 4 A flowchart depicting a method for integrating the SoH estimation method into a DC / DC converter EIS model is shown.

[0010] Figure 5 A flowchart depicting a method in which SoH monitoring (wherein I - V response is recorded) replaces the DC / DC converter EIS model is shown.

[0011] Figure 6 is a graph showing example I - V characteristics of a fuel cell stack at different current densities at 80 °C and 100% relative humidity under specific operating conditions at the beginning - of - life (BOL), in - operation, and end - of - life (EOL).

[0012] Figure 7A depicts, under specific operating conditions of 80 °C, 100% relative humidity, and 200 kPa pressure, as a function of current density at 1 A / cm2 A graph of oxygen transport resistance (s / cm) as a function of fuel cell voltage loss (V) at a current density of

[0013] Figure 7B Depicts, at specific operating conditions of 80 °C, 100% relative humidity, and 200 kPa pressure, as a function of fuel cell voltage loss (V) at a current density of 1 A / cm 2 A graph of normalized catalyst mass activity as a function of fuel cell voltage loss (V) at a current density of DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take different and alternative forms. The figures are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching one skilled in the art to employ the embodiments in various ways. As will be understood by one of ordinary skill in the art, the various features illustrated and described with reference to any one figure may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. Combinations of illustrated features provide representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be desirable for a particular application or implementation.

[0015] Except where otherwise indicated in the examples or otherwise explicitly stated, all numerical quantities in this specification indicating amounts of materials or conditions of reaction and / or use should be understood to be modified by the word "about" when describing the broadest scope of the invention. Practice within the stated numerical ranges is generally preferred. Additionally, unless explicitly stated to the contrary: percentages, "parts," and ratios are by weight; the term "polymer" includes "oligomer," "copolymer," "terpolymer," etc.; for a given purpose related to the present invention, a group or class of materials described as suitable or preferred means that any mixture of two or more members of the group or class is also suitable or preferred; the molecular weight provided for any polymer is the number average molecular weight; the description of a component in chemical terms refers to the component as added to any combination specified in the description and does not necessarily preclude chemical interactions between the components of the mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation in this document and, as necessary, to normal grammatical variants of the initially defined abbreviation; and, unless explicitly stated to the contrary, measurements of properties are determined by the same techniques as those cited previously or subsequently for the same property.

[0016] The present invention is not limited to the specific embodiments and methods described hereinafter, as specific components and / or conditions can of course vary. In addition, the terms used herein are for the purpose of describing embodiments of the present invention only and are not intended to be limiting in any way.

[0017] As used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. For example, referring to a component in the singular is intended to include a plurality of components.

[0018] The term "substantially" may be used herein to describe the disclosed or claimed embodiments. The term "substantially" may modify a value or relative characteristic disclosed or claimed in this disclosure. In such cases, "substantially" may mean that the value or relative characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of that value or relative characteristic.

[0019] One or more embodiments relate to a method for estimating the state of health (SoH) of a fuel cell. The fuel cell SoH monitoring method can be configured to operate in real time during the operation of the fuel cell such that an estimated SoH value can be generated during the operation of the fuel cell.

[0020] As described above, the fuel cell SOH monitoring method can monitor the SOH of the fuel cell. One type of fuel cell is a proton exchange membrane fuel cell (PEMFC). The PEMFC can include a polymer electrolyte fuel cell stack. Figure 1 A schematic side view of certain components of a PEMFC 10 according to one embodiment is depicted. As Figure 1 shown, the fuel cell 10 includes an anode catalyst support 12 coated with an anode catalyst layer 14 formed of an anode catalyst material and a cathode catalyst support 16 coated with a cathode catalyst layer 18 formed of a cathode catalyst material. A polymer electrolyte material (PEM) 20 extends between the anode catalyst support 12 and the cathode catalyst support 16. The cathode catalyst material can be dispersed at the interface between the PEM 20 and a current collector (not shown) supported by the cathode catalyst support. The current collector can be a porous carbon current collector. The anode catalyst layer 14 is positioned between the anode catalyst support 12 and the PEM 20. The cathode catalyst layer 18 is positioned between the cathode catalyst support 16 and the PEM 20. The anode 22 generally can refer to the anode catalyst support 12 and the anode catalyst layer 14. The cathode 24 generally can refer to the cathode catalyst support 16, the cathode catalyst layer 18 and the current collector. The fuel cell 10 also includes first and second gas diffusion layers (GDLs) (not shown). The first GDL is adjacent to the outer surface 26 of the anode 12, and the second GDL is adjacent to the outer surface 28 of the cathode 16.

[0021] The anode 22 is configured to perform a hydrogen oxidation reaction (represented by Equation 1 below), while the cathode 24 is configured to perform an oxygen reduction reaction (represented by Equation 2 below) during operation of the fuel cell 10.

[0022] H2 → 2H + +2e - (1)

[0023] 4H + +O2+4e - → 2H2O (2)

[0024] Due to the complexity of transferring four (4) electrons, the oxygen reduction reaction is rate-limiting and poses a significant challenge to the optimization of catalyst materials. Deterioration of the cathode catalyst material in the cathode catalyst layer 18 can be an important source of overall performance loss over time in the fuel cell 10.

[0025] During fuel cell operation, the cathode catalyst material can deteriorate primarily in the following ways: (1) coarsening, in which the average particle size increases, and / or (2) dealloying, in which the M element is lost by dissolving in the PEM 20. The coarsening and dealloying rates can be sensitive to the global operating parameters of the fuel cell 10 (e.g., the applied voltage and / or temperature) and / or the local environmental parameters around each catalyst nanoparticle (e.g., the hydration level and / or the structure of the carbon support).

[0026] Catalyst deterioration can lead to overall fuel cell deterioration and a reduction in the total SoH. Fuel cell deterioration can be measured by a combination of indirect metrics (e.g., overall fuel cell polarization) and post-disassembly characterization of the fuel cell (e.g., following an accelerated aging protocol). While post-disassembly characterization (e.g., via electron microscopy and / or spectroscopy) can be very accurate, post-disassembly characterization does not provide a simultaneous measurement of the catalyst health state during fuel cell operation. In addition, post-disassembly characterization may be limited in terms of throughput and the number of fuel cells that can be inspected and characterized. Conversely, electrochemical polarization data may conflate catalyst deterioration with many other polarization sources in the fuel cell. Therefore, electrochemical polarization data may not be used to reliably measure the catalyst SoH simultaneously during fuel cell operation. Given the above, what is needed is a fuel cell SoH monitoring method configured to estimate the SoH simultaneously with the operation of the fuel cell.

[0027] A method for monitoring the SoH of a fuel cell uses electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy can use a direct current to direct current (DC / DC) converter to estimate the SoH in a fuel cell. The DC / DC converter can apply an alternating current (AC) signal to a fuel cell system (e.g., a fuel cell stack or a single fuel cell), thereby generating an impedance response.

[0028] Figure 2 Depicts flowchart 200 including a method for analyzing impedance response to determine the SoH of a fuel cell stack. This method can also be applied to an individual fuel cell within a fuel cell stack. The operations depicted in flowchart 200 can be rearranged, omitted, enhanced, and / or modified depending on the implementation of the method for analyzing impedance response to determine the SoH of a fuel cell stack. Figure 1 The method can cause a perturbation of an electrochemical system in equilibrium or steady state (otherwise known as EIS) as part of the implementation of the SoH estimation method.

[0029] As depicted in operation 202, the method of flowchart 200 includes a DC / DC converter sending an AC signal to the fuel cell stack.

[0030] As depicted in operation 204, the method of flowchart 200 includes collecting a response (e.g., an electrical response) to the AC signal sent to the fuel cell stack. The response can be collected by an electrical sensor.

[0031] As depicted in operation 206, the method of flowchart 200 includes calculating the fuel cell stack impedance based on the response collected in operation 204. The calculation step can be performed by a processing device, a controller, or a computer, which can include any existing programmable electronic control unit or a dedicated electronic control unit.

[0032] As depicted in operation 208, the method of flowchart 200 includes performing a fuel cell stack diagnosis (e.g., fuel cell stack SoH estimation) based on the fuel cell stack impedance calculated in operation 206. The performing step can be performed by a processing device, a controller, or a computer, which can include any existing programmable electronic control unit or a dedicated electronic control unit.

[0033] As depicted in operation 210, the method depicted in flowchart 200 includes estimating the fuel cell stack SoH based on the fuel cell impedance. If the estimated fuel cell stack SoH is normal (e.g., indicating that the operation does not cause greater-than-normal degradation of the fuel cell stack), then control of the method is passed to the diagnostic system control module depicted by operation 212. If the estimated fuel cell stack SoH is abnormal (e.g., indicating that the operation causes greater-than-normal degradation of the fuel cell stack), then control of the method is passed to operation 214.

[0034] As depicted in operation 212, the method of flowchart 200 includes determining whether the fuel cell system is under diagnostic system control. If the fuel cell system is under diagnostic system control, the method proceeds to operation 202 (i.e., the DC / DC converter sends an AC signal to the fuel cell stack). If the fuel cell system is not under diagnostic system control, the method proceeds to operation 216 (i.e., disable the diagnostic system).

[0035] As depicted in operation 214, the method of flowchart 200 attempts operation adjustment in response to an abnormal fuel cell stack SoH condition. After performing the adjustment, control of the method depicted in flowchart 200 is then passed to the diagnostic system control module depicted by operation 212.

[0036] Figure 2 The SoH estimation method described in uses a DC / DC converter. In one or more embodiments, an SoH estimation method is disclosed that uses existing fuel cell system sensors to estimate SoH. The SoH estimation method can be used in real time during operation of the fuel cell system. Existing fuel cell sensors can include those that are standard for a fuel cell or are typically built into a fuel cell. Examples of existing sensors can include one or more current sensors, voltage sensors, temperature sensors, pressure sensors, and / or relative humidity sensors. In one or more embodiments, the monitoring method can operate using only existing sensors (e.g., without any other non-standard or dedicated sensing devices). The use of standard sensors provides implementation convenience and cost effectiveness.

[0037] The SoH estimation method can be combined or coupled to the DC / DC EIS method (e.g., the method that implements the method depicted in Figure 2 ). Alternatively, the SoH estimation method of one or more embodiments can be implemented independently of the DC / DC EIS method. In such an implementation, the SoH estimation method can be a permanent backup option for recording fuel cell operating conditions during the life of the fuel cell or a part thereof.

[0038] In one or more embodiments, the SoH estimation method can implement a method of recording voltage-current signals at (multiple) operating conditions (e.g., temperature, relative humidity, and / or pressure) during real-time fuel cell operation. As a next step in the method of one or more embodiments, the voltage-current relationship can be compared to the beginning-of-life (BOL) voltage-current relationship at the same or substantially the same operating conditions (e.g., the same or substantially the same temperature, relative humidity, and / or pressure). The BOL voltage-current relationship can be pre-measured and / or defined via a performance model of the fuel cell stack at BOL.

[0039] The monitoring algorithm may be implemented within the SoH monitoring system of one or more embodiments. The monitoring algorithm may be implemented into a fuel cell diagnostic system. The algorithm may include an aging model that relates SoH measurements to a current-voltage relationship (IV characteristic) under any operating condition(s) (e.g., combination of operating conditions). The monitoring algorithm integrated into the monitoring system may be used to determine one or more SoH parameters (e.g., decay and / or life loss) under specific operating condition(s) in real time (e.g., concurrently with operation of the fuel cell). The operating condition(s) may be adjusted to reduce SoH decay and / or life loss.

[0040] The aging model implemented within the SoH estimation method of one or more embodiments may use linear regression analysis to relate the IV characteristics to the SoH estimate under different operating condition(s). Figure 3A , Figure 3B and Figure 3C The specific operating conditions of 80°C, 100% relative humidity and 200 kPa pressure are plotted as the pressure at 0.05 A / cm 2 , 1A / cm 2 and 3A / cm 2 Graphs 300, 302 and 304 of normalized electrochemically active surface area (ECSA) as a function of fuel cell voltage loss (V) at current densities of . Figure 3A , Figure 3B and Figure 3C As shown in FIG. 1 , linear regressions 306, 308, and 310 are plotted through clusters of data points 312, 314, and 316, respectively. Linear regressions 306, 308, and 310 relate the monitored IV characteristics to a normalized ECSA related to a SoH parameter. In one or more embodiments, the SoH parameter may be a normalized ECSA. Different regions of the IV curve may show sensitivity to changes in ECSA loss. The sensitivity to changes may provide redundancy for accuracy and / or may trigger a control algorithm.

[0041] Although linear regression can be utilized in the aging models implemented within the SoH estimation methods of one or more embodiments as described above, other models or combinations of models can also be utilized. For example, machine learning-based non-linear modeling, stochastic modeling, and / or uncertainty quantification can be utilized. The one or more models used can be used under different operating conditions to improve the accuracy of the estimation of the SoH monitoring method. An example of a model that can be used in combination with the SoH monitoring method is Gaussian process regression. Gaussian process regression can output one or more nominal SoH parameters and one or more uncertainties associated with the one or more nominal SoH parameters. In one embodiment, the aging model can be combined with an electrochemical model based on the physical aging characteristics of the fuel cell stack and / or advanced machine learning algorithms.

[0042] In one embodiment, the SoH monitoring method can be implemented using the following steps. In a first step, a series of measurements of the fuel cell stack performance degradation (e.g., reduction in normalized ECSA) are made at various stages of degradation. These measurements can be used to establish a correlation or model between the SoH parameter (e.g., normalized ECSA) and the measured I-V response. In one or more embodiments, this correlation can be determined using a physics-based model and / or a machine learning model to determine the relationship between the I-V response and the SoH parameter. The model can actually be integrated into the fuel cell stack management method. The SoH estimation method can be configured to obtain the real-time I-V response during stack operation and estimate the SoH parameter in response to the I-V response. The SoH parameter can indicate the SoH of the fuel cell stack.

[0043] Figure 4 A flowchart of a method 400 for integrating the SoH estimation method into the DC / DC converter EIS model is depicted. Method 400 includes operation 402. Operation 402 utilizes a fuel cell control unit to record the I-V response during fuel cell operation. The I-V response is used in combination with the stack impedance calculation to estimate the SoH estimate of the fuel cell stack.

[0044] Figure 5 A flowchart of a method 500 is depicted in which SoH monitoring (where the I-V response is recorded) replaces the DC / DC converter EIS model. As Figure 5 shown, operation 502 utilizes a fuel cell control unit to record the I-V response during the operation of the fuel cell. In this embodiment, operation 502 replaces operations 202, 204, 206, and 208. In this embodiment, the I-V response is only used to estimate the SoH estimate of the fuel cell stack.

[0045] Figure 6is a graph showing exemplary I-V characteristics of a fuel cell stack at different current densities under specific operating conditions of 80 °C and 100% relative humidity at the beginning of life (BOL), during operation, and at the end of life (EOL). As Figure 6 shown, the fuel cell voltage decays from BOL to EOL at the same current density. As Figure 6 further shown, the fuel cell current decays from BOL to EOL at the same voltage.

[0046] Figure 6 demonstrates typical fuel cell system characteristics under a specific operating condition. For example, any voltage loss at any given current density can be estimated by comparing real-time fuel cell stack current and voltage sensed values with the voltage at the same current density at BOL. The BOL value can be constructed by an integrated fuel cell stack performance model. In one or more embodiments, a number of verification measurements can be mapped before the fuel cell stack is commissioned for operation.

[0047] In one or more embodiments, the fuel cell voltage can be automatically monitored and recorded during normal fuel cell stack operation. During any point in fuel cell operation, the voltage loss can be determined by comparing the fuel cell voltage measurement with the pre-loaded I-V characteristics at BOL under the same or substantially the same operating conditions.

[0048] Figure 7A depicts a graph 700 of oxygen transport resistance (s / cm) as a function of fuel cell voltage loss (V) at a current density of 1 A / cm 2 under specific operating conditions of 80 °C, 100% relative humidity, and 200 kPa pressure. A linear regression 702 is plotted through the cluster of data points 704. The linear regression 702 can correlate the monitored I-V characteristics with the oxygen transport resistance (s / cm) related to the SoH parameter. In one or more embodiments, the SoH parameter can be the oxygen transport resistance (s / cm).

[0049] Figure 7B depicts a graph 706 of normalized catalyst mass activity as a function of fuel cell voltage loss (V) at a current density of 1 A / cm 2 under specific operating conditions of 80 °C, 100% relative humidity, and 200 kPa pressure. A linear regression 708 is plotted through the cluster of data points 710. The linear regression 708 can correlate the monitored I-V characteristics with the normalized catalyst mass activity related to the SoH parameter. In one or more embodiments, the SoH parameter can be the normalized catalyst mass activity.

[0050] The measured I-V response data can be used to identify a degraded stack or portions thereof as replacement candidates. A controller or control unit can vary the voltage, temperature, or other operating parameters of the remainder of the device to compensate (e.g., elevated voltage) or prevent further damage (e.g., reduced voltage).

[0051] In one or more embodiments, measured I-V response data can be aggregated from multiple fuel cell systems (e.g., from multiple fleet vehicles). The aggregated data can be used to create an improved degradation model.

[0052] The processes, methods, or algorithms disclosed herein may be transferable to and / or implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms may be stored in a variety of forms as data and instructions executable by a controller or computer, including but not limited to information permanently stored on a non-writable storage medium such as a ROM device and information rewriteably stored on a writable storage medium such as a floppy disk, magnetic tape, CD, RAM device, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms may be implemented in whole or in part using suitable hardware components such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices, or combinations of hardware, software, and firmware components.

[0053] While the above describes exemplary embodiments, these embodiments are not intended to describe all possible forms encompassed by the claims. The words used in the specification are descriptive words rather than limiting words, and it should be understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously mentioned, the features of the various embodiments may be combined to form additional embodiments of the invention that may not be explicitly described or shown. While the various embodiments may have been described as providing advantages or being superior to other embodiments or prior art implementations in one or more desired characteristics, one of ordinary skill in the art recognizes that one or more features or characteristics may be compromised to achieve desired overall system attributes, depending on the particular application and implementation. These attributes may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Thus, to the extent that any embodiment is described as less desirable with respect to one or more characteristics than other embodiments or prior art implementations, these embodiments are not outside the scope of the disclosure and may be desirable for a particular application.

Claims

1. A method for estimating an electrochemical state of health (SoH), comprising: receiving an in-operation voltage and / or current signal from a fuel cell stack during operation of the fuel cell stack under one or more operating conditions; comparing an in-operation voltage-current relationship based on the in-operation voltage and / or current signal under the one or more operating conditions with a beginning of life (BOL) voltage-current relationship under one or more identical or substantially identical operating conditions to obtain a voltage-current comparison under the one or more operating conditions; as well as A SoH parameter is estimated in response to the voltage-current comparison.

2. The electrochemical SoH estimation method according to claim 1, wherein: The comparing step is performed using an aging model.

3. The electrochemical SoH estimation method according to claim 2, wherein: The aging model includes a linear regression model.

4. The electrochemical SoH estimation method according to claim 2, wherein: The aging model includes a nonlinear model, a random model and / or an uncertainty quantification model.

5. The electrochemical SoH estimation method according to claim 2, wherein: The aging model includes Gaussian process regression, and the SoH parameters include one or more nominal SoH parameters and one or more uncertainties associated with the one or more nominal SoH parameters. 6 . The electrochemical SoH estimation method of claim 1 , further comprising adjusting one or more operating conditions of the fuel cell stack in response to the SoH parameter.

7. The electrochemical SoH estimation method according to claim 1, wherein: The aging model includes a series of measurements of electrochemical performance degradation and the associated voltage-current relationship related to the model SoH parameters.

8. The electrochemical SoH estimation method according to claim 1, wherein: The estimating step includes considering the series of measurements of electrochemical performance decay, the associated voltage-current relationship and the model SoH parameter to estimate the SoH parameter.

9. The electrochemical SoH estimation method according to claim 1, wherein: The one or more operating conditions are measured using one or more fuel cell stack sensors.

10. The electrochemical SoH estimation method according to claim 9, wherein: The one or more fuel cell stack sensors include a temperature sensor, a relative humidity sensor, and / or a pressure sensor.

11. The electrochemical SoH estimation method according to claim 1, wherein: The SoH parameter is the attenuation of the fuel cell stack.

12. The electrochemical SoH estimation method according to claim 1, wherein: The SoH parameter is the life loss of the fuel cell stack.

13. The electrochemical SoH estimation method according to claim 1, wherein: The SoH parameter is the voltage loss of the fuel cell stack.

14. The electrochemical SoH estimation method according to claim 1, wherein: The operating conditions are measured solely using one or more fuel cell stack sensors.

15. The electrochemical SoH estimation method according to claim 1, wherein: The fuel cell stack is a polymer electrolyte fuel cell stack.

16. The electrochemical SoH estimation method according to claim 1, wherein: The fuel cell stack is a single fuel cell in the fuel cell stack.

17. The electrochemical SoH estimation method according to claim 1, wherein: The SoH parameter is the resistance to oxygen transfer.

18. The electrochemical SoH estimation method according to claim 1, wherein: The SoH parameter is the normalized catalyst mass activity.

19. A method for estimating an electrochemical state of health (SoH), comprising: receiving an in-operation voltage and / or current signal from a fuel cell stack during operation of the fuel cell stack under one or more operating conditions; comparing an in-operation voltage-current relationship based on the in-operation voltage and / or current signal under the one or more operating conditions with a beginning of life (BOL) voltage-current relationship under one or more identical or substantially identical operating conditions to obtain a voltage-current comparison under the one or more operating conditions; receiving an impedance calculation based on a response to an alternating current (AC) signal sent to the fuel cell stack; as well as A SoH parameter is estimated in response to the voltage-current comparison and the impedance calculation.

20. A method for estimating an electrochemical state of health (SoH), comprising: receiving an in-operation voltage and / or current signal from a fuel cell stack during operation of the fuel cell stack under one or more operating conditions; comparing an in-operation voltage-current relationship based on the in-operation voltage and / or current signal under the one or more operating conditions with a beginning of life (BOL) voltage-current relationship under one or more identical or substantially identical operating conditions to obtain a voltage-current comparison under the one or more operating conditions; estimating a SoH parameter in response to the voltage-current comparison; and transmitting the SoH parameter to a diagnostic system of the fuel cell stack.

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