Method for accelerating activation of fuel cell

Abstract

The invention discloses a method for accelerating activation of a fuel cell. The method can reduce activation time and hydrogen usage amount of a fuel cell stack. The method includes performing a step in which supply of air to the fuel cell stack is allowed and interrupted alternately repeated, while performing a current application step in which a high current load equal to or greater than a predetermined current is applied to the fuel cell stack. This is performed simultaneously with pressurizing the hydrogen to a predetermined pressurizing set pressure in a state where the air supply is interrupted and supplying the pressurized hydrogen to the fuel cell stack to cause the hydrogen to be pumped to the cathode of the fuel cell stack.

Description

Technical Field

[0001] The present disclosure relates to a method for activating a fuel cell. More specifically, the present disclosure relates to a method for accelerating the activation of a fuel cell, which can reduce the activation time and hydrogen usage of a fuel cell stack. Background Art

[0002] Generally, polymer electrolyte membrane fuel cells (or proton exchange membrane fuel cells) having high power density are mainly used as fuel cells for vehicles. The polymer electrolyte membrane fuel cell uses hydrogen as a fuel gas and uses oxygen or air containing oxygen as an oxidant gas.

[0003] A fuel cell comprises a single cell that generates electrical energy through a reaction between a fuel gas and an oxidant gas. Typically, a fuel cell is provided in the form of a cell stack, in which a plurality of single cells are stacked in series to meet the desired output level.

[0004] In the case where a fuel cell is installed in a vehicle, in order to meet the required high output level, several tens to several hundreds of single cells are arranged and assembled in the form of a cell stack, each of which generates electric energy individually.

[0005] The single cell constituting the fuel cell stack includes a polymer electrolyte membrane that can move hydrogen cations (protons), and also includes a cathode and an anode, which are electrode layers arranged on both sides of the electrolyte membrane and coated with a catalyst that allows the reaction between hydrogen and oxygen. The assembly in which the cathode and the anode are stacked as catalyst electrode layers on both sides of the polymer electrolyte membrane is usually called a "membrane electrode assembly (MEA)".

[0006] In addition, the single cell of the fuel cell stack further includes a gas diffusion layer (GDL) stacked outside the cathode and the anode and a separator stacked outside the gas diffusion layer to supply fuel and discharge water through a flow path.

[0007] At the same time, during the initial operation of the fuel cell stack after assembly and manufacturing, the activity of the electrochemical reaction is low. Therefore, in order to maximize the normal initial performance, it is necessary to perform a fuel cell activation process in the stacked state.

[0008] Fuel cell activation, also known as "preconditioning" or "break-in," aims to ensure hydrogen ion passage by activating unreactive catalysts and fully hydrating the electrolyte and electrodes (cathode and anode) contained in the electrolyte membrane.

[0009] In order for the fuel cell stack to exhibit normal performance after assembly, the fuel cell stack activation process is performed to ensure a three-phase electrode reaction area, remove impurities from the polymer electrolyte membrane or electrodes, and improve the ion conductivity of the polymer electrolyte membrane.

[0010] A conventional method for accelerating the activation of a fuel cell stack includes supplying pressurized hydrogen during the activation process in a process of applying a high current load to the fuel cell stack (high current discharge process) and in a process in which the fuel cell stack is kept shut down, thereby preventing water from back-diffusion from the cathode (air electrode) and reducing the amount of residual oxygen in the cathode.

[0011] Usually, the process of high current discharge for a predetermined time and the process of pulse discharge for a predetermined time in the off state are repeated dozens of times. However, the problem with the activation process by pulse discharge is that not only the process time is greatly increased, but also the amount of hydrogen used is greatly increased. In the current mass production process of fuel cell stacks, the activation process is the most time-consuming and labor-intensive, and the cost is high.

[0012] In order to achieve efficient mass production of fuel cell vehicles, an activation process is required that can further accelerate the activation of the fuel cell stack to shorten the activation process time and reduce the amount of hydrogen used.

[0013] The above information disclosed in this background technology section is only for enhancing understanding of the background of the present disclosure and therefore it may contain information that does not constitute the relevant technology that is already known in the country to a person of ordinary skill in the art. Summary of the invention

[0014] The present disclosure is devoted to solving the above-mentioned problems associated with the prior art, and an object of the present disclosure is to provide a method for accelerating the activation of a fuel cell, which can reduce the activation time and hydrogen usage of a fuel cell stack.

[0015] The objects of the present disclosure are not limited to the above objects, and those skilled in the art to which the present disclosure belongs (hereinafter referred to as "ordinary technicians") can clearly understand other objects not mentioned herein from the following description.

[0016] In one aspect, the present disclosure provides a method for accelerating the activation of a fuel cell, the method comprising an implementation step of allowing and interrupting the supply of air to the fuel cell stack to be repeated alternately while pressurizing hydrogen to a predetermined pressurization set pressure and supplying the pressurized hydrogen to the fuel cell stack, and simultaneously implementing a current application process of applying a high current load equal to or greater than a predetermined current to the fuel cell stack to promote the pumping of hydrogen to the cathode of the fuel cell stack while the air supply is interrupted.

[0017] In a preferred embodiment, the method may further include a reducing step, wherein the pressure of the hydrogen gas supplied to the fuel cell stack is reduced to a predetermined reduced set pressure lower than the pressurization set pressure while allowing and interrupting the supply of air to the fuel cell stack to be repeated alternately during the current application process.

[0018] In another preferred embodiment, one of the implementing step and the reducing step may be selected and performed according to the single cell voltage state of the fuel cell stack.

[0019] In yet another preferred embodiment, the cell voltage state of the fuel cell stack is a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack.

[0020] In yet another preferred embodiment, the implementing step may be performed when a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack is less than a predetermined first voltage.

[0021] In another preferred embodiment, the first voltage may be 0.1V.

[0022] In yet another preferred embodiment, the reducing step may be performed when a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack is within a range from a predetermined first voltage to a predetermined second voltage.

[0023] In another preferred embodiment, the first voltage may be 0.1V, and the second voltage may be 0.3V.

[0024] In another preferred embodiment, the method may further include an execution step, wherein the execution step is to only execute a current application process of applying a high current load to the fuel cell stack when the hydrogen and air are pressurized to their respective predetermined pressurization set pressures and the pressurized hydrogen and air are supplied to the fuel cell stack. One of the implementation step, the reduction step and the execution step may be selected and performed according to the single cell voltage state of the fuel cell stack.

[0025] In another preferred embodiment, the cell voltage state of the fuel cell stack is a cell voltage deviation representing the difference between an average cell voltage and a minimum cell voltage of the fuel cell stack, and when the cell voltage deviation is greater than a predetermined second voltage, the execution step is performed.

[0026] In yet another preferred embodiment, the second voltage may be 0.3V.

[0027] In another preferred embodiment, the method may further include an execution step, wherein the execution step is to only execute a current application process of applying a high current load to the fuel cell stack when the hydrogen and air are pressurized to their respective predetermined pressurization set pressures and the pressurized hydrogen and air are supplied to the fuel cell stack, and one of the implementation step and the execution step may be selected and performed according to the single cell voltage state of the fuel cell stack.

[0028] In yet another preferred embodiment, the cell voltage state of the fuel cell stack may be a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack.

[0029] In another preferred embodiment, the implementation step can be performed when the cell voltage deviation representing the difference between the average cell voltage and the minimum cell voltage of the fuel cell stack is less than a predetermined first voltage, and the execution step can be performed when the cell voltage deviation is greater than a predetermined second voltage.

[0030] In another preferred embodiment, the first voltage may be 0.1V, and the second voltage may be 0.3V.

[0031] In yet another preferred embodiment, in the performing step, the pressurization set pressure of the hydrogen gas supplied to the fuel cell stack may be set to be higher than the pressurization set pressure of the air supplied to the fuel cell stack.

[0032] In yet another preferred embodiment, in the executing step, the pressurization setting pressure of the hydrogen gas may be set to be 20 kPa higher than the pressurization setting pressure of the air.

[0033] In yet another preferred embodiment, in the executing step, a flow rate of hydrogen supplied to the fuel cell stack and a flow rate of air supplied to the fuel cell stack are set to a ratio of 1.5 to 2.0.

[0034] In yet another preferred embodiment, the predetermined current may be 400A.

[0035] Other aspects and preferred embodiments of the disclosure are discussed herein.

[0036] It should be understood that the term "vehicle" or "vehicular" or other similar terms used herein include conventional motor vehicles, such as passenger cars including SUVs, buses, trucks, various commercial vehicles, watercraft including various boats and ships, aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, for example, a vehicle having both gasoline power and electric power.

[0037] The above and other features of the present disclosure are discussed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other features of the present disclosure will now be described in detail with reference to certain exemplary embodiments shown in the accompanying drawings, which are given hereinafter by way of illustration only and thus do not limit the present disclosure, wherein:

[0039] Figure 1 is a block diagram showing the main components of an apparatus for activating a fuel cell according to the present disclosure;

[0040] Figure 2 is a flow chart showing a fuel cell activation process according to the present disclosure;

[0041] Figure 3 is a diagram showing a high current application process in a fuel cell activation process according to the present disclosure;

[0042] Figure 4 is a diagram illustrating a COD process for generating and applying COD conditions in a fuel cell activation process according to the present disclosure;

[0043] Figure 5 is a diagram showing voltage and air supply states in an activation process according to an embodiment of the present disclosure;

[0044] Figure 6 is a diagram showing voltage and air supply states in an activation process according to a comparative example;

[0045] Figure 7 is a diagram for explaining the reason why the hydrogen pressure is set higher than the air pressure in the activation process according to the present disclosure; and

[0046] Figure 8 Shown are a graph indicating a cell voltage and a graph indicating an air flow rate when a high current applying process and a COD process are simultaneously performed in an activation process according to the present disclosure.

[0047] It should be understood that the accompanying drawings are not necessarily to scale, but only present a certain degree of simplified representation of various preferred features that illustrate the basic principles of the present invention. The specific design features of the present invention disclosed herein, including, for example, specific size, direction, position and shape will depend in part on the specific intended use and use environment.

[0048] In the drawings, reference numbers refer to the same or equivalent parts of the present disclosure throughout the several figures of the drawing. DETAILED DESCRIPTION

[0049] Various exemplary embodiments will now be described more fully with reference to the accompanying drawings, in which only some exemplary embodiments are shown. The specific structural and functional details disclosed herein are merely representative for the purpose of describing exemplary embodiments. However, the present disclosure may be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. Therefore, although the exemplary embodiments of the present disclosure are capable of various modifications and alternative forms, their embodiments are shown in the accompanying drawings by way of example and will be described in detail herein. However, it should be understood that this document is not intended to limit the present disclosure to the specific exemplary embodiments disclosed. On the contrary, the exemplary embodiments are intended to cover all modifications, equivalents, and alternatives that fall within the scope of the present disclosure.

[0050] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiments of the present disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0051] It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intervening elements. Conversely, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0052] The same reference numerals will be used throughout the drawings to the extent possible to represent the same or similar parts. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the exemplary embodiments of the present disclosure. Unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used herein are intended to include plural forms as well. It should also be understood that the terms "comprise", "comprises", "includes" and / or "comprising" when used herein specify the presence of the components, steps, operations and / or elements, but do not exclude the presence or addition of one or more other components, steps, operations and / or elements.

[0053] The present disclosure relates to a method for accelerating activation of a fuel cell, which can reduce the activation time and hydrogen usage of a fuel cell stack.

[0054] The present disclosure provides a method for accelerating the activation of a fuel cell stack, which accelerates the activation of the fuel cell stack by supplying pressurized hydrogen during a high current load application process and a shutdown process to prevent water from back-diffusion from a cathode (air electrode) to an anode (hydrogen electrode), thereby effectively shortening the activation time and reducing the amount of hydrogen used for activation.

[0055] As described above, as a conventional technology for accelerating the activation of a fuel cell stack, there is a method of preventing water from back-diffusion from the air electrode by supplying pressurized hydrogen in a process of applying a high current load to the fuel cell stack during the activation process and in a shutdown process, thereby reducing the amount of oxygen remaining in the cathode.

[0056] However, since the high current load application (high current discharge) process is completed separately from the generation and application of cathode oxygen depletion (COD) conditions, the process time may be long. In addition, in the COD process for generating and applying COD conditions, the shutdown is performed while applying a low current load, so the hydrogen pumping effect may be small.

[0057] On the contrary, according to the present disclosure, COD conditions are intermittently applied when a high current load is applied, thereby maximizing the hydrogen pumping effect, thereby effectively shortening the activation time. In other words, the present disclosure proposes an activation acceleration mode in which the application of a high current load and the application of COD conditions are performed simultaneously to minimize the activation time and maximize the hydrogen pumping effect.

[0058] Figure 1 is a block diagram showing the main components of an apparatus for activating a fuel cell according to the present disclosure, Figure 2 FIG. 1 is a flow chart showing a fuel cell activation process according to the present disclosure. Figure 1 As shown, the configuration of the apparatus for activating a fuel cell stack remains the same as that of a conventional fuel cell system.

[0059] That is, the device for activating the fuel cell stack includes a fuel cell system controller 11, a status diagnosis controller 12 and a current / voltage monitoring system 13, wherein the fuel cell system controller 11 performs overall control of the fuel cell system (including a driving unit for the operation of the fuel cell stack 1) and controls the operating state and operating conditions of the fuel cell stack 1, the status diagnosis controller 12 diagnoses the state of the fuel cell system, and the current / voltage monitoring system 13 monitors the current and voltage of the fuel cell stack 1.

[0060] The fuel cell system controller 11 may be configured to control operating conditions of the fuel cell system, such as temperature, pressure, and humidity of the fuel cell system. Alternatively, however, a separate control system may be provided that controls operating conditions such as temperature, pressure, and humidity by cooperative control with the fuel cell system controller 11. In addition, although not shown in the drawings, an electric control and drive system may be provided.

[0061] Such electrical control and drive systems may include Figure 3 The electronic load 2 shown in the figure and the opening / closing unit (not shown), which will be described later, are configured to allow or interrupt the electrical connection between the electronic load 2 and the fuel cell stack 1. In this case, the operation of the electronic load 2 and the opening / closing unit can be controlled by the fuel cell system controller 11.

[0062] In addition, the equipment for activating the fuel cell stack also includes a hydrogen supply device 20, an air supply device 40 and a cooling device 30, wherein the hydrogen supply device 20 supplies hydrogen as a fuel gas to the fuel cell stack 1 and discharges hydrogen from the fuel cell stack 1, the air supply device 40 supplies air as an oxidant gas to the fuel cell stack 1 and discharges air from the fuel cell stack 1, and the cooling device 30 supplies a coolant to the fuel cell stack 1 and discharges the coolant that has passed through the fuel cell stack 1.

[0063] exist Figure 1 , reference numeral "1" indicates a fuel cell in a stacked state, i.e., a fuel cell stack. Hydrogen may be supplied to the inlet of the anode (hydrogen electrode or fuel electrode) of the fuel cell stack 1, and unreacted hydrogen may be discharged from the outlet of the anode of the fuel cell stack 1 through the hydrogen supply device 20. In addition, air may be supplied to the inlet of the cathode (air electrode) of the fuel cell stack 1, and air and hydrogen may be discharged from the outlet of the cathode of the fuel cell stack 1 through the air supply device 40.

[0064] Similarly, the coolant may be supplied to the inlet of the coolant channel of the fuel cell stack 1 through the cooling device 30, and the coolant may be discharged from the outlet of the coolant channel of the fuel cell stack 1. Figure 1 In the configuration of the apparatus shown, the fuel cell stack 1 may be referred to as a reaction unit, and the hydrogen supply device 20 , the air supply device 40 , the cooling device 30 , and the electrical control and drive system may be collectively referred to as a drive unit.

[0065] The present disclosure includes a gas flow control method for shortening the activation time of a fuel cell stack. The present disclosure provides a method for increasing the activation speed of a fuel cell stack, which is a core component of a fuel cell system, by controlling hydrogen and air supply operating conditions in a simple manner using existing components without using separate components other than those of a general fuel cell system.

[0066] The fuel cell stack 1 can be installed Figure 1 The fuel cell stack activation process according to the present disclosure is performed in the device shown. In addition, the fuel cell stack activation process can be performed under the control of the controller of the system for activation, that is, the above-mentioned fuel cell system controller 11 and the state diagnosis controller 12.

[0067] Although the fuel cell stack activation process according to the present disclosure is described as being performed under the control of multiple controllers (ie, the fuel cell system controller 11 and the status diagnosis controller 12), the fuel cell stack activation process according to the present disclosure may be performed by a single integrated control element rather than multiple controllers.

[0068] Multiple controllers and a single integrated control element may be collectively referred to as a controller. In the following description, these "controllers" are collectively referred to as controllers. The activation acceleration process according to the present disclosure described below may be controlled by a controller. The hydrogen supply device 20, the air supply device 40, the cooling device 30 and the electronic load (in Figure 3 and Figure 4 The drive unit (indicated by reference numeral “2” in the figure) is controlled by a controller.

[0069] Figure 3 is a diagram showing a high current application process in a fuel cell activation process according to the present disclosure, Figure 4 is a diagram illustrating a COD process for generating and applying COD conditions in a fuel cell activation process according to the present disclosure.

[0070] The method of accelerating the activation of a fuel cell stack according to the present disclosure includes a high current application process, in which a high current load is applied to the fuel cell stack 1 in a state where an electronic load 2 is electrically connected to the fuel cell stack 1 while humidified and pressurized hydrogen and pressurized air are supplied to and discharged from the fuel cell stack 1. In the high current application process, a high current equal to or greater than a predetermined current is applied from the fuel cell stack 1 to the electronic load 2.

[0071] In addition, the method for accelerating the activation of a fuel cell stack according to the present disclosure also includes a COD process, in which a high current is applied to the electronic load 2 in a state where the electronic load 2 is electrically connected to the fuel cell stack 1 while supplying humidified and pressurized hydrogen to the fuel cell stack 1 and simultaneously alternately repeating allowing and interrupting the supply of pressurized air to the fuel cell stack 1. The COD process is a process for generating and applying COD conditions for the fuel cell stack.

[0072] In the high current application process, such as Figure 3As shown, in a state where the electronic load 2 is electrically connected to the fuel cell stack 1 , hydrogen is supplied to the anode of the fuel cell stack 1 through the hydrogen supplier 20 , and air is supplied to the cathode of the fuel cell stack 1 through the air supplier 40 .

[0073] A pressurization system capable of supplying pressurized hydrogen and air to the fuel cell stack 1 is applied to Figure 1 The device for activating a fuel cell stack shown in FIG. 1 is a device for activating a fuel cell stack. In a high current application process, hydrogen pressurized to a predetermined pressure and humidified to a high humidification state is supplied to the inlet of the anode of the fuel cell stack 1 by the hydrogen supply device 20, and at the same time, air pressurized to a predetermined pressure is supplied to the inlet of the cathode of the fuel cell stack 1 by the air supply device 40 (pressurization of hydrogen and air).

[0074] Therefore, in the high current application process, a high current generated by and output from the fuel cell stack 1 can be applied to the electronic load 2 (application of high current), and its discharge can be performed through the electronic load 2. In this case, control of other environmental conditions, such as control of the coolant supply to the fuel cell stack 1 and control of the temperature of the fuel cell stack 1, can be performed.

[0075] In addition, the process of generating and applying COD conditions, namely the COD process, includes a process of causing hydrogen to be pumped to the cathode (air electrode) of the fuel cell stack by supplying only pressurized hydrogen to the fuel cell stack.

[0076] In the COD process, Figure 4 As shown, while a high current load is applied in a state where the electronic load 2 is electrically connected to the fuel cell stack 1, hydrogen is supplied to the anode of the fuel cell stack 1 through the hydrogen supply device 20. In this case, while maintaining the supply of pressurized hydrogen to the fuel cell stack, the operation of the air supply device 40 is controlled so that the supply of air to the cathode of the fuel cell stack is alternately repeated by allowing and interrupting it.

[0077] In the COD process, hydrogen pressurized to a predetermined pressure and humidified to a high humidification state is supplied to the inlet of the anode of the fuel cell stack 1 by the hydrogen supply device 20. At the same time, while maintaining the supply of hydrogen, the supply of air to the cathode of the fuel cell stack 1 is alternately repeatedly allowed and interrupted. When the air supply is interrupted, only the pressurized hydrogen is supplied to the fuel cell stack.

[0078] In this case, the following processes are repeated alternately, namely, a process of supplying air pressurized to a predetermined pressure to the cathode inlet of the fuel cell stack 1 through the air supply device 40 and simultaneously supplying pressurized hydrogen (pressurization and supply of hydrogen and air), and a process of interrupting the air supply while maintaining the supply of pressurized hydrogen (hydrogen pressurization and supply, air supply interruption).

[0079] Therefore, in the COD process, the process of promoting hydrogen pumping to the cathode (air electrode) of the fuel cell stack can be performed by supplying hydrogen only to the fuel cell stack 1 .

[0080] Furthermore, according to the present disclosure, the current application step (high current application step) and the COD step (COD condition generation step) are performed simultaneously, thereby further shortening the activation time.

[0081] In other words, the fuel cell stack is operated so that a high current application process of applying a high current in a state where an electronic load 2 having a set current density is connected to the fuel cell stack 1 and a COD process of pumping hydrogen to the reaction surface of the cathode (air electrode) are repeated alternately several times. In order to shorten the process time and improve efficiency, the high current application process and the COD process may be performed simultaneously.

[0082] Hereinafter, the activation acceleration process according to the present disclosure will be described in more detail.

[0083] First, in the high current application process, the operation of the hydrogen supply device 20 and the air supply device 40 is controlled so that the pressurized hydrogen is supplied to the anode of the fuel cell stack 1 through the hydrogen supply device 20, and at the same time, the pressurized air is supplied to the cathode of the fuel cell stack 1 through the air supply device 40. Figure 2 Step S1 in ).

[0084] For example, hydrogen and air can be supplied to the fuel cell stack in a state where they are pressurized to respective predetermined set pressures (e.g., 2.2 bara and 2.0 bara). In this way, since hydrogen and air as reactant gases are pressurized and supplied to the fuel cell stack, the effect of reducing the diffusion resistance of the reactant gases can be obtained.

[0085] In addition, the pressure of hydrogen is increased to prevent back pressure from being generated between the hydrogen outlet pressure (i.e., the pressure at which hydrogen is discharged from the single cell of the fuel cell stack) and the air inlet pressure (i.e., the pressure at which air is supplied to the single cell of the fuel cell stack). In this case, the hydrogen pressure can be set to be at least 0.2 bar (=20 kPa) higher than the air pressure.

[0086] In addition, the supply flow rate of the reactant gas is calculated based on the stoichiometric ratio. For example, hydrogen and air can be supplied at a ratio of 1.5 to 2.0. That is, the flow rate of hydrogen supplied to the anode (hydrogen electrode) of the fuel cell stack and the flow rate of air supplied to the cathode (air electrode) are set to a ratio of 1.5 to 2.0.

[0087] In addition, in a state where the reaction gas is pressurized and supplied to the fuel cell stack, an electronic load is electrically connected to the fuel cell stack to apply a high current, so that a high current equal to or greater than a predetermined current is applied from the fuel cell stack to the electronic load (applying a high current), that is, the high current of the fuel cell stack is discharged to the electronic load. In this case, a high current of 400A or more can be applied.

[0088] In addition, in this case, when the process from the fuel cell stack applying a high current to the electronic load for a predetermined period of time (the fuel cell stack releases a high current to the electronic load) to releasing the applied state is defined as a pulse-type high current application cycle, the cycle can be repeated several times (discharge of high current pulses).

[0089] In this case, a cycle of applying a high current to the electronic load is repeated several times so that the operating voltage (single cell voltage) of the fuel cell stack is maintained at a voltage value of 0.6 V or more or about 0.6 V ( Figure 2 Step S1 in ).

[0090] This is done to increase the rate at which the amount of platinum stabilizes. The rate at which the amount of platinum stabilizes can be increased by repeating the cycle of applying a high current to the electronic load several times.

[0091] In addition, according to the present disclosure, a COD process is performed in a high current application state, in which the air supply is alternately allowed and interrupted while maintaining the pressurized hydrogen supply. In this case, the process of sweeping the stack voltage from a high voltage to about 0 V is repeated by repeating the air supply allowance and interruption (generation and application of COD conditions).

[0092] Due to repeated air supply interruption and interruption in a high current application environment, hydrogen (H 2 )The pumping effect can be maximized, the electrochemical reaction of the oxidized catalyst reduction can be maximized, and the degree of activation can be improved.

[0093] As described above, according to the present disclosure, the high current application process and the COD process are performed simultaneously. When the cell voltage deviation (average cell voltage-minimum cell voltage) during the high current application cycle is less than a predetermined first voltage, for example, 0.1 V, the high current application process and the COD process in which the air supply is alternately allowed and interrupted are performed simultaneously in a state where the pressure of the pressurized hydrogen is maintained at the above-mentioned pressurized set pressure, i.e., 2.2 bar (maximum hydrogen pumping effect) ( Figure 2 Steps S3 to S7 in FIG.

[0094] Furthermore, during the high current application cycle, when the cell voltage deviation exceeds a predetermined second voltage (first voltage < second voltage), for example, 0.3 V, only the high current application process is performed without performing the COD process for generating and applying COD conditions ( Figure 2 Steps S1 and S2 in FIG.

[0095] Cells of the stack whose cell voltage deviation is greater than the second voltage (0.3 V) may be determined as defective cells after the stack is manufactured. If COD conditions are applied when the catalyst is in a poor state, the stack may be damaged and may cause safety hazards due to heat generation.

[0096] In addition, when the cell voltage deviation is within the range of the first voltage to the second voltage (e.g., 0.1V to 0.3V) during the high current application cycle, the high current application process and the COD process in which the permission and interruption of the air supply are alternately repeated are performed simultaneously. However, when the cell voltage deviation is within the range of the first voltage to the second voltage, the hydrogen decompression condition is applied to the COD process. That is, during the COD process, the pressure of the hydrogen supplied to the fuel cell stack can be adjusted to a predetermined reduced set pressure, such as 1.3 bar ( Figure 2 Steps S3 and S4 in FIG.

[0097] A single cell in the battery stack whose cell voltage deviation is within the range of 0.1 V to 0.3 V may also pose a potential hazard. Therefore, in order to adjust the hydrogen pumping degree, the pressurization degree of the hydrogen is reduced by controlling the pressure of the hydrogen to reduce the set pressure.

[0098] As described above, in the activation acceleration process according to the present disclosure, the high current application process and the COD process are performed simultaneously, and as a result, the activation time can be shortened by up to 25% (400 seconds → 300 seconds per cycle) compared to the conventional mode. In addition, since a high current is applied during the COD process, the hydrogen pumping effect can be maximized.

[0099] The reason for applying process conditions differently according to the cell voltage deviation is to prevent damage to the battery stack and occurrence of accidents during the activation process and to improve the efficiency of the activation process.

[0100] Thereafter, when the cell voltage of the fuel cell stack becomes the third voltage when the activation process is repeated, if the current density applied from the fuel cell stack is equal to or greater than the set value, the activation process is terminated. The third voltage of the cell voltage as the termination of the activation process may be set to 0.6 V, and the set value of the current density as the termination of the activation process may be set to 2.0 A / cm 2 ( Figure 2 , and steps S8 and S9 in the above embodiment.

[0101] The current density setting value may be set to a value that is increased by a predetermined level or more compared to the maximum output area of ​​the vehicle in the output area. For example, the current density setting value in the output area may be set to 2.0 A / cm 2 , a value that has increased by 33% to 60% compared to the maximum output area of ​​existing production vehicles and vehicles under development. When this procedure of the activation process is completed, it is possible to ensure the normal performance of the fuel cell stack after vehicle shipment.

[0102] Figure 5 and Figure 6 It is a diagram for comparison between the activation process of the present disclosure and a conventional activation process. Figure 5 An embodiment of the present disclosure is shown, wherein COD conditions are generated and applied during high current activation, while Figure 6 A comparative example is shown.

[0103] In the activation mode of the present disclosure, a high current is applied to the electronic load in a state where the electronic load is electrically connected to the fuel cell stack. In this case, a high current equal to or greater than a predetermined current (e.g., 400A) is applied to the electronic load. While maintaining hydrogen pressurization, when the cell voltage deviation is less than the first voltage according to the cell voltage state of the fuel cell stack, a COD process in which the air supply is alternately allowed and interrupted can be performed simultaneously with the high current application process.

[0104] However, as described above, when the cell voltage deviation falls between the first voltage and the second voltage during high current application, the COD process in which the air supply is allowed and interrupted is repeated alternately is performed in a state where the hydrogen pressure is reduced. In addition, when the cell voltage deviation exceeds the second voltage, only the high current application process is performed.

[0105] On the other hand, in the comparative example according to the conventional technology, a high current applying process of applying a high current load to the fuel cell stack is first performed, while controlling so that the hydrogen and air supplied to the anode and cathode of the fuel cell stack, respectively, are pressurized. Figure 6 In this high current application process, the maximum applied current is set to 400A or more.

[0106] After the high current application process, a process in which the air supply is allowed and interrupted alternately and repeatedly is performed separately. In the process in which the air supply is allowed and interrupted alternately and repeatedly, a current load lower than the current load in the high current application process of the present disclosure is applied to the fuel cell stack. In this state, the air supply to the fuel cell stack is allowed and interrupted repeatedly, and accordingly, a voltage sweep occurs in which the stack voltage is swept from a high voltage to about 0V. This process is repeated. Figure 6In the process in which the enabling and disabling of the air supply are alternately repeated, a current of 30A to 40A is applied.

[0107] Figure 7 FIG. 2 is a diagram for explaining the reason why the hydrogen pressure is set higher than the air pressure in the activation process according to the present disclosure. Figure 7 The anode inlet (hydrogen inlet) and the cathode outlet (air outlet) receiving hydrogen supply can be located on the left side of the single cell of the fuel cell stack, and the cathode inlet (air inlet) and the anode outlet (hydrogen outlet) receiving air supply can be located on the right side of the single cell of the fuel cell stack.

[0108] In the fuel cell activation process according to the present disclosure, during the high current application process, the pressures of hydrogen and air are controlled to respective pressurized set pressures. In this case, the pressure of hydrogen can be controlled to be a predetermined pressure level higher than the pressure of air. For example, during the high current application process, the pressure of hydrogen and the pressure of air can be controlled to be 2.2 bar and 2.0 bar, respectively, and the pressure of hydrogen can be controlled to be about 20 kPa (= 0.2 bar) higher than the pressure of air.

[0109] The reason for this is to prevent Figure 7 Back pressure is created on the right side of the cell shown where the cathode inlet and anode outlet are located. In other words, the pressure of the air is prevented from exceeding the pressure of the hydrogen, thereby minimizing or preventing degradation of the fuel cell stack and the cells during the activation process.

[0110] Due to the pressure loss when the reactant gas passes through the fuel cell stack, Figure 7 In the single cell shown, the pressure of the reaction gas inlet (anode inlet and cathode inlet) is higher than the pressure of the reaction gas outlet (anode outlet and cathode outlet). If the pressure of the hydrogen inlet and the pressure of the air inlet are controlled to be the same as each other, the pressure of the hydrogen outlet becomes lower than the pressure of the air inlet, resulting in Figure 7 The back pressure is generated on the right side of the single cell shown.

[0111] When back pressure occurs, oxygen in the cathode can cross over to the anode, leading to various degradation mechanisms. For example, the electrolyte membrane can degrade due to the production of hydrogen peroxide, and the electrode can degrade due to the formation of an interface between hydrogen and air in the anode.

[0112] Furthermore, when the cell voltage deviation falls between the first voltage (eg, 0.1 V) and the second voltage (eg, 0.3 V), the COD process is performed with the hydrogen pressure reduced to a predetermined reduced set pressure (eg, 1.3 bar).

[0113] This is an evaluation condition for the OCV decay time (ODT) used as an electrolyte membrane status inspection item (membrane degradation test) in the mass production process of the battery stack. It is judged that when the hydrogen pressure is lowered to the set pressure, for example, 1.3 bar, the possibility of additional damage to the single cell is minimized.

[0114] As described above, the method for accelerating fuel cell activation according to the present disclosure is characterized in that the high current application process and the COD process are performed simultaneously. The voltage sweep is generated by alternately repeating the enabling and interrupting of air supply during the high current application process.

[0115] Figure 8 A graph indicating the voltage of a single cell and a graph indicating the air flow rate are shown when a high current application process and a COD process are simultaneously performed in an activation process according to the present disclosure. Figure 8 The air flow rate graph shown makes it possible to confirm the alternating repetition of enabling and disabling of the air supply through the change in the air flow rate SR.

[0116] The method of accelerating activation of a fuel cell according to the present disclosure described in detail above has the following effects and advantages.

[0117] In the current fuel cell mass production process, a fuel cell stack is produced by stacking an electricity generating assembly (EGA) and a separator, wherein the EGA is an assembly of a membrane electrode assembly (MEA) and a gas diffusion layer (GDL).

[0118] The fuel cell stack produced in this way is not installed in the vehicle and works immediately after production. An activation process is necessary to form ion transfer channels and improve the activity of the catalyst through hydration of the electrolyte membrane / binder.

[0119] In the conventional technology, a high current application process in which a high current load is applied to a fuel cell stack and a COD process in which the permission and interruption of air supply are repeated alternately are separately implemented, and a low current is applied during the COD process. Therefore, the activation time is long, the hydrogen pumping effect is poor, and a large amount of time is required to reduce the oxidized catalyst in the cathode.

[0120] In contrast, in the present disclosure, since the COD process in which the air supply is allowed and interrupted alternately and repeatedly is performed simultaneously with the high current application process, the activation time can be shortened (up to 25%). In addition, since the COD process is performed under the condition of applying a high current, the hydrogen pumping effect can be maximized, thereby not only effectively reducing the oxidized catalyst, but also easily removing impurities. In addition, since the pressurized state of hydrogen is maintained during the COD process, hydrogen can be forced to flow to the cathode, thereby accelerating the hydrogen pumping phenomenon.

[0121] In addition, in the present disclosure, the conditions for whether the high current application process and the COD process can be implemented simultaneously are diagnosed, and specific operating conditions corresponding to each diagnostic condition can be established to minimize the occurrence of accidents and damage to the battery stack attributable to defective single cells (establishing standards based on single cell voltage deviations).

[0122] In the current fuel cell stack mass production process, the activation process is the most time-consuming, labor-intensive and costly. However, when the present disclosure is applied to the current fuel cell stack mass production process, the activation time can be greatly shortened (up to 25%), the amount of hydrogen used can be reduced, and the process time can be shortened. As a result, the production cost (labor and material cost) can be reduced and the productivity can be improved.

[0123] As is apparent from the above description, according to the method for accelerating the activation of a fuel cell stack disclosed herein, the activation time can be shortened because the COD process in which the air supply is allowed and interrupted alternately and repeatedly is performed simultaneously with the high current application process. In addition, since the COD process is performed while maintaining hydrogen pressurization during the high current application process, the hydrogen pumping effect can be maximized. Therefore, the amount of hydrogen used can be reduced and the process time can be shortened, thereby reducing production costs (labor and material costs) and improving productivity.

[0124] The present disclosure has been described above with reference to exemplary embodiments. The embodiments described in the specification and shown in the drawings are illustrative only and are not intended to represent all aspects of the present disclosure. Therefore, the present disclosure is not limited to the embodiments set forth herein, and it should be understood by those skilled in the art that various modifications or changes may be made without departing from the technical spirit or scope of the present disclosure disclosed in the appended claims.

Claims

1. A method for accelerating the activation of a fuel cell, the method comprising an implementation step, wherein the implementation step is to implement a process of allowing and interrupting the supply of air to the fuel cell stack alternately and repeatedly while pressurizing hydrogen to a predetermined pressurization set pressure and supplying the pressurized hydrogen to the fuel cell stack, and at the same time implement a current application process of applying a high current load equal to or greater than a predetermined current to the fuel cell stack to promote the step of pumping hydrogen to the cathode of the fuel cell stack while the air supply is interrupted.

2. The method according to claim 1 further includes a reducing step, wherein the pressure of the hydrogen gas supplied to the fuel cell stack is reduced to a predetermined reduced set pressure lower than the pressurized set pressure while allowing and interrupting the supply of air to the fuel cell stack to be repeated alternately during the current application process. 3 . The method according to claim 2 , wherein one of the implementing step and the reducing step is selected and performed according to a single cell voltage state of the fuel cell stack. 4 . The method according to claim 3 , wherein the cell voltage state of the fuel cell stack is a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack. 5 . The method according to claim 3 , wherein the implementing step is performed when a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack is smaller than a predetermined first voltage. The method according to claim 5 , wherein the first voltage is 0.1V.

7. The method according to claim 3, wherein the reducing step is performed when a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack is within a range from a predetermined first voltage to a predetermined second voltage. The method according to claim 7 , wherein the first voltage is 0.1V and the second voltage is 0.3V.

9. The method according to claim 2, further comprising an execution step of only executing a current applying process of applying the high current load to the fuel cell stack in a state where hydrogen and air are pressurized to respective predetermined pressurization set pressures and the pressurized hydrogen and air are supplied to the fuel cell stack, One of the implementing step, the reducing step and the executing step is selected and performed according to the single cell voltage state of the fuel cell stack.

10. The method according to claim 9, wherein the single cell voltage state of the fuel cell stack is a single cell voltage deviation representing a difference between an average single cell voltage of the fuel cell stack and a minimum single cell voltage, and in, When the battery cell voltage deviation is greater than a predetermined second voltage, the execution step is performed. The method according to claim 10 , wherein the second voltage is 0.3V.

12. The method according to claim 1 further includes an execution step, wherein the execution step is to only execute the current application process of applying the high current load to the fuel cell stack in a state where hydrogen and air are pressurized to their respective predetermined pressurization set pressures and the pressurized hydrogen and air are supplied to the fuel cell stack. 13 . The method according to claim 12 , wherein one of the implementing step and the executing step is selected and performed according to a single cell voltage state of a fuel cell stack. 14 . The method according to claim 13 , wherein the cell voltage state of the fuel cell stack is a cell voltage deviation representing a difference between an average cell voltage and a minimum cell voltage of the fuel cell stack.

15. The method according to claim 12, wherein: When the cell voltage deviation representing the difference between the average cell voltage and the minimum cell voltage of the fuel cell stack is less than a predetermined first voltage, the implementation step is performed, and Wherein, when the battery cell voltage deviation is greater than a predetermined second voltage, the execution step is performed.

16. The method according to claim 15, wherein: The first voltage is 0.1V, and the second voltage is 0.3V.

17. The method according to claim 9, wherein: In the execution step, the pressurization set pressure of the hydrogen gas supplied to the fuel cell stack is set to be higher than the pressurization set pressure of the air supplied to the fuel cell stack.

18. The method according to claim 17, wherein: In the execution step, the pressurization setting pressure of the hydrogen gas is set to be 20 kPa higher than the pressurization setting pressure of the air.

19. The method according to claim 9, wherein: In the performing step, a flow rate of hydrogen gas supplied to the fuel cell stack and a flow rate of air supplied to the fuel cell stack are set to a ratio of 1.5 to 2.

0.

20. The method of claim 1, wherein the predetermined current is 400A.

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