KR20210062192A - A highly durable fuel cell system capable of releasing cell voltage reversal - Google Patents

Abstract

The present invention relates to a fuel cell system including a configuration with which it is possible to check whether a reverse voltage has occurred and then resolve it. The fuel cell system includes: a fuel cell stack including at least one membrane-electrode assembly; and a battery cell provided on at least one side of the fuel cell stack. The battery cell includes: a working electrode including a cathode for oxygen supply and an anode for hydrogen supply; an electrolyte membrane provided between the cathode and the anode; and a reference electrode for hydrogen supply formed on one surface of the electrolyte membrane at a predetermined distance from the working electrode and a sub gasket surrounding the electrolyte membrane outside the working electrode and the reference electrode.

Description

A highly durable fuel cell system capable of resolving reverse voltage {A HIGHLY DURABLE FUEL CELL SYSTEM CAPABLE OF RELEASING CELL VOLTAGE REVERSAL}

The present invention relates to a fuel cell system including a configuration capable of solving the problem after checking whether a reverse voltage has occurred.

In general, a polymer electrolyte membrane fuel cell (PEMFC) is applied as a fuel cell for automobiles, and this polymer electrolyte membrane fuel cell normally exhibits high output performance of at least tens of kW under various driving conditions of automobiles. To do this, it must be able to operate reliably over a wide current density range. In general, a polymer electrolyte membrane fuel cell is used in the form of a stack in which unit cells are stacked and assembled to meet a required output level. In addition, a membrane-electrode assembly (MEA) is located at the innermost part of the unit cell configuration of the fuel cell stack, and this MEA is applied to both sides of the electrolyte membrane and the electrolyte membrane that can move hydrogen ions (Proton). It consists of an anode (Anode) and a cathode (Cathode). Hereinafter, the term “fuel cell” refers to a polymer electrolyte membrane fuel cell.

In addition, a gas diffusion layer (GDL) and a gasket are stacked on the outer part of the MEA, that is, the outer part where the anode and cathode are located, and the reactor body, cooling water, and water generated by the reaction are stacked on the outside of the GDL. A separator or bipolar plate providing a flow field is bonded. Looking at the electrochemical reaction for generating electricity in the polymer electrolyte membrane fuel cell, after hydrogen supplied to the anode, which is the anode of the fuel cell, is separated into hydrogen ions and electrons, the hydrogen ions move toward the cathode, which is the reduction electrode through the polymer electrolyte membrane. , The electrons move to the cathode through an external circuit, and oxygen molecules, hydrogen ions, and electrons react together at the cathode to generate electricity and heat, and at the same time, water as a reaction by-product is generated. The water generated during the electrochemical reaction in the fuel cell plays a desirable role in maintaining the humidification of the MEA if an appropriate amount is present.However, if excessive water is not properly removed, it is'water flooding or flooding' at a high current density. 'A phenomenon occurs, and the overflowed water plays a role in preventing the efficient supply of the reaction gases into the fuel cell cell, resulting in greater voltage loss.

It can be used when the performance is reversibly recovered, such as a phenomenon of'water flooding', in which the cell performance decreases by interfering with the flow of reaction gases (hydrogen and oxygen in the air) due to accumulation or accumulation of water in the fuel cell stack However, there is a limit to application in the irreversible deterioration mode. The problem of'Cell Voltage Reversal', which is a representative irreversible deterioration mode, is caused by various causes such as flooding of water in the fuel cell, ice formation in winter, and abnormality of the hydrogen fuel supply system. It occurs because of Hydrogen Fuel Starvation. It is known that the occurrence of a reverse voltage has a very fatal adverse effect on the performance of a fuel cell cell, thereby greatly reducing the cell voltage. In general, the hydrogen supply shortage is largely a phenomenon of'Overall Hydrogen Starvation' in which the supply of hydrogen to the entire fuel cell cell is insufficient, and hydrogen supply is sufficient but the supply of hydrogen is partially due to uneven distribution. It can be classified as a phenomenon of'local hydrogen starvation', which becomes scarce. This hydrogen shortage phenomenon frequently occurs in operating conditions such as uneven supply and distribution of hydrogen gas, sudden increase in fuel cell load demand, and fuel cell start-up. When the anode lacks hydrogen, the anode voltage (V _anode ) increases. However, if the anode voltage continues to increase, the anode voltage eventually increases _{compared to the cathode voltage (V cathode} ), resulting in a reverse voltage state in which the cell voltage (V _{cell ) becomes smaller than 0 (V cell} = V _cathode -V _anode <0). . In the reverse voltage state due to an increase in the anode voltage, first, a water electrolysis reaction occurs as shown in Reaction Equation 1 below.

[Scheme 1]

_{H 2 O → 1 / 2O 2} + 2H + + 2e -, E o = 1.229 V (vs SHE.)

However, where E ^o is the Standard Electrode Potential and SHE is the Standard Hydrogen Electrode.

However, if the anode voltage continues to increase after that, the carbon corrosion reaction at the anode is accelerated as shown in Reaction Equations 2 and 3 below.

[Scheme 2]

_{C + 2H 2 O → CO 2} + 4H + + 4e -, E o = 0.207 V (vs SHE.)

[Scheme 3]

_{C + H 2 O → CO +} 2H + + 2e -, E o = 0.518 V (vs SHE.)

If such a cell reverse voltage condition continues to reach an excessive reverse voltage state where the cell voltage is less than about -2V, the fuel cell cell heats up excessively, causing overall damage to the MEA and gas diffusion layer, and in particular, pinholes in the MEA. -Hole) occurs and the cell is electrically shorted, which may cause serious problems. In this case, a cell failure state is reached in which the fuel cell cell cannot be operated normally any more.

The overall hydrogen shortage phenomenon can be detected relatively easily by monitoring the hydrogen supply status using sensors in the fuel cell operation system (Balance Of Plant), but local hydrogen shortage phenomenon in some cells can be detected by each cell of the fuel cell stack. Because it can be detected only by closely monitoring with a Stack Voltage Monitoring device, much more effort and a complex control system are required.

Therefore, before reaching such a reverse voltage, it is important to properly control a vehicle equipped with a fuel cell so that it can operate stably, and to develop a fuel cell system and driving control technology having excellent durability against reverse voltage.

On the other hand, in the case of a cell voltage drop due to flooding of water, in the prior art, it was not clear whether it was caused by the anode or the cathode. There is a limit to normalizing the cell voltage by removing the water overflow phenomenon by increasing the supply of hydrogen to the anode and the air to the cathode without a clear judgment. Moreover, it was impossible to distinguish in advance whether the cell voltage drop was due to flooding of water at the cathode or reverse voltage at the anode.

Korean Registered Gazette No. 10-1405800 Korean Registered Gazette No. 10-0341435

Accordingly, in the present invention, it is intended to achieve normal vehicle driving even in a deterioration mode due to an irreversible reverse voltage by clearly determining in advance whether the cell voltage drop is due to an anode reverse voltage or a water overflow phenomenon of the cathode.

In addition, it is intended to propose a method to efficiently improve the durability of the vehicle by determining whether it is on the anode side or the cathode side in the event of water overflow.

In more detail, it is intended to independently measure the anode voltage and the cathode voltage by applying a cell including a reference electrode having a specification different from that of the main power stacked cell at an arbitrary position in the stack.

The object of the present invention is not limited to the object mentioned above. Objects of the present invention will become more apparent from the following description, and will be realized by means described in the claims and combinations thereof.

A fuel cell system according to an embodiment of the present invention includes a fuel cell stack including at least one membrane-electrode assembly; An oxygen supply unit supplying oxygen to the fuel cell stack; A hydrogen supply unit supplying hydrogen to the fuel cell stack; And a battery cell provided on at least one side of the fuel cell stack, wherein the battery cell includes a cathode supplied with oxygen and an anode supplied with hydrogen. ; An electrolyte membrane provided between the cathode and the anode; A reference electrode formed on one surface of the electrolyte membrane and supplied with hydrogen by being spaced apart from the working electrode by a predetermined distance, and a sub gasket surrounding the electrolyte membrane outside the working electrode and the reference electrode.

The fuel cell system may further include an insulator provided between the fuel cell stack and the battery cell.

The reference electrode may be formed on the electrolyte membrane on the same surface as the anode.

The battery cell further includes a housing provided on the reference electrode, wherein the housing includes at least one hydrogen passage through which hydrogen passes, a hydrogen inlet portion formed on one side of the hydrogen passage and into which hydrogen flows, and the hydrogen passage It may be formed on the other side of the to include a hydrogen discharge unit from which hydrogen is discharged.

The battery cell further includes a cathode separation plate provided on the cathode and an anode separation plate provided on the anode, and the cathode separation plate and the anode separation plate each include at least one channel portion through which the reactor body passes. It can be.

The fuel cell system includes a voltage measuring unit connected to said working electrode and said reference electrode for measuring the cathode voltage (V _cathode), the anode voltage (V _anode), and the cell voltage (V _cell) of the battery cell; And a control unit connected to the voltage measurement unit and controlling a supply amount of the reactor body supplied to the fuel cell stack based on a measurement result of the voltage measurement unit.

The control unit includes a determination module connected to the voltage measuring unit to determine whether a reverse voltage has occurred in the battery cell based on the values of the cathode voltage, the anode voltage, and the cell voltage received; And a flow rate control module connected to the determination module, the oxygen supply unit, and the hydrogen supply unit to adjust the supply amount of the reactor body supplied to the fuel cell stack according to a state determined by the determination module.

The determination module determines that a reverse voltage has occurred in the battery cell due to a lack of hydrogen supply when the anode voltage falls within 0.05V to 1.5V while the cell voltage is decreased, and the flow rate control module According to the determination, the amount of hydrogen supplied from the hydrogen supply unit may be increased.

The determination module has the anode voltage less than 0.05V in a state where the cell voltage is decreasing, and the ratio of the change amount of the cathode voltage (△V _cathode ) and the change amount of the anode voltage (△V _anode ) (△V _cathode /△ If V _anode ) is 1.5 to 2.5, it is determined that the cell voltage of the battery cell has decreased due to insufficient oxygen supply, and the flow control module increases the supply amount of oxygen supplied from the oxygen supply unit according to the determination of the determination module. I can.

The membrane-electrode assembly includes an anode, a cathode, and an electrolyte membrane positioned between the anode and the cathode, and a separation plate is provided between the membrane-electrode assembly, and the separation plate includes at least one channel portion through which the reactor body passes. Including, the content of the catalyst contained in the anode of the battery cell is 80% to 95% of the content of the catalyst contained in the negative electrode of the membrane-electrode assembly, the thickness of the anode of the battery cell is the membrane-electrode assembly 80% to 90% of the thickness of the negative electrode, the content of the ionomer contained in the anode of the battery cell is 125% to 190% of the content of the ionomer contained in the negative electrode of the membrane-electrode assembly, and the anode separation of the battery cell The cross-sectional area of the channel portion of the plate may be 85% to 95% of the cross-sectional area of the channel portion of the separator provided between the membrane-electrode assembly.

The membrane-electrode assembly includes an anode, a cathode, and an electrolyte membrane positioned between the anode and the cathode, and a separation plate is provided between the membrane-electrode assembly, and the separation plate includes at least one channel portion through which the reactor body passes. Including, the content of the catalyst contained in the cathode of the battery cell is 85% to 95% of the content of the catalyst contained in the positive electrode of the membrane-electrode assembly, the thickness of the cathode of the battery cell is the membrane-electrode assembly 80% to 90% of the thickness of the positive electrode, and the content of the ionomer contained in the cathode of the battery cell is 125% to 190% of the content of the ionomer contained in the positive electrode of the membrane-electrode assembly, and the cathode of the battery cell is separated The cross-sectional area of the channel portion of the plate may be 85% to 95% of the cross-sectional area of the channel portion of the separator provided between the membrane-electrode assembly.

The membrane-electrode assembly includes an anode, a cathode, and an electrolyte membrane positioned between the anode and the cathode, and a separation plate is provided between the membrane-electrode assembly, and the separation plate includes at least one channel portion through which the reactor body passes. Including, the content of the catalyst contained in the anode of the battery cell is 115% to 145% of the content of the catalyst contained in the negative electrode of the membrane-electrode assembly, the carbonization of the anode of the battery cell is the membrane-electrode assembly It may be 110% to 130% compared to the degree of carbonization of the negative electrode.

The fuel cell system according to the present invention can suppress the irreversible carbon corrosion reaction in advance when the reverse voltage occurs due to insufficient hydrogen at the anode, and detects the situation of shortage of hydrogen and air in advance to efficiently solve the problem of hydrogen shortage and insufficient air. It can be solved.

The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a cross-sectional view schematically showing a fuel cell system according to the present invention.
2 is a perspective view schematically showing a part of a fuel cell system according to the present invention.
3 is a cross-sectional view schematically showing a membrane-electrode assembly according to the present invention.
4 is a cross-sectional view schematically showing a battery cell according to the present invention.
5 is a circuit diagram schematically showing a structure for measuring a voltage of a battery cell according to the present invention.
6 is a block diagram schematically showing a voltage measuring unit and a control unit included in the fuel cell system according to the present invention.

The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments related to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In describing each drawing, similar reference numerals have been used for similar elements. In the accompanying drawings, the dimensions of the structures are shown to be enlarged than actual for clarity of the present invention.

In the present specification, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance the possibility of the presence or addition. Further, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where the other part is "directly above", but also the case where there is another part in the middle. Conversely, when a part such as a layer, a film, a region, or a plate is said to be "under" another part, this includes not only the case where the other part is "directly below", but also the case where there is another part in the middle.

Unless otherwise specified, all numbers, values, and/or expressions expressing quantities of ingredients, reaction conditions, polymer compositions, and formulations used herein are those that occur in obtaining these values, among other things essentially. Since they are approximations that reflect the various uncertainties of the measurement, it should be understood as being modified in all cases by the term "about". In addition, when numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values from the minimum value of this range to the maximum value including the maximum value. Furthermore, where this range refers to an integer, all integers from the minimum to the maximum value including the maximum value are included, unless otherwise indicated.

1 is a cross-sectional view schematically showing a fuel cell system according to the present invention. 2 is a perspective view schematically showing a part of a fuel cell system according to the present invention.

1 and 2, the fuel cell system includes a fuel cell stack 10 including at least one membrane-electrode assembly 11, and an oxygen supply unit supplying oxygen to the fuel cell stack 10 ( 20), a hydrogen supply unit 30 for supplying hydrogen to the fuel cell stack 10, a battery cell 40 and the fuel cell stack 10 provided on at least one side of the fuel cell stack 10, and / Or includes a pair of end plates 60 installed on the outside of the battery cell 40.

The fuel cell stack 10 may be formed by stacking a plurality of membrane-electrode assemblies 11 through a separator 12.

3 is a schematic cross-sectional view of the membrane-electrode assembly 11. Referring to this, the membrane-electrode assembly 11 may include an anode 111, a cathode 112, and an electrolyte membrane 113 positioned between the anode 111 and the cathode 112.

Hydrogen supplied to the cathode 112 is decomposed into ^{electrons and protons (H + ).} The electrons flow to the anode through an electric circuit (not shown), and protons (H ⁺ ) move to the anode 111 through the electrolyte membrane 113. In the anode 111, protons combine with electrons and oxygen supplied to the anode 111 to produce water and heat.

The separating plate 12 is configured to separate a plurality of membrane-electrode assemblies 11, and each separating plate 12 has at least one channel to allow hydrogen and oxygen to pass through the fuel cell stack 10. May include sub (not shown). The shape and position of the channel portion are not particularly limited, and may be appropriately formed according to the shape of the fuel cell stack.

The oxygen supply unit 20 is located outside the fuel cell stack 10 and supplies oxygen to the fuel cell stack 10 and/or the battery cell 40.

The oxygen supply unit 20 may include an oxygen tank 21 storing oxygen and an oxygen supply path 22 supplying the oxygen to the fuel cell stack 10 and/or the battery cell 40. . However, when using external air instead of oxygen, an air blower communicating with the outside may be installed in the oxygen supply unit 20. In addition, when oxygen and external air are selectively used, both the oxygen tank 21 and the air blower may be installed in the oxygen supply unit 20.

The hydrogen supply unit 30 may include a hydrogen tank 31 storing hydrogen and a hydrogen supply path 32 supplying the hydrogen to the fuel cell stack 10 and/or the battery cell 40. .

The oxygen supply unit 20 may supply the oxygen to the fuel cell stack 10 and the battery cell 40 through the same path. However, the oxygen supply unit 20 may supply the oxygen to the fuel cell stack 10 and the battery cell 40 through a separate path. A specific method thereof is not particularly limited, and may be implemented by installing a plurality of the oxygen supply units 20, or separately installing the oxygen supply path 32 and the oxygen inlet 61 of the end plate to be described later. .

The hydrogen supply unit 30 may supply the hydrogen to the fuel cell stack 10 and the battery cell 40 through the same path. However, the hydrogen supply unit 30 may supply the hydrogen to the fuel cell stack 10 and the battery cell 40 through a separate path. A specific method thereof is not particularly limited, and may be implemented by installing a plurality of the hydrogen supply units 30, or separately installing the hydrogen supply path 32 and the hydrogen inlet 63 of the end plate to be described later. .

The fuel cell system may further include a coolant supply unit (not shown) that supplies coolant to the fuel cell stack 10. The coolant supply unit may include a coolant tank storing coolant and a coolant supply path for supplying the coolant to the fuel cell stack.

The fuel cell system may include a pair of end plates 60 installed outside the fuel cell stack 10 and/or the battery cell 40. The end plate 60 includes an oxygen inlet 61 through which oxygen introduced from the oxygen supply unit 20 passes, an oxygen outlet 62 through which oxygen discharged from the fuel cell stack 10 passes, and the hydrogen supply unit 30 A hydrogen inlet 63 through which hydrogen introduced from) passes and a hydrogen outlet 64 through which hydrogen discharged from the fuel cell stack 10 passes. Their shape and position are not particularly limited, and may be appropriately formed in consideration of the arrangement and size of each component of the fuel cell system.

The end plate 60 may include a cooling water inlet (not shown) through which the cooling water introduced from the cooling water supply unit passes, and a cooling water outlet (not shown) through which the cooling water discharged from the inside thereof passes.

4 is a schematic cross-sectional view of the battery cell 40. Referring to this, the battery cell 40 is provided between a working electrode 41 including a cathode 41a and an anode 41b, and between the cathode 41a and the anode 41b. A reference electrode 43 and the working electrode 41 formed on any one surface of the electrolyte membrane 42 by being spaced apart from the working electrode 41 by a predetermined distance and supplied with hydrogen. And a sub gasket 44 surrounding the electrolyte membrane 42 outside the reference electrode 43. Here, the "working electrode" means including a general working electrode and a counter electrode. When the anode is the working electrode, the cathode becomes the counter electrode, and when the cathode is the working electrode, the anode becomes the counter electrode.

The present invention is characterized in that the fuel cell system includes at least one battery cell 40 including the reference electrode 43. The structure of the cathode 41a and the anode 41b of the battery cell, the supply of oxygen and hydrogen to them, and the structure of the overall cell are substantially the same as those of the membrane-electrode assembly 11 described above. However, in the present invention, by adding the reference electrode 43 to the battery cell 40, the cathode voltage (V _cathode ) and the anode voltage (V _anode ) of the battery cell 40 can be independently measured. Accordingly, it is possible to check in real time whether a reverse voltage is generated in the fuel cell system, and since the causing electrode can be clearly determined, it is possible to effectively respond to the reverse voltage. This will be described in detail later.

The fuel cell system may include at least one or more of the battery cells 40. It may be installed at one of both ends of the fuel cell stack 10 or may be installed at both ends of the fuel cell stack 10. In addition, the battery cell 40 may be installed inside the fuel cell stack 10.

The battery cell 40 is configured to function as a sensor capable of detecting the occurrence of a kind of reverse voltage. Accordingly, the same electrical load as the fuel cell stack 10 is applied to the battery cell 40. That is, the current loaded per unit area of the working electrode 41 of the battery cell 40 is the same as that of the pair of electrodes of the membrane-electrode assembly 11. However, in order to exclude the influence of the fuel cell stack 10 on the battery cell 40, an insulator 50 may be installed between the battery cell 40 and the fuel cell stack 10.

Any insulator 50 may be used as long as it can electrically separate the fuel cell stack 10 and the battery cell 40 from each other. For example, glass fiber reinforced plastics (GFRP); And/or carbon steel may be coated with a fluorine-based resin. The fluorine-based resin may include Polytetrafluoroethylene (PTFE), Fluorinated Ethylene Propylene (FEP), Perfluoroalkoxy Alkanes (PFA), Ethylene Tetrafluoroethylene (ETFE), and the like.

The cathode 41a and the anode 41b are operating electrodes 41 of the battery cell, and may each include a catalyst and an ionomer.

The catalyst is not particularly limited, but platinum (Pt), ruthenium (Ru), rhodium (Rh), nickel (Ni), osmium (Os), manganese (Mn), titanium (Ti), zirconium (Zr), tungsten ( W), iron (Fe), molybdenum (Mo), iridium (Ir), tin (Sn) may include two or more binary, ternary, quaternary metal catalysts selected from the group consisting of.

The ionomer is not particularly limited, but may include a fluorine-based ionomer such as Nafion ionomer (trade name of Du Pont).

Gas diffusion layers 45a and 45b may be further provided on the cathode 41a and the anode 41b, respectively. The gas diffusion layers 45a and 45b are for smoothly supplying a reactive body to each of the cathode 41a and the anode 41b, and may include a sheet-like substrate such as fabric, paper, and nonwoven fabric made of carbon.

The electrolyte membrane 42 is configured to allow protons generated in the anode 41b to move to the cathode 41a. The electrolyte membrane 42 is not particularly limited, but may include a fluorine-based ionomer such as Nafion ionomer or a fluorine-based ionomer impregnated with expanded-polytetrafluoroethylene (e-PTFE).

The battery cell 40 may further include a cathode separator 46a provided on the cathode 41a and an anode separator 46b provided on the anode 41b. The cathode separating plate 46a and the anode separating plate 46b may each include at least one channel portion 47 and 47' through which the reactor body passes. In addition, the cathode separating plate 46a and the anode separating plate 46b may further include passages (not shown) through which cooling water passes.

The electrolyte membrane 42 may extend outside the working electrode 41 to provide a space in which the reference electrode 43 is to be formed. In addition, a sub gasket 44 surrounding the electrolyte membrane 42 may be installed outside the working electrode 41 and the reference electrode 43 to prevent the electrolyte membrane 42 from being exposed. Accordingly, moisture in the electrolyte membrane 42 can be easily managed, and the cathode voltage and anode voltage of the battery cell 40 can be stably measured.

The reference electrode 43 may be formed on the electrolyte membrane 42 on the same surface as the anode 41b. In addition, by supplying hydrogen to the reference electrode 43, the reference electrode 43 may function as a hydrogen electrode in the battery cell 40.

The reference electrode 43 may include a catalyst and an ionomer. The catalyst is not particularly limited, but platinum (Pt), ruthenium (Ru), rhodium (Rh), nickel (Ni), osmium (Os), manganese (Mn), titanium (Ti), zirconium (Zr), tungsten ( W), iron (Fe), molybdenum (Mo), iridium (Ir), tin (Sn) may include two or more binary, ternary, quaternary metal catalysts selected from the group consisting of. The ionomer is not particularly limited, but may include a fluorine-based ionomer such as Nafion ionomer (trade name of Du Pont). The catalyst and the ionomer may be the same as or different from those of the working electrode 41.

A gas diffusion layer 45c may be further provided on the reference electrode 43. The gas diffusion layer 45c is for smoothly supplying the reactive body to the reference electrode 43, and may include a sheet-like substrate such as a fabric, paper, or nonwoven fabric made of carbon.

The battery cell 40 may further include a housing 48 provided on the reference electrode 43. The housing 48 may be installed to cover all of the reference electrode 43 and the electrolyte membrane 42 on which the reference electrode 43 is formed, and a predetermined portion of the sub gasket 44 surrounding the reference electrode 43.

The housing 48 includes at least one hydrogen passage 48a through which hydrogen passes, a hydrogen inlet 48b formed on one side of the hydrogen passage 48a and into which hydrogen flows, and the other side of the hydrogen passage 48a. It is formed in and may include a hydrogen discharge unit (48c) from which hydrogen is discharged. Hydrogen introduced from the outside is provided to the reference electrode 43 through the hydrogen flow path 48a through the hydrogen inlet 48b, and then discharged to the outside through the hydrogen discharge part 48c.

Hydrogen supplied to the housing 48 is introduced by forming a separate flow path (not shown) in the hydrogen supply unit 30, or a separate hydrogen supply device (not shown) distinguished from the hydrogen supply unit 30 is provided. It can be installed and introduced.

As described above, the fuel cell system according to the present invention includes a fuel cell stack 10 and a battery cell 40 electrically separated therefrom. Since the fuel cell stack 10 and the battery cell 40 are driven in substantially the same environment, the state of the fuel cell stack 10 can be inferred by monitoring the state of the battery cell 40.

In the present invention, by installing a reference electrode 43 in addition to the working electrode 41 to monitor the state of the battery cell 40, the cathode voltage and the anode voltage of the battery cell 40 can be independently measured. It is characterized. 5 is a circuit diagram schematically showing a structure for measuring the voltage of the battery cell 40. Since the battery cell 40 includes the reference electrode 43, a cathode voltage (V _cathode ) and an anode voltage (V _anode ) can be independently measured based on the voltage, and accordingly, the The cell voltage (V _cell = V _cathode -V _anode ) can be calculated.

If it is determined that the cell voltage drop has occurred in the battery cell 40, it can be inferred that the same or similar phenomenon has occurred in the fuel cell stack 10. However, this alone does not know whether the cell voltage drop is caused by insufficient supply of hydrogen or insufficient supply of oxygen. In other words, it is difficult to adequately cope with the cause of the cell voltage drop since it is not known.

The present invention determines the cause of the cell voltage drop based on the measured cathode voltage, anode voltage, and cell voltage of the battery cell 40 based on the fact that the patterns of the cathode voltage and the anode voltage appear different depending on the cause of the cell voltage drop. It is characterized in that it is possible to respond appropriately. It will be described in detail below.

6 is a block diagram schematically showing the voltage measurement unit 70 and the control unit 80 provided in the fuel cell system according to the present invention. Referring to this, the fuel cell system is connected to the working electrode 41 and the reference electrode 43 to be connected to the cathode voltage (V _cathode ), the anode voltage (V _anode ), and the cell voltage (V _cell ) independently measuring and calculating a voltage measurement unit 80 and a reaction connected to the voltage measurement unit 80 and supplied to the fuel cell stack 10 based on the measurement result of the voltage measurement unit 80 It may include a control unit 90 for adjusting the supply amount of gas.

The voltage measurement unit 80 is electrically connected to the working electrode 41 and the reference electrode 43 to measure a cathode voltage and an anode voltage of the battery cell 40 as shown in FIG. 5. , A calculation module 82 for calculating a cell voltage using the cathode voltage and the anode voltage measured by the measurement module 81, and the value measured by the measurement module 81 and the calculation module 82, the control unit ( It may include a transmission module 83 that transmits to 90).

The measurement module 81 is not particularly limited, and an appropriate module may be selected according to the use of various measurement methods such as a current-voltage measurement method, a current cutoff measurement method, an impedance spectroscopy method, and a cyclic voltammetry method.

The transmission module 83 may use any one as long as it can transmit the measured value of the measurement module 81 and the calculated value of the calculation module 82, for example, a wired module; Alternatively, it may be a wireless module such as Wi-Fi, Bluetooth, or ZigBee module.

The control unit 90 is connected to the voltage measuring unit 80 and a determination module 91 that determines whether a cell voltage drop has occurred in the battery cell 40 through the values of the cathode voltage, anode voltage, and cell voltage received. ); And connected to the determination module 91, the oxygen supply unit 20, and the hydrogen supply unit 30 to adjust the supply amount of the reactor body supplied to the fuel cell stack 10 according to the state determined by the determination module 91. It includes a flow control module 92.

When a reverse voltage occurs in the fuel cell due to insufficient supply of hydrogen, the cell voltage decreases and the anode voltage increases due to the formation of an overvoltage. At the same time, the cathode voltage also decreases, but it changes gently compared to the anode voltage, and does not drop below 0 V, but shows a relatively constant voltage.

On the other hand, when the cell voltage of the fuel cell decreases due to insufficient supply of oxygen, the anode voltage slightly increases, but the cathode voltage decreases before that.

That is, when the reverse voltage occurs due to insufficient supply of hydrogen and when the cell voltage decreases due to insufficient supply of oxygen, the situation is different from each other.

Therefore, the determination module 91 determines that a reverse voltage has occurred in the battery cell 40 due to a shortage of hydrogen supply when the anode voltage falls within the 0.05V to 1.5V state while the cell voltage decreases, and the flow rate The control module 92 transmits a signal for increasing the supply amount of hydrogen supplied from the hydrogen supply unit 30 according to the determination of the determination module 91. For reference, if the lower limit of the numerical range of the anode voltage is less than 0.05 V, control may become too sensitive, and if the upper limit exceeds 1.5 V, an irreversible carbon corrosion reaction may occur in the battery cell.

On the other hand, the determination module 91 is the anode voltage is less than 0.05V in a state in which the cell voltage is decreased, and the ratio of the change amount of the cathode voltage (ΔV _cathode ) and the change amount of the anode voltage _{(ΔV anode} ) ( If ΔV _cathode / _{ΔV anode} ) is 1.5 to 2.5, it is determined that the cell voltage drop of the battery cell 40 has occurred due to insufficient oxygen supply, and the flow control module 92 determines the determination module 91 Accordingly, a signal for increasing the amount of oxygen supplied from the oxygen supply unit 20 is transmitted.

The control unit 90 may further include a transmission/reception module 93 for receiving a value such as a cathode voltage transmitted from the voltage measuring unit 80 and transmitting a signal generated by the flow rate control module 92. have. The transmission/reception module 93 is not particularly limited, and includes, for example, a wired module; Alternatively, it may be a wireless module such as Wi-Fi, Bluetooth, or ZigBee module.

According to the present invention, in order to further improve the durability of the fuel cell system, the battery cell 40 is more capable of supplying hydrogen and/or oxygen than the membrane-electrode assembly 11 included in the fuel cell stack 10. It can also be sensitively formed. That is, when an abnormality occurs in the fuel cell system, the reverse voltage is artificially generated in the battery cell 40 before the fuel cell stack 10. Accordingly, measures can be taken before the reverse voltage is generated in the fuel cell stack 10.

The first embodiment of the fuel cell system is to lower the hydrogen oxidation reactivity of the battery cell 40. Specifically, in the fuel cell system, the content of the catalyst included in the anode 41b of the battery cell 40 is 80% to 95% compared to the content of the catalyst included in the anode 112 of the membrane-electrode assembly 11 And, the thickness of the anode 41b of the battery cell 40 is 80% to 90% of the thickness of the negative electrode 112 of the membrane-electrode assembly 11, and the anode 41b of the battery cell 40 The content of ionomer contained in the membrane-electrode assembly 11 is 125% to 190% of the content of the ionomer contained in the negative electrode 112 of the membrane-electrode assembly 11, and the channel portion of the anode separator 46b of the battery cell 40 The cross-sectional area of (47') may be 85% to 95% of the cross-sectional area of the channel portion (not shown) of the separator 12 provided between the membrane-electrode assembly 11.

In addition, in order to further lower the hydrogen oxidation reactivity of the battery cell 40, the anode separator 46b of the battery cell 40 and the gas diffusion layer 45b provided on the anode 41b may be hydrophilized.

In the second embodiment of the fuel cell system, the oxygen reduction reactivity of the battery cell 40 is reduced. Specifically, in the fuel cell system, the content of the catalyst contained in the cathode 41a of the battery cell 40 is 85% to 95% of the content of the catalyst contained in the anode 111 of the membrane-electrode assembly 11 And, the thickness of the cathode 41a of the battery cell 40 is 80% to 90% of the thickness of the positive electrode 111 of the membrane-electrode assembly 11, and the cathode 41a of the battery cell 40 The content of the ionomer contained in the membrane-electrode assembly 11 is 125% to 190% of the content of the ionomer contained in the anode 111 of the membrane-electrode assembly 11, and the channel portion of the cathode separator 46a of the battery cell 40 The cross-sectional area of 47 may be 85% to 95% of the cross-sectional area of the channel portion (not shown) of the separator 12 provided between the membrane-electrode assembly 11.

In addition, in order to further reduce the oxygen reduction reactivity of the battery cell 40, the cathode separator 46a of the battery cell 40 and the gas diffusion layer 45a provided on the cathode 41a may be hydrophilized. .

The third embodiment of the fuel cell system improves the robustness of the battery cell 40 against a reverse voltage. Here, "robustness against reverse voltage" means the degree to which the battery cell 40 does not lose its function even if the reverse voltage is frequently generated in the battery cell 40. As described above, when the battery cell 40 is sensitive to the supply of hydrogen and oxygen, a reverse voltage occurs relatively frequently in the battery cell 40. In this case, if the robustness against the reverse voltage of the battery cell 40 is low, the fuel cell system may not operate smoothly due to a failure of the battery cell 40. In the fuel cell system of the third embodiment, the content of the catalyst included in the anode 41b of the battery cell 40 is compared with the content of the catalyst included in the anode 112 of the membrane-electrode assembly 11. % To 145%, and the carbonization degree of the anode 41b of the battery cell 40 may be 110% to 130% of the carbonization degree of the negative electrode 112 of the membrane-electrode assembly 11. Here, "carbonization degree" means the proportion of carbon in the remaining components excluding moisture and ash in the carbon material.

As described in detail above, the scope of the present invention is not limited to the above-described embodiments, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims It is also included in the scope of the present invention.

10: fuel cell stack
11: membrane-electrode assembly 111: anode 112: cathode 113: electrolyte membrane
12: Separation plate
20: oxygen supply unit 21: oxygen tank 22: oxygen supply path
30: hydrogen supply unit 31: hydrogen tank 32: hydrogen supply path
40: battery cell 41: working electrode 41a: cathode 41b: anode
42: electrolyte membrane 43: reference electrode 44: sub gasket
45a: cathode gas diffusion layer 45b: anode gas diffusion layer
46a: cathode separation plate 46b: anode separation plate
47, 47': channel part
48: housing 48a: hydrogen flow path 48b: hydrogen inlet 48c: hydrogen outlet
50: insulator 60: end plate
80: voltage measurement unit 81: measurement module 82: calculation module 83: transmission module
90: control unit 91: determination module 92: flow control module 93: transmission/reception module

Claims (12)

A fuel cell stack including at least one membrane-electrode assembly;
An oxygen supply unit supplying oxygen to the fuel cell stack;
A hydrogen supply unit supplying hydrogen to the fuel cell stack; And
Including a battery cell provided on at least one side of the fuel cell stack,
The battery cell includes a working electrode including a cathode to which oxygen is supplied and an anode to which hydrogen is supplied; An electrolyte membrane provided between the cathode and the anode; A fuel cell comprising a reference electrode formed on one side of the electrolyte membrane and supplied with hydrogen by a predetermined distance from the working electrode, and a sub gasket surrounding the electrolyte membrane outside the working electrode and the reference electrode. system. The method of claim 1,
The fuel cell system further comprising an insulator provided between the fuel cell stack and the battery cell. The method of claim 1,
The fuel cell system wherein the reference electrode is formed on the electrolyte membrane on the same surface as the anode. The method of claim 1,
The battery cell further includes a housing provided on the reference electrode,
The housing includes at least one hydrogen flow path through which hydrogen passes, a hydrogen inlet part formed on one side of the hydrogen flow path and into which hydrogen is introduced, and a hydrogen discharge part formed on the other side of the hydrogen flow path and through which hydrogen is discharged. Battery system. The method of claim 1,
The battery cell further includes a cathode separator provided on the cathode and an anode separator provided on the anode,
The cathode separator and the anode separator each include at least one channel portion through which the reactor body passes. The method of claim 1,
A voltage measuring unit connected to the working electrode and the reference electrode to measure a cathode voltage (V _cathode ), an anode voltage (V _anode ), and a cell voltage (V _{cell) of the battery cell;} And
The fuel cell system further comprises a control unit connected to the voltage measurement unit and controlling a supply amount of the reactor body supplied to the fuel cell stack based on a measurement result of the voltage measurement unit. The method of claim 6,
The control unit includes a determination module connected to the voltage measuring unit to determine whether a reverse voltage has occurred in the battery cell based on the values of the cathode voltage, the anode voltage, and the cell voltage received; And a flow rate control module connected to the determination module, the oxygen supply unit, and the hydrogen supply unit to adjust the supply amount of the reactor body supplied to the fuel cell stack according to a state determined by the determination module. The method of claim 7,
The determination module determines that a reverse voltage has occurred in the battery cell due to insufficient hydrogen supply when the anode voltage falls within 0.05V to 1.5V while the cell voltage decreases,
The fuel cell system, wherein the flow rate control module increases the supply amount of hydrogen supplied from the hydrogen supply unit according to the determination of the determination module. The method of claim 7,
The determination module is in a state where the cell voltage is decreased, the anode voltage is less than 0.05V, and the ratio of the change amount of the cathode voltage (△V _cathode ) and the change amount of the anode voltage (△V _anode ) (△V _cathode /△ If V _anode ) is 1.5 to 2.5, it is determined that the cell voltage of the battery cell has decreased due to insufficient oxygen supply,
The fuel cell system wherein the flow rate control module increases the amount of oxygen supplied from the oxygen supply unit according to the determination of the determination module. The method of claim 1,
The membrane-electrode assembly includes an anode, a cathode, and an electrolyte membrane positioned between the anode and the cathode,
A separation plate is provided between the membrane-electrode assembly, and the separation plate includes at least one channel portion through which the reactor body passes,
The content of the catalyst contained in the anode of the battery cell is 80% to 95% compared to the content of the catalyst contained in the negative electrode of the membrane-electrode assembly,
The thickness of the anode of the battery cell is 80% to 90% of the thickness of the negative electrode of the membrane-electrode assembly,
The content of the ionomer contained in the anode of the battery cell is 125% to 190% compared to the content of the ionomer contained in the negative electrode of the membrane-electrode assembly,
A fuel cell system in which the cross-sectional area of the channel portion of the anode separator of the battery cell is 85% to 95% of the cross-sectional area of the channel portion of the separator provided between the membrane-electrode assembly. The method of claim 1,
The membrane-electrode assembly includes an anode, a cathode, and an electrolyte membrane positioned between the anode and the cathode,
A separation plate is provided between the membrane-electrode assembly, and the separation plate includes at least one channel portion through which the reactor body passes,
The content of the catalyst contained in the cathode of the battery cell is 85% to 95% compared to the content of the catalyst contained in the positive electrode of the membrane-electrode assembly,
The thickness of the cathode of the battery cell is 80% to 90% of the thickness of the anode of the membrane-electrode assembly,
The content of the ionomer contained in the cathode of the battery cell is 125% to 190% compared to the content of the ionomer contained in the positive electrode of the membrane-electrode assembly,
A fuel cell system in which the cross-sectional area of the channel portion of the cathode separator of the battery cell is 85% to 95% of the cross-sectional area of the channel portion of the separator provided between the membrane-electrode assembly. The method of claim 1,
The membrane-electrode assembly includes an anode, a cathode, and an electrolyte membrane positioned between the anode and the cathode,
A separation plate is provided between the membrane-electrode assembly, and the separation plate includes at least one channel portion through which the reactor body passes,
The content of the catalyst contained in the anode of the battery cell is 115% to 145% compared to the content of the catalyst contained in the negative electrode of the membrane-electrode assembly,
A fuel cell system in which the carbonization degree of the anode of the battery cell is 110% to 130% of the carbonization degree of the negative electrode of the membrane-electrode assembly.

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