JPS5983358A - Fuel battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fuel cells, and more particularly to fuel cells having a laminated porous matrix assembly disposed between the electrodes of the cell, in which individual thin layers t''' During the occurrence of
When this different %L electrolyte is required, it has a different porosity to distribute the electrolyte in the region between 11:1iii.

Much research has been carried out in the area of fuel cell technology in order to provide ever-increasing amounts of electrical power and to allow such batteries to operate over long periods of time without any need for shutdown to achieve maintenance. .

Compared to other methods of generating electricity from combustible fuels, fuel cells have a high efficiency and are characterized by the simplicity of their physical construction, in that such cells can be constructed without any moving parts. It is said that

Although various electrochemical reactions are known for converting fuels into electricity by direct combustion of such fuels, one well-known type of battery is one in which hydrogen is used as a fuel, oxygen It utilizes the reaction between and hydrogen. hydrogen·
One common type of structure for oxygen cell reservoirs is that the electrolyte is maintained by a porous layer holding the electrolyte = lff
It is a laminated structure that is separated by two layers. For example, electric jIl′F
The liquid is concentrated phosphoric acid. Hydrogen is guided by a passage after the active region of the anode, and oxygen is guided by a passage after the active region of the anode.

At the cathode, hydrogen gas is separated into hydrogen ions plus electrons in the presence of a catalyst, typically a noble metal such as platinum or other metals including platinum. Hydrogen ions move to the anode via spear dissolution in the process that constitutes ion current transfer, while electrons move to the anode via an external circuit. In the presence of a catalyst at the anode, hydrogen ions,
Electrons and oxygen molecules combine to produce water.

In order to provide the physical location of the respective reactants in the anode and cathode catalyst layers, layers of materials having hydrophilic and hydrophobic properties are placed in an adjacent arrangement with the catalyst layers. These allow the electrolyte and oxygen at the anode and hydrogen at the anode to contact the catalyst layer. The hydrophobic material has pores 2 of sufficiently large size to allow gaseous hydrogen and gaseous oxygen to flow freely through the material into contact with the catalyst.

For details of the structure of the fuel cell and its constituent parts, see Ad, l.
U.S. Patent No. 3.453.149 and 1 to H. ard.
Bushnell U.S. Pat. No. 4.064. , No. 322. The two Korekasa patents show structures for guiding gaseous reactants into the region of the catalyst. Additionally, the 1 Jush, Nell patent discloses an electrolyte storage reservoir within the battery to compensate for any changes in the amount of electrolyte applicable to ion transfer. A cell assembly that combines multiple fuel cells together in a single power source is from Acl lh, art USA! 1
♀r'l-4th. ], No. 75.165.

This patent also shows a reservoir manifold for the simultaneous supply of reactant gases to the cathode and anode of each cell. All three patents mentioned above are incorporated herein by reference.

During operation of a fuel cell, the problem arises that the cell suffers loss of electrolyte. For example, as a result of changes in the volume of the electrolyte, such as due to changes in temperature and composition, the electrolyte can be driven out of the matrix and permanently lost from use within the matrix. Fuel cells have limited capacity for additional electrolyte storage within them. Therefore, the amount of storage capacity limits the amount of time a fuel cell can operate before shutting down for maintenance. Such maintenance includes replenishing the amount of electrolyte at the required concentration.

Problems associated with distributing the electrolyte within the porous layer between the electrodes have been discovered. The electrolyte is typically distributed fairly uniformly throughout the porous layer during the formation of the cell.However, thereafter during operation of the cell, the distribution of the dissolution is For example, the losses are higher at the edges of the cell than in the medium heat section.The porous layer prevents the initial charge of the electrolyte (even if it breaks the , the fast or slow movement of the electrolyte across the layer does not allow adequate compensation for selective reduction of the electrolyte along the electrodes and at different locations along the layer. These vanishing areas create spaces through which oxygen and hydrogen can mix with significant damage to the cell.

Attempts to solve the above-mentioned problems by using larger or smaller pores in such porous skins do little to solve this problem. Increasing the pore size reduces capillary forces 7 and thus reduces the layer as a barrier to mixing of gaseous reactants. Reducing the pore size reduces the fluid movement rate and thus reduces the possibility of maintaining uniform distribution of the electrolyte.

Still other problems arise from the complexity of the structures required to direct the electrocatalyst from the storage region to the electrochemically active region along the catalyst layer. Such an electrolyte introducing structure is the above-mentioned Bus.
It is described in the patent of Hnell. In particular, it should be noted that such structures tend to increase the thickness of the cell, increase the resistive losses associated with current flow, and reduce the surface area available for electrochemical reactions. be.

A fuel cell constructed according to the invention, in which the fuel cell has a layered structure and the electrodes are separated by layers of different porosity, overcomes the above-mentioned problems and provides other advantages. . In a preferred embodiment h1a of the invention, the porous material is provided as a matrix assembly with a central layer of relatively large pores. The central layer has relatively small porosity and is disposed between two microlayers located on either side of the central layer. At least one of the 7-trix layers must be an electronic non-conductor. Either the large pore material or the small pore material can be made from sheets of fibrous carbon as long as the other is an electronic non-conductor. IJ assembly (m, atrix asse) between the two electrodes
The matrix assembly is used to apply an electrolyte to the space between the anode and cathode by placing a fluid reactant, a gaseous reactant, at the electrode. hydrogen is applied to the cathode and oxygen is applied to the anode. The electrolyte placement between the two electrodes (emplace - ηtent ) is provided for an ion conduction path, allowing hydrogen ions to propagate from the cathode to the anode, while electrons are transferred from the cathode to the anode through which the fuel cell is connected. It travels through the external circuit that is connected.

According to a main feature of the invention, large pores in the central layer of the matrix assembly permit total flow of electrolyte into universal locations within the central layer. According to another feature of the invention, electrolyte flow is allowed from an external reservoir to the battery. The central portion is provided with means for holding and transporting the electrolyte, whereby the electrolyte is drawn around the central layer for uniform distribution. Since fuel cells avoid the use of complex structures for electrolyte conduction and storage reservoirs within the cell, the central layer provides internal storage for electrolyte reservoirs without adding complexity to the cell structure. . The outer layer of the matrix assembly, which has smaller pores, attracts and strongly retains the electrocatalytic liquid that contacts the catalyst layer of the electrode. Because the electrolyte is held tightly within the pores of the outer layer of the matrix assembly, the outer layer effectively serves as a barrier to the flow of fluid or gaseous reactants.

According to still other features of the invention, the external reservoir is
It is connected to the central layer via a supply means such as a tube for storing the liquid and for replenishing the electrolyte. Electricity Q from external storage tank
The addition of electrolyte to the IJ assembly compensates for changes in the volume of electrolyte within the battery.

The central layer has good in-plane translocation Qr (in-plane transpo
rt) Must have 71￥ characteristics. Since the cell can be operated at atmospheric pressure, the electrolyte can therefore flow freely through the supply means according to said volume change.

The above aspects and other advantages of the invention can be seen in the accompanying drawings.
It is mentioned in the following article mentioned in .

The only figure shows the fuel cell IO in a perspective view. A second battery 1 has the same structure as the battery IO, one part of the oA is shown by the phantom line, and the battery IO is normally
One of many such cells placed in a stack (not shown) is placed adjacent to cell 10, as in the i11 solution. The communication of cells IO and 10A via the reactant transport reservoir manifold is shown schematically. Two such representative manifolds are shown: manifold 12 for the delivery of hydrogen to the cathode of each cell in the stack, and manifold 14 for the delivery of oxygen to the anode of each cell in the stack. There is. Although manifolds 12 and 14 are shown in a symbolic manner in the figure, a single manifold for each reactant reservoir flowing along the side of the stack carries reactants to the cell through respective passages 26. You will understand that we can supply it.

The fuel cell lO has two electrodes, i.e. a matrix 22, 11
The cathode 18, which is separated by the L solution, meets the cathode 20. Each 112 pole is adjacent to a solid, non-porous gas distribution plate 24. The top of the cell in the figure is plate 24, which has a groove to introduce and distribute only one reactant since it is at the end of the stack.
have. The plates 24 on the other side of the cell shown are bipolar made of two gas distribution plates 24 in back-to-back position for supplying reactants to the cell shown and an adjacent cell (not shown). This is a part of the plate.

The double-edged plate 24 provides passages 2 for the inlet of fluid, i.e. gaseous, reactants and for the removal of any residual gases.
6. Each electrode includes a hydrophobic substrate layer 28 and a catalyst 3
Contains 0. The plate 24 of the battery IOA comprises a series interconnection of two batteries.

Matrix assembly 22 includes a permeable central layer 32 of fibrous carbon sheet material having relatively large pores;
The central layer 32 is positioned between two permeable outer layers 34 having pores smaller than those of the central 7M 32. An electrolyte, typically phosphoric acid, is impregnated within the central layer 32. The pores in the center layer 32 are large enough to allow electrolyte to move freely through the center layer 32 to replenish the electrolyte within the VCC cell when necessary. The central layer 32 does not necessarily need to be completely filled with electrolyte, it is only necessary to provide sufficient electrolyte to ensure ionic conductivity between the electrodes 18 and 20.

The sterile pores of the outer layer 34 contain strong capillary forces that draw electrolyte from the central layer 32 to completely fill the outer layer 34 . The layer 34 has a rapid absorption capacity (fa, straf,
e of uptaJce).

By providing a uniform electrolyte to the H 34, each outer layer 34 serves as a barrier to the influx of reactive forces into the matrix assembly region.

Thus, the electrolyte is present in each of the three layers of the 7-trix assembly 22 to provide ionic conductivity to the matrix assembly 22, and the matrix assembly 22, along with the electrolyte therein, It serves as a pathway through which hydrogen ions can travel from the cathode 18 to the anode 20 via ion current transfer.

M) The outer layer 34 of the IJ box assembly 22 has silicon carbide powder combined with PTFE particles to add hydrophilic properties and further ensure that layer 34 serves as a gas barrier. are doing. In contrast, the VC1 hydrophobic layer 28 is impregnated with p TF E on a fibrous L-shaped carbon substrate to create hydrophobic properties. The porosity of the hydrophobic layer 28 is characterized by large pores through which the gaseous reactants can freely circulate from the passages 26 to the catalyst 3o. Thus, the catalyst 3o is surrounded by a hydrophobic layer and a hydrophilic layer, the hydrophobic layer facing the gaseous reactants and the hydrophilic layer facing the electrolyte. There is.

The hydrophobic layer 28 within each electrode is impregnated with Teflon to prevent electrolyte from filling the electrode. This is important because such filling, if allowed, reduces the number of open pores through which gaseous reactants must be conveyed into the cell 10. The above is an advantageous feature.

A reduction in the number of effective pores results in a reduction in the capacity of the battery to produce electricity.

Hydrophobic layer 28 allows the gaseous reactants to contact catalyst 3o, while hydrophilic layer 34 allows the electrolyte to contact catalyst 30. Thereby, each electrochemical reaction can be performed at the catalyst 30 of the cathode 18 and at the catalyst 30 of the anode 20. The catalyst 30ir is preferably formed of a noble metal such as platinum, with other metals precipitated on the hydrophobic layer 34 for bonding and partial waterproofing purposes. . The same configuration can be used for each of electrodes 18 and 20. Hydrophobic layer 2
8. Both plates 24 and electrodes 18 and 20 are electrically conductive. Therefore, in the case of the anode 18, the electrons liberated by the electrochemical reaction are transferred from the cathode 30 to the fibrous fibers of the hydrophobic layer 28. and through each passage 2
The partition of the brute 24 separating the 6
It can be propagated inward.

In the series arrangement shown in the figure, electrons from the cathode of one cell are conducted directly to the anode of an adjacent cell to travel through the entire stack.

A typical stack termination contact 38 is shown attached to the plate 24 of the cathode 18 in a conventional manner. The contactor 3sh is connected to an external circuit 40 (shown in block diagram form) and is connected to a unilateral circuit 4.
The other end of '0 is connected to a similar contact (not shown) at the opposite end of the stack of fuel 1D7 ponds.

This allows the electrons to reach the negative end of the staff (the end of the anode)
A complete circuit can be made from the positive end of the stack (at the beginning of the anode) via an external circuit 40 (1). Thus, hydrogen can move into each cell via the electrolyte contained within the matrix assembly, traveling from the cathode of the cell through the cell to the anode of the cell.

In operation, hydrogen is admitted through manifold 12 to passageway 26 in the cathode 18 of each cell in the stack. Oxygen is admitted through the manifold 14 into the anode 200 passageways 26 within each of the cells of the stack. Capillary action brings the electrolyte into contact with catalyst 30 at each of electrodes 18 and 20. Hydrogen passes from channel 26 to hydrophobic layer 28
propagates to the catalyst 30 at the cathode 18 through the pores. Oxygen propagates from the J path 26 through the hydrophobic layer 28 to the catalyst 3 at the anode 20. This causes the hydrogen and electrolyte to be placed in contact with each other at the interface of the catalyst 30 at the cathode 18, and the oxygen and the electrolyte are placed in contact with each other at the interface of the catalyst 30 at the anode 20. It is at these locations in the battery that each of the electrochemical reactions that produce electricity occur.

According to a feature of the invention, the matrix assembly 24 is located within the central layer 32 in order to ensure that the hydrophilic outer layer 34 is always filled with the required amount of electrolyte. The electrolyte is continuously dispensed from a reservoir 50 containing the electrolyte. A reservoir 50 is located outside the cell and is connected to the intermediate layer 32 by any suitable supply means, such as by a tube 52 serving as an electrolyte conduction means. This arrangement allows electrolyte to be fed into the cell 10 from the reservoir 50 via the tube 52 and through the central layer 32 without any interference with the conduction of the reactant gases within the cell. The feeding means may extend into and across the central layer 32. The connection between the central layer 32 and the tubes 52 can be achieved with the aid of a socket (not shown) to prevent spillage of the electrolyte.

In other embodiments, the supply means may be made of the same or similar material to the central layer 32 extending from the reservoir to the central layer 32. In other embodiments, the supply means can be an extension of the central layer 32 itself that feeds from the battery to the reservoir or to a supply means connected to the reservoir. The height of the reservoir 50 can be adjusted to provide hydrostatic pressure on the electrolyte as it flows from the reservoir to the battery. Any suitable means can be used to externally replenish the battery with electrolyte when required. For example, when the central layer 32 extends from the cell and acts as a supply means, a scrubber or other suitable electrolyte handling means may direct the electrolyte onto the material of the layer 32 at Vl and into the cell. It can be used for four purposes.

The loss of electrolyte in the area between the electrodes occurs in battery i.

may occur during the operation of the battery, and if insufficient compensation may result in a reduction in the electrical output of the battery or burnout of the battery. Due to the use of the storage tank 5o, frequent disconnection of the battery stack is not necessary and the outer layer 3 of the battery
Maintaining the correct level of electrolyte in 4.

The central layer 32 is manufactured by Kureha Chemical Co., Ltd.
clustryCompan, 77 o, f Tok
It is preferably made of fibrous carbon vapor produced by J(L7)αn.

The paper contains cut carbon fibers made from pitch and phenolic carbonized residual carbon. The fine lineal fibers average approximately 3 mm in length and, when bonded together, can form a uniform thin web. The thickness of paper is approximately 0.003 to 0.
020 inches (approximately 0075 to 0.28 +hM+)
, preferably about 0.009 to 0.011 inches thick (
(approximately 0.23 to 0.28 may), and the thickness can be easily reduced by compression. The term ``large pore'' means approximately 50 to 300 microns in size, while ``small pore'' refers to approximately 1 to 1 micron in size.
I'm enjoying 00 Mifuronwo. During assembly of battery 10, the layers are approximately 30 to 3.4 s Olbs/1n2 (approximately 2 to 3.4
It is compressed into a sandwich-like shape under a pressure of Rg/Cpfi).

External layer 34 is Teflon bonded silicon carbide. Silicon carbide was prepared by inking a suspension of Teflon (Litetrafluoroethylene) and an ink vehicle of polyethylene oxide.
It can be mixed with le). This mixture is added to the catalytic side of the electrode and smoothed out by something like grade. This mixture is dried and sintered. An electrolyte is then added to the layer during assembly of the cell.

- The method described above makes it possible to create small pores of a desired range of sizes. Any suitable material can be used for layer 34]. For example, the material can be made from an inert, condensed, perfluorocarbon polymer in the form of a reticulated cellulose, and a free, concentrated acid electrolyte enters within said reticulated cell, in which case , the inorganic parts are zirconium, tantalum,
Tungsten, Chromium and U.S. Pat. No. 3.453.14
No. 9 describes a compound consisting of at least one oxide, sulfate and phosphate of niobium. This patent is incorporated herein by reference in its entirety.

Further details regarding the construction of each layer of cell 10 are known and may be found, by way of example, in the aforementioned U.S. Pat. It's all listed in the issue. Are these patents P T J? 1+ of cells utilizing porous materials with impregnation of E and coating of precious metal catalysts
% is listed for construction. The multi-porous nature of matrix assembly 22 maintains the movement of electrolyte and retains electrolyte saturation of outer layer 34 during operation of cell 10. While utilizing the large pores of the central layer 32 to distribute the
4 to both. Additionally, the presence of electrolyte in all three layers of matrix assembly 22 provides a necessary conduction path for the hydrogen ion reservoir of ionized hydrogen.

Thus, the matrix assembly 22 of the present invention, as such, allows the battery 10 to operate at all times while maintaining uniform distribution of the layer liquid therein. The matrix 1 [solid 22 also maintains a uniform distribution of the electrolyte/in conjunction with the reservoir 50 outside the chamber allows the normal operation of the cell IO H1r+). Although an electrolyte replenishment system external to the fuel cell may be used herein, it is understood that matrix assembly 22 need not be used in conjunction with such a system.

It should be understood that the dual embodiments of the present invention are for illustration purposes only, and that modifications thereof may occur to those skilled in the art. It is not intended to be considered limiting to such embodiments, but should be limited only by the scope of the appended claims.

[Brief explanation of drawings]

FIG. 1 shows a perspective view of a portion of a stack of fuel cells in the assembly of such a fuel cell, which portion includes a second cell partially shown in phantom.
The fuel cell is depicted in cross-section to identify its individual layers. 10...Fuel cell 12.14...Manifold 18...Cathode 20...Anode 22...Matrix assembly 24... ... Distribution plate 28 ... Hydrophobic layer 30 ... Catalyst 32 ... Central layer 34 ... Outer layer

Claims (1)

[Claims] 1. In a fuel cell having an electrode in which an electrochemical reaction is carried out between a fluid reactant and an electrolyte, the electrolyte supporting structure comprises (a) first and second permeable (b) the electrically insulating layers are arranged in a laminated manner, one of which is electrically insulating;
The first layer is located within the ion conduction path between the electrodes. J
! (C) the second layer has relatively small pores that draw the electrolyte from the first layer; A fuel ff1c cell characterized in that the second layer is positioned adjacent to the interaction of one of the electrodes for supplying an electrolyte for electrochemical reactions at one electrode. 2 The first layer prevents in-plane movement of the electrolyte.
ne traussporting) ratio 1lt
a storage tank having 5 large pores and further supporting an electrolyte outside the fuel cell; and a storage tank with the electrolyte between the first layer and the storage tank. 2. A fuel cell according to claim 1, further comprising means for communicating. 3. a third porous layer arranged in a stacked configuration having the first layer and the second layer, the third layer sucking the electrolyte from the first layer; The third layer has relatively small pores (-) compared to the pores in the first layer, and the third layer supplies an electrolyte for the electrochemical reaction at the second electrode. 4. The fuel cell of claim 2, wherein the fuel cell is positioned adjacent to the interaction surface of a second said electrode. 4. The fuel cell of claim 2, wherein said cell and said electrolyte in said reservoir are at the same pressure. 5. The fuel cell of claim 3, wherein each of said electrodes comprises a hydrophobic layer having pores sufficiently large for transport of said fluid reactants, said second layer and said third layer is hydrophilic, and the cell further includes a layer between one of the hydrophilic layers and one of the hydrophobic layers to facilitate an electrochemical reaction between one of the fluid reactants and the electrolyte. 1. a catalyst disposed along the surface of each of the electrodes;
F. The fuel cell according to claim 43*. 6. the electrolytic layer 71'g, the support structure comprising a third transparent layer arranged in a stacked manner with the first layer and the second layer; The third layer has relatively small pores compared to the pores in the first layer that sucks the electrolyte from the layer of the electrolyte. The second electrochemical reaction
2. A fuel cell according to claim 1, wherein a second reservoir for supplying the electrode is located adjacent to the interaction surface of the electrode. 7. The fuel cell according to claim 1, wherein the large pores are approximately 50 to 300 microns thick, and the narrow pores are approximately 1 to 10 microns thick. 8. Claim 1, wherein one of the reactants is gaseous hydrogen, a second of the reactants is gaseous oxygen, the catalyst includes a noble metal, and the electrolyte is an acid. The fuel cell described. 9. A fuel cell according to claim 1, wherein one or more of the layers are electrically insulating. 10. The fuel cell of claim 1, wherein said electrically insulating layer is formed of silicon carbide particles combined with polytetrafluoroethylene.