WO2009116102A1 - Dispositif électrochimique - Google Patents

Dispositif électrochimique Download PDF

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Publication number
WO2009116102A1
WO2009116102A1 PCT/IT2008/000191 IT2008000191W WO2009116102A1 WO 2009116102 A1 WO2009116102 A1 WO 2009116102A1 IT 2008000191 W IT2008000191 W IT 2008000191W WO 2009116102 A1 WO2009116102 A1 WO 2009116102A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrolyte
electrodes
fuel
oxidizer
electro
Prior art date
Application number
PCT/IT2008/000191
Other languages
English (en)
Inventor
Angelo D'anzi
Original Assignee
Exergy Fuel Cells S.R.L.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Exergy Fuel Cells S.R.L. filed Critical Exergy Fuel Cells S.R.L.
Priority to PCT/IT2008/000191 priority Critical patent/WO2009116102A1/fr
Publication of WO2009116102A1 publication Critical patent/WO2009116102A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/08—Fuel cells with aqueous electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1065—Polymeric electrolyte materials characterised by the form, e.g. perforated or wave-shaped
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • H01M2300/0005—Acid electrolytes
    • H01M2300/0011—Sulfuric acid-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0094—Composites in the form of layered products, e.g. coatings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to an electro-chemical device which can be defined more appropriately as a particular embodiment of a fuel cell or of an electrolyzer.
  • Electrolyzers are devices which allow the electric power applied to the device to be converted into chemical energy contained in a fuel and an oxidizer.
  • the most common devices are those in which the flow of electric current generates the electrolysis of water to form hydrogen and oxygen in the gaseous phase.
  • the water, anode side is reduced in such catalytic interface regions with the addition of electric power from an external circuit, the generated protons pass through the electrolyte and oxidize into gaseous hydrogen on the cathode side, while gaseous oxygen is generated on the anode side.
  • the fuel cell is an electro-chemical device in which, in principle, the chemical energy contained in a fuel and an oxidizer is converted into electric power: a fuel (typically hydrogen or other fuels which include it among their components) and an oxidizer (oxygen or air) enter the cell and DC electric current, water and heat are obtained from them.
  • a fuel cell is similar to batteries and therefore, like other voltaic elements, it is formed substantially by two electrodes, the cathode and the anode, and an electrolyte which allows ion migration. Differently from ordinary batteries, in the fuel cell the active material is renewed continuously and therefore the DC electric current can be delivered indefinitely if the supply of fuel and oxidizing gases is maintained.
  • the interface regions between the electrodes and the electrolyte are provided with at least one layer of catalytic material, which allows the oxidizer reduction reactions (cathode side) and fuel oxidation reactions (anode side) to occur with the desired ratio.
  • the electrolyte is intended to conduct the ions produced proximate to one of the electrodes and used proximate to the other electrode. Such ion passage is accompanied by a passage of electrons from the anode to the cathode through an external circuit.
  • Each individual cell thus composed is coupled in electrical series to the next one by interposing a layer of electrically conducting material, which normally acts also as a flow field for the reagents.
  • the electro-chemical transformation is accompanied by the generation of heat, which has to be extracted in order to keep the operating temperature of the cell within values which allow its regular operation.
  • the cell substantially has a three-layer structure, in which the central layer, comprised between the cathode and the anode, constitutes or contains the electrolyte.
  • the facing surfaces must have an area which is sufficient to achieve current intensities which are adequate for the requirements of the application. It is thus possible to reach, depending on the application and the arrangement of cells, surfaces of even more than one square meter.
  • the individual cells characterized by voltages comprised between one half of a volt and one volt, depending on the technology used, on the operating conditions and on the electrical load applied to it) are mutually superimposed, connecting them in series so as to obtain a total T/IT2008/000J91
  • a fuel cell plant is composed not only by the power module
  • the present invention relates in particular to electro-chemical devices in which there is a proton exchange electrolyte.
  • PAFC Polymer Electrolyte
  • PEFC Fuel Cell
  • the former are characterized by the use of a liquid solution of phosphoric acid as an electrolyte. They have demonstrated satisfactory performance and life, but the need to use huge quantities of catalyst on the electrodes and the difficulty in managing an acid electrolyte in the liquid phase do not allow a reduction of production costs which is sufficient for their large-scale diffusion.
  • the latter are electro-chemical devices with a solid electrolyte which, in order to achieve an adequate ion conductivity within the electrolyte, require such electrolyte to be humidified.
  • This humidification is currently performed by introducing steam in the reagents that enter the device.
  • the devices most commonly used for this purpose are polymer membrane systems (for example Perma Pure LLC FC series) or enthalpy wheels (for example HumidicoreTM).
  • a polymeric membrane which has characteristics of molecular permeability for water, allows to transfer water molecules from a stream of gas with high humidity (for example the cathode stream in output from the stack) or from a stream of liquid water to the streams of reagent gases in input to the stack.
  • a rotary device allows the transfer of the water between such streams.
  • the resulting humidification is not uniform but is tightly linked to the path of the reagent gases in their field of flow adjacent to the surface of the exchange membrane.
  • the circulation of electric current can be attributed to the conductive bridge constituted by the electrolyte, which by striking the contiguous surfaces of the adjacent plates arranges them in electrical continuity: such electrical continuity entails energy losses due to the value of the electrical resistance observed by such current in passing between one plate and the contiguous one.
  • the negative consequence of these losses can be observed by checking the total value of the efficiency of the individual cell or of an electro-chemical device constituted by a plurality of elementary cells: the efficiency value in fact cannot exceed limit values which are due to the impossibility to eliminate this kind of losses. Disclosure of the Invention The aim of the present invention is to obviate the above-mentioned drawbacks and meet the mentioned requirements, by providing a high- efficiency electro-chemical device in which the currents that circulate between contiguous plates are substantially negligible.
  • an object of the present invention is to provide an electro-chemical device which allows optimum electrical contact of the electrodes with the electrolyte.
  • Another object of the present invention is to provide an electrochemical device which is simple, relatively easy to provide in practice, safe in use, effective in operation and has a relatively low cost.
  • the present electro-chemical device of the type that comprises at least one pair of mutually facing electrodes, between which an electrolyte is interposed, said electrodes being porous and being respectively struck by a fuel and by an oxidizer which arrive from respective supply circuits, said electrolyte having a substantially laminar structure and comprising at least two laminas of electrolyte in the solid state, between which at least one additional layer of liquid electrolyte is interposed within an interspace, characterized in that outside said electrodes there are respective bipolar plates made of conducting material and in that said laminas of solid electrolyte have a separation layer made of electrically insulating material, whose ends are thicker and are suitably shaped so as to delimit respective lateral channels for feeding and removing the liquid electrolyte within each individual elementary cell
  • Figure 1 is a schematic sectional side view, taken along a longitudinal plane, of an electro-chemical device according to the invention
  • Figure 2 is a schematic sectional side view, taken along a longitudinal plane, of the elementary cell of an electrochemical device according to the invention
  • Figure 3 is a front view of a separation layer of an electro-chemical device according to the invention
  • Figure 4 is a front view of a pole plate of an electro-chemical device according to the invention.
  • Figure 5 is a sectional view, taken along the line V-V of Figure 3. Ways of carrying out the Invention
  • the reference numeral 1 generally designates an electro-chemical device.
  • the electro-chemical device 1 comprises at least one pair of electrodes, an anode 2 and a cathode 3, which are substantially flat and face each other and between which an electrolyte is interposed.
  • the electrodes 2 and 3 are porous and are struck respectively by a fuel and by an oxidizer, which arrive from respective supply circuits (channels 4 for the fuel and channels 5 for the oxidizer).
  • the electrolyte has a substantially laminar structure and comprises two laminas of electrolyte in the solid state 6 (generally of the polymeric type), between which, within an interspace 7, there is at least one interposed layer of electrolyte in the liquid state 8 (generally an aqueous solution of sulphuric acid).
  • the electrolyte in the liquid state 8 is contained within a forced circulation circuit which also comprises the interspace 7.
  • the interspace 7 accommodates a support made of sponge-like material which is deformable in a' substantially elastic manner and is adapted for impregnation with the liquid electrolyte 8 and for its circulation inside it.
  • the deformability of the sponge-like material entails the advantage of ensuring perfect adhesion, by expansion of the interspace 7, of the laminas of the solid electrolyte 6 to the electrodes 2 and 3.
  • An elementary electro-chemical cell 13 has two layers of solid electrolyte 6 of the polymeric type, on each of which a porous electrode, anode 2 and cathode 3, is applied externally; the electrodes 2 and 3 are both provided with a catalyst at an interface 15.
  • An aqueous solution of liquid electrolyte 8 circulates between the two layers of solid electrolyte 6 and is managed by a closed circuit which is constituted, merely by way of example in a preferred embodiment, by ducts 12 and controls its concentration by way of suitable sensors (and by means of an apparatus for replenishing demineralized water within the liquid electrolyte 8, the demineralized water being taken through a condenser directly from the cathode discharge and stored within a suitable tank) and removes the heat generated by the electro-chemical reactions by means of a heat exchanger if necessary.
  • a suitable separation layer 10 allows the liquid electrolyte 8 to flow within the interspace 7 between the two polymeric membranes that constitute the solid electrolyte 6.
  • the laminas of the solid electrolyte 6 have a respective separation layer 10, which is made of electrically insulating material (a dielectric material which has suitable chemical and physical properties so that it is not damaged by the reactions that occur at the electrodes 2 and 3).
  • the separation layer 10 has ends 11 which are thicker and suitably shaped so as to delimit the lateral channels 12 to feed and remove the liquid electrolyte 8 within each individual elementary cell 13.
  • the thicker ends 11 have a thickness which is substantially equal to the entire thickness of an elementary cell 13, in order to avoid the possibility that the electrolyte 8 might come into contact with the pole plate 9, constituting an electric bridge through which circulation of an electrical current would be possible.
  • Such electrical current would entail a sharp decrease in the efficiency of the elementary cell 13 and therefore of the entire device 1: correct insulation is therefore essential for providing the device 1 according to the invention.
  • the lateral edge 14 of each individual end 11 of an elementary cell 13 abuts against a corresponding end edge 14 of a contiguous elementary cell 13: this constructive architecture ensures that the channels 12 are correctly delimited by the ends 11 in order to prevent the inflow of the (conducting) electrolyte 8 onto the plates 9, consequently establishing electrical leakage currents.
  • the pair of pole plates 9 arranged inside the device 1 allows to feed the reagents 4 (hydrogen or mixture of gases containing hydrogen) and 5 (oxygen or air) to the electrodes 2 and 3 and the series electrical connection between one cell 13 and the next.
  • the pole plates 9 of the terminal type connect the stack of fuel cells 13 to the electrical load by means of a circuit 16.
  • Humidification is perfectly uniform and practically independent of the operating conditions (temperatures, flow-rates of the reagents, ratios of reaction inside the device), differently from what occurs in traditional devices with polymeric electrolyte.
  • the regions of greatest heat generation are in close thermal contact with the aqueous solution 8, which prevents local temperature peaks even with high reaction ratios.
  • the separation layer 10 has the additional function of a gasket for the seals of the electrolyte 8 and of the reagents 4 and 5.
  • the separator 10 is made of a material which allows, by deforming as a consequence of the fastening step, a perfect seal: the lateral edges 14 abut against each other with compression and mutual deformation, ensuring a seal, since they behave as true gaskets.
  • the electrolyte 8 that is used is, according to a particular embodiment cited by way of example, an aqueous solution of sulphuric acid (H 2 SO 4 ) at 20% by weight.
  • This configuration allows to create a curtain of electrolyte 8 which is as thin as desired by varying the thickness of the separation layer 10 and/or the thickness of the membranes of the solid electrolyte 6 and of the porous electrodes 2 and 3.
  • the electrodes 2 and 3 both have thicknesses of substantially 0.3 mm
  • the membrane of the solid electrolyte 6 has a thickness of 0.035 mm
  • the separator 10 has a thickness of 0.8 mm
  • the curtain of electrolyte 8 has a thickness of 0.13 mm.
  • the individual cell 13 has been fed with dry air and hydrogen.
  • the considerable increase in efficiency of the cells 13 constituted according to the constructive architecture proposed by the present invention can be attributed to the elimination of the leakage currents that arise within the liquid electrolyte 8 in known types of device and provide an electrical connection between the pole plates 9 at a different potential.
  • the electrical insulation of the channels 12 with respect to the plates 9 ensured by the shape of the layers 10 (and in particular of their ends 11) is such as to prevent the circulation of leakage currents.
  • the identified conceptual configuration allows to design the electro-chemical cells 13 so that the curtain of liquid electrolyte 8 that is present is thin as desired (even less than 0.1 mm).
  • optimum electrical contact between the electrodes 2 and 3 and the pole plates 9 can be ensured by the presence of the support made of sponge-like material which is accommodated within the interspace 7, which can be compressed between the electrodes 2 and 3, thus forcing an optimum contact with them.
  • the presence of the electrolyte in the liquid phase 8 and of the two solid membranes 6 allows to obtain, in the same operating conditions, better performance than that observed for a polymer electrolyte cell which operates with a single membrane having identical characteristics.
  • the device 1 allows to obtain systems whose volumes and weights are comparable to those having an equal performance which can be obtained with single-membrane technology, adapted for both static applications and automotive applications.
  • the devices 1 based on this invention allow to have high power densities both per unit weight and per unit volume.
  • the concentration of the aqueous solution of electrolyte 8 can be controlled easily.
  • the cathode flow-rate can be changed over a very wide range depending on the requirements of the individual application without compromising correct operation. It has thus been shown that the invention achieves the proposed aim and objects.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Fuel Cell (AREA)

Abstract

La présente invention concerne un dispositif électrochimique (1) comprenant au moins une paire d'électrodes mutuellement opposées (2, 3) entre lesquelles est intercalée un électrolyte. Les électrodes (2, 3) sont poreuses et sont respectivement atteintes par un combustible (4) et un agent oxydant (5) qui arrivent par l'intermédiaire de circuits d'alimentation respectifs. L'électrolyte présente une structure sensiblement feuilletée et comporte au moins deux feuillets d'électrolyte dans l'état solide (6) entre lesquels au moins une couche additionnelle d'électrolyte liquide (8) est intercalée dans un espace intermédiaire (7). À l'extérieur des électrodes (2, 3) des plaques bipolaires respectives (9) en matériau conducteur sont disposées et les feuillets d'électrolyte solide (6) comportent une couche de séparation (10) en matériau isolant du point de vue électrique, dont les extrémités (11) sont plus épaisses et sont façonnées de manière appropriée pour délimiter des passages latéraux respectifs (12) servant à apporter l'électrolyte liquide (8) dans chaque cellule élémentaire individuelle (13) et à l'en faire sortir.
PCT/IT2008/000191 2008-03-21 2008-03-21 Dispositif électrochimique WO2009116102A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/IT2008/000191 WO2009116102A1 (fr) 2008-03-21 2008-03-21 Dispositif électrochimique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT2008/000191 WO2009116102A1 (fr) 2008-03-21 2008-03-21 Dispositif électrochimique

Publications (1)

Publication Number Publication Date
WO2009116102A1 true WO2009116102A1 (fr) 2009-09-24

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013028911A1 (fr) * 2011-08-25 2013-02-28 The Board Of Trustees Of The Leland Stanford Junior University Catalyse contrôlée par des champs électriques interfaciaux

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3856573A (en) * 1969-07-01 1974-12-24 Siemens Ag Method of producing a structural member formed of electrodes, cover layers and a support frame for fuel elements with a liquid electrolyte, and structural member produced by the method
WO2002071524A1 (fr) * 2001-03-02 2002-09-12 Pylkkaenen Thomas Empilement de cellules electrochimiques
WO2003019706A2 (fr) * 2001-08-22 2003-03-06 Reinz-Dichtungs-Gmbh & Co. Kg Pile a combustible a membrane
US20050260473A1 (en) * 2004-05-21 2005-11-24 Sarnoff Corporation Electrical power source designs and components
EP1646099A2 (fr) * 2004-09-28 2006-04-12 Arcotronics Fuel Cells S.r.l. Dispositif électrochimique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3856573A (en) * 1969-07-01 1974-12-24 Siemens Ag Method of producing a structural member formed of electrodes, cover layers and a support frame for fuel elements with a liquid electrolyte, and structural member produced by the method
WO2002071524A1 (fr) * 2001-03-02 2002-09-12 Pylkkaenen Thomas Empilement de cellules electrochimiques
WO2003019706A2 (fr) * 2001-08-22 2003-03-06 Reinz-Dichtungs-Gmbh & Co. Kg Pile a combustible a membrane
US20050260473A1 (en) * 2004-05-21 2005-11-24 Sarnoff Corporation Electrical power source designs and components
EP1646099A2 (fr) * 2004-09-28 2006-04-12 Arcotronics Fuel Cells S.r.l. Dispositif électrochimique

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013028911A1 (fr) * 2011-08-25 2013-02-28 The Board Of Trustees Of The Leland Stanford Junior University Catalyse contrôlée par des champs électriques interfaciaux

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