RU2692688C2 - Micro-planar solid oxide element (mpsoe), battery based on mpsoe (versions) - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention is related to the field of electric engineering, namely to designs of microplanar solid oxide fuel elements (MPSOE) and batteries based thereon. MPSOE has a membrane of thin-layer solid electrolyte with anode and cathode on opposite surfaces (active part) and series connection by current to battery through current collector (interconnect), applied on opposite ends of frames made of electrolytic or structural ceramics, wherein the frames arranged along the perimeter of the element provide mechanical strength and form the near-electrode gas spaces. Current flowing along the electrodes and their commutation is performed through current collectors located on opposite lateral edges of the frames. Frames can be made in the form of triangular, quadrangular, pentagonal, hexagonal, polygonal, round or oval shape. Battery with microplanar elements interconnected in series by current can be located on flat, oval or more complex surface of technical device, for example on surface of combustion chamber of aircraft engine or on surface of furnace making cement.EFFECT: higher specific power and reduced ohmic losses in fuel cell due to improved weight and size characteristics is technical result of invention.5 cl, 7 dwg

Description

Field of use

The invention relates to electrochemical devices (ECU), such as electrochemical current generators for fuel cells, oxygen pumps, electrolyzers, converters, etc. Devices based on solid oxide elements (SOE) - elements with solid oxide electrolyte. More precisely, to the design of the element and the battery of micro-planar TOE with thin-layer solid electrolyte and connection nodes (current paths, interconnects) of the TOE to the battery.

The level of technology

Known ECUs contain TOE, for example, solid electrolyte fuel cells, most often based on zirconium dioxide, which can have tubular, planar or block (monolithic) electrolyte structures with applied gas diffusion electrodes, an anode and a cathode. In this case, the design of the elements and the design of the battery itself are interrelated. In devices with separated gas spaces, whether it be the fuel and oxidation cavities in a fuel cell or the air and oxygen cavities of an oxygen pump, etc., the problem of separating gas spaces, in our opinion, is easier solved using a tubular element structure. In the planar construction, the separation of the near-electrode gas spaces is carried out by a bipolar plate, which performs the functions of organizing the gas flows of the reactants and the functions of the current passage (interconnect) for the electrical series connection of the elements in the battery. As a rule, the bipolar plate is made of metal, the element is ceramic, therefore their compatibility in the process of long-term operation is problematic and wants to be better. Often enough compaction occurs with the compressive force of the impregnated felt during operation and does not allow the desired number of heating-cooling cycles or the removal of this load. Recently, the use of Fe-Cr and Ni-Cr alloys, which, compared to electrically conductive ceramics, for example, lanthanum-strontium chromite, are more advanced, is being increasingly used as materials for current collectors and current passages in the construction of batteries. and have improved electrical and thermal properties, as well as an acceptable cost. In this application, to describe battery components that simultaneously perform the function of a current collector, a current collection and a current passage, we will use the term connection node (CS). In addition to traditional tubular and planar constructions of SOFC, developed in the last century, at present an already well-established term can be considered a micro-tubular structure in which the diameter of a single element is equal to or less than 5 mm. At the same time, it was shown in [1] that with a decrease in the diameter of such elements, the specific power — power per unit area of the electrode (s) increases. FIG. 1a shows the dependence of the power density (kW / l) on the diameter of micro-tubular SOFC for the specific power of 0.2 W / cm2 [1]. With a decrease in the diameter of micro-tubular SOFC, its consumer properties are improved: volumetric power (kW / l), specific mass power (kW / kg) and the speed of starting and cooling batteries in the minute interval, which allows expanding the application of power systems on SOFC to autonomous, mobile ( airborne). At the beginning of its development, in the last century, supporters of planar (flat) construction spoke not only about high packing density (specific volume capacity of kW / l), but also about the possibility of increasing the area of a single element to meter values. In this case, the removal of heat from the central part of the element along a thin-layer plate to the periphery did not pay enough attention, not considering this to be a problem. However, by the end of the century, most developers came to a limitation of the area of a single element of 1-2 dm2 or even to an area of 50x50 mm. The developers of Rolls-Royce Fuel Cell Systems (US) Inc. introduced the new term “Integrated Planar SOFC (IP-SOFC)” [2], i.e. “United planar SOFC” or in our understanding - “SOFC battery”. In our opinion, by analogy with the well-established term “micro-tubular” structure, such a structure should be called the “micro-planar” structure of the SOFC. FIG. 2 shows the appearance of three batteries of the company Rolls-Royce Fuel Cell Systems (US) Inc. (Fig. 2a – c) and a schematic depiction (Fig. 2d) of a series connection of the elements in them [2]. The batteries in FIG. 2a – c have the same overall dimensions and differ in the number of single elements N, the active area of the electrodes Sact. (% of total surface) and power generated under identical conditions P: (a) - N = 15, Sact. = 63%, P = 30 W; (b) - 30, 53%, 42 W; (c) - 60, 53%, 60 W. The dependence of the power density on the area of the electrode of these batteries with currents of 2.5 A (Fig. 2a), 1.75 A (Fig. 2b) and 1.25 A (Fig. 2b) at 0.8 V on a single element is shown in Fig . 1b. It is seen that the effect of increasing power density with decreasing electrode area, as well as for a tubular structure, occurs. The authors of the analogue naturally noticed that a decrease in the working area of a single element and a decrease in current lead to an increase in power density (kW / l; kW / kg), but unfortunately could not overcome the inertia of thinking by placing the battery cells on a plane - IP-SOFC), the authors could not get a greater packing density of the elements, as in the microtubular batteries of the cell.

Description of analogues

The authors consider, for example, a patent [3] to be one of the analogues of a SOFC battery made of tubular elements with a solid electrolyte carrier. The analogue used an element in the form of a solid electrolyte tube with uniformly applied gas diffusion electrodes and organized current collection and current transport through granular filling (for example, from electrode material) along the element with a terminal to the end portion of the tube with internal and external tubular metal current leads. At the same time, the internal current drain functioned as a gas inlet. The connection of the elements of the analog to the battery is carried out in parallel with the current and gas, as described by the authors in [4]. In this case, the serial connection of elements in the battery was not supposed to be attributed to the main disadvantage. The following disadvantage of the design of the analog is the use of a tubular element (test tube) with a thick wall and a large working area, which reduces the efficiency of the entire battery. Batteries from series-connected micro-tubular elements can also be considered analogous [1].

The analogs of the planar planar construction of the SOFC are quite fully described in monographs [5–7]. However, all of them have relatively low specific volumetric power of kW / l, specific mass power of kW / kg and are not suitable for use in automotive transport and aviation.

The closest analogue is the prototype of the elements, the battery of the elements and the nodes of the connection of the elements into the battery, the authors consider the design of the firm SolidPower [8], shown in FIG. 3. The developers of this company in order to increase the electrical efficiency, which reached 60–65%, went in stages to reducing the working area of the element from almost 2 dm2 to 1/4 dm2 (50x50 mm). At the same time, they improved the uniformity of the gas flow of fuel due to the complexity of the bipolar plate, which led to both a more uniform temperature distribution across 4 elements of 50x50 mm on one bipolar plate, and in the battery 1.5-2.0 kW in general. In fact, they fulfilled the principles of micro-tubular design, reduced the working surface of a single element, improving the uniform distribution of reactive gas flows and temperature. Ultimately, by equalizing the fluxes of reagents, they sought to reduce temperature gradients, improve heat dissipation, reduce current and electrical losses associated with ohmic (IRΩ) and polarization (IRη) overvoltages. The authors of the prototype achieved the goal and achieved experimentally high efficiency at low power of 1.5 kW. However, they could not increase the volumetric and mass specific power of the device as a whole (kW / l, kW / kg), and therefore could not move from stationary devices to more widespread use to mobile (on-board) energy or as it is called - small distributed energy , to power, devoid of large network losses. To improve (kW / l, kW / kg) most of all do not allow bipolar plates constituting more than 50% of the volume and 70% of the mass.

The goal, the technical task of the present invention is the design of the element and the battery, devoid of the above disadvantages of the prototype and analogues, allowing to obtain higher specific volume and mass density of power (kW / l, kW / kg).

The problem is solved by using a micro-planar solid oxide cell (TOE) and batteries based on such film micro-planar TOE (MP TOE). Thin-layer (thin-film) working part of the flat element is located between the frame of structural ceramics, which serves as a mechanical holder. The active part can be made with a carrier electrolyte with a thickness of up to 100–200 µm, with a carrier cathode, with a carrier anode, with carrier layers of an anodic or cathodic mixed conductor with a thin electrolyte layer, less than 5–10 µm. In this case, the electrolytic membrane can be made multi-layer, at least two-layer, with layers of solid electrolyte material of different composition or material with mixed electronic and ionic conductivity. The formation of a multilayer electrolyte allows us to solve several problems: the expansion of the electrolytic use of such an electrolyte, the formation of an electrolyte membrane with the optimal combination of its conductivity and mechanical strength, as well as improving the compatibility of the electrolyte with electrodes, etc.

The shape of the element of the active part and the frame can be in the form of a triangular, rectangular polygonal plate, circle, oval, etc. Conductivity and sequential switching of electrodes of adjacent elements into a battery is carried out by local layers of the current collector (interconnect) or wire (flat) grids applied to the electrodes of the active part of adjacent elements, flat surfaces and lateral faces of the frames of adjacent adjacent elements. An improved micro-planar element of the claimed design is shown in FIG. 4. In the active part, it has a carrier solid oxide electrolyte, membrane 1, generally containing two or more layers differing in conductivity type, electrodes are applied on opposite surfaces of membrane 1: anode 2 and cathode 3. The function of the carrier component of SOFC with the necessary mechanical strength, in the known technical solutions impose on a solid electrolyte, anode, cathode, current collector, etc., or several components simultaneously perform this role together. In the design declared by us, this function is performed by one or two frames 4, located along the perimeter of the active part from compatible structural ceramics or from the material of the same electrolyte. As described above, the thin-layer, active (functional, working) part of the element, bordered by the frame (s) giving (them) the required mechanical strength to the element, can have any shape shown in FIG. 5. At the same time, the functions of mechanical strength and the formation of near-electrode gas spaces of the micro-planar element, provided with one or two frames, imply the absence of additional details: plates with holes that separate the gas reactants and the series connection of adjacent elements in bipolar plates. At the same time, small working surfaces of the elements, reducing currents, make the losses when switching elements along the electrodes acceptable. Therefore, the electrodes of adjacent elements are connected in current through current collectors (interconnects) located at opposite ends of the framework.

FIG. 6 depicts a battery MP TOE from a thin-layer active zone (pos. 1-3), bounded by hexagonal frames 4, which are assembled (connected by current) on a flat, oval or more complex surface of a technical device. FIG. 6 shows the principle of a series of electrical connections MP TOE and washing the working surfaces of the battery with fuel and oxidizer. For example, the battery MP TOE may be located on the surface of the combustion chamber of the fuel in an aircraft engine, operating at operating temperatures and providing a supply of fuel and oxidizer. Batteries MP TOE can be located inside the cement kilns at high temperature and ensure the gas flow of reagents.

FIG. 7 shows a battery of micro-planar solid oxide cells (MP TOE) from a thin-layer active zone bounded by hexagonal frames, which is collected (connected by current) along the normal axis of symmetry of the planar elements. At the same time, adjacent elements of the battery are collected by active surfaces of the same name (electrodes) to each other. Such an arrangement of the elements makes it possible to exclude complex separating gas partitions (bipolar plates) for the formation of gas flows of fuel (H2) and oxidant (O2, air) and to ensure the consistent connection of the elements along the current. The arrangement (connection) of micro-planar elements in the battery we declare leads to the formation of joint, alternating anodic and cathodic gas cavities with inlet and outlet gas channels, and an electrical series-connected current connection is performed on the side edges of the frames.

The patented design of micro-planar elements (MP TOE) and batteries assembled on the surface of technical devices, or autonomously along the normal axis of symmetry, allows the manufacture of various solid oxide devices: electrochemical solid-state fuel cell (TFC) electricity generators; solid oxide electrolysis cells for producing hydrogen and oxygen, for example, water decomposition (SOE); solid oxide oxygen pumps for the production of highly pure oxygen from air (TOCN): solid oxide converters (TSC) and other possible devices.

The presented design options for the MP EOC and batteries based on the MP EFC are explained in the drawings in FIG. 4-7, where in FIG. 4 shows a schematic depiction of the cross section of the MP EOC in accordance with the present invention (in the figure is a local section): 1 — a thin membrane of a supporting solid oxide electrolyte, 2 — an anode, 3 — a cathode, 4 — a frame, 5 — current passage (interconnect); in FIG. 5 schematically shows the possible forms of MP TOE and their connection into a flat battery; in FIG. 6 schematically shows the principle of series electrical connection of the MP EFC in a flat battery and washing of the working surfaces of the battery elements with fuel and oxidizer: 1 - a thin membrane of a solid oxide electrolyte, 2 - an anode, 3 - a cathode, 4 - a frame, 5 - a current passage (interconnect); in FIG. 7 shows a schematic depiction of a block-type battery MP TOE, in which the elements are interconnected sequentially in current and arranged along the normal axis of symmetry of the active surfaces of the same name (electrodes) to each other with the formation of joint, alternating anode and cathode gas cavities (the channels in the figure are not shown): 2 — anode, 3 — cathode, 4 — frame, 5 — current passage (interconnect).

List of references:

1. K. Kendall. Progress in Microtubular Solid Oxide Fuel Cells // Int. J. Appl. Ceram. Technol., V. 7, 2010, p. 1–9.

2. Ted Ohrn. Rolls Royce IP-SOFC Technology Development // NETL.DOE.GOV: Proceedings of the 10th Annual Solid State Energy Conversion Alliance (SECA) Workshop, July 14-16, 2009, Pittsburgh, PA.

URL: https: //www.netl.doe.gov/file%20library/events/2009/seca/presentations/Ohrn_Presentation.pdf (access date: 03/03/2017).

3. Cell of a high-temperature element of a solid electrolyte electrochemical device: Pat. 2178560 Ros. Federation: MPK7 G 01 N 27/406 / Vostrotin V.A., Grechko M.V., Zakutnev A.D., Krylova O.E., Kulaev V.V., Lukashenko I.G., Ustyugov A.V. ., Chukharev V.F., Applicant and patent holder of RFNC - VNIITF, Ministry of the Russian Federation for Atomic Energy. - 98117353/28; Appl .: 17.09.1998; publ .: 27.06.2000, Bull. No. 18.

4. Solid oxide fuel cells: Collection of scientific and technical articles. - Snezhinsk: RFNC – VNIITF Publishers, 2003. - P. 340-364.

5. High temperature solid oxide fuel cells: fundamentals, design and applications // Edited by S.C. Singhal, K. Kendall, Elsevier Ltd.– 2003.– 405 p.

6. High-temperature electrolysis of gases / M.V. Perfilyev, A.K. Demin, B.L. Kuzin, A.S. Lipilin. - M .: Science, 1988. - 232 c.

7. Science and Technology of Ceramic Fuel Cells / Edited by N.Q. Minh, T. Takahasi. - Amsterdam: Elsevier Science B.V., 1995. - 366 p.

8. SolidPower BlueGEN // BLUEGEN.DE: Brochure. 2014. URL: http://www.solidpower.com/wp-content/uploads/2014/02/SOLIDpower_BlueGEN_UK_web.pdf (access date: 03/23/2017).

Claims (5)

1. A microplanar solid oxide cell (MP TOE) containing a thin-layer solid electrolyte membrane with an anode and a cathode on opposite surfaces (active part), designed for series connection of current into the battery, through a current collector (interconnect), which is not a bipolar plate, distinguished by that the functions of its mechanical strength and the formation of near-electrode gas spaces provide one or two frames of electrolytic or structural ceramics, connected to the active part and located along its perimeter, while the electrodes are connected to current collectors (interconnects) deposited on opposite ends of the framework. 2. Microplanar solid oxide cell (MP SOE) according to claim 1, characterized in that the electrolyte membrane contains two or more layers differing in the type of conductivity. 3. Micro-planar solid oxide element (MP TOE) according to claim 1, characterized in that the frames are made of electrolyte or structural ceramics, placed along the perimeter of the active (working) part of the element and have a triangular, quadrangular, pentagonal, hexagonal, polygonal, round, oval form with current collectors on opposite ends. 4. Battery based on MP TOE, characterized in that the microplanar elements in it are interconnected sequentially in current and are located on a flat, oval or more complex surface of a technical device operating at operating temperatures and providing fuel and oxidizer supply. 5. Battery based on MP TOE, characterized in that the microplanar elements in it are interconnected sequentially in current and are located along the normal axis of symmetry of the active surfaces of the same name (electrodes) to each other with the formation of joint, alternating anodic and cathodic gas cavities with input and output gas channels without the use of dividing gas partitions - bipolar plates, and an electrical series connection for current is carried out by current passages located along the opposite side nym side faces of the framework.

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