Abstract: In an electrochemical cell of the type having a solid ceramic electrolyte between its anode and cathode, the electrolyte is dome-shaped, in the form of a thin curved shell of ceramic material such as a beta alumina. The domed configuration of the electrolyte reduces the weight that is required to withstand internal pressure differential generated across the electrolyte in discharge, and also reduces internal resistance of the cell.

Abstract: Durable thin film ion conducting coatings are formed on a transparent glass substrate by the controlled deposition of the mixed oxides of lithium:tantalum or lithium:niobium. The coatings provide durable ion transport sources for thin film solid state storage batteries and electrochromic energy conservation devices.

Abstract: An electrode having higher power output is formed of an open mesh current collector such as expanded nickel covering an electrode film applied to a tube of beta-alumina solid electrolyte (BASE). A plurality of cross-members such as spaced, parallel loops of molybdenum metal wire surround the BASE tube. The loops are electrically connected by a bus wire. As the AMTEC cell is heated, the grid of expanded nickel expands more than the BASE tube and the surrounding loop of wire and become diffusion welded to the electrode film and to the wire loops.

Abstract: A liquid metal thermal electric converter which converts heat energy to electrical energy. The design of the liquid metal thermal electric converter incorporates a unique configuration which directs the metal fluid pressure to the outside of the tube which results in the structural loads in the tube to be compressive. A liquid metal thermal electric converter refluxing boiler with series connection of tubes and a multiple cell liquid metal thermal electric converter are also provided.

Abstract: An alkali metal heat engine. A thermoelectric generator which circulates alkali metal through a cationic barrier to produce electricity. The device is capable of operating in a reduced gravity or gravity-free environment and without mechanical pumps because it collects and recirculates the liquid alkali metal with capillary wick structures. One capillary wick moves the alkali metal from the cooler side of the barrier to the hotter side, and another wick is used as a bypass structure to recirculate the undiffused alkali metal back to the heat source.

Abstract: An electrochemical storage cell based on sodium and sulphur includes a metallic housing. A solid electrolyte disposed in the housing defines an anode space and a cathode space mutually separated by the solid electrolyte and outwardly bounded by the housing. A felt is disposed in the cathode space to form an electrode. The felt is impregnated with sulphur and folded at least twice. The felt has graphite or carbon fibers disposed substantially perpendicular to the longitudinal axis of the storage cell and substantially perpendicular to the surface of the solid electrolyte.

Abstract: The invention is directed to a composite article suitable for use in thermoelectric generators. The article comprises a thin film comprising molybdenum oxide as an electrode deposited by physical deposition techniques onto solid electrolyte. The invention is also directed to the method of making same.

Abstract: An electrode having higher power output is formed of a thin, porous film (less than 1 micrometer) applied to a beta-alumina solid electrolyte (BASE). The electrode includes an open grid, current collector such as a series of thin, parallel, grid lines applied to the thin film and a plurality of cross-members such as loop of metal wire surrounding the BASE tube. The loops are electrically connected by a bus wire. The overall impedance of the electrode considering both the contributions from the bulk BASE and the porous electrode BASE interface is low, about 0.5 OHM/cm.sup.2 and power densities of over 0.3 watt/cm.sup.2 for extended periods.

Abstract: An novel metal-sulfur type cell operable at a temperature of 200.degree. C. or less with an energy density of 150 Whrs/Kg or better is disclosed characterized by an organo-sulfur cathode formed from an organic-sulfur compound having the general formula, in its charged state, of (R(S).sub.y).sub.n wherein y=1 to 6; n=2 to 20; and R is one or more different aliphatic or aromatic organic moieties having 1 to 20 carbon atoms, which may include one or more oxygen, sulfur, or nitrogen heteroatoms when R comprisises one of more aromatic rings, or one or more oxygen, sulfur, nitrogen, or fluorine atoms associtated with the chain when R comprises an aliphatic chain, wherein the aliphatic group may be linear or branched, saturated or unsaturated, and wherein either the aliphatic chain or the aromatic ring may have substituted groups thereon.

Abstract: Electrical energy is generated by feeding oxygen through a solid electrolyte wall in contact with a bath of molten metal, the positive electrode being provided on the surface of this wall defining the gas space while the negative electrode is provided in the melt. Carbon monoxide released when the oxygen reacts with dissolved carbon in the melt is collected for further use and the carbon in the melt is replenished in the form of solid carbon particles which can be entrained into the melt in carbon monoxide gas.

Abstract: An electrode having increased output with slower degradation is formed of a film applied to a beta-alumina solid electrolyte (BASE). The film comprises a refractory first metal M.sup.1 such as a platinum group metal, suitably platinum or rhodium, capable of forming a liquid or a strong surface adsorption phase with sodium at the operating temperature of an alkali metal thermoelectric converter (AMTEC) and a second refractory metal insoluble in sodium or the NaM.sup.1 liquid phase such as a Group IVB, VB or VIB metal, suitably tungsten, molybdenum, tantalum or niobium. The liquid phase or surface film provides fast transport through the electrode while the insoluble refractory metal provides a structural matrix for the electrode during operation. A trilayer structure that is stable and not subject to deadhesion comprises a first, thin layer of tungsten, an intermediate co-deposited layer of tungsten-platinum and a thin surface layer of platinum.

Abstract: A high-temperature storage battery includes a housing and a stack of at least two storage cells disposed in the housing. Each of the storage cells has components loosely disposed on top of one another in the stack. The components include two reactant chambers, a planar ion-conducting solid electrolyte mutually separating the reactant chambers, and planar components serving as electrodes and bordering the storage cells toward the outside. At least one common resilient structural element presses the components of all of the storage cells together in a leakproof manner.

Abstract: The invention provides a method of preparing a surface of a ceramic solid electrolyte conductor of alkali metal ions for wetting by said alkali metal in molten form. The method comprises doping the ceramic surface with an oxide of a transition metal. Transition metals such as Fe, Ni, Cu, Mn, Co, Cr or Mo have suitable oxides for doping beta-alumina for wetting by sodium.

Abstract: The invention provides a method of protecting an electrochemical cell which has a molten sodium anode, a chloride-ion containing sodium aluminum halide molten salt electrolyte, an iron-containing cathode in contact with the electrolyte and a solid conductor of sodium ions which separates the anode from the electrolyte, from the adverse effects of overcharging. The method comprises operating the cell, to prevent oxidation of iron to FeCl.sub.3 in the cathode, by connecting it in parallel with a protective cell having an open circuit charging plateau at a voltage less than the open circuit voltage of the Fe/FeCl.sub.3 //Na plateau of the cell being protected, and greater than the open circuit voltage, in its fully charged state, of the cell being protected. The invention also provides a cell of this type protected in this fashion, a battery including one or more such protected cells, and a cathode for such cells.

Abstract: The present invention relates to a sodium-sulfur electric cell structure having a specific joint between a cathode tube and an anode tube. The cathode and anode tubes are each made of an iron-nickel base alloy and are joined to each other through the medium of a ceramic ring and an aluminum alloy insert provided on both sides of the ceramic ring. A chromium or chromium-rich layer is formed at the joint boundary between the insert and each tube. The sodium-sulfur electric cell having such a structure eliminates a problem of the occurrence of cracking, improves the airtightness and enables the production of large-sized electric cells.

Abstract: The invention provides a rechargeable electrochemical cell comprising a cell housing 10 divided by a separator 20 into a pair of electrode compartments, one of which contains an anode substance and the other of which contains an active cathode substance and an electrolyte. The anode and electrolyte are liquid at the operating temperature of the cell and the electrode compartments are each divided into a gas chamber communicating with an electrode chamber. The gas chamber contains an inert gas under pressure and the electrode chamber contains a liquid, namely the anode material or the liquid electrolyte. A wall of each electrode chamber is provided by the separator and each electrode chamber has a closeable bleed outlet 74, 80.

Abstract: The invention provides a method of manufacturing an electrochemical cell housing wherein a beta-alumina tube has an open end attached to a casing via an alpha-alumina ring. In the method the alpha-alumina ring is thermocompression bonded to a metal ring by hot isostatic pressing, the alpha-alumina ring is then glass welded to the open end of the tube, and the metal ring is metal welded to the casing. The invention also provides a cell housing wherein a beta-alumina tube is located in spaced relationship within a metal casing. The tube is glass welded to an alpha-alumina ring which is thermocompression bonded on a curved radially facing surface thereof to a metal ring, the metal ring being metal welded to the casing.

Abstract: An electrochemical storage cell based on sodium and sulfur having an anode space and a cathode space, which are separated from one another by an alkali-ion-conducting solid electrolyte and defined at least partially by a metal housing. The metal housing is provided at least on its inner surface with an anti-corrosion film that as its essential components contains iron and chromium and at least one of (a) nickel and (b) cobalt. The anti-corrosion film is formed by an alloy the nickel or cobalt equivalent of which is less than its chromium equivalent.

Abstract: Electrochemical storage cell based on sodium and sulfur with an anode space and a cathode space which are separated from each other by a solid electrolyte and are bounded at least in some places by a metallic housing, and a sulfur electrode formed of a fiber-like material impregnated with sulfur arranged within the cathode space. An auxiliary substance which decomposes during charging of the cell to produce ternary sodium sulfide is arranged in the cathode space at least in the boundary regions between the solid electrolyte and the sulfur electrode.

Abstract: This invention relates to a method for improving the chargeability of sodium-sulfur cells by including in the cathodic reaction of the cell a device which provides a continuous release of additive into the sodium polysulfide/sulfur cathodic reactant. This method also reduces the corrosion of corrodible metal current collectors which may be employed in contact with the cathodic reactant therein.

Abstract: An electrochemical storage cell based on sodium and sulfur having an anode space and a cathode space, which are separated from one another by a solid electrolyte and are defined at least in some areas by a metal housing wherein the cathode space, in order to form the electrode, is filled with filamentary material of graphite or carbon that is saturated with sulfur. Between the solid electrolyte and the electrode of the cathode space, at least one intermediate film is provided, by means of which a sliding of the electrode along the surface of the solid electrolyte is assured.

Abstract: Sodium sulphur cells are commonly connected in parallel. It is a problem with such arrangements that if one cell sustains a short circuit failure, the parallel connected cells discharge through it. In an embodiment disclosed, a switch series connected to a cell or series of cells, goes open circuit should current in excess of a predetermined value and consequently associated with the failure of a cell, flow through the switch. The switch comprises a conducting rod separated into two portions and placed within a beta alumina tube containing sodium: the level of the sodium determines whether an electrical circuit is completed between the portions rendering the switch "on". Sodium, contained within an outer conducting tube, also surrounds the inner beta alumina tube, there being an electrical connection from the outer tube, via a resistor, to one portion of the rod.

Abstract: An alkali metal energy conversion device, particularly a sodium sulphur cell has a cylindrical outer casing (18) containing a tubular solid electrolyte (10) of beta alumina. An outer cathode region between the electrolyte (10) and the casing (18) contains sulphur, and an inner anode region in the electrolye tube contains sodium. An alpha alumina lid (12) closes the tube (10) and holds a current collector (15). The cathode region is sealed by an annular metal element (23) which is thermocompression bonded about its inner periphery to the lid (12) and is welded about its outer periphery to the casing (18). A second annular metal element (26) is thermocompression bonded to the lid (12) wholly inside the first annular element (23) and is welded to the current collector.The metal elements (23,26) are bonded to the lid (12) before the lid is glazed to the electrolyte tube (10) and before the first element (23) is welded to the casing (18).

Abstract: An alkali metal electro-chemical storage cell comprising anode and cathode regions containing alkali metal and cathodic reactant respectively. A cationically conductive solid electrolyte member separating the anode and cathode regions and respective anode and cathode current collectors. The cell is formed with a contact breaker region which in the event of a breach in the electrolyte member functions to make the cell become an open circuit and thus not provide a discharge path for any other cells connected thereto.

Abstract: Electrochemical storage cell of the sodium and sulfur type with an anode space and a cathode space which are separated from each other by a solid electrolyte and are bounded, at least in some regions, by a metallic housing. The cathode space contains the sulfur electrode which is made of a sulfur-impregnated graphite or carbon fiber material and the cathode space is subdivided into at least two and preferably more sectors which are separated from each other at least in some regions.

Abstract: A sodium-sulfur cell block having a plurality of sodium-sulfur cells is attached to, and held by, common terminals at both ends of the cells and in the long axes directions of the cells. In order to absorb thermal stress generated between the cells and the common terminals, at least one end is cantilevered at said common terminal.

Abstract: Several advantages as to ease of cell fabrication, maximum cell size, fiber breakage, tubesheet tightness, resistance to tubesheet deformation in prolonged service, safety, etc., can be realized by using as the tubesheet in a hollow fiber type battery cell one which is elongated in shape, has a substantially smaller diameter than the fiber "bundle" depending from it and in which the fiber ends passing through it are closely packed.

Abstract: A sodium-sulfur storage battery comprises an alpha alumina ring, a sodium conductive solid electrolyte tube and solder glass jointing said ring and said tube together; and is characterized in that the alpha alumina ring is provided at its open end with a groove for collecting the solder glass, a width of said groove is in a range from 0.2 mm to 5 mm and a depth of said groove is in a range from 0.2 mm to 10 mm. A surface of the solder glass is formed at a position inner than an end surface of the alpha alumina ring. Said groove may have a section of a rectangular shape. An inside surface of said groove may have a section of a round shape or an oblique section.

Abstract: Electrochemical storage cell of the sodium and sulfur type with an anode space and a cathode space which are separated from each other by a solid electrolyte and are bounded at least in places, by a metallic housing, with the cathode space for forming the sulfur electrode, filled with fiber material of graphite or carbon which is saturated with sulfur. A defined ratio of the value p of the thickness (d.sub.S) of the sulfur electrode to the wall thickness (d.sub.K) of the solid electrolyte is fixed.

Abstract: A secondary electrochemical cell with sodium-sulfur or other molten reactants is provided with a ionically conductive glass electrolyte. The cell is contained within an electrically conductive housing with a first portion at negative potential and a second portion insulated therefrom at positive electrode potential. The glass electrolyte is formed into a plurality of elongated tubes and placed lengthwise within the housing. The positive electrode material, for instance sulfur, is sealed into the glass electrolyte tubes and is provided with an elongated axial current collector. The glass electrolyte tubes are protected by shield tubes or sheets that also define narrow annuli for wicking of the molten negative electrode material.

Abstract: The sodium sulfur storage battery comprises a solid electrolyte tube; metallic fiber filled in said solid electrolyte tube; powder, grain or mixture of them of substance resistant to attack by molten sodium which has porosity smaller than that of the metallic fiber and is filled in a first space above the metallic fiber; a battery housing; a positive electroconductive material disposed in a space between the battery housing and the solid electrolyte tube; a ring disposed on the upper surface of the positive electroconductive material; powder, grain or mixture of them of substance resistant to attack by molten sulfur which is filled in a second space above said ring and is prevented from dropping by said ring; and a solder glass layer arranged on a portion of the outer peripheral surface of the solid electrolyte tube in said second space.

Abstract: Electrochemical storage cell of the Na/S type with an anode space and a cathode space separated by a solid electrolyte within which a safety container for sodium is arranged which is in communication with the interior of the solid electrolyte via a hole. A flow resistance having several discharge openings for passage of sodium is arranged in the hole of the safety container.

Abstract: This specification is directed to a method of making a current collector (14) for a sodium/sulfur battery (10). The current collector so-made is electronically conductive and resistant to corrosive attack by sulfur/polysulfide melts. The method includes the step of forming the current collector for the sodium/sulfur battery from a composite material (16) formed of aluminum filled with electronically conductive fibers selected from the group of fibers consisting essentially of graphite fibers having a diameter up to 10 microns and silicon carbide fibers having a diameter in a range of 500-1000 angstroms.

Abstract: An alkali metal energy conversion device, particularly a sodium sulphur cell has a cylindrical outer casing (18) containing a tubular solid electrolyte (10) of beta alumina. An outer cathode region between the electrolyte (10) and the casing (18) contains sulphur, and an inner anode region in the electrolyte tube contains sodium. An alpha alumina lid (12) closes the tube (10) and holds a current collector (15). The cathode region is sealed by an annular metal element (23) which is thermocompression bonded about its inner periphery to the lid (12) and is welded about its outer periphery to the casing (18). A second annular metal element (26) is thermocompression bonded to the lid (12) wholly inside the first annular element (23) and is welded to the current collector.The metal elements (23, 26) are bonded to the lid (12) before the lid is glazed to the electrolyte tube (10) and before the first element (23) is welded to the casing (18).

Abstract: A manufacturing method of a sodium-sulfur storage battery wherein a negative cover is thermocompressively jointed to an upper surface of an alpha alumina ring which are jointed with solder glass to a solid electrolyte tube, and a positive cover is thermocompressively jointed to a lower surface of said alpha alumina ring, is characterized in that diffusion layers of chrome are provided on the surfaces of the negative and positive covers, coating layers of aluminum are provided at least on the surfaces, which are thermocompressively jointed, of the negative and positive covers, and thermocompressively jointing surfaces are thermocompressively jointed in the air with aluminum rings thereon, respectively. Said negative and positive covers may be made from stainless steel, iron or alloy of iron and nickel. Said chrome diffusion layers may be about 20.mu.-120.mu. in thickness, respectively, and said aluminum layers may be about 5.mu.-90.mu. in thickness, respectively.

Abstract: The present disclosure describes a sodium-sulfur storage battery comprising a sodium-ion conductive solid electrolyte tube; a positive electroconductive material consisting of graphite felt or carbon felt, and a metal sulfide layer disposed between the solid electrolyte tube and the positive electro-conductive material. Said metal sulfide layer may be sulfurated metal such as aluminum, nickel, copper, iron, tin, zinc, lead, magnesium and chrome. A metal member may be disposed between the solid electrolyte tube and the positive electroconductive material to form said metal sulfide layer by a sulfurated part formed at least at the surface of said metal member.

Abstract: A power cell having an anode, a cathode and a solid electrolyte is improved by having as the solid electrolyte a glass comprising either (1) from about 22 mole percent to about 47 mole percent Na.sub.2 O, from about 4 mole percent to about 9 mole percent Y.sub.2 O.sub.3 and from about 47 mole percent to about 70 mole percent SiO.sub.2 or (2) from about 34 mole percent to about 47 mole percent Li.sub.2 O, from about 5 mole percent to about 9 mole percent Y.sub.2 O.sub.3 and from about 47 mole percent to about 58 mole percent SiO.sub.2.

Abstract: Electrochemical cells are provided with a reactive metal to reduce the oxide of the alkali metal electrode-reactant. Cells employing a molten alkali metal electrode, e.g., sodium, in contact with a ceramic electrolyte, which is a conductor of the ions of the alkali metal forming the electrode, exhibit a lower resistance when a reactive metal, e.g., vanadium, is allowed to react with and reduce the alkali metal oxide. Such cells exhibit less degradation of the electrolyte and of the glass seals often used to joining the electrolyte to the other components of the cell under cycling conditions.

Abstract: Several advantages as to ease of cell fabrication, maximum cell size, fiber breakage, tubesheet tightness, resistance to tubesheet deformation in prolonged service, safety, etc., can be realized by using as the tubesheet in a hollow fiber type battery cell one which is elongated in shape, has a substantially smaller diameter than the fiber "bundle" depending from it and in which the fiber ends passing through it are closely packed.

Abstract: Electrochemical storage cell of the alkali metal and chalcogen type with at least one anode chamber and one cathode chamber which are separated from each other by an alkali ion-conducting solid electrolyte and are bounded at least in some regions by a metallic housing, the solid electrolyte being fastened at its open end to the housing via a connecting element. At least one connecting element as a pressure ring and at least one compensating ring taking up the forces emanating from the pressuring ring are fastened at the open end of the solid electrolyte.

Abstract: Mixed crystals of the general formulaNa.sub.1+x M.sub.2-1/3x+y Si.sub.x Z.sub.3-x O.sub.12-2/3x+2ywhereinM represents one of the transition metals of the Fourth Group of the Peric System, Zr, Ti, Hf or mixtures thereof, Z represents one of the elements of the Fifth Group of the Periodic System, P, Sb, Bi, V, Nb, Ta or mixtures thereof, andx represents a number from 0.01 to 3, andy a number from 0 to 0.5,are new, and are suitable as ion-conducting electrolyte in electrochemical cells.

Abstract: A sodium-sulfur battery comprising molten sodium as an active material for a minus pole and molten sulfur as an active material for a plus pole, the molten sodium and molten sulfur being partitioned from each other by a sodium ion-permeating solid electrolyte such as .beta.-alumina as a boundary is provided with a sodium storage tank communicated with the molten sodium in the battery cell, a draining mechanism for withdrawing the molten sodium, when desired, from the battery cell into the sodium storage tank, and a circulating mechanism for purifying and returning the sodium from the sodium storage tank to the battery cell as the molten sodium, sodium can be discarged urgently from the battery at an accident of direct contact between the sodium and sulfur, with the result of improved safety.

Abstract: Electrochemical storage cell with at least one anode space and a cathode space separated from each other by an alkali-ion-conducting solid electrolyte and bounded at least in some areas by a housing. The housing is bounded on its inside by an inner housing element and on its outside by an outer housing element. The inner housing element acts as the current collector and embraces the two reactant spaces. The outer housing element assumes a support function and is arranged on all sides around the inner housing element in the manner of an enclosure. Preferably, the outer housing element is a tubular enclosure with two discs forming the end faces of the storage cell. The inner housing element is preferably made of aluminum and is provided with corrosion protection. The outer housing element can be made of a heat-resistant steel or an organic or inorganic material.

Abstract: In a sodium sulphur cell, improved protection of a cathode current collector is obtained by isostatically pressing graphite foil or flakes onto the surface of the collector, which surface is preferably roughened or coated with an intermediate conductive layer such as a nickel-chromium alloy or a conductive carbide providing a rough surface.

Abstract: Electrochemical storage cell based on alkali metal and chalcogen with an anodic space and a cathodic space which are separated from each other by an alkali ion-conducting solid electrolyte and are limited at least areawise by a metallic housing, and ceramic structural elements connected with metallic structural elements by thermocompression. The metallic structural elements connected with ceramic structural elements by thermocompression are very thin-walled at least in the joint region and are supported at least areawise by a reinforcement element of a metallic or non-metallic material.

Abstract: The invention provides an electronically conductive tectosilicate which has, trapped within and forming part of its framework structure at the molecular or atomic level, colloidal particles of one or more electronically conducted species, which act to render the tectosilicate electronically conductive. The invention further provides a method of making such electronically conductive tectosilicate, wherein, for example, a zeolite is precipitated from the solution which has an electronically conductive species such as colloidal graphite in suspension therein, so that the colloidal particles of the electronically conductive species are trapped within and form part of the framework structure of the precipitate at the atomic or molecular level. The invention also extends to electronically conductive artifacts, such as electrodes for electrochemical cells, which are made from the electronically conductive tectosilicate by compacting the artifact from particles of the tectosilicate.

Abstract: Method for the manufacture of an electrochemical storage cell of the sodium and sulfur type, with at least one anode space and one cathode space as well as an alkali ion conducting solid electrolyte separating the two, where at least one cathodic current collector and one electron-conducting matrix material are arranged in the cathode space. The invention is characterized by the features that in the cathode space at least one strongly anisotropic felt is inserted with the principal fiber direction parallel to the solid electrolyte; the felt is impregnated with at least one dissolved duromer; and thereupon a larger amount of the duromer is collected in the vicinity of the cathodic current collector; and the duromer is subsequently coked.

Abstract: High-temperature storage battery with at least two or more storage cells of the alkali metal and chalcogen type, with each cell bounded by a metallic housing, and wherein a defined number of storage cells forming a module are combined. The housing of each storage cell is formed by at least two concentrically arranged housing elements, which are separated from each other by electrical insulation, and the storage cells of each module are arranged in a defined manner, and adjacent storage cells are connected to each other at least in some regions via their outer housing elements.

Abstract: Sulfide glasses capable of conducting alkali metal ions are prepared from a nonmetal glass former such as GeS.sub.2, B.sub.2 S.sub.3 and SiS.sub.2 in mixture with a glass modifier such as Na.sub.2 S or another alkali metal sulfide. A molten mixture of the constituents is rapidly quenched to below the glass transition temperature by contact with a metal mold. The rapid quench is sufficient to prevent crystallization and permit solidification as an amorphous solid mixture. An oxygen-free atmosphere is maintained over the mixture to prevent oxidation. A new glass system of (1-X) Na.sub.2 O:XB.sub.2 S.sub.3 is disclosed.

Abstract: A corrosion resistant structure for a sodium-sulfur cell is described which comprises a container structure for the sulfur cathode including an outer metallic container having an inner surface defining a volume for containing the cathode, a layer of glass on the inner surface of the container, and a current collector of metallic foil disposed within the container adjacent the glass layer for containing the cathode. A preferred embodiment includes stainless steel as the container material and molybdenum foil as the current collector material.