DE4030944A1 - Molten carbonate fuel cell - has sintered cathode of lithium ferrite and opt. lithiated nickel oxide with high conductivity and catalytic activity - Google Patents

Abstract

Molten carbonate fuel cell (MCFC) has a metallic current transfer plate (6), a cathode (2), a matrix (5) impregnated with Li2CO3 and K2CO3 melt (4), an anode (3) and another metallic current transfer plate (7), laminated in the given sequence. The cathode (2) is sintered and is based on LiFeO2 and opt. lithiated NiO with esp. high electrical conductivity and esp. large intrinsic surface area such that, when used with a standard anode of sintered Ni contg. 15 (wt.)% Cr, it gives a cell resistance of 0.95+/- 0.15 ohm.cm. Pref. the cathode may also contain MgO (0-20%). The transfer plates consist of stainless steel plated with Ni on both sides and pref. are bipolar, with ducts for the fuel on one side and O2 on the other. The cathode is produced from carbonyl Fe (I) and opt. carbonyl Ni (granulation pref. 0.5-4 microns) plus one or more additives, an organic binder (III) vapourised at a temp. below the cell operating temp. and an emulsifying liq. (IV). The components are mixed to a homogeneous, bubble-free paste, made into a film and sintered at 550-650 deg.C in a reducing atmos. to a porous metal matrix. ADVANTAGE - The electrical resistance of the cathode is reduced, whilst its catalytic activity is increased. Also, a good and permanent contact between the transfer plates and cathode is ensured by chemical modification. (7pp Dwg.No.1/7)

Description

The invention relates to a molten carbonate fuel cell (MCFC = Molten Carbonate Fuel Cell) with a metallic flow plate, a cathode, a matrix in a soaking lithium carbonate (Li ₂ CO ₃ ) and potassium carbonate (K ₂ CO ₃ ) Melt, an anode and another metallic current transfer plate, which lie flat on top of one another in this order.

Carbonate melt fuel cells are among other things by the Essay by Dr. Peter Schütz "Fuel cells: the key to almost unlimited energy? "in the journal e & i, year 106, Issue 6, pages 238 to 244, through the "Fuel Cell Handbook" by Appleby & Foulkes, New York, 1989 and by the Journal of Power Sources, Vol. 29, No. 1 + 2, January 1990, "The molten carbonate fuel cell program in the Netherlands "by P.v. Dÿkum and K. Joon in: Fuel Cells Special Issue, p. 77-86 previously known. Because they directly transfer the chemically bound energy into elec they can convert tric energy, they make fuel Fe such as hydrogen, natural gas, biogas with higher Efficiency and with less impact on the environment in convert electrical energy than the previously known conventional thermal power plants, the efficiency of which by so-called Carnot process is limited to do.

According to the aforementioned publications, known carbo exist natural melt fuel cells consisting of a cathode and an anode, between which there is an electronically isolating, but for the ions formed from the fuel gases have a good ionic conductivity ze from lithium carbonate and potassium carbonate. The melt is generally characterized by capillary forces in between  Cathode and anode arranged porous ceramic matrix held. There is one on the outside of the anode and one on the cathode metallic power plate on which the electrical Potentials can be tapped. With known carbonate melt fuel cells, the anode is made of porous nickel and the porous lithiated nickel oxide cathode. At the Anode is the fuel gas, i.e. H. the hydrogen, oxidized, whereby Carbonate ions from the cathode to the anode through the electrolyte and the electrons through the outer circuit from the anode to the cathode. There the oxygen reacts with the im Cathode gas contained carbon dioxide and the one above the outside Circuit incoming electrons and forms carbonate ions that anodic, decomposes again with the release of carbon dioxide will.

From the aforementioned publications, it is also known meh rere such fuel cells to generate higher voltages to be stacked on top of each other. The two can metallic current transformer attached to each cell plates are designed as so-called bipolar plates and creasing on the side of one of the adjacent cells shaped channels for the oxygen and on the opposite side lying on the side groove-shaped channels for the fuel gas wear their immediately adjacent cell. Because the flow channels of known bipolar plates on both sides are arranged at right angles to each other, on one Face of the bipolar plate of the fuel and on that there to the immediately adjacent face of the oxygen or air forwarded and on the opposite side be sucked off again. Such molten carbonate fuel cells usually work at a temperature of 650 ° C, whereby in addition to hydrogen also convertible, hydrogen-containing gases can be implemented.

The lifespan of known molten carbonate fuel cells is limited by a variety of competing processes.  

It is a central problem of known carbonate melt- Fuel cells that the cell geometry is particularly characterized by Shrinkage and compression of the electrodes changed. So age Molten carbonate fuel cells by recrystallization of the Nickel anodes, by coarsening and flowing the carbonate melt-absorbing lithium aluminate matrix. One has this on the one hand a decrease in cell performance due to reduced Electrode surface and on the other hand higher electrical resistance during the current transfer from the electrodes to the me metallic current transformer plates result. These defects can NEN can not be remedied by pressing the Zel lenstapels increased, thereby the electrical contact between to improve the current transfer plates and electrodes, because the clear width of the cells can only be made slightly change. The clear width of the cell is essentially through the little changeable width of the wet seal, that is the Thickness of the matrix soaked in the melt. A Another problem is the insufficient catalytic activity and the too high electrical resistance of the cathodes. In the end corrode the metallic current transformer plates in lithium carbonate and potassium carbonate melts and enlarge the contact resistance between the electrodes and the metalli current transformer plates. The loss of electrolyte also leads gradually over the course of the fuel cell's life decrease in cell performance.

The invention is therefore based on the object of finding a way find that allows, on the one hand, the electrical resistance the cathode was reduced and at the same time its ka increase analytical activity. At the same time it should also go through chemical modification a good and permanent contact be secured between the current transfer plates and cathodes.

This object is achieved by the features of claims 1 and 6 solved. Further advantageous embodiments of the invention are claims 2 to 5 and 7 to 15.  

Characterized in that the cathode is sintered according to the invention and consists essentially of lithium ferrite (LiFeO ₂ ) and optionally lithiated nickel oxide (NiO) with a particularly high electrical conductivity and a particularly large inner surface, with the use of a standard anode consisting of sintered nickel with 15% by weight. % Chromium additive gives a cell resistance of 0.95 ± 0.15 ohm · cm ² , not only is the internal resistance of the cathode reduced, but, as will be explained, a prerequisite has also been created to reduce the electrical contact resistances throughout To reduce the molten carbonate fuel cell.

The fact that Invention as a starting material for the cathode according to carbonyl iron and optionally carbonyl nickel with an addition from at least one of the following five Groups of substances I, II, III, IV and V is used, this Aus material below the operating temperature of the furnace volatile organic binder and a die Bulk emulsifying liquid added and the bulk too a homogeneous, bubble-free, pasty mass is mixed and then processed into a film and at 550 to 650 ° C in a reducing atmosphere to a porous me tall matrix is sintered, the substance groups as follows put together,

Group I:
Perovskite materials of the ABO₃ type
With:
A = La, Sr, Y, Ba
B = Ni, Co, Fe, Ag, Mn,
for example: LaNiO₃; YNiO₃

Group II:
Perovskite materials of the type AB _0.5 C _0.5 O₃
With:
A = La, Sr, Y, Ba
B = Ni, Co, Fe, Ag, Mn, Cu
C = Ni, Co, Fe, Ag, Mn, Cu
for example:
LaNi _0.5 Co _0.5 O₃; SrNi _0.5 Co _0.4 O₃;
LaMn _0.5 Ni _0.5 O₃

Group III:
ABAO₄ type spinels
With:
A = Ni, Co, Fe
B = Ni, Co, Fe, Mn
for example: Fe₃O₄; Ni₃O₄; CO₃O₄

Group IV:
Semiconducting oxides
for example:
LiFeO₂; LiCuO₂; LiNiO₂; LiCoO₂; LiMnO₃

Group V:
Other additives
for example: La₂O₃; LaNi₅,

stabilization of the cathode matrix is achieved as well the electrical resistance of the cathode is also reduced. Except this is provided by the extraordinary delicacy of carbonyl iron as well as the carbonyl nickel the requirement for sufficient fine pores, which in turn are a prerequisite for are as large as possible. So the carbonyl iron is at the later commissioning of the cathode in the oxygen cell atmospheric at the prevailing operating temperatures oxi dated and in contact with the lithium carbonate-containing melt transformed into lithium ferrite with increasing volume. Through the se volume increase is the contact pressure of the electrodes to the Matrix and past the metallic power plates increasing, which among other things leads to a reduction in electrical contact resistance due to better sintering leads.

In a particularly advantageous embodiment of the invention, the Cathode also contain magnesium oxide. This will make the good wettability of the nickel oxide cathode for the carbonate melt ze due to the significantly poorer wettability of magnesium oxides compensated for this melt. The one with carbonyl iron and carbonyl nickel achievable fineness of the pores on the one hand and the good wettability of nickel oxide and lithium ferrite on the other hand there would otherwise be the danger that all pores with the  Lithium carbonate and potassium carbonate melt are soaked. The three-phase limit that is essential for the material turnover would be greatly reduced. With the amount of magnesium oxide you get hence a regulation to flood the pores of the cathode to prevent the melt and an optimal three-phase limit in the pores of the cathode between cathode, melt and acid adjust fabric.

It has proven to be particularly advantageous when in off design of the invention the magnesium oxide content 0 to 20% by weight the cathode mass. Here are the higher weights percentages for larger and the smaller percentages for weight smaller pores within the specified range turn.

A reduction in the contact resistance between the cathode and the immediately adjacent current transformer plate or bi polar plate can be achieved if in an advantageous Wei terbildung the invention the current applied to the cathode Transfer plate made of stainless steel, nickel-plated on both sides. Due to the nickel plating of the stainless steel power plate on this a firmly adhering coating is formed, which at corresponding procedure with nickel oxide formation well with the Sinter the cathode. The prerequisite is thus created to minimize contact resistance between the stainless steel of the bipolar plate and the nickel oxide cathode receive.

Advantageously, in an embodiment of the invention Starting material for the cathode carbonyl iron and given in the case of carbonyl nickel with a grain size in the range from 0.5 to 4 µm be used. This measure becomes the prerequisite for a later fine porosity of the cathode.

In an advantageous embodiment of the invention, the additives from groups I to V together 15 to 25 wt .-% of the mass  make up the cathode. This can reduce the conductivity of the Cathode can be improved without disturbing side effects.

Further details of the invention are based on one of the Figures illustrated embodiment explained. Show it:

Fig. 1 shows a section of a stack of fuel cells Karbonatschmelzen- in longitudinal section;

Fig. 2 is an enlarged view of the detail II in FIG. 1,

Fig. 3 is a plan view of the anode side of a bipolar plate, Fig. 4 is a plan view of the cathode side of a bipolar plate,

Fig. 5 used a plan view of the bipolar between two plates matrix,

Fig. 6 is a plan view of an electrode inserted between the matrix and the bipolar plate and

Fig. 7 is a schematic enlargement of the three-phase boundary in the cathode.

Fig. 1 illustrates the structure of a fuel cell stack 1 Karbonatschmelzen-. There, the two electrodes 2 , 3 lie on both sides of the matrix 5 impregnated with the electrolyte 4 . In the exemplary embodiment, the cathode 2 rests above the matrix 5 and the anode 3 abuts the matrix below the matrix 5 and so-called metallic current transformer plates 6 , 7 abut on both sides of the electrodes facing away from the matrix. In the exemplary embodiment, these current transformer plates are designed as bipolar plates 6 , 7 . These bipolar plates each have on their sides facing the electrodes pa parallel channels 8 , 9 for the fuel gas or the oxygen carrier. These channels open, as shown in FIGS. 3 and 4, at both ends of the channels 8 , 9 in bores 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 on opposite edges of the current transformer plates 6 , 7th The channels on one side of a bipolar plate open out on both sides in different bores than the channels on the opposite side of the same bipolar plate. Rectangular depressions 22 , 23 for receiving the electrodes 2 , 3 are embedded on both sides of the bipolar plates. For the sake of completeness, in the illustration of FIG. 1 in the rectangular depression 24 in the upper surface of the upper bipolar plate 6 , the anode 3 'of the next successive carbonate melt fuel cell and in the rectangular recess 25 in the lower surface of the lower bipolar plate 7, the cathode 2 '' of the next successive carbonate melt fuel cell and the matrixes 5 'and 5 ''of these two adjacent individual cells have been drawn.

In Fig. 3 it can be seen that the gas channels 9 on the anode side of the bipolar plate 7 open into relatively small bores 14 , 15 , 16 , 17 on both sides of the depression 22 for the anode 3 , while the gas channels on the cathode side, as the Fig. 4 shows, likewise on both sides of the depression 23 for the cathode 2 , opening into relatively large bores 10 , 11 , 12 , 13 . As shown in FIG. 5, the matrix 5 located between the two bipolar plates 6 , 7 and anode 3 and cathode 2 has bores 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 at the same points where the bipolar plates have their holes, and with the corresponding diameters. In this way, when stacking the bipolar plate, the matrix and the next bipolar plate, the respective bores go vertically through each individual cell and the entire stack 1, one overlying a single cell. As a result, the United supply lines (not shown) for the supply and suction of the fuel and the oxygen carrier can be ruled out at the upper and lower ends of the stack of molten carbonate fuel cells 1 .

In Fig. 6 it can be seen that the electrodes, that is, both the cathode 2 and the anode 3 , have the shape of a right angular plate, the dimensions of which correspond exactly to the depressions 22 , 23 on both sides of the bipolar plates 6 , 7 are adapted. With reference to FIG. 2 is further nen to erken that the bipolar plates 6, 7 are provided on the surface on both sides with a nickel layer 34. In addition, it is indicated in FIG. 2 by additional puncturing that the cathode 2 contains a higher proportion of porous nickel oxide on its side facing the bipolar plate 6 . This he increased nickel content, which has made it easier to oxidize to nickel oxide before sintering the anode 3 with the adjacent bipolar plates 6 , 7 .

When operating such a stack of molten carbonate fuel cells 1 , the oxygen or the oxygen-containing gas - such as air - through the holes 10 , 11 vertically through the entire fuel cell stack 1 and through the gas channels 8 of the individual bipolar plates 6 , 7 to the other side and there again in the bores 12 , 13 and conveyed out of the stack of carbonate melt fuel cells together with the water vapor. In the same way, the hydrogen-containing fuel gas flows through the small holes 16 , 17 in countercurrent into the fuel cell stack 1 and through the channels 9 of each individual bipolar plate 6 , 7 to the other side thereof and from there again into the small holes 14 , 15 and back out of the fuel cell stack.

At the operating temperature of the carbonate melt fuel cell 1 of approx. 650 ° C, the electrolyte 4 , the lithium carbonate and potassium carbonate melt is liquid. It is held in the pores of the matrix 5 by the capillary forces. In the exemplary embodiment, this consists of a porous mixed ceramic made of lithium aluminum aluminate and lithium zirconate. At the operating temperature, the liquid electrolyte rises into the pores of the adjacent electrodes 2 , 3 . The anode 3 consists of a sintered porous film made of lithiated nickel and titanium dioxide. This film is coated on its side against the matrix on its inner and outer surfaces with lithium titanate, which among other things has the property of promoting wetting with the molten electrolyte. On the other side of the matrix, the cathode 2 consists of a sintered, porous film consisting essentially of nickel and iron, which, when the fuel cell is started up for the first time, at the prevailing operating temperatures and the oxygen-containing atmosphere and in the presence of the melt containing lithium carbonate and potassium carbonate is converted to lithiated nickel oxide (NiO) and lithium ferrite (LiFeO ₂ ). In this way, the lithium ferrite has introduced a material into the cathode which has a significantly higher electrical conductivity than the lithiated nickel oxide and which helps to reduce the ohmic resistance of the cathode. In addition, the conversion of carbonyl iron to lithium ferrite takes place with a simultaneous increase in volume. This increase in volume causes the matrix to be pressed against the electrodes and the electrodes against the metallic current transformer plates. In addition to nickel oxide and lithium ferrite, the cathode contains up to 20% by weight magnesium oxide. In contrast to nickel oxide and lithium ferrite, this magnesium oxide is poorly wetted by the lithium carbonate and potassium carbonate-containing melt. With a metered addition of magnesium oxide, the capillary forces on the inner surfaces of the cathode can be regulated. In addition, the capillary forces strongly depend on the cross section of the pores. The aim is to add so much magnesium oxide that the pores are only partially filled by the melt. In particular, it must be avoided that the pores of the cathode fill up with the melt. While the addition of magnesium oxide on the cathode is intended to prevent the pores from filling with the melt, the capillary forces on the anode are regulated by the addition of nickel titanate, which is intended to compensate for the inadequate wetting properties of the nickel anode. Thus, the liquid electrolyte rises at the operating temperature in the pores of the adjacent anode and cathode, but without completely filling these pores, so that a sufficiently large three-phase boundary between the electrolytes, the respective electrode material and the gas form in the pores of the two electrodes, where the actual implementation takes place.

At the three-phase boundary in the anode, the hydrogen is broken down into two hydrogen ions and two electrons with the help of the catalytically active anode. The hydrogen ions react with carbonate ions from the melt to form water vapor and carbon dioxide. By the electrolyte 4 , which is held in the matrix 5 by the capillary forces, these carbons migrate from the cathode to the anode. The oxygen molecule is broken down at the cathode and reduced to oxygen ions. The oxygen ions react with carbon dioxide, which was added to the cathode gas, to form carbonate ions. The water vapor that forms under the operating conditions flows out with the excess fuel gas and the carbon dioxide released during the anode reaction via the channels 8 of each bipolar plate and the bores 12 , 13 .

In order to achieve the highest possible current densities, the largest possible inner and outer surfaces of the electrodes, including the cathode 2, would be required. However, because the conversion takes place at the three-phase boundary between the carbonate melt rising through the capillary forces in the pores of the cathode, the electrode surface and the gas - at the cathode the oxygen - there is an optimal pore size range. If the pores are too narrow, the capillary forces would continuously pull the melt into the pores and clog the pores. If the pores are too wide, the melt will not enter the interior of the pores sufficiently, or, if these were still further, the pores would simply fill up with the melt. In the FIG. 7 of the cathode 2 is sketched the desired three-phase boundary in a schematic, highly Enlarge th segment. The aim is that the pores should only be filled about half with the carbonate melt 4 due to the capillary forces. The gas access should remain free from the side of the current transfer plate 6 , 7 . On the other hand, the largest possible inner and outer surfaces are sought. For this reason, commercial carbonyl nickel with a grain size in the range of 0.5 to 4 µm is used in the manufacture of the cathode. It has proven to be quite advantageous if the maximum grain size distribution is 2.55 µm. Carbonyl nickel is a commercially available material, which is formed by the decomposition of Ni (CO) ₄ and is very pure and fine. Carbonyl iron is also a commercially available material that is manufactured using a similar process to carbonyl nickel and is similarly pure and fine-grained. Because of the good wettability of the nickel oxide with the melt, in the fineness of the pores that can be achieved with this starting material, the pores can only be filled up with the melt if a substance that is poorly wettable by the melt, here magnesium oxide, is added. The amount of magnesium oxide required is in the range from 0 to 20% by weight of magnesium oxide, depending on the pore diameter.

Because the nickel oxide cathode, in contrast to the nickel-containing Ano de has a relatively poor electrical conductivity addition to the lithium ferrite from the cathode material groups I to V, these are perovskite materials, as well Spinels and semiconducting oxides in amounts of 15 to 25% by weight admitted. These have the property of being in the presence of the Carbonate melt to partially decompose and the containing To release metals by doping the cathode material, e.g. B. of lithiated nickel oxide or lithium ferrite, the cathode impart additional conductivity.

The nickel oxide-containing cathode is very difficult to connect to the metallic current transformer plates. In order to nevertheless establish a good electrical connection here, the starting material for the cathode, the carbonyl nickel and / or the carbonyl iron, in addition to the additives from the groups of substances designated I to V, contains an organic binder which is volatile below the operating temperature of the fuel cell and an emulsifying mass Liquid added and the whole mixed to a homogeneous, bubble-free, pasty mass. Suitable binders are polyvinyl alcohol, such as polyvinyl butyrene, methyl cellulose, polyethylene glycol and linseed oil. They can be used alone or mixed with other binders. Water, low-chain alcohols such as ethanol, glycol and phenol-water mixtures are suitable as emulsifying liquids. They can also be used alone or as a mixture. The bubble-free, pasty mass obtained in this way is then processed into a film and subjected to a temperature treatment. The rolled or extruded film is first heated in a temperature range of 100 to 200 ° C and held in this temperature range until the emulsifying liquid is driven off. The temperature is then raised to 200 to 400 ° C so that the organic binder evaporates. After this has been done, the film is heated to 450 to 700 ° C in a reducing atmosphere containing hydrogen or forming gas. During this heating, which leads to a reducing sintering of the cathode, the cathode foil is already in the recess 24 of the associated bipolar plate 6 . This ensures that when the cathode is sintered it is also sintered together with the surface nickel-plated bipolar plate, so that a very low electrical contact resistance is formed between the nickel-containing cathode and the nickel-plated bipolar plate 6 during this process. If this cathode 2 sintered with the bipolar plate 6 later, when it is installed in a carbonate melt fuel cell, comes into contact with the oxygen-containing atmosphere at its operating temperatures of 650 ° C., the nickel of the cathode oxidizes to nickel oxide, among other things. This oxidation process also affects the connection between the cathode and the bipolar plate. But remains in the oxidation in the area of this interface between the cathode and bipolar plate, the nickel oxide-iron connection, so that a minimized ter electrical contact resistance is formed. If the cathode then comes into contact with the lithium carbonate of the melt under operating conditions, lithium ferrite (LiFeO ₂ ) forms with the carbonyl, which in turn makes a contribution to improving the conductivity of the cathode. In addition, the iron spinels formed during the decomposition of the substances of material group III in the presence of the melt contribute to a solidification of the cathode due to their rod-shaped structure. This consolidation also contributes to the stabilization of the mechanical structures in the carbonate melt fuel cell.

Claims (15)

1. Carbonate melt fuel cell (MCFC = Molten Carbonate Fuel Cell) with a metallic current transfer plate ( 6 ), a cathode ( 2 ), a matrix ( 5 ) in a soaking lithium carbonate (Li ₂ CO ₃ ) and potassium carbonate (K ₂ CO ₃ ) melt, an anode ( 3 ) and a further metallic current transformer plate ( 7 ), which lie flat one above the other in this order, characterized in that the cathode ( 2 ) is sintered and essentially made of lithium ferrite (LiFeO ₂ ) and optionally consists of lithiated nickel oxide (NiO) with a particularly high electrical conductivity and a particularly large inner surface, whereby when using a standard anode made of sintered nickel with 15% by weight chromium there is a cell resistance of 0.95 ± 0.15 Ohm · cm. 2. Carbonate melt fuel cell according to claim 1, characterized in that the cathode ( 2 ) additionally contains magnesium oxide. 3. Carbonate melt fuel cell according to claim 1 and / or 2, characterized in that the Magne silicon oxide content is 0 to 20% by weight of the cathode mass. 4. molten carbonate fuel cell according to one or more of claims 1 to 3, characterized in that the current transducer plate ( 6 , 7 ) lying on the cathode ( 2 ) consists of nickel-plated stainless steel on both sides. 5. molten carbonate fuel cell according to one or more of claims 1 to 4, characterized in that the current transducer plate ( 6 , 7 ) applied to the cathode ( 2 ) is designed as a so-called bipolar plate with bilateral flow channels, the flow channels on the one side for the fuel and the flow channels on the other side for oxygen. 6. A process for the production of a molten carbonate fuel cell cathode, in particular according to one or more of the claims 1 to 5, characterized in that carbonyl iron and optionally carbonyl nickel, each with an addition of one or more of the following five, are used as the starting material for the cathode ( 2 ) Substance groups I, II, III, IV and V are used, an organic binder volatile below the operating temperature of the fuel cell and an emulsifying liquid are added to these starting materials and the mass is mixed to form a homogeneous, bubble-free pasty mass and then processed into a film and at 550 up to 650 ° C in a reducing atmosphere to a porous metal matrix, the five groups of substances being composed as follows: Group I:
Perovskite materials of the ABO₃ type
With:
A = La, Sr, Y, Ba
B = Ni, Co, Fe, Ag, Mn,
for example: LaNiO₃; YNiO₃Group II:
Perovskite materials of the type AB _0.5 C _0.5 O₃
With:
A = La, Sr, Y, Ba
B = Ni, Co, Fe, Ag, Mn, Cu
C = Ni, Co, Fe, Ag, Mn, Cu
for example:
LaNi _0.5 Co _0.5 O₃; SrNi _0.5 Co _0.5 O₃;
LaMn _0.5 Ni _0.5 O₃Group III:
ABAO₄ type spinels
With:
A = Ni, Co, Fe
B = Ni, Co, Fe, Mn,
for example:
Fe₃O₄; Ni₃O₄; Co₃O₄Group IV:
Semiconducting oxides
for example:
LiFeO₂; LiCuO₂; LiNiO₂; LiCoO₂; LiMnO₃Group V:
Other additives
for example: La₂O₃; LaNi₅. 7. The method according to claim 6, characterized in that carbonyl iron and optionally carbonyl nickel with a grain size in the range from 0.5 to 4 µm are used as the starting material for the cathode ( 2 ). 8. The method according to claim 6 and / or 7, characterized in that the additives from groups I to V together 5 to 40 wt .-% of the mass of the cathode chen ( 2 ). 9. The method according to one or more of claims 6 to 7, characterized in that the additives from groups IV to V together make up 15 to 25 wt .-% of the mass of the cathode ( 2 ). 10. The method according to one or more of claims 6 to 9, characterized in that the Katho the film is gradually heated in a reducing atmosphere being used to volatilize the emulsifying liquid first to 100 to 200 ° C, then to volatilize the Binders to 200 to 400 ° C and finally for sintering 450 to 700 ° C is heated. 11. The method according to one or more of claims 6 to 10, characterized in that the sine tion takes place in the presence of hydrogen and / or forming gas. 12. The method according to one or more of claims 6 to 11, characterized in that the Katho the foil during sintering on the current transfer plate lies.   13. The method according to one or more of claims 6 to 12, characterized in that the gesin tert cathode in contact with the lithium carbonate (Li ₂ CO ₃ ) and potassium carbonate (K ₂ CO ₃ ) -containing melt and in the presence of oxygen is formed with the adjacent current transformer plate ( 6 , 7 ) at 550 to 650 ° C. 14. The method according to one or more of claims 6 to 13, characterized in that as a binder Polypvinyl alcohol, such as polyvinyl butyral and / or Methyl cellulose and / or polyethylene glycol and / or linseed oil ver be applied. 15. The method according to one or more of claims 6 to 14, characterized in that as emulgie liquid water and / or low-chain alcohols such as for example methanol, ethanol, glycol and / or phenol water mixtures can be used.