Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M12/00—Hybrid cells; Manufacture thereof
  • H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
  • H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
  • H01M12/065—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode with plate-like electrodes or stacks of plate-like electrodes

Definitions

• the present invention relates to lithium-ion batteries, in particular, lithium-air batteries which are suited for a broad range of applications, in particular, high-power applications, for example, traction accumulators for automotive applications.
• Lithium-ion batteries are used in a broad range of applications due to a relatively high energy storage capacity.
• lithium-ion batteries involve the use of a host crystal, like LiCo0 3 , the energy storage capacity is limited.
• Lithium-ion-air batteries promise a higher energy storage capacity per mass, because no host crystal is necessary.
• Oxygen is delivered to the electrode assembly as gas dissolved in a liquid medium (e.g. water).
• a battery comprising a composite layer which encloses both, a lithium-ion storing phase as well as a non-lithium-ion storing phase.
• Such coexisting phases require the use of costly and sensitive material.
• the structure of such a composite material comprising both phases inherently delimits the reaction rate, in particular, due to the limited mobility of the ions and the electrons.
• the two-phase structure of such a composite material is not stable with regard to ageing and thermal stress.
• prior art battery structures provide a delimited reaction rate due to delimited ion mobility and a delimited oxygen support rate.
• carbon powder-based frameworks which are commonly used on the cathode side, for providing electronic conduction from the current collector to the reaction zone require a significant amount of space which, however, is needed for the position of the reaction product Li 2 0 2 .
• the oxygen transport to the reaction zone via dissolution is delimited due to the limited solubility of oxygen in water.
• the battery structure used within the prior art allows only a delimited distribution of catalytically active material within the reaction zone.
• the concept underlying the invention is the use of a mixed conductor layer, which is conductive for lithium ions as well as for electrons. Since the mixed conductor layer is electronically conductive as well as conductive for ions, i.e. permeable for lithium ions, the mixed conductor layer provides at least a part of the reaction zone and, in particular, delivers electrons to the lithium ions in order to promote the desired reaction. In addition, the mixed conductor layer allows the transportation of gaseous oxygen directly repeat
• reaction rate can be significantly increased since the delivery of oxygen is not limited by the dissolvability in water. Rather, oxygen can directly be delivered to the reaction zone by a gas stream. This also relieves the battery construction from additional liquid material which significantly decreases the mass of the battery.
• the lithium-air battery comprises an Li-electrolyte layer which is an insulator for electrons and which conducts lithium ions.
• the lithium-ion source that is a solid layer of lithium (or a solid conductive layer comprising lithium or a lithium alloy), is protected from the reaction zone.
• the lithium is separated from oxygen by the lithium-electrolyte layer.
• the lithium-air battery according to the invention comprises therefore an anode structure and a cathode structure, wherein the anode structure further comprises a lithium- electrolyte layer forming an insulator for electrons and a conductor for lithium ions. Further, the battery comprises a mixed conductor layer which is conductive for lithium ions and which is conductive for electrons.
• the lithium-electrolyte layer is an insulator for electrical current, in contrast to the mixed conductor layer which is electronically conductive.
• both the lithium-electrolyte layer and the mixed conductor layer are permeable for lithium ions such that lithium ions can travel from a lithium source towards the reaction zone in order to be combined with oxygen.
• the lithium source i.e.
• a solid conductive layer comprising lithium, in particular comprising an Li- alloy is separated from the mixed conductor layer by the lithium-electrolyte layer.
• the lithium-electrolyte layer is sandwiched between the mixed conductor layer and the lithium source. Consequently, the mixed conductor layer is arranged on a surface of the lithium-electrolyte layer.
• the mixed conductor layer is arranged on the surface of the lithium-electrolyte layer which is directed towards the cathode structure or, in other words, the surface of the lithium-electrolyte layer supporting the mixed conductor layer faces towards the cathode structure.
• the mixed conductor layer is arranged on the surface of the lithium electrolyte layer, which is opposite to the lithium source (which can be provided by the solid conductive layer).
• the lithium-air battery comprises in a preferred embodiment catalytic active material which supports a reversible cathode reaction.
• the catalytic active material is distributed within the reaction zone. Consequently, the catalytic active material is carried by the mixed conductor layer.
• the catalytic active material is in form of particles and, preferably, in form of nanoparticles.
• a part of the catalytic active material (or all of the catalytic active material) is distributed on a surface of the mixed conductor layer, which is in opposite direction of the lithium-electrolyte layer.
• the mixed conductor layer is formed of a material which provides an electrode potential lower than the standard electrode potential of Li 2 0 2 to Li.
• the material of the mixed conductor layer provides an electrode potential versus lithium below 2.9 volt, below 2.8 volt, below 2.5 volt, below 2.2 volt, below 2 volt or below 1 .8 volt.
• the material providing the mixed conductor layer is conductive for lithium ions.
• the material of the mixed conductor layer is Li 4- x Mg x Ti 5-y (Nb,Ta)yOi2, wherein 0 ⁇ x ⁇ 2 and/or 0 ⁇ y ⁇ 0,1 or more advantageously 0 ⁇ x ⁇ 1 and/or 0 ⁇ y ⁇ 0, 05 .
• the material of the mixed conductor layer is another Li-Ti-Oxide according to:
• the anode structure comprises a solid conductive layer which comprises lithium.
• the lithium electrolyte layer is also a part of the anode structure.
• the lithium electrolyte layer sepa- rates the solid conductive layer, that is a layer of solid lithium, from the mixed conductor layer.
• the lithium-electrolyte layer is a solid Li-electrolyte layer, preferably impermeable for gases and H 2 0, in particular, impermeable for oxygen and C0 2 .
• the lithium- electrolyte layer comprises a solid lithium-ion conducting material, e.g. garnet type ceramics (e.g. Li 7 La 3 Zr 2 0i2) or LiSiCON-type ceramics (e.g. Li 1+x+y Al x (Ti,Ge)2-xSiyP 3 -yOi2).
• the lithium-electrolyte layer comprises a solid lithium-ion conducting material as defined in DE 102007030604 (garnet type ceramic) or as defined in EP 1926164 (LiSiCON-type ceramics).
• DE 102007030604 garnet type ceramic
• EP 1926164 LiSiCON-type ceramics.
• the mixed conductor layer as electron source/drain (depending on the operation mode of the battery).
• the mixed conductor layer also provides a current collector.
• the advantages of the first and the second embodiments are combined, and the mixed conductor layer is partly in the form of a meshwork for providing a high specific surface density, and in which the mixed conductor layer is also used as electrode, that is as current collector or electron supply.
• the mixed conductor layer is provided by a meshwork, preferably a nanowire meshwork.
• the meshwork supports catalytic active material, which supports a reversible cathode reaction.
• the catalytic active material is distributed within the meshwork.
• an additional, electrically conducting current collector provides the cathode electrode of the cathode structure.
• the current collector has a structure permeable for fluid, in particular for gas, for example, in form of a grid or of a perforated plate.
• the current collector is provided by an electrically conducting material, by conducting alloy or, particularly, by a metal.
• the current collector extends on the surface of the meshwork opposite to the anode structure.
• the mixed conductor layer is located between the current collector and the lithium- electrolyte layer.
• the mixed conductor layer is directly physically connected to the current collector.
• the mixed conductor layer is directly connected to the lithium-electrolyte layer.
• the mixed conductor layer is sandwiched by the current collector and the lithium-electrolyte layer.
• additional layers between the mixed conductor layer and the current collector can be provided, which are preferably electrically conducting.
• at least one additional layer is between the mixed conductor layer and the lithium-electrolyte layer, wherein the additional layer is permeable for lithium ions and electrically conducting or insulating.
• the mixed conductor layer is provided as a solid structure or as a porous structure.
• the mixed conductor layer is provided as a meshwork or as a nanowire meshwork.
• At least a part or all of the catalytic active material is supported on a surface of the mixed conductor layer, which is opposite to the anode structure, which is opposite the lithium- electrolyte layer.
• the catalytic active material is printed on the surface of the mixed conductor layer, which is opposite to the anode structure.
• the cathode electrode is provided by the mixed conductor layer itself. Therefore, the mixed conductor layer comprises an electrical connection hail
• the catalytic active material in the second embodiment is directly supported by the mixed conductor layer.
• the second embodiment shows that the mixed conductor layer can also provide a cathode electrode, since the mixed conductor layer is electrically conductive.
• the specific surface of the reactive region that is the mixed conductor layer
• the electrical connectivity of the cathode electrode the meshwork of the first embodiment is combined with the mixed conductor layer which forms a cathode electrode.
• the third embodiment comprises a mixed conductor layer with a first section and a second section.
• the first section is provided as a solid structure or as a porous structure.
• the first section allows a good electron conductivity, such that the first section of the mixed conductor layer provides a current collector or electron source with high conductivity.
• the second section is provided as a meshwork or as a nanowire mesh- work, which allows a high specific surface for the reaction zone (that is the second section of the mixed conductor layer). At least a part of the catalytic active material of the inventive lithium-air battery or all of the catalytic active material is supported by and is distributed within the meshwork of the second section.
• the first section provides the cathode electrode and extends on the lithium-electrolyte layer, in particular, on the sur- face of the lithium-electrolyte layer, which is opposite to the anode structure and directed towards the cathode structure.
• the second section extends on and extends from a plane in a direction opposite to the anode structure. In this way, the following structure and layer sequence is achieved: (solid lithium electrode)/lithium-electrolyte layer/first section of the mixed conductor layer (solid, high electrical conductiv- ity)/second section of the mixed conductor layer (high specific surface, carriers distributed active catalyst material).
• the reaction zone is focused on the second section, since this section provides a high specific surface.
• an electrical connection element can be connected to the first section of the mixed conductor layer.
• the second section extends away from the residual components of the lithium-air battery.
• the second section directly extends into the exterior of the battery and allows simple and effective support with oxygen or a gas mixture comprising oxygen (air).
• the first section as well as the second section are both provided by meshwork, for example, nanowire meshwork, wherein the density of the material providing the mixed conductor layer is substantially higher than the density within the second section.
• Such a density difference or gradient can be provided by compressing a part of a meshwork or by changing growth parameters, when providing the meshwork by a growth process.
• Figure 1 shows a first embodiment of the inventive battery
• Figure 2 shows a second embodiment of the inventive battery
• FIG. 3 shows a third embodiment of the inventive battery. Detailed description of the drawings
• FIG. 1 shows the first embodiment of the invention as described above.
• the lithium- air battery according to the first embodiment comprises a solid lithium-containing layer 10 which is connected to an electrical contact 12.
• the lithium layer 10 provides an an- ode electrode of the anode structure.
• an Li-electrolyte layer 20 is arranged which is permeable for lithium ions and forms an insulator for electrons.
• the mixed conductor layer 30 is arranged on the lithium-electrolyte layer 20, in particular on a surface opposed to the lithium layer 10.
• the mixed conductor layer is conductive for lithium ions as well as for electrons.
• the mixed conductor layer is formed of a meshwork which is depicted symbolically.
• the meshwork carries catalytic active material in form of particles, which are shown as dots located on the wires or needles forming the meshwork.
• a metal grid 40 is provided, which is in direct contact with the mixed conductor layer.
• the metal grid 40 is permeable for fluids, in particular, for gases due to its structure.
• the grid layer 40 comprises an electrical connection 42 which allows electrical connection to the grid 40, which forms the cathode electrode.
• the second embodiment as described above is depicted. Components which are similar in Figures 1 and 2 have the same reference sign.
• the second embodiment of the inventive lithium-air battery shown in Figure 2 comprises a solid lithium n
• the lithium-electrolyte layer 20 which comprises an electrical connection element 12.
• the lithium-electrolyte layer 20 is arranged on the lithium layer 10.
• the lithium-electrolyte layer 20 of Figure 2 is an insulator for electrons and conducts lithium ions (that is it is permeable for lithium ions).
• a mixed conductor layer 30' is located, which directly covers the surface of lithium-electrolyte layer 20 which is opposed to the solid lithium layer 10.
• the mixed conductor layer 30' supports catalytic active material on a surface of the mixed conductor layer 30' which is opposed to the lithium-electrolyte layer 20.
• the catalytic active material is in form of particles, wherein the particles are depicted as dots on the surface of the mixed conductor layer 30'.
• the mixed conductor layer of the embodiment shown in Figure 2 comprises an electrical contact 32 and, consequently, provides a cathode electrode (that is a current collector or an electron source for the inventive lithium-air battery).
• a cathode electrode that is a current collector or an electron source for the inventive lithium-air battery.
• mixed conductor layer 30' of Figure 2 is provided as porous layer or, in particular, as solid layer, preferably having open pores.
• the mixed conductor layer 30' of Figure 2 provides a lower specific surface in comparison to the mixed conductor layer 30 of the Figure 1 .
• the mixed conductor layer 30' of Figure 2 has the function of an electrode and, consequently, has to be provided in a dense structure for providing a high electrical conductivity.
• the active surface interacting with surrounding gas of Figure 2 is only the surface of the mixed conductor layer 30', which is opposed to the lithium-electrolyte layer 20 of Figure 2. Therefore, the distribution of the catalytic active material in Figure 2 is only two-dimensional, in contrast to the three-dimensional distribution in Figure 1 .
• the active region of Figure 2 is delimited onto the surface of the mixed conductor layer 30' opposed to the lithium-electrolyte layer 20.
• the active region in Figure 1 is provided by the space, to which the mixed conductor layer 30 extends.
• the third embodiment of the inventive lithium-air battery as described above is depicted. Components similar to the embodiments of Figures 1 and 2 have the same reference sign.
• the embodiment of Figure 3 comprises the conductive lithium layer 10, on which the lithium-electrolyte layer 20 is arranged.
• the solid lithium layer 10 comprises an electrical connection element 12.
• the third embodiment shown in Figure 3 further comprises the mixed conductor 30" which is arranged on the surface of the lithium-electrolyte layer 20 opposed to the conductive layer 10.
• the mixed conductor layer comprises two sections that is a first sec- n
• the first section 34 is provided like the mixed conductor layer 30' of Figure 2:
• the first section 34 is a high-density mixed conductor layer which provides a high electrical conductivity and is formed of a porous or solid structure.
• the specific surface of the first section 34 is of secondary interest.
• the second section 36 is provided in form of a meshwork, preferably a nanowire meshwork, and has a structure similar to the mixed conductor layer 30 of Figure 1 . Consequently, the second section 36 of the mixed conductor layer 30" is formed of a meshwork, preferably a nanowire meshwork, wherein the wires carry catalytic active material, preferably in form of particles (or nanoparticles). Therefore, the second section 36 has a high specific surface in order to allow a high reaction rate and a high support rate of gaseous oxygen.
• the first section 34 of Figure 3 comprises an electrical connection element 32 which provides the first section 34 as cath- ode electrode.
• the second section 36 provides the active reaction region, wherein the reactions within the first section 34 are insignificant. Consequently, the catalytic active material is distributed within the active region, that is within the secondary section 36. Further, the first section 34 does not comprise a significant amount of catalytic active material.
• the embodiments shown in Figures 1 , 2 and 3 are not drawn to scale.
• the thickness of the layers 10, 20, 30, 40, 30' and 34/36 are not drawn to scale.
• the size as well as the meshwork of layers 30 and 36 are not drawn to scale.
• the meshwork of the mixed conductor layer can be provided by a wire mesh- work, preferably by a nanowire meshwork.
• the catalytic active material can be provided by particles, preferably in form of powder or, in particular, in form of nanoparticles.
• the shape of the components shown in Figures 1 to 3 are only symbolic.
• the solid lithium layer i.e. the lithium source
• the solid lithium layer is provided in form of a rod or a plate.
• the mixed conductor layer is arranged onto this lithium-electrolyte layer.
• the mixed conductor layer is provided in two sections, an inner section (abutting to the lithium-electrolyte layer in form of a solid or porous mixed conductor layer) and an outer section equivalent to the second section in which the mixed conductor layer is provided by a meshwork, which preferably supports particles of catalytic active material.
• the inner section of the mixed conductor layer can be compared with the first section. Consequently, the first section comprises an electrical con- nection, and the innermost solid lithium layer comprises the complementary electrical connection element.
• the current collector or the mixed conductor layer provides the positive terminal of the battery
• the solid lithium layer provides the negative terminal of the lithium-air battery.
• the solid lithium layer is to be understood as inner element and can be provided in form of a rod or a plate.
• the lithium-electrolyte layer as well as the mixed conductor layer completely encompass the solid lithium layer and, consequently, have a similar shape as the solid lithium layer.
• a particular realization of the lithium-air battery system can comprise a plurality of lithium-air batteries according to the invention, which can be connected in parallel or in series (or in any sub-group combination thereof).
• the lithium-air battery system comprises a housing which encloses all batteries.
• a first electrical passage is provided through the housing in order to connect the lithium-air batteries within the housing with an external circuit.
• a second electrical passage is provided for connecting an oxygen sensor located within the housing in order to connect the inner oxygen sensor with external circuits, for example, with control circuits.
• the housing comprises an inlet in form of a support for gas.
• the housing comprises an outlet passage, which comprises an outlet valve. The housing provides a pressure containment for the lithium-air batteries arranged therein.
• the outer valve of the outlet passage is arranged outside the housing and allows to control the pressure within the pressure containment provided by the housing.
• the inlet of the housing is connected to an outlet of a C0 2 retention assembly.
• An inlet of the C0 2 retention is connected with an outlet of an H 2 0 trap.
• the inlet of the H 2 0 trap is connected to the outlet of an air compressor.
• the inlet of the air compressor is in fluidic connection to the exterior of the housing in order to support surrounding air to the battery system.
• the H 2 0 trap as well as the C0 2 retention assembly (which can be provided as a C0 2 retention membrane) provide a blocking element for water as well as for C0 2 and ensure that only oxygen and nitrogen are entering the housing.

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