Three-dimensionally structured lithium anode

Abstract

Method for producing a lithium anode (10) for a lithium cell and / or lithium battery, comprising the method steps: a) providing a current collector (11) and a protective layer (12), wherein the current collector (11) and / or the protective layer (12) has a surface structuring (110, 120) in which at least one raised surface section (112, 122) delimits at least one lower-lying surface section (111, 121); b) applying the current conductor (11) and the protective layer (12) to one another, wherein the surface structuring(s) (110,120) form at least one cavity (113,123) between the current conductor (11) and the protective layer (12); c) electrochemically filling the at least one cavity (113,123) with anode active material (13).

Description

The present invention relates to a method for producing a lithium anode, a lithium anode and a lithium cell and lithium battery equipped therewith.Prior ArtIn novel lithium cells and batteries, for example lithium-sulfur and lithium-oxygen / air cells and batteries, which use metallic lithium or a lithium alloy as anode active material instead of graphite, undesired, irreversible and damaging side reactions can occur at the anode surface between the anode active material and electrolyte or species contained therein. In order to protect the anode active material from this, a lithium-ion-conducting, dense and chemically as well as electrochemically stable protective layer can be applied to the anode surface.The publication DE 10 2011 089 174 A1 describes a battery anode component, the total amount of lithium of which is encapsulated in defined partitions in order to prevent lithium release in the event of damage.The document DE 10 2011079026 A1 describes an electrode having a basic structure made of a porous electrically conductive carbon-based material and metallic lithium, which is arranged at least partially in the pores of the basic structure.The publication DE 102011089174 A1 discloses a battery anode component for a battery cell having a current collector component with spatially separated recesses as lithium receiving spaces in which anode material units comprising lithium are arranged, and having a protective cover on the current collector component.The publication US 2005 / 0074671 A1 describes a method for producing an electrode, wherein at least one cavity is formed on a current collector, which cavity is surrounded by a plurality of support elements.The document WO 2011 / 058416 A1 describes a method for producing a negative electrode for a lithium secondary battery, wherein at least one cavity is formed on a current collector and between two opposite protective elements.The present invention relates to a method for producing an, in particular three-dimensionally structured and / or protected, lithium anode for a lithium cell and / or lithium battery.In a method step a), in particular a current collector and a protective layer are provided. In this case, the current collector and / or the protective layer can have a surface structuring in which at least one raised surface section delimits at least one surface section, in particular a lower or recessed surface section.In a method step b), the current collector and the protective layer are in particular placed against one another. This can be effected in particular in such a way that the surface structuring / s, for example of the current conductor and / or of the protective layer, form at least one cavity.In a method step c), the at least one cavity is filled electrochemically, in particular with anode active material.The term "lower" or "recessed" serves in particular to describe the formation of a surface section with respect to a surface section raised in this respect, in particular without limiting in this case with respect to its or its orientation with respect to the direction of gravity and / or the production method or methods for forming the respective surface sections.Because the anode active material, for example metallic lithium or a lithium alloy, is accommodated in the at least one cavity formed by the surface structuring of the current collector and / or the protective layer, the adhesion or adhesion between the active material, the current collector and / or the protective layer can advantageously be improved and mechanical adverse effects on the protective layer, for example detachment (delamination) and / or bursting of the protective layer, can be reduced or avoided. In particular, the three-dimensional surface structuring can deform, for example flexibly, and thereby maintain good adhesion between the active material, the current collector and / or the protective layer, for example in all states of charge, for example even if the volume and / or the amount of the anode active material in the anode fluctuates greatly due to deposition or dissolution between charging and discharging of the cell, and in this way can also compensate for severe volume movements and / or amount movements.Because the anode active material is filled electrochemically into the at least one cavity, the adhesion between the active material, the current collector and / or the protective layer can likewise be improved in a simple manner and mechanical adverse effects on the protective layer, for example detachment (delamination) and / or bursting of the protective layer, can be reduced or avoided. This can be explained by the fact that, as a result of the electrochemical filling of the at least one cavity, exactly the amount or the volume of anode active material is filled into the at least one cavity, which / s can be absorbed by the at least one cavity in the charged state, in which the anode active material generally has a larger volume (than in the uncharged state), for example at most.By improving the adhesion between the active material, the current collector and / or the protective layer and reducing the mechanical adverse effects on the protective layer, it is advantageously possible to increase the service life, performance and safety, and in particular also the cycle stability, of a lithium cell or lithium battery equipped with the lithium anode.Advantageously, such a lithium anode can be used in, for example, all, secondary and primary lithium cells and / or batteries which comprise or use metallic lithium (lithium metal anode) or a lithium alloy (lithium alloy anode).The anode active material may in particular comprise metallic lithium.In one embodiment, the anode active material is metallic lithium or a lithium alloy, for example a silicon-lithium alloy. For example, the anode active material may be metallic lithium. Thus, a high specific energy density can be advantageously achieved.The at least one deeper-lying (or recessed) surface section of the protective layer and / or of the current conductor can have a planar surface, for example. For example, the at least one lower surface section of the protective layer and / or of the current conductor may have a polygonal surface, for example a rectangular, for example square, triangular or hexagonal surface. The at least one deeper-lying surface section of the protective layer and / or of the current conductor can, however, also have a different geometric shape, for example an at least partially round shape, for example an ovaloid shape, such as an oval, a circle and / or an ellipse, and / or a drop-like shape.The at least one raised surface section of the protective layer and / or of the current conductor can, for example, enclose the at least one lower surface section of the protective layer or of the current conductor. For example, the at least one raised surface section of the protective layer and / or of the current conductor can, similar to a boundary line, delimit the at least one lower-lying surface section of the protective layer or of the current conductor. In this case, the surface of the at least one lower surface section of the protective layer and / or of the current conductor can be enclosed in particular between the at least one raised surface section of the protective layer or of the current conductor. For example, the at least one raised surface section of the protective layer and / or of the current collector can be configured in the manner of a wall or wall. The space surrounded by the at least one raised surface section of the protective layer and / or of the current conductor and the at least one lower surface section of the protective layer or of the current conductor can thereby represent at least one cavity.In particular, the at least one raised surface section of the protective layer and / or of the current conductor can surround or enclose a multiplicity of lower-lying surface sections of the protective layer or of the current conductor. In this case, the surfaces of the lower surface sections of the protective layer and / or of the current conductor can be enclosed in particular between the at least one raised surface section of the protective layer or of the current conductor. For example, the at least one raised surface section of the protective layer and / or of the current collector can be formed in a grid-like manner from wall-like or wall-like raised structures. The spaces surrounded by the at least one raised surface section of the protective layer and / or of the current conductor and the lower surface sections of the protective layer or of the current conductor can constitute cavities. In this case, the lower surface sections of the protective layer and / or of the current conductor can have planar surfaces, for example. For example, the lower surface sections of the protective layer and / or of the current conductor can have a polygonal, for example a rectangular, for example square, triangular and / or hexagonal surface. If appropriate, the lower surface sections of the protective layer and / or of the current conductor can also have two or more differently polygonal surfaces, for example selected from the group of rectangles, for example squares, triangles and / or hexagon. The lower surface sections of the protective layer and / or of the current conductor can, however, also have another geometric shape, for example an at least partially round shape, for example an ovaloid shape, such as an oval, a circle and / or an ellipse, and / or a drop-like shape. Such a surface structuring of the protective layer and / or of the current conductor can be formed in particular over the entire anode surface of the lithium anode to be produced.In principle, it may be sufficient if only the protective layer has a surface structuring in which at least one raised surface section delimits at least one lower surface section, or if only the current collector has a surface structuring in which at least one raised surface section delimits at least one lower surface section.Within the scope of a further embodiment, however, (at least) the protective layer has a surface structuring in which at least one raised surface section delimits at least one lower surface section. By introducing a surface structuring into the protective layer, the mechanical stability of the protective layer can advantageously be increased, for example according to the principle of reinforcing ribs. Thus, in addition to improved adhesion, an increase in the mechanical stability of the protective layer as such can advantageously be achieved and, as a result, mechanical adverse effects on the protective layer can be effectively reduced.In particular, however, both the current collector and the protective layer can have such a surface structuring.Within the scope of a further embodiment, the protective layer and the current collector therefore each have a surface structuring in which at least one raised surface section delimits at least one lower surface section, for example a multiplicity of lower surface sections. Thus, particularly good adhesion and compensation of volume movements and / or quantity movements can advantageously be achieved and mechanical adverse effects on the protective layer can be further reduced.The at least one raised surface section of the protective layer and the at least one raised surface section of the current conductor can be formed offset with respect to one another, for example, or, for example, in method step b), arranged offset with respect to one another, or placed against one another. In this case, the at least one raised surface section of the protective layer and the at least one raised surface section of the current conductor can each individually form cavities which optionally overlap one another or can open into one another. In this way, it is possible to improve adhesion and to reduce mechanical damage to the protective layer.Within the scope of a further embodiment, however, in method step b) at least one raised surface section of the protective layer and at least one raised surface section of the current conductor are placed against one another and together form at least one common cavity. For example, the surface-structured protective layer and the surface-structured current collector can be applied to one another such that the structures together form (common) cavities, in particular a multiplicity of (common) cavities. In particular, the at least one raised surface section of the protective layer can be configured, in particular substantially, congruently with the at least one raised surface section of the current conductor.The electrochemical filling of the cavities in method step c) with the anode active material, for example metallic lithium, can be effected, for example, during the first charging of a cell, in particular during the forming of the cell. The anode active material to be filled electrochemically into the cavities can be supplied by a cathode, for example a lithiated cathode, for example which contains at least one lithiated transition metal oxide, such as lithium manganese and / or nickel and / or cobalt oxide (LiNi / Mn / Co / O 2, LiCoO 2, LiMnO 2, LiNiO 2), etc.), and / or an electrolyte, for example an electrolyte containing lithium salts, for example which contains at least one lithium conducting salt, such as lithium hexafluorophosphate (LiPF 6).Within the scope of a further embodiment, therefore, in method step b) the current collector-protective layer arrangement is installed with a cathode comprising an oxidized form of the anode active material, in particular lithium ions, and / or an electrolyte comprising an oxidized form of the anode active material, in particular lithium ions, to form a cell, wherein method step c) takes place by the first charging, in particular forming, of the cell. By the first charging or forming of the cell, the oxidized form of the anode active material can be transported through the protective layer into the cavities and reduced and deposited in the cavities. Thus, the cavities can advantageously be filled electrochemically with the anode active material in a particularly simple manner.Alternatively, method step c) can also be carried out by applying the anode active material to the protective layer and filling the cavities electrochemically therewith. For example, in method step c), the anode active material can be placed on the protective layer in the form of a film, for example a lithium film.Within the scope of a further embodiment, therefore, in method step c) the anode active material, for example in the form of a film, is applied, for example placed, onto the protective layer. In particular, the anode active material, for example lithium, can be transported electrochemically through the protective layer (electrochemical transport). For example, a voltage, for example a charging voltage, can be applied to the anode active material applied to the protective layer, for example in the form of a film applied to the protective layer, and to the current collector. By applying the voltage, the anode active material can be transported through the protective layer into the cavities and deposited in the cavities. For example, metallic lithium can be applied, for example placed, as anode active material, for example in the form of a lithium foil, onto the protective layer.Thereafter, the anode active material, for example the lithium foil, applied to the protective layer can be removed again.Within the scope of a further embodiment, the method therefore further comprises, in particular after method step c), method step d): removing the anode active material applied to the protective layer, for example the film applied to the protective layer.The protected anode obtained in this way in the form of the current collector-protective layer arrangement filled electrochemically with anode active material, for example metallic lithium, can then be installed in a cell.Within the scope of a further embodiment, the method therefore further comprises, in particular after method step d): the following method step d'): installing the anode in the form of the electrochemically filled current collector-protective layer arrangement, in particular from method step d), in a cell.The protective layer and / or the current collector can be formed, for example, in the form of a continuous layer. For example, the surface structuring of the protective layer and / or of the current conductor, in particular in method step a), can be formed by rolling and / or embossing, in particular with a structured, for example embossed, roller, or by deep drawing or by chemical etching. In order to achieve the highest possible mechanical stability, the protective layer and / or the current collector can be designed in particular free of predetermined breaking points.The current collector can be formed in particular from an electrically conductive material. For example, the current collector may be formed from a metallic material.Within the scope of a further embodiment, the current collector is formed from copper. Copper advantageously has a good electrical conductivity, is comparatively cost-effective and can be formed in particular well by rolling and / or embossing. For example, the current collector may be formed of a copper foil.In the context of a further embodiment, the protective layer is lithium ion-conducting. In particular, the protective layer can be a dense, in particular liquid- and / or gas-tight, lithium-ion-conducting layer. The protective layer can be formed in particular from one or more chemically and electrochemically stable materials.Within the scope of a further embodiment, the protective layer is formed from a ceramic and / or polymeric, in particular lithium ion-conducting, material and / or from a composite, composite or multilayer concept of such materials.The process steps b) and / or c) can be carried out in particular under a protective gas atmosphere and / or under reduced pressure. Thus, side reactions of the anode active material filled into the cavity can be advantageously avoided.With regard to further technical features and advantages of the method according to the invention, explicit reference is hereby made to the explanations in connection with the anode according to the invention, the cell according to the invention and the battery according to the invention, and to the figures and the description of the figures.The present invention further provides a lithium anode for a lithium cell and / or lithium battery. The lithium anode can be structured three-dimensionally, for example, and / or protected, in particular by a protective layer.The lithium anode can be produced in particular by a method according to the invention and / or comprise a current collector and a surface-structured protective layer having at least one surface portion, in particular a recessed surface portion, bounded by a raised surface portion, wherein the current collector and the protective layer abut each other, wherein the surface structure of the protective layer forms at least one cavity, and wherein the at least one cavity is filled with anode active material, for example metallic lithium and / or a lithium alloy. As already explained in connection with the method according to the invention, mechanical adverse effects on the protective layer can be reduced by electrochemical filling and / or surface structuring of the protective layer and the adhesion between anode active material, current collector and / or protective layer can be improved and in this way the service life, performance and safety of a cell equipped therewith can be increased.Within the scope of an embodiment, the current collector is a surface-structured current collector having at least one surface section, in particular a recessed surface section, bounded by a raised surface section. Thus, adhesion can be further improved and mechanical adverse effects on the protective layer can be further reduced.The at least one recessed surface portion of the protective layer and / or of the current conductor can be recessed in particular with respect to the (respective) raised surface portion. In particular, the at least one recessed surface section of the protective layer and / or of the current conductor can be a surface section referred to as lower in the context of the method.Within the scope of a further embodiment, at least one raised surface section of the current conductor and at least one raised surface section of the protective layer abut each other and together form at least one common cavity. For example, the surface-structured protective layer and the surface-structured current collector can be applied to one another such that the structures together form (common) cavities, in particular a multiplicity of (common) cavities. In particular, the at least one raised surface section of the protective layer can be configured, in particular substantially, congruently with the at least one raised surface section of the current conductor.The protective layer and / or the current collector can be formed, for example, in the form of a continuous layer. In order to achieve the highest possible mechanical stability, the protective layer and / or the current conductor can be free of predetermined breaking points in particular.With regard to further technical features and advantages of the anode according to the invention, explicit reference is hereby made to the explanations in connection with the method according to the invention, the cell according to the invention and the battery according to the invention, and to the figures and the description of the figures.The present invention further relates to a lithium cell and / or lithium battery which comprises at least one lithium anode according to the invention. The lithium battery can in particular comprise at least two lithium cells according to the invention, for example each equipped with a lithium anode according to the invention. In the lithium battery, the at least two cells according to the invention can be connected together in particular.With regard to further technical features and advantages of the cell and battery according to the invention, explicit reference is hereby made to the explanations in connection with the method according to the invention and the anode according to the invention, and to the figures and the description of the figures.DRAWINGSFurther advantages and advantageous embodiments of the subject matter according to the invention are illustrated by the drawings and explained in the following description. It should be noted that the drawings are merely descriptive in nature and are not intended to limit the invention in any form. They show FIGS. 1 a- 1 dshow schematic cross sections to illustrate an embodiment of a method according to the invention for producing a three-dimensionally structured lithium anode; and FIG. 2 shows a schematic perspective view of an embodiment of a three-dimensionally structured lithium anode according to the invention.FIGS. 1 ato 1 d illustrate an embodiment of the method according to the invention for producing a three-dimensionally structured lithium anode 10 for a lithium cell and / or lithium battery.FIG. 1 ashows that within the scope of this embodiment, in a method step a) a surface structured current collector 11 and a surface structured protective layer 12 are provided, in particular three-dimensionally. In this case, both the current collector 11 and the protective layer 12 have a surface structuring 110, 120, in which 110, 120 border wall-like or wall-like raised surface sections 112, 122 of deeper lying or recessed surface sections 111, 121. The raised surface sections 112, 122 serve as boundary lines which delimit deeper planar surfaces 111, 121 enclosed therebetween. The surfaces 111, 121 can be square, for example, as illustrated in FIG. 2. The current collector 11 and the protective layer 12 are each formed in the form of continuous layers. The current collector 11 can be, for example, a copper foil. The protective layer 12 can be formed in particular from a ceramic and / or polymeric, lithium-ion-conducting material and / or from a composite, composite or multilayer concept of such materials. The surface structures 110, 120 of the current conductor 13 and of the protective layer 12 can be formed, for example, by rolling and / or embossing, for example with a structured or embossed roller, or by deep drawing or by chemical etching.FIG. 1 bshows that in a method step b), the two surface-structured layers, namely the current collector 11 and the protective layer 12, have been applied to one another or applied to one another such that the surface structures 110, 120 together result in common cavities 113, 123. FIG. 1 billustrates that the raised surface sections 122 of the protective layer 12 are formed substantially congruently with the raised surface section 112 of the current conductor 11 and have been placed against one another in such a way that they 112, 122 together form common cavities 113, 123.FIG. 1 cillustrates that, within the scope of this embodiment, the, in particular common, cavities 113, 123 are electrochemically filled with anode active material 13, in particular metallic lithium, by applying anode active material 13 in the form of a film, in particular in the form of a lithium film, to protective layer 12 in a method step c) and applying a voltage to anode active material 13 applied to protective layer 12 and to current collector 11. FIG. 1 cillustrates that, by applying the voltage, the anode active material is converted into an oxidized form, in particular into lithium ions, which can be transported through the protective layer 12 into the cavities 113, 123 and deposited there again in reduced form, in particular as metallic lithium.FIG. 1 dillustrates that, within the scope of this embodiment, the anode active material 13 applied to the protective layer 12 can be removed after the electrochemical filling in a method step d). The resultant anode 10 in the form of the electrochemically filled current collector-protective layer arrangement 11, 12, 13 can then be installed in a cell in a method step d') (not shown).Alternatively to electrochemical filling by applying and removing the anode material 13 to the protective layer 12, the electrochemical filling in method step c) can also take place during the first charging or within the scope of forming a cell with a lithiated cathode, for example comprising a lithiated transition metal oxide, such as lithium cobalt oxide (LiCoO 2).Thus, a lithium metal anode protected by the protective layer 12 or a lithium alloy anode 10 having a three-dimensional structuring can advantageously be produced, which is distinguished by an improved adhesion between the current collector 11, anode active material 13, for example lithium, and the protective layer 12 and increased mechanical stability and an associated increased lifetime, cycle stability, performance and safety and can withstand, in particular, high volume surges occurring during charging / discharging.FIG. 2 shows a schematic, perspective view of an embodiment of a three-dimensionally structured lithium anode 10 according to the invention, which is producible or produced by the embodiment of the production method according to the invention explained in the context of FIGS. 1 ato 1 d.FIG. 2 illustrates that the lithium anode 10 comprises a surface-structured current collector 11 having a plurality of surface sections 111 bounded by a grid-like raised surface section 112, in particular recessed with respect to the raised surface section 112, and a surface-structured protective layer 12 having a plurality of surface sections 121 bounded by a raised surface section 122, in particular recessed with respect to the raised surface section 122. The current collector 11 and the protective layer 12 are each formed in the form of continuous layers. The raised surface sections 112, 122 serve as boundary lines which delimit planar, square surfaces 111, 121 enclosed therebetween. FIG. 2 illustrates that the raised surface sections 112, 122 of the current conductor 11 and of the protective layer 12 bear congruently against one another and together form a multiplicity of common cavities 113, 123, which are filled with anode active material 13, in particular metallic lithium. FIG. 2 also illustrates that the structure described within the scope of FIGS. 1a to 1d can be formed in particular on the entire anode surface. A three-dimensionally structured lithium anode 10 illustrated in FIG. 2 advantageously makes it possible to provide a secure, powerful, long-lived and cycle-stable lithium cell or lithium battery.

Claims

Method for producing a lithium anode (10) for a lithium cell and / or lithium battery, comprising the method steps: a) providing a current conductor (11) and a protective layer (12), wherein the current conductor (11) and / or the protective layer (12) has a surface structuring (110, 120), in which at least one raised surface section (112, 122) delimits at least one lower surface section (111, 121); b) mutually applying the current conductor (11) and the protective layer (12), wherein the surface structuring / s (110, 120) form at least one cavity (113, 123) between the current conductor (11) and the protective layer (12); c) electrochemically filling the at least one cavity (113, 123) with anode active material (13).The method of claim 1, wherein the protective layer (12) includes a surface pattern (120) in which at least one raised surface portion (122) defines at least one underlying surface portion (121).Method according to Claim 1 or 2, wherein the protective layer (12) and the current collector (11) each have a surface structuring (120, 110), in which (120, 110) at least one raised surface section (122, 112) delimits at least one lower-lying surface section (121, 111).Method according to one of Claims 1 to 3, wherein, in method step b), at least one elevated surface section (122) of the protective layer (12) and at least one elevated surface section (112) of the current conductor (11) are placed against one another and together form at least one common cavity (113, 123).The method according to any one of claims 1 to 4, wherein the anode active material (13) is metallic lithium or a lithium alloy.Method according to one of Claims 1 to 5, wherein in method step b) the current collector-protective layer arrangement (11, 12) is installed to form a cell with a cathode comprising an oxidized form of the anode active material, in particular lithium ions, and / or an electrolyte comprising an oxidized form of the anode active material, in particular lithium ions, wherein method step c) takes place by the first charging of the cell.Method according to one of Claims 1 to 6, wherein in method step c) the anode active material (13), in particular in the form of a film, is applied to the protective layer (12) and the anode active material (13) is transported electrochemically through the protective layer (12).Method according to claim 7, wherein the method further comprises the method step d): removing the anode active material (13) applied to the protective layer (12), in particular wherein the method further comprises the method step d'): installing the anode (10) in the form of the electrochemically filled current collector-protective layer arrangement (11, 12, 13) in a cell.Method according to one of Claims 1 to 8, wherein the current collector (11) is formed from copper and / or wherein the protective layer (12) is formed from a ceramic and / or polymeric material and / or from a composite, composite or multilayer concept of such materials.The method according to any one of claims 1 to 9, wherein the protective layer (12) is lithium ion conductive.Lithium anode (10) for a lithium cell and / or lithium battery, comprising - a current collector (11), and - a surface-structured protective layer (12) having at least one surface portion (121) bounded by a raised surface portion (122), wherein the current collector (11) and the protective layer (12) abut each other, wherein the surface structuring (110) of the protective layer forms at least one cavity (123) between the current collector (11) and the protective layer (12), and wherein the at least one cavity (123) is filled with anode active material (13), in particular metallic lithium.Lithium anode (10) according to Claim 11, wherein the current collector (11) is a surface-structured current collector (11) having at least one surface section (111) bounded by a raised surface section (112).Lithium anode (10) according to Claim 11 or 12, wherein at least one elevated surface section (112) of the current conductor (11) and at least one elevated surface section (122) of the protective layer (12) bear against one another and together form at least one common cavity (113, 123).Lithium cell and / or lithium battery, comprising at least one lithium anode (10) according to one of Claims 11 to 13.

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