Flat silicon anode on a copper conductor for a lithium-ion battery

Abstract

The present invention relates to a silicon electrode suitable for use as an anode in a lithium-ion battery, comprising a current collector preferably made of copper, an adhesive layer disposed on the current collector, and a multilayer structure disposed on the adhesive layer. The object of providing a Si electrode that is not pulverized when lithium is incorporated, and thus does not lose electrical contact with the current collector as a result, and has a stable surface and high intrinsic conductivity, is achieved in that the multilayer structure as the active layer of the Si electrode is formed by at least one layer made of metal and silicon, or by a mixed system consisting of silicon mixed with at least one metal, and the multilayer structure is subjected to rapid tempering to form a conductive metal silicide matrix, and the metal silicide matrix contains amorphous nanocrystalline regions of silicon.

Description

Technical Field

[0001] The present invention relates to a silicon electrode suitable for use as an anode in a lithium-ion battery, preferably comprising a current collector made of copper, an adhesion layer disposed on the current collector, and a multi-layer structure disposed on the adhesion layer.

[0002] The present invention further relates to a battery cell comprising the silicon electrode according to the present invention, and to a battery comprising at least one battery cell.

Background Art

[0003] Electrochemical energy storage is an important pillar of the global energy revolution for the temporary storage of variable renewable power and for the supply of said power for stationary and portable applications. Due to the rapid development in the field of electro-mobility and in mobile communication devices, the demand for large storage capacities and high charging rates for energy storage devices is also increasing. In this regard, established technologies have reached their limits. Diversification of energy storage concepts as well as new materials are required, particularly to counteract shortages related to raw materials and thus, in particular, the increasing cost of secondary batteries. First, it is required to improve the technical performance (including capacity, energy density, service life) of the relevant energy storage concepts, and second, to minimize the manufacturing costs. The latter can be ensured, in particular, by using readily available chemical elements such as silicon for which an extensive technical base already exists.

[0004] A battery is an electrochemical energy storage device and is classified into a primary battery and a secondary battery.

[0005] A primary battery is an electrochemical power source in which chemical energy is irreversibly converted into electrical energy. A primary battery is, therefore, not rechargeable. A secondary battery, also referred to as a storage battery, on the other hand, is a rechargeable electrochemical energy storage device in which the chemical reactions that occur are reversible, which means that it can be used repeatedly. Electrical energy is converted into chemical energy when charging and then back into electrical energy from chemical energy when discharging.

[0006] A battery is a general term for a series of cells connected together. A cell is a galvanic unit consisting of two electrodes, an electrolyte, a separator, and a cell housing. Figure 1 shows an exemplary structure and function of a lithium-ion cell during the discharge process. The components of the cell will be briefly described below in this specification.

[0007] Each Li-ion cell consists of two different electrodes 7 and 9, an electrode 7 that is negatively charged in the charged state and an electrode 9 that is positively charged in the charged state. During the release of energy, i.e., during discharge, ions move from the negatively charged electrode to the positively charged electrode, so that the positively charged electrode is referred to as the cathode 7 and the negatively charged electrode is referred to as the anode 9. The electrodes are each composed of a conductor 2, 8 (also referred to as a current collector), and an active material applied thereon. First, an ion-conductive electrolyte 4 that enables the necessary charge exchange and a separator 5 that ensures electrical separation of the electrodes are between the electrodes.

[0008] The cathode consists of, for example, a mixed oxide applied to an aluminum current collector. Transition metal oxides having cobalt (Co), manganese (Mn), nickel (Ni) or aluminum oxide (Al2O3) are the most common compounds. The applied metal oxide layer serves for the intercalation of lithium ions when the cell is discharged.

[0009] The anode of a lithium-ion cell can consist of a copper foil as a current collector and a layer of carbon as an active material. The carbon material used is generally natural or artificial graphite, because its electrode potential is low and the volume expansion during the charge and discharge processes is small. During the charging process, lithium ions are reduced and intercalated into the graphite layer.

[0010] In the structure of a lithium-ion battery, the cathode typically supplies lithium atoms for charging and discharging at the anode, and thus the battery capacity is limited by the cathode capacity. As already mentioned, examples of typical cathode materials used to date are Li(Ni, Co, Mn)O2 and LiFePO4. Since the structure of the cathode is based on lithium metal oxides, an increase in capacity is only possible to a limited extent.

[0011] It is also known to use silicon instead of carbon in the anode of a Li battery. Silicon is a semiconductor with poor conductivity, very hard and highly brittle, and its surface reacts with oxygen to form silicon dioxide. However, silicon as an anode material has a high storage capacity of 3579 mAh / g at room temperature compared to conventional carbonaceous materials such as graphite, which has a storage capacity of 372 mAh / g. Compared to pure metallic lithium, silicon has a significantly reduced reactivity and prevents the formation of dendritic structures, especially at high surface currents. Dendrites are tree- or bush-like crystal structures that can penetrate the separator, resulting in a short circuit of the battery and thus the cell quickly becoming inoperable. However, the problems that occur when using silicon as an anode material include the significant change in the volume of the host matrix (volume shrinkage and expansion) during the intercalation and deintercalation of mobile ionic species during the charge and discharge of the corresponding energy storage device. In the case of lithium intercalation, Li 15Alloying with lithium to form Si4 results in a volume expansion of up to 400%. The volume change in the case of graphite is approximately 10%. The volume change of the anode material when using silicon leads to internal stress, cracking, pulverization of the active material (silicon) in the host matrix, and ultimately complete destruction of the anode. The highly brittle Si layer breaks up and loses electrical contact with the conductive current collector, resulting in the loss of the active material. At the same time, a gradual disintegration of the surface of the Si anode occurs, which, together with the simultaneous breakdown of the electrolyte, causes continuous enhancement of the solid electrolyte interphase (SEI).

[0012] So far, nanostructures with a maximum of 100 nm for crystalline silicon and a maximum of 1 μm for amorphous silicon have been considered suitable for homogeneous volume expansion. This makes it possible to compensate for the stress of volume expansion without the surface disintegrating. Nevertheless, this thickness is completely insufficient to match the storage capacity of current lithium-ion batteries, which requires a structure of at least 5 μm of pure silicon corresponding to an ideal capacity of 3.5 mAh / cm 2 2.

[0013] The focus of previous research in the field of lithium-ion batteries has been placed on the development of silicon nanostructures to prevent the pulverization of the silicon used, and on ensuring continuous electrical contact with the current collector during volume expansion in the operation of the battery. In the case of pure silicon, it is known that only the use of nanowires was possible. For powdered or particulate silicon, a suitable conductive adhesive or binder is required to ensure electrical contact. Silicon powder is currently provided together with a binder and applied to the current collector in a slurry process. Despite this, due to the volume expansion of silicon that occurs during lithium intercalation, its use has so far been limited to less than 20% by volume of silicon in the slurry. A slurry is understood to mean a mixture of solid substances in which solids are dispersed in a liquid. In a slurry-based process, a layer of silicon particles is applied to the current collector with a carbonaceous binder or calendared thereon. The binder ensures adhesion and electrical contact between the particles and with the current collector. Considerable efforts have been made so far to produce macroscopic amounts of silicon with a nanoporous structure. The conductivity of the structure is limited by the conductivity of the binder. The porous structure has a large surface area and thus tends to form a large solid electrolyte interface (SEI).

[0014] Silicon-based anodes developed so far generally have the following problems: large volume expansion during lithium intercalation, associated pulverization of the material and loss of electrical contact with the current collector, unstable anode surface, and poor intrinsic conductivity.

Prior Art Documents

Non-Patent Documents

[0015]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0016] Therefore, an object of the present invention is to identify a silicon electrode suitable for use as an anode in a lithium-ion battery and having none of the problems summarized above.

Means for Solving the Problems

[0017] This object is achieved by the silicon electrode according to independent claim 1.

[0018] The silicon electrode according to the present invention, designed and intended for use as an anode in a lithium-ion battery, preferably comprises a current collector composed of copper, an adhesion layer disposed on the current collector, and a multi-layer structure disposed on the adhesion layer. The multi-layer structure as the active layer of the Si electrode is formed from at least one layer composed of a metal and silicon, or from a mixed system composed of silicon mixed with at least one metal. The multi-layer structure is subjected to rapid thermal annealing to form a conductive metal silicide matrix, and the metal silicide matrix surrounds the amorphous nanocrystalline regions of silicon.

[0019] The adhesion layer in one configuration of the Si electrode according to the present invention is formed from one or more of the materials titanium (Ti), silicon (Si), chromium (Cr), tantalum (Ta) and / or tungsten (W).

[0020] The adhesion layer ensures extremely stable contact between the active layer of the anode and the current collector of the anode, firstly, by mechanical adhesion due to the roughened surface and, secondly, by (partial) reaction (chemisorption) with the substrate. Adhesion layers that can be used or employed consist of titanium or chromium as adhesion promoters and use a suitable diffusion barrier such as tungsten or carbon, and silicon itself can be used as the adhesion layer.

[0021] Rapid thermal annealing with controllable and defined energy input into the silicon layer of the multilayer structure results in a partial reaction of the silicon with the copper current collector and the formation of a roughened surface, thereby establishing extremely strong adhesion between the multilayer structure and the current collector that does not weaken during battery operation.

[0022] The multilayer structure as the active layer of the Si electrode is formed from at least one layer. One layer includes a deposited layer of an active material capable of lithium intercalation and one or more layers of metal. Depending on the target capacity, the thickness of the active layer of the electrode, i.e., the layer of the composite of the active material and the metal, can be composed of one or more layers. As an alternative, at least one layer can be formed from at least one metal and silicon. The silicon and at least one metal are applied by alternately depositing separate layers of the materials. One layer is thus formed from at least one layer of at least one metal and one layer of silicon, and the target thickness of the anode is achieved by forming multiple layers in the multilayer structure (Figure 5). As another alternative, at least one layer may be formed by a mixed system, and the mixed system of silicon is mixed with at least one metal (Figure 6). This homogeneous mixture of at least one metal and silicon can be produced from a sintered powder sputtering target (Figure 8b) or it is deposited by co-deposition of the starting materials (Figure 8a) to form a mixed layer. The layer thickness in the case of silicon is 500 - 1000 nm, and in the case of the metal, the layer thickness is 10 - 100 nm. This means that a multilayer structure of the active layer with a total thickness of 5 μm can consist of a maximum of 20 individual layers.

[0023] Volume expansion occurs during lithium intercalation, but the pulverization of the silicon layer does not occur through the mixing of metals and the use of a multi-layer structure. The mixing of metals leads to the formation of an alloy with a reduced hardness compared to pure silicon. At the same time, a very high electrical conductivity of silicon is brought about compared to graphite. Despite the mixing of metals, a specific total capacity exceeding 2000 mAh / g is ensured.

[0024] The stability and high electrical conductivity of the silicon electrode according to the present invention are maintained by the formation of a heterogeneous structure involving the formation of a conductive matrix of a metal or metal silicide surrounding the amorphous regions of silicon.

[0025] In one configuration of the silicon electrode according to the present invention, a further layer composed of silicon or a mixed system, and / or a protective layer forming a planar surface, is disposed on the multi-layer structure.

[0026] The deposition technique used for the multi-layer structure, such as sputtering, results in the formation of a planar surface. Next, a layer composed of silicon or a mixed system of silicon and one or more metals, and / or a protective layer, can be disposed thereon up to the desired layer thickness. The planar layer structure has a small surface area that does not change during the operation of the battery. This minimizes the enhancement of the SEI and the depletion of the electrolyte.

[0027] In a further configuration of the silicon electrode according to the present invention, a boundary layer and / or a solid electrolyte is disposed on the planar multi-layer structure.

[0028] The planar layer structure of the multi-layer structure simultaneously provides the possibility of dressing an artificial protective layer (artificial SEI) through the application of a solid electrolyte for the optimization of the battery, and is thus suitable for a new cell concept.

[0029] In another configuration of the silicon electrode according to the present invention, the multi-layer structure has an active layer thickness of 10 μm.

[0030] In yet another configuration of the silicon electrode according to the present invention, the multilayer structure has a specific capacity of more than 1500 mAh / g, preferably more than 2000 mAh / g.

[0031] Thus, the active layer in a multilayer construction or in a multilayer structure (both terms are used synonymously) that includes various materials and silicon, or that is in the form of a mixture of silicon and one or more metals, is capable of establishing a specific capacity of more than 1500 mAh / g, preferably more than 2000 mAh / g. With respect to the specific capacity of pure silicon of 3579 mAh / g, the capacity of the Si electrode according to the present invention reaches more than 50%.

[0032] In one configuration of the silicon electrode according to the present invention, the multilayer structure has an areal capacity of 2 mAh / cm 2 ~6 mAh / cm 2 . A larger areal capacity is not practical because manufacturing becomes increasingly costly and inconvenient as the layer thickness increases.

[0033] In one configuration of the silicon electrode according to the present invention, the multilayer structure can be fabricated into a multilayer by alternately depositing separate layers of silicon and at least one metal.

[0034] The advantage of the hierarchical structure over the hybrid system is that each layer in each tier can be varied, and thus a tailored structure with advantageous properties can be created. For example, volume expansion can be controlled by creating a stepped structure where an increased fraction of metal silicide is incorporated in the region near the substrate, while a silicon-rich structure is selected in the region near the surface.

[0035] In another configuration of the silicon electrode according to the present invention, the metal added to the active layer is formed from at least one of the materials titanium (Ti), nickel (Ni), iron (Fe), manganese (Mn), aluminum (Al), tin (Sn), gold (Au) and / or silver (Ag), and / or a mixture of said materials.

[0036] In a further configuration of the silicon electrode according to the present invention, the rapid thermal annealing is flash lamp annealing, and the flash lamp annealing is carried out by a flash lamp having a flash time in the range from 0.2 to 20 ms and an energy density in the range from 0.3 to 160 J / cm 2 and / or by preheating or cooling in the range from 4 °C to 200 °C.

[0037] In another further configuration of the silicon electrode according to the present invention, the rapid thermal annealing is laser annealing, and the laser annealing is carried out by a laser having an annealing time in the range from 0.01 to 100 ms and an energy density in the range from 0.1 to 100 J / cm 2 and / or by preheating or cooling in the range from 4 °C to 200 °C.

[0038] The temperature range from 4 °C to 200 °C shown is the surface temperature of the substrate or layer to be annealed.

[0039] In the deposition of different materials in the active layer, it has been found that the effect of rapid thermal annealing varies. This is due to the wide variety of chemical processes associated with silicon. As a result, other structures, such as the columnar structure in the case of nickel, can be formed in the anode layer to be manufactured. Furthermore, in contrast to Cu silicide, which can hardly intercalate with lithium at all, other silicides that can also intercalate with lithium can be formed. The advantage of utilizing the aforementioned differences is that this enables control of the volume expansion of silicon in the intercalation of lithium. As a result, the stability of the operation of the battery is clearly increased.

[0040] In the case of titanium, a Ti silicide is formed in which Li intercalation may be possible in an appropriate phase (see Xu, J et al., Preparation of TiSi2 Powders with Enhanced Lithium-Ion Storage via Chemical Oven Self-Propagating High-Temperature Synthesis. Nanomaterials 11, 2279 (2021)). This has the advantage that there is no distinct Li active-inactive interface and thus good electrical contact even during cycling. Other metals such as aluminum do not form compounds with silicon, i.e., they do not form silicides. As a result, these metals are mixed in silicon and the electrical conductivity is increased. In the rapid thermal annealing process, the morphology and hardness of the silicon-metal layer can be further improved compared to pure hard silicon.

[0041] The reaction between silicon particles and metal particles promoted by rapid thermal annealing is a non-equilibrium process, which is only achievable in the ms range and thus requires the use of a flash lamp or laser.

[0042] The heating gradient achieved in rapid thermal annealing is within the range of 10 4 ~10 7 K / s required in the process. While flash lamp annealing utilizes the spectrum in the visible light wavelength range for this purpose, laser annealing uses discrete wavelengths in the spectrum from infrared (IR) to ultraviolet (UV).

[0043] The aforementioned reaction is made possible by a defined input of energy by rapid thermal annealing to one or more layers of the particles. Neither does silicon react completely nor does only insufficient active material remain, and a sufficient reaction occurs between the metal and silicon. The more metal there is, the more opportunities for reaction there are, but the less active material there is. The greater the energy, the higher the adhesion, but the less active material there is. The optimal result depends on the materials used and the particle size.

[0044] The present invention will now be described more specifically by using exemplary embodiments.

Brief Description of the Drawings

[0045]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8a

Figure 8b

Figure 9

Modes for Carrying Out the Invention

[0046] The diffusion of metals in silicon and the reaction of silicon with metals are significantly time - dependent and temperature - dependent. At very low temperatures above 200 °C, metal silicides are formed with many metals at the boundary contact between the metal and silicon, where reversible intercalation of lithium is possible, not possible, or only possible to a very small extent. Metals already diffuse at room temperature and diffuse very rapidly at high temperatures, and diffusion is difficult to control in classical furnace treatments. Using the example of copper, the silicon layer has completely reacted after at least 1 second at 600 °C (see Figure 2a).

[0047] Figure 2b shows the influence of rapid thermal annealing 13, especially flash - lamp annealing, on the formation 12 of silicide at the contact point in the layer system of copper 10 and silicon 11. Due to the very short flash pulses in the range from 0.1 to 10 ms, silicon 11 does not fully react with copper 10 to form copper silicide 12. Flash - lamp annealing 13 results in the persistence of pure amorphous or nanocrystalline silicon 11, which is available as an active material for lithium intercalation and at the same time has a sufficient number of inactive regions to ensure stability and good electrical conductivity.

[0048] Figure 3 shows a schematic illustration of a planar Si anode according to the present invention. An adhesion layer 14 is disposed on a copper substrate 10, on which a multi - layer structure 15 as the active layer of the Si anode is applied. Finally, a protective layer 16 or artificial SEI is formed thereon.

[0049] Figure 4 shows the process steps for manufacturing the adhesion layer 14 on the copper substrate 10 for subsequent dressing of the active layer 15 of the Si anode. At the same time, the substrate 10, which serves as a current collector in a LIB: lithium-ion battery, undergoes prior cleaning 17 under vacuum conditions in a plasma atmosphere. This cleaning is necessary because it prevents the reaction between the silicon layer 11 and the copper substrate 10 that will be applied subsequently during flash lamp annealing 13 (FLA), i.e., due to the formation of the oxide layer 18 on the substrate 10 in air, the silicon layer 11 will not adhere to the Cu substrate 10. Subsequently, the first silicon layer 11 is deposited, for example, by sputtering. The first silicon layer 11 reacts with the Cu substrate 10 in the transition region to form copper silicide 12. As a result, the roughness of the substrate 10, for example, a Cu foil, increases, and the silicon layer reacted with copper serves as a kind of bonding layer for dressing further layers. The copper silicide layer 12 is completely inert in the battery. Therefore, in a subsequent step, a diffusion barrier 19, for example, composed of carbon, is first applied. The diffusion barrier 19 is necessary to prevent the reaction of silicon 11 in copper 10 that forms copper silicide 12 during further rapid thermal annealing 13. Subsequently, further Si layers 11, 31 can then be applied successively, and the layers can be stabilized by flash lamp annealing 13 (Figure 5). The advantage of repeating the Si deposition and subsequent flash lamp annealing 13 is that a stable ( "reacted") layer with a completed interface, which acts as an intermediate layer (interface) for subsequent layers, is formed in each sequence. This is advantageous for the adhesion of the Si layer to the copper foil because copper silicide 12 is partially formed, yet active silicon 11 is available. The process described according to the invention thus further results in roughening of the surface, which in turn results in good adhesion to further layers. The growth of the columnar structure is also promoted, thus achieving better ion conductivity and enabling good control of the copper content for subsequent processing. Finally, the protective layer 16 is applied to the multi-layer structure 15.

[0050] By repeating the deposition of silicon 11 and metal 21 and subsequent rapid thermal annealing 13, particularly flash lamp annealing, it is thus possible to control diffusion and silicide formation 30 in one layer, and therefore to establish a concentration gradient of silicide formation perpendicular to the surface.

[0051] The concentration gradient of copper silicide formation 12, 30 can be established by setting the annealing time through the setting of flash lamp energy, flash lamp time or the scanning speed and energy density of the locally heated point by laser, and / or by adjusting the minimum thickness of the silicon layer 11 to be deposited.

[0052] FIG. 6 shows a schematic illustration of the heterogeneous structure of a multi-layer structure 15 formed from a layer formed of silicon 11 and one or more metals 21. As a result of rapid thermal annealing 13, dendrites 23 and nanoparticles 24 are formed in the layer by diffusion and segregation processes, forming a silicide matrix having a large proportion of amorphous silicon 11 that is ideally suitable for mitigating the volume expansion of silicon by lithium intercalation as a high-capacity electrode material. At the same time, the conductive silicide matrix forms a stable scaffold for the dendrites 23, ensuring strong electrical contact with the current collector and thus enabling the continuous operation of the battery. Since the diffusion rate of Cu in Si is much higher than the diffusion rate of Si in Cu: D Cu in Si >>D Si in Cu , it is possible to form a hollow structure. In the thermal equilibrium state, the following approximate formula: D Cu in Si ≒D voids +D Si in Cu applies.

[0053] FIG. 7 shows the influence of the rapid thermal cycle 13 on the hybrid system 22. Depending on the material used for the active layer 15 of the Si anode, the separation process can result in the uniform formation of a heterogeneous layer 25 composed of the scaffold of the conductive dendrite 23 having the amorphous matrix of the active material 11. Due to supersaturation, nanoparticles (nanodroplets) 24 can also be formed by concentration through partial separation of the starting material.

[0054] FIG. 8 shows two variants for manufacturing a planar Si anode according to the invention. The hybrid layer 22 composed of at least one metal and silicon can be manufactured from a sintered powder sputtering target (FIG. 8b), or the hybrid layer 22 is manufactured by co-deposition of the starting materials M1, 27 and M2, 28 from two sources (FIG. 8a), and the hybrid layer 22 is formed to the target thickness of the active layer 15, for example by vapor deposition.

[0055] FIG. 9 shows means for providing a concentration gradient of layers in a deposited multi-layer structure composed of a partially reacted layer / hierarchy 30. The concentration gradients of the silicide / silicon concentrations 12, 11 in the multi-layer structure 15 can be established, firstly, by the selected processing parameters of the rapid thermal annealing process 13, and secondly, by the thickness of the deposited metal layer or the ratio between Si11 and metal 21 in the deposited layer 31. For example, the greater the selected energy input by a flash lamp or laser 13, the greater the amount of metal atoms that can diffuse into the silicon layer 11 during the rapid thermal annealing process, i.e., the smaller the concentration gradient of the silicide / silicon concentration in the layer (see the right sub-picture in FIG. 9). A small concentration gradient means that the concentration of silicide in the anode layer 31 or in the active layer 15 gradually decreases from the side of the layer / active layer 31 facing the collector 10 to the side of the layer / active layer facing away from the collector. A large concentration gradient means a sharp decrease in the silicide concentration. A high concentration of silicide is formed at the bottom of the layer 31, which rapidly decreases, and only silicon 11 is present at the top, i.e., on the side of the layer / active layer 31 facing away from the collector 10. While pure silicon 11 is available for lithium intercalation, the formation of silicide 12 increases the electrical conductivity.

[0056] For example, the concentration gradient of the copper concentration in a silicon layer having a copper layer is established by adjusting the pulse time, the preheating or cooling of the layer structure, and the layer thickness of the deposited layer, i.e., by adjusting the energy input (with respect to time and temperature) and the thickness ratio of the silicon layer to the copper layer, such that the average reaction depth (diffusion distance) is smaller than the layer thickness of the silicon layer for the purpose of supplying sufficient unreacted silicon for lithium intercalation.

[0057] The silicon electrode according to the invention as an anode in a lithium-ion battery thus has the following overall structure.

[0058] Si30, which is partially reacted with Cu, exists on the copper current collector 10 (conductor), and on top of that, an active layer in the multilayer structure 15, in the form of a mixed system 22 containing various materials (metals and silicon) or at least one metal and silicon, is deposited and has a specific capacity exceeding 1500 mAh / g, preferably greater than 2000 mAh / g. A further layer composed of silicon or a mixed system, and / or a protective layer, or optionally, a boundary layer through the coating of a solid electrolyte, is deposited on the multilayer structure 15, and the layer has a planar surface. This structure realizes a thickness of the active layer of the anode active material of 10 μm, thereby enabling an areal capacity of 4 mAh / cm² at a specific total capacity of 2000 mAh / g. This layer structure enables excellent lithium diffusion and high electrical conductivity, and is suitable for the operation of the battery without pulverizing the active layer 15. 2 This enables an areal capacity of 4 mAh / cm². This layer structure enables excellent lithium diffusion and high electrical conductivity, and is suitable for the operation of the battery without pulverizing the active layer 15.

[0059] A further advantage of the anode according to the present invention is a high charging rate exceeding 1C without any associated decrease in capacity. Due to the inhomogeneous formation of the silicide scaffold, the active layer 15 of the anode has an electrical conductivity of up to 5×10⁻³ S / cm, which is increased by up to 100 times compared to graphite. The low resistance means that less waste heat is generated during charging / discharging, and a smaller overall cell design with less cooling is possible. 4 The low resistance means that less waste heat is generated during charging / discharging, and a smaller overall cell design with less cooling is possible.

[0060] The planar surface minimizes the need for SEI enhancement, and only a minimal amount of additives are required for SEI control. This also results in low electrolyte consumption and high durability of the anode constructed in this way.

Explanation of Reference Numerals

[0061] 1 Lithium-ion battery 2 Anode-side current collector 3 SEI (Solid Electrolyte Interface) 4 Electrolyte 5 Separator 6 Conductive intermediate phase 7 Cathode, positive electrode 8 Cathode current collector 9 Anode, negative electrode 10 Copper substrate 11 Silicon 12 Copper silicide, metal silicide 13 Rapid thermal annealing, e.g., flash lamp annealing 14 Adhesion layer 15 Multilayer structure 16 Protective layer or SEI 17 Pre - cleaning by plasma 18 Oxide layer 19 Diffusion barrier 20 Repeated deposition of layers 21 Further metal layer, e.g., Cu or Al 22 Mixed layer 23 Dendrite 24 Nanoparticles, nanodroplets 25 Heterogeneous layer 26 Sputtering source 27 Material 1 28 Material 2 29 Mixed target composed of M1 + M2 30 Partially reacted layer (e.g., Cu / CuSi x / Si) 31 Deposition layer in the active layer

Claims

1. 1. A silicon electrode designed and intended for use as an anode in a lithium-ion battery, comprising: a current collector (10) made of copper; an adhesion layer (14) disposed on the current collector (10); and a multi-layered structure (15) disposed on the adhesion layer (14), wherein the multi-layered structure (15) as an active layer of the silicon electrode is formed from at least one layer (31) composed of a metal (21) and silicon (11) or from a mixed system (22) consisting of silicon (11) mixed with at least one metal (21); and wherein the adhesion layer (14) and the multi-layered structure (15) are subjected to rapid thermal annealing (13), and the multi-layered structure (15) forms a conductive metal silicide matrix, the metal silicide matrix surrounding amorphous nanocrystalline regions of the silicon (11).

2. 2. A silicon electrode designed and intended for use as an anode in a lithium ion battery according to claim 1, characterized in that the adhesion layer (14) is formed from at least one of the following materials: titanium, Ti, silicon, Si, chromium, Cr, tantalum, Ta, and / or tungsten, W.

3. 2. A silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1, characterized in that on the multi-layer structure (15) a further layer composed of the silicon (11) or the mixed system (22) and / or a protective layer (16) with a planar surface is arranged.

4. 2. A silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1, characterized in that an interface layer and / or a solid electrolyte is disposed on the planar surface of the multi-layer structure (15).

5. 2. A silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1, characterized in that the multi-layer structure (15) as an active layer has an active layer thickness of 10 μm.

6. 2. A silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1, characterized in that the multi-layer structure (15) has a specific capacity of more than 2000 mAh / g.

7. The multi-layer structure (15) has a current density of 2 mAh / cm ２ ~6mAh / cm ２ 2. A silicon electrode designed and intended for use as an anode in a lithium ion battery according to claim 1, characterized in that it has an areal capacity of

8. 2. A silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1, characterized in that the multi-layer structure (15) as the active layer of the electrode can be fabricated into multiple layers by alternately depositing distinct layers (31) of the silicon (11) and of the at least one metal (21).

9. 2. A silicon electrode designed and intended for use as an anode in a lithium ion battery according to claim 1, characterized in that the metal (21) added to the active layer is formed from at least one of the following materials: manganese, Mn, iron, Fe, titanium, Ti, nickel, Ni, aluminum, Al, tin, Sn, gold, Au and / or silver, Ag, and / or a mixture of said materials.

10. The rapid thermal anneal (13) is a flash lamp anneal, with a flash time ranging from 0.2 to 20 ms and a power of 0.3 to 160 J / cm ２ 10. A silicon electrode designed and intended for use as an anode in a lithium ion battery according to claim 1, characterized in that it can be carried out by a flash lamp having an energy density ranging from 0.1 to 100°C and / or by preheating or cooling in the range from 4°C to 200°C.

11. The rapid thermal annealing (13) is a laser annealing, and the annealing time ranges from 0.01 to 100 ms and the radiation energy ranges from 0.1 to 100 J / cm through setting the scanning speed of the local heating point. ２ 10. A silicon electrode designed and intended for use as an anode in a lithium ion battery according to claim 1, characterized in that the laser irradiation can be carried out by a laser having an energy density ranging from 0.1 to 100°C and / or by preheating or cooling ranging from 4°C to 200°C.

12. A lithium ion cell comprising a silicon electrode according to any one of claims 1 to 11.

13. A lithium ion battery comprising at least one battery cell according to claim 12.

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