Flat silicon anode on a copper conductor for lithium ion batteries

Abstract

The 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 arranged on the current collector, and a multi-layer structure arranged on the adhesive layer. The object of providing an Si electrode, which is not pulverised when lithium is incorporated and therefore does not lose the electrical contact with the current collector as a result, as well as having a stable surface and high intrinsic conductivity, is achieved in that the multi-layer structure, as an active layer of the Si electrode, is formed by at least one layer made of a metal and silicon or formed by a mixed system consisting of silicon mixed with at least one metal, wherein the multi-layer structure undergoes rapid tempering and forms a conductive metal silicide matrix, wherein the metal silicide matrix contains amorphous, nanocrystalline regions of the silicon.

Description

[0001] Planar silicon anode on a copper conductor for lithium-ion batteries

[0002] The 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 arranged on the current collector and a multilayer structure arranged on the adhesive layer.

[0003] The invention also relates to a battery cell which comprises the silicon electrode according to the invention and to a battery which comprises at least one battery cell.

[0004] Electrochemical energy storage is a key pillar of the globally desired energy transition, which requires the temporary storage of fluctuating electricity generated from renewable sources and the provision of it for stationary and mobile applications. Rapid developments in electromobility and mobile communications devices are also driving up the demand for high storage capacities and high charging rates in energy storage systems. This is where established technologies are reaching their limits. In order to counteract raw material shortages and the resulting increase in costs, particularly for secondary batteries, new materials are needed alongside the diversification of energy storage concepts. These materials should improve the technical performance of such energy storage concepts (e.g. capacity, energy density and service life) and also minimize manufacturing costs.The latter can be ensured in particular by the use of readily available chemical elements such as silicon, for which a broad technological base already exists.

[0005] Batteries are electrochemical energy storage devices and are divided into primary and secondary batteries.

[0006] Primary batteries are electrochemical power sources in which chemical energy is irreversibly converted into electrical energy. A primary battery is therefore not rechargeable. Secondary batteries, also called accumulators, on the other hand, are rechargeable electrochemical energy storage devices in which the chemical reaction is reversible, allowing multiple uses. Electrical energy is converted into chemical energy during charging, and from chemical energy into electrical energy during discharging.

[0007] Battery is the generic term for interconnected cells. Cells are galvanic units consisting of two electrodes, an electrolyte, a separator, and a cell casing. Figure 1 shows an example of the structure and function of a lithium-ion cell during the discharge process. The components of a cell are briefly explained below.

[0008] Each Li-ion cell consists of two different electrodes 7, 9, one which is negatively charged when charged and one which is positively charged when charged. Since ions migrate from the negatively charged electrode to the positively charged electrode during energy release, i.e. during discharge, the positively charged electrode is called the cathode 7 and the negatively charged electrode the anode 9. The electrodes each consist of a current conductor 2, 8 (also called a collector) and an active material applied to it. Between the electrodes there is the ion-conducting electrolyte 4, which enables the necessary charge exchange, and the separator 5, which ensures the electrical separation of the electrodes.

[0009] The cathode, for example, consists of mixed oxides applied to an aluminum collector. Transition metal oxides with cobalt (Co), manganese (Mn), and nickel (Ni), or aluminum oxide (Al2O3) are the most common compounds. The applied metal oxide layer serves to store the lithium ions during the cell discharge.

[0010] The anode of a Li-ion cell can consist of a copper foil as the collector and a layer of carbon as the active material. Natural or synthetic graphite is typically used as the carbon compound because it has a low electrode potential and exhibits low volume expansion during charging and discharging. During the charging process, lithium ions are reduced and incorporated into the graphite layers.

[0011] In lithium-ion battery designs, the cathode typically supplies the lithium atoms for charging and discharging in the anode, so the battery capacity is limited by the cathode capacity. As already mentioned, typical cathode materials used to date include, for example,

[0012] Li (Ni, Co, Mn) O2 and LiFePO.}. Due to the lithium metal oxide structure of the cathode, an increase in capacity is only possible to a limited extent.

[0013] It is also known to use silicon instead of carbon for lithium battery anodes. Silicon is a semiconductor with poor conductivity, is very hard and 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 with a storage capacity of 372 mAh / g. Compared to pure metallic lithium, silicon has significantly reduced reactivity and prevents the formation of dendrite structures, especially at high surface currents. Dendrites are tree- or bush-like crystal structures that can pierce the separator, causing short circuits in the battery and thus rapid cell death.However, challenges arise when using silicon as an anode material due to the sometimes significant volume changes (volume contraction and expansion) of the host matrix during the incorporation and removal of mobile ion species during charging and discharging of corresponding energy storage devices. Lithium incorporation results in Li through alloying with lithium. 15Si4 can experience a volume expansion of up to 400%. The volume change for graphite is approximately 10%. The volume change of the anode material when using silicon leads to internal stresses, cracking, pulverization of the active material of the host matrix (silicon), and ultimately to the complete destruction of the anode. The brittle Si layer crumbles and loses electrical contact with the conductive current collector, resulting in the loss of active material. At the same time, the surface of the Si anode is constantly breaking up, requiring the continuous buildup of a solid electrolyte interphase (SEI) with simultaneous degradation of the electrolyte.

[0014] To date, nanostructures of up to 100 nm for crystalline silicon and up to 1 pm for amorphous silicon are considered suitable for homogeneous volume expansion. This allows the stress of volume expansion to be compensated without causing surface disruption. However, this thickness is far from sufficient to compete with the storage capacity of current lithium-ion batteries; for this, structures of at least 5 pm of pure silicon are necessary, which corresponds to an ideal capacity of 3.5 mAh / cm 2 .

[0015] Previous research in the field of lithium-ion batteries has focused on the development of silicon nanostructures to prevent the silicon used from pulverizing, with the emphasis being on ensuring continuous electrical contact with the current collector during volume expansion during battery operation. It is known that for pure silicon, only the use of nanowires was possible. For powder- or particle-based silicon, a correspondingly conductive adhesive or binder is required to ensure electrical contact. Silicon powders are currently provided with binders and applied to the current collector in a slurry process. The volume expansion of the silicon that nevertheless occurs when lithium is incorporated has so far restricted its use to less than 20% vol silicon in the slurries.Slurries are mixtures of solids in which the solids are dispersed in a liquid. In slurry-based processes, a layer of silicon particles with a carbon-containing binder is applied or calendered onto a current collector. The binder ensures adhesion and electrical contact between the particles and to the current collector. Enormous effort has been expended to date to produce macroscopic quantities of silicon with nanoporous structures. The conductivity of the structures is limited to the conductivity of the binder. The porous structures have a large surface area and thus tend to form an immense Solid Electrolyte Interface (SEI).

[0016] In summary, the silicon-based anodes developed so far have the following problems: high volume expansion when lithium is incorporated, the resulting pulverization of the material and loss of electrical contact with the current collector, an unstable surface of the anode and poor intrinsic conductivity.

[0017] It is therefore the object of the present invention to provide a silicon electrode which is suitable for use as an anode in a lithium-ion battery and which does not have the problems summarized above.

[0018] The object is achieved by a silicon electrode according to independent claim 1.

[0019] The silicon electrode according to the invention, which is designed and intended for use as an anode in a lithium-ion battery, comprises a current collector, preferably made of copper, an adhesive layer arranged on the current collector and a multilayer structure arranged on the adhesive layer, wherein the multilayer structure is formed as the active layer of the Si electrode from at least one layer of a metal and silicon or from a mixed system which consists of silicon admixed with at least one metal, wherein the multilayer structure is subjected to a short-time annealing and forms a conductive metal-silicide matrix, wherein the metal-silicide

[0020] Matrix includes amorphous, nanocrystalline regions of silicon.

[0021] In one embodiment of the Si electrode according to the invention, the adhesive layer is formed from one or more of the materials titanium (Ti), silicon (Si), chromium (Cr), tantalum (Ta) and / or tungsten (W).

[0022] The adhesion layer guarantees extremely stable contact between the anode's active layer and the anode's current collector, both through mechanical fixation using a roughened surface and through a (partial) reaction with the substrate (chemisorption). Suitable adhesion layers consist of titanium or chromium as adhesion promoters; with suitable diffusion barriers such as tungsten or carbon, silicon itself can also be used as an adhesion layer.

[0023] The short-term annealing with a controllable and defined energy input into a silicon layer of the multilayer structure causes a partial reaction of the silicon with the copper current collector and the formation of a roughened surface, creating an extremely strong adhesion between the multilayer structure and the current collector, which does not weaken during battery operation.

[0024] The multilayer structure as the active layer of the Si electrode is formed from at least one layer. One layer comprises a deposited layer of active material which is capable of integrating lithium, and one or more layers of metal. Depending on the target capacity, the layer thickness of the active layer, i.e. the composite of active material and metal, of the electrode can be made up of one or more layers. The at least one layer can be formed from at least one metal and silicon. The silicon and the at least one metal are applied alternately by separate layer deposition of the materials. One layer is thus formed from at least one layer of at least one metal and one layer of silicon, with several layers being formed in the multilayer structure to achieve the target thickness of the anode (Fig. 5).The at least one layer can also be formed by a mixed system, wherein the mixed system of silicon is mixed with at least one metal (Fig. 6). This homogeneous mixture of at least one metal and silicon can be produced from a sputtering target made of sintered powder (Fig. 8b) or it is deposited by co-deposition (Fig. 8a) of the starting materials to form a mixed layer. The layer thickness for silicon is between 500 and 1000 nm, for metal the layer thickness is between 10 and 100 nm. Thus, a multilayer structure of the active layer with a total thickness of 5 pm can consist of up to 20 individual layers.

[0025] When lithium is incorporated, the volume expands; however, the silicon layer is not pulverized due to the addition of metals and the use of the multilayer structure. The addition of metals leads to the formation of an alloy with reduced hardness compared to pure silicon. At the same time, the silicon has a very high electrical conductivity compared to graphite. Despite the addition of metals, a specific total capacity of over 2000 mAh / g is guaranteed. The stability and high electrical conductivity of the silicon electrode according to the invention is supported by the formation of a heterogeneous structure with the formation of a conductive matrix of metals or metal silicides that envelop the amorphous regions of the silicon.

[0026] In one embodiment of the silicon electrode according to the invention, a further layer of silicon or the mixed system and / or a protective layer is arranged on the multilayer structure, which forms a planar surface.

[0027] The deposition technology used for the multilayer structure, for example, sputtering, creates a planar surface. A layer of silicon, or a mixed system of silicon and one or more metals, can be deposited on this surface to a desired thickness and / or a protective layer. The planar layer structure has only a small surface area, which does not change during battery operation.

[0028] This limits the build-up of SEI and the loss of electrolyte to an absolute minimum.

[0029] In a further embodiment of the silicon electrode according to the invention, a boundary layer and / or a solid electrolyte is therefore arranged on the planar multilayer structure.

[0030] The planar layer structure of the multilayer structure also offers the possibility of building up an artificial protective layer (artificial SEI) up to the application of a solid electrolyte for battery optimization and is therefore suitable for new cell concepts.

[0031] In another embodiment of the silicon electrode according to the invention, the multilayer structure has an active layer thickness of 10 pm.

[0032] In a further embodiment of the silicon electrode according to the invention, the multilayer structure has a specific capacity of >1500mAh / g, preferably >2000mAh / g.

[0033] This allows a specific capacity of over 1500 mAh / g, preferably over 2000 mAh / g, to be achieved with the active layer in a multilayer structure (both terms are used synonymously) with various materials and silicon, or in the form of a mixed system of silicon and one or more metals. In relation to the specific capacity of pure silicon of 3579 mAh / g, the capacity of the Si electrode according to the invention reaches more than 50%.

[0034] In one embodiment of the silicon electrode according to the invention, the multilayer structure has a surface capacity of 2mAh / cm 2 up to 6mAh / cm 2 Larger surface capacities are not advisable, since the manufacturing effort increases with increasing layer thickness.

[0035] In one embodiment of the silicon electrode according to the invention, the multilayer structure can be produced by separate layer deposition of the silicon and the at least one metal alternately in multilayers.

[0036] The advantage of a layered structure compared to a mixed system is that each layer can be varied in each layer, thus creating a customized structure with advantageous properties. For example, to control volume expansion, a gradual structure can be created in which an increased metal silicide content is added in the area close to the substrate, whereas in the area close to the surface

[0037] A silicon-rich structure can be chosen in this area.

[0038] In another embodiment of the silicon electrode according to the invention, the metal provided in 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 these materials.

[0039] In a further embodiment of the silicon electrode according to the invention, the short-time tempering is a flash lamp tempering, which is carried out by means of a flash lamp with a flash duration in the range of 0.2 to 20 ms and an energy density in the range of 0.3 to 160 J / cm 2 and / or preheating or cooling in the range of 4°C to 200°C.

[0040] In another further embodiment of the silicon electrode according to the invention, the short-time annealing is a laser annealing, which is carried out by means of a laser with an annealing time in the range of 0.01 to 100 ms by setting a scanning speed of a local heating point and an energy density in the range of 0.1 to 100 J / cm 2 and / or with preheating or cooling in the range of 4°C to 200°C.

[0041] The temperature range from 4°C to 200°C refers to the surface temperature of the substrate or the layer to be tempered.

[0042] It has been shown that the effect of short-term annealing differs when depositing different materials in the active layer. This is thought to be due to the various chemical processes associated with silicon. This can lead to the formation of different structures in the resulting anode layer, e.g., columnar structures in nickel. Furthermore, other silicides can form which, unlike copper silicides, can store no or negligible lithium, also store lithium. Exploiting these differences has the advantage of controlling the volume expansion of silicon during lithium storage. This significantly increases the stability of battery operation.

[0043] In the case of titanium, Ti silicide is formed, which can be capable of storing Li in the right 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 clear Li-active-inactive interface, thus ensuring good electrical contact even during cycling. Other metals such as aluminum do not form compounds with silicon, and therefore no silicides. As a result, these metals mix with silicon, increasing electrical conductivity. In the short-term annealing step, the morphology and hardness of the silicon-metal layer can also be improved compared to hard pure silicon.

[0044] The reactions between the silicon particles and the metal particles forced by the short-term annealing are non-equilibrium processes that can only be realized in the ms range and thus require the use of a flash lamp or a laser.

[0045] The heating ramps achieved in the short-time tempering are in the range of 10 4 - 10 7 K / s . Flash lamp annealing uses a spectrum in the visible wavelength range, whereas laser annealing uses discrete wavelengths in the infrared (IR) to ultraviolet (UV) spectrum.

[0046] The aforementioned reaction is enabled by the defined energy input through short-term annealing into one or more layers of particles. This results in a sufficient reaction between metal and silicon without the silicon reacting completely or leaving insufficient active material. More metal means more reaction possibilities but less active material. More energy means more adhesion but less active material. The optimal result depends on the materials used and the particle size.

[0047] The invention will be explained in more detail below using exemplary embodiments.

[0048] The drawings show

[0049] Fig. 1 Example structure and function of a lithium ion cell during the discharge process;

[0050] Fig. 2 Influence of a temperature input on the silicide formation in a silicon anode a) in a conventional furnace process (state of the art) b) with short-time annealing, in particular flash lamp annealing;

[0051] Fig. 3 Schematic representation of the planar Si anode according to the invention; Fig. 4 Schematic representation of the process for producing an adhesion layer made of silicon;

[0052] Fig. 5 Schematic representation of a process for producing a multilayer structure of silicon and metal;

[0053] Fig. 6 Schematic representation of a heterogeneous multilayer structure according to a variant of the Si electrode according to the invention;

[0054] Fig. 7 Schematic representation of a multilayer structure formed from a mixed system according to a further variant of the Si electrode according to the invention;

[0055] Fig. 8 Possible manufacturing variants of the Si electrode according to the invention a) co-deposition of different materials, b) deposition from a mixed target;

[0056] Fig. 9 Schematic representation of a process for producing a gradient mixing system.

[0057] The diffusion of metals into silicon, as well as the reaction of silicon with metals, is highly dependent on time and temperature. Even at temperatures as low as 200°C, many metals form a metal silicide at the interface between metal and silicon. This metal silicide has little to no reversible lithium intercalation capacity, or only a very low one. The diffusion of metals occurs very rapidly, even at room temperature and at elevated temperatures, and is difficult to control in conventional furnace processes. For example, with copper, a complete layer of silicon is completely reacted after 1 second at 600°C (see Fig. 2a).

[0058] Figure 2b) shows the influence of short-term annealing 13, in particular flash lamp annealing, on the silicide formation 12 at the contact point in a layer system of copper 10 and silicon 11. Due to the very short flash pulse in the range of 0.1 to 10 ms, the silicon 11 does not completely react with the copper 10 to form copper silicide 12. The flash lamp annealing 13 leaves pure amorphous or nanocrystalline silicon 11, which is available as an active material for lithium incorporation, while at the same time providing a sufficient number of inactive regions to ensure stability and good electrical conductivity.

[0059] Figure 3 shows a schematic representation of the planar Si anode according to the invention. An adhesive layer 14 is arranged on a copper substrate 10, onto which the multilayer structure 15 is applied as the active layer of the Si anode. Finally, a protective layer 16, or artificial SEI, is formed thereon.

[0060] Figure 4 shows method steps for producing an adhesion layer 14 on the copper substrate 10 for the subsequent buildup of the active layer 15 of the Si anode. A substrate 10, which simultaneously serves as a current collector in a LIB (lithium-ion battery), undergoes pre-cleaning 17 under vacuum conditions in a plasma atmosphere. This cleaning is necessary because an oxidation layer 18 forms on the substrate 10 in air, which would prevent a reaction between a subsequently applied silicon layer 11 and the copper substrate 10 during flash lamp annealing 13 (FLA - flash lamp annealing), and the silicon layer 11 would therefore not adhere to the Cu substrate 10. A first silicon layer 11 is then deposited, e.g., by sputtering. This first silicon layer 11 reacts with the Cu substrate 10 in a transition region to form copper silicide 12, thereby reducing the roughness of the substrate 10, e.g.a Cu foil, and the silicon layer that has reacted with the copper serves as a type of adhesive layer for the further layer buildup. The copper silicide layer 12 is completely inactive in a battery, so that in a subsequent step, a diffusion barrier 19, e.g. made of carbon, is first applied. This diffusion barrier 19 is necessary to prevent the reaction of silicon 11 in copper 10 to form copper silicide 12 during a further short-term annealing 13. Subsequently, further Si layers 11, 31 can be applied sequentially, whereby the layers can be stabilized by a flash lamp annealing 13 (Figure 5). The advantage of repeated Si deposition and subsequent flash lamp annealing 13 is that with each sequence, a stable ("reacted") layer with a closed boundary surface is formed, which acts as an interface for the subsequent layers.This is advantageous for the adhesion of the Si layer to copper foil, since copper silicide 12 is partially formed and active silicon 11 is still available. The described inventive method thus additionally roughens the surface, resulting in good adhesion for further layers. The growth of columnar structures is also promoted, so that better ionic conductivity is achieved and the copper content can be well controlled for subsequent processes. Finally, a protective layer 16 is applied to the multilayer structure 15. After repeated deposition of silicon 11, metal 21 and subsequent short-term annealing 13, in particular flash lamp annealing, the diffusion and silicide formation 30 in a layer can be controlled, so that a gradual course of silicide formation perpendicular to the surface can be established.

[0061] The copper silicide formation 12, 30 can be gradually adjusted by adjusting the flash lamp energy, the flash lamp duration or the annealing time, by adjusting a scanning speed of a local heating point and an energy density by means of a laser and / or by minimal thickness adjustment of the deposited silicon layer 11.

[0062] Figure 6 shows a schematic representation of a heterogeneous multilayer structure 15, which is formed from layers made of silicon 11 and one or more metals 21. Due to the short-term annealing 13, dendrites 23 and nanoparticles 24 form in the layers due to diffusion and segregation processes. These nanoparticles form a silicide matrix with large proportions of amorphous silicon 11, which, as a high-capacity electrode material, is ideally suited to absorb the volume expansion of silicon due to lithium incorporation. At the same time, the conductive silicide matrix forms a stable framework of dendrites 23 to ensure solid electrical contact with the current collector and thus enable continuous battery operation. Cavity structures can form because the diffusion rate of Cu in Si is significantly higher than that of Si in Cu; D Cu in s± >> D si in Cu- In thermal equilibrium, approximately: D Cu in si ~ D VO ids + D si in Cu Figure 7 shows the influence of short-term annealing 13 on a mixed system 22. Depending on the material used for the active layer 15 of the Si anode, a heterogeneous layer 25 consisting of a framework of conductive dendrites 23 with an amorphous matrix of the active material 11 can form uniformly through separation processes. Due to supersaturation, nanoparticles (nanodroplets) 24 can also form through condensation due to the partial separation of the starting materials.

[0063] Figure 8 shows two variants for producing the planar Si anode according to the invention. A mixed layer 22 of at least one metal and silicon can be produced from a sputtering target made of sintered powder (Fig. 8b), or the mixed layer 22 can be produced to the target thickness of the active layer 15 by co-deposition (Fig. 8a) of the starting materials M1 27 and M2 28 from two sources to form a mixed layer 22, for example by evaporation.

[0064] Figure 9 shows the possibility of producing a layer gradient in a deposited multilayer structure from partially reacted layers / layers 30. The gradual progression of the silicide / silicon concentration 12, 11 in the multilayer structure 15 can be adjusted, on the one hand, by the selected process parameters of the short-time annealing process 13, and, on the other hand, by the thickness of the deposited metal layers or the ratio between Si 11 and metal 21 in a deposited layer 31. The higher the energy input, e.g., by the flash lamp or the laser 13, the more metal atoms can diffuse into the silicon layer 11 during the short-time annealing process, i.e., the lower the gradient of the silicide / silicon concentration in the layer (cf. Fig. 9, right-hand part of the image). A small gradient means that the concentration of silicide in a layer 31 orin the active layer 15 of the anode, the silicide concentration gradually decreases from the side of the layer / active layer 31 facing the current collector 10 to the side of the layer / active layer facing away from the current collector. A high gradient means that the silicide concentration decreases rapidly. A high silicide concentration forms on the underside of the layer 31, which decreases rapidly, leaving only silicon 11 on the top side, i.e., the side of the layer / active layer 31 facing away from the current collector 10. The pure silicon 11 is available for the incorporation of lithium, whereas the formation of silicide 12 increases the electrical conductivity.

[0065] The gradual progression of, for example, the copper concentration in a silicon layer with a copper layer is adjusted by adjusting the pulse duration, the preheating or cooling of the layer structure and the layer thickness of the deposited layers, i.e. by adjusting the energy input (over time and temperature) and the thickness ratio of the silicon layer to the copper layer, whereby the average reaction depth e (diffusion length) should be smaller than the layer thickness of the silicon layer in order to provide sufficient unreacted silicon for the lithium intercalation.

[0066] The overall structure of the silicon electrode according to the invention as an anode in a lithium-ion battery is therefore as follows:

[0067] On a copper current collector 10 (current conductor) there is partially reacted Si 30 with Cu as an adhesive layer 14, on which the active layer has been deposited in a multilayer structure 15 with various materials (metals and silicon) or as a mixed system 22 of at least one metal and silicon, and has a specific capacity of over 1500 mAh / g, preferably greater than 2000 mAh / g. A further layer of silicon or the mixed system and / or a protective layer or optionally a boundary layer up to a structure of a solid electrolyte is deposited on this multilayer structure 15, which has a planar surface. With this structure, an active layer thickness of the active material of the anode of 10 μm is achieved, which, with a specific total capacity of 2000 mAh / g, results in a surface capacity of 4 mAh / cm 2This layer structure enables excellent lithium diffusion as well as high electrical conductivity and is suitable for battery operation without the active layer 15 becoming powdered.

[0068] Further advantages of the anode according to the invention are the high charging rates of more than IC without any significant loss of capacity. The active layer 15 of the anode has an electrical conductivity that is up to 100 times higher than that of graphite, up to 5* 10 4 S / cm due to the heterogeneous formation of a silicide framework. The low resistance results in less waste heat during charging / discharging, allowing for a more compact design of the overall cell with less cooling.

[0069] The planar surface limits the buildup of SEI to an absolute minimum, and only minimal amounts of additives are required for SEI control. This also results in low electrolyte consumption and a long service life for anodes constructed in this way. Planar silicon anode on a copper conductor for lithium-ion batteries.

[0070] List of reference symbols

[0071] Lithium-ion battery Collector on anode side SEI -Solid-Electrolyte- Interphase Electrolyte Separator Conductive interphase Cathode, positive electrode Collector on cathode side Anode, negative electrode Copper substrat Silicon Copper silicide, metal silicide

[0072] Short-term annealing, e.g. flash lamp annealing Adhesive layer Multilayer structure Protective layer or SEI Plasma pre-cleaning Oxidation layer Diffusion barrier

[0073] Repeated layer deposition additional metal layer, e.g. Cu or Al mixed layer dendrite nanoparticles, nano droplets heterogeneous layer sputter source material 1 material 2 mixed target of M1+M2 partially reacted layer (e.g. Cu / CuSi x / Si) deposited layer in the active layer

Claims

Planar silicon anode on a copper conductor for lithium-ion batteries Claims A silicon electrode designed and intended for use as an anode in a lithium-ion battery comprising a current collector (10), preferably made of copper, an adhesive layer (14) arranged on the current collector (10) and a multilayer structure (15) arranged on the adhesive layer (14), characterized in that the multilayer structure (15) as the active layer of the Si electrode is formed from at least one layer (31) of a metal (21) and silicon (11) or from a mixed system (22) which consists of silicon (11) doped with at least one metal (21), wherein the adhesive layer (14) and the multilayer structure (15) are subjected to short-term annealing (13) and the multilayer structure (15) forms a conductive metal-silicide matrix, wherein the metal-silicide matrix includes amorphous, nanocrystalline regions of the silicon (11).The silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1, characterized in that the adhesive layer (14) is formed from at least one of the materials titanium, Ti, silicon, Si, chromium, Cr, tantalum, Ta, and / or tungsten, W. The silicon electrode designed and intended for use as an anode in a lithium-ion battery according to claim 1. Claim 1, characterized in that a further layer of silicon (11) or the mixing system (22) and / or a protective layer (16) having a planar surface is arranged on the multilayer structure (15).

4. The silicon electrode designed and intended for use as an anode in a lithium-ion battery according to one of the preceding claims, characterized in that a boundary layer and / or a solid electrolyte is arranged on the planar surface of the multilayer structure (15).

5. The silicon electrode designed and intended for use as an anode in a lithium-ion battery according to one of the preceding claims, characterized in that the multilayer structure (15) has an active layer thickness of 10 pm as the active layer.

6. The silicon electrode designed and intended for use as an anode in a lithium-ion battery according to one of the preceding claims, characterized in that the multilayer structure (15) has a specific capacity of > 1500mAh / g, preferably >2000mAh / g.

7. The silicon electrode designed and intended for use as an anode in a lithium-ion battery according to one of the preceding claims, characterized in that the multilayer structure (15) has an area capacity of 2 mAh / cm² 2 up to 6mAh / cm 2 The silicon electrode is designed and intended for use as an anode in a lithium-ion battery according to any one of the preceding claims, characterized in that the multilayer structure (10) as the active layer of the electrode can be produced by separate layer deposition (31) of silicon (11) and the at least one metal (21) alternately in multilayers. The silicon electrode is designed and intended for use as an anode in a lithium-ion battery according to any one of the preceding claims, characterized in that the metal (21) provided in the active layer is formed from at least one of the materials manganese, Mn, iron, Fe, titanium, Ti, nickel, Ni, aluminum, Al, tin, Sn, gold, Au, and / or silver, Ag, and / or a mixture of these materials.The silicon electrode is designed and intended for use as an anode in a lithium-ion battery according to one of the preceding claims, characterized in that the short-term annealing (13) is a flash lamp annealing and is carried out by means of a flash lamp with a flash duration in the range of 0.2 to 20ms and an energy density in the range of 0.3 to 160J / cm. 2 and / or preheating or cooling in the range of 4°C to 200°C is possible. The silicon electrode is designed and intended for use as an anode in a lithium-ion battery according to one of the preceding claims, characterized in that the short-term annealing (13) is a laser annealing process and is carried out by means of a laser with an annealing time in the range of 0.01 to 100 ms by setting a scan speed of a local heating point and an energy density in the range of 0.1 to 100 J / cm² 2and / or is feasible with preheating or cooling in the range of 4°C to 200°C.

12. Battery cell, in particular a lithium-ion cell, comprising a silicon electrode according to any one of claims 1 to 11.

13. Battery, in particular a lithium-ion battery, comprising at least one battery cell according to claim 12.

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