METHOD FOR PRODUCING A SILICON ELECTRODE AS AN ANODE FOR A LITHIUM BATTERY

Description

[0001] The invention relates to a method for producing a silicon electrode as an anode for a lithium battery.

[0002] Batteries are electrochemical energy storage devices and are divided into primary and secondary batteries; general principles and essential characteristics of lithium (Li)-ion batteries have been summarized in a compendium published by the Association of German Engineers (VDE), from which some basic information has been taken (see https: / / www.dke.de / resource / blob / 933404 / dd44d15918ce4d4aefc3 63a4ef1490e1 / kompendium-li-io-batterien-2021-de-data.pdf - 2022-01-20).

[0003] 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 for multiple uses. Electrical energy is converted into chemical energy during charging, and back again during discharging.

[0004] A complete, continuous charge and discharge cycle is referred to as a cycle. The lifespan of a battery is linked to the number of cycles. Depending on the type, application, and handling, the lifespan of rechargeable batteries varies. Lithium-ion batteries are robust, have a high cycle stability, and a high energy density.

[0005] Battery is the generic term for interconnected cells. Cells are galvanic units consisting of two electrodes, electrolyte, separator, and cell casing. Figure 1 This 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.

[0006] Each lithium-ion cell consists of two different electrodes 7, 9: a negatively charged electrode 9 and a positively charged electrode 7. 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. Each electrode comprises a current collector 2, 8 and an active material applied to it. Between the electrodes are the ion-conducting electrolyte 4, which enables the necessary charge exchange, and the separator 5, which ensures the electrical separation of the electrodes.

[0007] The anode of a lithium-ion cell can consist of a copper foil and a layer of carbon. 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 charging, lithium ions are reduced and incorporated into the graphite layers.

[0008] It is also known to use silicon instead of carbon in lithium-ion battery anodes. Silicon is a particularly suitable anode material for lithium batteries due to its highest storage capacity, theoretically up to 4200 mAh / g.

[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. During cell discharge, the applied metal oxide layer serves to store the lithium ions.

[0010] In lithium-ion battery designs, the cathode typically supplies the lithium atoms for charging and discharging in the anode; therefore, the battery capacity is limited by the cathode capacity. Typical cathode materials used to date include Li(Ni,Co,Mn)O₂ and LiFePO₄. Due to the cathode's composition of lithium metal oxides, increasing the capacity is only marginally possible.

[0011] It is known that pre-lithiation of the silicon anode is a suitable way to compensate for lithium losses, especially in the first few cycles, and to ensure lithium retention during operation. Lithiation refers to the incorporation of lithium ions into the host material, such as silicon or graphite. However, pre-lithiation is a complex process. Both CN 112 563 458 A and US 2021 / 0175495 A1 describe a wet-chemical process for pre-lithiating a silicon anode. In an electrochemical pre-lithiation process, a lithium metal electrode and the anode are electronically isolated from each other, and the anode is charged with a low current or an electrical short circuit to initiate lithiation. This process can be repeated for several charge / discharge cycles, for a defined period, or until the anode reaches a defined potential.However, the electrochemical pre-lithiation process requires a re-installation step of the pre-lithiated anode into the lithium-ion battery cell, which increases the effort and reduces the possibility of using this process commercially.

[0012] Another option for pre-lithiation is the use of stabilized lithium metal powder. However, the addition of lithium must be precisely dosed so that no residual lithium remains after incorporation; this is very difficult to control due to slight variations in layer homogeneity. A further disadvantage is the use of highly reactive lithium metal, meaning that the entire electrode fabrication process, or at least parts of it, must be carried out under dry atmospheric conditions, which further increases the cost of lithium-ion battery (LIB) cell production.

[0013] Another method of pre-lithiation is to add an excess of lithium salts to the electrolyte in the cell. However, this alters the cell parameters, especially the conductivity of the electrolyte. This is undesirable during LIB operation.

[0014] Referring to Figure 1 During discharge, lithium ions migrate from the anode through the electrolyte and separator to the cathode, where they are reversibly stored. The oxidation process at the anode releases electrons. These flow from the negatively charged anode, via an external electrical connection, to the positive cathode, where a reduction process occurs and electrons are absorbed. This external current flow allows electrical devices to be powered. The charging process is exactly the reverse.

[0015] During charging and discharging, the electrolyte acts as an intermediary between the reactions at the electrodes, ensuring the transport of lithium ions. It must exhibit high ionic conductivity and be stable within the voltage range of 0 to 4.5 V relative to Li / Li+ as a reference, as well as within the operating temperature range of the battery. Electrolytes include liquid, polymer, and solid forms, as well as mixtures (hybrid cells) of these. In suitable liquid and polymerized electrolytes, a protective layer forms on carbon-based anodes, as well as directly on silicon or other electrodes. This layer is known as the Solid Electrolyte Interphase (SEI). It protects the anode from the corrosive electrolyte solution while remaining permeable to lithium ions. This layer is essential for the use of lithium or lithium-ion intercalation compounds in primary and secondary cells.However, the formation of the SEI layer in the first few battery operating cycles is accompanied by a loss of free lithium ions, which are then no longer available for operation. Therefore, the pre-lithiation process mentioned above is used, the influence of which is exemplified in [reference to relevant example]. Figure 2 The lithium reservoir in the cathode is limited. Introducing additional lithium into the anode through pre-lithiation can compensate for otherwise unavoidable losses. Fig. 2c This shows that the storage capacity of the cathode is exhausted; no additional lithium can be added.

[0016] The separator separates the two electrodes to prevent an electrical short circuit resulting from direct contact. Materials used include, for example, polymer membranes, ceramic separators, nonwovens, and glass fiber separators.

[0017] Energy density is a measure of the energy content of a cell or battery per unit volume or mass. It therefore has a direct impact on, for example, the achievable range of a purely electric vehicle with a traction battery for the same mass or volume and is described as specific [Wh / kg] or volumetric energy density [Wh / l]. A cell with high energy density requires a combination of two electrode materials with high charge density and potential difference.

[0018] Lithium-ion batteries can be categorized into energy-optimized batteries with high energy densities, low power densities, and average discharge currents, and power-optimized batteries with lower energy densities, high power densities, and short-term very high discharge currents. The former are particularly important for battery electric vehicles (BEVs), as the vehicle's range depends on its capacity. In contrast, hybrid electric vehicles (HEVs) place the highest demands on power density and, consequently, on high-current capability during charging and discharging.

[0019] The lifespan of a lithium-ion battery is defined as the period between the delivery date (Beginning of Life, BoL), characterized by properties typically defined in the specifications, and the point in time (End of Life, EoL) when these properties fall below a predefined value due to aging. The EoL for batteries in electric vehicles is usually reached when the storage capacity drops below 80% of the nominal capacity. Lifespan is measured in two ways: cycle life (or cycle stability) and calendar life. Aging refers to a deterioration of the electrochemical properties (e.g., reduced capacity, increased internal resistance, etc.). This is largely caused by energy throughput and cycling. High power demands during battery charging and discharging result in high internal heat generation.This can cause irreversible damage to the electrode materials used and directly influence and accelerate the aging of the cell or system. Capacity decreases over time, leading to an increase in internal resistance and a corresponding decrease in performance. Side reactions that occur during charging in the electrolyte, such as expansion of the active materials or the mechanical work performed by the active substances, also contribute to aging.

[0020] In current lithium-ion battery designs, the cathode supplies the lithium atoms. These are reversibly embedded in the interstitial sites of a lithium metal oxide lattice ( Fig. 1For example, commercial nickel-manganese-cobalt (NCM 622) cathodes have an energy density of up to 210 mAh / g. To provide sufficient capacity for high-capacity battery cells, the cathode layer thickness is increased accordingly to allow for balancing with the anode. Balancing refers to the ratio of the absolute capacity of the cathode and anode. Ratios of 1:1 to 1:1.3 (cathode : anode) are common. The anode is dimensioned larger for safe operation to prevent lithium plating. If lithium is removed from the cathode beyond a certain limit during charging / discharging, the lattice structure of the metal oxide lattice collapses, and lithium cannot be reversibly added. The less expensive but lower-density lithium iron phosphate (LiFePO4) (up to 160 mAh / g) is significantly more robust.As already mentioned, the battery capacity is therefore usually limited by the cathode capacity.

[0021] Especially during the first few cycles of a lithium-ion battery, losses occur due to the decomposition of the electrolyte and the resulting formation of a solid electrolyte interphase (SEI). During this process, and also during the initial charging of the anodes, irreversible lithium losses occur, which must be taken into account during cell construction and balancing. The limited lithium capacity of the cathodes cannot be sustainably increased. Fig. 2c Therefore, any additional introduction of lithium, especially to compensate for initial losses, can only be achieved via the anode.

[0022] Previous solutions utilized pre-lithiation of the anode by employing reactive lithium, which was added to the battery in dry processes, either as a powder or in a molten state. A dry process is defined as one free of water or solvents. Another possibility involves simply bringing a lithium foil into contact with the anode to be lithiated, where pre-lithiation occurs even at room temperature due to the high rate of lithium diffusion.

[0023] Pre-lithiation is a technically complex process involving the construction of a silicon-lithium half-cell and the electrochemical charging of the silicon anode with lithium. Another possibility is the use of an excess of lithium salts in the electrolyte to compensate for the battery's initial losses. A problem arises from the difficulty in controlling the amount of lithium added to the battery. Furthermore, the use of nanostructures prevents uniform pre-lithiation. Additionally, subsequent pre-lithiation in the dry process is only superficial, resulting in an anode that is generally very reactive and difficult to handle, comparable to pure lithium foil. Adding lithium as a powder is difficult to control, and the cell again contains pure, reactive lithium, which is highly reactive, hygroscopic, and oxidizes very quickly.The high reactivity of lithium typically leads to pronounced SEI formation, resulting in high cell resistances during battery operation. Furthermore, high surface currents, common in high-performance batteries, lead to the formation of dendrites, i.e., tree- or shrub-like crystal structures that can penetrate the separator and cause short circuits.

[0024] Concepts for a roll-to-roll system exist for electrochemical pre-lithiation; see [reference]. Figure 3 However, the concept is very complex.

[0025] Figure 3a Figure 1 schematically shows the process of prelithiation of a c-SiO x electrode 9. An electrical short circuit is created between the c-SiO x electrode 9 and a piece of lithium metal foil 10 in the presence of an electrolyte 4 and a separator 5, thus initiating spontaneous prelithiation through the potential difference between the two electrodes ( Fig. 3aThe speed of the prelithiation can be controlled by means of the built-in resistor 13. The endpoint of the prelithiation is determined by the cell voltage 14, which is monitored throughout the entire prelithiation process. Figure 3b shows the pre-lithiation process in a roll-to-roll coating.

[0026] It is therefore the object of the present invention to provide a method which is suitable for introducing additional lithium into the silicon electrode, in particular to compensate for the initial losses, and which is suitable for industrial use, without, however, exhibiting the disadvantages of the prior art.

[0027] This problem is solved by a method according to independent claim 1. In the inventive method for producing a silicon electrode as an anode for a lithium-ion battery, in which a silicon layer structure is applied to a support substrate, the silicon electrode is subjected to pre-lithiation according to the invention by introducing lithium into the silicon layer structure by a process. A silicon layer structure is characterized by the repeated application of silicon and optionally other functional layers to a substrate (multilayer or multiple stack). A protective layer is applied, and the introduced lithium is subjected to a controlled and diffusion-controlled reaction with the silicon layer structure to form lithium silicide by subsequent short-term annealing with a targeted energy input.

[0028] Short-term annealing refers specifically to flash lamp annealing and / or laser annealing. Flash lamp annealing is performed with a pulse duration or annealing time in the range of 0.3 to 20 ms and a pulse energy in the range of 0.3 to 100 J / cm². In laser annealing, the annealing time of 0.01 to 100 ms is set by the scanning speed of the local heating point to generate an energy density of 0.1 to 100 J / cm². The heating ramps achieved in short-term annealing are in the range of 10⁴–10⁷ K / s required for the process. Flash lamp annealing utilizes a spectrum in the visible wavelength range, whereas laser annealing employs discrete wavelengths in the infrared (IR) to ultraviolet (UV) spectrum.

[0029] The inventive method allows a defined amount of lithium to be incorporated into the silicon electrode without significant effort. Initial losses during initial battery operation can thus be specifically compensated for, and a significantly simpler balancing of the cathode and anode of lithium-ion batteries is made possible.

[0030] An advantage is that an additional top layer, such as silicon or carbon, is automatically deposited, acting as a protective layer, thus facilitating simple further processing of the anode.

[0031] In the process according to the invention, the subsequent short-term annealing enables the stabilization of the lithium layer. The targeted energy input allows the desired distribution of lithium in silicon and, if possible, a reaction to lithium silicide under controlled diffusion; i.e., once saturation has occurred, the reaction to lithium silicide ends.

[0032] An advantageous energy input is achieved when flash lamp tempering is carried out with a pulse duration in the range of 0.3 to 20ms, with a pulse energy in the range of 0.3 to 100J / cm 2< and with preheating or cooling in the range of 4°C to 200°C.

[0033] If laser annealing is used for short-term annealing, diffusion and reaction of metal with silicon is controlled by 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 / cm², as well as preheating or cooling in the range of 4°C to 200°C of the laser annealing process.

[0034] In one embodiment of the process according to the invention, the lithium is introduced into the silicon layer structure in a dry process. This is made possible by the unique silicon layer structure. The special feature of this silicon layer structure is the presence of multiphases in the silicon layer and the metal substrate. These multiphases consist of amorphous silicon and / or crystalline silicon from the silicon layer, crystalline metal from the metal substrate, and silicide. The multiphase silicon layer has free spaces to accommodate the volume change during lithiation, thus stabilizing the entire material composite. The lithium can be incorporated in any quantity as an intermediate layer using a dry process, for example, cathode sputtering, and subsequently covered with a protective layer.

[0035] In a further embodiment of the inventive method, the lithium is therefore introduced into the silicon layer structure in a controlled manner by sputtering. Sputtering is a controllable method with which the amount of lithium to be introduced into the silicon electrode can be precisely controlled. The lithium is present as a solid target.

[0036] In another embodiment of the inventive method, the lithium is introduced into the silicon layer structure in a controlled manner by thermal evaporation. Thermal evaporation is a controllable method with which the amount of lithium to be introduced into the silicon electrode can be precisely controlled. The lithium is initially in solid form, is liquefied, and then evaporated.

[0037] In another embodiment of the inventive method, the lithium is introduced into the silicon layer structure by thermally assisted rolling. Although thermally assisted rolling is a less precise method for introducing lithium into the silicon electrode, it is very easy to perform. The lithium is present in solid form in this process.

[0038] In one embodiment of the process according to the invention, the lithium is introduced into the silicon layer structure by lithium melt deposition under vacuum or in an inert gas atmosphere. Lithium melt deposition under vacuum or in an inert gas atmosphere is also a less precise method for introducing lithium into the silicon electrode, but it is nevertheless easy to perform. The lithium is present in liquid form as the starting material. The special feature of lithium melt deposition is the ease with which the deposition process can be integrated into a planar roll-to-roll process, in which the lithium is introduced as an interlayer into the silicon layer structure. Pre-functionalization of the copper layer, i.e., the current collector, e.g., by applying a layer of silicon to increase the wettability of liquid lithium, is readily possible.

[0039] In another embodiment of the inventive method, the lithium is introduced separately as a single layer or it is introduced as a mixed layer, in particular of lithium and silicon.

[0040] In one embodiment of the inventive process, the protective layer is deposited from silicon, carbon, or copper. The protective layer can additionally be formed from one or more layers of an artificial solid electrolyte interphase (SEI), which is deposited in a vacuum or inert gas process, e.g., an atomic layer deposition (ALD) process. It is advantageous if the artificial SEI is formed from Al₂O₃, TiO₂, SiO₂, and / or LiOH, because these prevent further oxidation and are nevertheless sufficiently permeable to Li⁺ ions during battery operation.

[0041] The process according to the invention can advantageously be used to produce silicon electrodes as anodes in battery cells where the lithium is added to the battery cell from the opposite direction to the cathode. Adding lithium from the opposite direction to the cathode means that the lithium is not supplied to the battery cell via the cathode. This is the case with novel cell types, for example, third-generation lithium-sulfur (Li-S) batteries. The designation "third generation" distinguishes it from second-generation lithium-ion batteries because the transport between the cathode and anode does not occur via Li+ ions, but rather via a Li₂S compound. The targeted introduction of lithium into the silicon electrode as the anode, or pre-lithiation, enables new and innovative cell concepts for which, until now, only highly reactive lithium in foil form seemed feasible.

[0042] The process according to the invention can advantageously also be used in lithium-sulfur (Li-S) batteries. The silicon anode produced according to the invention is therefore considered ideal, especially for resource-efficient Li-S battery designs with sulfur as the cathode material. Sulfur, as a cathode material, has the highest known energy density of lithium, up to 1600 mAh / g. This enables batteries with the highest volumetric and gravimetric energy density. Both sulfur and silicon are abundant resources; together with the controlled introduction of lithium, this concept represents the most resource-efficient use of a reusable lithium battery.

[0043] The method according to the invention can advantageously also be used for the construction of a lithium-ion battery with a lithium nickel manganese cobalt oxide (NMC), a lithium nickel cobalt aluminum oxide (NCA) or lithium iron phosphate (LFP) cathode.

[0044] The invention will be explained in more detail below using an exemplary embodiment.

[0045] The drawings show Fig. 1 Exemplary structure and function of a lithium-ion cell during the discharge process; Fig. 2 Influence of pre-lithiation on the availability of lithium in the first charging cycles of a lithium-ion battery; Fig. 3 Illustration of a) pre-lithiation, as well as its application in a roll-to-roll manufacturing process; Fig. 4 Schematic representation of the inventive method for producing a silicon electrode as an anode for a lithium-ion battery; Fig. 5 Schematic representation of a system for carrying out the inventive method; Fig. 6 Application of the Si anode produced by the inventive method in a Li-S battery; Fig. 7 SEM-SE image of an active layer of 3 µm silicon interrupted by 100 nm copper and 100 nm lithium each, produced according to the inventive method.

[0046] Figure 4Figure 1 shows the process steps according to the invention in a flowchart. A substrate, which simultaneously serves as a current collector, undergoes pre-purification under vacuum conditions in a plasma atmosphere. Subsequently, silicon layering and pre-lithiation are carried out by sputtering. A Si / Li layer is sequentially deposited, with the layers being stabilized by flash lamp annealing. Flash lamp annealing enables targeted energy input, allowing the silicon layer buildup to be dosed and diffusion-controlled to lithium silicide; i.e., once saturation has occurred, the reaction to lithium silicide ends. Preferred process parameters for flash lamp annealing are a pulse duration in the range of 0.3 to 20 ms, a pulse energy in the range of 0.3 to 100 J / cm², and preheating or cooling in the range of 4°C to 200°C is advantageous.The layers are sputtered in multiple layers and stabilized using flash lamp annealing until the desired target thickness is achieved. This process is very easy to perform.

[0047] Figure 5Figure 1 schematically shows an exemplary roll-to-roll coating system for carrying out the process according to the invention. For the production of the silicon electrode as anode 9, a silicon layer or a silicon layer structure is applied to a metal substrate 2. A copper foil, for example, is fed through the system from a first roll at the belt start 15. A functional layer, followed by layers of silicon and lithium, is sputtered onto this foil alternately 16, 17 and subjected to short-term annealing 18 using a flash lamp. The belt can be moved forwards and backwards through the system at any time to apply a desired layer structure. Up to three sources can be installed in the chambers 16, 17, 21, so that up to three different materials can be deposited in each chamber. Accordingly, lithium could be introduced into each chamber. However, it is important that the material is embedded in a layer stack to prevent any lithium from reaching the surface.Subsequently, silicon is deposited by thermal evaporation 19 and a controlled conversion to lithium silicide is achieved by short-term annealing, in particular flash lamp annealing 20. Further layers can be deposited by sputtering 21. A final treatment in a (reactive) plasma 22 is possible, as is a final short-term annealing, in particular flash lamp annealing, 23 to finalize the stack. The coated substrate is then wound back onto a reel 24. Short-term annealing, in particular flash lamp annealing, after the deposition of the silicon layer stack can, among other things, enable the formation of a porous silicide matrix in which amorphous or nanocrystalline silicon occurs together with cavities or pores. However, a silicide matrix is ​​not strictly necessary.

[0048] Figure 6Figure 1 shows an application of the silicon electrode produced by the inventive method as an anode 9 in a lithium-sulfur battery. The targeted introduction of lithium into the silicon anode 9, or pre-lithiation, enables new and innovative cell concepts for which previously only highly reactive lithium in foil form seemed possible. The silicon anode produced by the inventive method is considered ideal, especially for resource-efficient designs of lithium-sulfur batteries with sulfur as the cathode material. Sulfur, as a cathode material, has the highest known energy density of lithium, up to 1600 mAh / g. Both sulfur and silicon are abundant resources; together with the controlled introduction of lithium, this concept represents the most resource-efficient use of a reusable lithium battery.

[0049] The REM-SE image in Figure 7The diagram shows an active layer with a layer sequence 25 of 3 µm silicon 26 interrupted by 100 nm copper 28 and 100 nm lithium 27. The materials were sputtered in the Figure 5 The depicted facility is isolated. Reference symbol list

[0050] 1 Lithium-ion battery 2 Collector on anode side 3 SEI solid electrolyte interphase 4 Electrolyte 5 Separator 6 Conductive interphase 7 Cathode, positive electrode 8 Collector on cathode side 9 Anode, negative electrode 10 Lithium foil 11 Lithium ions 12 Roller 13 Resistor 14 Cell voltage 15 Belt start 16 First sputtering, sputtering module 17 Second sputtering, sputtering module 18 First flash lamp annealing, short-term annealing 19 Thermal evaporation 20 Second flash lamp annealing, short-term annealing 21 Third sputtering, sputtering module 22 Plasma cleaning 23 Third flash lamp annealing, short-term annealing 24 Belt end 25 Silicon layer build-up 26 Silicon 27 Lithium 28 copper

Claims

1. A method for producing a silicon electrode as an anode for a lithium-ion battery, wherein a stratified silicon construction is applied to a carrier substrate, characterized in that the silicon electrode is subjected to a prelithiation by introduction of lithium as an intermediate layer into the stratified silicon construction by a process, in that a protective layer is applied and in that the introduced lithium is subjected to metered and diffusion-controlled reaction with the stratified silicon construction to form lithium silicide by subsequent short-term annealing with a targeted energy input, wherein the short-term annealing is flash-lamp annealing performed with a pulse duration in the range of 0.3 to 20 ms and a pulse energy in the range of 0.3 to 100 J / cm2, and / or laser annealing performed with an annealing time of 0.01 to 100 ms established through the rate of scanning of the local heating site, to generate an energy density of 0.1 to 100 J / cm2, and wherein the lithium is introduced into the stratified silicon construction in a dry process, wherein the protective layer is deposited from silicon or carbon or copper.

2. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in claim 1, characterized in that the lithium is introduced into the stratified silicon construction by controlled sputtering.

3. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in claim 1, characterized in that the lithium is introduced into the stratified silicon construction by controlled thermal vaporization.

4. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in claim 1, characterized in that the lithium is introduced into the stratified silicon construction by thermally assisted rolling.

5. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in claim 1, characterized in that the lithium is introduced into the stratified silicon stack by lithium melt deposition under vacuum or in an inert gas atmosphere.

6. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in any of claims 1 to 5, characterized in that the lithium is introduced separately as an individual layer.

7. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in any of claims 1 to 5, characterized in that the lithium is introduced as a mixed layer, more particularly of lithium and silicon.

8. The method for producing a silicon electrode as an anode for a lithium-ion battery as claimed in claim 1, characterized in that the protective layer is additionally formed from one or more strata of an artificial solid-electrolyte interphase, SEI, which is deposited in a vacuum or inert-gas process, wherein the artificial SEI is formed from Al2O3, TiO2, SiO2 and / or LiOH.

9. The use of the method for producing a silicon electrode as an anode for a lithium battery as claimed in claims 1 to 8 in battery cells, wherein the lithium is added away from the cathode into the battery cell.

10. The use of the method for producing a silicon electrode as an anode for a lithium battery as claimed in claims 1 to 8 for the construction of a lithium-sulfur battery, with sulfur as cathode material.

11. The use of the method for producing a silicon electrode as an anode for a lithium battery as claimed in claims 1 to 8 for the construction of a lithium-ion battery with a lithium nickel manganese cobalt oxide, NMC, a lithium nickel cobalt aluminum oxide, NCA, or a lithium iron phosphate, LFP, cathode.