Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/134—Electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
  • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/386—Silicon or alloys based on silicon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• 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.
• the invention also relates to a battery cell which comprises the silicon electrode according to the invention and a battery which comprises at least one battery cell.
• Electrochemical energy storage is an essential cornerstone of a global energy transition in order to temporarily store fluctuating renewable electricity and make it available for stationary and mobile applications.
• the rapid development in the field of electromobility and mobile communication devices also increases the demand for high storage capacities and high charging rates for energy storage devices. This is where the established technologies reach their limits.
• new materials are also required in addition to diversifying energy storage concepts.
• these should improve the technical performance of corresponding energy storage concepts (including capacity, energy density, service life), and on the other hand, they should also minimize manufacturing costs.
• the latter can be achieved in particular through the use of readily available chemical elements, such as silicon for which there is already a broad technology base.
• Batteries are electrochemical energy storage devices and are divided into primary and secondary batteries.
• 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 that occurs is reversible, so that multiple use is possible. When charging, electrical energy is converted into chemical energy, and during discharging it is converted from chemical energy into electrical energy.
• Battery is the generic term for cells connected together.
• Cells are galvanic units consisting of two electrodes, electrolytes, separator and cell housing.
• Figure 1 shows an exemplary structure and the function of a lithium-ion cell during the discharging process. The components of a cell are briefly explained below.
• the cathode consists, for example, of mixed oxides that are applied to an aluminum collector. Transition metal oxides with cobalt (Co), manganese (Mn) and nickel (Ni) or aluminum oxide (AI2O3) are the most common compounds.
• the applied metal oxide layer serves to store the lithium ions when the cell is discharged.
• the anode of the Li-ion cell can consist of a copper foil as a collector and a layer of carbon as an active material. Natural or artificial graphite is usually used as the carbon compound because it has a low electrode potential and a low volume expansion during the charging and discharging process. During the charging process, lithium ions are reduced and stored in the graphite layers.
• Li (Ni, Co, Mn) O2 and LiFePO. ⁇ Due to the structure of the cathode using lithium metal oxides, an increase in capacity is only possible insignificantly.
• silicon instead of carbon in Li battery anodes.
• Silicon is a semiconductor with poor conductivity, very hard and brittle, the surface reacts with oxygen Silicon dioxide.
• silicon as an anode material has a high storage capacity of 3579 mAh/g at room temperature compared to conventional carbon-like materials such as.
• 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 and lead to short circuits in the battery and thus rapid cell death.
• Matrix includes amorphous, nanocrystalline areas of silicon.
• the adhesive layer guarantees an extremely stable contact of the active layer of the anode with the current collector of the anode, on the one hand through a mechanical fixation using a roughened surface and on the other hand through a (partial) reaction with the substrate (chemisorption).
• Adhesive layers that can be used or used 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 adhesive layer.
• 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, which creates an extremely strong adhesion between the multilayer structure and the current collector, which does not change weakens during battery operation.
• the at least one layer can also be formed by a mixing system, the mixing system made of silicon being 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 into a mixed layer by co-deposition (Fig. 8a) of the starting materials.
• the layer thickness for silicon is between 500 - 1000 nm, for metal the layer thickness is between 10 - 100 nm. This means that a multilayer structure of the active layer with a total thickness of 5pm can consist of up to 20 individual layers.
• a further layer of silicon or the mixed system and/or a protective layer which forms a planar surface is arranged on the multilayer structure.
• the deposition technology used for the multilayer structure creates a planar surface.
• a layer of silicon, or the mixed system of silicon and one or more metals can be arranged up to a desired layer thickness and / or a protective layer.
• the planar layer structure has only a small surface area that does not change during battery operation.
• a boundary layer and/or a solid electrolyte is therefore arranged on the planar multilayer structure.
• planar layer structure of the multilayer structure simultaneously offers the possibility of building an artificial protective layer (artificial SEI) through to the application of a solid electrolyte for battery optimization and is therefore suitable for new cell concepts.
• artificial SEI artificial protective layer
• the multilayer structure has an active layer thickness of 10pm.
• the multilayer structure has a specific capacity of >1500mAh/g, preferably >2000mAh/g.
• the active layer can be used in a multi-layer structure or in the multilayer structure, both terms are used synonymously, with various materials and silicon or in the manner of a mixed system made of silicon and one or more metals to produce a specific capacity of over 1500mAh/g, preferably over 2000 mAh/g .
• the specific capacity of pure silicon of 3579 mAh/g the capacity of the Si electrode according to the invention reaches more than 50%.
• the multilayer structure has an area capacity of 2mAh/cm 2 to 6mAh/cm 2 . Larger surface capacities do not make sense because the cost of production increases with increasing layer thickness.
• the multilayer structure can be produced alternately in multilayers by separate layer deposition of the silicon and the at least one metal.
• the advantage of a layered structure over a mixed system is that you can vary each layer in each layer and thus create a customized structure with advantageous properties. For example, to control the volume expansion, a gradual build-up can be created in which an increased metal silicide is present in the area close to the substrate Portion is inserted, whereas in the one near the surface
• a silicon-rich structure can be selected.
• the short-term annealing is a laser annealing, which is carried out using a laser with an annealing time in the range from 0.01 to 100 ms by setting a scanning speed of a local heating point and an energy density in the range from 0.1 to 100J/cm 2 and / or can be carried out with preheating or cooling in the range from 4°C to 200°C.
• the temperature range from 4°C to 200°C this refers to the surface temperature of the substrate or the layer to be tempered.
• the reactions between the silicon particles and the metal particles forced by the short-term tempering are non-equilibrium processes that can only be realized in the ms range and therefore require the use of a flash lamp or a laser.
• the heating ramps achieved in short-term tempering are in for the range of 10 4 - 10 7 K/s required in the process.
• 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.
• the aforementioned reaction is made possible by the defined energy input into one or more layers of particles by means of short-term annealing. There is a sufficient reaction between metal and silicon without the silicon reacting completely. Only insufficient active material remains. More metal means more reaction options but less active material. More energy means more adhesion but less active material. An optimal result depends on the materials used and particle sizes.
• Fig. 1 Example of structure and function of a lithium-ion cell during the discharging process
• FIG. 3 Schematic representation of the planar Si anode according to the invention
• Fig. 4 Schematic representation of the process for producing an adhesive layer made of silicon
• FIG. 5 Schematic representation of a method for producing a multilayer structure made of silicon and metal
• Fug. 7 Schematic representation of a multilayer structure, which is formed from a mixed system, according to a further variant of the Si electrode according to the invention.
• FIG. 9 Schematic representation of a method for producing a mixing system with gradients.
• Figure 2b shows the influence of the short-term annealing 13, in particular flash lamp annealing, on the silicid formation 12 at the contact point in a layer system made of copper 10 and silicon 11. Due to the very short lightning pulse in the range of 0.1 to 10 ms, the silicon 11 does not react completely with the copper 10 to form copper silicide 12. Through the flash lamp annealing 13, pure amorphous or nanocrystalline silicon 11 remains, which is available as an active material for lithium storage, while at the same time there are a sufficient number of inactive areas that ensure stability and good electrical conductivity.
• Figure 4 shows process steps for producing an adhesive layer 14 on the copper substrate 10 for the subsequent construction of the active layer 15 of the Si anode.
• a substrate 10 which also serves as a current collector in a LIB (lithium-ion battery), undergoes a 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 with the copper substrate 10 during flash lamp annealing 13 (FLA - flash lamp annealing) and the silicon layer 11 thus would not adhere to the Cu substrate 10.
• a first silicon layer 11 is then deposited, e.g. B. by sputtering.
• This first silicon layer 11 reacts with the Cu substrate 10 in a transition region to copper silicide 12, thereby increasing the roughness of the substrate 10, e.g. B. a Cu foil, is increased and the silicon layer reacted with the copper serves as a kind of adhesive layer for the further layer structure.
• the copper silicide layer 12 is completely inactive in a battery, so that in a following step a diffusion barrier 19, e.g. B. is applied from carbon.
• This diffusion barrier 19 is necessary in order to prevent the reaction of silicon 11 in copper 10 to form copper silicide 12 during further short-term tempering 13.
• Further Si layers 11, 31 can then be applied sequentially, the layers being able to be stabilized by flash lamp annealing 13 (FIG. 5).
• the advantage of repeated Si -Ab separation and subsequent flash lamp annealing 13 is that with each sequence a stable ("reacted") layer with a closed interface is formed, which acts as an intermediate layer (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 method according to the invention described thus also causes a roughening of the surface, so that good adhesion is created for further layers.
• the growth of column structures is also promoted, so that better ion conductivity can be achieved and the copper content can be well controlled for subsequent processes.
• a protective layer 16 is applied to the multilayer structure 15.
• the diffusion and silicide formation 30 can be controlled in a layer, so that a gradual course of silicide formation can be set perpendicular to the surface.
• Figure 9 shows the possibility of producing a layer gradient in a deposited multilayer structure made of partially reacted layers/layers 30.
• the gradual course 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.
• a small gradient means that the concentration of silicide in a layer 31 or in the active layer 15 of the anode 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 the silicide concentration decreases quickly.
• a high silicide concentration forms on the underside of the layer 31, which decreases rapidly, with only silicon 11 being present on the upper 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 storage of lithium, whereas the silicide formation 12 increases the electrical conductivity.
• the gradual progression e.g. B. 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 a layer thickness of the deposited layers, i.e. H. 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 enough unreacted silicon for the lithium incorporation.
• the overall structure of the silicon electrode according to the invention as an anode in a lithium-ion battery is as follows:
• the active layer was deposited in the multilayer structure 15 with various materials (metals and silicon) or as a mixed system 22 made 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 mixing system and/or a protective layer or optionally a boundary layer up to a structure of a solid electrolyte is deposited, which has a planar surface.
• an active layer thickness of the active material of the anode of 10 pm is achieved, which enables a surface capacity of 4 mAh/cm 2 with a specific total capacity of 2000 mAh/g.
• This layer structure enables excellent lithium diffusion as well as high electrical conductivity and is suitable for battery operation without the active layer 15 pulverizing.
• the active layer 15 of the anode has an electrical conductivity that is up to 100 times higher than graphite of up to 5*10 4 S/cm due to the heterogeneous formation of a silicide framework. Due to the low resistance, less waste heat is generated during charging/discharging and a more compact design of the entire cell is possible with less cooling.
• planar surface limits the build-up of SEI to an absolute minimum and only the smallest amounts of additives are necessary for SEI control. This also results in low electrolyte consumption and a long service life for anodes constructed in this way.
• Lithium ion battery Collector on anode side SEI -Solid-Electrolyte- Interphase Electrolyte Separator Conductive intermediate phase Cathode, positive electrode Collector on cathode side Anode, negative electrode Copper substrate Silicon Copper silicide, metal silicide

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• 2023
  • 2023-02-08 EP EP23706702.0A patent/EP4540871A1/de active Pending
  • 2023-02-08 CN CN202380046838.1A patent/CN119365981A/zh active Pending
  • 2023-02-08 JP JP2024569076A patent/JP2025520280A/ja active Pending
  • 2023-02-08 KR KR1020247042335A patent/KR20250025632A/ko active Pending
  • 2023-02-08 TW TW112104454A patent/TWI887602B/zh active
  • 2023-02-08 WO PCT/EP2023/053091 patent/WO2023247074A1/de not_active Ceased

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