Method for reproducing electrochemical properties of a lithium foil
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- TRUMPF LASER & SYSTEMTECHNIK GMBH
- Filing Date
- 2024-01-26
- Publication Date
- 2026-04-29
AI Technical Summary
Lithium foils used in battery systems, especially solid-state batteries, deteriorate when exposed to improper atmospheres like water, oxygen, and nitrogen, leading to increased ion resistance and reduced performance and capacity due to the formation of lithium compounds on their surface.
A pulsed laser beam source is used for surface processing to remove lithium compounds and introduce structuring on the lithium foil, reducing ion resistance by cleaning and expanding the surface area, thereby enhancing the electrochemical properties and performance of the lithium foil.
The process effectively reduces ion resistance, leading to improved battery performance and capacity, even surpassing that of untreated lithium foils, by simultaneously removing contaminants and structuring the surface with precise control over laser parameters.
Smart Images
Figure EP2024051944_02012025_PF_FP_ABST
Abstract
Description
[0001] Title: Method for restoring electrochemical properties of a lithium foil
[0002] Description
[0003] The invention relates to a method for surface treatment of a lithium foil and a battery foil for a solid-state battery.
[0004] Lithium foils or lithium metal foils, as well as lithium-coated copper foils, are promising for use in battery systems, especially solid-state batteries, due to their excellent electrochemical properties. Lithium serves as the anode material. Lithium is a highly reactive alkali metal. Therefore, the storage and use of lithium is particularly challenging. Improperly handled or stored lithium foils lead to deteriorated battery performance and capacity.
[0005] US Pat. No. 6,951,120 B2 discloses laser processing of crystalline lithium niobate. The laser has a laser beam with a wavelength close to the absorption edge of lithium niobate. The laser beam is emitted in short-duration pulses and at a repetition rate selected to ablate the surface of the lithium niobate without damaging the base material. The laser beam and the substrate can be shifted relative to one another to create a trench of the desired geometry in the lithium niobate.
[0006] The invention is based on the object of restoring the electrochemical properties of a lithium foil which has been exposed to an improper atmosphere, in particular water, oxygen and / or nitrogen.
[0007] The problem underlying the invention is solved by a method having the features of claim 1. The method provides for surface treatment of a lithium foil using a pulsed laser beam source, wherein the surface treatment reduces the ionic resistance of the lithium foil. The laser beam source is configured to remove lithium compounds formed on the lithium foil and to introduce a structure into the surface of the lithium foil.
[0008] Studies have shown that improper storage of lithium foils leads to an increase in impedance and ionic resistance as lithium compounds are deposited on the surface of the lithium foil.
[0009] The process firstly cleans the surface of the lithium foil by removing the lithium compounds. This leads to a reduction in ionic resistance. It is surprising that the lithium compounds can be removed using a pulsed laser beam source. Secondly, the process structures the surface of the lithium foil. This leads to a further reduction in ionic resistance due to the larger surface area, so that surprisingly a lower ionic resistance can be achieved in the restored lithium foil than in an untreated and correctly handled lithium foil. Consequently, when the processed lithium foil is used in a battery, the batteries can achieve increased performance and capacity. In addition, the process is particularly efficient because the removal and structuring can be carried out simultaneously.
[0010] For the purposes of this invention, a "lithium foil" is understood to mean a flat material containing lithium. The flat material may further comprise a carrier material, such as a copper foil. Accordingly, a copper foil coated with lithium is also to be regarded as a lithium foil.
[0011] An advantageous development provides that a pulse energy of the laser beam source lies in a range between 4 pj and 6 mJ, in particular less than 50 pj or greater than 250 pj. It is advantageous if the pulse rate of the laser beam source is greater than 10 kHz. It is further advantageous if the beam diameter of the laser beam source on the surface of the lithium foil lies in a range between 25 gm and 600 gm. This is accompanied by the advantage that the ion resistance of the lithium foil is further reduced. Accordingly, the use of the processed lithium foil, for example in a solid-state battery, results in increased battery capacity and performance.
[0012] It is advantageous if a lithium foil is provided in the surface treatment process which has previously undergone a reaction which increases the ionic resistance, in particular a reaction with water, oxygen and / or nitrogen. This occurs if, for example, the lithium foil is stored improperly or if a leak occurs. As a result, a large number of lithium compounds, in particular lithium oxide, lithium nitrides, lithium hydroxides and lithium carbonates, have formed in the lithium foil. The provision of such a lithium foil is particularly well suited for use with the laser beam source with the aforementioned parameters, so that a significant reduction in the ionic resistance can be expected.
[0013] It is advantageous if the laser beam source introduces a structure into the surface of the lithium foil with a structure depth of at least 10% and / or of at least 2.5 gm and / or of at most 30% and / or of at most 10 gm, in particular of at most 5 gm, compared to the non-structured regions of the surface of the lithium foil. This is accompanied by a further reduction in the ion resistance. It is furthermore advantageous if the laser beam source is set up in such a way that it has a pulse shape with a pulse peak power which is at least 10% above an average pulse power of the laser beam source. This is accompanied by a defined structural shaping of the structure introduced into the surfaces.
[0014] The laser beam source is preferably designed as an ultrashort pulse laser, in particular as an ns laser, ps laser, or fs laser. This achieves high intensities at moderate average power levels, ensuring targeted heat input to the surface. The laser beam source can be designed as a NIR laser.
[0015] A further advantageous development provides that the laser beam source has a beam quality M 2 in a range between 1 and 5 and / or wherein the laser beam source is a single-mode laser or a multi-mode laser. This ensures targeted melting and / or evaporation of the surface of the lithium foil.
[0016] It is advantageous if surface treatment, especially laser treatment, is carried out in a dry room atmosphere. This ensures a reduction in the reaction of the lithium foil with water in the ambient air.
[0017] It is also advantageous if the drying room atmosphere is adjusted to a dew point of at most -15. An advantageous further development provides for the use of a beam deflection unit, in particular a scanner optics, to guide the laser beam source during surface processing. This ensures high speed during laser processing.
[0018] It is advantageous to use multiple laser beam sources and / or multiple optics simultaneously. This allows the scan fields to be superimposed to ensure the desired contour size. Furthermore, this results in increased productivity.
[0019] Preferably, the position and / or circumferential geometry of the lithium foil is recorded during surface processing, particularly laser processing. An optical sensor system, particularly a camera system and / or optical coherence tomography (VisonLine), can be used for this purpose. Consequently, tolerances in the lithium foil can be compensated, resulting in greater precision and lower scrap.
[0020] It is further advantageous if the processing position of the laser beam source, in particular the beam deflection unit, is adjusted depending on the position and / or the circumferential geometry of the lithium foil. Consequently, automated path programming can be provided.
[0021] Advantageously, during surface processing, particularly laser processing, the surface, in particular the surface roughness, and / or the cutting position of the lithium foil are recorded. A distance sensor and / or optical coherence tomography and / or laser triangulation can be used for this purpose. The cutting position can be controlled using the surface and / or the cutting position, thus ensuring greater contour fidelity.
[0022] A further advantageous development of the invention provides that a lithium foil is processed at least partially continuously by the laser beam source, in particular the beam deflection unit, following the position of the lithium foil. The compensation of the relative movement of the lithium foil and the laser beam source can be compensated for by means of a control unit. Accordingly, a lithium foil can be unrolled from a roll, and the lithium foil can be processed at the same time. This allows consistent processing results and a high degree of contour accuracy to be achieved.
[0023] The problem underlying the invention is also solved by a battery foil having the features of claim 15. Accordingly, the battery foil is produced from a lithium foil processed in a method according to one of claims 1 to 16. The battery foil thus represents a foil whose surface has been cleaned of lithium compounds and structured.
[0024] Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which embodiments of the invention are further described and explained.
[0025] Shown are: Fig. 1 flow diagram for a method according to the invention;
[0026] Fig. 2 Laser processing of a contaminated lithium
[0027] foil; and
[0028] Fig. 3 ablated and structured lithium foil.
[0029] According to Fig. 1, in the surface treatment process, a clean lithium foil 10 with a carrier layer 12 made of copper and a lithium layer 14 arranged on the carrier layer 12 is first provided (S10).
[0030] Subsequently, the lithium foil 10 becomes contaminated, e.g., due to improper storage and contact with ambient air (S20). As shown in Fig. 2, lithium compounds 18, particularly lithium oxide, lithium nitrides, lithium hydroxides, and lithium carbonates, form on a surface 16 of the lithium foil 10, particularly on the lithium layer 14, which increases the ionic resistance of the lithium foil 10. Consequently, the excellent electrochemical properties of the lithium foil 10 are lost. Accordingly, such a contaminated lithium foil 10 results in poorer battery capacity and performance.
[0031] In order to restore the electrochemical properties of the lithium foil 10, the latter is processed using a pulsed laser beam source 20 with a laser beam 21. First, a dry atmosphere with a dew point of at most -15° is provided for this purpose (S30). Then the ion resistance of the lithium foil 10 is reduced by the laser beam source 20 being set up in such a way that lithium compounds 14 formed on the lithium foil 10, in particular on the lithium layer 14, are removed and a structure 22 is introduced into the surface 16 of the lithium foil 10 (S40). According to Fig. 3, the structure 22 introduced into the surface 16 of the lithium foil 10 has a structure depth 24 of at least 10% and / or 2.5 μm compared to the non-structured regions 26. The structure shown in Fig. The lithium foil 10 shown in Figure 3 can be used as a battery foil 100 with excellent electrochemical properties for e.g. a solid-state battery.
[0032] The laser beam source 20 has a pulse energy in a range between 4 gj and 6 mJ, a pulse rate greater than 10 kHz and a beam diameter on the lithium foil 10, in particular on the lithium compounds 14 and / or on the lithium layer 14, in a range between 25 gm and 600 gm.
[0033] The laser beam source 20 is configured such that it has a pulse shape with a pulse peak power which is at least 10% above an average pulse power of the laser beam source 20.
[0034] The laser beam source 20 is designed as an ultrashort pulse laser, in particular as an ns laser, ps laser or as an fs laser.
[0035] The laser beam source 20 has a beam quality M2 in a range between 1 and 5. The laser beam source 20 is designed as a single mode laser or as a multi-mode laser. For beam guidance, the laser beam source 20 has a
[0036] Beam deflection unit 28, in particular a scanner optics, on .
[0037] Furthermore, a sensor device 30 is provided which is designed to detect the position and / or the circumferential geometry and / or the surface 16, in particular the surface roughness, and / or the cutting position of the lithium foil 10 during the surface processing.
[0038] In addition, a control device 32 is provided which controls the parameters and / or the position of the laser beam source 20 and / or the position of the lithium foil 10, in particular as a function of the sensor data provided by the sensor device 30.
[0039] To increase the surface roughness, the hatch of the laser beam 21 can preferably be reduced. The hatch can preferably be in a range between 0.006 mm and 0.2 mm. Pulse rates of 200 kHz and 360 kHz can be selected.
Claims
Patent Claims 1. Method for surface treatment of a lithium foil (10) using a pulsed laser beam source (20) to reduce the ionic resistance of the lithium foil (10), wherein the laser beam source (20) is configured to remove lithium compounds (18) formed on the lithium foil (10) and to introduce a structuring (22) into a surface (16) of the lithium foil (10).
2. The method according to claim 1, wherein the pulse energy of the laser beam source (20) is in a range between 4 pJ and 6 mJ, and / or wherein the pulse rate of the laser beam source (20) is greater than 10 kHz, and / or wherein the beam diameter of the laser beam source (20) on the lithium foil (10) is in a range between 25 pm and 600 pm.
3. The method according to claim 1 or 2, wherein the laser beam source (20) introduces a structuring (22) into the surface (16) of the lithium foil (10) with a structure depth (24) of at least 10% and / or of 2.5 pm.
4. The method according to one of the preceding claims, wherein the laser beam source (20) is configured such that it has a pulse shape with a pulse peak power that is at least 10% higher than an average pulse power of the laser beam source (20).
5. The method according to one of the preceding claims, wherein the laser beam source (20) is configured as an ultrashort pulse laser, in particular as an ns laser, ps laser, or fs laser.
6. The method according to one of the preceding claims, wherein the laser beam source (20) has a beam quality M 2 in a range between 1 and 5 and / or wherein the laser beam source (20) is designed as a single-mode laser or a multi-mode laser.
7. The method according to one of the preceding claims, wherein the surface treatment is carried out in a dry room atmosphere.
8. The method according to claim 7, wherein the dry room atmosphere has a dew point of at most -15°C.
9. The method according to one of the preceding claims, wherein a beam deflection unit (28), in particular a scanner optics, is used to guide the beam of the laser beam source (20) during surface treatment.
10. The method according to one of the preceding claims, wherein multiple laser beam sources (20) and / or multiple optics (28) are used simultaneously.
11. The method according to one of the preceding claims, wherein the position and / or the circumferential geometry of the lithium foil (10) is detected during surface processing.
12. The method according to claim 11, wherein the processing position of the laser beam source (20) is adjusted depending on the position and / or the circumferential geometry of the lithium foil (10). 13. The method according to one of the preceding claims, wherein the surface (16) and / or the cutting position of the lithium foil (10) is detected during surface processing.
14. The method according to one of the preceding claims, wherein a lithium foil (10) is processed at least partially continuously by the laser beam source (20) following the position of the lithium foil (10).
15. A battery foil (100) for a battery system, wherein the battery foil (100) is produced from a lithium foil (10) processed in a method according to one of the preceding claims.