CUTTING OF SOFT METALS WITH THE AID OF ULTRASOUND

Abstract

Method for cutting soft metals, comprising the use of a cutting tool capable of being set in motion by ultrasonic vibration. The method is employed for cutting components used in the manufacture of an electrochemical storage device, for example, a lithium battery. These components include the anodes, the cathodes, the solid electrolytes, the current collectors and the separators. The method is also employed in a system for manufacturing and/or characterizing an electrochemical storage device.

Claims

1. A method of cutting soft metals, comprising the use of a cutting tool adapted to be set in motion by ultrasonic vibration.

2. A system for cutting soft metals, comprising a cutting tool adapted to be set in motion by ultrasonic vibration.

3. A method for manufacturing and/or characterizing an electrochemical storage device, comprising the use of a cutting tool adapted to be set in motion by ultrasonic vibration.

4. A system for manufacturing and/or characterizing an electrochemical storage device, comprising a cutting tool adapted to be set in motion by ultrasonic vibration.

5. The method of claim 3, wherein the electrochemical storage device is a lithium battery, an “entirely solid” lithium battery, a lithium ion battery, or a cell.

6. The method claim 1, wherein the cutting tool comprises at least one cutting blade coupled to an ultrasonic generator.

7. The method of claim 6, wherein the cutting blade is: a blade adapted to be driven by a guillotine motion, a razor blade, a diamond blade, an exacta blade, a steel blade, a blade made of tungsten carbide, or a combination of these.

8. The method claim 1, wherein the cutting tool is a microtome.

9. The method claim 1, wherein the soft metals are metals having high malleability at room temperature; or metals having a hardness of less than 4 on the Mohs scale.

10. The method of claim 1, wherein the soft metals are soft alkali metals.

11. The method of claim 1, wherein the soft metals are metals malleable at a temperature greater than room temperature.

12. A method for manufacturing and/or characterizing an electrochemical storage device, comprising at least one step of cutting at least one component of the electrochemical storage device, the cutting being performed using a cutting tool adapted to be set in motion by ultrasonic vibration.

13. A system for manufacturing and/or characterizing an electrochemical storage device, comprising at least one cutting tool for cutting at least one component of the electrochemical device, the cutting tool being adapted to be set in motion by ultrasonic vibration.

14. The method of claim 12, wherein the electrochemical storage device is a lithium battery, an “entirely solid” lithium battery, a lithium ion battery, or a cell.

15. The method or system of claim 12, wherein the component of the electrochemical storage device is a negative electrode, a positive electrode, a solid electrolyte, a current collector, a separator, or a combination of these.

16. The method of claim 15, wherein: the negative electrode consists of an alkali metal foil; the positive electrode consists of a composite mixture; the current collector consists of a metal foil; and the separator consists of polymer or ceramic material.

17. The method of claim 12, wherein the cutting tool comprises at least one cutting blade coupled to an ultrasonic generator.

18. The method of claim 17, wherein the cutting blade is: a blade adapted to be driven by a guillotine motion, a razor blade, a diamond blade, an exacta blade, a steel blade, a blade made of tungsten carbide, or a combination of these.

19. The method of claim 12, wherein the cutting tool is a microtome.

20. The method of claim 12, wherein the manufacturing comprises at least one of the following steps: a stacking or assembly of the components of the electrochemical storage device; a resizing of the components of the electrochemical storage device; an extrusion from a billet originating from the melting of an ingot of material constituting a component of the electrochemical storage device; a re-dimensioning of a cell or half-cell; and a stacking of two-sided cells.

21. The method of claim 12, wherein the cutting tool comprises: a blade with a high degree of hardness; and/or a blade with a surface that has been modified by heat treatment; and/or a blade made of a wear resistant material; and/or a blade made of an electrically insulating material.

22. A system for characterizing an electrochemical storage device (lithium battery or “entirely solid” lithium battery or a lithium-ion battery or cell), comprising: a cutting tool adapted to be set in motion by ultrasonic vibration; and/or a microscope; and/or a measuring device.

23. The system of claim 22, wherein the cutting tool comprises at least one cutting blade coupled to an ultrasonic generator.

24. An electrochemical storage device obtained by a method that includes the method as defined in claim 21.

25. A lithium battery or “entirely solid” lithium battery or a lithium-ion battery or cell, obtained by a method which comprises the method as defined in claim 21.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0048] The patent or application file contains at least one color figure. Copies of the published patent or application with the color figures will be provided by the Office upon request and payment of the required fee.

[0049] FIG. 1: Structure of an “entirely solid” lithium battery according to the prior art [4].

[0050] FIG. 2: Cut of lithium metal according to a standard method, without ultrasonic assistance.

[0051] FIG. 3: Lithium metal cut with ultrasonic assistance.

[0052] FIG. 4: Device for cutting a round lithium rod,

[0053] FIG. 5: Result of the cut of the round lithium rod according to FIG. 4, A without ultrasound assistance, B) with ultrasound assistance.

[0054] FIG. 6: Longitudinal cut of a lithium ingot with ultrasonic assistance.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0055] Before this invention is further described, it should be understood that the invention is not limited to the particular embodiments described below, as variations of these embodiments may be realized and remain within the scope of the appended claims. It should also be understood that the terminology used is intended to describe particular embodiments and is not intended to be limiting. Instead, the scope of this invention will be established by the appended claims.

[0056] In order to provide a clear and coherent understanding of the terms used in this description, a number of definitions are provided below, In addition, unless otherwise indicated, all technical and scientific terms, as used in this document, have the same meaning as commonly understood in the technical field to which the invention relates.

[0057] As used in this document, the term “ultrasound” refers to a mechanical and elastic wave, which propagates through fluid, solid, gaseous or liquid media. The frequency range of ultrasound is generally between 16,000 and 10,000,000 Hertz.

[0058] As used in this document, the term “soft metals” refers to metals with high malleability/plasticity at room temperature. Examples of such metals are Pb, Na, Ca, Sr, K, Mg, Al, Sn, Au, Pt, Ba, Cu, Ag, Cd, In, Ga, Bi, Fe, Zn, Li, Ni, Pd, Cs, Rb and their alloys.

[0059] As used in this document, the term “soft alkali metals” refers to alkali metals exhibiting high malleability/plasticity at room temperature. Examples of such metals are Li, Na, K, Mg, Ca, and their alloys.

[0060] As used in this document, the term “‘entirely solid’ lithium battery” refers to a lithium battery in which the electrolyte is in solid form.

[0061] As used in this document, the term “electrochemical storage device” means a rechargeable battery, a battery, a cell, a lithium battery, an “entirely solid” lithium battery, a lithium ion battery, or any other type of storage device.

[0062] As used in this document, the term “cutting” refers to a mechanical operation that allows to divide and/or separate a piece of solid material according to a determined geometry. The division and/or separation allows pieces of reduced size and/or different geometrical shapes.

[0063] As used in this document, the term “characterization” refers to a method by which the electrochemical storage device is examined to determine its architecture. An example of this method is measuring the thickness of each layer of the various components of the cell. This examination method may be linked to a microscope and/or measuring device. This examination method incorporates the cutting method according to the invention, with a microtome (ultrasonically assisted microtomy) as the cutting tool.

[0064] The inventors have designed and employed a method for cutting soft metals. The method according to the invention uses a system comprising a cutting blade set in motion by ultrasonic vibration. The method is employed for cutting components used in the manufacture of electrochemical storage devices, for example, lithium batteries. Such components include the anodes, the cathodes, the solid electrolytes, the current collectors and the separators. These components can be cut up individually or when assembled, for example, as a multilayer assembly, The method is also employed in a system for manufacturing and/or characterizing an electrochemical storage device.

[0065] The method according to the invention allows for the elimination of friction and consequently, the reduction of cutting forces, the reduction of the short-circuit time of an assembled cell during cutting, the minimization of the tool buttering, the reduction of the heating and the wear of the tool used. Also, the method according to the invention provides an improved cut finish.

[0066] According to one embodiment of the invention, the method uses a cutting tool set in motion by ultrasonic vibration. According to another embodiment of the invention, the cutting tool comprises at least one blade coupled to an ultrasonic generator.

[0067] According to one embodiment of the invention, the components of the electrochemical storage device may be cut individually, or during the manufacture of the device. The components of the electrochemical storage device may also be cut when assembled, for example, when it is desired to perform an examination of the device to determine its architecture (characterization of the electrochemical storage device). During such a characterization method, the cutting tool may be coupled to a microscope and/or a device that can be used to measure, for example, the thickness of each layer of the various components of the electrochemical storage device.

[0068] The invention includes the application of ultrasonic assistance to the cutting of soft metals. The invention addresses the cutting problems of components used in the manufacture of electrochemical storage devices, such as an “entirely solid” lithium battery, a lithium-ion battery, or a cell, FIG. 1 reproduced from U.S. Pat. No. 6,030,421 [4] illustrates the structure of such a battery. According to one aspect, the invention allows the cutting of an ingot that is used in extruding a lithium strip.

[0069] Different mechanisms can be used to produce ultrasound; most modern power converters use the piezoelectric effect. The amplitude and frequency of the vibrations and the static load have an influence on the results of the cut. Most installations work at frequencies around 20 kHz, which are close to the lowest frequency compatible with the human ear.

[0070] Optionally, a lubricant, such as a mineral cutting oil, is used. The lubricant helps to reduce heating of the workpiece and the cutting tool. The lubricant also helps eliminate surface oxidation of the tool and of the material being cut and improves the finish of the cut,

[0071] To reduce knife wear, it may be advantageous to use a cutting tool with a knife that has a high degree of hardness and/or a surface that has been modified by various treatments (carburizing, nitriding, quenching, ceramic deposition, or a combination of these). It may also be advantageous to use a cutting tool having a knife made of a wear-resistant material (tungsten carbide, silicon carbide, diamond, alumina, zirconium, silicon nitride, or a combination of these) and/or made of an electrically insulating material.

[0072] The soft metals contemplated according to the invention are those metals presenting a high degree of malleability (high plasticity) at room temperature. Such metals include Pb, Na, Ca, Sr, K, Mg, Al, Sn, Au, Pt, Ba, Cu, Ag, Cd, In, Ga, Bi, Fe, Zn, Li, Ni, Pd, Cs, Rb, and alloys thereof. Those metals presenting a malleability at higher temperatures can nevertheless be cut by the method according to the invention. In such a case, the method is carried out ensuring a thermal protection by ultrasonic assistance to the cutting system.

[0073] An “entirely solid” lithium battery is composed of several components. In the case of an LMP (“lithium metal polymer”) cell, the negative electrode is generally made of an alkali metal light-metal-foil: lithium metal, a lithium-aluminium alloy or the like. In the case of a lithium-ion cell, the negative electrode is usually made up of graphite as active material, deposited on a current collector layer (usually Cu or Ni). The positive electrode is usually made of a composite mixture—material containing a redox active center (transition metal oxide), an electrically conductive filler material (usually carbon particles), a solid electrolyte material (ionic conductor); the composite material deposited on a current collector (usually a thin aluminium foil). The solid electrolyte is usually made of polymer, glass, ceramic or a mixture of these; and allows the conduction of lithium ions (Li.sup.+). The “entirely solid” lithium battery is manufactured by the layering of the positive electrode, the solid electrolyte and the negative electrode. The method is illustrated in FIG. 1 of U.S. Pat. No. 6,030,421 [4],

[0074] The method is employed in a system for manufacturing an electrochemical storage device. The method according to the invention is also employed in a system for characterizing an electrochemical storage device. According to one mode of the invention, the system is adapted for use in the fabrication and characterization of an electrochemical storage device. The storage device may be a lithium battery, an “entirely solid” lithium battery, a lithium ion battery, or a cell.

[0075] Example 1: A piece of lithium is cut with a guillotine blade using a standard method, without ultrasonic assistance (FIG. 2A). Cutting tests show significant deformation of the piece, due to the application of high pressure. A poor surface finish is also observed (FIG. 2B).

[0076] Example 2: A piece of lithium is cut with a razor blade operated with a 20 kHz, 750 W ultrasonic generator (Cole-Palmer) (FIG. 3A). A small amount of light mineral oil is used as a lubricant to protect the lithium from oxidation during the cutting operation. The cut is force-free, fast, and the surface finish is of good quality (FIG. 3B and FIG. 3C). The amplitude is modulated between 20 and 80%; this influences the cutting speed. The lithium does not stick to the blade.

[0077] Example 3: An ultrasound-assisted microtome is used to cut a cell to be studied under a microscope. A vibrating diamond blade cuts a complete cell to visualize the cross section. The cut exposes the different components of the cell (the current collectors, the anode, the cathode, the solid electrolyte, the metal-plastic bag). The cut is clean, only a slight deformation of the different thicknesses of the cell components is observed.

[0078] Example 4: During the method of manufacturing an “entirely solid” battery by stacking two-sided cells, the live (chemically active) cell is cut with a blade by ultrasonic assistance. A short circuit is created (sharp cut) by the action of the metal knife, but the speed of the cut and its sharpness eliminates the need to use chemical healing of the cell edges.

[0079] Example 5: An aluminum strip is slit anew to reduce its width. An ultrasonic assisted exacta blade is used in the method. A clean cut without tearing is obtained. This method is typically used to resize the current collectors, the anodes, the cathodes, the solid electrolytes, the cells, the half-cells, or any other combination of the cell components. It is noted that the durability of the blade is increased.

[0080] Example 6: A lithium ingot 6 inches in diameter and 24 inches long is cast by a melting method. The billet, when removed from the mold, has ends that include imperfections (shrinkage area, porosity, inclusions). In order for the ingot to be extruded without generating defects, the ends are cut using a steel blade with an ultrasound assisted system. A clean finish of the cuts is noted.

[0081] Example 7: Ultrasonic assisted cutting was tested on several soft metals at room temperature. The metals tested include: Pb, Na, Ca, Mg, Al, Cu, Ni. All metals that had a hardness below 4 on the Mohs scale were successfully cut and a fairly clean finish was noted.

[0082] Example 8: Tests were performed to measure the impact of cutting pressure on the deformation of a 10 mm diameter round lithium rod. The setup used is shown in FIG. 4. The rod is coated with mineral oil to reduce heating of the blade. FIG. 5A shows the result obtained after cutting without ultrasound assistance, FIG. 5B shows the result obtained after cutting with ultrasound assistance. The difference is obvious: the cut with ultrasonic assistance produces a dear result. Indeed, the ultrasonic assistance greatly reduces the pressure applied to perform the cut; and the metal remains virtually intact, with no apparent deformation.

[0083] Example 9: A test was performed using an ultrasonic press with integrated generator (TED 2000X, Telsonic) with a sonotrode blade (TE 20 42328, Telsonic). The 150 mm wide by 60 mm high blade, coated with mineral oil and vibrating at an ultrasonic frequency (20 kHz) sliced the lithium ingot along its effective length, cutting it accurately with a clean cut without significantly deforming the ingot, The cut is shown in FIG. 6.

[0084] The above examples relate to an entirely solid lithium battery. The person skilled in the art understands that the invention also relates to other types of batteries including lithium batteries, lithium ion batteries, cells.

[0085] The claims should not be limited in scope by the embodiments illustrated in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[0086] The present description refers to a number of documents. The contents of each of these documents are incorporated in their entirety into the present description by reference.

REFERENCES

[0087] 1. D. Kremer, “Usinage par Ultrasons”, Techniques de I'Ingénieur (Apr. 10, 1998), Ref.: BM7240 V1 [0088] 2. S. Roustel, “Découpe des Produits Aiimen aires”, Techniques de I'Ingénieur (Mar. 10, 2002), Ref.: F1230 V1. [0089] 3. U.S. Pat. No. 1,354,505 of M. W. Round “Method of, and Apparatus for Cutting a Blanket of Confectionery Product”. [0090] 4. U.S. Pat. No. 6,030,421 of M. Gauthier, G. Lessard, G. Vassort, P. Bouchard, A. Vallee and M. Perrier “Ultra-Thin Solid-State Lithium Batteries and Process of Preparing Same”. [0091] 5. U.S. Pat. No. 5,250,784 of D. Muller and B. Kapfer “Method and Device for Cutting a Multilayer Assembly Composed of a Plurality of Thin Films and Comprising a thin Film Electrochemical Generator or a Component Part Thereof”.