Network of metal fibers, method of generating a network of metal fibers, electrode and battery

Abstract

The invention relates to a network of metal fibers comprising a plurality of metal fibers fixed to each other; wherein at least some of the plurality of metal fibers have a length of 1.0 mm or more, a width of 100 µm or less and a thickness of 50 µm or less. The invention further relates to a method comprising the steps of 1. generating a plurality of metal fibers (2) by melt spinning; 2. providing a loose network of the metal fibers (2) generated in step 1; and 3. fixing the plurality of metal fibers to each other by one of the following treatments c1 to c4.

Description

TECHNICAL FIELD

[0001] The present invention relates to a network of metal fibers, a method of manufacturing a network of metal fibers, an electrode comprising a network of metal fibers, and a battery comprising such an electrode. BACKGROUND

[0002] The network of metal fibers can improve the performance of secondary electrodes, as described below. Such a network of metal fibers can also contribute to the performance in catalytic materials, fuel cells, water splitting, as a component in electromagnetic shielding materials, as a filter, in polymer composites, or as a tissue material and tissue hybrid materials, which can also include as an additive, for example, cotton, silk, or wool.

[0003] In lithium ion batteries, the active electrode material is deposited on a metal foil that serves as a current collector. Typically, the negative electrode consists of Li x C n graphite intercalation compounds, while the positive electrode consists of Co-, Ni-, Mn- or Fe compounds that can intercalate lithium cations, and aluminum foil serves as a current collector. Upon discharge, electrons are transferred to the copper collector, and lithium cations travel from the graphite intercalation compounds to the cathode. The mobility of Li cations is facilitated by the non-protic electrolyte. Much of the current research and development efforts are focused on the development of new anode and cathode materials.

[0004] Since the above reactions occur in the active electrode material, electrons must travel through the active electrode material to reach the current collector. The low electrical conductivity of the active electrode material limits the capacity of lithium ion batteries. Thus, the long distance or path length of the electrons from their location of freedom in the active material to the current collector also hinders efficient charging and discharging processes.

[0005] Accordingly, attempts have been made to reduce the electrical resistance of the active electrode material by incorporating conductive materials, such as carbon nanotubes. These additives are loosely dispersed in the active electrode material, and there is a risk that these materials do not adequately connect the active electrode material to the current collector. As a result, there is a risk that the capacity of a battery doped with carbon nanotubes in the active electrode material is not adequately improved.

[0006] To enhance the connectivity between such conductive additives, the composite of active material with copper or aluminum foil is pressed together with high mechanical force. This increases the conductivity of the composite material and its mass density. However, the mass density is critical for the diffusion of lithium ions from the anode to the cathode and vice versa. A too dense composite material limits the diffusion of lithium ions and impairs the performance of the battery.

[0007] Furthermore, due to the use of conductive additives and binders in the active electrode material, the active electrode material, i.e., the material in which the electrochemical reactions occur, is reduced, which is detrimental to the performance of the battery.

[0008] It is also known that the charging / discharging process is accompanied by a volume change of the active material, which leads to structural aging and capacity loss of the battery during use. Similarly, mechanical deformation can jeopardize the performance of such batteries, so the manufacturing of flexible lithium-ion battery assemblies remains a challenge. Improving the flexibility of the electrodes without affecting the electrode performance would open new applications, but would also be beneficial to the manufacturing process itself. SUMMARY

[0009] The main object of the present invention is to provide a current collector material suitable for improving the battery performance. Another object of the present invention is to provide an electrode material suitable for providing a flexible electrode and battery, which electrode material makes use of a material suitable for improving the battery capacity, while showing a high resistance to degradation due to flexible deformation, and having improved battery charge kinetics and lifetime.

[0010] These objects are met by the method for generating a network of metal fibers, an electrode and a battery according to the independent claims, the network according to each of claims 1 and 16.

[0011] A drawback of using a metal foil, such as a copper foil, as a current collector is that such a current collector makes the battery rigid and vulnerable to damage due to bending and folding. In order to provide a flexible battery assembly, WO 2017 / 222895 Al discloses a porous substrate, on which a suitable electrode material slurry can then be coated. Suitable electrode material slurries include an active material, such as lithium iron phosphate for generating a lithium-ion cathode or lithium titanate for generating a lithium-ion anode, and a conductive additive and a binder in an organic solvent.

[0012] Another electrode for a secondary battery is disclosed in WO 2018 / 048166 Al. The electrode is generated by introducing an electrode mixture containing an active electrode material into the pores of a current collector having a three-dimensional network structure. As an example of this three-dimensional structure, a conductive metal felt is mentioned in WO 2018 / 048166 Al as suitable for use in a flexible battery.

[0013] In the present invention described here, a metal current collector material is utilized according to claim 1 that exhibits an ultra-fine electronic conducting network of metal fibers. The present invention also relates to a method for generating a network of metal fibers, an electrode and a battery according to the independent claims. Surprisingly, the present invention also allows to significantly increase the charge / discharge current without destroying the battery.

[0014] Description of the network of metal fibers and preferred embodiments:

[0015] According to a first aspect of the present application, a network of metal fibers is provided, wherein a plurality of metal fibers are fixed to each other, and wherein the metal fibers have a length of 1.0 mm or more, a width of 100 pm or less, and a thickness of 50 pm or less. The fibers can optionally have a circular or elliptical cross-sectional area with a diameter of less than 100 pm, preferably less than 10 pm. In case of an elliptical cross-section, the diameter referred to is the average diameter. For example, the elliptical cross-section has the shape of an ellipse.

[0016] The network according to the present application is flexible and can be repeatedly deformed without causing a degradation of the network, i.e. without separating individual metal fibers from the network of metal fibers due to the deformation. The metal fibers are fixed to each other such that the metal fibers are in contact with each other, i.e. the contact points are not movable with respect to the metal fibers as in the case of a non-woven mass of entangled metal fibers such as a metal felt. Thus, the network of metal fibers according to the present application is mechanically stable but soft. Mechanically stable in this context means that the network of metal fibers is not a loose mass of metal fibers, i.e. the network does not disintegrate into isolated metal fibers when a small force is acting on the network. Thus, such a network of metal fibers can be flexibly deformed without breaking. The network of metal fibers is able to recover its form after the deformation. However, if the network of metal fibers is folded, it is also possible to permanently reshape its form.

[0017] With metal fibers having a length of 1.0 mm or more, a width of 100 pm or less, and a thickness of 50 pm or less, it is possible to generate a network with metal fibers fixed to each other without the need to heat the metal fibers to a temperature close to their melting point. Traditionally, the manufacture of a network of metal fibers requires higher temperatures. Such higher temperatures are typically close to or above the melting temperature of the metal, thus the material of the metal fibers can be melted or at least softened to some extent such that the metal fibers can form a metal foil instead of the claimed network. Since the network of metal fibers is not a metal foil, i.e. the structure of the metal fibers used to manufacture the network of metal fibers can still be identified in the network of metal fibers. Thus, in a cross-sectional view of the network of metal fibers, there are voids between the metal fibers of the network fibers that are not part of the metal fibers.

[0018] Preferably, the metal fibers show an exothermic event when heated in a DSC measurement before and / or after fixing the metal fibers to each other. An example of such an exothermic event is shown in Figure 6d In other words, the metal fibers are not in their thermodynamic equilibrium at ambient temperature. During heating in a DSC measurement, the metal fibers can for example transition from a metastable state to a thermodynamically more stable condition by crystallization, recrystallization or other relaxation processes that reduce defects in the metal atomic lattice. The exothermic event of the metal fibers when heated, for example observed during a DSC measurement, is preferably a crystallization event.Figure 6d This indicates that the metal fiber is not in thermodynamic equilibrium; for example, the metal fiber may be in an amorphous or nanocrystalline state containing defect energy and / or crystallization energy, which is released during heating of the metal fiber due to crystallization or recrystallization. These events can be identified, for example, using DSC measurements. Figure 6d Surprisingly, it was found that after metal fibers are fixed together, for example by sintering or welding, the network of metal fibers exhibiting this exothermic event has improved strength and electrical conductivity. In the context of this disclosure, the terms "sintering" and "welding" are used interchangeably, i.e., they have the same meaning.

[0019] It should be understood that the network according to the present invention can be obtained by the following method.

[0020] To ensure high electrical conductivity throughout the network, even if the network deforms, it is preferable that the metal fibers are electrically contacted at their fixed points (i.e., contact points). To achieve conductive yet mechanically stable fixation of the metal fibers, it is further preferred that, in the network of the invention, at least some of the plurality of metal fibers are sintered together, i.e., the connection between the metal fibers is formed from the material of the metal fibers. This provides a strong connection between the metal fibers, resulting from the bonding between the metal atoms formed by two contacting metal fibers, and thus leading to a durable yet flexible network with good electrical conductivity. In this regard, it is particularly preferred to sinter the metal fibers onto other metal fibers, most preferably directly onto other metal fibers, without the need for additional adhesives, such as polymeric adhesives. Most preferably, the fixation of one metal fiber to another is achieved through the material of the metal fibers. Therefore, it is further preferred that the metal fibers are fixed together without polymeric adhesives, as such polymeric adhesives typically have poor electrical conductivity and high-temperature performance. By directly sintering the metal fibers together, welding materials, etc., in the network according to the invention can also be omitted.

[0021] It is also preferred to use ultrasonic welding or hammering to fix the metal fibers to each other. Ultrasonic welding and hammering are simple processes that can be used to quickly fix the metal fibers to each other. When using ultrasonic welding or hammering to fix the metal fibers to each other, it is possible to create a network of metal fibers in which the fixation of the metal fibers is not uniform over the entire surface of the network, but is limited to areas that are separated from each other and distributed over the network of metal fibers. For this purpose, it is particularly preferred to configure the compacting tool for ultrasonic welding or hammering. For example, the compacting tool for ultrasonic welding or hammering can have a plurality of protrusions, such as needle-like tines or rims. With such a plurality of protrusions, it is possible to create separate areas in which the metal fibers are fixed to each other with one action. Between these separate areas, the metal fibers can have contact points, but are not fixed to each other. As described above, this can improve the overall flexibility of the network of metal fibers. It is therefore preferred that the network comprises areas in which the metal fibers have contact points, but are not fixed to each other, and that the network comprises areas in which the metal fibers have contact points in which the metal fibers are fixed to each other.

[0022] According to one embodiment, at least some of the plurality of metal fibers are amorphous. According to another embodiment, at least some of the plurality of metal fibers are nanocrystalline. It is also possible to combine amorphous and nanocrystalline metal fibers in the network of metal fibers. Nanocrystalline metal fibers contain crystalline domains. Upon heating to a temperature of about 20-60% of the melting temperature of the nanocrystalline metal fibers, these domains recrystallize, resulting in an increase of the average size of the crystalline domains compared to the average size of the initial crystalline domains in the nanocrystalline metal fibers before heating. It is also possible to mix non-equilibrium (e.g. nanocrystalline or amorphous fibers) with equilibrium (e.g. annealed) fibers.

[0023] As described above, it is preferred that the metal fibers, before and / or after the metal fibers are fixed to each other, show an exothermic event when heated in a DSC measurement. The extent of the exothermic event observed when heating the metal fibers is not particularly limited. Preferably, the exothermic event releases an amount of energy of 0.1 kJ / g or more, more preferably of 0.5 kJ / g or more, even more preferably of 1.0 kJ / g or more, most preferably of 1.5 kJ / g or more. The absolute amount depends very much on the metal or metal alloy used. The extent of the exothermic event can be determined by comparing the DSC measurements of the metal fibers before and after thermal equilibration.

[0024] Amorphous and nanocrystalline metal fibers can be manufactured by melt spinning using the equipment and methods for manufacturing metal filaments by melt spinning, for example as described in the examples disclosed in European patent application no. EP19175749.1, WO2016 / 020493A1 and WO2017 / 042155A1, the contents of which are hereby incorporated by reference with respect to the method of forming and thus obtaining the metal fibers. Thus, the metal fibers can be, for example, Cu, Cu99 Si1, Cu 96 Si4, aluminum, Al 99 Si1, Fe 40 Ni 40 B 20 Metal fibers of Au, Ag, Pb, Si or stainless steel V2A.

[0025] Metal fibers are preferably produced by melt spinning. Due to the rapid cooling applied during the melt spinning process, these metal fibers can contain spatially confined regions of high energy states. Therefore, these metal fibers can be sintered together while maintaining the temperature well below the melting temperature of the metal fibers during the structural transformation that activates these high-energy domains, through which the domains loosen and utilize energy to activate the sintering process. Thus, these metal fibers can be sintered together even at temperatures below the crystallization temperature of the material and far below its melting temperature. This is particularly advantageous if the metal fibers are coated with a high-temperature sensitive coating. Higher temperatures would cause the fiber crystallization to disrupt the amorphous or nanocrystalline state of the fiber, thus risking that these fibers lose their special mechanical properties of high elasticity and low brittleness. The aforementioned domains in the high-energy state can release energy when heated or mechanically pressed by pressing, hammering, or ultrasonic welding. The release of energy in these regions can be observed as an exothermic event.

[0026] The metal fibers are made of or at least contain metal. In this invention, there is no particular limitation on which metals the metal fibers contain or which metals the metal fibers are made of. However, it is preferred that the metal fibers of the network comprise an element selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, cobalt, iron, chromium, vanadium, titanium, aluminum, silicon, lithium, combinations thereof, and alloys comprising one or more of the above. More preferably, the metal fibers of the network comprise an element selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, iron, vanadium, aluminum, silicon, lithium, combinations thereof, and alloys comprising one or more of the above.

[0027] Particularly preferred are metal fibers made of copper, aluminum, or stainless steel alloys. Different types of metal fibers can be combined with each other, such that the network can contain metal fibers made of, for example, copper, one or more stainless steel alloys, and / or aluminum. Networks of metal fibers, wherein the metal fibers are copper, aluminum, cobalt, copper-containing alloys, aluminum, silicon, and / or cobalt, are particularly preferred. An example of an aluminum and cobalt alloy is Al. 99 Si1 and Co 66 Fe4Mo2B 12 Si 16 Examples of copper alloys are CuSi1, CuSi4, or CuSi12.

[0028] It is preferred that the length of the metal fibers is 2.0 mm or more, more preferably 10 mm or more, even more preferably 20 mm or more, even more preferably 70 mm or more. With the length of the metal fibers meeting the above length specifications, the mechanical stability of the network of metal fibers is improved, because due to the increased length of the metal fibers, each metal fiber can have multiple points of contact with other metal fibers of the network, at which the metal fiber is fixed to the respective other metal fibers to form mechanically strong and electrically conductive connections between these metal fibers. Thus, when one of the connections between the metal fibers breaks, this does not compromise the overall structural integrity of the network nor does it separate the metal fibers from the network, because several other connections between the fibers are available to hold the network together and provide the desired electrical conductivity. Preferably, the fiber length should be in the range of 1 to 20 cm, more preferably in the range of 3 to 15 cm, even more preferably in the range of 4 to 8 cm, because it is easy to arrange the fibers by carding.

[0029] It is also preferred if the width of the metal fibers is 80 pm or less, more preferably 70 pm or less, even more preferably 40 pm or less, most preferably 5 pm or less. Furthermore, it is preferred that the thickness of the metal fibers is 50 pm or less, more preferably 30 pm or less, even more preferably 10 pm or less, most preferably 5 pm or less. Instead of a rectangular cross-section of the fibers, it is also possible to have a circular or elliptical cross-section of the dimensions as described above. With the metal fibers showing an exothermic event when heated or mechanically pressed, it is possible to generate the network with the metal fibers fixed to each other without the need to heat the metal fibers to temperatures close to the melting point, i.e. the temperature sensitive coating can be preserved on top of the metal fibers when the fibers are fixed to each other, e.g. by sintering. Furthermore, because the high temperatures for fixing the fibers to each other can be avoided, the risk of the metal fibers transforming into metal foils during the generation of the network can be reduced.

[0030] There is no particular lower limit to the width and thickness of the metal fibers. However, the metal fibers can have a width of not less than 1 pm, preferably not less than 3 pm, and a thickness of not less than 1 pm.

[0031] It is further preferred in the network of metal fibers according to the present application that a majority of the metal fibers are in contact with one or more other metal fibers. This ensures that a high electrical conductivity is provided throughout the network. It is further preferred that the network is a disordered network. Such a disordered network has a good electrical conductivity in every direction. Furthermore, it is easier to generate a network of metal fibers that is disordered compared to an ordered network of fibers. It is further preferred that the optical fibers in the network are combed in different directions to provide directionality of the individual optical fibers, but still allow for a conductivity through the network that is equal in all possible directions. It is therefore preferred that some or all of the optical fibers in the network have an orientation, i.e. the length of the optical fibers is not randomly oriented, but has a predominant orientation in one or more spatial directions.

[0032] It is particularly preferred if the network of metal fibers according to the present application the metal fibers are fixed to each other at contact points that are randomly distributed throughout the network of metal fibers. According to another aspect of the application, it is preferred that the contact points are not randomly distributed, but are for example distributed in a peripheral region of the network of metal fibers, or the metal fibers are ordered such that the contact points are also ordered. It is further preferred that the contact points at which the metal fibers are fixed to each other are located in specific regions and are not evenly provided over the complete network of metal fibers. With the contact points at which the metal fibers are fixed to each other only existing in separate regions, the fibers between these regions can have a high flexibility while at the same time ensuring mechanical stability and a good electrical conductivity.

[0033] It is further preferred if in the network of metal fibers according to the present application the metal fibers are fixed to each other at contact points, wherein the metal fibers are in contact with each other. Preferably, each metal fiber has at least two contact points with other metal fibers, more preferably at least three contact points, even more preferably at least four contact points.

[0034] It is particularly preferred if in the network of metal fibers according to the present application the metal fibers are fixed to each other at contact points, wherein the contact points are distributed throughout the network such that there are contact points throughout the three-dimensional structure of the network of metal fibers. Thus, the contact points are not only provided in specific regions of the network of metal fibers, for example in the center or the circumference of the web. It is possible that the contact points are evenly distributed throughout the network. It is also possible that the density of the contact points throughout the network has a gradient, i.e. the network has regions with a higher density of contact points and regions with a lower density of contact points. It is also possible to have an ordered or random spatial distribution of the contact points.

[0035] The network according to the present application preferably has open pores between the metal fibers. The porosity of the network is preferably up to 95 vol.%. It is also preferred that the porosity of the network is greater than 80 vol.%. It is even more preferred when the porosity is in the range of 80 vol.% to 95 vol.%. It is possible to incorporate active materials into the open pores, for example active electrode materials or active catalyst materials. It is further preferred that in the network according to the present application at least some of the plurality of metal fibers are at least partially coated. The coating can for example be an active material, such as an electrode active material that interacts with lithium ions in a battery or a catalytically active material that is active in the conversion of CO to CO2 or in hydrolysis. It is also possible to coat the metal fibers with a coating that improves the fixation of the metal fibers to each other, thereby increasing the mechanical strength of the network.

[0036] By way of example, such active electrode materials for batteries are: for the anode: graphite, silicon, silicon carbide (SiC) and tin oxide (SnO), tin oxide (Sn02) and lithium titanium oxide (Li4Ti50i2) for the cathode: lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCo02) and lithium iron phosphate (LFP). 12 ) for the cathode: lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCo02) and lithium iron phosphate (LFP).

[0037] It is particularly preferred if the coating comprises an active material for an electrode of a secondary battery. Such a network of metal fibers provided with a coating comprising an active material for a secondary battery electrode can be used to provide a flexible secondary battery with increased capacity. Furthermore, the use of a metal foil as a current collector can be omitted, which not only improves the flexibility of the battery but also reduces the weight of the battery.

[0038] In a further preferred embodiment of the present application, the network of metal fibers has metal fibers coated with a coating comprising at least one catalytically active material. Such a network can be used as a catalyst. In particular, if the network has open pores and the metal fibers are coated with a coating comprising at least one transition metal, a gas or a liquid fluid can flow through the network such that compounds contained in the fluid can come into contact with the coating provided on the metal fibers, whereby a catalytic reaction can take place. Suitable metal alloys can also be used as catalytic materials themselves, for example nickel fibers.

[0039] The catalytically active material can be any material that is capable of catalyzing a chemical reaction. It is particularly preferred that the catalyst material comprises one or more transition metals.

[0040] It is further preferred if in the network according to the present application the plurality of metal fibers forms a network of interconnected pores.

[0041] It is further preferred if the coating provided on the plurality of metal fibers is in electrical contact with the plurality of metal fibers. This is particularly advantageous if the network is used as electrode material for a fuel cell in a hydrolysis or battery. A network comprising metal fibers coated with a coating comprising elements suitable to catalyze the electrochemical reactions occurring at the electrodes of a fuel cell or battery is able to transport electrons to or from the reaction site. Thus, such a network can be used to improve the performance of a fuel cell or battery.

[0042] The thickness of the network of the present application is not particularly limited. However, it is preferred that the network has a thickness of 0.01 mm or more. More preferably, the thickness of the network is 0.03 mm or more, even more preferably 0.05 mm or more, even more preferably 0.07 mm or more, most preferably 0.1 mm or more. If the thickness of the network is less than 0.01 mm, there is a risk that the mechanical stability of the network is insufficient. The upper limit of the thickness of the network is not particularly limited. However, depending on the application, the upper limit can be 3.0 mm or less, or 2.5 mm or less. For battery applications, the most preferred thickness of the network is in the range from 0.1 mm to 0.5 mm. A network having a thickness in this range is advantageous for the stacking and rolling of active material coated networks for the generation of batteries. This also facilitates the diffusion of Li ions within a reasonable time.

[0043] The present application also relates to a network of metal fibers comprising a plurality of metal fibers fixed to each other; wherein the network of metal fibers can be obtained by a process comprising the following steps: a first step of generating a plurality of metal fibers having a length of 1.0 mm or more, a width of 100 pm or less and a thickness of 50 pm or less by subjecting a molten material from which the metal fibers are to be prepared to a cooling rate of 10 2 K x min"1or more; a step 2 of arranging the metal fibers obtained in the step into a loose network of metal fibers; a step 3 of sintering the metal fibers to each other by one of the following processes cl to c4: cl: placing the plurality of metal fibers in a hot press and subjecting the plurality of metal fibers present in the hot press to a predetermined pressure and temperature for a predetermined time period to form contact points by sintering the plurality of metal fibers to each other at which the metal fibers are fixed to each other between the metal fibers, wherein in process cl the pressure is between 0-20 GPa, preferably at least 20 MPa, and the temperature is between 10-95% of the melting temperature of the material of the metal fibers, wherein the melting temperature is determined by DSC measurement; c2: placing the loose network of metal fibers between two heated plates, adjusting the distance between the two heated plates to 0.1 mm to 1 mm and heating the plates to a temperature of 10% to 95% of the melting temperature of the material of the metal fibers, wherein the melting temperature is determined by DSC measurement; c3: ultrasonic welding; c4: hammering.

[0044] In step 1, metal fibers are generated from the melt using controlled lengths of 1 mm or greater. In cases of entangled fibers or insufficiently uniform fiber length, further processing is performed by developing techniques for recycling carbon fibers (Henrik Dommes, “Vom Faserabfure zum hochwertigen Leichtbau Halbzeug”, Light weightDesign 2010, 3, 23-27; doi: 10.1007 / BF03223621). Therefore, they can be cut to the desired length, separated, and partially oriented using a mechanical cutter or by means of a laser.

[0045] In step 2, the metal fibers produced in step 1 either form a liquid dispersion through precipitation or are randomly arranged by an airflow. Figure 27 Step 2, b2). An ordered array of metal fibers is formed through combing. Figure 27 Step 2, b1). In this way, a felt-like structure is generated, as is the case in the standard textile treatment of nonwoven fabrics, for example, by carding.

[0046] Therefore, as a further aspect, the present invention relates to a method for generating a network of metal fibers having welded or sintered contacts between the fibers. The invention includes steps 1 and 2 of providing a plurality of metal fibers and a network, and step 3 of interconnecting the filaments to form a consolidated porous nonwoven felt-like structure.

[0047] In step 3 ( Figure 27 In step 3), the loose felt of disordered metal wires (also known as a loose network of metal fibers) obtained in steps 1 and 2 undergoes one of the treatments c1 to c4. For example, it is placed in a hot press ( Figure 27, step 3, c1, c2) and subjected to a predetermined pressure and temperature for a predetermined period of time to generate the network by welding the metal fibers at their points of contact to form a cross-linked metal fiber network. The plurality of metal fibers present in the hot press is subjected to a predetermined pressure and temperature for a predetermined period of time to generate the network by sintering the plurality of metal fibers to each other to form points of contact between the metal fibers, wherein the pressure is between 0 and 2 GPa, preferably at least 20 MPa, and the temperature is between 10% and 95% of the melting temperature of the material of the metal fibers, wherein the melting temperature is determined by DSC measurement, for example by monitoring the recrystallization temperature. Based on the DSC measurement, the skilled person is able to determine the appropriate temperature to sinter the metal fibers to each other in step 3. The skilled person understands that the features related to steps 1 to 3 can be combined with the features related to steps 1 to 3 described below and in the claims as well as with all features described above, the features related to the metal fiber network described below and in the claims.

[0048] In the processing c2 of step 3, when adjusting the distance between the heating plates, it is preferred to compact the loose network of metal fibers to generate points of contact between the metal fibers.

[0049] In a further embodiment of step 3, if the compacting tool is equipped with a structured contact surface, for example protrusions such as needle-like tines opposed to a flat surface or an edge pattern, the network structure can be tailored with different length scales Figure 27 , step 3, c3, c4; Figure 27 not shown in c2). In this case, the distance between the fiber chains is controlled by the density of the fibers in the area of the tool or its protrusions compressing the felt, but at the points of contact of the metal fibers where the compression tool does not exert to the network or the compacting tool does not have protrusions, no weld points will be formed at the points of contact of the metal fibers. With this tool structure, the average porosity and flexibility of the network of metal fibers can be improved.

[0050] Preferably, the fiber length should be in the range of 1 cm to 20 cm, more preferably in the range of 3 cm to 15 cm, even more preferably in the range of 4 cm to 8 cm. For fibers having a length as described above, the fibers can easily be arranged by carding.

[0051] In an improved procedure, if the wires are welded by hammering impacts instead of continuous compression of the wires, the temperature to weld the wires to the consolidated felt, i.e. the network according to the present invention, can be reduced, wherein the shock wave can reach significantly higher peak pressures connected to local heating Figure 27 , step 3, c4). This hammering impact can be applied in the form of ultrasound, i.e. ultrasonic welding, wherein the oscillations are in a direction perpendicular to the felt Figure 27In case of welding by hammering impacts or by ultrasound, as mentioned above, preferably the compacting tool is equipped with a structured surface having a plurality of protrusions, such as needle-like tines or edges. As mentioned above, such a structured compacting tool can be used to generate a network according to the present application in which the contact points of the metal fibers that are fixed to each other are only in a plurality of separate areas, such that between such separate areas the metal fibers can have contact points that are however not fixed to each other. The areas in which the metal fibers are not fixed to each other can improve the porosity and can also increase the flexibility of the metal fiber network.

[0052] It is further preferred that each area in which the metal fibers are fixed to each other and / or each area in which the metal fibers are not fixed to each other has a size of at least 1 mm 2 , more preferably at least 2 mm 2 , and even more preferably at least 5 mm 2 . It is further preferred that, in particular, each area in which the metal fibers are fixed to each other and / or each area in which the metal fibers are not fixed to each other has a size of at least 1 mm 2 , wherein the areas in which the metal fibers are fixed to each other form island structures that are surrounded by sea-like areas in which the metal fibers are not fixed to each other. Alternatively, it is also preferred that, in particular, when each area in which the metal fibers are not fixed to each other and / or each area in which the metal fibers are fixed to each other has a size of at least 1 mm 2 , the areas in which the metal fibers are not fixed to each other form island structures that are surrounded by sea-like areas in which the metal fibers are fixed to each other.

[0053] All processes cl to c4 have in common that the fibers as a whole remain significantly below the melting temperature and are only sintered at their contact points. This can ensure that the fiber structure does not collapse. In all cases, the fact that the rapidly cooled fibers obtained by, for example, melt spinning are not in their thermal equilibrium and contain amorphous and / or nanocrystalline domains, in which atoms can be rearranged more easily than in balanced crystalline domains, improves and mitigates the welding of the contacts between the different filaments.

[0054] In the method according to the application, the pressure applied in the treatment cl allows to maintain a temperature significantly lower than the melting temperature of the metallic fiber material, while at the same time creating a strong bond between the metallic fibers to create a stable network of metallic fibers. In all treatments cl to c4 of the method according to the application, the atomic diffusion induced by thermal energy remains low, while the atomic diffusion induced by mechanical pressure increases. This mechanism allows it to create a stable network of metallic fibers that are permanently sintered together at low cost and without the need for careful control of the applied temperature. If the temperature is higher than 95% of the melting temperature of the metallic fiber material, there is a risk of the metallic fibers transforming into a metallic foil. On the other hand, if the temperature is lower than 10% of the melting temperature of the metallic fiber material, the mobility of the atoms is so low that in this method the metallic fibers are not sintered together sufficiently to provide a stable network of metallic fibers or take too much time.

[0055] In the context of the description of the application, the "%" of the melting point refers to the melting point in °C. Thus, if the melting point is 1000 °C, in the context of the description of the application, 20% of the melting point is 200 °C, 50% of the melting point is 500 °C and 95% of the melting point is 950 °C.

[0056] It will be understood that all aspects of the above described metallic fiber network, in particular the aspects related to the metallic fibers, constitute preferred embodiments also in view of the method according to the application.

[0057] In the method according to the application, it is preferred if the metallic fibers provided have a length in the range of 1 cm to 20 cm, more preferably in the range of 3 cm to 15 cm, even more preferably in the range of 4 cm to 8 cm, have a width of 100 pm or less, have a thickness of 50 pm or less, or have a circular or elliptical cross-section. In relation to the length, width and thickness of the metallic fibers, it will be understood that the same dimensions indicated above for the description of the network are also preferred in the method according to the application. It is observed that such fibers can be used to generate a stable network of metallic fibers without the need to heat the metallic fibers to their melting temperature.

[0058] In the method according to the application, the applied temperature depends on the material of the metallic fibers. In order to avoid crystallization of amorphous metallic fibers during the welding process, it is preferred to keep the applied temperature below the crystallization temperature of these fibers. For the metallic fibers to be tested, the crystallization temperature can be determined by differential scanning calorimetry (DSC). The DSC measurement is carried out using the following conditions: starting temperature 30 °C, heating rate of 10 K min -1 up to 1200 °C, continue with a cooling rate of 10 K min -1 up to room temperature. The constant argon flow is 100 milliliter min-1 DSC measurements were performed in a zirconium-oxygen-trap system under an argon atmosphere and a completely oxygen-free atmosphere (STA 449 F3 Jupiter, Netzsch Bj. 2017).

[0059] In the method according to the application, the time during which the metal fibers are subjected to the predetermined temperature and pressure is not particularly limited and depends on the material of the metal fibers, the applied pressure and temperature. However, in order to ensure that the metal fibers are sufficiently sintered together, it is preferred that the predetermined time in the treatment cl and c2 is 10 seconds or more, more preferably 1 minute or more, even more preferably 2 minutes or more, even more preferably 3 minutes or more and most preferably 5 minutes or more. The upper limit of the time during which the metal fibers in step b) are subjected to the predetermined temperature and pressure is not particularly limited. However, from an economic point of view, it is preferred if the time is 60 minutes or less, even more preferably 45 minutes or less, most preferably 30 minutes or less.

[0060] In order to ensure a stable connection between the metal fibers throughout the network, it is preferred if the pressure and heat in the treatment cl are applied for at least one minute.

[0061] It is preferred that the pressure applied in the processes cl and c2 is 20 MPa or more, more preferably 30 MPa or more, even more preferably 100 MPa or more, most preferably 120 MPa or more. Depending on the metal alloy and the melt spinning process, it is also possible to reduce the applied pressure. The upper limit of the pressure is not particularly limited. However, in order to avoid transforming the metal fibers into a metal foil, the pressure is preferably 1000 MPa or less, more preferably 750 MPa or less, even more preferably 500 MPa or less, most preferably 300 MPa or less.

[0062] In order to generate a network comprising coated metal fibers, it is in principle possible to provide the coated metal fibers after step 1 or 2 or to perform step 4 of coating the metal fibers, wherein step 4 is preferably performed after step 3. Performing step 4 after the sintering in step 3 allows to create a basic network for many applications. In a subsequent step 4, the network can then be modified for the intended application by providing a suitable coating on the metal fibers. Furthermore, performing step 4 after step 3 allows to provide a coating on the metal fibers which will be susceptible to the conditions applied during the sintering and / or welding in step 3. This is for example the case if the coating has a low melting point such that subjecting the coating to the conditions in step 3 would melt the coating.

[0063] In the method according to the application, it is further preferred if the metal fibers are generated by melt spinning. Due to the application of a rapid cooling during melt spinning, such metal fibers generated by melt spinning can contain spatially confined domains in a high-energy state. In this regard, rapid cooling means a cooling rate of 102K min -1 or more, preferably 104K min -1 or more, more preferably a cooling rate of 105K min -1 or more. Thus, it is possible to sinter such metal fibers together while keeping the temperature in step 3 far below the melting temperature of the metal fiber. It is even possible to sinter such metal fibers together at a temperature below the crystallization temperature of the metal fiber material. This is particularly advantageous if the metal fibers are coated with a coating which is sensitive to high temperatures. In view of the above, it is preferred that the metal fibers of the metal fiber web according to the application can be obtained by subjecting the molten material of the metal fibers to a cooling rate of 102K min -1 or more by melt spinning.

[0064] It is preferred if, in the method according to the application, the temperature applied in step 3 is 80% or less, more preferably 70% or less, even more preferably 60% or less, most preferably 50% or less of the melting temperature of the metal fiber material. It is even possible that the temperature applied in step 3 is 25% or less of the melting temperature of the metal fiber material. By keeping the temperature in step 3 below these limits, the risk of transforming the metal fibers into a metal foil is reduced. The temperature is preferably 10% or more, more preferably 20% or more, even more preferably 25% or more, most preferably 30% or more of the melting temperature of the metal fiber material. If the temperature in step 3 is below these limits, the risk of not being able to sufficiently sinter the metal fibers together to provide a stable network of metal fibers increases due to the reduction of the mobility of the atoms of the metal fibers. However, the lower limit depends on the metal or metal alloy and can thus be even below 20% of the melting temperature.

[0065] In the method of the present invention, amorphous metal fibers can be used. If amorphous metal fibers are used, it is preferable to keep the temperature in step b) below the crystallization temperature. The crystallization temperature can be determined by differential scanning calorimetry (DSC). More preferably, if amorphous metal fibers are used, the temperature is preferably 50% or lower of the crystallization temperature of the metal fiber material, more preferably 50% or lower, more preferably 35% or lower, even more preferably 30% or lower, and most preferably 20% or lower. However, if amorphous metal fibers are used, the temperature may preferably be 95% or lower, more preferably 90% or lower, even more preferably 85% or lower, and most preferably 80% or lower.

[0066] In the context of this invention, "% of crystallization temperature" refers to the crystallization temperature in °C as determined by differential scanning calorimetry (DSC). Therefore, if the crystallization temperature is 1000 °C, in this invention, 20% of the crystallization temperature is 200 °C, 50% is 500 °C, and 95% is 950 °C.

[0067] A further preferred embodiment is that, in the method for generating the metal fiber network, a step is performed to at least partially utilize an active material, particularly an active electrode material or catalyst material, to fill the voids between the metal fibers in the network. Figure 1a The diagram schematically illustrates the steps of filling the gaps between metal fibers.

[0068] After the metal fiber network is manufactured by the method of the present invention, it is particularly preferable to cut the metal fiber network into a shape suitable for the desired application. Cutting can be performed before or after the coating step, and also if no coating step is intended. If cutting is performed after the metal fiber network is formed, this cutting facilitates the generation of a metal fiber network in the desired shape.

[0069] Description and preferred embodiments of electrodes comprising a network of metal fibers:

[0070] Another aspect of the invention relates to an electrode comprising the network described above, preferably manufactured or obtained by the method described above. Particularly preferred is that the network of metal fibers forming part of the electrode has been separated from the network described above, for example, by cutting.

[0071] If the electrode contains a network as a collector, it is particularly preferred.

[0072] In the electrode according to the invention, it is further preferred that the gaps between the metal fibers in the network are at least partially filled with active material, particularly active electrode material or catalyst material.

[0073] Description and preferred embodiments of a battery including electrodes comprising a network of metal fibers:

[0074] Another aspect of the invention relates to a battery including electrodes, such as those described above. At least one electrode in the battery is a cathode (positive electrode) and / or at least one electrode is an anode (negative electrode). The terms anode and cathode refer to the electrodes when the battery is discharging.

[0075] The porous structure of the metal fiber network provides a relatively large volume that can be occupied by the active electrode material and is not present in, for example, commonly used metal foils. Therefore, the amount of active electrode material can be significantly increased without compromising capacity due to the increased resistance caused by the high amount of active electrode material. Furthermore, by using the metal fiber network as described above, the active material is distributed throughout the current collector. Therefore, electrons must only overcome the short distance between the active material and the current collector. Since the conductivity and connectivity of the active material and the electrode are generally high, it is not necessary to press the electrode material as much as in the case of metal foil used as an electrode, thus enhancing lithium-ion diffusion. As a result, the battery charging time can be significantly reduced, and the use of additives such as carbon black and binders can also be reduced, allowing more active material to be incorporated into the battery electrodes, further improving battery performance. The flexibility and stability of the metal fiber network allow for the manufacture of durable electrodes, thus resulting in increased battery life. Furthermore, due to the three-dimensional nature of the metal network penetrating the active electrode material, batteries using electrodes according to the invention have improved battery charging kinetics. This allows electrons and charge carriers to migrate a short distance from their origin in the active material to the metal current collector, from which electrons and charge carriers are distributed throughout the circuit.

[0076] If the battery according to the invention is a rechargeable battery, more preferably a lithium-ion battery, it is preferred. The network is a network of copper metal fibers or copper alloy fibers, such as Cu. 99 Si1, Cu 98 Si2, Cu 96 Si4, Cu 88 Si 12 or Cu 92 Sn8, or a network of aluminum metal fibers or aluminum alloy fibers, such as Al 99 Si1 is also preferred. Compared to pure metals, copper and aluminum alloys offer better manufacturing conditions for melt-spun fibers, while exhibiting nearly equal conductivity.

[0077] It is also preferred to provide a network of metal fibers, wherein the metal fibers are made of aluminum for the cathode of a secondary battery or of copper for the anode of a secondary battery. Such a network can be infiltrated with a lithium active material and used for an electrode. In this case as well, the distance between the current collector and the active material can be reduced, which is advantageous for the performance of the battery.

[0078] Therefore, it is particularly preferred if the battery according to the present application comprises an electrode comprising a network of metal fibers of copper or a copper alloy. It is also particularly preferred if the battery according to the present application comprises an electrode comprising a network of metal fibers of aluminum or an aluminum alloy. It is also particularly preferred if the battery according to the present application comprises a first electrode comprising a network of metal fibers of copper or a copper alloy and a second electrode comprising a network of metal fibers of aluminum or an aluminum alloy. It is also possible to use two or more electrodes of the same or different metal fiber material.

[0079] In the present disclosure, the focus is on networks of metal fibers and their use as electrode material. However, it is also preferred to use the network of metal fibers as described herein in catalytic materials, in fuel cells, in hydrolysis, as a component in electromagnetic shielding materials, as filters, in polymer composites or as tissue materials and tissue hybrid materials which can also comprise tissue materials as additives, such as cotton, silk or wool. BRIEF DESCRIPTION OF DRAWINGS

[0080] The present application will now be described in further detail by way of example only with reference to the drawings and the accompanying drawings and by various examples of the network and method of the present application. Shown in the drawings are:

[0081] Figure 1b ) is a schematic drawing of a vertical melt spinning device.

[0082] Figure 1c ) is a schematic drawing of a horizontal melt spinning device.

[0083] Figure 2a ) is a photographic image taken from an image of melt deposition of Al 99 Si1 alloy onto a rotating wheel.

[0084] Figure 2b ) is a photographic image of copper metal fibers.

[0085] Figure 2c ) is a photographic image of cobalt metal fibers.

[0086] Figure 2d ) is a photographic image of metal fibers of Al 99 Si1 alloy.

[0087] Figure 4a ) is a photographic image of Co 66 Fe4Mo2B 12 Si16 Photographic images of metal fibres of the alloy.

[0088] Figure 3a) i) is a photographic image of Co 66 Fe4Mo2B 12 Si 16 Photographic images of metal fibres of the alloy, ii) shows Co 66 Fe4Mo2B 12 Si 16 Average thickness of metal fibres of the alloy, iii) shows Co 66 Fe4Mo2B 12 Si 16 Average width of metal fibres of the alloy.

[0089] Figure 3b) i) is a photographic image of Co 66 Fe4Mo2B 12 Si 16 Photographic images of metal fibres of the alloy, ii) shows Co 66 Fe4Mo2B 12 Si 16 Average thickness of metal fibres of the alloy, iii) shows Co 66 Fe4Mo2B 12 Si 16 Average width of metal fibres of the alloy.

[0090] Figure 4b is an X-ray diffraction pattern of copper metal fibres.

[0091] Figure 4c is an X-ray diffraction pattern of Al 99 Si1metal fibres of the alloy.

[0092] Figure 5a is an X-ray diffraction pattern of Co 66 Fe4Mo2B 12 Si 16 X-ray diffraction pattern of metal fibres of the alloy.

[0093] Figure 5b is a scanning electron micrograph (SEM) of copper metal fibres.

[0094] Figure 5a is a magnified view of Figure 5c ).

[0095] Figure 5d is a scanning electron micrograph of Al 99 Si1metal fibres of the alloy.

[0096] Figure 5c ) is Figure 5e ) is a magnified view of

[0097] Figure 5f ) is Al 99 Further scanning electron micrograph of Si1 alloy metal fibers.

[0098] Figure 5g ) is a scanning electron micrograph of gold metal fibers

[0099] Figure 5h ) is Cu 92 Scanning electron micrograph of Sn8 alloy metal fibers.

[0100] Figure 6a ) is Cu 96 Scanning electron micrograph of Si4 alloy metal fibers.

[0101] Figure 6b ) are 527 Al 99 Thickness and width of Si1 alloy metal fibers.

[0102] Figure 6c ) are 527 Al 99 Distribution of thickness of Si1 alloy metal fibers.

[0103] Figure 6d ) are 527 Al 99 Distribution of width of Si1 alloy metal fibers.

[0104] Figure 7 ) DSC measurement of CuSn8 microfibers after melt spinning (curve I) and after thermal equilibration of the same microfibers (curve II) demonstrating the exothermic process in case of heating the melt spun fibers compared to the equilibrated metal fibers.

[0105] Figure 8 is sintered Co 66 Fe4Mo2B 12 Si 16 SEM image of a network of alloy metal fibers according to the present application (network of example 2).

[0106] Figure 9 is sintered Co 66 Fe4Mo2B 12 Si 16 Photo image of a network of alloy metal fibers according to the present application.

[0107] Figure 8 is Figure 10A photographic image of a network in a deformed state.

[0108] Figure 11 The image shows a photographic image of a copper metal fiber network according to the present invention (network of Example 9) sintered at 300°C and 177 MPa for 5 minutes.

[0109] Figure 12 The image shows a photographic image of a copper metal fiber network according to the present invention (network of Example 10) sintered at 300°C and 177 MPa for 3 minutes.

[0110] Figure 11 yes Figure 13 The SEM image of the network shown.

[0111] Figure 11 Figure 12 and Figure 14a The enlarged SEM image of the network shown.

[0112] Figure 14b Cu was sintered at 300℃ and 78MPa for 3 minutes. 92 Photograph of the network of Sn8 alloy metal fibers according to the present invention (network of Example 11).

[0113] Figure 14a ) Figure 14c SEM image of the network.

[0114] Figure 14b ) Figure 15 The image shows a magnified SEM image of the network.

[0115] Figure 16a This is a schematic diagram of hot pressing.

[0116] Figure 16b ( ) is a schematic diagram of a battery according to the present invention.

[0117] Figure 17 ( ) is a schematic diagram of a reference battery based on existing technology.

[0118] Figure 18 This is a comparison of the capacity of the battery according to the present invention with that of a reference battery according to the prior art.

[0119] Figure 19 It is a charge-discharge curve of a reference battery obtained through chronopotentiometry.

[0120] Figure 20a This is a curve showing the charging and discharging distribution of the invented network battery, obtained through the time-potential method.

[0121] Figure 18 ) through such Figure 20b The graphs shown are the second and last charge-discharge distribution curves of the reference battery obtained by the chronopotential method.

[0122] Figure 19 ) through such Figure 21a The graphs showing the second and last charge-discharge distributions of the network battery of the present invention obtained by the chronopotential measurement method are shown.

[0123] Figure 21b The graph shows the charging and discharging distribution of the network battery of the present invention and a reference battery with current normalization time obtained by the time-potential method.

[0124] Figure 21a )yes Figure 21c This is an enlarged view of the curve for the first cycle.

[0125] Figure 21a )yes Figure 22 An enlarged view of the curves showing the area around the last cycle of the reference battery.

[0126] Figure 23 This is a graph showing the capacity of the network battery and reference electrode of the present invention as a function of the number of cycles.

[0127] Figure 23 a) is a SEM image of the electrode of the present invention, showing graphite sheets within a fiber network.

[0128] Figure 23 b) is Figure 23 EDX mapping of copper for the electrode of the present invention shown in Figure a.

[0129] Figure 23 c) is Figure 24 EDX mapping of carbon in the electrode of the present invention is shown in figure a.

[0130] Figure 25 This is an example of a combing machine solution for forming metallic fluff.

[0131] Figure 26 Photographs of the manufacturing method according to the present invention, wherein metal fibers are formed into fluff and combined with cotton fluff.

[0132] Figure 27 It is a copper-based fluff that is mechanically stabilized through ultrasonic treatment.

[0133] Figure 1a This is a schematic representation of the process according to the present invention. Detailed Implementation

[0134] For clarity, some figures do not show reference numerals or not all reference numerals are shown.

[0135] Figure 1b ) shows a schematic view of a melt spinning device 1 that can be used to generate metal fibers 2 suitable for forming a network according to the present application. The melt spinning device 1 has a vertical rotating wheel 3 that can be rotated around an axis Z. Above the rotating wheel 3 a microstructured nozzle 4 is arranged through which droplets 5 of a melt of a material from which the metal fibers 2 are generated can be deposited onto the rotating wheel 3. Alternatively, a horizontal melt spinner can be used Figure 1b A horizontal melt spinner is disclosed in European patent application with the application number EP19175749.1, the content of which is incorporated herein by reference.

[0136] Figure 1a ) shows a schematic view of a horizontal melt spinning device 1 that can also be used to form metal fibers 2. In contrast to the melt spinning device 1 shown in Figure 1b ) the melt spinning device 1 shown in Figure 1a ) has a horizontally rotating wheel 3. Similar to the melt spinning device 1 shown in Figure 1b ) the melt spinning device 1 shown in Figure 1c ) the melt spinning device 1 has a horizontally rotating wheel 3. Similar to the melt spinning device 1 shown in

[0137] Figure 2a ) shows a photographic image of the generation of Al 99 Si1 alloy metal fibers. The photographic image shows the Al 99 Si1 alloy melt being deposited onto the rotating wheel 3 and is separated from the footage taken at 40000 fps of the metal melt being deposited onto the rotating wheel 3 of the melt spinning device 1. The rotating wheel 3 is located in the lower part and the microstructured nozzle 4 is located in the upper part of the photographic image shown in Fig. 1C. The temperature of the melt is set in the range of 50 °C to 300 °C above the melt temperature (higher processing temperatures are possible). The melt forms a metal stream that wets the rotating wheel 3 and is rapidly cooled to form metal fibers 2 from the metal stream 5.

[0138] In Figure 1a ) to d) photographic images of copper metal fibers ( Figure 2a ) generated and collected using the melt spinning device 1 shown in Figure 2b ) and b), of cobalt metal fibers ( Figure 2c ) and of Al 99 Si1 alloy metal fibers ( Figure 4a ) and Co 66 Fe4Mo2B 12 Si 16Photograph of alloy metal fibers. Metal fibers 2 form an entangled network of metal fibers 2, wherein the metal fibers 2 are not fixed to each other, so that individual metal fibers 2 can be easily separated from the entangled network of metal fibers 2.

[0139] Co 66 Fe4Mo2B 12 Si 16 Further photographic images of the alloy metal fibers are shown in Figures 3a) and 3b). The fibers were produced using wheel speeds of 50 m / s and 25 m / s, respectively. 66 Fe4Mo2B 12 Si 16 Photographs of alloy metal fiber 2. As can be seen from the corresponding thickness and width distributions also shown in Figures 3a) and 3b), the higher wheel speed of 50 m / s results in metal fiber 2 with reduced thickness and width (see Figure 3a) compared to metal fiber 2 produced using a wheel speed of 25 m / s (see Figure 3b).

[0140] Bruker D8 forward XRD recording using a cobalt source in Brugg-Bretano mode with 30mA and 40kV anode current and accelerating voltage. Figure 4c to Figure 4a The X-ray diffraction spectrum is shown. Data were collected using a Bruker VANTEC-1 detector and measurements were taken in air. Metallic copper fiber 2 (see...) Figure 4b )) and Al 99 Si1 alloy metal fiber 2 (see Figure 4c The sharp peak 20 observable at a specific angle indicates that these metal fibers 2 are polycrystalline, while Co... 66 Fe4Mo2B 12 Si 16 Alloy metal fiber 2 (see Figure 5a The absence of peak 22 extending over a relatively large angular range, i.e., the absence of such sharp peak 20, indicates that these metal fibers 2 are amorphous.

[0141] Scanning electron micrographs of copper fiber 2 in Figure 5a The photomicrographs are shown in (a) and (b). The photomicrographs were recorded on a Zeiss Ultra55 with an accelerating voltage of 3 kV. Figure 5b The scale bar in the lower left corner indicates a length of 100 μm, and... Figure 5a The scale bar in the lower left corner indicates a length of 2 μm. From Figure 5a The micrographs show that the metal fibers 2 are not fixed to each other and form an entangled network, but can move relative to each other, allowing individual metal fibers 2 to be easily separated from the entangled network. Figure 5aThe micrographs also reveal that the metal fiber 2 has a substantially constant width over a length of millimeters. In fact, although from... Figure 5a While not visible in (a) and (b), the width and thickness of the copper fibers remain essentially constant over a length of several centimeters. Figure 5c Similar to the scanning electron micrographs shown in (a) and (b), in Al 99 Recorded on Si1 alloy metal fiber 2 Figure 5c Other scanning electron micrographs shown in 1) and d) Figure 5d The scale bar in the lower left corner indicates a length of 100 μm, while Figure 5c The scale bar in the lower left corner indicates a length of 10 μm. It can be recognized that Al 99 Si1 alloy metal fibers 2 form an entangled network, wherein the metal fibers 2 are not fixed to each other. The thickness and width of these metal fibers 2 are also substantially constant over a length of millimeters. In fact, although from Figure 5e ) and d) are not visible, Al 99 The width and thickness of the Si1 alloy metal fiber 2 are also basically constant over a length of several centimeters. Figure 5e Al was shown 99 Another scanning electron micrograph of Si1 alloy metal fiber 2. Figure 5e The scale bar in the lower left corner indicates a length of 3 μm. Figure 5f In the micrographs shown, nanocrystalline domains can be identified as a grain structure. Scanning electron micrographs of gold metal fibers 2 are shown in... Figure 5f As shown in the figure. Figure 5f The scale bar in the lower left corner indicates a length of 10 μm. Figure 5g In the micrograph shown, nanodomains can be identified as a grain structure. Figure 5g In the image, Cu is shown. 92 Scanning electron micrograph of Sn8 alloy metal fiber 2. Figure 5g The scale bar in the lower left corner indicates a length of 1 μm. Similarly, in... Figure 5h Nanodomains can be identified in the micrograph shown. Nanodomains can also be found in Cu produced by melt spinning. 96 Si4 alloy metal fibers 2 can be found, such as those that can be found in Si4 alloy metal fibers 2. Figure 5h The grain structure of this fiber 2, as shown in the scanning electron micrograph, is identified. Figure 6a The scale bar in the lower left corner of the image indicates a length of 1 μm.

[0142] 527 Al atoms manufactured using a wheel speed of 25 m / s 99 The thickness and width of Si1 alloy metal fibers 2 are in Figure 6b The figure shows the corresponding thickness and width distributions. Figure 6aAs shown in the diagram for 6c. From Figure 6b )and Figure 6b It can be seen that Al 99 The thickness of the Si1 alloy metal fibers ranges from 3 to 17 μm, with an average thickness of 8.5 μm. The thickness distribution follows a narrow Gaussian function, such as... Figure 6d The lines in the diagram indicate the width of the metal fibers, which range from 5 to 80 μm, with an average width of 39.5 μm and a median width of 35.0 μm. Figure 6d The image shows two DSC measurements. Figure 6d Curve I in the figure was obtained directly from CuSn8 microfibers after melt spinning, and Figure 7 Curve II in the figure was obtained after the same microfibers reached thermal equilibrium. This demonstrates the exothermic treatment in the case of heated melt-spun fibers compared to the equilibrium of metal fibers.

[0143] Figure 7 The image shows a scanning electron microscope image of the network 6 of the metal fiber 2 according to the present invention. Figure 7 The scale bar in the lower left corner indicates a length of 20 μm. Figure 5a Metal fiber 2 in network 6 is Co 66 Fe4Mo2B 12 Si 16 Amorphous metal fibers of alloy 2. With, for example, in Figure 7 In contrast to the entangled network of metal fibers 2 shown in the scanning electron micrographs of (c) or (d), the network is as follows: Figure 7 to Figure 9 In the network 6 of metal fibers 2 shown, the metal fibers 2 are fixed to each other at contact points 7, wherein the metal fibers 2 are sintered together. Because the metal fibers are sintered together and fixed to each other, it is impossible to move these metal fibers 2 relative to each other and one of the metal fibers 2 will be separated from the network 6 without breaking the contact points 7.

[0144] from Figure 7 It can be seen that the network 6 of the metal fibers 2 according to the present invention has gaps 9 in the form of pores between the metal fibers 2. For a better overview, Figure 8 Only some of the metal fibers 2, contact points 7, and gaps 9 are indicated by reference numerals in the attached diagram. Figure 9 and Figure 8 The reference numerals for the gap 9 and the contact point 7 are omitted, and only part of the metal fiber 2 is indicated by reference numerals.

[0145] exist Figure 8 and 9 In the middle, Co is shown 66 Fe4Mo2B 12 Si 16A photographic image of another network 6 of amorphous metal fibers 2 of an alloy. From these photographic images it can be seen that the network 6 can be held with tweezers 8 without separating the metal fibers 2 from the network 6 of metal fibers 2 and that the network 6 is a disordered network 6, i.e. the metal fibers 2 do not have a preferred orientation but are randomly oriented.

[0146] Figure 9 and 9 A photographic image of the same network 6 of metal fibers 2 is shown. In Figure 8 the network 6 generated after is held by tweezers 8. From Figure 9 it can be seen that the network 6 can be bent and the metal fibers 2 still are fixed to each other and not separated from the network 6 of metal fibers 2.

[0147] Furthermore, from Figure 10 and Figure 10 it can be seen that the network 6 of metal fibers 2 has a porous structure with interconnected pores extending throughout the network of metal fibers. The contact points 7 between the metal fibers 2 are randomly distributed throughout the network 6 of metal fibers 2.

[0148] A photographic image of a network 6 of metal fibers 2 of copper is shown in Figure 11 and 11 . Figure 11 The generation of the network 6 shown is described below as example 9 and Figure 10 the generation of the network 6 shown is described below as example 10. Thus, compared to the network 6 shown in Figure 10 the network 6 shown in Figure 10 is generated at a higher temperature. While both networks 6 show voids 9 in the form of pores distributed throughout the network 6, in the network 6 shown in Figure 11 the density of pores, i.e. the number of pores per surface area, is lower at the center of the network 6 and increases towards the edges of the network 6. For a better overview, the reference signs for the metal fibers 2, the contact points 7 and the voids 9 are omitted in Figure 11 and Figure 10 .

[0149] In the network 6 shown in Figure 10 compared to the distribution of voids 9 in the network 6 shown in Figure 11 the voids 9 in the form of pores are more evenly distributed throughout the network 6 of metal fibers 2. Possibly due to the higher processing temperature used for generating the network 6 shown in Figure 11 a fracture of the metal fibers 6 into metal foils occurs. This is almost completely avoided by lowering the processing temperature as found for the network 6 shown in Figure 12 .

[0150] Figure 12 A scanning electron micrograph of the network is shown inFigure 13 and 13 As shown in the figure. The recording of scanning electron micrographs was performed in a similar manner to the recording of other scanning electron micrographs described above. Figure 12 The scale bar in the lower left corner indicates a length of 200 μm, and Figure 15 The scale bar in the lower left corner indicates a length of 100 μm. From these scanning electron micrographs, it can be seen that the structure of the copper fibers 2 is conservative, and the fibers 2 are sintered together at the contact points 7, so that they are no longer merely forming an entangled network but are fixed together, making it impossible to easily separate individual fibers 2 from the network 6. It can also be seen that voids 9 in the form of pores extend through the network 6 of the fibers 2, and the contact points 7 are randomly distributed throughout the network 6. Figure 14a and 13 The striations visible in the scanning electron micrographs originate from the hot-melt alloy discs used to generate the network 6 of the metal fibers 2, as described in the following example. These hot-melt alloy discs are cut and therefore have very fine grooves (not shown) on their surface, which are... Figure 14a The diagram schematically illustrates the use of a hot press 10 to press the metal fibers onto a network during production.

[0151] Figure 14a This shows another photographic image of a network 6 of metal fibers 2 according to the present invention. In this network 6 of metal fibers 2, the metal fibers are made of Cu 92 Made of Sn8 alloy. Figure 14a The generation of network 6 shown in the diagram is described below as Example 11. Figure 14a In the network 6 shown, voids 9 in the form of holes are distributed throughout the network 6. Network 6 is a disordered network 6, meaning the metal fibers 2 do not have a preferred orientation but are randomly oriented, wherein the metal fibers 2 are fixed to each other at contact points 7, and wherein the metal fibers 2 are sintered together. For a better overview, in Figure 14b) The reference numerals for contact point 7 and gap 9 are omitted in the attached diagram. Figure 14a Only a portion of the metal fibers 2 are indicated by reference numerals in the attached diagram. Metal fibers 2, contact points 7, and gaps 9 can be obtained from... Figure 14b and 14c) Identified from SEM images, these SEM images are from Figure 14c The image was taken from Network 6 as shown in the image. Figure 14c The scale bar in the lower left corner indicates a length of 100 μm, and Figure 14b The scale bar in the lower left corner indicates a length of 20 μm. Figure 15The enlarged view provided in Fig. 7 shows that at the contact points 7 more than two metal fibers 2 can be sintered together, so that at a single contact point 7 multiple metal fibers 2 can be fixed to each other due to sintering. For a better overview, in Figure 12 and 14c only some metal fibers 2, contact points 7 and voids 9 are indicated by reference numerals.

[0152] Figure 16a) A schematic view of a hot press 10 is shown, which can be used to generate a network 6 of metal fibers 2 according to the present application. The hot press 10 is provided with an upper part 11 and a lower part 11, which can exert a force onto a disc 12 between which the metal fibers 2 are placed. In the hot press, the temperature of the location at which the metal fibers 2 are located can be controlled. It is also possible to omit the disc 12 and place the metal fibers 2 directly between the upper part 11 and the lower part 11. To generate a network 6 of metal fibers 2 (scanning electron micrograph as shown in Figure 16a and 13 The disc 12 is made of a hot-fusible alloy having fine grooves (not shown) on its surface. These fine grooves have a width in the range of 30 to 60 pm.

[0153] Schematic views of a half-cell 13a according to the present application and a battery 13b according to the prior art are shown in Figure 16b and 16b) In both half-cells 13a, 13b, a current collector 14 is provided as a first electrode. The current collector 14 is coated with an active electrode material 15. Lithium 16 is provided as an electrolyte. In the half-cell 13a and 13b, an electrolyte is provided, which wets all components of the battery 13a and 13b and transports lithium ions. In Figure 17 The half-cell 13a schematically shown in Fig. 7, the current collector 14 is a network 6 of metal fibers 2 according to the present application, while in Figure 18 The battery 13b schematically shown in Fig. 8, the current collector 14 is a copper foil. In the context of describing examples, the structure and composition of the batteries 13a and 13b are described in more detail below.

[0154] Figure 20a Results of capacity measurements of the half-cells 13a and 13b are shown. The battery according to the present application comprising a network of metal fibers has an increased capacity of about 50% compared to a reference battery comprising a copper foil instead of a network of metal fibers, while keeping the composition and amount of active material constant for both half-cells 13a and 13b.

[0155] A further electrode was prepared using a network of metal fibers consisting of a copper alloy Cu 96 Si4. The network was infiltrated with a dispersion of 90% graphite and 10% binder, as further described below. As a reference electrode, a copper foil was coated with a 50 pm layer of the same dispersion using a doctor blade.Figure 18 and 19 The graphs show the discharge distribution of the electrode of the present invention with a metal fiber network and a reference cell obtained by chronopotential method.

[0156] exist Figure 20b The figure shows a reference cell obtained by the chronopotential method. Figure 21a The second and final charge / discharge distributions of the curves, and in Figure 21b) The diagram shows the second and final charge / discharge distributions of the network battery of the present invention obtained by the chronopotential method. To better demonstrate the changes in charge / discharge distribution during ringing, Figure 22 The graphs showing the charge / discharge distribution versus current-normalized time for the network battery and reference battery of the present invention, obtained by the chronopotential method, are illustrated. Figure 23 and 21c) A magnified view is provided. Figure 23 The capacity of the electrode and reference electrode of the present invention is shown to develop with the number of cycles.

[0157] exist Figure 23 In section a, a method using copper alloy Cu is provided. 96 SEM image of the electrode of the present invention, which is a metal fiber network composed of Si4. The SEM image shows that the graphite sheets are located within the metal fiber network, i.e., between the metal fibers. Figure 23 b) shows Figure 23 a) EDX mapping of copper in the electrode of the present invention shown in the figure. Figure 1a c shows Figure 2a Figure a shows the EDX mapping of carbon in the electrode of the present invention. The EDX mapping demonstrates the graphite between the metal fibers.

[0158] The following experiments were conducted:

[0159] The generation of metal fibers:

[0160] A melt spinning apparatus using a series of experimental parameters was used to form metal fibers. On one hand, the apparatus consisted of a large wheel 3 (copper alloy) with a diameter of 200 mm, placed in a chamber filled with atmospheric argon gas at 300 mbar (all typical experimental settings). On the other hand, the wheel rotation speed was increased to 60 m / s. A pressure difference of up to 2000 mbar (or less) between the crucible with nozzles and the surrounding chamber atmosphere triggered the ejection of molten metal or metal alloy onto the rotating wheel surface. As a result, for droplets of different metals deposited on the spinning wheel, the molten droplets were rapidly quenched (see...). Figure 1b (a) and (b) are formed and shaped into microribbon-like metal fibers. Details of the melt spinning apparatus used are disclosed in EP 19175749.1, WO 2016 / 020493A1 and WO 2017 / 042155A1.

[0161] Each single droplet 5 is transformed into a single metal fiber 2 or a plurality of metal fibers 2. The deposition rate of the molten alloy on the rotating wheel 3 is reduced to the range of 1.0 to 10.0 mg-s -1 or even lower. With this deposition rate, a large amount of metal fibers 2 in the form of micro ribbons is formed in the crucible up to 90-95% of the initial mass of the molten alloy. The optical images of the produced metal fibers 2 are shown in Figure 2a After the fast quenching and collection, the metal fibers 2 form a tangled network, in which the metal fibers easily slide against each other, so that it is easy to isolate one single metal fiber from the network.

[0162] The typical initial mass of the melt is in the range of 5 to 12 g (but can be increased up to 100 g). The distance between the nozzle 5 and the wheel surface is set in the range of 50 to 3000 μm, see Figure 4a ), which shows the photographic images taken separately from the images of the Al 99 Si1alloy melt deposited on the rotating wheel at 40000 fps. The temperature of the melt is set in the range of 50 to 300 °C above the melting temperature (higher processing temperatures are possible). Figure 4b ) to d) and the photographic images shown in Fig. 3 a) and b) are taken from the metal fibers produced accordingly.

[0163] Structure of the metal fibers:

[0164] The metal fibers 2 in the form of micro ribbons are produced from Co, Cu, Al and alloys of these elements with other elements such as Co 66 Fe4Mo2B 12 Si 16 , Al 99 Si1(no comprehensive list). The metal fibers 2 made of pure Cu or the alloy Al 99 Si1have a polycrystalline structure of crystals with a maximum size of up to 8 μm, as the copper metal fibers 2 Figure 4c ) and the Al 99 Si1alloy metal fibers 2 Figure 6a ) as shown by the X-ray diffraction spectra. The metal fibers 2 made of Co 66 Fe4Mo2B 12 Si 16 alloy have the typical structure of glassy metals, i.e. these metal fibers 2 are amorphous metal fibers 2, as depicted from Figure 5c) ) and the Al 66 Fe4Mo2B 12 Si 16 alloy metal fibers 2 can be seen.

[0165] When using more complex Cu and Al alloys and adjusting experimental parameters like wheel speed and melting temperature, metal fibers 2 that can be predominantly composed of Al or Cu can be fabricated to have a nanocrystalline or glassy metal structure (as for Co alloy Co 66 Fe4Mo2B 12 Si 16 as observed).

[0166] Dimensions of metal fibers:

[0167] For Co alloy Co 66 Fe4Mo2B 12 Si 16 , the metal fibers 2 have the following typical dimensions: a width of 2.0 to 25.0 pm, a thickness of 1.0 to 7.0 pm, and a length of 2.0 to 100.0 mm (see Figures 3a) and 3b)). The ribbon thickness is distributed as a narrow Gaussian distribution with a standard deviation as small as 0.4 pm, i.e. 68% (respectively 95%) of the metal fibers 2 have a thickness within an interval of as narrow as 0.8 pm (respectively 1.6 pm) centered around the average thickness. At a wheel speed of 25 m / s, the average thickness of the ribbon is 5.80 pm (see Figure 3b)). When the wheel speed is doubled, it decreases to 3.22 pm (see Figure 3a)). The fiber width is distributed as a Gaussian or lognormal distribution. At a wheel speed of 25 m / s, the average width of the fibers is 14.2 pm and the median width is 13.2 pm, i.e. 50% of the fibers have a width below 13.2 pm. When the wheel speed is doubled, the average width and the median width decrease to 9.4 pm, i.e. 50% of the fibers have a width below 9.4 pm.

[0168] For Al alloy Al 99 Si1, the average thickness and the median thickness are 8.5 ± 0.1 pm, i.e. for 68% (respectively 95%) of the fibers, and the metal fibers 2 have a thickness between 6.6 and 10.4 (respectively 4.8 and 12.2) pm. The average width is 39.5 ± 1.0 pm and the median width is 35.0 ± 1.0 pm, i.e. 50% of the fibers have a width below 35.0 pm Figure 5a) to c)). The Al 99 Si1 alloy metal fibers 2 are shown in Figure 7 and 5d) respectively.

[0169] The dimensions of the metal copper fibers 2 are similar to (or smaller than) the dimensions of the Al alloy metal fibers. SEM images of the metal copper fibers 2 are shown in Figure 8 and 5b)The SEM images are shown in FIG. 6. These SEM images prove that the width of the metal fibers 2 remains constant over a length of at least 1 mm (and even over a length of 1 cm). These ribbons have a crystalline structure: observing the top side (which is the liquid-gas interface) before the fast quenching solidification allows direct observation of the grains. The largest dimension of these crystals is estimated to be in the range of 5-8 μιη.

[0170] The metal fibers 2 are used to create a network 6 of metal fibers 2.

[0171] Generation of the metal fiber network:

[0172] Prior to creating the network 6 of metal fibers 2, the Co alloy Co 66 Fe4Mo2B 12 Si 16 has a crystallization temperature of 560 °C and a melting temperature of 1021 °C.

[0173] Example 1 :

[0174] The amorphous metal fibers 2 of Co 66 Fe4Mo2B 12 Si 16 produced by the melt spinning method described above are placed between two discs 12 of alumina having a diameter of 45 mm. The discs 12 of alumina having a diameter of 45 mm and the main components of the metal fibers 2 are then placed in a preheated hot press 10 at 400 °C and the fibers 2 are pressed at a predetermined pressure of 377 MPa for a predetermined time of 30 minutes to avoid thermal expansion effects due to heating.

[0175] Example 2:

[0176] The network 6 of Example 2 is prepared identically to the network 6 of Example 1, except that the pressure is reduced to 277 MPa. In Figure 9 SEM images of the network 6 of Example 2 are provided in FIG. 7, as can be seen, the metal fibers 2 are sintered together and form a stable network 6. The SEM images show that the texture and appearance of the metal fibers 2 are preserved except for the contact surface with the alumina discs 12.

[0177] Example 3:

[0178] The network 6 of Example 3 is prepared identically to the network 6 of Example 1, except that the alumina discs 12 of Thermax high temperature alloy having a diameter of 60 mm are used instead of the discs 12. The applied pressure is 283 MPa.

[0179] Example 4:

[0180] The network 6 of Example 4 is prepared identically to the network 6 of Example 3, except that the time is reduced to 20 minutes.

[0181] Example 5:

[0182] The network 6 of Example 5 was prepared identically to the network 6 of Example 3, except that the time was reduced to 10 minutes.

[0183] Example 6:

[0184] The network 6 of Example 6 was prepared identically to the network 6 of Example 3, except that the time was reduced to 5 minutes.

[0185] Example 7:

[0186] The network 6 of Example 7 was prepared identically to the network 6 of Example 3, except that the temperature was reduced by 300 °C.

[0187] Comparative Example 1:

[0188] For Comparative Example 1, the Co 66 Fe4Mo2B 12 Si 16 The amorphous metal fibers 2 were placed in an oven and heated to 600 °C for 30 minutes without applying external pressure. The fibers crystallized but did not sinter together.

[0189] Comparative Example 2:

[0190] The network of Comparative Example 2 was prepared identically to the network 6 of Example 1, except that the pressure was reduced to 157 MPa.

[0191] The network disintegrated when removed from the hot press 10, indicating that the metal fibers 2 did not sinter together sufficiently.

[0192] Comparative Example 3:

[0193] The network of Comparative Example 3 was prepared identically to the network 6 of Example 3, except that the pressure was reduced to 177 MPa.

[0194] Comparative Example 4:

[0195] The network of Comparative Example 4 was prepared identically to the network 6 of Example 4, except that the temperature was reduced to 100 °C.

[0196] Comparative Example 5:

[0197] The network of Comparative Example 5 was prepared identically to the network 6 of Example 4, except that the temperature was reduced to 200 °C.

[0198] Table 1 summarizes the time, pressure, and temperature used to prepare the networks of Examples 1-7 and Comparative Examples 1-5.

[0199]

[0200] In Comparative Example 2, the time and temperature were the same as in Examples 1 and 2. However, the network in Comparative Example 2 decomposed upon re-movement from press 10. This indicates that the pressure was insufficient for sintering amorphous Co. 66 Fe4Mo2B 12 Si 16 Alloy metal fibers 2 are used to provide fixation between the metal fibers 2. It can be concluded that pressure is the driving force for the sintering of the metal fibers 2. Since amorphous materials have a lower density than crystalline materials, atoms at the phase interface begin to move when pressure is applied. Given the applied pressure, this causes these atoms to transform into an energy-preferred state. As a result of the movement of atoms, the metal fibers 2 are permanently sintered together.

[0201] The metal fiber network 6 in Examples 3 to 5 did not show significant differences. When the time was shortened to only 5 minutes in Example 6, the fibers 2 were not as firmly bonded to each other as in Examples 3 to 5. This demonstrates that Co 66 Fe4Mo2B 12 Si 16 The process of fixing the alloy metal fibers 2 to each other is time-dependent, but can be completed within a few minutes.

[0202] It can be seen that although the metal fiber 2 was subjected to temperatures of only about Co, 66 Fe4Mo2B 12 Si 16 The melting temperature of the alloy is 40% or 30%, but a process occurs to sinter the metal fibers 2 together, as demonstrated by Examples 4 and 7, where the temperatures are 400°C and 300°C, respectively. Comparative Examples 4 and 5 show that if the temperature is reduced to 100°C or 200°C, respectively, the movement of atoms is too low to provide the fixation of the metal fibers 2 to each other by sintering.

[0203] Example 8:

[0204] Network 6 in Example 8 was prepared in the same manner as network 6 in Example 3; however, the temperature was set to 500°C and the time to 20 minutes. Furthermore, in network 6 of Example 8, more fibers 2 were used to obtain a network 6 with a thickness of 0.7 mm. After 20 minutes at a temperature of 500°C and a pressure of 283 MPa, network 6 of Example 8 was completely sintered, meaning the stability of network 6 was comparable to that of Example 3.

[0205] exist Figure 9 The image shown is of network 6 in example 8 before deformation, and... Figure 10 The image shown is of network 6 in the deformed state of example 8. Therefore, from... Figure 10It can be seen that even when the network 6 is highly deformed, no metal fibers 2 are detached from the network 6. This indicates that a highly stable network 6 is formed which is not easily damaged by deformation.

[0206] Example 9:

[0207] The network 6 of Example 9 was prepared identically to the network 6 of Example 3, however, instead of Co 66 Fe4Mo2B 12 Si 16 The amorphous metal fibers 2 were replaced by polycrystalline wire fibers 2 of copper (Cu) as described above, the time was set to 5 minutes, the pressure was set to 177 MPa and the temperature was set to 300°C.

[0208] Example 10:

[0209] The network 6 of Example 10 was prepared identically to the network 6 of Example 9, however, the time was set to 5 minutes.

[0210] Comparative Example 6:

[0211] The network 6 of Comparative Example 6 was prepared identically to the network of Example 9, however, the time was set to 30 minutes and the temperature was set to 500°C.

[0212] Table 2 summarizes the time, pressure and temperature used for the preparation of the networks of Examples 9 and 10 and Comparative Example 6.

[0213] Table 2

[0214]

[0215] In Comparative Example 6, the metal fibers could not be identified in the sintered product and the product obtained was a copper foil. If a light source is placed behind the copper foil, a certain inhomogeneity can be identified. The networks 6 of Examples 9 and 10 had a thickness of from 0.15 mm up to 0.25 mm.

[0216] To produce the network 6 of Example 9, the time and temperature were reduced to 5 minutes and 300°C, while the pressure was the same as applied in Comparative Example 6. The metal fibers 2 and the porous structure, i.e. the voids 9, could be identified in the resulting product, at least in some areas. Thus, to produce the network 6 of Example 10, the time was further reduced to 3 minutes, while the time and pressure were kept at the same values as in Example 9. The porous structure, i.e. the voids 9, was found to be present substantially uniformly throughout the sample.

[0217] Images of the networks 6 of Examples 9 and 10 are shown in Figures Figure 11 and 11 respectively. From Figure 12It can be seen that the network 6 of Example 9 has some areas of reduced porosity. Particularly close to the edges of the network 6 of Example 9, a number of holes can be observed. By reducing the time from 5 minutes to 3 minutes, the porosity increases, as can be seen from the images of the network 6 of Example 10 provided in Figure 12

[0218] SEM images of the network 6 of Example 10 are shown in Figure 14a and 13 The striations visible in Figure 14b and 13 are caused by the surface of the Thermax high-temperature alloy disc 12 used to press the metal fibers 2. The striations in the Thermax high-temperature alloy disc are a result of cutting the Thermax high-temperature alloy.

[0219] Without being bound by theory, it is assumed that the metal copper fibers 2 exhibit an improved sintering ability due to the high energy stored as a result of the rapid cooling rate due to the melt-spinning process used to make the fibers. The melt-spinning process provides cooling rates of up to 106K min -1 , which freezes the movement of the atoms of the system before they can arrange themselves into energetically favorable states. Of course, copper-specific effects related to atomic diffusion can also play a role.

[0220] The networks 6 of the above examples can be bent without permanently deforming them. If these networks 6 are folded, they can be provided with a stable new shape.

[0221] Further experiments were performed using metal fibers of the Cu alloy Cu 92 Sn8. The metal fibers of the Cu alloy Cu 92 Sn8 were prepared similarly to the other metal fibers described above. The metal fibers of the Cu alloy Cu 92 Sn8 were dispersed in 200 mL of demineralized water containing 50 mg of SDS (sodium dodecyl sulfate), dried after vacuum filtration. In the entangled network of metal fibers obtained in this way, the metal fibers were distributed uniformly but without orientation.

[0222] Example 11:

[0223] Cu 92 ​The polycrystalline metal fibers 2 of Sn8 (as described above) are placed between two plates 12 of a hot-melt alloy with a diameter of 60 mm. The plates 12 and the main components of the metal fibers 2 are then placed in a hot press 10 preheated to 300°C and pressed at a predetermined pressure of 78 MPa for a predetermined time of 3 minutes to avoid thermal expansion due to heating. This yields Cu. 92 The stable network 6 of Sn8 metal fibers has similar deformation stability to the network 6 in Examples 1 to 10 described above. The network 6 in Example 11 has a thickness ranging from 0.15 mm to 0.25 mm. 92 Photograph of Sn8 metal fiber network 6 Figure 14c As shown in ), Cu 92 SEM images of the Sn8 metal fiber network in Figure 24 )and Figure 25 As shown in the figure.

[0224] Compare with Example 7:

[0225] Network 6 in Comparative Example 7 was prepared in the same manner as Network 6 in Example 11; however, the temperature was maintained at room temperature, approximately 20°C. The metal fibers did not sinter together and only weak mechanical stability was observed. This mechanical stability is a result of the deformation of the metal fibers due to the applied pressure, rather than a result of the sintering of the metal fibers.

[0226] Compare with Example 8:

[0227] Network 6 in Comparative Example 8 was prepared in the same manner as network 6 in Example 11; however, only a weak pressure of approximately 2 kPa was applied. The resulting metal fibers were not fixed to each other.

[0228] Example 11 and comparative examples 7 and 8 demonstrate that a combination of pressure and temperature is required to sinter the metal fibers together, thus fixing the metal fibers 2 to each other. Unbound by theory, it is likely that pressure causes the metal fibers 2 to come into close contact with each other, and mechanical deformation forms matching contact surfaces between the metal fibers 2. Increased temperature promotes atomic movement in the pressure direction, and thus leads to the sintering of the metal fibers 2, fixing them to each other.

[0229] Example 12

[0230] Preparation of down through combing

[0231] Carding is a mechanical method for untangling, cleaning, and mixing fibers 2 to prepare continuous fibers 26. The design of the carding machine 24 is as follows: Figure 25A continuous pile 26 is obtained by passing the fibers 3 between different moving surfaces (e.g. a drum 28) covered with a card cloth 30. The card cloth 30 breaks the clumps and unorganized masses of fibers 2 and then aligns the individual fibers 2 parallel to each other. Although carding is well known for piles, it has not yet been used to organize metal fibers 2 to form a pile 26.

[0232] Figure 25 An example of a carded pile is shown. Here, fibers of brass of about 10 cm length, 30 pm width and 2 pm thickness, as prepared by melt spinning, are disentangled by a carding device. Two layers are formed stacked on top of each other. It can also be stacked between layers of cotton in order to form a cotton / metal hybrid pile or organization. A combination of cotton and metal fiber webs can also be disentangled by one carding step and form a cotton / metal fiber hybrid pile.

[0233] Figure 25 A photo image of the manufacturing method according to the present application is shown. First, metal fibers are disentangled by a carding device, as Figure 25 is shown in the upper left image. For a better overview, Figure 25 the reference signs are not shown. Fibers of different orientation as shown in the two middle photos in the upper line are stacked on top of each other to provide a two-layer pile, as Figure 25 is shown in the upper right image of Figure 25 . As intermediate material, cotton pile (such as cotton pile shown in the lower right image of Figure 26 ) can be integrated in the metal fibers to provide a layered pile, the upper and lower side of which are shown in the lower left and middle images of Figure 26 .

[0234] Example 13:

[0235] Ultrasonic welding is applied to mechanically fix all fibers 2 in the metal network 6 or only fibers 2 at different locations. In principle, longitudinal and vertical ultrasonic welding is possible. Corresponding machines are commercially available. Vertical ultrasonic is the preferred technique. Here, a hammer moves up and down at high frequency. In principle, this is also possible by hammering a suitable object on a pile made of metal fibers 2. An example of a copper-based pile is shown in Figure 26 . In Figure 26 , for a better overview, the reference signs are not shown. Figure 26 The left part of the photo image of a network 6 of metal fibers 2 according to the present application is shown. The square section clearly visible in the middle of the photo image on the left side is the area where the metal fibers 2 are fixed to each other via ultrasonic welding as described above. Figure 16a The images numbered 1 to 3 in Figure 16bMagnified view of the portion indicated by the corresponding frame and number in the photograph image on the left. The image below Magnified view 1 is another magnified view corresponding to the frame indicated in Magnified view 1 and shows the metal fibers 2 fixed to each other as a result of the applied ultrasonic welding.

[0236] Preparation of the electrodes and lithium ion batteries:

[0237] The electrode of the invention:

[0238] A disc with a diameter of 6 mm was cut out of the network 6 of example 10 and infiltrated with a dispersion of 80% SnO, 10% carbon black and 10% binder. In this electrode of the invention, the network 6 of sintered metal fibers 2 of copper serves as current collector 14.

[0239] The electrode of the invention:

[0240] A copper foil was coated with a dispersion of 80% SnO, 10% carbon black and 10% binder to obtain a copper foil with a coating layer of active material on its surface. The thickness of this coating was adjusted to 50 μιη by using belt casting. The copper foil serves as current collector 14.

[0241] The dispersion was prepared using the following materials:

[0242] SnO: Tin (II) oxide, 99.9 wt%, trace metal based (Alfa Aesar (Art. Nr. 11569))

[0243] Carbon black: (Carbon nano powder < 100 nm, Sigma Aldrich, P-code: 633100-25)

[0244] Binder: Polyvinylidene fluoride (PVDF) (Alfa Aesar (Art. Nr. 44080))

[0245] The battery:

[0246] As Figure 17 schematically shown, a half battery 13a comprising electrodes 14 and 15, separator 17 and Li foil 16 was assembled. In this half battery 13a, the electrode described above as electrode of the invention was used, i.e. the network 6 of example 10, which was coated with active electrode material 15.

[0247] For reference, another half battery 13b was assembled as Figure 18 schematically shown. In this half battery 13b, the electrode described above as electrode not of the invention was used, i.e. a copper foil coated with 50 μιη of active electrode material as described above.

[0248] If the amount of active electrode material 15 in the reference half-cell 13b is increased, i.e. the layer is tape cast thicker than 50 pm, the capacitance decreases because the electrons have to pass through a thicker layer of active electrode material. It was found that by using the assembly shown in 13a, the amount of active electrode material can be increased by a factor of 60 compared to the standard assembly shown in 13b by incorporating it into the conductive network. Furthermore, a uniform charge distribution throughout the electrode can be obtained by using a network of metal fibers and the capacity per mass unit can be further significantly increased.

[0249] In Figure 20a a comparison of the capacities of the two half-cells 13a, 13b is provided. As can be seen, the capacity of the half-cell 13a (according to the present application) is increased by almost 50% compared to the reference half-cell 13b.

[0250] The capacity measurements were performed using a Metrohm M204 electrochemical measurement system, running with software NOVA Cell 1.0. The cells were assembled in Swagelok TM type cells, using lithium foil (Sigma Aldrich (99.8 wt%) as counter electrode, Celgard® (Sigma Aldrich, 2400, 25 pm) as separator, and 1 M LiClO4 (Sigma Aldrich) dissolved in 1 : 1 EC / DMC (Ethyl Carbonate / Dimethyl Carbonate (ALFA AESAR)) as electrolyte. glass microfiber filter, grade) as separator, and 1 M LiClO4 (Sigma Aldrich) dissolved in 1 : 1 EC / DMC (Ethyl Carbonate / Dimethyl Carbonate (ALFA AESAR)) as electrolyte.

[0251] To measure the capacity of the half-cells, a constant current of 100 mAh / g was applied, normalized to the amount of active material for the respective electrode. The potential was measured simultaneously and the eddy current points of the potential 0.0125 V (lower eddy current point) and 2.2 V (higher eddy current point) were measured. The resulting set of data points comprises the value of the potential at any given point in time. Since a constant current was supplied, the capacity can be calculated by multiplying the time between the lower (fully discharged) and higher eddy current point (fully charged) by the applied current.

[0252] In addition to the above half-cell 13a, other electrodes were prepared and assembled with a counter electrode, a separator and an electrolyte and analyzed. The specifics are as follows:

[0253] Cu 96The Si4 fibers were dispersed, vacuum filtered and then pressed between two 60 mm diameter Thermax alloys at 300 °C for 3 min at a pressure of 300 kN. From the resulting sintered network (mechanically stable) 10 mm diameter discs were punched and infiltrated with a dispersion of 90% graphite and 10% binder. Here, the copper alloy network acts as the current collector. As a reference, the same dispersion was coated using a doctor blade with 50 pm layers on a copper foil.

[0254] The graphite and binder used were as follows:

[0255] Graphite: powder, <20 pm, synthetic (Sigma Aldrich (Art. Nr. 282863)

[0256] Binder: polyvinylidene fluoride (PVDF) (Alfa Aesar Art. Nr. 44080)

[0257] Capacity measurements were performed using a Metrohm M204 electrochemical measurement system running with software NOVA battery 1.0. The cell was assembled in a Swagelok TM type cell, using lithium foil (Sigma Aldrich (99.8 wt%) as counter electrode, glass fiber (Sigma Aldrich, glass microfiber filter, grade) as separator, EC: DMC (1 M LiPF6) as electrolyte (EC: ethylene carbonate; DMC: dimethyl carbonate).

[0258] To measure the capacity of the half-cell, a constant current of 382 mA / g was applied, normalized to the amount of active material for the respective electrode. The potential was measured simultaneously and the vortex points of the potential 0.0125 V (lower vortex point) and 2.2 V (higher vortex point) were measured. The resulting set of data points comprises the value of the potential at any given point in time. Since a constant current was supplied, the capacity can be calculated by multiplying the time between the lower (fully discharged) and higher vortex point (fully charged) by the applied current.

[0259] For the reference cell with a reference electrode, a decrease of 76% of the capacity (from 1183 mAh / m2to 289 mAh / m2) was noted after 50 cycles. For the cell with the network electrode of the application, a decrease of only 9% of the capacity (from 1492 mAh / m2to 1381 mAh / m2) was noted. This demonstrates that the network electrode of the application is more electrochemically stable than the common reference electrode with almost constant capacity over 50 cycles when using the same active material. This involves the 3D network of the electrode of the application which supports an efficient distribution of the stresses formed within the active material due to the swelling during the insertion of ions. Upon insertion of lithium ions, the active material undergoes a swelling (up to 8 vol% for graphite) which leads to a decrease of the capacity with cycling in the reference cell.

[0260] Moreover, these results indicate that the electronic conductivity is improved by the metal fiber network of the application used as current collector. This network improves the electrode conductivity by shortening the electronic conduction path compared to the reference electrode where there is a gradient of conductivity through the electrode. Thus, for the case of the electrode of the application, it was possible to charge and discharge the half-cell 50 times in 6 hours compared to the reference electrode which was charged 50 times in 16 hours. Moreover, as mentioned above, it is possible to preserve the capacity of the network electrode of the application (1492 mAh / m 2 → 1381 mAh / m 2 ) which is not the case for the reference electrode (1183 mAh / m 2 → 289 mAh / m 2 ).

[0261] Figure 20b and 19 present the charge discharge profiles of the reference cell and the network cell of the application respectively. Figure 21a) to 21c) ) and Figure 22 ) present the first and last cycles of the same measurement. Figure 23 present the charge discharge profiles with current normalized time in order to better observe the changes upon cyclization. Figure 23 present the capacity over cycles.

[0262] For all calculations, the first cycle of each measurement was excluded.

[0263] Material a) presents a cross-section SEM image of the network electrode of the application which visualizes the graphite sheets between the copper fibers. The same points of the study are mapped by EDX (EDAX model ZEISS Ultra 55, 132-10) in Defect energy [kJ / g] b) and 23 c) shown in).

[0264] Microstructure of the metal fibers:

[0265] To investigate the influence of the microstructure of the metal fibers in the network of metal fibers, CuSi4, Al 99 Si1, Cu 92 Sn8, Co 66 Fe4Mo2B 12 Si 16 and FeNiB fibers. The alloys listed in Table 3 were heat pretreated with the parameters listed in Table 3 to reduce the stored defect energy, but not to cause a change in the grain structure by recrystallization. The amorphous / nanocrystalline fibers were additionally heat treated above the crystallization temperature to investigate the differences in the microstructure state.

[0266] Table 3

[0267]

[0268] A part of the fibers in each state (before heat pretreatment, after heat pretreatment and after crystallization) was melted twice using a Netzsch STA 449 F3 under an argon atmosphere. The heat pretreatment was also performed using a Netzsch STA 449 F3 using the parameters described in Table 3. In the case of Al 99 In the case of Si1, all samples were heated from 30°C to 1200°C or 900°C, respectively, with a constant heating and cooling rate of 10 K / min and then cooled again to 30°C. The samples were then heated to 1200°C or 900°C, respectively. Between the individual melting steps or, if applicable, between the heat treatment and the melting, the temperature was held at 30°C for 1 hour. By subtracting the second heat cycle from the first heat cycle, the measurement can be adjusted so that only the amount of pure energy of the fibers is measured. The difference in the area integration between the measurements with and without heat pretreatment corresponds to the stored defect energy or the crystallization energy. The amount of stored energy is shown in Table 4 as defect energy and crystallization energy. The energy of CuSi4 could not be determined, because during the heat pretreatment the fibers were transferred into a thermodynamically stable phase with a two-phase structure. Due to the resulting two-phase structure, a correct measurement of the stored defect energy is not possible.

[0269] Table 4

[0270] Crystallization energy [kJ / g] Material Weight [g] Cu 96 Si4]] - - Al 99 Si1]] 1.7 - Cu 92 Sn8]] 1.8 - Co 66 Fe4Mo2B 12 Si 16 ]]> 0.1 2.6 Fe 40 Ni 40 B 20 ]]> 2.8 3.8

[0271] As can be seen from the results of Table 4, the metal fibers obtained by melting spinning as described above have a significant amount of stored energy in the form of defect energy and / or crystallization energy, i.e. these fibers are not in their thermodynamic equilibrium. Even for the alloy Cu 96Si4 does not indicate any value, note that the metal fibers of this alloy also have a significant amount of defect energy; however, it is not possible to make a meaningful quantification of it because the material is shifted to a thermodynamic equilibrium state when subjected to the thermal pretreatment conditions specified in Table 3. Cu 96 The combined amount of defect energy and crystallization energy of Si4 is estimated to be about 2.3 kJ / g.

[0272] The fibers are then weighed against the values given in Table 5 and wet laid to form a uniform nonwoven structure thereof. These are then sintered using pressure-induced low temperature sintering as described above for Example 1, with the parameters also listed in Table 5. Prior to sintering, the electrical conductivity of the nonwoven structure of copper and aluminum alloy fibers is determined by 4-point measurement and impedance measurement. These measurements are repeated after sintering. The values before and after sintering are listed in Table 6.

[0273] Table 5: Initial weight and pressure sintering parameters.

[0274] Temperature [°C] Pressure [MPa] Duration [min] Figure 27 Figure 27 Cu 96 Si4]] 1 300 35 5 Al 99 Si1]] 0.7 200 35 5 Cu 92 Sn8]]> 1 300 35 5 Co 66 Fe4Mo2B 12 Si 16 ]]> 1 400 140 5 Fe 40 Ni 40 B 20 ]]> 0.7 400 140 5

[0275] Table 6: Electrical conductivity.

[0276]

[0277] It can be clearly seen that the electrical conductivity of the sintered samples is many times higher than that of the unsintered samples. It is worth mentioning that in the case of loose fibers (before sintering), the distance between the contacts used to measure the electrical conductivity of the material is only 5 mm. Increasing the distance between these contacts increases the resistance by more than 100 times. This is due to the fact that the unsintered fibers do not form a stable conductivity between the fibers. In contrast, in the case of sintered networks, the conductivity is almost independent of the distance between the contacts when this distance is increased. This is because of the high conductivity between the fibers due to sintering.

[0278] To investigate the mechanical stability of the samples, 10 mm wide strips are cut from each sample and examined with the aid of a tensile test at a tensile rate of 0.01 mm / s. The results of the tensile measurements are presented in Table 7. The same number of fibers per cross section is chosen for the standardization of the samples, since all samples are made from the same generated uniform fibers with the same base weight. Therefore, the samples from the network of metal fibers in which the fibers are subjected to a thermal pretreatment as described in Table 3 have the same density of fibers compared to the samples from the network of metal fibers in which the fibers are not subjected to such a thermal pretreatment.

[0279] Table 7: Mechanical stability of sintered fiber networks

[0280]

[0281] It is clear that the mechanical properties of the sintered network are negatively affected by the heat treatment of the sample and the associated degradation due to storage defects. In other words, the strength of the resulting sintered network is improved by using metal fibers with a structure that is not in thermodynamic equilibrium. This is particularly relevant for Co samples that have undergone heat pretreatment. 66 Fe4Mo2B 12 Si 16 The sample became exceptionally clear. Compared to the untreated sample, the thermally pretreated Co... 66 Fe4Mo2B 12 Si 16 The sample could not be sintered at all. Amorphous / nanocrystalline alloy Co 66 Fe4Mo2B 12 Si 16 and Fe 40 Ni 40 B 20 The crystalline samples could not be sintered at all; the samples were annealed before sintering. They decomposed into fine fibrous particles during pressing without any mechanical cohesion.

[0282] In conclusion, if the sample is not annealed prior to sintering, only fibers produced by melt spinning can be mechanically and firmly bonded together through pressure-induced low-temperature sintering. The results presented here demonstrate the extent to which the defect energy introduced by the manufacturing process affects the degree of sintering and, therefore, the mechanical and electrical properties of the 3D mesh. For the 3D mesh to be used as a current collector, it is essential that these fibers are firmly connected to each other to ensure constant electrical conductivity across the entire battery electrode. However, it is required to maintain the fiber structure during sintering, i.e., to prevent the fibers from being pressed onto the non-porous metal foil.

[0283] The present invention is further described below with respect to the battery manufacturing method. Battery production consists of seven processing steps:

[0284] 1. The generation of metal fibers ( Figure 27 Step 1)

[0285] 2. Combing the fiber web to lay out the fiber pile ( Figure 27 Step 2, b1); alternatively, fibers are deposited by liquid dispersion or gas flow. Figure 27 Step 2, b2).

[0286] 3. Sintering of metal fibers for the formation of metal fiber mesh electrodes ( Figure 27 Step 3); in the hot press (c1, c2), by ultrasonic welding (c3) or hammering (c4).

[0287] 4. Anodes and cathodes are formed by loading metal fiber meshes with electrode active materials. Figure 27 Step 4)

[0288] 5. Calendering of the electrode (step 5) in Figure 27

[0289] 6. Ultrasonic welding of the conductive wire on the electrode as connector (step 6) in Figure 27

[0290] 7. Assembly of the battery (step 7) of Figure 27

[0291] Figure 24 A schematic overview of these process steps is provided in Figure 1, wherein step 1 shows the generation of metal fibers, step 2 shows the laying of the fiber web for the layer of fiber fleece, and step 3 shows different sintering methods of the metal fibers for forming a mechanically stable metal fiber web. Sintering can be performed by pressure-induced low-temperature sintering (part cl) or by thermal sintering (part c2), ultrasonic welding (part c3) or hammering (part c4). In part d, anodes and cathodes are formed by loading the metal fiber network with active material (step 4). The electrodes are densified in part e using calendering (step 5). As a next step, a conductive foil is attached to the network of metal fibers in step 6. In step 7 of Figure 27

[0292] Step 1. Generation of metal fibers

[0293] Metal fibers are produced by melt spinning. Two main different melt spinning technologies can be used to produce metal fibers: a) vertical melt spinning machines, b) horizontal melt spinning machines; vertical melt spinning machines have technical limitations which make the product more expensive and less efficient compared to the generation using horizontal melt spinning machines. Therefore, the use of horizontal melt spinning machines is preferred in the present invention.

[0294] Step 2. Laying of the fiber fleece

[0295] For textiles, metal fibers are treated very much like cotton is used for textiles, which is why the resulting web can be called a metal textile. First, the metal "wool" is disentangled and the fibers are aligned by carding, as Figure 27 ​​​​The diagram is schematically shown. This step requires microfibers of considerable length. By using melt spinning as described herein, fibers several centimeters in length can be generated; due to the significant fiber length, a liquid dispersion step is neither necessary nor possible. This treatment produces a three-dimensional fiber web for subsequent processing. In step 2, b1, the fibers are combed by a carding comb, as known in the field of cotton processing, to obtain a uniform fiber web structure, and such ordered layers are stacked on top of each layer. To do this, these fibers preferably have a length of 5-18 cm and are not connected to each other before carding. In this step, a liquid dispersion step is not required. Due to the elongation of the fibers, it is possible to avoid liquid dispersion.

[0296] Alternatively, disordered fiber webs are generated by deposition from a liquid dispersion or from an air stream (step 2, b2).

[0297] Step 3. Sintering of metal fibers used for the formation of 3D metal fiber mesh

[0298] The distance between the two heating plates is adjustable between 0.2-1mm, and in this case, it is 0.5mm; Al 99 Si1 was held at 650℃ for 1.5 h; Cu 96 A uniform fibrous network structure sintered from Si4 at 950°C for 2 hours, such as in Figure 27 Step 3, shown schematically in c2.

[0299] This results in a strong mechanical bond between the fibers at their intersections. Once the metal fibers are mechanically bonded and sintered, electrical conductivity increases significantly.

[0300] Alternatively, 3D metal fiber meshes are pressure sintered between two hot plates. For this purpose, the fibers are placed on two polished hot plates and sintered with Al at 150°C under a pressure of 10 GPa in a preheated uniaxial press. 99 Si1 is pressurized and Cu is subjected to 300°C. 96 Si4 is pressurized for 1 minute, for example Figure 27 Step 3, c1, is schematically shown. After this, the mechanically stabilized 3D fiber optic network can be easily pulled off the substrate.

[0301] Alternatively, metal fibers are welded using ultrasonic welding. Figure 27 Step 3, c3) or hammering ( Figure 27 Step 3, c4) Local fixation.

[0302] Step 4. Form the anode and cathode by loading a 3D metal fiber mesh with electrode active material.

[0303] The active material used in the examples was commercially available as a slurry from CustomCell. Graphite was used for the anode side and NMC_111 for the cathode side.

[0304] Next, the 3D metal fiber web was loaded with the active material slurry using a standard doctor blade process (from doctor blade; Rakel prozess) as shown in Figure 27 Step 4, d. The siliconized PMMA foil was placed on the plate and then wetted with ethanol / acetone. After the foil was flattened, the sintered fiber network was placed on the foil. Then, a rather liquid slurry of the active material was drop-casted onto the 3D metal fiber web. The 3D metal fiber web structure provides capillary forces that pull the slurry into the network and coat the slurry evenly. A more viscous slurry was poured onto the network and residual slurry was removed using a gap doctor blade (height 0.650 mm). Subsequently, the samples were dried (anode at room temperature (RT) and cathode at 30 °C).

[0305] The 3D metal fiber networks were formed without contact with the active material, i.e. after the sintering of these networks was completed, the active material was applied to the network of metal fibers.

[0306] Lamination / post-processing of the electrodes

[0307] Step 5. Calendering of the electrodes

[0308] After drying the electrodes, they were laminated using a calendering process with a gap of 0.2 mm and a weight limit of 40 kg per roll. Additional experiments with the following parameters were also conducted:

[0309] - 0.4 mm gap, 40 kg

[0310] - no gap, 40 kg

[0311] - no gap, 120 kg

[0312] - no gap, 112 kg, 160 °C

[0313] A schematic of this calendering process is shown in Battery of the invention Step 5, e.

[0314] Step 6. Ultrasonic welding of the conductive foil to the electrodes

[0315] Finally, the Ni foil was attached to the electrode side by ultrasonic welding. These Ni foils are the contact electrodes of the battery. The ultrasonic welding of the contact electrodes to the network 6 is shown schematically in Comparative battery Step 6, f.

[0316] Step 7. Assembly of the battery

[0317] The encapsulation of the 3D metal fiber network starts with the punching of the electrodes loaded with active material in the desired size / geometry. The samples are placed in a uniaxial press and punched in the required form. Subsequently, these samples are glued to the corresponding sides of the separator (PP / PE stretched) using PVDF adhesive in acetone, which is previously punched with an overlap of 1-2 mm in order to avoid internal short-circuiting of the electrodes. Then, they are placed in a lamination bag and dried in an oven at 110°C for 48 hours. After 48h, the samples are transferred to a glove box, filled with electrolyte (EC / DMC, 1M LIPF6) and sealed to ensure airtight packaging. After wetting the sample for 3h, the excess electrolyte is removed using a syringe and a vacuum pump with a liquid filter and sealed again tightly directly under the electrode.

[0318] Results:

[0319] The battery of the present application obtained by the above method was compared with a comparative battery which does not contain a metal fiber web as a current collector but contains a flat foil. The results are provided in Tables 8 and 9 below.

[0320] Table 8: Weight capacity and weight energy density

[0321] Weight capacity 140 Ah / kg (0.1 C) 63 Ah / kg (0.1 C) 135 Ah / kg (0.5 C) 52 Ah / kg (0.5 C) 67 Ah / kg (1 C) 29 Ah / kg (1 C) Weight energy density 519 Wh / kg (0.1 C) 233 Wh / kg (0.1 C) 499 Wh / kg (0.5 C) 196 Wh / kg (0.5 C) 249 Wh / kg (1 C) ​ ​ 107 Wh / kg (1 C)

[0322] Table 9: Volume capacity and volume energy density

[0323] Battery of the invention Comparative battery Volumetric capacity 87 Ah / l (0.1 C) 28 Ah / l (0.1 C) 81 Ah / l (0.5 C) 24 Ah / l (0.5 C) 41 Ah / l (1 C) 18 Ah / l (1 C) Volumetric energy density 320 Wh / l (0.1 C) 106 Wh / l (0.1 C) 301 Wh / l (0.5 C) 89 Wh / l (0.5 C) 150 Wh / l (1 C) 67 Wh / l (1 C)

[0324] In the above Tables 8 and 9, the c-rate for determining the values of weight and volume capacity and energy density is represented as 0.1C, 0.5C and 1C, respectively.

[0325] Reference signs

[0326] 1 Melt spinning device

[0327] 2 Metal fiber

[0328] 3 Spinning wheel

[0329] 4 Microstructured nozzle

[0330] 5 Droplet

[0331] 6 Network

[0332] 7 Contact point

[0333] 8 Tweezers

[0334] 9 Void

[0335] 10 Hot press

[0336] 11 Upper and lower

[0337] 12 disc

[0338] 13a battery

[0339] 13b prior art battery

[0340] 14 collector

[0341] 15 active electrode material

[0342] 16 lithium

[0343] 17 separator

[0344] 20 spike

[0345] 22 peak

[0346] 24 carding machine

[0347] 26 nap

[0348] 28 drum

[0349] 30 card clothing

Claims

1. A network (6) of metal fibers (2) comprising: a plurality of metal fibers (2) fixed to each other; wherein the plurality of metal fibers (2) have a length of 1.0 mm or more, a width of 100 pm or less and a thickness of 50 pm or less, wherein the metal fibers (2), before and / or after being fixed to each other, show an exothermic event when heated in a DSC measurement, wherein the exothermic event releases an amount of energy of 0.1 kJ / g or more, wherein the energy comprises defect energy; wherein the metal fibers comprise one of the elements selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, cobalt, iron, chromium, vanadium, titanium, aluminum, silicon, lithium, combinations of the aforementioned and alloys comprising one or more of the aforementioned; wherein the metal fibers (2) are in an amorphous and / or nanocrystalline state before and / or after being fixed to each other.

2. The network (6) according to claim 1, wherein the exothermic event releases an amount of energy of 0.5 kJ / g or more.

3. The network (6) according to claim 1 or 2, wherein the metal fibers (2) are in electrical contact with each other.

4. The network (6) according to claim 1 or 2, wherein at least some of the plurality of metal fibers (2) are sintered to each other.

5. The network (6) according to claim 1 or 2, wherein The metal fibers (2) can be obtained by melt spinning subjecting the molten material of the metal fibers (2) to a cooling rate of 10 2 K*min -1 or more.

6. The network (6) according to claim 1 or 2, wherein each metal fiber (2) is in contact with one or more other metal fibers (2).

7. The network (6) according to claim 1 or 2, wherein the network (6) is a disordered or ordered network (6).

8. The network (6) according to claim 1 or 2, wherein, the network (6) has open pores between the metal fibers (2) of the plurality of metal fibers (2).

9. The network (6) according to claim 1 or 2, wherein at least some of the plurality of metal fibers (2) are at least partially coated.

10. The network (6) according to claim 1 or 2, wherein, the contact points (7) between the metal fibers are distributed in a disordered or ordered manner throughout the three-dimensional structure of the network (6).

11. A method of generating a network (6) of metal fibers (2) according to any of the preceding claims, wherein the method comprising a step 1 of generating a plurality of metal fibers (2) having a length of 1.0 mm or more, a width of 100 pm or less and a thickness of 50 pm or less by melt spinning; a step 2 of providing a loose network of the metal fibers (2) generated in step 1 ; and a step 3 of fixing the plurality of metal fibers to each other by one of the following treatments cl to c4: cl : sintering the metal fibers to each other; c1 : placing the plurality of metal fibers in a hot press (10) and subjecting the plurality of metal fibers (2) present in the hot press (10) to a predetermined pressure and temperature for a predetermined period of time to generate the network (6) by sintering the plurality of metal fibers (2) to each other to form contact points (7) between the metal fibers (2), wherein in process c1 the pressure is between 0 GPa and 20 GPa and the temperature is between 10% and 80% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement; c2: placing a loose network of metal fibers (2) between two hot plates and adjusting the distance between the two hot plates to 0.1 mm to 1 mm and heating the hot plates to a temperature of 10% to 80% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement; c3: ultrasonic welding; c4: hammering.

12. The method according to claim 11, wherein, process c3 or c4 is used to fix the metal fibers (2) to each other over the entire surface area of the network (6) or at a plurality of separate areas distributed over the surface area of the network (6).

13. The method of claim 11 or 12, wherein, The metal fibers (2) have a length of 1 cm to 20 cm.

14. The method according to claim 11 or 12, wherein The method further comprises a step 4 of coating the metal fibers (2), wherein step 4 is carried out after step 3.

15. The network (6) of metal fibers (2) according to claim 1 or 2, wherein The network (6) of metal fibers (2) comprises a plurality of metal fibers (2) fixed to each other; and wherein the network (6) of metal fibers (2) is obtained by a method comprising: by subjecting a molten material from which a metal fiber will be produced to a cooling rate of 10 2 K*min -1 or more to produce a plurality of metal fibers (2) having a length of 1.0 mm or more, a width of 100 μm or less, and a thickness of 50 μm or less. a step 2 of arranging the metal fibers (2) obtained in step (1) into a loose network of metal fibers (2); a step 3 of sintering the metal fibers (2) to each other by one of the following processes c1 to c4: c1 : placing the plurality of metal fibers in a hot press (10) and subjecting the plurality of metal fibers (2) present in the hot press (10) to a predetermined pressure and temperature for a predetermined period of time to generate the network (6) by sintering the plurality of metal fibers (2) to each other to form contact points (7) between the metal fibers (2), wherein in process c1 the pressure is between 0 GPa and 20 GPa and the temperature is between 10% and 80% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement; c2: placing a loose network of metal fibers (2) between two hot plates and adjusting the distance between the two hot plates to 0.2 mm to 1 mm and heating the hot plates to a temperature of 10% to 80% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement; c3: ultrasonic welding; c4: hammering.

16. The network (6) of metal fibers (2) according to claim 15, wherein, In step 2, the metal fibers (2) are arranged using carding, deposition or sedimentation from a liquid dispersion or from a gas stream or by spraying.

17. An electrode comprising the network (6) according to any one of claims 1 to 10, 15 and 16.

18. A current collector (14) comprising the network (6) according to any one of claims 1 to 10, 15 and 16.

19. A battery, a half-cell (13a) or a plurality of half-cells separated by a membrane comprising the electrode according to claim 17.

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