Metal fiber network, method for producing a metal fiber network, electrode, and battery

Abstract

A metal fiber network, a method for manufacturing a metal fiber network, an electrode, and a battery are provided. [Solution] The present invention relates to a metal fiber network comprising a plurality of metal fibers bonded together, at least some of which 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 present invention also relates to a method comprising step 1 of producing a plurality of metal fibers (2) by melt spinning, step 2 of obtaining a loose network of the metal fibers (2) produced in step 1, and step 3 of bonding the plurality of metal fibers together by any one of the following processes c1 to c4: [Selected figure] Figure 3ai

Description

[Technical Field]

[0001] The present invention relates to a metal fiber network, a method for producing a metal fiber network, an electrode comprising a metal fiber network, and a battery having such an electrode. [Background technology]

[0002] The metal fiber network can improve the performance of secondary electrodes, as described below, and can also contribute to performance in catalytic materials, fuel cells, or hydrolysis, as a component of electromagnetic shielding materials, as filters, in polymer composites, as textured materials, or as textured hybrid materials that may include additives such as cotton, silk, or wool.

[0003] In lithium-ion batteries, the electrode active material is deposited on a metal foil that acts as the current collector. Typically, the negative electrode is a Li-ion battery on copper foil. x C n The cathode is made of a graphite intercalation compound and a Co, Ni, Mn, or Fe compound capable of absorbing Li cations, with aluminum foil as the current collector. During discharge, electrons are transferred to the copper current collector, and Li cations migrate from the graphite intercalation compound to the cathode. The aprotic electrolyte enhances Li cation mobility. Currently, much research and development is being focused on developing new anode and cathode materials.

[0004] Because the above reactions occur in the electrode active material, electrons must travel through the electrode active material to reach the current collector. Poor conductivity of the electrode active material limits the capacity of lithium-ion batteries. Therefore, a long electron path length, or the distance from the location where electrons are released in the active material to the current collector, also adversely affects the efficient charge-discharge process.

[0005] For this reason, attempts have been made to reduce the electrical resistance of electrode active materials by incorporating conductive materials such as carbon nanotubes. However, these additives tend to be sparsely dispersed in the electrode active material, which can lead to insufficient connection between the electrode active material and the current collector. As a result, the capacity of batteries incorporating carbon nanotubes into the electrode active material may not be fully improved.

[0006] To enhance the connectivity between these conductive additives, the composite of the active material and copper or aluminum foil is pressed under high mechanical force. This increases the electrical conductivity and mass density of the composite. However, mass density is crucial for Li-ion diffusion from the anode to the cathode and vice versa. If the composite is too dense, Li-ion diffusion will be restricted, hindering battery performance.

[0007] Furthermore, the use of conductive additives and binders in the electrode active material reduces the electrode active material, i.e., the material in which the electrochemical reaction occurs, which adversely affects battery performance.

[0008] It is also well known that the charge / discharge process involves volume changes in the active materials, resulting in structural degradation and capacity loss of the battery during use. Similarly, fabricating flexible lithium-ion battery assemblies remains a challenge, as mechanical deformation can threaten the performance of such batteries. Improving the flexibility of the electrodes without hindering their performance would not only open up new applications but also benefit the fabrication process itself.

[0009] A primary object of the present invention is to provide a current collector material suitable for improving battery performance. Another object of the present invention is to provide an electrode material suitable for providing a flexible electrode, and a battery utilizing the material suitable for improving battery capacity while improving battery charging kinetics and lifespan by exhibiting high resistance to degradation through flexibly deforming.

[0010] These objects are achieved by a network according to claims 1 and 16, a method for producing a metal fiber network according to the independent claims, an electrode and a battery.

[0011] Patent Document 1 states that a drawback of using metal foils, such as copper foil, as current collectors is that such collectors make the battery rigid and susceptible to damage from folding or bending. To provide flexible battery components, Patent Document 1 discloses porous substrates that can then be coated with a suitable electrode material slurry. The suitable electrode material slurry includes an active material, such as lithium iron phosphate for producing a lithium-ion cathode or lithium titanate for producing a lithium-ion anode, a conductive additive, and a binder in an organic solvent.

[0012] Patent Document 2 discloses another electrode for a secondary battery. The electrode is produced by introducing an electrode mixture containing an electrode active material into the pores of a current collector having a three-dimensional network structure. Patent Document 2 cites conductive metal felt as an example of this three-dimensional structure that is suitable for use in flexible batteries. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] International Publication No. 2017 / 222895 [Patent Document 2] International Publication No. 2018 / 048166 Summary of the Invention [Means for solving the problem]

[0014] The invention described herein utilizes a metal current collector material that provides an ultrafine, electronically conductive metal fiber network according to claim 1. The invention further relates to a method for producing a metal fiber network, an electrode, and a battery according to the independent claims. Surprisingly, the invention also allows the charge / discharge current to be significantly increased without destroying the battery.

[0015] Description of Metal Fiber Networks and Preferred Embodiments According to a first aspect of the present invention, there is provided a metal fiber network comprising a plurality of metal fibers bonded together, the metal fibers having a length of at least 1.0 mm, a width of at most 100 μm, and a thickness of at most 50 μm. The fibers may have a circular or oval cross-sectional area with a diameter of less than 100 μm, preferably less than 10 μm. In the case of an oval cross-section, the diameter is the average diameter. For example, the oval cross-section may be an ellipse.

[0016] The network of the present invention is flexible and can be repeatedly deformed without degradation of the network, i.e., without the deformation separating individual metal fibers from the metal fiber network. The metal fibers are fixed to one another, so that the metal fibers are in contact with one another; that is, the contact points are not movable relative to the metal fibers, as is the case with nonwoven entangled metal fiber aggregates, such as metal felt. As a result, the metal fiber network of the present invention is mechanically stable yet flexible. In this context, "mechanically stable" means that the metal fiber network is not a loose collection of metal fibers, i.e., the network does not collapse into individual metal fibers upon application of a small force. Thus, such a metal fiber network can be flexibly deformed without breaking. The metal fiber network can return to its original shape after deformation. However, the metal fiber network can also be bent to permanently assume a new shape.

[0017] When the 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, a network in which the metal fibers are bonded to one another can be produced without heating the metal fibers to near their melting points. Conventionally, higher temperatures are required to produce such a metal fiber network. Such high temperatures are typically near or above the melting point of the metal, which can melt or at least soften the metal fiber material to some extent, potentially resulting in the metal fibers forming a metal foil rather than the claimed network. Because the metal fiber network is not a metal foil, the structure of the metal fibers used to produce the metal fiber network can also be recognized in the metal fiber network. Therefore, in a cross-sectional view of the metal fiber network, voids are present between the metal fibers of the network fiber, even though they do not constitute metal fibers.

[0018] Preferably, before and / or after the metal fibers are bonded together, the metal fibers exhibit an exothermic phenomenon upon heating in a DSC measurement. An example of such an exothermic phenomenon is shown in FIG. 6d. In other words, the metal fibers are not in thermodynamic equilibrium at ambient temperature. Upon heating in a DSC measurement, the metal fibers can transition from a metastable state to a more thermodynamically stable state, such as by crystallization, recrystallization, or other relaxation processes that reduce defects in the metal atomic lattice. Observing an exothermic phenomenon in the metal fibers upon heating, such as in a DSC measurement (FIG. 6d), indicates that the metal fibers are not in thermodynamic equilibrium; for example, the metal fibers may be in an amorphous or nanocrystalline state that contains defect energy and / or crystallization energy that is released as the metal fibers undergo crystallization or recrystallization upon heating. Such a phenomenon can be recognized, for example, using DSC measurements (FIG. 6d). Surprisingly, it has been found that metal fiber networks in which the metal fibers exhibit such an exothermic phenomenon exhibit improved strength and electrical conductivity after the metal fibers are bonded together, such as by sintering or welding. In the context of this disclosure, the terms "sintering" and "welding" can be used interchangeably, i.e., they have the same meaning.

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

[0020] To ensure high electrical conductivity throughout the network, it is preferable that the metal fibers remain electrically connected to each other at the points where they are bonded to each other (i.e., contact points) even when the network is deformed. To ensure that the metal fibers are bonded to each other in a manner that is both electrically conductive and mechanically stable, it is more preferable that at least some of the metal fibers in the network of the present invention are sintered to each other, i.e., that the connections between the metal fibers are formed by the material of the metal fibers. In this case, metal atoms of two contacting metal fibers bond to each other, thereby firmly connecting the metal fibers, resulting in a network with good electrical conductivity and durability while being flexible. In this regard, it is particularly preferable that the metal fibers are sintered to other metal fibers, and most preferably, they are sintered directly to other metal fibers without the addition of a binder such as a polymer binder. It is most preferable that the bonding between one metal fiber and another is achieved by the material of the metal fiber. Therefore, it is more preferable that the metal fibers are bonded to each other without a polymer binder, as such polymer binders often have poor electrical conductivity and high-temperature performance. If the metal fibers are sintered directly to one another, solder materials etc. may also be omitted in the network according to the invention.

[0021] It is also preferable to bond the metal fibers to each other by ultrasonic welding or hammering. Ultrasonic welding and hammering are simple methods that can be used to rapidly bond the metal fibers to each other. When bonding the metal fibers to each other using ultrasonic welding or hammering, it is possible to produce a metal fiber network in which the bonding of the metal fibers is not uniform over the entire surface of the network, but is limited to isolated regions distributed throughout the metal fiber network. For this purpose, it is particularly preferable to structure the compression molding tool for ultrasonic welding or hammering. For example, the compression molding tool for ultrasonic welding or hammering may have multiple protrusions, such as needle-like pinnacles or rims. With such multiple protrusions, separate regions in which the metal fibers are bonded to each other can be created in a single operation. Between such separate regions, the metal fibers may have contact points but are not bonded to each other. As mentioned above, this can improve the flexibility of the entire metal fiber network. Therefore, it is preferable that the network include regions in which the metal fibers have contact points but are not bonded to each other, and that the network include regions in which the metal fibers have contact points where they are bonded to each other.

[0022] According to one embodiment, at least some of the metal fibers of the plurality of metal fibers are amorphous. According to another embodiment, at least some of the metal fibers of the plurality of metal fibers are nanocrystalline. Amorphous and nanocrystalline metal fibers can be combined in the metal fiber network. Nanocrystalline metal fibers contain crystalline domains. Upon heating to a temperature that is about 20-60% of the melting temperature of the nanocrystalline metal fibers, these domains recrystallize, resulting in an increase in the average size of the crystalline domains compared to the average size of the initial crystalline domains in the nanocrystalline metal fibers before heating. Non-equilibrated fibers (e.g., nanocrystalline or amorphous fibers) can also be mixed with equilibrated fibers (e.g., annealed fibers).

[0023] As described above, the metal fibers preferably exhibit an exothermic phenomenon when heated in DSC measurement before and / or after being bonded to each other. The degree of the exothermic phenomenon observed when the metal fibers are heated is not particularly limited. The amount of energy released in the exothermic phenomenon is preferably 0.1 kJ / g or more, more preferably 0.5 kJ / g or more, even more preferably 1.0 kJ / g or more, and most preferably 1.5 kJ / g or more. The absolute amount depends greatly on the metal or metal alloy used. The degree of the exothermic phenomenon can be determined by comparing the DSC measurement values ​​of the metal fibers before and after thermal equilibrium.

[0024] Amorphous and nanocrystalline metal fibers can be produced by melt spinning using equipment and methods for producing metal strands by melt spinning. Examples include those described in the examples of European Patent Application No. 19175749.1, International Publication No. WO 2016 / 020493, and International Publication No. WO 2017 / 042155, the contents of which are incorporated herein by reference with respect to the methods for forming and resulting in the metal fibers. Thus, the metal fibers can be, for example, Cu, Cu 99 Si1, Cu 96 Si4, Al, Al 99 Si1, Fe 40 Ni 40 B 20 , Au, Ag, Pb, Si, or stainless steel V2A metal fibers.

[0025] The metal fibers are preferably produced by melt spinning. Such melt-spun metal fibers can contain spatially restricted domains of high energy state due to the rapid cooling that occurs during the melt spinning process. Therefore, such metal fibers can be sintered together at temperatures significantly lower than the melting temperature of the metal fibers by activating the structural transition of these high-energy domains. The energy released from the domains by the structural transition is used to activate the sintering process. Therefore, such metal fibers can be sintered together at temperatures lower than the crystallization temperature of the metal fiber material and even significantly lower than its melting temperature. This is particularly advantageous when the metal fibers are coated with a coating layer that is sensitive to high temperatures. Higher temperatures can cause the fibers to crystallize, destroying their amorphous or nanocrystalline state and thereby destroying their special mechanical properties of high elasticity and low brittleness. The high-energy domains can release energy when heated or when mechanically compressed by a press, hammer, or ultrasonic welding device. The release of energy from such domains can be observed as an exothermic phenomenon.

[0026] The metal fibers are formed from or at least contain a metal. The present invention is not particularly limited as to which metal the metal fibers contain or are made from. Nevertheless, it is preferred that the metal fibers of the plurality of metal fibers in the network contain one 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 containing one or more of these. It is even more preferred that the metal fibers of the plurality of metal fibers in the network contain one element selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, iron, vanadium, aluminum, silicon, lithium, combinations thereof, and alloys containing one or more of these.

[0027] It is particularly preferred that the metal fibers are made of copper, aluminum, or a stainless steel alloy. Different types of metal fibers can be combined with one another, so that the network contains, for example, metal fibers made of copper, one or more stainless steel alloys, and / or aluminum. Particularly preferred are metal fiber networks in which the metal fibers are made of copper, aluminum, cobalt, or alloys containing copper, aluminum, silicon, and / or cobalt. Examples of aluminum and cobalt alloys include Al 99 Si1 and Co 66 Fe4Mo2B 12 Si 16 Examples of copper alloys include CuSi1, CuSi 4、 or CuSi 12 Examples include:

[0028] The length of the metal fibers is preferably 2.0 mm or more, more preferably 10 mm or more, even more preferably 20 mm or more, and even more preferably 70 mm or more. When the length of the metal fibers satisfies the above length requirement, the mechanical stability of the metal fiber network is improved. This is because the longer the length of the metal fibers, the more contact points each metal fiber has with other metal fibers in the network, where they are fixed to each other, forming mechanically strong conductive connections. Therefore, even if one connection between metal fibers is broken, the network can be held together by multiple other inter-fiber connections to achieve the desired conductivity, so the structural integrity of the entire network is not compromised and the metal fibers are not separated from the network. To facilitate fiber placement by carding, the fiber length should preferably be in the range of 1 to 20 cm, more preferably 3 to 15 cm, and even more preferably 4 to 8 cm.

[0029] The width of the metal fibers is preferably 80 μm or less, more preferably 70 μm or less, even more preferably 40 μm or less, and most preferably 5 μm or less. Additionally, the thickness of the metal fibers is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, and most preferably 5 μm or less. Instead of a rectangular cross section, the fibers can have a circular or elliptical cross section with the above dimensions. By using metal fibers that generate heat when heated or mechanically pressed, a network in which the metal fibers are bonded to each other can be produced without heating the metal fibers to temperatures near their melting points. In other words, when the metal fibers are bonded to each other by sintering or other methods, a temperature-sensitive coating can be applied to the fibers for protection. Furthermore, avoiding the high temperatures required to bond the fibers to each other reduces the risk of the metal fibers becoming metal foil during the production of the network.

[0030] There are no particular lower limits on the width and thickness of the metal fibers, but the metal fibers may have a width of 1 μm or more, preferably 3 μm or more, and a thickness of 1 μm or more.

[0031] In the metal fiber network of the present invention, it is also preferred that most of the metal fibers in the network are in contact with one or more of the remaining metal fibers. This ensures high conductivity throughout the network. It is even more preferred that the network is an irregular network. Such an irregular network has good conductivity in all directions. Furthermore, irregular metal fiber networks are easier to manufacture than regular fiber networks. It is even more preferred that the fibers in the network are combed in various directions, so that while individual fibers have directionality, the conductivity of the network is equally oriented in all possible directions. Therefore, it is preferred that some or all of the fibers in the network have orientation, i.e., the longitudinal axes of the fibers are not randomly oriented, but have a predominant orientation in one or more spatial directions.

[0032] In the metal fiber network according to the present invention, it is particularly preferred that the metal fibers are bonded to one another at contact points that are randomly distributed throughout the metal fiber network. According to another aspect of the present invention, it is preferred that the contact points are not randomly distributed but are, for example, located in the peripheral region of the metal fiber network, or that the metal fibers are regularly distributed, resulting in regular contact points. It is even more preferred that the contact points at which the metal fibers are bonded to one another are unevenly distributed in specific regions and are not evenly distributed throughout the entire metal fiber network. If the contact points at which the metal fibers are bonded to one another are only present in separate regions, it is possible to increase the flexibility of the fibers between those regions while ensuring mechanical stability and good electrical conductivity.

[0033] In the metal fiber network according to the present invention, it is further preferred that the metal fibers are fixed to each other at contact points where the metal fibers contact each other, and each of the metal fibers preferably has at least two, more preferably at least three, and even more preferably at least four contact points with other metal fibers.

[0034] In the metal fiber network according to the present invention, it is particularly preferred that the metal fibers are fixed to one another at contact points, and that the contact points are distributed throughout the network, so that contact points are present throughout the three-dimensional structure of the metal fiber network. Therefore, the contact points are not provided only in specific regions of the metal fiber network, such as the center or periphery of the network. The contact points may be evenly distributed throughout the network. Alternatively, there may be a gradient in the density of contact points throughout the network. That is, the network may have regions with a higher contact density and regions with a lower contact density. The spatial distribution of the contact points may be regular or random.

[0035] The network of the present invention preferably has open pores between the metal fibers. The porosity of the network is preferably 95% by volume or less. It is also preferable that the porosity of the network is greater than 80% by volume. It is even more preferable that the porosity is in the range of 80% to 95% by volume. An active material, such as an electrode active material or an active catalytic material, can be incorporated into the open pores. It is even more preferable that in the network of the present invention, at least some of the metal fibers are at least partially coated. This coating may be, for example, an active material, such as an electrode active material that interacts with Li ions in a battery, or a catalytic active material that converts CO to CO2 or is active in hydrolysis. The metal fibers may also be coated with a coating that improves adhesion between the metal fibers and thereby increases the mechanical strength of the network.

[0036] For example, electrode active materials for such batteries include graphite, silicon, silicon carbide (SiC), tin oxide (SnO), tin dioxide (SnO), and lithium titanium oxide (LiTiO) for the anode. 12 ), and for the cathode, lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCoO2), and lithium iron phosphate (LFP).

[0037] It is particularly preferred that the coating contains an active material for a secondary battery electrode. A metal fiber network with a coating containing such an active material for a secondary battery electrode can be used to obtain a flexible secondary battery with increased capacity. Furthermore, the use of 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 another preferred embodiment of the present invention, the metal fiber network comprises metal fibers coated with a coating containing at least one catalytically active material. Such a network can be used as a catalyst. In particular, when the network has open pores and the metal fibers are coated with a coating containing at least one transition metal, a gaseous or liquid fluid can flow through the network, allowing compounds contained in the fluid to come into contact with the coating on the metal fibers, resulting in a catalytic reaction. Suitable metal alloys, such as nickel fibers, can also function as catalytic materials themselves.

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

[0040] In the network according to the present invention, it is further preferred that the plurality of metal fibers form a network of interconnected pores.

[0041] More preferably, the coating on the plurality of metal fibers is in electrical contact with the plurality of metal fibers. This is particularly beneficial when the network is used as an electrode material for a fuel cell, in a hydrolysis system, or in a battery. Networks containing metal fibers coated with a coating containing an element suitable for catalyzing an electrochemical reaction occurring in an electrode of a fuel cell or battery can transport electrons to or from reaction sites. Thus, such networks can be used to improve the performance of fuel cells or batteries.

[0042] The thickness of the network of the present invention is not particularly limited. However, the network thickness is preferably 0.01 mm or more. The network thickness is more preferably 0.03 mm or more, even more preferably 0.05 mm or more, even more preferably 0.07 mm or more, and most preferably 0.1 mm or more. If the network thickness is less than 0.01 mm, the mechanical stability of the network may be insufficient. The upper limit of the network thickness is not particularly limited. However, depending on the application, the upper limit may be 3.0 mm or less or 2.5 mm or less. For battery applications, the network thickness is most preferably in the range of 0.1 mm to 0.5 mm. A network with a thickness in this range is advantageous for manufacturing a battery by stacking and winding the network coated with an active material. It is also preferable for diffusing Li ions within a reasonable time.

[0043] The present invention also relates to a metal fiber network comprising a plurality of metal fibers bonded together, said metal fiber network being formed by applying a molten material for forming said metal fibers to said metal fiber network. 2 K·min -1The metal fibers are obtained by a process comprising: step 1, in which a plurality of metal fibers having a length of 1.0 mm or more, a width of 100 μm or less, and a thickness of 50 μm or less are produced by subjecting the metal fibers to a cooling rate of 1.0 mm or more; step 2, in which the metal fibers obtained in step 1 are arranged to form a loose metal fiber network; and step 3, in which the metal fibers are sintered together by one of the following processes c1 to c4. c1: The network is produced by placing the plurality of metal fibers in a heat press and subjecting the plurality of metal fibers in the heat press to a predetermined pressure and temperature for a predetermined time, thereby sintering the plurality of metal fibers together and forming junctions between the metal fibers where the metal fibers are fixed to each other. In process c1, the pressure is 0 to 20 GPa, preferably at least 20 MPa, and the temperature is 10 to 95% of the melting temperature of the material of the metal fibers, which is determined by DSC measurement. c2: The loose metal fiber network is placed between two heating plates, the distance between the two heating plates is adjusted to 0.1-1 mm, and the heating plates are heated to a temperature that is 10-95% of the melting temperature of the material of the metal fiber, which is determined by DSC measurement. c3: Ultrasonic welding. c4: Hammering.

[0044] In step 1, the metal fibers are produced from the melt with a controlled length of at least 1 mm. If the fibers are entangled or not sufficiently uniform in length, they are further processed using techniques developed to recycle carbon fibers (Henrik Dommes, "Vom Faserabfall zum hochwertigen Leichtbau Halbzeug", Lightweight Design 2010, 3, 23-27; doi:10.1007 / BF03223621). Thus, the fibers can be cut to the desired length with a mechanical cutting tool or a laser, disentangled, and partially oriented.

[0045] In step 2, the metal fibers produced in step 1 are arranged in a random array by settling from a dispersion or by airflow (step 2 b2 in Figure 27). A regular array of metal fibers is formed by carding (step 2 b1 in Figure 27). In this way, a felt-like structure is formed, as is standard in fiber processing of nonwoven fabrics by carding or the like.

[0046] Therefore, in another aspect, the present invention relates to a method for producing a metal fiber network having welded or sintered contacts between the fibers, comprising steps 1 and 2 of obtaining a plurality of metal fibers and a net, and step 3 of connecting the filaments to form a consolidated porous nonwoven felt-like structure.

[0047] In step 3 (step 3 in FIG. 27), the loose felt of random metal filaments (also referred to as a loose metal fiber network) obtained in steps 1 and 2 is subjected to one of processes c1 to c4. For example, the network is produced by placing the loose felt in a heat press (c1 and c2 in step 3 in FIG. 27) and subjecting it to a predetermined pressure and temperature for a predetermined time, thereby welding the metal fibers at their contact points and forming a network of cross-linked metal fibers. The metal fibers in the heat press are subjected to a predetermined pressure and temperature for a predetermined time, thereby sintering the metal fibers to each other and forming contact points between the metal fibers, thereby producing the network. The pressure is 0 to 2 GPa, preferably at least 20 MPa, and the temperature is 10 to 95% of the melting temperature of the material of the metal fibers, which can be determined by DSC measurement, for example, by monitoring the recrystallization temperature. Those skilled in the art can determine the appropriate temperature for sintering the metal fibers to each other in step 3 based on the DSC measurement. Those skilled in the art will understand that the features relating to steps 1 to 3 can be combined with the features described below, with the features described in the claims relating to steps 1 to 3, and with all features described in the claims relating to the metal fiber network above, below, and above.

[0048] In process c2 of step 3, when adjusting the distance between the heating plates, it is preferable that the loose network of the metal fibers 2 is compressed to form contact points between the metal fibers.

[0049] In another embodiment of step 3, if the compression tool has a structured contact surface, such as protrusions such as needle-like pinnacles or a rim pattern (c3, c4 in step 3 of Figure 27; protrusions not shown in Figure 27) opposite a flat surface, the network structure can be tailored at various length scales. In this case, the distance between fiber bonds is controlled by the density of the fibers in the area where the tool or its protrusions compress the felt, but if the compression tool does not hit the network or does not have protrusions, no welds will form at the contact points of the metal fibers. When the tool is structured, the average porosity and flexibility of the metal fiber network can be improved.

[0050] The fiber length should preferably be in the range of 1 to 20 cm, more preferably in the range of 3 to 15 cm, and even more preferably in the range of 4 to 8 cm. Fibers of the above-mentioned length can be easily arranged by carding.

[0051] In a modified procedure, the temperature required to weld the filaments into a consolidated felt, i.e., a network of the present invention, can be reduced if, instead of continuously compressing the filaments, the filaments are welded by hammer strokes (step 3, c4 in FIG. 27 ), in which shock waves can reach extremely high peak pressures associated with localized heating. Such hammer strokes can be applied as ultrasonic, i.e., ultrasonic welding, with the vibration direction perpendicular to the felt (step 3, c3 in FIG. 27 ). In the case of hammer stroke or ultrasonic welding, as described above, the compression molding tool preferably has a structured surface with multiple protrusions, such as needle-like pinnacles or rims. As described above, such a structured compression molding tool can be used to produce a network of the present invention in which the metal fibers are bonded to each other only in multiple discrete regions at the contact points, and thus the metal fibers may have contact points but are not bonded to each other between the discrete regions. The regions in which the metal fibers are not bonded to each other can improve porosity and also the flexibility of the metal fiber network.

[0052] Each area where the metal fibers are bonded to one another and / or each area where the metal fibers are not bonded to one another is at least 1 mm in size. 2 More preferably, it is at least 2 mm 2 , more preferably at least 5 mm 2 In particular, the size of each region where the metal fibers are bonded to each other and / or each region where the metal fibers are not bonded to each other is at least 1 mm 2 In this case, it is more preferable that the regions where the metal fibers are bonded to each other form an island structure and are surrounded by sea-like regions where the metal fibers are not bonded to each other. Alternatively, it is particularly preferable that the size of each region where the metal fibers are not bonded to each other and / or each region where the metal fibers are bonded to each other is at least 1 mm 2In this case, it is also preferable that the regions in which the metal fibers are not bonded to each other form an island-like structure and are surrounded by a sea-like region in which the metal fibers are bonded to each other.

[0053] In all of processes c1-c4, the entire fiber is maintained at a temperature significantly lower than the melting point, with sintering occurring only at the contact points between the fibers. This ensures that the fiber structure does not collapse. In any case, welding of the contact points between different filaments is improved and facilitated because the quenched fiber, such as that obtained by melt spinning, is not in thermal equilibrium and contains amorphous and / or nanocrystalline domains that are more susceptible to atomic rearrangement than equilibrated crystalline domains.

[0054] In the method of the present invention, the pressure applied in step c1 keeps the temperature significantly lower than the melting temperature of the metal fiber material, simultaneously forming strong bonds between the metal fibers and resulting in a stable metal fiber network. In all of steps c1 to c4 of the method of the present invention, atomic diffusion induced by thermal energy is suppressed and atomic diffusion induced by mechanical pressure is increased. This mechanism allows for the production of a stable metal fiber network in which the metal fibers are permanently sintered together at low cost without carefully controlling the applied temperature. If the temperature is higher than 95% of the melting temperature of the metal fiber material, the metal fibers may turn into metal foil. On the other hand, if the temperature is lower than 10% of the melting temperature of the metal fiber material, the atomic mobility becomes too low, resulting in insufficient sintering of the metal fibers in the method, and thus failing to produce a stable metal fiber network or requiring an excessively long time.

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

[0056] It should be understood that all aspects of the metal fiber network described above, and in particular those relating to the metal fibers, constitute preferred embodiments in view of the method according to the invention.

[0057] In the method of the present invention, the resulting metal fibers preferably have a length in the range of 1 to 20 cm, more preferably in the range of 3 to 15 cm, and even more preferably in the range of 4 to 8 cm, a width of 100 μm or less, a thickness of 50 μm or less, or a circular or elliptical cross section. It should be understood that the same dimensions for the length, width, and thickness of the metal fibers as those given for the description of the network are also preferred in the method of the present invention. It has been observed that stable metal fiber networks can be produced using such fibers without heating the metal fibers to their melting temperature.

[0058] In the method according to the present invention, the temperature to be applied depends on the material of the metal fibers. To avoid the crystallization of amorphous metal fibers during the welding process, it is preferable to keep the temperature below the crystallization temperature of these fibers. The crystallization temperature can be determined by differential scanning calorimetry (DSC) measurements on the metal fibers in question. DSC measurements are performed at a starting temperature of 30°C and a heating rate of 10 Kmin. -1 to 1200°C, followed by a cooling rate of 10 km / min -1 The DSC measurement was carried out under the conditions of 100 ml / min under an argon atmosphere. -1 This is done using a zirconium oxygen scavenging system (STA 449 F3 Jupiter, Netzsch Bj. 2017) for a completely oxygen-free atmosphere at a constant argon flow rate of 1000 kJ / min.

[0059] In the method according to the present invention, the time for which the metal fibers are subjected to the predetermined time and pressure is not particularly limited and depends on the material of the metal fibers, the applied pressure, and the temperature. However, to ensure that the metal fibers are sufficiently sintered together, the predetermined time in steps c1 and c2 is preferably 10 seconds or longer, more preferably 1 minute or longer, even more preferably 2 minutes or longer, even more preferably 3 minutes or longer, and most preferably 5 minutes or longer. There is no particular upper limit to the time for which the metal fibers are subjected to the predetermined temperature and pressure in step b, but from an economical point of view, the time is preferably 60 minutes or shorter, more preferably 45 minutes or shorter, and most preferably 30 minutes or shorter.

[0060] To ensure stable connections between the metal fibers in the entire network, it is preferred that the pressure and heat in process c1 be applied for at least 1 minute.

[0061] The pressure applied in processes c1 and c2 is preferably 20 MPa or more, more preferably 30 MPa or more, even more preferably 100 MPa or more, and most preferably 120 MPa or more. Depending on the metal alloy and melt spinning process, lower pressures may be possible. The upper limit of the pressure is not particularly limited. However, to avoid the metal fibers from turning into metal foil, the pressure is preferably 1,000 MPa or less, more preferably 750 MPa or less, even more preferably 500 MPa or less, and most preferably 300 MPa or less.

[0062] To produce a network containing coated metal fibers, in principle, the coated metal fibers can be obtained after step 1 or 2, or a step 4 can be carried out to coat the metal fibers. In this case, step 4 is preferably carried out after step 3. If step 4 is carried out after sintering in step 3, it is possible to produce a basic network for many applications. In the subsequent step 4, a suitable coating can be provided on the metal fibers, allowing the network to be modified depending on the intended application. Furthermore, if step 4 is carried out after step 3, it is possible to provide a coating on the metal fibers that would be sensitive to the conditions applied during sintering and / or welding in step 3. This is the case, for example, if the coating has a low melting point and would melt when subjected to the conditions of step 3.

[0063] In the method according to the present invention, the metal fibers are preferably produced by melt spinning. Such melt-spun metal fibers contain spatially restricted domains of high energy due to the quenching that occurs during the melt spinning process. In this regard, quenching refers to the process of 2 K·min -1 More than 10, preferably 4 K·min -1 More than 10, more preferably 5 K·min -1 This refers to a cooling rate equal to or greater than the melting temperature of the metal fibers. Therefore, such metal fibers can be sintered together while keeping the temperature in step 3 significantly lower than the melting temperature of the metal fibers. Such metal fibers can even be sintered together at a temperature lower than the crystallization temperature of the material of the metal fibers. This is particularly advantageous when the metal fibers are coated with a coating layer that is sensitive to high temperatures. In view of the above, the metal fibers of the metal fiber network according to the present invention can be sintered together by melt spinning the molten material of the metal fibers to a temperature of 1000°C. 2 K·min -1 It is preferable that the above cooling rate is used.

[0064] In the method of the present invention, the temperature applied in step 3 is preferably 80% or less, more preferably 70% or less, even more preferably 60% or less, and most preferably 50% or less of the melting temperature of the metal fiber material. The temperature applied in step 3 may even be 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 the metal fibers turning into a metal foil is reduced. The temperature is preferably 10% or more, more preferably 20% or more, even more preferably 25% or more, and most preferably 30% or more of the melting temperature of the metal fiber material. If the temperature in step 3 is lower than these limits, the mobility of the atoms in the metal fiber decreases, increasing the risk that the metal fibers will not be sufficiently sintered together and a stable metal fiber network will not be obtained. However, the lower limit depends on the metal or metal alloy and may even be lower than 20% of the melting temperature.

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

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

[0067] The method for producing the metal fiber network further preferably includes a step of at least partially filling the voids between the metal fibers in the network with an active material, in particular an electrode active material or a catalytic material. The step of filling the voids between the metal fibers is shown schematically in Figure 27.

[0068] It is particularly preferred that after producing a metal fiber network by the method of the present invention, the network is cut into a shape suitable for the desired application. Cutting may be performed before or after the coating step, or even if no coating step is intended to be performed. When cutting is performed after forming the metal fiber network, it is easy to produce a metal fiber network of the desired shape.

[0069] Description of Electrodes Comprising Metal Fiber Networks and Preferred Embodiments As mentioned above, another aspect of the present invention relates to an electrode comprising a network, preferably produced according to or obtained by the method described above. As mentioned above, it is particularly preferred that the metal fiber network forming part of the electrode is separated from the network by cutting or the like.

[0070] It is particularly preferred that the electrode comprises the network as a current collector.

[0071] It is further preferred in the electrode according to the invention if the voids between the metal fibers in the network are at least partly filled with an active material, in particular an electrode active material or catalytic material.

[0072] Batteries with electrodes containing metal fiber networks and description of preferred embodiments Another aspect of the invention relates to a battery having electrodes as described above, wherein 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 discharged.

[0073] The porous structure of the metal fiber network allows for a relatively large volume to be occupied by the electrode active material, which is not present in commonly used metal foils. Therefore, the amount of electrode active material can be significantly increased without sacrificing capacity due to increased electrical resistance caused by a large amount of electrode active material. Furthermore, by using the metal fiber network, the active material is distributed throughout the current collector. Therefore, electrons only need to traverse a short distance between the active material and the current collector. Due to the generally higher electrical conductivity and connectivity between the active material and the electrode, the electrode material does not need to be compressed as much as when using a metal foil as an electrode, thereby enhancing Li-ion diffusion. As a result, the charging time of the battery can be significantly reduced, and the use of additives such as carbon black and binders can be reduced, allowing for the incorporation of more active material into the battery electrode, further improving the battery's performance. The flexibility and stability of the metal fiber network enable the creation of durable electrodes, resulting in longer-lasting batteries. Additionally, batteries utilizing electrodes according to the present invention have improved battery charging kinetics due to the three-dimensional nature of the metal network that permeates the electrode active material, thereby reducing the distance that electrons and charge carriers must travel from their origin within the active material to the metal current collector, from where they are dispersed to the circuit.

[0074] The battery according to the present invention is preferably a secondary battery, more preferably a lithium ion battery. 99 Si1, Cu 98 Si2, Cu 96 Si4, Cu 88 Si 12 , or Cu 92 A network of copper metal fibers or copper alloy fibers such as Sn8, or Al 99 It is also preferred that the material is a network of aluminum metal fibers or aluminum alloy fibers such as Si1. Compared to the pure metals, copper alloys and aluminum alloys have almost the same electrical conductivity, but the manufacturing conditions for the fibers by melt spinning are good.

[0075] It is also preferred to provide a metal fiber network in which the metal fibers are formed from aluminum for the cathode of a secondary battery or copper for the anode of a secondary battery. Such a network can be impregnated with a lithium active material and used as an electrode. In this case, the distance between the current collector and the active material can be reduced, which is beneficial to battery performance.

[0076] Therefore, it is particularly preferred that the battery according to the invention has an electrode comprising a network of copper or copper alloy metal fibers. It is also particularly preferred that the battery according to the invention has an electrode comprising a network of aluminum or aluminum alloy metal fibers. It is also preferred that the battery according to the invention has a first electrode comprising a network of copper or copper alloy metal fibers and a second electrode comprising a network of aluminum or aluminum alloy metal fibers. In some cases, two or more electrodes of the same or different metal fiber materials can be used.

[0077] While the present disclosure focuses on the metal fiber networks and their use as electrode materials, it is also preferred to use the metal fiber networks described herein in catalytic materials, fuel cells, hydrolysis, as components of electromagnetic shielding materials, filters, polymer composites, and as textured materials and textured hybrid materials that may include additives such as cotton, silk, or wool.

[0078] The invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0079] [Figure 1a] FIG. 1 is a schematic diagram of a vertical melt spinning apparatus. [Figure 1b] FIG. 1 is a schematic diagram of a horizontal melt spinning apparatus. [Figure 1c]1 is a photographic image taken from a video of a melt of Al99Si1 alloy being deposited onto a rotating wheel. [Figure 2a] 1 is a photographic image of copper metal fibers. [Figure 2b] 1 is a photographic image of cobalt metal fibers. [Figure 2c] 1 is a photographic image of metal fibers of Al99Si1 alloy. [Figure 2d] 1 is a photographic image of metal fibers of Co66Fe4Mo2B12Si16 alloy. [Figure 3ai] 1 is a photographic image of Co66Fe4Mo2B12Si16 alloy metal fibers produced at a wheel speed of 50 m / s. [Figure 3aii] The average thickness of the Co66Fe4Mo2B12Si16 alloy metal fibers is shown. [Figure 3aiii] The average width of the Co66Fe4Mo2B12Si16 alloy metal fibers is shown. [Figure 3bi] 1 is a photographic image of Co66Fe4Mo2B12Si16 alloy metal fibers produced at a wheel speed of 25 m / s. [Figure 3bii] The average thickness of the Co66Fe4Mo2B12Si16 alloy metal fibers is shown. [Figure 3biii] The average width of the Co66Fe4Mo2B12Si16 alloy metal fibers is shown. [Figure 4a] 1 is an X-ray diffraction pattern of copper metal fiber. [Figure 4b] 1 shows an X-ray diffraction pattern of Al99Si1 alloy metal fiber. [Figure 4c] 1 is an X-ray diffraction pattern of Co66Fe4Mo2B12Si16 alloy metal fiber. [Figure 5a] 1 is a scanning electron microscope (SEM) photograph of copper metal fibers. [Figure 5b] FIG. 5b is an enlarged view of FIG. 5a. [Figure 5c] 1 is a scanning electron microscope photograph of Al99Si1 alloy metal fiber. [Figure 5d] This is an enlarged view of Figure 5c. [Figure 5e]1 is another scanning electron microscope photograph of an Al99Si1 alloy metal fiber. [Figure 5f] This is a scanning electron microscope photograph of gold metal fibers. [Figure 5g] 1 is a scanning electron microscope photograph of Cu92Sn8 alloy metal fiber. [Figure 5h] 1 is a scanning electron microscope photograph of Cu96Si4 alloy metal fiber. [Figure 6a] The thickness and width of 527 Al99Si1 alloy metal fibers produced at a wheel speed of 25 m / s are shown. [Figure 6b] The thickness distribution of 527 Al99Si1 alloy metal fibers fabricated at a wheel speed of 25 m / s is shown. [Figure 6c] The width distribution of 527 Al99Si1 alloy metal fibers produced at a wheel speed of 25 m / s is shown. [Figure 6d] DSC measurements of CuSn8 microfibers after melt spinning (curve I) and after thermal equilibration (curve II) are shown, illustrating the heat generation process when the melt-spun fiber is heated compared to the equilibrated metal fiber. [Figure 7] 1 is an SEM image of a Co66Fe4Mo2B12Si16 alloy metal fiber network according to the present invention after sintering (network of Example 2). [Figure 8] 1 is a photographic image of a sintered Co66Fe4Mo2B12Si16 alloy metal fiber network according to the present invention before deformation. [Figure 9] 9 is a photographic image of the network of FIG. 8 in a deformed state. [Figure 10] 1 is a photographic image of a copper metal fiber network according to the present invention sintered at a temperature of 300° C. and a pressure of 177 MPa for 5 minutes (network of Example 9). [Figure 11] 1 is a photographic image of a copper metal fiber network according to the present invention sintered at a temperature of 300° C. and a pressure of 177 MPa for 3 minutes (network of Example 10). [Figure 12] FIG. 12 is an SEM image of the network shown in FIG. [Figure 13]13 is a magnified SEM image of the network shown in FIGS. 11 and 12. [Figure 14a] 1 is a photographic image of a Cu92Sn8 alloy metal fiber network according to the present invention sintered at a temperature of 300° C. and a pressure of 78 MPa for 3 minutes (network of Example 11). [Figure 14b] FIG. 14a is an SEM image of the network in FIG. [Figure 14c] FIG. 14b is a magnified SEM image of the network shown in FIG. [Figure 15] FIG. 1 is a schematic diagram of a heat press. [Figure 16a] 1 is a schematic diagram of a battery according to the present invention. [Figure 16b] FIG. 1 is a schematic diagram of a reference battery according to the prior art. [Figure 17] 1 shows a comparison of the capacity of a battery according to the present invention and a reference battery according to the prior art. [Figure 18] 1 is a graph showing the charge-discharge profile of a reference cell obtained by chronopotentiometry. [Figure 19] 1 is a graph showing the charge-discharge profile of the network cell of the present invention obtained by chronopotentiometry. [Figure 20a] 19 is a graph showing the second and final charge-discharge profiles of the reference cell shown in FIG. 18 obtained by chronopotentiometry. [Figure 20b] 20 is a graph showing the second and final charge-discharge profiles of the network cell of the present invention obtained by chronopotentiometry shown in FIG. 19. [Figure 21a] 1 is a graph of current normalized against time of charge / discharge profiles of a network cell of the present invention and a reference cell obtained by chronopotentiometry. [Figure 21b] FIG. 21b is an enlarged view of the graph of FIG. 21a, showing the first cycle. [Figure 21c] FIG. 21b is an enlarged view of the graph of FIG. 21a, showing the region near the final cycle of the reference cell. [Figure 22] 1 is a graph showing capacity versus cycle number for a network cell and a reference electrode of the present invention. [Figure 23]Figure 23a is an SEM image of an electrode of the invention showing graphite flakes in the fiber network, Figure 23b shows an EDX mapping of copper for the electrode of the invention shown in Figure 23a, and Figure 23c shows an EDX mapping of carbon for the electrode of the invention shown in Figure 23a. [Figure 24] 1 is a scheme illustrating an example of a carding machine for forming a metallic fleece. [Figure 25] 1 is a photographic image of a manufacturing process according to the present invention in which metal fibers are formed into a fleece and combined with a cotton fleece. [Figure 26] Figure 1 shows a copper-based fleece that has been mechanically stabilized by ultrasonic treatment. [Figure 27] FIG. 1 is a diagram showing a schematic representation of a process according to the present invention.

[0080] For clarity, some figures may not show all or any reference numbers. DETAILED DESCRIPTION OF THE INVENTION

[0081] Figure 1a shows a schematic diagram of a melt spinning apparatus 1 that can be used to produce metal fibers 2 suitable for forming a network according to the present invention. The melt spinning apparatus 1 has a vertical rotating wheel 3 that can rotate about an axis Z. Above the rotating wheel 3 is arranged a microstructured nozzle 4, through which droplets 5 of the melt of the material from which the metal fibers 2 are made can be deposited onto the rotating wheel 3. Alternatively, a horizontal melt spinning apparatus can be used (Figure 1b; a horizontal melt spinning apparatus is disclosed in European Patent Application No. 19175749.1, the contents of which are incorporated herein by reference).

[0082] FIG. 1b shows a schematic diagram of a horizontal melt spinning apparatus 1, which can also be used to form metal fibers 2. In contrast to the melt spinning apparatus 1 shown in FIG. 1a, the melt spinning apparatus 1 shown in FIG. 1b has a horizontal rotating wheel 3. As with the melt spinning apparatus 1 shown in FIG. 1a, in the melt spinning of FIG. 1b, the wheel 3 can rotate about an axis Z. A microstructured nozzle 4 is arranged above the rotating wheel 3, through which droplets 5 of the melt of the material from which the metal fibers 2 are produced can be deposited onto the rotating wheel 3.

[0083] Figure 1c shows the Al 99 This photograph shows the production of Si1 alloy metal fibers. 99 This image shows the deposition of a melt of Si1 alloy. It was taken from a video recorded at 40,000 fps of the metal melt being deposited onto the rotating wheel 3 of the melt spinning apparatus 1. The rotating wheel 3 is at the bottom of the image shown in Figure 1c, and the microstructured nozzle 4 is at the top. The temperature of the melt was set to 50-300°C above the melting temperature (although a higher processing temperature may also be used). The melt forms a metal stream that wets the rotating wheel 3 and is quenched, forming metal fibers 2 from the metal stream 5.

[0084] 2a to 2d show copper metal fibers (FIG. 2a), cobalt metal fibers (FIG. 2b), and Al metal fibers (FIG. 2c) after the metal fibers 2 were produced and collected using the melt spinning apparatus 1 shown in FIGS. 1a and 1b. 99 Si1 alloy metal fiber (Fig. 2c), and Co 66 Fe4Mo2B 12 Si 16 A photographic image of alloy metal fibers (FIG. 2d) is shown. The metal fibers 2 form an entangled network of metal fibers 2. In this network, the metal fibers 2 are not attached to each other, and therefore, individual metal fibers 2 can be easily separated from the entangled network of metal fibers 2.

[0085] Figures 3a and b show the Co 66 Fe4Mo2B 12 Si 1610 shows another photographic image of alloy metal fiber 2. These photographic images show Co produced at wheel speeds of 50 m / s and 25 m / s, respectively. 66 Fe4Mo2B 12 Si 16 The images were taken from alloy metal fiber 2. The corresponding thickness and width distributions, also shown in Figures 3a and 3b, show that at the higher wheel speed of 50 m / s (see Figure 3a), the thickness and width of the resulting metal fiber 2 are reduced compared to the metal fiber 2 produced at a wheel speed of 25 m / s (see Figure 3b).

[0086] The X-ray diffraction spectra shown in Figures 4a-c were recorded using a Bruker D8 advance XRD in Bragg-Bretano mode with a cobalt source at an anode current of 30 mA and an accelerating voltage of 40 kV. The data were collected using a Bruker VANTEC-1 detector, and the measurements were performed in air. At specific angles, the copper metal fiber 2 (see Figure 4a) and Al 99 The sharp peaks 20 observed in the Si alloy metal fibers 2 (see Figure 4b) indicate that these metal fibers 2 are polycrystalline. 66 Fe4Mo2B 12 Si 16 In the alloy metal fiber 2 (see FIG. 4c), the peaks 22 are spread over a relatively wide angular range, ie, there is no such sharp peak 20, which indicates that this metal fiber 2 is amorphous.

[0087] Figures 5a and 5b show scanning electron micrographs of copper metal fibers 2. These micrographs were recorded on a Zeiss Ultra55 at an accelerating voltage of 3 kV. The scale bar in the lower left corner of Figure 5a indicates a length of 100 μm, and the scale bar in the lower left corner of Figure 5b indicates a length of 2 μm. As can be seen from the micrograph in Figure 5a, the metal fibers 2 are not fixed to each other but form an entangled network. In this network, the metal fibers 2 can move relative to each other, so that individual metal fibers 2 can be easily separated from the entangled network. Also visible from the micrograph in Figure 5a is the fact that the metal fibers 2 have a nearly constant width over a length of millimeters. In fact, although not visible in Figures 5a and 5b, the width and thickness of the copper metal fibers are nearly constant over a length of several centimeters. Figures 5c and 5d show additional scanning electron micrographs of Al metal fibers, which were prepared in a manner similar to the scanning electron micrographs in Figures 5a and 5b. 99 The scale bar in the lower left corner of Fig. 5c indicates a length of 100 μm, and the scale bar in the lower left corner of Fig. 5d indicates a length of 10 μm. 99 It can be seen that the Si1 alloy metal fibers 2 form an entangled network in which the metal fibers 2 are not fixed to each other. The thickness and width of the metal fibers 2 are also approximately constant over the millimeter length. In fact, although not visible in Figures 5c and 5d, the Al 99 The width and thickness of the Si1 alloy metal fiber 2 are almost constant over a length of several centimeters. 99 Another scanning electron micrograph of Si1 alloy metal fiber 2 is shown. The scale bar in the lower left corner of Figure 5e indicates a length of 3 μm. In the micrograph shown in Figure 5e, nanocrystalline domains are visible as granular structures. Figure 5f shows a scanning electron micrograph of gold metal fiber 2. The scale bar in the lower left corner of Figure 5f indicates a length of 10 μm. In the micrograph shown in Figure 5f, nanocrystalline domains are visible as granular structures. Figure 5g shows a scanning electron micrograph of Cu 92 A scanning electron micrograph of Sn8 alloy metal fiber 2 is shown. The scale bar in the lower left corner of Figure 5g indicates a length of 1 μm. Nanocrystalline domains can also be recognized in the micrograph shown in Figure 5g. Figure 5h shows a Cu alloy fiber fabricated by melt spinning. 96Nanocrystalline domains are also found in Si4 alloy metal fiber 2, as can be seen from the granular structure visible in the scanning electron micrograph of fiber 2. The scale bar in the lower left corner of Figure 5h indicates a length of 1 μm.

[0088] The graph in Figure 6a shows the 527 Al strips fabricated at a wheel speed of 25 m / s. 99 The thickness and width of the Si1 alloy metal fiber 2 are shown in Fig. 6b and Fig. 6c, respectively. 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, as shown by the line in Figure 6b. The width of the metal fibers ranges from 5 to 80 μm, with an average width of 39.5 μm and a median width of 35.0 μm. Figure 6d shows the results of two DSC measurements. Curve I in Figure 6d was obtained from CuSn8 ultrafine fibers immediately after melt spinning. Curve II in Figure 6d was obtained from the same ultrafine fibers after thermal equilibration. This shows the heat generation process when heating a melt-spun fiber compared to a thermally equilibrated metal fiber.

[0089] Figure 7 shows a scanning electron microscope photograph of a network 6 of metal fibers 2 according to the present invention. The scale bar in the lower left corner of Figure 7 indicates a length of 20 μm. The metal fibers 2 in the network 6 in Figure 7 are Co 66 Fe4Mo2B 12 Si 16 5a or 5c, the network 6 of metal fibers 2 shown in FIG. 7 is made up of amorphous metal fibers 2 of an alloy. In contrast to the entangled network of metal fibers 2 shown in the scanning electron micrographs of, for example, FIG. 5a or 5c, the network 6 of metal fibers 2 shown in FIG. 7 is made up of metal fibers 2 that are fixed to one another at contact points 7 where the metal fibers 2 are sintered together. As a result of the metal fibers 2 being sintered together, the metal fibers 2 are fixed to one another and cannot move relative to one another, and a single metal fiber 2 cannot be separated from the network 6 without destroying the contact points 7.

[0090] 7 to 9, it can be seen that the network 6 of metal fibers 2 according to the present invention has voids 9 as holes between the metal fibers 2. For a clear overview, only some of the metal fibers 2, contact points 7, and voids 9 are indicated by reference numerals in FIG. 7. In FIGS. 8 and 9, the reference numerals for the voids 9 and contact points 7 are omitted, and similarly, only some of the metal fibers 2 are indicated by reference numerals.

[0091] Figures 8 and 9 show the Co 66 Fe4Mo2B 12 Si 16 Photographs of another network 6 of amorphous metal fibers 2 of the alloy are shown, which show that the network 6 can be grasped with tweezers 8 without separating the metal fibers 2 from the network 6 of metal fibers 2, and that the network 6 is an irregular network 6, i.e., the metal fibers 2 have no preferred orientation and are randomly oriented.

[0092] Figures 8 and 9 show photographic images of the same network 6 of metal fibers 2. In Figure 8, the resulting network 6 after production is held with tweezers 8. From Figure 9, it can be seen that the network 6 can be bent and that the metal fibers 2 remain attached to each other and do not separate from the network 6 of metal fibers 2.

[0093] 8 and 9, it can be seen that the network 6 of metal fibers 2 has a porous structure with interconnected pores extending throughout the metal fiber network. The contact points 7 between the metal fibers 2 are randomly distributed throughout the network 6 of metal fibers 2.

[0094] Figures 10 and 11 show photographic images of a network 6 of copper metal fibers 2. The fabrication of the network 6 shown in Figure 10 is described below as Example 9. The fabrication of the network 6 shown in Figure 11 is described below as Example 10. Thus, the network 6 shown in Figure 10 was fabricated at a higher temperature compared to the network 6 shown in Figure 11. In both networks 6, pores 9 are distributed throughout the entire network 6, but the pore density, i.e., the number of pores per surface area, is lower in the center of the network 6 and increases toward the edges of the network 6 in Figure 10. For clarity, the reference numerals for the metal fibers 2, contacts 7, and pores 9 have been omitted in Figures 10 and 11.

[0095] In the network 6 shown in Figure 11, the distribution of voids 9 as pores is more uniform throughout the network 6 of metal fibers 2 compared to the distribution of voids 9 in the network 6 shown in Figure 10. It is believed that the higher processing temperature used to produce the network 6 shown in Figure 10 converted some of the metal fibers 6 into metal foil. This could be almost completely avoided by lowering the processing temperature, as confirmed in the network 6 shown in Figure 11.

[0096] Figures 12 and 13 show scanning electron micrographs of the network shown in Figure 11. These scanning electron micrographs were recorded in the same manner as the other scanning electron micrographs described above. The scale bar in the lower left corner of Figure 12 indicates a length of 200 μm, and the scale bar in the lower left corner of Figure 13 indicates a length of 100 μm. From these scanning electron micrographs, it can be seen that the structure of the copper metal fibers 2 is preserved, but that the metal fibers 2 have been sintered together at their contact points 7, so that the fibers 2 no longer form an entangled network but are instead fixed together, and therefore it is no longer easy to separate individual metal fibers 2 from the metal fiber network 6. It can also be seen that pores 9 extend throughout the metal fiber network 6, and that the contact points 7 are randomly distributed throughout the network 6. As will be discussed in the Examples, the striations visible in the scanning electron micrographs of Figures 12 and 13 result from the Thermax alloy discs used to fabricate the metal fiber network 6. These Thermax alloy discs were cut, resulting in very fine grooves (not shown) on the surface. These grooves are cut into the metal fiber network during manufacture using a hot press 10 as shown diagrammatically in FIG.

[0097] Figure 14a shows another photographic image of a network 6 of metal fibers 2 according to the present invention, in which the metal fibers are Cu 92The network 6 shown in FIG. 14a is made of a Sn8 alloy. The fabrication of the network 6 shown in FIG. 14a is described later in Example 11. In the network 6 shown in FIG. 14a, voids 9 (as holes) are distributed throughout the entire network 6. The network 6 is an irregular network 6. That is, the metal fibers 2 are randomly oriented without a preferred orientation, and the metal fibers 2 are attached to each other at contact points 7, where the metal fibers 2 are sintered to each other. For clarity, the reference numerals for the contact points 7 and voids 9 are omitted in FIG. 14a; only some of the metal fibers 2 are labeled in FIG. 14a. The metal fibers 2, contact points 7, and voids 9 can be seen in the SEM images of the network 6 shown in FIG. 14a, shown in FIGS. 14b and 14c. The scale bar in the lower left corner of FIG. 14b indicates a length of 100 μm, and the scale bar in the lower left corner of FIG. 14c indicates a length of 20 μm. The enlarged view shown in Figure 14c shows that more than two metal fibers 2 may be sintered together at a contact point 7, so that multiple metal fibers 2 may be bonded together by sintering at one contact point 7. For the sake of clarity, only some of the metal fibers 2, contact points 7, and voids 9 are labeled in Figures 14b and 14c.

[0098] FIG. 15 shows a schematic diagram of a heat press 10 that can be used to manufacture a network 6 of metal fibers 2 according to the present invention. The heat press 10 includes upper and lower members 11 that can apply force to disks 12, with the metal fibers 2 placed between the disks. The heat press allows for control of the temperature at the location of the metal fibers 2. The disks 12 may be omitted, and the metal fibers 2 may be placed directly between the upper and lower members 11. When manufacturing the network 6 of metal fibers 2 whose scanning electron micrographs are shown in FIGS. 12 and 13, the disks 12 were formed from a Thermax alloy having fine grooves (not shown) on their surfaces. The fine grooves had widths ranging from 30 to 60 μm.

[0099] 16a and 16b show schematic diagrams of a half-cell 13a according to the present invention and a prior art battery 13b, respectively. Both half-cells 13a and 13b include a current collector 14 as a first electrode. The current collector 14 is coated with an electrode active material 15. The battery includes lithium 16 as an electrolyte. The half-cells 13a and 13b include an electrolyte that impregnates all components of the batteries 13a and 13b and transports lithium ions. In the half-cell 13 shown schematically in FIG. 16a, the current collector 14 is a network 6 of metal fibers 2 according to the present invention, while in the battery 13b shown schematically in FIG. 16b, the current collector 14 is a copper foil. The construction and composition of batteries 13a and 13b will be described in more detail in the context of the examples below.

[0100] The results of capacity measurements of half-cells 13a and 13b are shown in Figure 17. Compared to a reference cell containing copper foil instead of a metal fiber network while keeping the amount and composition of active material constant in both half-cells 13a and 13b, the capacity of the cell according to the invention containing a metal fiber network is increased by about 50%.

[0101] Copper alloy Cu 96 Another electrode was fabricated using a metal fiber network composed of Si4. The network was impregnated with a dispersion consisting of 90% graphite and 10% binder, as further described below. As a reference electrode, copper foil was coated with a 50 μm layer of the same dispersion using a doctor blade. Figures 18 and 19 show graphs of the discharge profiles obtained by chronopotentiometry for an electrode of the present invention with a metal fiber network and a reference cell.

[0102] Figure 20a shows the second and final charge-discharge profiles of the reference cell obtained by chronopotentiometry in the graph of Figure 18. Figure 20b shows the second and final charge-discharge profiles of the network cell of the present invention obtained by chronopotentiometry. To better illustrate the changes in the charge-discharge profiles during cycling, Figure 21a shows graphs of current-normalized charge-discharge profiles of the network cell of the present invention and the reference cell obtained by chronopotentiometry versus time. Figures 21b and 21c show enlarged views. Figure 22 shows the evolution of capacity versus cycle number for the electrode of the present invention and the reference electrode.

[0103] Figure 23a shows the copper alloy Cu 96 Figure 23 shows an SEM image of an electrode of the present invention having a metal fiber network composed of Si4. This SEM image shows the presence of graphite flakes in the metal fiber network, i.e., between the metal fibers. Figure 23b shows an EDX mapping of copper for the electrode of the present invention shown in Figure 23a. Figure 23c shows an EDX mapping of carbon for the electrode of the present invention shown in Figure 23a. The EDX mapping shows the presence of graphite between the metal fibers. [Example]

[0104] The following experiments were carried out.

[0105] Metal fiber manufacturing Metal fibers were formed using a melt spinning apparatus with various experimental parameters. On the one hand, the apparatus consisted of a large 200 mm diameter copper alloy wheel 3 placed in an argon-filled chamber at a pressure of 300 mbar (both typical experimental setups). On the other hand, the wheel rotation speed was increased up to 60 m / s. The pressure difference between the nozzle-equipped crucible and the surrounding chamber atmosphere was increased up to 2000 mbar (or less), resulting in the ejection of molten metal or metal alloy onto the rotating wheel surface. As a result, microdroplets of the melt were formed, which were rapidly quenched and formed into fine ribbon-like metal fibers (see Figures 1a and 1b for microdroplets of different metals deposited on the rotating wheel). Details of the melt spinning apparatus used are disclosed in European Patent Application No. 19175749.1, International Publication No. WO 2016 / 020493, and International Publication No. WO 2017 / 042155.

[0106] Each single microdroplet 5 was transformed into one or more metal fibers 2. The deposition rate of the molten alloy on the rotating wheel 3 was 1.0 to 10.0 mg s -1 The deposition rate was reduced to a range of 0.01 to 0.15 or less. Using this deposition rate, a large amount of fine ribbon-like metal fibers 2 was formed, up to 90-95% of the initial mass of the molten alloy in the crucible. Optical images of the produced metal fibers 2 are shown in Figures 2a-d. After rapid quenching and recovery, the metal fibers 2 form an entangled network. In this network, the metal fibers easily slide past each other, making it easy to remove a single metal fiber from the network.

[0107] Typical initial mass of the melt ranged from 5 to 12 g (however, it may be increased to 100 g). The distance between the nozzle 5 and the wheel surface ranged from 50 to 3000 μm. Referring to FIG. 1b, Al 99The photographs shown are from a video of the deposition of a Si1 alloy melt onto a rotating wheel, filmed at 40,000 fps. The melt temperature was 50–300°C higher than the melting temperature (although a higher processing temperature may also be used). The photographs shown in Figures 2a–d and 3a and b were taken from a similarly fabricated metal fiber.

[0108] Metal fiber structure The minute ribbon-shaped metal fibers 2 are made of Co, Cu, Al, and alloys of these elements with other elements, such as Co. 66 Fe4Mo2B 12 Si 16 , Al 99 Made from Si1 (not a comprehensive list), pure Cu or alloyed Al 99 The metal fiber 2 formed with Si1 has the X-ray diffraction spectrum of Cu metal fiber 2 (Fig. 4a) and Al 99 As shown in the X-ray diffraction spectrum of Si1 alloy metal fiber 2 (Fig. 4b), it had a polycrystalline structure with a maximum crystal size of 8 μm or less. 66 Fe4Mo2B 12 Si 16 The metal fiber 2 formed from the alloy had a typical glass-metal structure. 66 Fe4Mo2B 12 Si 16 As can be seen from the X-ray diffraction spectrum of the alloy metal fiber 2, this metal fiber 2 was an amorphous metal fiber 2.

[0109] By using more complex Cu and Al alloys and adjusting experimental parameters such as wheel speed and melt temperature, metal fibers 2 composed mainly of Al or Cu can be obtained (Co alloy Co 66 Fe4Mo2B 12 Si 16 It is expected that they can be fabricated as nanocrystalline structures (as observed in ) or glassy metallic structures.

[0110] Metal fiber dimensions Co alloy Co 66 Fe4Mo2B 12 Si 16In this case, typical dimensions of the metal fibers 2 were widths of 2.0 to 25.0 μm, thicknesses of 1.0 to 7.0 μm, and lengths of 2.0 to 100.0 mm (see Figures 3a and 3b). The ribbon thickness distribution was narrowly Gaussian with a small standard deviation of 0.4 μm. That is, 68% (resp. 95%) of the metal fibers 2 had thicknesses within a narrow interval (centered around the mean thickness) of 0.8 μm (resp. 1.6 μm). At a wheel speed of 25 m / s, the mean ribbon thickness was 5.80 μm (see Figure 3b). Doubling the wheel speed reduced the mean ribbon thickness to 3.22 μm (see Figure 3a). The fiber width distribution was either Gaussian or log-normal. At a wheel speed of 25 m / s, the mean fiber width was 14.2 μm, with a median width of 13.2 μm. That is, 50% of the fibers are smaller than 13.2 μm in width. Doubling the wheel speed reduces the mean and median width to 9.4 μm, that is, 50% of the fibers are smaller than 9.4 μm in width.

[0111] Al alloy Al 99 For Si1, the mean and median thickness was 8.5 ± 0.1 μm. That is, 68% (resp. 95%) of the fibers and 2 had thicknesses between 6.6 and 10.4 μm (resp. 4.8 and 12.2 μm). The mean width was 39.5 ± 1.0 μm, and the median width was 35.0 ± 1.0 μm. That is, 50% of the fibers had widths smaller than 35.0 μm (Figures 6a-c). 99 SEM images of the Si1 alloy metal fiber 2 are shown in Figures 5c and 5d, respectively.

[0112] The dimensions of the copper metal fibers 2 were similar to (or smaller than) those of the Al alloy metal fibers. SEM images of the copper metal fibers 2 are shown in Figures 5a and 5b. These SEM images show that the width of the metal fibers 2 remains constant over lengths of at least 1 mm (this is true even for lengths greater than 1 cm). These ribbons have a crystalline structure (particles can be directly visualized by observing the top surface, which is the gas-liquid interface before solidification during rapid quenching). The maximum size of the crystals is estimated to be in the range of 5-8 μm.

[0113] Using the metal fibers 2, a network 6 of metal fibers 2 was produced.

[0114] Manufacturing of metal fiber networks Before fabricating the network 6 of metal fibers 2, the Co alloy Co 66 Fe4Mo2B 12 Si 16 It was confirmed that the crystallization temperature was 560°C and the melting temperature was 1021°C.

[0115] Example 1 Co produced by the melt spinning process described above 66 Fe4Mo2B 12 Si 16 The amorphous metal fiber 2 was placed between two 45 mm diameter aluminum oxide disks 12. The element consisting of the 45 mm diameter aluminum oxide disks 12 and the metal fiber 2 was then placed in a preheated heat press 10 at 400°C, and the fiber 2 was pressed at a predetermined pressure (377 MPa) for a predetermined time (30 minutes) to avoid thermal expansion effects due to heating.

[0116] Example 2 Network 6 of Example 2 was prepared in the same manner as Network 6 of Example 1, except that the pressure was reduced to 277 MPa. An SEM image of Network 6 of Example 2 is shown in FIG. 7. As can be seen, the metal fibers 2 are sintered together to form a stable network 6. The SEM image shows that the texture and appearance of the metal fibers 2 are preserved, except for the interface with the aluminum oxide disk 12.

[0117] Example 3 Network 6 of Example 3 was prepared in the same manner as network 6 of Example 1, except that a 60 mm diameter Thermax high temperature alloy disk 12 was used instead of the aluminum oxide disk 12. The applied pressure was 283 MPa.

[0118] Example 4 Network 6 of Example 4 was prepared in the same manner as Network 6 of Example 3, except that the time was shortened to 20 minutes.

[0119] Example 5 Network 6 of Example 5 was prepared in the same manner as Network 6 of Example 3, except that the time was shortened to 10 minutes.

[0120] Example 6 Network 6 of Example 6 was prepared in the same manner as Network 6 of Example 3, except that the time was shortened to 5 minutes.

[0121] Example 7 Network 6 of Example 7 was prepared in the same manner as Network 6 of Example 3, except that the temperature was reduced to 300°C.

[0122] Comparative Example 1 As Comparative Example 1, Co 66 Fe4Mo2B 12 Si 16 Amorphous metal fiber 2 was placed in an oven and heated to 600°C for 30 minutes without external pressure. The fibers crystallized, but did not sinter together.

[0123] Comparative Example 2 A network of Comparative Example 2 was prepared in the same manner as Network 6 of Example 1, except that the pressure was reduced to 157 MPa.

[0124] The network collapsed when removed from the heat press 10. This indicates that the metal fibers 2 were not sufficiently sintered together.

[0125] Comparative Example 3 A network of Comparative Example 3 was prepared in the same manner as Network 6 of Example 3, except that the pressure was reduced to 177 MPa.

[0126] Comparative Example 4 A network of Comparative Example 4 was prepared in the same manner as Network 6 of Example 4, except that the temperature was lowered to 100°C.

[0127] Comparative Example 5 A network of Comparative Example 5 was prepared in the same manner as Network 6 of Example 4, except that the temperature was lowered to 200°C.

[0128] Table 1 summarizes the time, pressure, and temperature used to prepare the networks of Examples 1 to 7 and Comparative Examples 1 to 5.

[0129] [Table 1]

[0130] The time and temperature for Comparative Example 2 were the same as those for Examples 1 and 2. However, the network of Comparative Example 2 collapsed upon removal from the press 10. This indicates that amorphous Co 66 Fe4Mo2B 12 Si 16 It can be seen that the pressure was insufficient to sinter the alloy metal fibers 2 and bond the metal fibers 2 together. It can be concluded that pressure is the driving force for the sintering of the metal fibers 2. Because amorphous materials are less dense than crystalline materials, when pressure is applied, atoms at the interface begin to move. This causes these atoms to transition to a state that is energetically favorable in light of the applied pressure. As a result of the atomic movement, the metal fibers 2 are permanently sintered together.

[0131] No significant difference was observed in the metal fiber networks 6 of Examples 3 to 5. In Example 6, where the time was shortened to only 5 minutes, the fibers 2 were not bonded to each other as strongly as in Examples 3 to 5. This suggests that Co 66 Fe4Mo2B 12 Si 16 It has been found that the process of bonding the metal fibers 2 of the alloy together is somewhat time dependent but is complete within a few minutes.

[0132] For example, as can be seen from Examples 4 and 7, in which the temperatures were 400°C and 300°C, respectively, the temperature at which the metal fiber 2 was applied was Co 66 Fe4Mo2B 12 Si 16It can be seen that the process of sintering the metal fibers 2 together occurs even at temperatures as low as 40% or 30%, respectively, of the melting temperature of the alloy. Comparative Examples 4 and 5 show that when the temperature is lowered to 100°C or 200°C, respectively, the atomic movement is too small to bond the metal fibers 2 together by sintering.

[0133] Example 8 Network 6 of Example 8 was produced in the same manner as Network 6 of Example 3, except that the temperature was 500°C and the time was 20 minutes. In addition, the amount of Fiber 2 used in Network 6 of Example 8 was increased to obtain Network 6 with a thickness of 0.7 mm. When subjected to a temperature of 500°C and a pressure of 283 MPa for 20 minutes, Network 6 of Example 8 was completely sintered. That is, the stability of Network 6 was equivalent to that of Example 3.

[0134] Fig. 8 shows an image of the network 6 of Example 8 before deformation, and Fig. 9 shows an image of the network 6 of Example 8 in a deformed state. Therefore, it can be seen from Fig. 9 that the metal fibers 2 do not separate from the network 6 even when the network 6 is significantly deformed. This shows that a highly stable network 6 that is resistant to damage due to deformation has been formed.

[0135] Example 9 Co 66 Fe4Mo2B 12 Si 16 Network 6 of Example 9 was produced in the same manner as network 6 of Example 3, except that the amorphous metal fibers 2 were replaced with the above-mentioned copper (Cu) polycrystalline fibers 2, the time was 5 minutes, the pressure was 177 MPa, and the temperature was 300°C.

[0136] Example 10 Network 6 of Example 10 was prepared in the same manner as Network 6 of Example 9, except that the time was changed to 5 minutes.

[0137] Comparative Example 6 Network 6 of Comparative Example 6 was produced in the same manner as the network of Example 9, except that the time was 30 minutes and the temperature was 500°C.

[0138] Table 2 summarizes the time, pressure, and temperature used to prepare the networks of Examples 9 and 10 and Comparative Example 6.

[0139] [Table 2]

[0140] In Comparative Example 6, no metal fibers were discernible in the sintered product, and the resulting product was copper foil. If a light source were placed behind the copper foil, some inhomogeneity might be discernible. The network 6 in Examples 9 and 10 had a thickness of 0.15 mm or more and 0.25 mm or less.

[0141] When producing network 6 in Example 9, the time and temperature were reduced to 5 minutes and 300°C, respectively, but the pressure was the same as that applied in Comparative Example 6. Metal fibers 2 were recognizable in the resulting product, and a porous structure, i.e., voids 9, was observed in at least some areas. As a result, when producing network 6 in Example 10, the time was further reduced to 3 minutes, while the time and pressure were maintained at the same values ​​as in Example 9. It was found that the porous structure, i.e., voids 9, was present almost uniformly throughout the sample.

[0142] Images of networks 6 of Examples 9 and 10 are shown in Figures 10 and 11, respectively. From Figure 10, it can be seen that the porosity of network 6 of Example 9 has decreased in some areas. In particular, many holes can be observed near the ends of network 6 of Example 9. As can be seen from the image of network 6 of Example 10 shown in Figure 11, the porosity increased by shortening the time from 5 minutes to 3 minutes.

[0143] SEM images of network 6 from Example 10 are shown in Figures 12 and 13. These SEM images show the porous structure of network 6 and also show that the metal fibers 2 are sintered together. The stripes seen in Figures 12 and 13 are caused by the surface of the Thermax high temperature alloy disc 12 used to press the metal fibers 2. The stripes in the Thermax high temperature alloy disc are caused by cutting the Thermax high temperature alloy.

[0144] Without being bound by theory, it is hypothesized that the improved sinterability of copper metal fibers 2 is due to the high energy storage resulting from the rapid cooling rate of the melt spinning process used to fabricate the fibers. In the melt spinning process, cooling rates can be as high as 10 6 K·min -1 Therefore, the atoms in the system are frozen before they can be arranged in an energetically favorable state. Of course, copper's intrinsic effects on atomic diffusion may also play a role.

[0145] The networks 6 of the above-described embodiments can be bent without permanently deforming them, and once bent, these networks 6 can bend into new, stable shapes.

[0146] Cu alloy 92 Another experiment was carried out using Sn8 metal fibers. 92 The SnO metal fibers were prepared in the same manner as the other metal fibers described above. The Cu alloy was dissolved in 200 mL of demineralized water containing 50 mg of SDS (sodium dodecyl sulfate). 92 The Sn8 metal fibers were dispersed, vacuum filtered, and then dried. The resulting entangled metal fiber network was homogeneously distributed but not oriented.

[0147] Example 11 Cu prepared by the melt-spinning process described above and treated with the SDS aqueous solution also described above. 92A polycrystalline metal fiber 2 of Sn8 was placed between two 60 mm diameter Thermax alloy discs 12. The element consisting of the 60 mm diameter Thermax alloy discs 12 and the metal fiber 2 was then placed in a preheated 300°C heat press 10, and the fiber 2 was pressed at a predetermined pressure (78 MPa) for a predetermined time (3 minutes) to avoid thermal expansion effects due to heating. In this way, a Cu network 6 with stability against deformation similar to that of Examples 1 to 10 was fabricated. 92 A stable network 6 of Sn8 metal fibers was obtained. The thickness of the network 6 in Example 11 was in the range of 0.15 mm to 0.25 mm. 92 A photographic image of the Sn8 metal fiber network 6 is shown in Figure 14a. 92 SEM images of the Sn8 metal fiber network are shown in Figures 14b and 14c.

[0148] Comparative Example 7 Network 6 of Comparative Example 7 was fabricated in the same manner as Network 6 of Example 11, except that the temperature was kept at room temperature, i.e., approximately 20°C. The metal fibers were not sintered together, and only poor mechanical stability was observed. This mechanical stability was due to deformation of the metal fibers under applied pressure, not due to sintering of the metal fibers.

[0149] Comparative Example 8 Network 6 of Comparative Example 8 was prepared in the same manner as Network 6 of Example 11, except that only a weak pressure of about 2 kPa was applied. The metal fibers were not bonded to each other at all.

[0150] Example 11 and Comparative Examples 7 and 8 reveal that a combination of pressure and temperature is required to sinter the metal fibers together and bond the metal fibers 2 together. Without being bound by theory, it is believed that the pressure likely causes the metal fibers 2 to adhere to each other, and mechanical deformation creates a conformal contact surface between the metal fibers 2. Increasing the temperature promotes atomic migration in the direction of the pressure, resulting in sintering of the metal fibers 2 and bonding the metal fibers 2 together.

[0151] Example 12 Making fleece by carding Carding is a mechanical process in which fibers 2 are loosened, cleaned, and mixed to produce a continuous fleece 26. A schematic of a carding machine 24 is shown in Figure 24. The continuous fleece 26 is obtained by passing the fibers 3 between clothed, differentially moving surfaces, such as rotating drums 28. A carding cloth 30 breaks up bundles or irregular clumps of fibers 2, causing the individual fibers 2 to align and become parallel to one another. Although carding is well known for wool, it has not been used to organize metal fibers 2 to form a fleece 26.

[0152] Figure 25 shows an example of a fleece after carding. Here, melt-spun brass fibers approximately 10 cm long, 30 μm wide, and 2 μm thick are disentangled in a carding machine. Two layers are formed and stacked. They may be layered between layers of cotton to form a cotton / metal hybrid fleece or fabric. Also, a combination of cotton and metal fiber netting can be disentangled in a single carding step to form a cotton / metal hybrid fleece.

[0153] Figure 25 shows photographic images of the manufacturing process according to the present invention. First, the metal fibers were disentangled in a carding machine, as shown in the top left image of Figure 25. For a better overview, reference numbers are not shown in Figure 25. Next, layers 1 and 2 of differently oriented fibers, as shown in the two center photographs in the top row of Figure 25, are stacked to obtain a two-layer fleece, as shown in the top right image of Figure 25. As an intermediate material, a cotton fleece, such as that shown in the bottom right image of Figure 25, can be integrated with the metal fibers to obtain a layered fleece. The top and bottom surfaces of the layered fleece are shown in the bottom left and bottom center images of Figure 25.

[0154] Example 13 Ultrasonic welding was performed to mechanically bond all fibers 2 of the metal network 6 or only fibers 2 at different locations. In principle, longitudinal and vertical ultrasonic welding are possible. These machines are commercially available. The preferred technique is vertical ultrasonic welding. In this case, a hammer moves up and down at high frequency. In principle, this can also be achieved by striking a suitable object against a fleece formed from the metal fibers 2. An example of a copper-based fleece is shown in Figure 26. For clarity, reference numbers are not shown in Figure 26. The left part of Figure 26 shows a photographic image of a network 6 of metal fibers 2 according to the present invention. The clearly visible square in the center of the left photographic image is the area where the metal fibers 2 are bonded to each other by ultrasonic welding, as described above. Images numbered 1 to 3 in Figure 26 are enlargements of the areas indicated by the boxes and numbers corresponding to the left photographic image in Figure 26. The image below the enlargement of number 1 is another enlargement corresponding to the box shown in the enlargement of number 1, showing that the metal fibers 2 are bonded to each other by ultrasonic welding.

[0155] Fabrication of electrodes and lithium-ion batteries The electrode of the present invention Circular disks 6 mm in diameter were cut from the network 6 of Example 10 and impregnated with a dispersion of 80% SnO, 10% carbon black, and 10% binder. In this electrode of the present invention, the network 6 of sintered copper metal fibers 2 functions as the current collector 14.

[0156] Electrodes not according to the present invention 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 the coating layer was adjusted to 50 μm using a tape casting method. This copper foil served as a current collector 14.

[0157] The materials used to prepare the dispersion were as follows: SnO: Tin(II) oxide, 99.9% by weight, purity based on impurity metals (Alfa Aesar (Art. No. 11569)) Carbon black: (Carbon Nanopowder<100nm, Sigma Aldrich, P-Code: 633100-25) Binder: Polyvinylidene fluoride (PVDF) (Alfa Aesar (Art. No. 44080))

[0158] battery As shown schematically in Figure 16a, a half-cell 13a was assembled, including electrodes 14 and 15, a separator 17, and a Li foil 16. In this half-cell 13a, the electrode of the present invention was the above-described electrode, i.e., the network 6 of Example 10 coated with an electrode active material 15.

[0159] For reference, another half-cell 13b was assembled as shown schematically in Figure 16b, in which the non-inventive electrode was the electrode described above, i.e., copper foil coated with 50 μm of the electrode active material described above.

[0160] Increasing the amount of electrode active material 15 in the reference half-cell 13b, i.e., tape-casting a layer thicker than 50 μm, reduces capacity because electrons must travel through a thicker layer of electrode active material. Using the assembly shown in 13a, we found that incorporating the electrode active material into a conductive network allowed for a 60-fold increase in the amount of electrode active material compared to the standard assembly shown in 13b. Furthermore, the use of a metal fiber network allowed for a homogeneous charge distribution throughout the electrode and a significant increase in capacity per mass unit.

[0161] A comparison of the capacities of these two half-cells 13a and 13b is shown in Figure 17. It can be seen that the capacity of half-cell 13a (according to the present invention) is increased by nearly 50% compared to the reference half-cell 13b.

[0162] Capacity measurements were performed using a Metrohm M204 electrochemical measurement system running the software NOVA Battery 1.0. Cells were assembled in a Swagelok™-type cell using lithium foil (Sigma Aldrich (99.8 wt%)) as the counter electrode, separation polymer vlieβ (Sigma Aldrich, Whatman® glass microfiber filter, grade 934-AH®) as the separator, and 1 M LiClO4 (Sigma Aldrich) dissolved in 1:1 EC / DMC (ethyl carbonate / dimethyl carbonate (ALFA AESAR)) as the electrolyte.

[0163] To measure the capacity of the half-cell, a constant current of 100 mAh / g was applied, normalized to the amount of active material used in each electrode. The potential was simultaneously measured, and the vortex points were determined as 0.0125 V (low vortex point) and 2.2 V (high vortex point). The resulting set of data points contains the potential value at any given time. Because a constant current was applied, the capacity can then be calculated by multiplying the time between the low vortex point (fully discharged) and the high vortex point (fully charged) by the applied current.

[0164] In addition to the half-cell 13a described above, another electrode was fabricated and assembled with a counter electrode, separator, and electrolyte, and analyzed as detailed below.

[0165] Copper alloy Cu 96 The fibers formed from Si4 were dispersed, vacuum filtered, and then pressed between two 60 mm diameter plates of Thermax alloy at 300 kN and 300 °C for 3 minutes. From the resulting sintered network (mechanically stable), circular disks with a diameter of 10 mm were punched and impregnated with a dispersion of 90% graphite and 10% binder. In this case, this copper alloy network served as the current collector. For reference, a copper foil was coated with a 50 μm layer of the same dispersion using a doctor blade.

[0166] The following graphite and binders were used: Graphite: powder, <20 μm, synthetic (SigmaAldrich (Art.Nr.282863)) Binder: Polyvinylidene fluoride (PVDF) (Alfa Aesar (Art. No. 44080))

[0167] Capacity measurements were performed using a Metrohm M204 electrochemical measurement system running the software NOVA Battery 1.0. Cells were assembled in a Swagelok™-type cell using lithium foil (Sigma Aldrich (99.8 wt%)) as the counter electrode, glass fiber (Sigma Aldrich, Whatman® Glass Microfiber Filter, Grade 934-AH®) as the separator, and EC:DMC (1 M LiPF6) (EC: ethylene carbonate, DMC: dimethyl carbonate) as the electrolyte.

[0168] To measure the capacity of the half-cell, a constant current of 382 mA / g was applied, normalized to the amount of active material used in each electrode. The potential was simultaneously measured, and vortex points of 0.0125 V (low vortex point) and 2.2 V (high vortex point) were determined. The resulting set of data points includes the potential value at any given time. Because a constant current was applied, the capacity can then be calculated by multiplying the time between the low vortex point (fully discharged) and the high vortex point (fully charged) by the applied current.

[0169] For the reference cell with a reference electrode, there was a 76% loss in capacity (1183 mAh / m) after 50 cycles. 2 from 289mAh / m 2 For the cell with the network electrode of the present invention, only a 9% decrease in capacity (1492 mAh / m 2 from 1381mAh / m 2(up to 50 cycles). This indicates that the network electrode of the present invention is more electrochemically stable than a conventional reference electrode, maintaining a nearly constant capacity over 50 cycles despite using the same active material. This is related to the 3D network of the electrode of the present invention, which supports effective distribution of the stress generated in the active material by expansion during ion intercalation. The expansion of the active material during lithium ion intercalation (up to 8% by volume in the case of graphite) causes a capacity loss in the reference cell over cycling.

[0170] Furthermore, these results demonstrate that the metal fiber network of the present invention used as a current collector improves electronic conductivity. The use of such a network improves electrode conductivity by shortening the electronic conduction path compared to a reference electrode where a conductivity gradient exists throughout the electrode. Thus, the electrode of the present invention was able to charge and discharge the half-cell 50 times within 6 hours, compared to the reference electrode, which could be charged 50 times in 16 hours. In addition, as mentioned above, the network electrode of the present invention was able to maintain its capacity (1492 mAh / m 2 →1381mAh / m 2 ), but not the reference electrode (1183 mAh / m 2 →289mAh / m 2 ).

[0171] Figures 18 and 19 show graphs of the charge-discharge profiles of a reference cell and a network cell of the present invention, respectively. Figures 20a and 20b show the first and last cycles of the same measurements. Figures 21a-21c show the charge-discharge profiles normalized to current versus time to better visualize changes during cycling. Figure 22 shows the capacity over the cycles.

[0172] In all calculations, the first cycle of each measurement was excluded.

[0173] Figure 23a shows a cross-sectional SEM image of a network electrode of the present invention, visualizing the graphite flakes between the copper fibers, and Figures 23b and 23c show EDX (EDAX, ZEISS Ultra 55 model, 132-10) mapping of the same area.

[0174] Metal fiber microstructure To investigate the influence of the microstructure of the metal fibers in the metal fiber network, CuSi4, Al 99 Si1, Cu 92 Sn8, Co 66 Fe4Mo2B 12 Si 16 , and FeNiB fibers were produced as described above. The alloys shown in Table 3 were pre-heat treated with the parameters also shown in Table 3 to reduce the stored defect energy but to prevent recrystallization from changing the grain structure. The amorphous / nanocrystalline fibers were further heat treated above the crystallization temperature to investigate differences in the microstructural state.

[0175] [Table 3]

[0176] A portion of the fibers in each state (before pre-heat treatment, after pre-heat treatment, and after crystallization) was melted twice under argon atmosphere using Netzsch STA 449 F3. Pre-heat treatment was also performed using Netzsch STA 449 F3 with the parameters shown in Table 3. All samples were melted at constant heating and cooling rates (10 K / min) from 30 to 1200 °C or Al. 99In the case of Si1, the sample was heated to 900°C and then cooled again to 30°C. The sample was then heated to 1200°C or 900°C, respectively. Between each melting step, or between heat treatment and melting, if applicable, the temperature was maintained at 30°C for 1 hour. The measurements were adjusted to measure only the pure energy content of the fiber by subtracting the second heating cycle from the first. The difference in area integral between the measurements with and without pre-heat treatment corresponds to the stored defect energy or crystallization energy. The stored energy is shown in Table 4 as defect energy and crystallization energy. In the case of CuSi4, the energy was not determined because the fiber transformed into a thermodynamically stable phase with a two-phase structure during the pre-heat treatment. The two-phase structure resulted in an inaccurate measurement of the stored defect energy.

[0177] [Table 4]

[0178] The results in Table 4 show that, as mentioned above, the metal fibers obtained by melt spinning have a significant amount of stored energy as defect energy and / or crystallization energy, i.e., these fibers are not in thermodynamic equilibrium. 96 Although no value for Si4 is given, it should be noted that the metal fibers of this alloy also have a significant amount of defect energy. However, when subjected to the pre-heat treatment conditions listed in Table 3, the material transitions to a thermodynamic equilibrium state, so a meaningful quantification cannot be performed. Cu 96 The total defect energy and crystallization energy of Si4 is estimated to be about 2.3 kJ / g.

[0179] The fibers were then weighed and wet-laid to the values ​​shown in Table 5 to form a uniform nonwoven structure. They were then sintered by pressure-induced low-temperature sintering as described above in Example 1, also using the parameters shown in Table 5. Prior to sintering, the electrical conductivity of the copper and aluminum alloy fiber nonwoven structure was determined by four-point and impedance measurements. These measurements were repeated after sintering. The measurements before and after sintering are shown in Table 6.

[0180] [Table 5]

[0181] [Table 6]

[0182] It is clearly seen that the conductivity of the sintered samples is many times higher than that of the unsintered samples. It is worth mentioning that the contact distance used to measure the material's conductivity was only 5 mm for the loose fibers (before sintering). Increasing this contact distance resulted in a more than 100-fold increase in resistance. This is due to the fact that unsintered fibers do not develop stable electrical conductivity between the fibers. In contrast, the conductivity of the sintered networks was almost independent of the contact distance when increasing it. This is due to the high electrical conductivity between the fibers that is achieved by sintering.

[0183] To examine the mechanical stability of the samples, strips 10 mm wide were cut from each sample and tested by tensile testing at a pulling speed of 0.01 mm / s. The results of the tensile measurements are shown in Table 7. Since all samples were formed from homogeneous fibers of the same basis weight and manufacture, the samples were standardized by selecting samples with the same number of fibers per cross section. Therefore, the fiber density of samples obtained from metal fiber networks whose fibers had been pre-heat treated as described in Table 3 was the same as that of samples obtained from metal fiber networks whose fibers had not been pre-heat treated in this way.

[0184] [Table 7]

[0185] It can be clearly seen that the heat treatment of the samples and the resulting decomposition of storage defects adversely affect the mechanical properties of the sintered network. In other words, the use of metal fibers with structures that are not in thermodynamic equilibrium improves the strength of the resulting sintered network. This is evident from the fact that Co subjected to a pre-heat treatment 66 Fe4Mo2B 12 Si 16 This is particularly evident in the pre-heat treated Co sample, in contrast to the untreated sample. 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 crystallized samples could not be sintered at all. These samples were annealed before the sintering process. These samples collapsed into fine fibrous particles during pressing and did not achieve any mechanical cohesion.

[0186] We can summarize that only fibers produced by melt spinning can be mechanically strongly bonded to each other during pressure-induced low-temperature sintering, provided the samples are not annealed prior to sintering. The results presented here demonstrate how the defect energy introduced by the fabrication process significantly influences the degree of sintering and, therefore, the mechanical and electrical properties of the 3D mesh. To use the 3D net as a current collector, it is essential that the fibers are strongly connected to each other, ensuring consistent conductivity throughout the battery electrode. Nevertheless, the structure of the fibers must be maintained during sintering; i.e., they must not be pressed into a metal foil with no open pores.

[0187] The invention will now be further described with respect to a method for manufacturing a battery. The battery manufacturing process comprises seven process steps. 1. Manufacture metal fibers (step 1 in Figure 27). 2. The fiber net is carded to laminate the fiber fleece (step 2 b1 in FIG. 27), or the fibers are deposited by dispersion or airflow (step 2 b2 in FIG. 27). 3. The metal fibers are sintered to form a metal fiber net electrode (step 3 in Figure 27). This can be done by hot pressing (c1, c2), ultrasonic welding (c3), or hammering (c4). 4. The metal fiber net is loaded with electrode active materials to form the anode and cathode (step 4 in FIG. 27). 5. The electrode is subjected to calendar processing (step 5 in Figure 27). 6. Conductive wires are ultrasonically welded to the electrodes as connectors (step 6 in Figure 27). 7. Assemble the battery (step 7 in Figure 27).

[0188] A schematic representation of these process steps is shown in Figure 27. In the figure, step 1 shows the production of metal fibers, step 2 shows the arrangement of a fiber net into a layer fiber fleece, and step 3 shows various methods of sintering metal fibers to form a mechanically stable metal fiber network. Sintering can be performed by pressure-induced low-temperature sintering (part c1), thermal sintering (part c2), ultrasonic welding (part c3), or hammering (part c4). In part d, the metal fiber network is loaded with active material to form the anode and cathode (step 4). In part e, these electrodes are densified by calendaring (step 5). Next, in step 6, a conductive foil is attached to the metal fiber network. The battery assembly is shown in step 7 of Figure 27. These process steps are also described below.

[0189] Process 1: Manufacturing metal fibers Metal fibers are produced by melt spinning. Two major melt spinning techniques can be used to produce metal fibers: a) vertical melt spinning and b) horizontal melt spinning. Vertical melt spinning has technical limitations that result in a more expensive product and lower efficiency than horizontal melt spinning. Therefore, horizontal melt spinning is preferred in the present invention.

[0190] Step 2: Laminating fiber fleece The metal fibers are processed in a manner similar to cotton for textiles (hence the name metal fabric). First, the metallic "wool" is disentangled and the fibers are aligned by carding, as shown diagrammatically in Figure 24. This process requires very long, ultra-fine fibers. Using melt spinning as described herein, fibers several centimeters long can be produced. In this case, the substantial fiber length makes a dispersion step impossible or unnecessary. This process produces a three-dimensional fiber net that is subsequently processed. In step 2b1, the fibers are carded with a carding comb to obtain a uniform fiber network structure, and these regular layers are stacked, as is well known in the cotton processing art. To achieve this, it is preferable that the fibers be 5 to 18 cm long and that there be no connections between the fibers before carding. In this process, a dispersion step is not necessary. Dispersion can be avoided due to the long, elongated fibers.

[0191] Alternatively, an irregular fiber net is produced by deposition from a dispersion or air stream (step 2 b2).

[0192] Step 3: Sintering of the metal fibers to form a 3D metal fiber net As shown schematically in step 3c2 of Figure 27, a uniform fiber network structure can be sintered between two heating plates (the distance can be adjusted from 0.2 to 1 mm, here 0.5 mm; Al 99 Si1 at 650°C for 1.5 hours; Cu 96 Si4 at 950°C for 2 hours).

[0193] This creates a strong mechanical connection between the fibers at their crossing points. Once the metal fibers are mechanically connected and sintered, their electrical conductivity increases significantly.

[0194] Alternatively, the 3D metal fiber net can be pressure-sintered between two heated plates. To do this, the fibers are placed between two polished heated plates and sintered using a preheated uniaxial press at a pressure of 10 GPa with Al as shown in Figure 27, step 3, c1. 99150℃ for Si1, Cu 96 In the case of Si4, the material is pressed at 300 °C for 1 minute, after which the mechanically stable 3D fiber network can be easily peeled off from the substrate.

[0195] Alternatively, the metal fibers are locally fixed by ultrasonic welding (c3 in step 3 of FIG. 27) or hammering (c4 in step 3 of FIG. 27).

[0196] Step 4: Formation of anode and cathode by loading electrode active materials onto the 3D metal fiber net The active materials used in the examples are commercially available as slurries from Custom Cells. Graphite was used on the anode side and NMC_111 was used on the cathode side.

[0197] The active material slurry was then loaded onto the 3D metal fiber net using a standard doctor blade method (by doctor blade; Rakelprozess) as shown in step 4(d) of Figure 27. A siliconized PMMA foil was placed on a plate previously wetted with ethanol / acetone. After flattening the foil, the sintered fiber network was placed on the foil. The highly fluid active material slurry was then drop-cast onto the 3D metal fiber net. The capillary forces exerted by the 3D metal fiber net structure wicked the slurry into the network, uniformly coating it. A more viscous slurry was then poured onto the network, and the remaining slurry was removed using a gap doctor blade (height: 0.650 mm). The samples were then dried (anode at room temperature, cathode at 30°C).

[0198] The 3D metal fiber network was formed without contact with the active material, i.e., the active material was applied onto the metal fiber network after sintering was complete.

[0199] Electrode stacking / post-processing Step 5: Calendaring the electrodes After the electrodes were dried, they were laminated using a weight-limited calendering method with a gap of 0.2 mm and a weight of 40 kg per roller. Further experiments were performed with the following parameters: Gap: 0.4mm, 40kg No gaps, 40kg No gap, 120kg No gap, 112kg, 160℃

[0200] A schematic representation of such a calendar method is shown in step 5e of FIG.

[0201] Step 6: Ultrasonic welding of the conductive foil to the electrode Finally, Ni foils were ultrasonically welded to the sides of the electrodes. These Ni foils were the contact electrodes of the battery. The ultrasonic welding of the contact electrodes to the network 6 is shown schematically in step 6f of Figure 27.

[0202] Step 7: Assembling the battery Packaging of the 3D metal fiber network began with punching the active material-loaded electrode to the desired dimensions and shape. The sample was placed in a uniaxial press and punched to the desired shape. The sample was then attached to each side of a pre-punched separator (stretched PP / PE) with a 1-2 mm overlap to avoid internal shorting of the electrode, using a PVDF binder in acetone. These were then placed in a laminating pouch and dried in an oven at 110 °C for 48 hours. After 48 hours, the sample was transferred to a glove box, filled with electrolyte (EC / DMC, 1M LIPF6), and sealed to ensure airtight packaging. After wetting the sample for 3 hours, excess electrolyte was removed using a syringe and a vacuum pump with a liquid filter, and the pouch was resealed directly beneath the electrode.

[0203] result: The cells according to the invention obtained by the process described above were compared with comparative cells containing a flat foil as current collector instead of a metal fiber network, and the results are shown in Tables 8 and 9 below.

[0204] [Table 8]

[0205] [Table 9]

[0206] In Tables 8 and 9 above, the C-rates used to determine the gravimetric capacity and energy density and the volumetric capacity and energy density values ​​are shown as 0.1C, 0.5C, and 1C, respectively. [Explanation of symbols]

[0207] 1. Melt spinning equipment 2. Metallic Fibers 3 Spinning Wheels 4 Microstructured nozzle 5 droplets 6 Network 7. Contacts 8 tweezers 9 void 10 Heat press 11 Upper and lower members 12 discs 13a battery 13b Prior art batteries 14 Current collector 15 Electrode active material 16 Lithium 17 Separator 20 Sharp Peak 22 Peak 24 Carding machine 26 Fleece 28 Rotating Drum 30 Carded Cloth

Claims

1. A network (6) of metal fibers (2), It comprises a plurality of metal fibers (2) fixed to each other, The plurality of metal fibers (2) 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 metal fibers (2) before and / or after being fixed to each other exhibit an exothermic phenomenon when heated in a DSC measurement, The amount of energy released in the exothermic phenomenon is 0.1 kJ / g or more.

2. 2. The network (6) according to claim 1, wherein the amount of energy released in the exothermic event is equal to or greater than 0.5 kJ / g.

3. 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 any one of claims 1 to 3, wherein at least some of the metal fibers (2) of the plurality of metal fibers (2) are amorphous, or at least some of the metal fibers (2) of the plurality of metal fibers (2) are nanocrystalline.

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

6. The network (6) according to any one of claims 1 to 5, wherein each of the metal fibers (2) is in contact with one or more of the other metal fibers (2).

7. The network (6) according to any one of claims 1 to 6, wherein said network (6) is an irregular or regular network (6).

8. The network (6) according to any one of claims 1 to 7, wherein the network (6) has open holes between the metal fibers (2) of the plurality of metal fibers (2).

9. The network (6) according to any one of claims 1 to 8, wherein at least some of the metal fibers (2) of the plurality of metal fibers (2) are at least partially coated.

10. A network (6) according to any one of the preceding claims, wherein the contact points (7) between the metal fibres are randomly or regularly distributed throughout the three-dimensional structure of said network (6).

11. A method for producing a network (6) of metal fibers (2), comprising: Step 1: producing 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 by melt spinning; Step 2 of obtaining a loose network of metal fibers (2) produced in step 1; Step 3 of fixing the plurality of metal fibers to each other by any one of the following processes c1 to c4; A method comprising: c1: The plurality of metal fibers are placed in a heat press (10), and the plurality of metal fibers (2) in the heat press (10) are subjected to a predetermined pressure and temperature for a predetermined time, thereby sintering the plurality of metal fibers (2) to each other and forming contact points (7) between the metal fibers (2), thereby producing the network (6). In process c1, the pressure is 0 to 20 GPa, and the temperature is 10 to 80% of the melting temperature of the material of the metal fibers (2), which is determined by DSC measurement. c2: The loose network of metal fibers (2) is placed between two heating plates, the distance between the two heating plates is adjusted to 0.1-1 mm, and the heating plates are heated to a temperature that is 10-80% of the melting temperature of the material of the metal fibers (2), which is determined by DSC measurement. c3: Ultrasonic welding. c4: Hammering.

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

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

14. The method according to any one of claims 11 to 13, further comprising a step 4 of coating said metal fibers (2).

15. An electrode comprising a network (6) according to any one of claims 1 to 10.

16. A cell, half-cell (13a) or a plurality of half-cells separated by a membrane, comprising an electrode according to claim 15.

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