WO2024038180A1

WO2024038180A1 - Conductive conduit

Info

Publication number: WO2024038180A1
Application number: PCT/EP2023/072792
Authority: WO
Inventors: Dmitry YARMOLICH
Original assignee: Meta Materials Inc.
Priority date: 2022-08-18
Filing date: 2023-08-18
Publication date: 2024-02-22
Also published as: WO2024038184A1

Abstract

Provided are a conductive conduit and methods of manufacturing the same, as well as devices comprising such conduits.

Description

CONDUCTIVE CONDUIT

FIELD OF THE INVENTION

[001] The present invention is in the field of electronics, and more specifically, of composite materials such as conductive conduits and devices containing the same, such as current collector components of batteries, fuses, and cables, such as signal or current-carrying cables.

BACKGROUND OF THE INVENTION

[002] Conductive materials are found in a significant portion of modem products, from consumer electronics to electric vehicles and aerospace applications. There is therefore an ongoing desire for strong and lightweight conductive materials with application dependent properties.

[003] Current collectors are a fundamental component of every battery product available on the market, from mobile phones to electric vehicles. Applications are driven by the automotive sector and increased EV adoption among the general population, grid storage of electricity, avionics, train, marine and other transport electrification.

[004] Commercially available current collectors are made of thin foils of copper metal that is either rolled at high pressure into shape or deposited using electrochemical methods. The main issue with traditional manufacturing techniques is the minimum thickness of copper that can be used reliably as a mechanical substrate in subsequent production steps. Currently, standard foil thicknesses between 10 pm and 120 pm are used. From an electrical conductivity point of view, even 10 pm of copper is more than what might be used to make a functional battery. Hundreds of nanometres of copper are enough for electrical conduction purposes.

[005] Copper metal is considered an abundant and easily recyclable material. However, the production of thin copper foils is an energy intensive process that uses prolonged steps at high temperature (greater than 750 °C) and high pressure to create a substrate with the desired properties.

[006] Copper and aluminium foils used in battery manufacturing are ubiquitous to all chemistries and battery types including upcoming solid-state batteries. However, commercially available battery technologies suffer from well-known trade-offs between power density, energy density, cost, safety and scalability. Recent improvements in high performance Li-ion batteries, together with a steady decrease in cell prices, enabled the recent growth of new electric vehicle battery solutions for the automotive sector. However, there are still significant technical challenges that are hindering substantial market penetration into electric vehicle and other applications like local energy storage, electric vertical take-off and landing (eVTOL) and more. These can be summarized as improving the energy and power densities of Li-Ion batteries at scale and without additional costs (has proven to be challenging for manufacturers); and as more energy is stored into smaller form factors, the inherent safety of a cell becomes paramount. The cost of "add-on" safety solutions like more sophisticated battery management systems, higher performance materials or even pack insurance negatively affects the potential for continued growth.

[007] The bill of materials of modem Li-ion packs represents the largest portion of the manufacturing cost. Rare or environmentally damaging materials such as chromium, nickel and magnesium are driving the total materials cost. Technological solutions that utilize less material, or replace expensive ones with cheaper, more environmentally friendly alternatives are of great interest to the market. Thus, a current collector that is lighter, safer, and more sustainable than the presently available current collectors, and methods of their manufacture which are scalable, are desirable.

[008] Similar considerations apply to next generation fuses and cables, which are generally made from similar materials such as copper. Thus, lighter, safer, and more sustainable iterations of these technologies are also desirable.

SUMMARY OF THE INVENTION

[009] It has been discovered that the conductive conduits of the present disclosure address the above issues, and that their composite nature allows properties like strength, conductivity, weight, frequency response and more to be controlled at least to some extent independently. This allows the properties to be tuned for each application. This discovery has been exploited to develop the present disclosure, which, in part, is directed to a method of producing conductive conduits, and equipment containing the same, on a scalable level. In addition, when used as a current collector in batteries, the conduit addresses additional problems. It has also been discovered that current collectors made of plastic with much less copper foil can be made via vacuum roll-to- roll deposition systems.

[010] In one aspect, a conductive conduit comprises: a polymer layer; a conductive layer on the polymer layer; and a plurality of conductive paths in the polymer layer, each conductive path extending from the conductive layer to an opposite side of the polymer layer, and each conductive path comprising a convex end portion at one end, the convex end portion extending beyond and radially along the polymer layer.

[OH] In an example, each of the conductive paths comprises a concave end portion at the other end of each conductive path. Alternatively, each of the conductive paths may comprise a convex end portion at the other end of each conductive path extending beyond and radially along the polymer layer. The conductive layer may be on a first face of the polymer layer and the conductive conduit comprises a further conductive layer on a second face of the polymer layer opposite the first face. The conductive paths may be irregularly distributed in the polymer layer. A thickness of each end portion may be greater than a thickness of the conductive layer. Each end may have a concave portion between the polymer layer and the conductive layer. Each conductive path may comprise an intermediate portion in the polymer layer connected to its convex end portion, and the convex end portion may extend laterally beyond the intermediate portion within the polymer layer. Each conductive path may extend radially towards its convex end portion within the polymer layer. The plurality of conductive paths may be homogeneous.

[012] In other aspects, a current collector for a battery, a fuse or a cable comprises the conductive conduit disclosed above.

[013] In another aspect, a method of manufacturing a conductive conduit comprises providing a polymer layer and depositing a plurality of metal droplets onto the polymer layer, wherein a temperature of the plurality of metal droplets is greater than a melting point of the polymer layer. The method may comprise depositing the plurality of metal droplets onto the polymer layer using virtual cathode deposition. The method may comprise depositing one or more conductive surface layers onto the polymer layer. Depositing one of the one or more conductive surface layers onto the polymer layer may be performed at the same time as depositing metal droplets onto the polymer layer. Depositing a plurality of metal droplets onto the polymer layer may comprise vaporizing a metal target and/or may be performed under vacuum.

[014] In an example, a ratio of the diameter D of the metal droplets to the thickness h of the polymer layer is such that D is about 0.3A to about 20A, D is about Q.5h to about 10/? or D is about 0.8A to about 5h. In another example, the polymer layer has a tensile strength of at least 150 N/m² and the conductive surface layer is a metal layer with a thickness of 0.5 pm or less.

[015] In another aspect, a virtual cathode deposition system comprises a virtual cathode deposition system, comprising a target; a substrate opposite the target; and a plasma source configured to generate a plasma in an area adjacent the target, a clearance between walls of the plasma source increasing in the direction of the substrate from the target. The walls of the plasma source may be walls of a hollow electrode and the plasma source may be ring-shaped. The walls may be walls of an inner portion of the plasma source.

DESCRIPTION OF THE DRAWINGS

[016] The foregoing and other objects of the present disclosure, the various features thereof, as well as the disclosure itself may be more fully understood from the following description, when read together with the accompanying drawings in which:

[017] FIG. l is a diagrammatic representation showing a top-down view of a conductive conduit;

[018] FIG. 2 is diagrammatic representation showing a side view of a conductive conduit with a single conductive surface layer;

[019] FIG. 3 is a diagrammatic representation showing a side view of a conductive conduit with two conductive surface layers;

[020] FIG. 4 is a diagrammatic representation showing a side view of a conductive conduit with increased surface area;

[021] FIG. 5A is a diagrammatic representation showing a battery comprising conductive conduit current collectors;

[022] FIG. 5B is a diagrammatic representation of a process for tab welding a conductive conduit current collector to a single tab;

[023] FIG. 5C is a diagrammatic representation of a process for tab welding a conductive conduit current collector to two tabs;

[024] FIG. 6 is a diagrammatic representation showing a multi-layer high-voltage battery cell comprising conductive conduit current collectors;

[025] FIG. 7A is a diagrammatic representation showing a cross section of a conductive conduit cable;

[026] FIG. 7B is a diagrammatic representation showing a top view of a conductive conduit cable according to the disclosure; [027] FIG. 8 is a diagrammatic representation showing a cross-section of an exemplary cable comprising multiple conductive conduit sub-cables, according to the disclosure;

[028] FIG. 9A is a photographic representation showing a conductive composite fuse before fusing;

[029] FIG. 9B is a photographic representation showing a conductive composite fuse after fusing;

[030] FIG. 10A is a diagrammatic representation showing the mechanism of tap fusing in an exemplary conductive composite fuse according to the disclosure;

[031] FIG. 10B is a diagrammatic representation showing the mechanism of nail fusing in an exemplary conductive composite fuse according to the disclosure;

[032] FIG. 11 A is a photographic representation showing a conductive conduit fuse after nail fusing;

[033] FIG. 1 IB is a representation of a heat map of an exemplary conductive conduit fuse according to the disclosure before nail fusing;

[034] FIG. 12 is a flow diagram showing an exemplary method of manufacturing a conductive conduit according to the disclosure;

[035] FIG. 13 A is a diagrammatic representation showing the operation of an exemplary VCD system;

[036] FIG. 13B is a diagrammatic representation showing the operation of an exemplary VCD system;

[037] FIG. 13C is a diagrammatic representation showing the operation of an exemplary VCD system;

[038] FIG. 13D is a diagrammatic representation showing the operation of an exemplary VCD system;

[039] FIG. 13E is a diagrammatic representation showing the operation of an exemplary VCD system;

[040] FIG. 13F is a diagrammatic representation showing the operation of an exemplary VCD system;

[041] FIG. 13G is a diagrammatic representation showing the operation of an exemplary VCD system; [042] FIG. 13H is a diagrammatic representation showing the operation of an exemplary VCD system;

[043] FIG. 14A is a photographic representation showing a single impact site of a metal droplet on the top side of a polymer film;

[044] FIG. 14B is a photographic representation showing a single impact site of a metal droplet on the underside of a polymer film;

[045] FIG. 15A is a photographic representation showing micro-droplet flux generation with a low VCD pulse energy;

[046] FIG. 15B is a photographic representation showing micro-droplet flux generation with a medium VCD pulse energy; and

[047] FIG. 15C is a photographic representation showing micro-droplet flux generation with a high VCD pulse energy.

DESCRIPTION

[048] The disclosures of these patents, patent applications, and publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described and claimed herein. The instant disclosure will govern in the instance that there is any inconsistency between the patents, patent applications, and publications and this disclosure.

[049] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The initial definition provided for a group or term herein applies to that group or term throughout the present specification individually or as part of another group, unless otherwise indicated.

[050] For the purposes of explaining the invention, well-known features of conductive conduit, battery, fuse, and cable technology known to those skilled in the art of production of these products have been omitted or simplified in order not to obscure the basic principles of the invention. Parts of the description will be presented using terminology commonly employed by those skilled in the art of composite material design. It should also be noted that in the following description of the invention repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment.

[051] As used herein, the articles “a” and “an” refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. Furthermore, use of the term “including” as well as other forms, such as “include,” “includes,” and “included,” is not limiting. Use of the term “comprising” as well as other forms, such as “comprise,” “comprises,” and “comprised,” is not limiting.

[052] As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term “about” is meant to encompass variations of ±20% or ±10%, including ±5%, ±1%, and ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods. The term “about” also encompasses the specified value(s) exactly.

[053] As used herein, the concave end portions may be referred to as craters or depressions in the polymer layer and may extend laterally along the polymer layer. The term “lateral” may be defined as perpendicular to the direction between the end portions/opposing conductive surface layers. As used herein in respect of the plurality of conductive paths, the term “homogeneous” may mean that the conductive paths are made of a single material throughout.

[054] The present disclosure provides conductive conduits and methods of producing the same. It also provides equipment that can contain such conductive conduits, including current collectors, fuses, and cables. Such equipment containing such conductive conduits is a lighter, safer and more sustainable compared to conventional presently available examples using metallic foils. The production of such conduits may utilize a roll-to-roll line, followed by the preparation of medium sized rolls, ready to be deployed into standard industrial production and testing lines for batteries, current collectors, cables, and fuses.

[055] In one aspect, the present disclosure is directed to a conductive conduit. The conductive conduit comprises: a polymer layer; a conductive layer on the polymer layer; and a plurality of conductive paths in the polymer layer, each conductive path extending from the conductive layer to an opposite side of the polymer layer. The conductive layer provides the conductive conduit with lateral or in-plane conductivity while the conductive channels provide the conductive conduit with vertical or through-plane conductivity. A further conductive layer may be provided on an opposite face of the polymer layer, providing the conduit with two conductive surfaces that are electrically connected by the conductive paths.

[056] Each conductive path may comprise an end portion at one end. Each conductive path may further comprise another end portion at its other end and an intermediate portion extending between the end portions. One or more of the end portions may be a convex end portion extending beyond and radially along the polymer layer and/or a concave end portion. The convex end portions may be on the polymer layer. The convex end portions may be referred to as bulbs or bumps and are on the surface of the polymer layer or conductive layer. The concave end portions may be on the polymer layer. In general, the end portions may extend laterally on the face of the polymer layer and/or extend away from the face of the polymer layer, and may do so in the region in which they extend laterally. That is to say that the end portions may extend diagonally or radially away from the face of the polymer layer. The end portions provide contact zones between the conductive paths (also known as conductive channels or conductive vias) and the conductive surface layers (which may be coated metal layers). The end portions increase the volume and size of conductive material at the junction between the conductive surface layer and the conductive channels. The end portions can extend out of the polymer layer and/or conductive layer in the direction of the polymer film or out of the polymer film or in both directions. The end portions also provide increased contact area for improved adhesion of the conductive paths, polymer layer and conductive layers, and lower the contact resistance. The plurality of conductive paths may be homogeneous.

[057] The conductive paths (and therefore the end portions) may be irregularly or randomly distributed in or on the polymer layer. This avoids potential fault lines due to regular arrangement of holes weakening the conduit by removing materials along a defined line. A thickness of each end portion may be greater than the thickness of the adjacent conductive layer and/or greater than a diameter of the conductive channels. The thickness of each end portion may be defined as the largest dimension of the end portion or the largest dimension of the end portion outside of the polymer layer. The conductive layer thickness may be an average, mean, minimum or maximum thickness. Each end portion may be between the polymer layer and the conductive layer. The respective conductive layer may be on or directly on the end portions. Each conductive path may comprise an intermediate portion in the polymer layer connected to its end portion, wherein the end portion extends laterally beyond the intermediate portion within the polymer layer and/or each conductive path may extend radially towards its convex end portion within the polymer layer, and may do so at both ends with respect to the intermediate portion. Thus, the conductive channels may have a funnel or frustoconical shape. This can reduce contact resistance and/or increase contact area with the conductive layer. Each conductive path may be in a channel in the polymer layer, wherein each channel is completely filled with its respective conductive path. The conductive paths may have a cylindrical or substantially cylindrical cross section. This provides increased conductivity and structural integrity for a given channel size. A melting point of the conductive paths may be higher than a melting point of the polymer layer.

[058] The polymer layer(s) may be sheets or films. They may comprise or consist of polyethylene terephthalate ‘PET’/’PETE’, polyethylene naphthalate ‘PEN’, high-density polyethylene ‘HDPE’, polyvinyl chloride ‘PVC’, low-density polyethylene ‘LDPE’, polypropylene ‘PP’, polystyrene or Styrofoam ‘PS’, polytetrafluoroethylene ‘PTFE’ or polyimide such as Kapton, or combination of them in a layered structure or alloying them. The polymer layer may have a thickness of at least about 1 pm, at least about 5 pm, at least about 10 pm, at least about 50 pm, less than about 250 pm, less than about 100 pm, or less than about 50 pm. Controlling the polymer substrate mechanical properties (by using different polymers and thicknesses) enables control of mechanical properties of the conductive conduit. Choosing a polymer having certain dielectric properties (by using a polymer with specific impedance, resistance, frequency dependent losses, etc.) enables control of high-frequency signal propagation along and through the conduit.

[059] The thickness of the polymer material layer and the polymer material maximal tensile strength and elongation to break (ETB) (or elongation to fracture) impact the conductive conduit maximal tensile strength and ETB. The metal layer also contributes to the tensile strength and elongation coefficient of the conductive conduit, however, the percent elongation at fracture of metals is usually lower than that of polymers. However, a thin metal layer deposited on a polymer substrate with good adhesion between the layers has a higher ETB than that of bulk metal, as discussed in, for example, Metal films on polymer substrates stretched beyond 50%, APPLIED PHYSICS LETTERS 91, 221909, 2007). Hence in order to increase the elongation to break of the conductive conduit the metal layer may be chosen to be as thin as possible (less than about 1000 nm, less than about 500 nm, less than about 250 nm, or less than about 50 nm) while the polymer layer may be as thick as possible and have a high tensile strength and ETB. For example, a battery cell active material coating may require the conductive conduit to have a tensile strength of 150N/mm², hence a PET or PEN film of, for example, 6 pm (tensile strength of about 150 N/mm²) can be used as a polymer layer and a metal layer of less than about 500 nm of copper enables the conductive conduit to exceed a tensile strength of about 150 N/mm² and have a percent elongation at fracture above about 5%, or above 10% , or above 20% (bulk copper has a percent elongation at fracture of about 2.5%).

[060] The conductive layer(s) may be made of any conductive material known to the skilled person, such as, but not limited to, copper, aluminum, iron, silver, precious metals such as gold and platinum, or any other suitable metal. The conductive layer(s) may be vapor deposited metal. Controlling the deposited thickness of the metal layer and metal type enables control of the lateral and overall conductivity of the conduit.

[061] The conductive channels may be made of any conductive material known to the skilled person, such as but not limited to, copper, aluminum, iron, silver, precious metals such as, but not limited to, gold and platinum. The diameter of the conductive channels may be at least about 10 nm, at least about 100 nm, or at least about 500 nm, and/or less than about 1 pm, less than about 10 pm, less than about 100 pm, or less than about 500 pm.

[062] The conductive paths may be homogeneous, consisting of the same material throughout. The conductive paths may be made of the same material as the coating layers on the polymer substrate. However, the materials of the conductive paths and each of conductive layer coatings can be different.

[063] The density of conductive paths in the polymer layer may be at least about 10%m², at least about 10²/cm², or at least about 10⁴/cm², and/or less than about 10¹⁰/cm², less than about 10⁸/cm², or less than about 10⁶/cm². Controlling the conductive path density and conductivity (by variation of manufacturing method and conductive material type) enables control of conductive conduit through-plane conductivity.

[064] The polymer layer and/or conductive layer may have an irregular surface between the end portions. The polymer layer and/or conductive layer may be patterned or have a surface texture which increases the surface area of the conduit. The pattern may be an undulating pattern. All of these features improve adhesion and increase contact area between the conduit and any material deposited on the conduit, such as an active layer of a battery.

[065] The above features can be applied to any of the methods/systems/devices defined herein.

[066] A top view of a conductive conduit 100 is depicted in FIG. 1. A side view of the same conduit 100 is shown in FIG. 2. The conductive conduit 100 comprises a polymer layer 101, a conductive surface layer 103 made of copper and conductive paths 105 extending through the polymer layer 101 and also made of copper. However, the conductive surface layer 103 and polymer layer 101 are not limited to copper. The polymer layer 101 is made of PET but not limited to this material. The conductive paths 105 comprise a convex end portion 107 extending radially on a face of the polymer layer 101. The conductive paths 105 can have different forms and shapes, e.g., but not limited to, having inclination with respect to polymer layer. The convex end portions are bulbs that protrude from the surface of the conductive conduit 100 and mechanically and electrically connect to the conductive layer 103. The conductive conduit 100 also may comprise a concave end portion 109 at the other end of one of the conductive paths 105.

[067] A side view of a conductive conduit 100 as illustrated in FIGS. 1 and 2 comprising a further conductive surface layer 111 on the opposite side of the polymer layer 101 is depicted in FIG. 3. The further conductive surface layer I l l is made of copper but not limited to this and may be a different material to the conductive surface layer 103 and conductive paths 105. Conductive surface layers on each side of the polymer layer can be made of different materials. In one nonlimiting example, one side can be aluminum and other side can be copper. Also, any of the conductive layers or the polymer layer may comprise multiple layers of different materials. In a nonlimiting example, conductive layer 111 can comprise 150 nm thick copper and 10 nm of aluminum or other material or materials in different combinations. The combination of materials can be used for altering a surface property (e.g., but not limited to, wettability, adhesion, or other functionality).

[068] Through plane conductivity between two conductive layers means that the thickness of the conductive layers can be reduced while retaining the same overall conductivity of the conduit due to the non-linearity of conductivity dependence on thickness. For example, a 50 nm copper layer has a resistivity of about 3 pQ-cm. Hence, two parallel layers of about 50 nm thick copper have a resistivity of about 1.5 pQ-cm. However, a copper layer of about 100 nm has a resistivity of about 2 pQ-cm. Thus, the conductive conduit reduces the amount of copper used to achieve a specific conductivity. [069] The polymer layer 101 exemplified in FIGS. 1, 2, and 3 is about 6 pm thick, but it is not limited to this thickness. The exemplified conductive layers 103, 111 are each about 150 nm thick but are not limited to this thickness. The exemplified conductive channels 105 have an average diameter of about 1000 nm but are not limited to this diameter. The exemplified end portions 107, 109 have a diameter of about 10 pm and a height of about 2 pm but are not limited to these dimensions. The polymer layer 101 may consist of several layers of different materials in different combinations. For example, it can consist of 2 pm of PET combined with 2 pm of polypropylene on both sides of the PET for chemical protection and adhesion improvement.

[070] A side view of a conductive conduit 100 with increased surface area is depicted in FIG. 4. The surface of the polymer layer 101 (and hence the surface of the conductive layers 103, 111) has an undulating pattern. The conductive channels 105, polymer layer 101 and conductive layers 103, 111 are otherwise the same as in the conductive conduits 100 in FIG 3. The increased surface area improves the adhesion and increases the contact area between the conduit and a material on the surface of the conduit, such as the active material in a battery cell if the conduit is used as a current collector. Many methods of increasing the surface area of a polymer layer are known to the skilled person, such as using a mold roller on the surface to add texturing.

[071] In other aspects, the present disclosure is directed to a current collector, a fuse, or a cable each comprising a conductive conduit. Choosing the polymer layer material melting temperature, conductive layer thickness and geometrical factors defines the maximum current that a current collector, a fuse, or a cable conduct before the polymer layer will melt and trip off the current.

[072] The cable may comprise an insulating layer encompassing the conductive conduit. The cable may comprise multiple conductive conduits. The cable may comprise multiple conductive conduits that are electrically isolated from each other within the cable.

[073] Through-plane conductivity of the conductive conduit enables a multi-layer battery without compromising safety. If adjacent stacks in the battery have an unequal amount of active material, the current on both sides of the current collector becomes uneven which can lead to high current areas inside the battery cell stack in the case of no through-plane conductivity.

[074] Li-ion battery current collectors are usually metal foil of about 6 pm to about 20 pm thick made of copper for the anode and aluminum for the cathode (material choice is defined by electrochemical stability of the materials during the cycling). The current collector is a passive part of the battery and does not contribute to the storage of energy/charge. It has two functions: one being the support for the active material which is deposited on one or both sides of the current collector. For this functionality it is mechanically and thermally stable enough to be processed roll-to-roll. Another function of the current collector is the conducting of the current from the active material to the battery current outlet during charge or discharge. The charge stored in the active material is usually in the range of about 1 mAh/cm² to about 4 mAh/cm² of the current collector area, and the current density at about IO C charge/discharge rate is in the range of about 10 mA/cm² to about 40 mA/cm².

[075] The copper foil as the anode current collector provides mechanical support for the active material which usually has a thickness of about at least 5 pm, while for conductivity purposes it is sufficient to have a thickness of only a few hundred nanometers. The weight of the copper in the battery is from about 10% to about 25% depending on the thickness of the foil used for the anode.

[076] The conductive conduit disclosed herein can be used as a current collector in different types of batteries such as, but not limited to, lithium-ion, sodium-ion, metallic lithium, sulfur, and other known batteries. The conductive conduit for the cathode and the conductive conduit for the anode do not need to be the same and can be made of different materials (as a non-limiting example, aluminium and copper as metal layer and PP and PEN as polymer layer, respectively). The mechanical strength of about 6 pm thick PET or PEN is comparable with the mechanical strength of the same thickness of copper foil. However the expansion coefficient of plastic is usually much higher than that of copper. For example, PET has an elongation coefficient at least about 5 times higher, which allows for the lower tolerance or higher rolling speed of a roll-to-roll machine used in anode manufacturing.

[077] In another aspect, a battery comprises a plurality of conductive conduit current collectors, wherein the polymer layer of one or more of the current collectors is configured to seal the battery.

[078] For a standard pouch cell battery design, the conductive conduit may replace the copper foil allowing: standard (for copper or aluminum foil) electrode manufacturing equipment and processes; reduced weight of current collector, hence improved gravimetric energy and power density; reduced volume of current collector, hence improved volumetric energy and power density; improved safety due to the local fusing in case of dendrite or nail penetration and customized design (plastic mechanical and thermal properties, thickness and material of the coating and density of the conductive vias) for the current/voltage of the specific battery design and electrochemistry. [079] An exemplary standard pouch cell 200 with conductive conduit 100 current collectors is depicted in FIG. 5 A. The pouch cell 200 comprises anode active material 201, cathode active material 203 and separator or solid-state electrolyte 205. Arrows 207 indicate low-density current inside the battery (ionic current). Arrows 209 indicate high-density current inside the battery (electronic current).

[080] An exemplary process for tab welding conductive conduits 100 together in a current collector is depicted in FIGS. 5B and 5C. The welding of a single metal tab lead 251 is depicted in FIG. 5B, and the welding of two metal tab leads 251 to a conductive conduit 100 is depicted in FIG. 5C. The tab lead(s) 251 and conductive conduit 100 are positioned between welder electrodes 253. A current of at least about 1 A is then passed through the tab lead(s) 251 and conductive conduit 100, creating welded-through metal 255. The optimum current will depend on the specific properties of the conductive conduit and tab(s), but can be readily determined. Tab welding for the conductive conduit 100 is significantly simplified due to the through-plane conductivity (indeed the process is made possible by the through-plane conductivity of the conductive conduit 100). The through-plane conductivity enables initial current flow through the conductive conduit 100, which then increases while the plastic is melted and replaced with the heated metal from the metal tab connector 251 pressed by the welder pins 253. Alternatively, the tab welding can be done using laser, ultrasound, or other technologies used for standard copper foil current collectors.

[081] An exemplary multi-layer high-voltage battery cell 300 with conductive conduit 100 current collectors is depicted in FIG. 6. The cell 300 comprises anode active material 301, cathode active material 303, separator or solid-state electrolyte 305, current leads 311, current lead contact plates 313 and liquid or solid-state electrolyte 315 and sealant 319. An uncoated (non-conductive polymer layer only) part of conductive conduit 317 is shown. The conductive conduit surface facing the anode active material can be made of copper or have surface coated with copper, while the surface facing the cathode active material can be made of aluminium or have surface coated with aluminium. Arrows 307 indicate low-density current inside the battery 300 (ionic current). Arrows 309 indicate high-density current indicator inside the battery (electronic current). The subcells are arranged in series, forming a high voltage battery. The uncoated part of the conductive conduit 317 can be used to seal the individual sub cells of the battery, simplifying manufacture and reducing weight.

[082] Replacing metallic current collectors with the present conductive conduit slot-in alternative simultaneously improves the performance (about +10% in energy density without penalizing power density), safety (fail-safe fuse feature) and economics of battery products. Safer batteries reduce the cost of ownership of future electric vehicles due to insurance premiums covering fire and damage of their battery packs. [083] Safe-by-design batteries can be re-utilized in different applications, like local energy storage, even after their capacity drops below levels deemed safe or useful. Fire happens due to an internal short circuit, penetration of external objects, or overheating. High power operation of the battery promotes overheating and dendrite growth, leading to internal short circuits. The present conductive conduit increases safety by providing a fail-safe mechanism that addresses these issues.

[084] Commercially available current collectors are made of thin foils of copper metal that is either rolled at high pressure into shape or deposited using electrochemical methods. Substituting copper metal with a plasticbased alternative reduces the amount of material and energy used to manufacture current collector substrates at scale. Polymer-based VCD deposition enables a reduction of more than about 95% of the amount of copper used to make high performance Li-ion batteries, while improving performance metrics at the same time. Clear environmental benefits such as a reduced reliance on mining, metal extraction, metal purification, use of aggressive solvents, transportation, etc. are readily reachable owing to the superior smart plastic method and product.

[085] A cross section of an exemplary conductive conduit cable 400 is depicted in FIG. 7A, and a top view of a conductive conduit cable 400 is depicted in FIG. 7B. The cables 400 are similar to the conductive conduits disclosed above and comprise a polymer layer 401, conductive layers 403 on either side of the polymer layer 401 and conductive paths 405 connecting the conductive layers 403. A difference between the conductive conduit cable 400 and the conductive conduits 100 presented above is a difference in geometry i.e., they have a different shape. The conductive conduit cable 400 has a greater length L than width W such that it can be used to conduct electricity or signals between two distant points.

[086] The thickness of the metal layer and dielectric properties of the polymer layer combined with the conduit geometry (height, width, length) define the electrical signal propagation velocity, intensity losses and bandwidth of frequency of maximal throughput. For example, a signal-carrying cable can be about 2 mm wide and about 100 m long, having a polymer layer with a thickness of about 5 pm with a coating of about 50 nm of copper, silver or gold on each side. The optimum frequency depends on the type of polymer used - PTFE for example would be preferable at about more than 10 GHz signal frequencies due to its low dielectric loses at high frequency.

[087] A cross section of an exemplary cable 500 is depicted in FIG. 8. The cable 500 comprises multiple conductive conduit cables 400, which may be termed sub-cables, separated by a plastic insulator 501. It can conduct multiple signals and is a flat cable that has the functionality of a multi-wire signal cable but where each conductive lead can have a specific resistance, impedance, or signal loss/dissipation factor. The plastic insulator 501 also encompasses all of the conductive conduit cables 400 to electrically insulate them externally. Packing multiple conductive conduits in the multi-layer flat cable enables lightweight and safe signal transmission for aircraft, space and other applications.

[088] The structure of a conductive composite fuse 600 is the same as that of the conductive conduit 100 or conductive conduit cable 400 described above. However, the resistance and melting temperature of the fuse 600 are selected such that for a specific current the fuse 600 heats up beyond a melting temperature of the plastic causing thermal expansion and then melting of the polymer. In the exemplary fuse shown in FIGS. 9 A and 9B, the polymer layer is about 6 pm of PET and there is about 150 nm of copper on both sides of the polymer layer. Melting destroys the integrity of the thin metal layer leading to disconnecting of the current. The fuse 600 before fusing is depicted in FIG. 9A. A conductive composite fuse 600 after fusing is depicted in FIG. 9B. The fuse 600 is connected between plates 601 of a current source. The fuse is conducting a current of 0.5 A in FIG. 9A. Upon passing a 3 A current fusing occurs, as illustrated in FIG. 9B. Controlling the melting temperature of the plastic enables control of maximal temperature of operation of the fuse 600. Thus, the fuse 600 has a number of beneficial characteristics, including, but not limited to, low temperature fusing, tripping off of current with low temperature, and elimination of the possibility of catching fire during fusing. The maximal current value defined by the width of the fuse can be easily adjusted with high precision by adjusting the thickness of conductive layer. Different materials known in the art can be used for different form-factors of the fuse.

[089] Localized fusing can also occur in a large area fuse 600. The local excess of current along the conduit leads to local fusing of the polymer layer. In this case the local short circuit is fused while the other areas can continue to operate. The mechanism of tap fusing in a conductive composite fuse 600 is shown in FIG. 10a. The mechanism of nail fusing in a conductive composite fuse 600 is depicted in FIG. 10B. The conductive conduit has a PET polymer layer of about 6 pm with about 150 nm of copper on each side. The conductive conduit is about 5 cm by about 7 cm, and the tab width is about 1 cm. A current source 601 is connected to opposite sides of a fuse 600, as depicted in FIG. 10A, wherein the left hand connection is to a narrow portion of the fuse. The current flow paths 603 are shown. Maximal current density is seen at fusing point 605, with fusing occurring from a surge current of more than about 2 A/cm. A current source 601 is connected to the perimeter of the fuse 600 depicted in FIG. 10B. The other end of the current source 601 is connected to a point in the middle of the fuse 600. The current flow paths 603 are shown. Maximal current density is seen at fusing point 605, with fusing not occurring below a higher surge current of more than about 4 A/cm. [090] A photograph of a conductive conduit fuse 600 after nail fusing at fusing point 605 is depicted in FIG.

11 A, demonstrating that the fuse has only melted in the vicinity of the fusing point 605. A heat map of the fuse 600 before fusing is depicted in FIG. 1 IB, demonstrating that the heat is concentrated in the vicinity of the fusing point 605.

[091] In yet another aspect, the present disclosure is directed to a method of manufacturing a conductive conduit. The method comprises: providing a polymer layer; and depositing a plurality of metal droplets onto the polymer layer, a temperature of the plurality of metal droplets being greater than a melting point of the polymer layer. This forms conductive paths in the polymer layer as a result of incorporation of the droplets into the polymer layer. Thus, the method efficiently provides the polymer layer with through-plane conductivity without separate steps for creating channels in the polymer layer and then filling the channels with a conductive material. The method may further comprise depositing one or more conductive surface layers on the polymer layer. Depositing one or more conductive surface layers onto the polymer layer may be performed at the same time as depositing metal droplets onto the polymer layer. Depositing metal droplets onto the polymer layer may be performed on both sides of the polymer layer. The method may be performed on a roll-to-roll line, the polymer layer being transferred between the rolls.

[092] Depositing metal droplets onto the polymer layer may be accomplished using virtual cathode deposition (VCD), thermal evaporation deposition, electron beam evaporation deposition, magnetron sputtering, arc deposition, plasma spraying, pulsed laser ablation, or any other suitable process known in the art. Depositing metal droplets onto the polymer layer may comprise vaporizing, ablation, or mechanical distraction a metal target. Depositing metal droplets onto the polymer layer may comprise using an overpowered deposition process, which is to say that the energy, such as the pulse energy, used in the process is greater than used typically for deposition of thin films. For example, in the case of virtual cathode deposition, a pulse energy of greater than about 1 J may be used. The metal droplets may be any conductive material known to the skilled person, such as, but not limited to, copper, aluminum, iron, silver, precious metals such as, but not limited to, gold and platinum, or any other suitable metal. Depositing the metal droplets may be performed under vacuum, such as at a pressure of less than about 10'² mbar, less than about 10'⁴ mbar, or less than about 10'⁶ mbar, although the droplets may also be deposited at atmospheric pressure or greater than atmospheric pressure.

[093] A ratio of the diameter D of the metal droplets to the thickness h of the polymer layer may be such that D = about 0.3A to about 20/?, D = about 0.5A to about 1 Oh, or D = about 0.8A to about 5/ . Alternatively or additionally, D is greater than about 0.3A, greater than about 0.5h or greater than about 0.8A, and/or D is less than about 20h, less than about 10A or less than about 5h. The droplets may be deposited (i.e. the conductive paths may be made) in parallel or simultaneously. The plurality droplets may be deposited in less than about 1 s, less than about 0.1 s or less than about 0.01 s. The droplets may also be known as particles.

[094] The polymer layer may be the same as the polymer layer of the conductive conduit described above.

[095] The method may further comprise rolling, stamping or otherwise patterning the polymer layer in order to increase a surface area of the polymer layer.

[096] In another aspect, the present disclosure is directed to a conductive conduit obtained by the method of manufacturing a conductive conduit, such as that described above.

[097] A flow diagram for a method of manufacturing a conductive conduit is depicted in FIG. 12. The method comprises providing 701 a polymer layer; and depositing 703 a plurality of metal droplets onto the polymer layer, wherein a temperature of the plurality of metal droplets is greater than a melting point of the polymer layer. The polymer layer is made of PET and is about 20 pm thick, but is not limited to this. The metal droplets are deposited using overpowered virtual cathode deposition ‘VCD’ with a copper or other metal target, which is described with reference to FIGS. 13A - 13H.

[098] In another aspect, the present disclosure is directed to a thin film deposition apparatus. A non-limiting example of a thin film deposition apparatus is VCD system 800 comprising a copper metal target 801, VCD (or plasma) source 803 configured to generate a virtual cathode plasma in an area adjacent the target and comprising a hollow electrode 808, lead 805 and gas feed 807, depicted in FIG. 13 A. A substrate such as the polymer layer described above (not shown) is positioned opposite the target 801 such that metal droplets 823 generated from the target 801 are deposited on the substrate. Hollow electrode 808 comprises electrode walls 808a/b that encompasses a cavity within the hollow electrode 808. The hollow electrode 808 itself is ringshaped (although other similar geometries are possible) i.e. it is a hollow ring. In operation, the metal droplets 823 generated from the target 801 pass through the ring of the hollow electrode on their way to the substrate.

[099] The gas feed 807 is configured to supply gas to the VCD source 803. Suitable gases include, but are not limited to, oxygen, nitrogen, argon, helium, xenon, and others. In operation, the gas passes through the VCD source 803 and out through a VCD source outlet 804 in the vicinity of the target 801. Lead 805 is configured to supply a high voltage high current electrical pulse to the electrode 808 of the VCD source 803 from a pulsed power unit, while the target 801 may be grounded. The lead may be connected to only one or both of electrode walls 808a and/or 808b. Electrode walls 808a and 808b may form a single continuous wall. Irrespective of whether electrode walls 808a/b are electrically connected by a permanent electrical connection (e.g. by a cable, conductive mechanical support or in direct contact with each other) in operation they become electrically connected via the plasma.

[100] The exemplified VCD system 800 comprises a modification to a conventional VCD system that may allow a higher pulse energy, although this modification is not essential in order for the VCD system to generate pulse energies sufficient for the manufacture of the conductive conduits described herein. The modification comprises a geometry change to the VCD source 803 enabling more fluid operational gas flow towards the virtual plasma cathode 813 location and provides more space for metal droplets 823 generated from the metal target 801 to propagate. Specifically, a clearance 806 (which may also be referred to as a separation or distance) between the walls of the electrode 808 of the VCD source increases in the direction of the substrate from the target. The clearance may increase continually. As such, walls of the plasma source 803/electrode 808a and/or 808b may be inclined to form an acute angle relative to a line between the target 801 and the substrate (e.g. the shortest line between the target 801 and the substrate).

[101] The hollow electrode 808 comprises a target-side wall or electrode 808a and a substrate-side wall or electrode 808b, both of which extend in the direction of the substrate to the target, with the line from the target to the substrate passing through the center of the electrode 808. Together, the walls 808a, 808b form the cavity of the hollow electrode 808 into which the gas feed 807 supplies gas and in which an initial plasma may be generated, as discussed below. The cavity comprises an outlet 804 at the center of the hollow electrode 808 through which the gas can escape to the area adjacent the target 801. The target-side wall 808a and/or substrate-side wall 808b of the electrode 808 may be inclined by more than about 5 degrees, more than about 10 degrees, more than about 30 degrees, or more than about 45 degrees. The target-side wall 808a and/or substrate-side wall 808b of the electrode 808 may be inclined by less than about 85 degrees, less than about 80 degrees, less than about 60 degrees, or less than about 50 degrees. The target-side wall 808a corresponds to an outer portion of the plasma source/hollow electrode 808 and the substrate- si de wall 808b corresponds to an inner portion of the plasma source/hollow electrode 808. The clearance between the target-side wall 808a and the substrate- si de wall 808b may also increase in the direction of the substrate. This creates a funnel that better directs the gas flow towards the target. The resulting increased gas density provides a higher virtual cathode plasma density that enables higher electron beam currents at increased pulse power. Additionally, as explained above, inclination of the surfaces of the VCD source 803 decreases the length of the VCD source 803 in the axial direction (the direction of the substrate from the target 801). This decreases the interaction of the droplets with the VCD source 803 surfaces which may decrease how often source maintenance and cleaning are required. [102] An initial plasma 809 is generated inside the VCD source 803 (as depicted in FIG. 13B) followed by an expanded plasma 811 (FIG. 13C) (also inside the VCD source 803), followed by a virtual plasma cathode 813 (FIG. 13D) which forms at an outlet 804 of the VCD source 803, which in turns generates an electron beam 815. The modification of the geometry of the VCD source 803 comprises an increase of radial to axial size ratio that may result in a higher density of virtual plasma and higher electron beam energy density. The electron beam 815 ablates the metal target 801 and a plasma of the target material 817 is generated, as depicted in FIG. 13C. A plasma plume 819 is generated from an impacted area of the target 821, as depicted in FIG. 13F. The plasma plume 819 then grows (FIG. 13G) and propagates towards the substrate/polymer layer. Metal droplets 823 are generated at the impacted area of the target 821, as depicted in FIG. 13H. The droplets are ejected along droplet trajectories 825. The modified geometry of the VCD source 803 helps to decrease the interaction of the droplets with the source. The droplets 823 have a higher temperature than a melting temperature of the polymer layer when they reach the polymer layer. For example, the polymer layer may have a melting temperature below about 400 °C. Thus, the droplets melt and pass into the polymer layer, creating conductive paths that extend through the polymer layers.

[103] VCD generates a flux of droplets if the VCD electron beam pulse has an excess of energy (in this case a total energy greater than about 1 J per pulse, for example). Any frequency and pressure can be used within the standard operating range for a VCD system. Any metal target can be used, such as a copper or aluminum target, for example. Increasing the total energy increases the size and number of droplets emitted. The higher the power of the VCD pulse, the higher intensity of micro-droplet flux generated. The micro-droplet flux follows the plume plasma generated by standard virtual cathode deposition. The plume plasma ejected by VCD has a propagation speed in the range of about 0.1 km/s to about 100 km/s. In the case of a VCD pulse having an excess of energy, in addition to the plume plasma of material which forms a thin film coating, larger (between about 1 pm and about 100 pm) droplet-type pieces of material are ejected at a much lower velocity (between about 1 m/s to about 100 m/s). In this case, the droplets have sufficient energy to implant into and traverse up to an about 50 nm copper layer and up to an about 200 pm PET film, which causes an electrically conductive link to be made between the top and the bottom of the film. Higher energy droplets (i.e. droplets generated with a greater excess of energy) can of course implant into and traverse thicker metal and polymer layers. The excess of the VCD pulse energy provides the thermal energy to the micro-droplets sufficient to melt the polymer substrate and embed in it forming conductive paths. The diameter of the droplet is the same order of magnitude as the thickness of the polymer layer, but this is not essential. The droplet size can be readily controlled by the skilled person by varying the pulse energy. [104] A single impact site of a metal droplet on a polymer film is shown both on the front and the back of a polymer layer in FIGS. 14A and 14B. The impact sire has a crater-like appearance on the side of impact (FIG. 14A) and bump or bulge on the opposite side (FIG. 14B). The polymer film has a conductive copper layer deposited on both sides.

[105] Using VCD, a conductive layer of the metal target 801 material is simultaneously deposited on the polymer layer. The conductive paths fuse with the conductive surface layer and thus make the polymer layer conductive in the plane perpendicular to the conductive layer on the polymer layer. The conductive surface layers have a thickness of about 50 nm in the present nonlimiting example. The polymer layer can then be turned over and the process repeated to provide more conductive paths and in plane conductivity on both sides of the polymer layer. Alternatively, the other side of the polymer layer may be coated with a conductive layer using a different process to VCD.

[106] Photographic images of micro-droplet flux generation with different VCD pulse energies are shown in FIGS. 15A-15C, which are images taken with about 8 ms exposure and about 1 ms delay after the electron beam pulse. A light burst of droplets corresponding to a lower pulse energy is shown in FIG. 15 A. A medium burst of droplets corresponding to an intermediate pulse energy is shown in FIG. 15B. A heavy burst of droplets corresponding to a higher pulse energy is shown in FIG. 15C. Thus, it can be seen that increasing the pulse energy increases the number and energy of droplets generated in a single pulse.

[107] The hot droplets can be produced with different methods including high speed injector ink-jet type methods where the particles are accelerated by high-speed gas or liquid. Also, it is possible to use mechanical acceleration from a rotated target or electrostatic acceleration of charged particles. In addition, droplets can be generated using thin film deposition processes like magnetron deposition, a plasma arc, pulsed laser deposition, pulsed electron beam deposition, or other similar process. Micro droplet generation in these processes is generally considered to decrease the quality of thin films. However, by adjusting the deposition process (for example, but not limited to, by increasing the energy/power of the deposition source) microdroplet generation may be used to implant droplets into the polymer substrate to provide through plane conductivity as explained above.

EQUIVALENTS

[108] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific embodiments described specifically herein. Such equivalents are intended to be encompassed in the scope of the following claims.

Claims

1. A conductive conduit, comprising: a polymer layer; a conductive layer on the polymer layer; and a plurality of conductive paths in the polymer layer, each conductive path extending from the conductive layer to an opposite side of the polymer layer, and each conductive path comprising a convex end portion at one end, the convex end portion extending beyond and radially along the polymer layer.

2. A conductive conduit according to claim 1, wherein each of the conductive paths comprises a concave end portion at the other end of each conductive path.

3. A conductive conduit according to claim 1, wherein each of the conductive paths comprises a convex end portion at the other end of each conductive path extending beyond and radially along the polymer layer.

4. A conductive conduit according to any preceding claim, the conductive layer being on a first face of the polymer layer and the conductive conduit comprising a further conductive layer on a second face of the polymer layer opposite the first face.

5. A conductive conduit according to any preceding claim, wherein the conductive paths are irregularly distributed in the polymer layer.

6. A conductive conduit according to any preceding claim, wherein a thickness of each end portion is greater than a thickness of the conductive layer.

7. A conductive conduit according to any preceding , wherein each end has a concave portion between the polymer layer and the conductive layer.

8. A conductive conduit according to any preceding claim, wherein each conductive path comprises an intermediate portion in the polymer layer connected to its convex end portion, and the convex end portion extends laterally beyond the intermediate portion within the polymer layer.

9. A conductive conduit according to any preceding claim, wherein each conductive path extends radially towards its convex end portion within the polymer layer.

10. A conductive conduit according to any preceding claim, wherein the plurality of conductive paths are homogeneous.

11. A current collector for a battery, comprising the conductive conduit according to any of claims 1-10.

12. A fuse, comprising the conductive conduit according to any of claims 1-10.

13. A cable, comprising the conductive conduit according to any of claims 1-10.

14. A method of manufacturing a conductive conduit, the method comprising: providing a polymer layer; and depositing a plurality of metal droplets onto the polymer layer, a temperature of the plurality of metal droplets being greater than a melting point of the polymer layer.

15. A method according to claim 14, wherein depositing the plurality of metal droplets onto the polymer layer comprises using virtual cathode deposition.

16. A method according to claim 14 or 15 , further comprising depositing one or more conductive surface layers onto the polymer layer.

17. A method according to claim 16, wherein depositing one of the one or more conductive surface layers onto the polymer layer is performed at the same time as depositing metal droplets onto the polymer layer.

18. A method according to any one of claim 14 to 17, wherein depositing a plurality of metal droplets onto the polymer layer comprises vaporizing a metal target.

19. A method according to any one of claims 14 to 18, wherein depositing a plurality of metal droplets is performed under vacuum.

20. A method according to any one of claims 14 to 19, wherein a ratio of the diameter D of the metal droplets to the thickness h of the polymer layer is such that D is about 0.3A to about 20A, D is about Q.5h to about 10/ or D is about 0.8A to about 5h.

21. A conductive conduit according to any one of claims 1 to 10 or a method according to claim 16 or 17, wherein the polymer layer has a tensile strength of at least 150 N/m² and the conductive surface layer is a metal layer with a thickness of 0.5 pm or less.

22. A virtual cathode deposition system, comprising: a target; a substrate opposite the target; and a plasma source configured to generate a plasma in an area adjacent the target, a clearance between walls of the plasma source increasing in the direction of the substrate from the target.

23. A system according to claim 22, wherein the walls of the plasma source are walls of a hollow electrode.

24. A system according to claim 22 or 23, wherein the plasma source is ring-shaped.

25. A system according to any of claims 22 to 24, wherein the walls are walls of an inner portion of the plasma source.