WO2022152385A1

WO2022152385A1 - Current collector for an anode of an energy storage device, energy storage device, method for forming a current collector for an anode of an energy storage device, and apparatus for forming a current collector for an anode of an energy storage device

Info

Publication number: WO2022152385A1
Application number: PCT/EP2021/050717
Authority: WO
Inventors: Roland Trassl
Original assignee: Applied Materials, Inc.
Priority date: 2021-01-14
Filing date: 2021-01-14
Publication date: 2022-07-21

Abstract

A current collector (100) for an anode of an energy storage device is described. The current collector (100) includes a flexible substrate (101) having a first surface (101a) and a second surface (101b); and a conductive layer (110) provided on at least one of the first surface (101a) or second surface of the flexible substrate (101), wherein the conductive layer (110) includes a first material (110a) and a second material (110b) different from the first material, the first material (110a) and the second material (110b) being gradually provided in the conductive layer (110).

Description

CURRENT COLLECTOR FOR AN ANODE OF AN ENERGY

STORAGE DEVICE, ENERGY STORAGE DEVICE, METHOD FOR FORMING A CURRENT COLLECTOR FOR AN ANODE OF AN

ENERGY STORAGE DEVICE, AND APPARATUS FOR FORMING A CURRENT COLLECTOR FOR AN ANODE OF AN ENERGY STORAGE DEVICE

FIELD

[0001] Examples of the present disclosure relate to a current collector, an energy storage device, a method for forming a current collector, and an apparatus for forming a current collector. Examples of the present disclosure particularly relate to a current collector for an anode of an energy storage device, an energy storage device, a method for forming a current collector for an anode of an energy storage device, and an apparatus for forming a current collector for an anode of an energy storage device.

BACKGROUND

[0002] Rechargeable electrochemical storage systems are currently becoming increasingly valuable for many fields of everyday life. High-capacity electrochemical energy storage devices, such as lithium-ion (Li-ion) batteries, are used in a growing number of applications, including portable electronics, medical, transportation, grid- connected large energy storage, renewable energy storage, and uninterruptible power supply (UPS). Traditional lead/sulfuric acid batteries often lack the capacitance and are often inadequately cycleable for these growing applications. Lithium-ion batteries are thought to have the best chance. [0003] Energy storage devices, in particular Li-ion batteries, include a current collector. The current collector typically includes a conducting material for conducting current. Current collectors formed from a single conducting material, i.e. consisting of this single conducting material, are often thick and heavy, having an adverse effect on the volumetric energy density (Wh/1) and gravimetric energy density (Wh/kg). Thus, it has been proposed to form the current collector by depositing a conductive material on a substrate.

[0004] Several methods are known for depositing a material on a substrate. For instance, substrates may be coated by a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, a plasma enhanced chemical vapor deposition (PECVD) process, etc. Typically, the process is performed in a process apparatus or process chamber in which the substrate to be coated is located. However, the proposed current collectors still increase the volumetric or gravimetric energy density, are unstable or cost intensive to produce.

[0005] Accordingly, there is a demand for providing improved anode electrode structures for lithium-ion batteries, improved lithium-ion batteries, and improved methods for making anode electrode structures and lithium-ion batteries as well as improved processing systems for fabricating such anode electrode structures which overcome at least some of the problems of the state of the art.

SUMMARY

[0006] In light of the above, an anode electrode structure, a current collector for an anode of an energy storage device, an energy storage device, a method for forming a current collector for an anode of an energy storage device, and an apparatus for forming a current collector for an anode of an energy storage device according to the independent claims are provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0007] According to an aspect of the present disclosure, a current collector for an anode of an energy storage device is provided. The current collector includes a flexible substrate having a first surface and a second surface. A conductive layer is provided on at least one of the first surface or second surface of the flexible substrate. The conductive layer includes a first material and a second material different from the first material. The first material and the second material are gradually provided in the conductive layer.

[0008] According to a further aspect of the present disclosure, an energy storage device is provided. The energy storage device includes an anode, a cathode, at least one polymeric or fabric separator or a solid electrolyte between the anode and the cathode, and at least one current collector in contact with the anode. The current collector includes a flexible substrate having a first surface and a second surface. A conductive layer is provided on at least one of the first surface or second surface of the flexible substrate. The conductive layer includes a first material and a second material different from the first material. The first material and the second material are gradually provided in the conductive layer.

[0009] According to a further aspect of the present disclosure, a method for forming a current collector for an anode of an energy storage device is provided. The method includes providing a flexible substrate having a first surface and a second surface. A conductive layer is formed on at least one of the first surface or second surface of the flexible substrate. The conductive layer includes a first material and a second material different from the first material. The first material and the second material are gradually provided in the conductive layer.

[0010] According to a further aspect of the present disclosure, an apparatus for forming a current collector for an anode of an energy storage device is provided. The apparatus includes a deposition arrangement including a deposition zone configured to convey a flexible substrate, a first material source having a first material, and a second material source having a second material different from the first material. The deposition arrangement is configured to form a conductive layer on a surface of the flexible substrate. The conductive layer includes a first material and a second material different from the first material. The first material and the second material are gradually provided in the conductive layer.

[0011] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIGs. 1 A and IB show schematic views of a current collector for an anode of an energy storage device according to embodiments described herein;

FIGs. 2A and 2B show schematic views of a current collector for an anode of an energy storage device according to embodiments described herein; FIG. 3 shows a schematic view of an energy storage device according to embodiments described herein;

FIG. 4 shows a schematic view of an energy storage device according to embodiments described herein;

Fig. 5 shows a block diagram for illustrating a method for forming a current collector for an anode of an energy storage device according to embodiments described herein;

Fig. 6 shows a schematic view of an apparatus for forming a current collector for an anode of an energy storage device according to embodiments described herein;

Figs. 7A and 7B show schematic views of details of an apparatus for forming a current collector for an anode of an energy storage device according to embodiments described herein;

Figs. 8A to 8C show schematic views of details of an apparatus for forming a current collector for an anode of an energy storage device according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0013] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, same reference numbers refer to same components. Only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0014] With exemplary reference to FIGS. 1 A and IB, a current collector 100 according to the present disclosure is described. The current collector 100 can be a current collector for an anode. In particular, the current collector 100 can be a current collector for an anode of an energy storage device, such as a lithium-ion (Li-ion) battery.

[0015] According to embodiments, which can be combined with any other embodiments described herein, the current collector 100 can include a flexible substrate 101 having a first surface 101a and a second surface 101b. The first surface 101a can be opposite the second surface 101b. In particular, the first surface 101a and the second surface 101b can be opposing major surfaces of the flexible substrate 101.

[0016] According to embodiments, which can be combined with any other embodiments described herein, a conductive layer 110 can be provided on at least one of the first surface 101a or the second surface 101b of the flexible substrate 101. That is, the conductive layer 110 can be provided on the first surface 101a, the second surface 101b or on both the first surface 101a and the second surface 101b.

[0017] According to embodiments, which can be combined with any other embodiments described herein, the conductive layer 110 includes a first material and a second material different from the first material. The first material and the second material can be gradually provided in the conductive layer. In particular, the first material and the second material can be provided in the conductive layer 110 with a varying concentration along a direction perpendicular to the first surface 101a and/or the second surface 101b of the flexible substrate. For example, in portions of the conductive layer 110 closer to the one of the first surface 101a and the second surface 101b, on which the conductive layer 110 is provided, a larger amount of the first material than of the second material may be present, whereas in portions of the conductive layer 110 further away from the one of the first surface 101a and the second surface 101b, on which the conductive layer 110 is provided, a larger amount of the second material than of the first material may be present.

[0018] According to embodiments, which can be combined with any other embodiments described herein, the first material and the second material can form or constitute the conductive layer 110. More specifically, the conductive layer 110 can essentially consist of the first material and the second material, and impurities.

[0019] Accordingly, an improved current collector for an anode of an energy storage device can be provided. In particular, the current collector as described herein can provide an improved inter-material adhesion. For example, the first material and the second material can be selected according to the specific requirements of the current collector and can provide an improved adhesion between the first material and the second material as well as between the first material and/or the second material and the substrate. For example, the first material can be selected to provide good adhesion to the flexible substrate. Further, the gradual provision of the first material and the second material can provide a good adhesion between the first material and the second material even in the case where sharp interface between the first material and the second material does not provide good adherence. In particular, a good adhesion can be provided due to material mixing in the transition region.

[0020] Thus, embodiments described herein can reduce weight, cost and improve safety in an energy storage device, such as a Li-ion battery, and/or can increase throughput in the manufacturing.

[0021] Before various further embodiments of the present disclosure are described in more detail, some aspects with respect to some terms used herein are explained. [0022] In the present disclosure, a “current collector for an anode of an energy storage device” can be understood as a current collector configured for being used for or in an anode electrode, particularly for lithium-ion batteries. In particular, an “collector for an anode of an energy storage device” according to the present disclosure can be understood as a current collector that is intended to be in contact with an anode of the finished energy storage device.

[0023] In the present disclosure, a “substrate” is particularly a flexible substrate. A “flexible substrate” can be understood as a bendable substrate. The term “flexible substrate” or “substrate” may be synonymously used with the term “foil” or the term “web”. In particular, it is to be understood that embodiments of the processing system described herein can be utilized for processing any kind of flexible substrate, e.g. for manufacturing flat coatings with a uniform thickness. For example, a flexible substrate as described herein may include materials like PET, HC-PET, PE, PI, PU, TaC, OPP, CPP, one or more metals (e.g. copper or aluminum), paper, combinations thereof, and already coated substrates like Hard Coated PET (e.g. HC-PET, HC-TaC) or metal coated polymeric substrates (e.g. copper coated PET) and the like. For example, the substrate thickness can be 0.5 pm or more and 1 mm or less. Typically, the substrate thickness TS of a substrate employed in an anode electrode structure as described herein is 1 pm < TS < 15 pm, particularly 3 pm < TS < 10 pm. According to embodiment described hereon, the flexible substrate can be a polymeric film.

[0024] In the present disclosure, a “conductive layer” can be understood as a layer that allows flow of charge (electrical current) in one or more directions. In particular, the “conductive layer” may allow flow of charge at typical operating conditions, such as temperatures and voltages, in energy storage devices, specifically of Li-ion batteries. For example, the conductive layer can be a metal layer and/or include metal materials. [0025] FIG. IB illustrates a section of FIG. 1A. In particular, Fig. IB illustrates the gradual provision or gradual transition of the first material 110a and the second material 110b in the conductive layer 110 by showing two different point types.

[0026] As illustrated in Fig IB, an amount of the first material 110a can decrease along a direction perpendicular to the one of the first surface 101a and second surface 101b of the flexible substrate 101, specifically on which the conductive layer 110 is provided.

[0027] As further illustrated in Fig IB, an amount of the second material 110b can increase along a direction perpendicular to the one of the first surface 101a and second surface 101b of the flexible substrate 101, specifically on which the conductive layer 110 is provided.

[0028] In particular, the first material 110a and the second material 110b can be provided with an opposing distribution in the conductive layer 110. More specifically, the opposing distribution can be along the direction perpendicular to the one of the first surface 101a and second surface 101b of the flexible substrate 101, specifically on which the conductive layer 110 is provided.

[0029] According to embodiments, which can be combined with any other embodiments described herein, the first material 110a can be provided in the conductive layer 110 with a first material concentration. Specifically, the first material concentration can decrease along a direction perpendicular to the one of the first surface 101a and second surface 101b of the flexible substrate 101. More specifically, the first material concentration can be highest proximate to the one of the first surface 101a and second surface 101b of the flexible substrate 101.

[0030] According to embodiments, which can be combined with any other embodiments described herein, the second material 110b can be provided in the conductive layer 110 with a second material concentration. Specifically, the second material concentration can increase along a direction perpendicular to the one of the first surface 101a and second surface 101b of the flexible substrate 101. More specifically, the second material concentration can be highest distal to the one of the first surface 101a and second surface 101b of the flexible substrate 101.

[0031] According to embodiments, which can be combined with any other embodiments described herein, the first material 110a and the second material 110b can be co-evaporated. For example, the first material 110a can be evaporated with a higher intensity than the second material 110b at the beginning of the evaporation of the conductive layer 110. During the evaporation of the conductive layer 110, the intensity of the first material 110a can be decreased and/or an intensity of the second material 110b can be increased. At the end of the evaporation process, the first material 110a can be evaporated with a lower intensity than the second material 110b. As an example, such an evaporation process can beneficially form a gradual provision of the first material and the second material in the conductive layer, specifically with opposing distributions.

[0032] According to embodiments, which can be combined with any other embodiments described herein, the conductive layer 110 can be formed from one or more conductive materials. The conductive materials, such as the first material 110a and the second material 110b, can be metal materials. For example, the first material 110a can be Al (aluminum) and/or the second material 110b can be Cu (copper).

[0033] For a conventional energy storage device, such as a Li-ion battery with liquid electrolyte, the material of choice for the anode current collector is Cu, whereas Al is used on the cathode side. These materials need to be selected because of their electrochemical stability at positive or negative potential, respectively. Cu, however, is not desirable due to the high density and hence negative impact on the gravimetric energy density. Therefore, the present disclosure proposes to use Al as the current collector, however it is capped with Cu for the contact with the electrolyte. Since the adhesion between Al and Cu is not good, the present disclosure proposes to gradually form the layers, therefore having excellent adhesion due to the transition or mixing region.

[0034] The person skilled in the art will understand that for current liquid electrolytes, the anode current collector can have a Cu surface (second material 110b). The conducitve layer underneath the Cu surface could be anything, Al having the lowest density and cost (first material 110a). In upcoming batteries, e.g. solid-state batteries, there may be different materials possible/necessary, depending on the choice of the electrolyte, e.g. Ni or SST. Here, the same graded layer could be applied.

[0035] While FIG.s 1A and IB illustrate the conductive layer 110 provided on one of the first surface 101a and second surface 101b of the flexible substrate 101, specifically on the first surface 101a, FIG.s 2 A and 2B illustrate two conductive layers 110, 120 provided on the first surface 101a and the second surface 101b of the flexible substrate 101, respectively. For example, a first conductive layer 110 can be provided on the first surface 101a and a second conductive layer 120 can be provided on the second surface 101b. The first conductive layer 110 can include a first material 110a and a second material 110b different from the first material. The first material and the second material can be gradually provided in the first conductive layer. The second conductive layer 120 can include a first material 120a and a second material 120b different from the first material. The first material and the second material can be gradually provided in the second conductive layer 120.

[0036] As can be understood from the description herein, in the case that a conductive layer 110, 120 is formed on both the first surface 101a and the second surface 101b of the flexible substrate 101, a description such as “proximate to the one of the first surface 101a and second surface 101b of the flexible substrate 101” pertains to the one of the first surface 101a and second surface 101b on which the respective conductive layer 110 is provided. Similar considerations apply for “direction perpendicular to the one of the first surface 101a and second surface 101b of the flexible substrate 101”, “distal to the one of the first surface 101a and second surface 101b of the flexible substrate 101” etc.

[0037] With exemplary reference to FIG. 3, an energy storage device 20 according to the present disclosure is described. The energy storage device 20 can include two electrodes of opposing polarity, namely a negative anode 21 and a positive cathode 22. The cathode 22 and the anode 21 can be insulated by a separator 23 arranged between the cathode and the anode to prevent short circuits between the cathode and the anode. Further, the battery can include an electrolyte 24 which is used as an ion conductive matrix. The person skilled in the art will understand that the electrolyte cannot be a separate layer such as in Fig. 3, but can be soaked into the porous cathode and anode material and can also be inside the separator.

[0038] Accordingly, the electrolyte can be an ion conductor, which may be liquid, in gel form or solid. Particularly in the case of a solid electrolyte between the anode and the cathode, the separator 23 can be omitted.

[0039] The separator can be ion-pervious and permit an exchange of ions between the anode and cathode in a charge or discharge cycle. For example, the separator 23 can be a porous polymeric ion-conducting polymeric substrate. In particular, the porous polymeric substrate may be a multi-layer polymeric substrate. Additionally or alternatively, the separator 23 can be a fabric separator.

[0040] With exemplary reference to FIGS. 1 A, IB, 2A, 2B and 3, according to embodiments which can be combined with any other embodiments described herein, the energy storage device 20 can include at least one current collector 100 in contact with the anode 21. Specifically, the at least one current collector 100 can be part of the anode 21 illustrated in FIG. 3 [0041] According to embodiments, which can be combined with any other embodiments described herein, the energy storage device 20 is a Li-ion battery.

[0042] With exemplary reference to FIGS. 1 A, IB, 2A, 2B and 4, according to embodiments which can be combined with any other embodiments described herein, the energy storage device 20 can include an anode 21 having an anode electrode structure 10 including a substrate 11 having a first surface and an opposite second surface . A first lithium film 12 can be provided on the first surface. A second lithium film 13 can be provided on the second surface. Additionally, the anode electrode structure 10 can include a first interface film 14 provided on the first lithium film 12. Further, the anode electrode structure 10 can include a second interface film 15 provided on the second lithium film 13. The first interface film 14 and the second interface film 15 can be lithium- ion conducting. In particular, the anode electrode structure 10 of the energy storage device 20 can be in contact with the conductive layer 110.

[0043] With exemplary reference to FIGS. 1 A, IB, 2A, 2B and 4, according to embodiments which can be combined with any other embodiments described herein, the energy storage device 20 can include at least one current collector 100 in contact with the anode 21. Specifically, the at least one current collector 100 can be part of the anode 21 illustrated in FIG.4. More specifically, the current collector 100 can be in contact with the anode electrode structure 10. Even more specifically, the conductive layer 110 of the current collector 100 can be in contact with the anode electrode structure 10.

[0044] According to embodiments, which can be combined with any other embodiments described herein, the energy storage device 20 includes a cathode 22 having a cathode electrode structure having a substrate including or consisting of aluminum. In particular, the substrate may include a polymeric substrate 26, particularly a polymeric foil, having an aluminum coating 27 on both sides of the polymeric foil. [0045] According to embodiments, which can be combined with any other embodiments described herein, the energy storage device 20 is a Li-ion battery.

[0001] With exemplary reference to the block diagram of FIG. 5, a method 400 for forming a current collector 100 for an anode of an energy storage device 20 device according to the present disclosure is described. According to embodiments, which can be combined with any other embodiments described herein, the method includes providing (represented by block 410 in FIG. 5) a flexible substrate 101 having a first surface 101a and a second surface 101b. For example, the flexible substrate can be a polymeric film. Further, the first surface 101a and second surface 101b can be opposing major surfaces of the flexible substrate 101.

[0046] Further, the method 400 can include forming (represented by block 420 in FIG. 5) a conductive layer 110 on at least one of the first surface 101a or second surface 101b of the flexible substrate 101. The conductive layer 110 can be formed by evaporating a conductive material on at least one of the first surface 101a or second surface 101b of the flexible substrate 101.

[0047] According to embodiments, which can be combined with any other embodiments described herein, the conductive layer 110 can include a first material 110a and a second material 110b different from the first material, the first and second materials can be gradually provided in the conductive layer. Specifically, the conductive layer 110 can be formed by co-evaporating the first material 110a and the second material 110b. More specifically, the conductive layer 110 can be formed by co-evaporating the first material 110a with a decreasing intensity and the second material 110b with an increasing intensity. Accordingly, the concentration of the first material 110a and the second material 110b may change with time and, thus, with growth of the conductive layer 110. Accordingly, the first material 110a can be provided in the conductive layer 110 with a decreasing material concentration and/or the second material 110b can be provided in the conductive layer 110 with an increasing material concentration, considered from the one of the first surface 101a and second surface 101b of the flexible substrate 101 on which the conductive layer 110 is provided.

[0048] It is to be understood that in the method 400 for forming a current collector 100 for an anode of an energy storage device 20, the flexible substrate 101 can be the flexible substrate 101 according to embodiments described herein and the conductive layer 110 can be the conductive layer 110 according to embodiments described herein.

[0049] Further, it is to be understood that the method 400 for forming a current collector 100 for an anode of an energy storage device 20 can be conducted by using an apparatus for forming a current collector for an anode of an energy storage device, such as a roll-to-roll processing system, as exemplarily described with reference to FIG.s 6 to 8.

[0050] With exemplary reference to FIG. 6, an apparatus 500 for forming a current collector 100 for an anode of an energy storage device 20 according to the present disclosure is described.

[0051] The apparatus 500 can include a deposition arrangement 510. The deposition arrangement 510 can include a deposition conveyor 512 configured to convey a flexible substrate 101, a first material source 514a having a first material, and/or a second material source 514b having a second material different from the first material. The deposition arrangement 510 can be configured to form a conductive layer 110 on a surface 101a, 101b of the flexible substrate 101. The conductive layer 110 can include a first material 110a and a second material 110b different from the first material. The first and second materials can be gradually provided in the conductive layer 110.

[0002] In the present disclosure, an “apparatus for forming a current collector for an anode of an energy storage device according to the present disclosure” can be understood as an apparatus or processing system configured for producing anode current collectors according to embodiments described herein. In particular, the substrate processing system can be a roll-to-roll processing system for continuously processing a flexible substrate. More specifically, the apparatus can be a vacuum processing system having at least one vacuum chamber with a deposition unit for depositing material on the flexible substrate. For instance, the apparatus may be configured for a substrate length of 500 m or more, 1000 m or more, or several kilometers. The substrate width can be 300 mm or more, particularly 500 mm or more, more particularly 1 m or more. Further, the substrate width can be 3 m or less, particularly 2 m or less.

[0052] According to embodiments, which can be combined with any other embodiments described herein, the apparatus 500 for forming a current collector 100 for an anode of an energy storage device 20 can include a vacuum deposition chamber 501 in which the deposition arrangement 510 can be provided.

[0053] In the present disclosure, a “vacuum deposition chamber” can be understood as a chamber configured to provide a vacuum within the chamber and including a deposition unit for depositing material on the substrate. The term “vacuum”, as used herein, can be understood in the sense of a technical vacuum having a vacuum pressure of less than, for example, 10 mbar. Typically, the pressure in a vacuum chamber as described herein may be between 10-5 mbar and about 10-8 mbar, more typically between 10-5 mbar and 10-7 mbar, and even more typically between about 10-6 mbar and about 10-7 mbar. It is to be understood that typically the vacuum level during processing is higher and depends on the process.

[0054] In the present disclosure, a “deposition arrangement” can be understood as a unit, arrangement or device configured for depositing material on a substrate, in particular a material of the layers as described herein. For example, the deposition unit may be a sputter deposition unit, a CVD deposition unit, an evaporation deposition unit, a PVD or PECVD deposition unit, sputter deposition unit, or another suitable deposition unit.

[0055] According to embodiments, which can be combined with any other embodiments described herein, the deposition conveyor 512 can be or include a coating drum 512.

[0056] In the present disclosure, a “coating drum” can be understood as a drum or a roller having a substrate support surface for contacting the flexible substrate. In particular, the coating drum can be rotatable about a rotation axis and may include a substrate guiding region. Typically, the substrate guiding region is a curved substrate support surface, e.g. a cylindrically symmetric surface, of the coating drum. The curved substrate support surface of the coating drum may be adapted to be (at least partly) in contact with the flexible substrate during operation of the processing system.

[0057] Additionally, as exemplarily shown in FIG. 6, the deposition conveyor 512 can be configured for transporting the flexible substrate 101 such that a front side of the flexible substrate 101 faces deposition arrangement 510 and a back side of the flexible substrate faces the deposition conveyor 512. The front side of the flexible substrate 101 can the one of the first surface 101a or second surface 101b in which the conductive layer 110 is currently formed.

[0058] As further exemplarily shown in FIG. 6, the apparatus 500 can include an unwind drum 522, a rewind drum 524, a tension roller 526 and several further rollers for winding and conveying the flexible substrate 101 in the apparatus 500.

[0059] Further, the apparatus 500 can include a layer monitoring device 530 for monitoring properties of the conductive layer 110.

[0060] Fig. 7 exemplarily shows the first material source 514a and the second material source 514b including or being first and second crucibles. In particular, a first crucible 514a can hold the first material and a second crucible 514b can hold the second material.

[0061 ] Fig. 6 further exemplarily shows an electron beam gun 516 configured to evaporate the first and second materials in the first and second material sources or crucibles 514a, 514b. In particular, the electron beam gun 516 can be configured to emit an electron beam towards the first and second material sources 514a, 514b. When the electron beam hits the first and second material sources 514a, 514b, the first and second material being hit by the electron beam may evaporate and be deposited on the flexible substrate 101. Accordingly, the first material 110a and the second material 110b can be co-evaporated for forming the conductive layer 110.

[0062] Further, by controlling the power and time of the electron beam hitting the first or second material source, the amount of the first and second material being evaporated can be controlled. According to embodiments, which can be combined with any other embodiments described herein, the electron beam gun 516 can be configured to scan between the first material source 514a and the second material source 514b.

[0063] FIGs. 7A and 7B exemplarily show the deposition arrangement 510 according to embodiments of the present disclosure. In particular, FIG. 7A shows a side view of the deposition arrangement 510 and FIG. 7B shows a top view of the first material source 514a and the second material source 514b.

[0064] FIG. 7A shows the deposition conveyor 512 or coating drum 512, the first material source 514a, the second material source 514b, the electron beam gun 516 and the electron beam 517. As can be seen in FIG. 7A, the first material source 514a and the second material source 514b can be arranged next to each other and/or next to the deposition conveyor 512.

[0065] FIG. 7B shows a top view of the first material source 514a and the second material source 514b. FIG. 7B further illustrates a line along which the electron beam 517 is moved in the first material source 514a and the second material source 514b, respectively. For example, the electron beam 517 can be scanned or moved along the lines indicated in FIG. 7B.

[0066] Assuming a constant power of the electron beam 517, an evaporation intensity of the first material and the second material may depend upon a time the electron beam 517 hits the first and second material sources 514a, 514b, respectively. Accordingly, if a high evaporation intensity, and thus concentration, of the first material 110a is intended, the electron beam 517 can be controlled to be provided in the first material source 514a longer than in the second material source 514b, and vice versa. In the case of a scanning electron beam 517, the electron beam gun 516 can be configured to perform more turns in the material source of which a higher intensity and concentration is intended at this time of the evaporation process.

[0067] Additionally or alternatively, the power of the electron beam 517 can be varied to obtain or support the above effect.

[0068] FIGs. 8A to 8C show schematic views of details of an apparatus 500 for forming a current collector 100 for an anode of an energy storage device 20, in particular of the deposition arrangement 510 according to embodiments described herein.

[0069] FIGs. 8A to 8C show alternative first and second material sources 514a, 514b and scanning patterns of the electron beam gun 516.

[0070] According to embodiments, which can be combined with any other embodiments described herein, the first material source 514a can include more than one crucible and/or the second material source 514b can include more than one crucible, irrespective of the specific configuration of the first and second material sources 514a. [0071] FIG. 8 A shows an alternative scanning pattern of the electron beam gun 516. In Fig. 7B, the electron beam 517 scans along the first and second material sources 514a, 514b across a width substrate of the flexible substrate 101 for uniform deposition. FIG. 8a illustrates that an area scanned by the electron beam 517 can also be varied for obtaining different evaporation intensities. For example, the scanned area can be controlled to be larger for the one of the first and second material sources 514a, 514b for which a higher evaporation intensity is intended.

[0072] FIGs. 8B and 8C show other evaporation techniques, i.e. without an electron beam gun, for co-evaporating the first and second materials 110a, 110b. In particular, FIG. 8B shows inductively heated crucibles, and FIG. 8C shows resistively heated evaporation boats.

[0073] In view of the above, it is to be understood that compared to the state of the art, embodiments of the present disclosure beneficially provide a current collector for an anode of an energy storage device, an energy storage device, a method for forming a current collector for an anode of an energy storage device, and an apparatus for forming a current collector for an anode of an energy storage device which are improved compared to the state of the art.

[0074] While the foregoing is directed to the embodiments described herein, other and further embodiments may be devised without departing from their basic scope, and the scope is determined by the claims that follow.

Claims

1. A current collector (100) for an anode of an energy storage device, the current collector comprising: a flexible substrate (101) having a first surface (101a) and a second surface (101b); and a conductive layer (110) provided on at least one of the first surface (101a) or second surface (101b) of the flexible substrate, wherein the conductive layer (110) includes a first material (110a) and a second material (110b) different from the first material, the first material and the second material being gradually provided in the conductive layer.

2. The current collector of claim 1, wherein the flexible substrate (101) is a polymeric film.

3. The current collector of any one of claims 1 to 2, wherein the first material (110a) is Al and/or the second material is Cu.

4. The current collector of any one of claims 1 to 3, wherein an amount of the first material (110a) decreases along a direction perpendicular to the one of the first surface and second surface of the flexible substrate (101).

5. The current collector of any one of claims 1 to 4, wherein an amount of the second material (101b) increases along a direction perpendicular to the one of the first surface and second surface of the flexible substrate (101).

6. The current collector of any one of claims 1 to 5, wherein the first material (110a) is provided in the conductive layer (110) with a first material concentration, the first material concentration decreasing along a direction perpendicular to the one of the first surface and second surface of the flexible substrate (101).

7. The current collector of claim 6, wherein the first material concentration is highest proximate to the one of the first surface and second surface of the flexible substrate (101).

8. The current collector of any one of claims 1 to 7, wherein the second material (110b) is provided in the conductive layer with a second material concentration, the second material concentration increasing along a direction perpendicular to the one of the first surface and second surface of the flexible substrate (101).

9. The current collector of claim 8, wherein the second material concentration is highest distal to the one of the first surface and second surface of the flexible substrate (101).

10. The current collector of any one of claims 1 to 9, wherein the first material and the second material are co-evaporated.

11. An energy storage device (20), comprising: an anode (21); a cathode (22); at least one polymeric or fabric separator (23) or a solid electrolyte (23) between the anode and the cathode; and at least one current collector (100) according to any one of claims 1 to 10 in contact with the anode.

12. A method for forming a current collector for an anode of an energy storage device, the method comprising: providing a flexible substrate (101) having a first surface (101a) and a second surface (101b), and forming a conductive layer (110) on at least one of the first surface (101a) or second surface (101b) of the flexible substrate (101), wherein the conductive layer (110) includes a first material (110a) and a second material (110b) different from the first material, the first and second materials being gradually provided in the conductive layer (110).

13. The method for forming a current collector according to claim 12, wherein the conductive layer (110) is formed by co-evaporating the first material (110a) and the second material (110b).

14. The method for forming a current collector according to claim 12 or 13, wherein the conductive layer (110) is formed by co-evaporating the first material with a decreasing intensity and the second material with an increasing intensity.

15. An apparatus (500) for forming a current collector (100) for an anode of an energy storage device (20), the apparatus comprising: a deposition arrangement (510) including a deposition conveyor (512) configured to convey a flexible substrate (101), a first material source (514a) having a first material (110a), and a second material source (514b) having a second material (110b) different from the first material, wherein the deposition arrangement (510) is configured to form a conductive layer (110) on a surface (101a, 101b) of the flexible substrate (101), and wherein the conductive layer (110) includes the first material (110a) and the second material (110b), the first and second materials being gradually provided in the conductive layer (110).