Method for employing stable self-assembled monolayers as release layers for lithium deposition and transfer onto a receiving substrate

Abstract

A method and apparatus for transferring metal layers using release layers is disclosed. In particular, implementations relate to methods using self-assembled monolayers as release layers to deposit and transfer lithium from polymer substrates to receiving substrates. In one implementation a method for transferring an alkali metal layer is provided. The method includes forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution. The method further includes depositing the alkali metal layer on the SAM disposed on the polymer substrate, and transferring the alkali metal layer from the polymer substrate to a receiving substrate.

Description

METHOD FOR EMPLOYING STABLE SELF-ASSEMBLED MONOLAYERS AS RELEASE LAYERS FOR LITHIUM DEPOSITION AND TRANSFER ONTO A RECEIVING SUBSTRATEBACKGROUNDField

[0001] Implementations of the present disclosure generally relate to processes for transferring metal layers using release layers. In particular, implementations relate to methods using self-assembled monolayers as release layers to deposit and transfer alkali metal layers from polymer substrates to receiving substrates.Description of the Related Art

[0002] Lithium metal layers play a vital role in the development of batteries in mobile devices, microelectronics and electric vehicles. For example, a typical Li-ion battery includes a positive electrode (cathode), a negative electrode (anode), an electrolyte to conduct ions, and a porous separator membrane to keep the electrodes physically apart. Some Li-ion batteries include a lithium layer to act as a pre-lithiation layer to protect an anode of the battery during the first cycle charge. Alternatively, a lithium layer can be used as an anode.

[0003] There is a need for methods and systems for the deposition and processing of alkali metals used in energy storage devices.SUMMARY

[0004] In one implementation a method for transferring an alkali metal layer is provided. The method includes forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution. The method further includes depositing the alkali metal layer on the SAM disposed on the polymer substrate, and transferring the alkali metal layer from the polymer substrate to a receiving substrate.

[0005] In another implementation, a method for transferring an alkali metal layer is provided. The method includes pre-treating a polymer substrate, and forming a self-assembled monolayer (SAM) on the polymer substrate, the SAM being formed using a SAM precursor in solution. The method further includes depositing the alkali metal layer on the SAM disposed on the polymer substrate, and transferring the alkali metal layer and the SAM from the polymer substrate to a receiving substrate.

[0006] In yet another implementation, a method for transferring an alkali metal layer is provided. The method includes forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution, and depositing the alkali metal layer on the SAM disposed on the polymer substrate. The method further includes transferring the alkali metal layer from the polymer substrate to a copper substrate forming an anode structure, wherein the SAM acts as a release layer and integrating the anode structure with a separator and cathode structure to form an energy storage device.

[0007] In yet another implementation a method for transferring a lithium layer is provided. The method includes forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution. The method further includes depositing the lithium layer on the SAM disposed on the polymer substrate, and transferring the lithium layer from the polymer substrate to a receiving substrate.

[0008] In yet another implementation, a method for transferring a lithium layer is provided. The method includes pre-treating a polymer substrate, and forming a self-assembled monolayer (SAM) on the polymer substrate, the SAM being formed using a SAM precursor in solution. The method further includes depositing the lithium layer on the SAM disposed on the polymer substrate, and transferring the lithium layer and the SAM from the polymer substrate to a receiving substrate.

[0009] In yet another implementation, a method for transferring a lithium layer is provided. The method includes forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution, and depositing the lithium layer on the SAM disposed on the polymer substrate. The method further includes transferring the lithium layer from the polymer substrate to a copper substrate forming an anode structure, wherein the SAM acts as a release layer and integrating the anode structure with a separator and cathode structure to form an energy storage device.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 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 implementations, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary implementations of the disclosure and are therefore not to be considered limiting of its scope, and may admit to other equally effective implementations.

[0011] Figure 1 is a flow diagram describing a method of transferring a lithium layer between substrates, according to some implementations.

[0012] Figure 2A-2D are views of various stages of manufacturing an energy storage device according to the method of Figure 1 , according to some implementations.

[0013] Figure 3 is a schematic of an energy storage device incorporating a receiving stack, according to some implementations.

[0014] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one implementation may be beneficially incorporated in other implementations without further recitation.DETAILED DESCRIPTION

[0015] The present disclosure generally relates to processes for transferring metal layers using release layers. In particular, implementations relate to methods using self-assembled monolayers as release layers to deposit and transfer alkali metals from polymer substrates to receiving substrates.

[0016] Lithium metal is an alkali metal and very reactive. Therefore, special conditions such as an inert gas atmosphere is needed to handle lithium and lithium needs to be transferred between substrates after deposition.

[0017] Transferring alkali metal layers, for example, lithium layers, onto substrates is used in microfabrication of microelectronic devices and energy storage devices. Methods of depositing and transferring lithium involve the use of release layers that are not stable under high temperature conditions or do not provide adequate adhesion between the lithium layers and substrates. This can result in poor lithium layer quality after transfer and other issues. A method of transferring lithium layers that can be completed at high temperature conditions and provide adequate lithium adhesion is described below. The method can be incorporated in a roll-to-rol I tool and used in a roll-to-roll process.

[0018] It is noted that while the particular substrate on which some implementations described herein can be practiced is not limited to particular substrates, it is particularly beneficial to practice the implementations on flexible substrates, including for example, web-based substrates, panels and discrete sheets. The flexible substrate can also be in the form of a foil, a film, or a thin plate.

[0019] The substrate can be or include plastic material, metallic material, metallized plastic or combinations thereof. Examples of suitable plastic materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), poly(methyl methacrylate) (PMMA), cellulose tri-acetate (TAC), polypropylene (PP), polyethylene (PE), polycarbonates (PC), bio degradable polymers such as Polyethylene 2,5-furandicarboxylate (PEF), multilayers thereof, or a combination thereof. Examples of suitable metallicmaterials include aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), stainless steel, clad materials, metallized plastic, paper, stainless steel, metal mesh, or a combination thereof.

[0020] It is also noted here that a flexible substrate or web as used within the implementations described herein can typically be characterized in that it is bendable. The term “web” can be synonymously used to the term “strip,” the term “flexible substrate,” or the term “flexible conductive substrate.” For example, the web as described in implementations herein can be a polymer material.

[0021] Substrate independent direct transfer (SIDT) is a method for forming electrode device stacks by transferring one or more layers including an alkali- metal layer, for example, a lithium metal layer, to a receiving substrate, for example, a current collector in implementations where lithium metal functions as an anode or for pre-lithiating an anode material which is already formed on the current collector. The alkali-metal includes an alkali-metal, for example, lithium metal, sodium, potassium, rubidium, cesium, francium, an alloy including the alkali-metal, or a combination thereof. The already formed anode material can include or be, but is not limited to, graphite, silicon, silicon graphite, silicon oxide graphite, silicon, tin, hard carbon, metal oxide, or combinations thereof. The alloy including the alkali metal can include an alloy of the alkali metal and the anode material. The current collector can include or be metalized plastic, copper, or combinations thereof. In SIDT processes, alkali-metal is formed over a carrier substrate composed of one or more materials such as a polymer substrate, for example, polyethylene terephthalate (PET), paper, or combinations thereof. The materials formed on the carrier substrate are directly transferred to a receiving substrate. The receiving substrate can include or be a current collector, a current collector having anode material formed thereover, a metallized plastic substrate, a separator, or a metallized plastic substrate having alkali-metal formed thereover. A release layer is formed between the alkali-metal layer and the carrier substrate. The release layer enables transferring the alkali metal and other materials from the carrier substrate to thereceiving substrate. The SIDT process of the disclosure is described in implementations of Figure 1.

[0022] Figure 1 is a flow diagram describing a method 100 of transferring a lithium layer between substrates. Figure 2A-2D are views of various stages of manufacturing an energy storage device according to the method 100 of Figure 1 . The method 100 describes forming a SIDT stack 250 on a polymer substrate 210 and then transferring the SIDT stack 250 to a receiving substrate 240 to form a receiving stack 270. Although Figures 2A-2D are described in relation to the method 100, it will be appreciated that the structures disclosed in Figures 2A-2D are not limited to the method 100, but instead may stand alone as structures independent of the method 100. Similarly, although the method 100 is described in relation to Figures 2A-2D, it will be appreciated that the method 100 is not limited to the structures disclosed in Figures 2A-2D but instead may stand alone independent of the structures disclosed in Figures 2A-2D. It should also be noted that although the method 100 illustrated in Figure 1 is described sequentially, other process sequences that include one or more operations that have been omitted and / or added, and / or have been rearranged in another desirable order, fall within the scope of the implementations of the disclosure provided herein.

[0023] Referring to Figure 2A, optionally, at operation 101 , the polymer substrate 210 is pre-treated. The polymer substrate 210 has a first surface 211 and a second surface 212. The second surface 212 is opposite the first surface 211. The polymer substrate 210 is the first layer in a flexible support layer stack 200. The polymer substrate 210 may comprise any suitable material that is compatible with the targeted processing conditions including a self-assembled monolayer (SAM) 220 to be formed. In one or more implementations, which can be combined with other implementations, the polymer substrate 210 can be or include, one or more layers selected from polymer materials. Example of suitable polymer materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polypropylene (PP), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyvinylidene fluoride(PVDF), polybenzoxazole (PBO), multilayers thereof, or a combination thereof. In one or more implementations, which can be combined with other implementations, the polymer substrate 210 is a web-based substrate.

[0024] In one or more implementations, which can be combined with other implementations, the polymer substrate 210 has a thickness in a range from about 5 micron to about 50 microns, or in a range from about 10 microns to about 50 microns, or in a range from about 25 microns to about 50 microns.

[0025] The pre-treatment of the polymer substrate 210 is a surface treatment process. The surface treatment process can be performed to remove contaminants (if present) from the first surface 211 of the polymer substrate 210 to activate the first surface 211 of the polymer substrate 210 for better bonding, attachment, or wetting by subsequently deposited material. The surface treatment process can be selected from a corona treatment process, an atmospheric plasma treatment process, a low energy plasma treatment process, a plasma treatment process performed in a vacuum environment, a chemical etching treatment process, a UV / Ozone treatment process, a surface activation treatment process or a combination thereof.

[0026] The surface treatment process can be performed under atmospheric conditions, near atmospheric conditions, or vacuum conditions. In one example the surface treatment process can be carried out in a vacuum environment with an environment of 1 x 10’2mbar to about 1 x 10’6mbar (e.g., 1 x 10’3or below; 1 x 10’4or below).

[0027] The surface treatment process can be a plasma treatment performed in an oxidizing gas environment, a reducing gas environment, or a combination of oxidizing and reducing gases. The plasma treatment can be performed under atmospheric conditions, near atmospheric conditions, or vacuum conditions. The oxidizing environment can include one or more oxidizing gases. The one or more oxidizing gases can be selected from oxygen (O2), ozone (O3), nitrous oxide (N2O), fluorine (F2), chlorine (CI2), carbon monoxide (CO), carbon dioxide (CO2), radicals thereof, derivatives thereof, or acombination thereof. In one implementations, the one or more oxidizing gases include oxygen (O2). The one or more oxidizing gases can be introduced with one or more inert gases, such as nitrogen, helium or argon. The reducing environment can include one or more reducing gases. The reducing gases can be selected from ammonia (NH3), hydrazine (N2H4), hydrogen (H2), NF3, atomic hydrogen, radicals thereof, derivatives thereof, or a combination thereof. In one example, the one or more reducing gases includes hydrogen. The one or more reducing gases can be introduced with one or more inert gases, such as nitrogen, helium or argon.

[0028] In some implementations, the surface treatment process is a plasma treatment process performed in a vacuum environment. The plasma treatment process can include exposing the electrode structure to a reducing plasma. The reducing plasma can be formed from a reducing gas mixture comprising ammonia (NH3), hydrazine (N2H4), hydrogen (H2), atomic hydrogen, radicals thereof, derivatives thereof, or a combination thereof. The reducing gas mixture can further include one or more inert gases. The reducing plasma can be a remotely formed plasma, a capacitively coupled plasma, or an inductively coupled plasma. The plasma treatment process can include exposing the electrode structure to an oxidizing plasma. The oxidizing plasma can be formed from an oxidizing gas mixture comprises oxygen (O2), ozone (O3), nitrous oxide (N2O), fluorine (F2), chlorine (CI2), carbon monoxide (CO), carbon dioxide (CO2), radicals thereof, derivatives thereof, or a combination thereof. The oxidizing gas mixture can further include one or more inert gases. The oxidizing plasma can be a remotely formed plasma, a capacitively coupled plasma, or an inductively coupled plasma.

[0029] The surface treatment process can be a corona treatment (e.g., an air plasma treatment) used to modify the surface of the electrode structure. The corona treatment can be performed using a low temperature corona discharge plasma to impart changes to the surface energy of the electrode structure. The corona treatment discharge process includes generating an ionized coronadischarge plasma. The generated corona discharge plasma can include a positive or negatively charged plasma.

[0030] Corona discharge usually involves two asymmetric electrodes positioned in a processing region; one highly curved, e.g., a needle tip or a small diameter wire, and one of low curvature, e.g., a plate, or a ground. The high curvature ensures a high potential around the electrode, providing for the generation of a plasma. If the geometry and gradient are such that the ionized region continues to grow instead of stopping at a certain radius, a completely conductive path may be formed, resulting in a momentary spark or a continuous arc.

[0031] In some implementations, the corona is positive. In other implementations, the corona is negative. This is determined by the polarity of the voltage on the highly-curved electrode. If the curved electrode is positive with respect to the flat electrode a positive corona exists; otherwise the corona is negative. In some implementations, the corona treatment is carried out in part under atmospheric or partial pressure, under vacuum, or a combination thereof.

[0032] In some implementations, the surface treatment process is the chemical etching treatment process. The chemical etching treatment process includes treating the first surface 211 , the second surface 212, or both the first surface 211 and the second surface 212 of the polymer substrate 210 with suitable etchants or chemical solutions to create microscale roughness and functional groups on the surfaces. The chemical etching treatment process enhances surface adhesion and promotes SAM formation. In some implementations, the surface treatment process is the UV / Ozone treatment process. The UV / Ozone treatment process exposes the polymer substrate 210 to UV light or ozone. The UV light and ozone modifies surface chemistry of the polymer substrate 210 improving wettability and aiding in SAM adhesion. In some implementations, the surface treatment process is the surface activation treatment process. The surface activation treatment process uses silanecoupling agents. Silane coupling agents chemically bond to the first surface 211 and provide reactive groups for subsequent SAM attachment.

[0033] Referring to Figure 2B, at operation 103 the self-assembled monolayer (SAM) 220 is formed. The SAM 220 is formed on the polymer substrate 210 of the flexible support layer stack 200. SAM refers to a layer of molecules that are attached (e.g., by chemical bond) to a surface and that have adopted a preferred orientation with respect to that surface and even with respect to each other. SAMs are organic thin films. In one or more implementations, the SAM 220 includes an organized layer of amphiphilic molecules in which one end of the molecule, the “head group” shows a specific, reversible affinity for a substrate such as the polymer substrate 210. Selection of the head group will depend on the application of the SAM 220. The head group is connected to an alkyl chain in which a tail or “terminal end” can be functionalized, for example, to vary wetting and interfacial properties. The tail is selected to show affinity to alkali metals such as lithium. SAM precursors that form the SAM will selectively attach to one material over another material (e.g. metal vs. polymer.) The SAM precursors are discussed below.

[0034] The SAM 220 has a first surface 221 corresponding to the tail and a second surface 222 corresponding to the head group. The second surface 222 is disposed on the first surface 211 of the polymer substrate 210. The head group bonds the first surface 211 of the polymer substrate 210 using chemisorption. Chemisorption occurs through a reaction between the head groups on the SAM and the surface atoms of the polymer substrate 210.

[0035] SAMs can be tailored for specific applications by choosing the appropriate molecular structure and functional groups. The molecular structure of SAMs can be varied by changing the length and branching of the hydrocarbon chain, the nature of the tail group, and the presence of functional groups such as carboxylic acids, amines, and hydroxyl groups. In one or more implementations, which can be combined with other implementations, SAM 220 has a thickness in a range between 1 nm and 15 nm, or in a range between 1 nm and 10 nm, or in a range between 3 nm and 10 nm, or in a range between4 nm and 7 nm. The thickness can be controlled by the concentration and incubation time of the SAM precursor solution.

[0036] The SAM 220 is formed on the polymer substrate 210 from a SAM precursor. The SAM precursors include alkyltrichlorosilanes, fluoroalkylsilanes, dithiocarbamates, and phosphonic acids. Alkyltrichlorosilane reacts with the first surface 211 of polymer substrate 210 to form an alkyltrichlorosilane SAM. Alkyltrichlorosilane SAMs are stable under high temperature conditions and can provide good adhesion to both lithium and copper. Fluoroalkylsilane reacts with the first surface 211 of the polymer substrate 210 to form a fluoroalkylsilane SAM. Fluoroalkylsilane SAMs are highly hydrophobic. Fluoroalkylsilane SAMs are stable under high temperature conditions and provide good adhesion to both lithium and copper. Dithiocarbamate reacts with the first surface 211 of the polymer substrate 210 to form a dithiocarbamate SAM. Dithiocarbamate SAMs are stable under high temperature conditions and provide good adhesion to both lithium and copper. Phosphonic acid reacts with the first surface 211 of the polymer substrate 210 to form a phosphonic acid SAM. Phosphonic acid SAMs are stable under high temperature conditions and provide good adhesion to both lithium and copper.

[0037] Examples of phosphonic acid materials include methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, butylphosphonic acid, pentylphosphonic acid, hexylphosphonic acid, heptylphosphonic acid, octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, undecylphosphonic acid, dodecylphosphonic acid, tridecylphosphonic acid, tetradecylphosphonic acid, pentadecylphosphonic acid, hexadecylphosphonic acid, heptadecylphosphonic acid, octadecylphosphonic acid, nonadecylphosphonic acid, or a combination thereof.

[0038] In one or more implementations, the SAM precursors may be amino oxysilane materials, such as (3-Aminopropyl)triethyoxysilane (“APTES”). APTES is a silane-based compound that contains a reactive amino group that can react with the hydroxyl groups on the first surface 211 on the polymer substrate 210 to form covalent bonds. APTES forms a stable SAM 220.

[0039] Examples of other SAM precursors, which may be utilized depending on the specific chemistry involved, include the precursors described hereinafter, including combinations, mixtures, and grafts thereof, in addition to other SAM precursors having characteristics suitable for blocking deposition of subsequently deposited materials in a semiconductor fabrication process. In one implementation, the SAM precursors may be carboxylic acid materials, such as methylcarboxylic acids, ethylcarboxylic acids, propylcarboxylic acids, butylcarboxylic acids, pentylcarboxylic acids, hexylcarboxylic acids, heptylcarboxylic acids, octylcarboxylic acids, nonylcarboxylic acids, decylcarboxylic acids, undecylcarboxylic acids, dodecylcarboxylic acids, tridecylcarboxylic acids, tetradecylcarboxylic acids, pentadecylcarboxylic acids, hexadecylcarboxylic acids, heptadecylcarboxylic acids, octadecylcarboxylic acids, nonadecylcarboxylic acids, or a combination thereof.

[0040] In another implementation, the SAM precursors may be thiol materials, such as methanethiol, ethanethiol, propanethiol, butanethiol, pentanethiol, hexanethiol, heptanethiol, octanethiol, nonanethiol, decanethiol, undecanethiol, dodecanethiol, tridecanethiol, tetradecanethiol, pentadecanethiol, hexadecanethiol, heptadecanethiol, octadecanethiol, nonadecanethiol, or a combination thereof.

[0041] In another implementation, the SAM precursors may be silylamine materials, such as bis(diethylamino)silane (“BDEAS”), tris(dimethylamino)methylsilane, tris(dimethylamino)ethylsilane, tris(dimethylamino)propylsilane, tris(dimethylamino)butylsilane, tris(dimethylamino)pentylsilane, tris(dimethylamino)hexylsilane, tris(dimethylamino)heptylsilane, tris(dimethylamino)octylsilane, tris(dimethylamino)nonylsilane, tris(dimethylamino)decylsilane, tris(dimethylamino)undecylsilane tris(dimethylamino)dodecylsilane, tris(dimethylamino)tridecylsilane, tris(dimethylamino)tetradecylsilane, tris(dimethylamino)pentadecylsilane, tris(dimethylamino)hexadecylsilane, tris(dimethylamino)heptadecylsilane, tris(dimethylamino)octadecylsilane, tris(dimethylamino)nonadecylsilane, or a combination thereof.

[0042] In another implementation, the SAM precursors may be chlorosilane materials, such as hexachlorodisilane (“HCDS”), methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, butyltrichlorosilane pentyltrichlorosilane, hexyltrichlorosilane, heptyltrichlorosilane octyltrichlorosilane, nonyltrichlorosilane, decyltrichlorosilane undecyltrichlorosilane, dodecyltrichlorosilane, tridecyltrichlorosilane tetradecyltrichlorosilane, pentadecyltrichlorosilane, hexadecyltrichlorosilane heptadecyltrichlorosilane, octadecyltrichlorosilane (“OTS”), nonadecyltrichlorosilane, or a combination thereof.

[0043] In another implementation, the SAM precursors may be oxysilane materials, such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane pentyltrimethoxysilane, pentyltriethoxysilane, hexyltrimethoxysilane hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane octyltrimethoxysilane, octyltriethoxysilane, nonyltrimethoxysilane nonyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane undecyltrimethoxysilane, undecyltrethoxysilane, dodecyltrimethoxysilane dodecyltriethoxysilane, tridecyltrimethoxysilane, tridecyltriethoxysilane tetradecyltrimethoxysilane, tetradecyltriethoxysilane pentadecyltrimethoxysilane, pentadecyltriethoxysilane hexadecyltrimethoxysilane, hexadecyltroethoxysilane heptadecyltrimethoxysilane, heptadecyltriethoxysilane octadecyltrimethoxylsilane octadecyltriethoxysilane nonadecyltrimethoxysilane, nonadecyltriethoxysilane, or a combination thereof.

[0044] In another implementation, the SAM precursors may have a fluorinated R group, such as (1 ,1 ,2,2-perfluorodecyl)trichlorosilane, trichloro(1 ,1 ,2,2-perflrorooctyl)silane, (trideca-fluoro-1 ,1 ,2,2- tetrahydrooctyl)trichlorosilane, (tridecafluoro-1 ,1 ,2,2-tetrahydro- octyl)triethoxysilane, (tridecafluoro-1 , 1 ,2,2- tetrahydrooctyl)methyldichlorosilane, (tridecafluoro-1 , 1 ,2,2-tetrahydrooctyl)dimethylchlorosilane, and (heptadecafluoro-1 ,1 ,2,2- tetrahydrodecyl)trichlorosilane, among others. It is contemplated that combinations and mixtures of the aforementioned materials are within the scope of this disclosure.

[0045] In another implementation, the SAM precursors are selected from the group comprising bis(diethylamino)silane (“BDEAS”), hexachlorodisilane (HCDS), (3-Aminopropyl)triethoxysilane (“APTES”), and octadecyltrichlorosilane (“OTS”).

[0046] The formation of the SAM 220 may include immersion, spin-coating, or spray-coating. Immersion includes the polymer substrate 210 being immersed in a dilute solution of the SAM precursor. After the immersion, the polymer substrate 210 is rinsed with a solvent and dried. Immersion is relatively easy to scale up and can provide good control over the thickness and uniformity of the SAM 220.

[0047] When APTES is used as the SAM precursor, it may be dissolved in ethanol or water and immersion or spin-coating is used. The SAM 220 made from APTES is typically cured at a high temperature to promote cross-linking and ensure stability.

[0048] Spin-coating includes a solution containing the SAM precursors being dispensed onto the polymer substrate 210, which is then spun at a high speed to create a uniform layer. The excess solution is then removed by spinning the polymer substrate 210 again. Spin-coating can provide good control over the thickness and uniformity of the SAM 220.

[0049] Spray-coating includes spraying a solution containing the SAMs precursors onto the polymer substrate 210 using a spray nozzle. The polymer substrate 210 is then heated to initiate the self-assembly process. Spraycoating can provide good control over the thickness and uniformity of the SAM layer.

[0050] Referring to Figure 2C, at operation 105 an alkali metal layer 230, for example, a lithium layer is deposited. The alkali metal layer 230 is disposed on the SAM 220. The lithium layer has a first surface 231 and a second surface 232. The second surface 232 of the alkali metal layer 230 is deposited on the first surface 221 of the SAM 220. The lithium layer may be deposited under vacuum. The alkali metal layer 230 may be deposited via a physical vapor deposition process, for example, an evaporation process or a sputtering process. The evaporation process may be an electron beam evaporation process or a thermal evaporation process. The alkali metal layer 230 completes the flexible support layer stack 200. The flexible support layer stack 200 includes the SIDT stack 250 and the polymer substrate 210. The SIDT stack 250 includes the alkali metal layer 230 and in some implementations the SAM 220.

[0051] The SIDT stacks described herein are formed such that the alkali metal layer 230 is deposited last on the flexible support layer stack 200. Depositing the lithium layer last enables forming the film stack without damaging the lithium layer, which typically has a lower melting point relative to other materials that are formed in an energy storage device. Conventional methods of forming energy storage devices include direct deposition of molten lithium onto the current collector in lithium metal anode formation or onto the anode material in pre-lithiation implementations. These methods further include maintaining the underlying substrate as the alkali metal layer 230 is formed to prevent damage to the lithium. In contrast, the flexible support layer stack 200 and methods described herein, enable forming the alkali metal layer 230 last prior to transferring the SIDT stack 250 to the receiving substrate 240 during operation 107.

[0052] Referring to Figure 2D, at operation 107, the alkali metal layer 230 is transferred. The alkali metal layer 230 is transferred from the polymer substrate 210 to the receiving substrate 240. The receiving substrate 240 has a first surface 241 and a second surface 242. In one or more implementations, which can be combined with other implementations, the receiving substrate 240includes or is a web-based substrate. The first surface 241 and the second surface 242 oppose each other on the receiving substrate 240. The first surface 231 of the alkali metal layer 230 attaches to the second surface 242 of the receiving substrate 240. The SAM 220 acts as a release layer, releasing the alkali metal layer 230 from the polymer substrate 210 as the alkali metal layer 230 is transferred to the receiving substrate 240 forming a receiving stack 270. The receiving stack 270 may be used in microelectronic devices or energy storage devices.

[0053] In some implementations, when forming a battery and where pre- lithiation is involved, an anode material may already be formed over the receiving substrate 240 and the alkali metal layer 230 contacts the anode material formed over the receiving substrate 240. In other implementations, the alkali metal layer 230 is the anode. The receiving substrate 240 formed of a polymer material, a metallic material, or a combination of a polymer material and a metallic material, for example, metallized plastic. The receiving substrate 240 may be or include flexible film, such as a CPP film (i.e., a casting polypropylene film), an OPP film (i.e., an oriented polypropylene film), or a PET film (i.e., a polyethylene terephthalate film). Alternatively, the flexible substrate may be a pre-coated paper, a polypropylene (PP) film, a PEN film, a polylactic acid (PLA) film, or a PVC film. The receiving substrate 240 can be or include one or more current collectors, which can include aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), stainless steel, clad materials, alloys thereof, and a combination thereof. In particular implementations, the receiving substrate 240 can be a copper substrate or include copper.

[0054] In one or more implementations, which can be combined with other implementations, during operation 107 the SAM 220 is transferred or partially transferred with the alkali metal layer 230 to a receiving substrate as is shown in Figure 2D. Alternatively, in other implementations, the SAM 220 remains or partially remains on the polymer substrate 210 after operation 107.

[0055] At operation 109, the receiving stack 270 is optionally integrated with a separator 310, a cathode structure 320, or both the separator 310 and the cathode structure to form an energy storage device 300. Figure 3 is a schematic view of the energy storage device 300 incorporating the receiving stack 270. The energy storage device 300 includes the receiving stack 270 acting as an anode structure. The alkali metal layer 230 disposed upon the receiving substrate 240 acts as an anode. The receiving substrate 240 acts as an anode current collector. Optionally, the SAM 220 is disposed upon the alkali metal layer 230 and acts as a protective layer.

[0056] The separator 310 may include, a microporous polymeric separator including a polyolefin, by way of non-limiting example. The polyolefin may be a homopolymer (derived from a single monomer constituent) or a heteropolymer (derived from more than one monomer constituent), which may be either linear or branched. If a heteropolymer is derived from two monomer constituents, the polyolefin may assume any copolymer chain arrangement, including those of a block copolymer or a random copolymer. Similarly, if the polyolefin is a heteropolymer derived from more than two monomer constituents, it may likewise be a block copolymer or a random copolymer. In certain implementations, the polyolefin may be polyethylene (PE), polypropylene (PP), or a blend of PE and PP, or multi-layered structured porous films of PE and / or PP. Commercially available polyolefin porous membranes include CELGARD® 2500 (a monolayer polypropylene separator) and CELGARD® 2320 (a tri-layer polypropylene / polyethylene / polypropylene separator) available from Celgard LLC.

[0057] In one or more implementations, which can be combined with other implementations, the cathode structure 320 includes a cathode current collector 325 and cathode 330. The cathode current collector 325 may be or include any of the flexible films described or any of aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), tin (Sn), silicon (Si), manganese (Mn), magnesium (Mg), alloys thereof, and combinations thereof. The cathode current collector 325 may be or include any of aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni),cobalt (Co), tin (Sn), silicon (Si), manganese (Mn), magnesium (Mg), alloys thereof, and combinations thereof. In particular implementations, the cathode current collector 325 may be or include aluminum.

[0058] The cathode 330 may be or include any suitable cathode material. The cathode 330 may be or include any material compatible with the anode and may include an intercalation compound, an insertion compound, or an electrochemically active polymer. Suitable intercalation materials include, for example, sulfur, lithium-containing metal oxides, M0S2, FeS2, MnO2, TiS2, NbSes, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, VeO and V2O5. Suitable polymers include, for example, polyacetylene, polypyrrole, polyaniline, and polythiophene. In some implementations the cathode 330 includes a polymer binder material as described herein. The cathode 330 or cathode may be or include a layered oxide, such as lithium cobalt oxide, an olivine, such as lithium iron phosphate, or a spinel, such as lithium manganese oxide. Examples of lithium-containing oxides may be layered, such as lithium cobalt oxide (LiCoC ), or mixed metal oxides, such as LiNixCoi-2xMnO2, LiNiMnCoC (“NMC”), LiNio.5Mm.5O4, Li(Nio.8Coo.i5Alo.o5)02, LiMn2O4, and doped lithium rich layeredlayered materials, wherein x is zero or a non-zero number. Examples of phosphates may be or include iron olivine (LiFePO4) and its variants (such as LiFe(i-x)MgxPO4), LiMoPO4, LiCoPO4, LiNiPO4, Li3V2(PO4)3, LiVOPO4, LiMP2O7, or LiFei.5P2O7, wherein x is zero or a non-zero number. Examples of fluorophosphates may be or include LiVPO4F, LiAIPO4F, Li5V(PO4)2F2jLi5Cr(PO4)2F2jLi2CoPO4F, or Li2NiPO4F. Example of silicates may be or include Li2FeSiO4, Li2MnSiO4, or Li2VOSiO4. Examples of non-lithium compounds may be or include Na5V2(PO4)2F3.

[0059] The previously described implementations of the present disclosure have many advantages. However, the present disclosure does not require that all the advantageous features and all the advantages need to be incorporated into every implementation of the present disclosure. In summation, SAMs may be used as release layers for transferring alkali metal layers onto receiving substrates. SAMs provide a simple and effective method for achieving high-performance alkali metal transfer processes. The SAMs described herein have been shown to be stable under high-temperature conditions and can provide excellent adhesion between the alkali metal layer and the receiving substrate. The SAM precursors may be selected for cost effectiveness and the particular chemistries of the receiving substrate and polymer substrate. The receiving stack can function as an anode structure for an energy storage device.

[0060] While the foregoing is directed to implementations of the present disclosure, other and further implementations of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:1 . A method for transferring an alkali metal layer, comprising: forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution; depositing the alkali metal layer on the SAM disposed on the polymer substrate; and transferring the alkali metal layer from the polymer substrate to a receiving substrate.

2. The method of claim 1 , wherein the SAM precursor is selected from a group including alkyltrichlorosilanes, fluoroalkylsilanes, dithiocarbamates, and phosphonic acids.

3. The method of claim 1 , wherein the SAM has a thickness between 3 nm and 10 nm.

4. The method of claim 1 , wherein the receiving substrate comprises a metal.

5. The method of claim 4, wherein the metal of the receiving substrate is copper.

6. The method of claim 1 , wherein the alkali metal layer is deposited by a thermal evaporation process.

7. The method of claim 1 , wherein the polymer substrate comprises polyethylene terephthalate (PET).

8. The method of claim 1 , wherein the lithium layer on the receiving substrate is used in microelectronic devices or energy storage devices.

9. The method of claim 1 wherein the SAM is formed on the polymer substrate by immersion, spin-coating, or spray-coating.

10. A method for transferring a lithium layer, comprising: pre-treating a polymer substrate; forming a self-assembled monolayer (SAM) on the polymer substrate, the SAM being formed using a SAM precursor in solution; depositing the lithium layer on the SAM disposed on the polymer substrate; and transferring the lithium layer and the SAM from the polymer substrate to a receiving substrate.11 . The method of claim 10, wherein the SAM precursor is selected from a group including alkyltrichlorosilanes, fluoroalkylsilanes, dithiocarbamates, and phosphonic acids.

12. The method of claim 10, wherein the SAM has a thickness between 3 nm and 10 nm.

13. The method of claim 10, wherein the receiving substrate is copper.

14. The method of claim 10, wherein the lithium layer is deposited by a thermal evaporation process.

15. The method of claim 10, wherein the polymer substrate comprises polyethylene terephthalate (PET).

16. The method of claim 10, wherein the lithium layer on the receiving substrate is used in microelectronic devices or energy storage devices.

17. A method for transferring a lithium layer, comprising: forming a self-assembled monolayer (SAM) on a polymer substrate, the SAM being formed using a SAM precursor in solution;depositing the lithium layer on the SAM disposed on the polymer substrate; transferring the lithium layer from the polymer substrate to a copper substrate forming an anode structure, wherein the SAM acts as a release layer; and integrating the anode structure with a separator and cathode structure to form an energy storage device.

18. The method of claim 17, wherein the SAM has a thickness between 3 nm and 10 nm.

19. The method of claim 17, wherein the polymer substrate comprises polyethylene terephthalate (PET).

20. The method of claim 17, wherein the lithium layer on the copper substrate is used in microelectronic devices or energy storage devices.

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