Lithium alloy anode with compensation for lithiation-induced volume change

Abstract

A method for forming an alloy film stack is provided. The method includes disposing solutes on a flexible substrate stack and laminating a lithium metal containing layer formed on a flexible support layer stack to the solutes on the flexible substrate stack. The method also includes exposing portions of the lithium metal containing layer to laser energy to create a void volume between the lithium metal containing layer and the flexible support layer stack, and transferring the exposed portions of the lithium metal containing layer from the flexible support layer stack to the flexible substrate stack. The exposure of the lithium metal containing layer to the laser energy in turn also causes a reaction between the lithium metal containing layer and the solute layer on the flexible substrate stack to form an alloy material.

Description

Attorney Docket No.: E165-0161PCTLITHIUM ALLOY ANODE WITH COMPENSATION FOR LITHIATION-INDUCED VOLUME CHANGEBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to metal electrodes, more specifically lithium-containing anodes, high performance electrochemical devices, such as primary and secondary electrochemical devices, including the aforementioned lithium-containing electrodes, and methods for fabricating the same.Description of the Related Art

[0002] Battery technologies, including 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 electric vehicles (EVs), 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, have too much weight, and are often inadequately cycleable for these growing applications. Lithium- ion batteries, however, are thought to have the best chance.

[0003] Typically, lithium-ion batteries do not contain solid metallic lithium anodes for safety reasons but instead use a graphitic material containing lithium or silicon- blended graphite as the anode. However, lithium alloy anodes have the advantage of high energy density compared to graphite or graphite-silicon anodes. Although silicon blended graphite anodes have higher energy density than graphite anodes, silicon blended graphite anodes suffer from first cycle capacity loss. Lithium metal undergoes a significant volume change during lithiation and delithiation, which can cause stress and strain on the anode and lead to failure. This unwanted volumetric expansion of the lithium metal in anode results in it being challenging to produce battery cells with lithium metal and lithium alloy anodes. Thus, there is a need for improved methods for forming lithium metal and lithium alloy anodes for energy storage devices.Attorney Docket No.: E165-0161PCTSUMMARY

[0004] In one embodiment, a method for forming an alloy film stack is provided. The method includes disposing solutes on a flexible substrate stack, the flexible substrate stack comprising a current collector, and laminating a lithium metal containing layer to the solutes on the flexible substrate stack. The lithium metal containing layer is formed on a polymer substrate of a flexible support layer stack. The method also includes exposing portions of the lithium metal containing layer to laser energy to create a void volume between the lithium metal containing layer and the flexible support layer stack, and transferring the exposed portions of the lithium metal containing layer from the flexible support layer stack to the flexible substrate stack. The exposure of the lithium metal containing layer to the laser energy in turn also causes a reaction between the lithium metal containing layer and the solute layer on the flexible substrate stack.

[0005] In another embodiment, a method for forming an alloy film stack is provided. The method includes forming a lithium metal layer on a flexible substrate stack and laminating a solute layer to the lithium metal layer. The solute layer is formed on a polymer substrate of a flexible solute support stack. The method also includes separating the solute layer from the flexible solute support stack to transfer the solute layer to the flexible substrate stack, and laminating a lithium metal containing layer to the solute layer. The lithium metal containing layer is formed on a polymer substrate of a flexible support layer stack. The method also includes exposing portions of the lithium metal containing layer to laser energy to create a void volume between the lithium metal containing layer and the flexible support layer stack, and separating the lithium metal containing layer from the flexible support layer stack to transfer the exposed portions of the lithium metal containing layer to the flexible substrate stack. The exposure of the lithium metal containing layer to the laser energy in turn also causes a reaction between the lithium metal containing layer and the solute layer on the flexible substrate stack.

[0006] In an embodiment, a film stack is provided. The film stack includes a flexible substrate stack, and a lithium alloy layer formed over the flexible substrate stack. A plurality of voids is formed in a top surface of the lithium alloy layer. The lithium alloy layer is formed from a reaction between a solute layer on the flexible substrate stackAttorney Docket No.: E165-0161PCT and a lithium metal containing layer transferred to the flexible substrate stack from a flexible support layer stack using a laser lift-off process.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] 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, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0008] FIG. 1 illustrates a flowchart showing a method of forming an anode film stack, in accordance with one or more embodiments of the present disclosure.

[0009] FIGS. 2A-2H illustrate views of various stages of manufacturing an anode film stack according to the method of FIG. 1 , in accordance with one or more embodiments of the present disclosure.

[0010] FIG. 3 illustrates a flowchart showing showing another method of forming an anode film stack, in accordance with one or more embodiments of the present disclosure.

[0011] FIGS. 4A-4H illustrate views of various stages of manufacturing an anode film stack according to the method of FIG. 3, in accordance with one or more embodiments of the present disclosure.

[0012] FIGS. 5A and 5B illustrates schematic top and side view of an anode film stack formed using techniques of the present disclosure, in accordance with one or more embodiments of the present disclosure.

[0013] 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 embodiment may be beneficially incorporated in other embodiments without further recitation.Attorney Docket No.: E165-0161PCTDETAILED DESCRIPTION

[0014] The following disclosure describes anode electrodes, high performance electrochemical cells and batteries including the aforementioned anode electrodes, and methods for fabricating the same. Certain details are set forth in the following description and figures to provide a thorough understanding of various embodiments of the disclosure. Other details describing well-known structures and systems often associated with electrochemical cells and batteries are not set forth in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments.

[0015] Many of the details, dimensions, angles and other features shown in the Figures are merely illustrative of particular embodiments. Accordingly, other embodiments can have other details, components, dimensions, angles and features without departing from the spirit or scope of the present disclosure. In addition, further embodiments of the disclosure can be practiced without several of the details described below.

[0016] Energy storage devices, for example, Li-ion batteries, typically include a positive electrode (e.g., cathode), and a negative electrode separated by a polymer separator with a liquid electrolyte. Solid-state batteries also typically include a positive electrode (e.g., cathode) and a negative electrode (e.g., anode) but replace both the polymer separator and the liquid electrolyte with an ion-conducting material.

[0017] Energy storage devices, for example, Li-ion batteries, typically include a positive electrode (e.g., cathode), and a negative electrode separated by a polymer separator with a liquid electrolyte. Solid-state batteries also typically include a positive electrode (e.g., cathode) and a negative electrode (e.g., anode) but replace both the polymer separator and the liquid electrolyte with an ion-conducting material.

[0018] Graphite anodes are the current state of the art but the industry is moving from the graphite based anode to silicon blended graphite anodes to increase cell energy density. However, silicon blended graphite anodes often suffer from irreversible capacity loss that occurs during the first cycle. Thus, the ability to use lithium in next generation batteries including both Li-ion batteries and solid-state batteries becomes increasingly substantial. However, lithium technology presentsAttorney Docket No.: E165-0161PCT significant device integration challenges such as unwanted volumetric expansion during charging and discharging which in turn can make it difficult to produce cells and batteries, as well as reduce the battery life of the resulting lithium-ion battery formed.

[0019] Using the embodiments described herein, a 3D patterned lithium alloy anode having a plurality of cavities or cells can be formed in a lithium alloy anode stack to mitigate volume change by the lithium alloy layer in the anode cell. In one or more embodiments, which can be combined with other embodiments, the lithium alloy anode is formed by a chemical reaction resulting from the formation of a lithium-solute- lithium stack layer after patterned lithium is transferred onto a substrate stack by exposure to one or more lasers. In one or more embodiments, which can be combined with other embodiments, an IR fiber laser can be used in a laser activation process, such as a laser lift-off (LLO) process for patterned Li transfer from a flexible layer stack onto the substrate stack. For example, the I laser can be used activate PET-Li interface from the PET side and transfer a patterned lithium metal layer onto the substrate stack.

[0020] In one or more embodiments, which can be combined with other embodiments, the laser lift-off process can use a laser source to create an interface reaction with either a release layer, an interface layer, or both the release layer and the interface layer between the alkali metal or alloy layer and the flexible support layer, for example, PET, to (a) form an SEI layer in the electrode structure post-SIDT and / or (b) a Li surface protection layer for easy handling / shipping and integration of Li films in manufacturing environment.

[0021] In one or more embodiments, which can be combined with other embodiments, the laser lift-off process can use a laser source to create an interface reaction with a solute layer on the substrate stack, such as a solute layer between the patterned lithium metal layer and the substrate stack after the lithium metal layer is transferred by the laser lift-off process. In one or more embodiments, which can be combined with other embodiments, the interface reaction between the solute layer and the patterned lithium metal layer causes the two layers to form a patterned lithium alloy layer. For example, in one or more embodiments, which can be combined with other embodiments, a Li-compatible solute layer such as a silicon layer is formed onAttorney Docket No.: E165-0161PCT the substrate stack and exposed to the laser during the patterned lithium transfer. Due to the high reactivity of lithium, exposure of the lithium metal layer in contact with the silicon layer to the laser during the patterned lithium transfer results in the formation of a patterned Li-Si alloy layer on the substrate stack after the patterned lithium transfer.

[0022] In one or more embodiments, which can be combined with other embodiments, the laser lift-off process can be incorporated into a roll-to-roll tool and used in a roll-to-roll process. The laser lift-off process enables transfer of patterned lithium from a flexible substrate onto a roll-to-roll battery anode substrate by exposing an interface between the alkali metal (i.e. lithium metal) and the flexible support layer stack, for example, the Li-PET interface, to a laser which induces lithium transfer at the interface.

[0023] In one or more embodiments, which can be combined with other embodiments, the laser lift-off process enables the patterning of lithium. For example, the lithium can be patterned to match the pattern of the anode material in a pre- lithiation process, such as lane coating, skip coating, and also directly onto a current collector. Any suitable pattern may be achieved, for example, a square, a triangle, a circle, etc.

[0024] In one or more embodiments, which can be combined with other embodiments, a flexible support layer stack is provided. The flexible support layer stack can include a plastic containing substrate, for example, a polyethylene terephthalate (PET) substrate. The flexible support layer stack can further include a release layer, for example, silicone or other deposited release layers, formed on the flexible support layer stack. An alkali metal-containing layer, for example, an alkali metal such as lithium metal is formed over the flexible support layer stack. In embodiments where the release layer is not present, the lithium metal layer can be formed directly on the plastic containing substrate. In embodiments where the release layer is present, the lithium metal layer can be formed directly on the release layer.

[0025] The flexible support layer stack having the lithium metal layer formed thereon is exposed to a laser lift-off process. In one or more embodiments, during the laser lift-off process, a laser is directed through the flexible support layer stack toAttorney Docket No.: E165-0161PCT activate the interface of the lithium metal layer and the flexible support layer stack, for example, the Li-PET interface. The laser can be directed through the backside of the flexible support layer stack, for example, from the plastic containing substrate or PET side. Exposure to the laser can induce a lithium transfer process creating a void volume in the lithium metal layer at the Li-PET interface between the lithium metal layer and the flexible support layer. This void volume can make separation of the lithium metal layer from the flexible support layer easier during transfer of the lithium metal layer from the flexible support layer stack to the current collector. In addition, precise laser beam position control enables the selective transfer of alkali metal into desired shapes from the flexible support layer stack to the substrate stack to form anode device stacks with various shapes. Further, exposure to the laser can be used to pattern the lithium metal layer such that a precise pattern of alkali metal is transferred from the flexible support layer stack to the substrate stack to form a lithium metal anode device stack. A cathode structure and / or separator can be integrated with the formed lithium metal anode device stack to form the energy storage device.

[0026] In one or more embodiments, which can be combined with other embodiments, the laser lift-off process and the compatible solute layer on the substrate stack provides for forming a patterned lithium alloy layer on the substrate stack after the patterned lithium transfer. When the laser lift-off process causes the patterned lithium metal layer and the solute layer to form the patterned lithium alloy layer, the void volume formed in the lithium metal layer by the laser lift-off process in turn forms a plurality of voids in a top surface of the patterned lithium alloy layer. The voids in the patterned lithium alloy layer provide an internal void space that allows for mechanical expansion of the lithium alloy material. The void volume accommodates for the volume expansion of the core particle therewithin. Thus, the structure of the patterned lithium alloy layer provides a buffer matrix in which the void volume minimizes mechanical degradation of the core material during lithiation and delithiation which in turn results in increased cycle life and capacity retention.

[0027] It is noted that while the particular substrate on which some embodiments described herein can be practiced is not limited, it is particularly beneficial to practice the embodiments on flexible substrates, including for example, web-based substrates,Attorney Docket No.: E165-0161PCT panels and discrete sheets. The flexible substrate can also be in the form of a foil, a polymer film, or a thin plate.

[0028] It is also noted here that a flexible substrate or web as used within the embodiments 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 embodiments herein can be a polymer material.

[0029] It is further noted that the methods and systems described may be used in forming single-sided electrode structures and double-sided electrode structures.

[0030] FIG. 1 illustrates a flow chart of a method 100 for manufacturing an anode film stack 200 in accordance with one or more embodiments of the present disclosure. FIGS. 2A-2G illustrate views of various stages of manufacturing the anode film stack 200 in accordance with one or more embodiments of the present disclosure. Although FIGS. 2A-2G are described in relation to the method 100, it will be appreciated that the structures disclosed in FIGS. 2A-2G 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 FIGS. 2A-2G, it will be appreciated that the method 100 is not limited to the structures disclosed in FIGS. 2A-2G but instead may stand alone independent of the structures disclosed in FIGS. 2A-2G. It should be understood that FIGS. 2A-2G illustrate only partial schematic views of the energy storage device structure, and the energy storage device structure may contain any number of additional layers and / or additional materials common to energy storage devices, which are not shown for the sake of brevity. It should also be noted that although the method 100 illustrated in FIG. 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 embodiments of the disclosure provided herein.

[0031] Referring to FIG. 2A, at operation 110, a flexible substrate stack 202 is provided. The flexible substrate stack 202 may include one or more layers. In some embodiments, for example, for an alkali metal, lithium metal, or lithium alloy anode device, the flexible substrate stack 202 can be or include a current collector. As shownAttorney Docket No.: E165-0161PCT in FIG. 2A, the flexible substrate stack 202 is a current collector. In one or more embodiments, which can be combined with other embodiments, the flexible substrate stack 202 includes a web-based substrate, for example, the current collector can be a web-based substrate. Any suitable current collector may be used. The current collector can include or be, but is not limited to, 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.

[0032] In operation 120, an alkali metal layer, such as a first lithium metal containing layer 204 is formed on the flexible substrate stack 202, as shown in FIG. 2B. In an embodiment, the first lithium metal containing layer 204 comprises a lithium metal layer. Any suitable lithium deposition process for depositing thin films of the alkali metal may be used to deposit the first lithium metal containing layer 204 on the flexible substrate stack 202. Deposition of the first lithium metal containing layer 204 may be by PVD processes, such as evaporation. The chambers for depositing the thin film of the alkali metal or alloy may include a PVD system, such as an electronbeam evaporator, a thermal evaporator, or a lamination system.

[0033] In operation 130, solute particles 206 are disposed on the first lithium metal containing layer 204, as shown in FIG. 2C. The solute particles 206 may be any Li- compatible solute particles such as Si, SiOx, Zn, Bi, Ag, Sn, Al, ZnO, TiOx, or combinations thereof. For example, the solute particles 206 comprises silicon in which the solute particles 206 are disposed on the first lithium metal containing layer 204 as metallurgical grade Si powder. When using metallurgical grade Si powder, the solute particles 206 may be disposed on the first lithium metal containing layer 204 using various physical and chemical methods. For example, the solute particles 206 can be slurry coated on first lithium metal containing layer 204 to a desired thickness (eg. PVDF, SBR, PVA binders) using slot-die coating, comma head coating, bar coating, and the like.

[0034] In an embodiment, operation 130 forms a layer of solute particles 206 on the flexible substrate stack 202 having a thickness between about 1 micrometer and about 20 micrometers, such as between about 3 micrometers and about 5 micrometers. In another embodiment, the solute particles 206 can be disposed onAttorney Docket No.: E165-0161PCT the first lithium metal containing layer 204 as a vapor deposition deposited solute layer. In some embodiments, which can be combined with other embodiments herein, the solute particles 206 may be formed via a deposition process, for example, a physical vapor deposition (PVD) process. In such an embodiment, the deposited solute layer can be formed with a thickness between about 5 micrometers and about 50 micrometers, such as between about 10 micrometers and about 20 micrometers. Without being bound by theory, it should be noted that the thickness of the solute layer may at least partially depend on the cell capacity loading (mAh / cm2) and electrode porosity of the energy storage device to be formed.

[0035] In an embodiment, the solute particles 206 may be treated or coated prior to being disposed on the flexible substrate stack 202. For example, the solute particles 206 comprising silicon may be coated with Ag, Ni, Fe, Co, Ni, Pd, or Cu to enhance the conductivity of the solute particles 206 prior to being disposed on the first lithium metal containing layer 204 in operation 130.

[0036] In another embodiment, the solute particles 206 may alternatively be disposed directly on the current collector of the flexible substrate stack 202 such that the formation of the first lithium metal containing layer 204 in operation 120 is omitted. In such an embodiment, the solute particles 2016 may instead be disposed on an electrochemically compatible conductive coating formed on the flexible substrate stack 202 prior to operation 130. Operation 120 may therefore alternatively include thinly coating the current collector with the conductive coating so as to modify the surface roughness of the current collector to improve the interaction between the current collector and the solute particles 206.

[0037] In operation 140, a second lithium containing metal layer 208 of a flexible support layer stack 210 is laminated to the flexible substrate stack 202. Operation 140 includes the second lithium containing metal layer 208 contacting the solute particles 206 such that the solute particles 206 are disposed between the first lithium metal containing layer 204 and the second lithium containing metal layer 208. In an embodiment, the flexible support layer stack 210 includes the second lithium containing metal layer 208 deposited on a flexible support layer 212. In another embodiment, the flexible support layer stack 210 may include a release layer between the second lithium containing metal layer 208 and the flexible support layer 212.Attorney Docket No.: E165-0161PCT

[0038] In one or more embodiments, which may be combined with other embodiments, the flexible support layer stack 210 and the second lithium containing metal layer 208 are pre-fabricated. In other embodiments, the flexible support layer stack 210 is pre-fabricated and the second lithium containing metal layer 208 is formed on the flexible support layer stack 210 via a deposition process, for example, a physical vapor deposition (PVD) process.

[0039] The flexible support layer 212 may comprise any suitable material that is compatible with the targeted processing conditions. In some embodiments, the flexible support layer 212 includes a plurality of sub-layers, such as a release layer (not shown) or an interface layer (not shown) between the second lithium containing metal layer 208 and the flexible support layer 212. In one or more embodiments, which can be combined with other embodiments, the flexible support layer 212 can be or include, one or more layers selected from plastic, polymer materials, metallized plastic, metals, paper, multilayers thereof, or a combination thereof. Suitable polymer materials include polymer materials that are transparent to laser light and have low to no photon absorption to prevent overheating and fire incidents. Example of suitable polymer 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 polymer such as Polyethylene 2,5-furandicarboxylate (PEE), multilayers thereof, or a combination thereof. In one or more embodiments, which can be combined with other embodiments, the flexible support layer 212 is a web-based substrate.

[0040] In one or more embodiments, the polymer material of the flexible support layer 212 is selected so that the second lithium containing metal layer 208 can be debonded from flexible support Iayer212 by photo-initiated lift-off, for example, a laser lift-off process, wherein the polymer material interacts with photons entering from the flexible support layer 212. In one or more embodiments, which can be combined with other embodiments, the flexible support layer 212 has a thickness in a range from about 1 micron to about 100 microns, or in a range from about 1 micron to about 100 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.Attorney Docket No.: E165-0161PCT

[0041] Referring to FIG. 2E, in operation 150, the flexible support layer stack 210 is exposed to a laser activation process, such as a LLO process. The LLO process of operation 150 includes exposing the flexible support layer stack 210 having the second lithium containing metal layer 208 formed thereon to a laser. In one or more embodiments, during the laser lift-off process of operation 150, laser energy from a laser 214 provided by one or more laser sources 216 is directed through a backside 212b of the flexible support layer 212 to activate the interface of the second lithium containing metal layer 208 and the flexible support layer stack 210, for example, the Li-PET interface. In another embodiment, laser energy from the laser 214 may activate the interface of the release layer (if present) and the second lithium containing metal layer 208. As is shown in FIG. 2E, the laser 214 can be directed through the backside of the flexible support layer stack 210, for example, from the plastic containing substrate or PET side of the flexible support layer 212. Exposure to the laser can activate not only a surface of the second lithium containing metal layer 208 but also a portion of the flexible support layer stack 210. For example, exposure to the laser can activate a portion of the flexible support layer stack 210, for example, an activated portion 218 of the flexible support layer 212. In one or more embodiments, the activated portion 218 can correspond to a void volume. Exposure to the laser can induce a lithium transfer process creating a void volume between the second lithium containing metal layer 208 and the flexible support layer 212. This void volume can make separation of the second lithium containing metal layer 208 from the flexible support layer 212 easier during transfer of the second lithium containing metal layer 208 from the flexible support layer stack 210 to the flexible substrate stack 202. The void volume can be formed in a pattern such that portions of the second lithium containing metal layer 208 that are above the patterned void volume can be more easily removed thus forming a pattern when transferred onto the flexible substrate stack 202. In addition, exposure to the laser 214 can be used to pattern the second lithium containing metal layer 208 such that a precise pattern of patterned lithium metal can be transferred from the flexible support layer 212 to the flexible substrate stack 202.

[0042] In some embodiments, which can be combined with other embodiments, the mechanism of void formation is believed to be a combination of plasma generation by photoionization with recombination of sublimation and lithium.Attorney Docket No.: E165-0161PCT

[0043] The laser source 216 can be an IR laser source. The laser source 216 can provide is a pulsed laser. In one embodiment, which can be combined with other embodiments described herein, the laser 214 includes a Gaussian beam profile with a beam quality “M2-factor” of less than about 1.3. In another embodiment, which can be combined with other embodiments described, the laser 214 is a Bessel-type beam profile. In yet other embodiments, the laser 214 is a multi-focus laser and uses a bifocal lens as part of an optical array. Multiple lenses may also be used within the optical array to diffract the laser 214 and form multiple focal points within the flexible support layer 212 and the second lithium containing metal layer 208. The laser source 216 can be in communication with a controller. The controller may control other input parameters or output parameters of the laser source 216.

[0044] In one or more embodiments, which can be combined with other embodiments, laser source 216 is an IR fiber laser. The IR fiber laser is a 1060-nm laser with a pulse width of 5 to 500 nanoseconds, for example, a 30 nanosecond pulse width, a Gaussian profile, ~150 urn spot size, 2 m / sec raster speed, and a line distance of 70 urn.

[0045] The laser lift-off process can be run in a single pass only, or in multiple passes. However, due to the moving speed of the flexible substrates, it may be preferable that the laser lift-off process be performed in a single pass.

[0046] In one or more embodiments, which can be combined with other embodiments, the flexible support layer stack 210 including the second lithium containing metal layer 208 is exposed to a pre-heat process prior to operation 150. The pre-heat process can include exposing the second lithium containing metal layer 208 to thermal energy, for example, thermal energy provided by an IR lamp source. In some embodiments, where the second lithium containing metal layer 208 is a thicker layer, pre-heating the second lithium containing metal layer 208 can reduce the amount of energy during the laser lift-off process.

[0047] Referring to FIG. 2F, at operation 160, the patterned portion of the second lithium containing metal layer 208 exposed to the laser 214 is separated from the flexible support layer 212 to form the anode film stack 200. As shown in FIG. 2F, the first lithium metal containing layer 204 and the second lithium containing metal layerAttorney Docket No.: E165-0161PCT208 may comprise of the same lithium containing metal material such that after the second lithium containing metal layer 208 is transferred to the flexible substrate stack 202, a single patterned lithium containing metal layer 220 is formed on the flexible substrate stack 202 with the solute particles 206 disposed there within.

[0048] Not to be bound by theory but it is believed that laser photons are selectively absorbed at the interface of the second lithium containing metal layer 208 / flexible support layer 212, for example, the Li / PET interface, and less reflection of laser light is intended. With selective exposure / absorption, the laser lift-off process described, the interface can locally create gas / plasma or induce chemical reaction to form density change creating a ‘gap’ or void volume for easy release. For example, during the laser lift-off process, the laser beam passing through the backside of the flexible support layer 212, for example, the PET substrate is absorbed by the lithium in the second lithium containing metal layer 208 to generate plasma, causing high-pressure gas and interfacial separation of the flexible support layer 212 from the second lithium containing metal layer 208. At the same time, the released second lithium containing metal layer 208 can be attached to the surface of the flexible substrate stack 202 due to the high-pressure gas. The plasma may be maintained for a very short time, for example, around the pulse duration, and then gradually stabilizes to become gas or particles. Upon separation from the flexible support layer 212, the high-pressure gas is released resulting in a plurality of voids 222 in a top surface of the patterned lithium containing metal layer 220, as shown in FIG. 2F. In an embodiment, the voids 222 resemble a plurality of concave or recessed cavities each having a circular shape and formed in the top surface of the patterned lithium containing metal layer 220.

[0049] Referring to FIG. 2G, in addition to releasing the second lithium containing metal layer 208 from the flexible support layer 212, energy from the exposure to the laser 214 during the laser lift-off process also causes a reaction between the patterned lithium containing metal layer 220, the first lithium containing metal layer 204, and the solute particles 206 disposed on the flexible substrate stack 202 so as chemically transform the layers into a patterned lithium alloy layer 224. The material of the resulting lithium alloy formed depends on the chemistry and material of the solute particles 206. In the case where the solute particles 206 comprises silicon, the patterned lithium alloy layer 224 in turn comprises a LiSi alloy metal. In one or moreAttorney Docket No.: E165-0161PCT embodiments, which can be combined with other embodiments, the reaction between the lithium in the patterned lithium containing metal layer 220 and silicon solute particles 206 on the flexible substrate stack 202 causes the formation of various lithium silicide crystalline phases, such as Li 1 sSis or Li22Si4.

[0050] After the patterned lithium containing metal layer 220 is transferred in operation 160 to form the anode film stack 200, optionally, at operation 170, postprocessing processes may be performed on the anode film stack 200. In an embodiment, which may be combined with other embodiments herein, the anode film stack 200 may be heated during post-processing to catalyze or facilitate the reaction between the solute particles 206 and the patterned lithium containing metal layer 220 to form the patterned lithium alloy layer 224.

[0051] In some embodiments, post-processing operations may alternatively include the anode film stack 200 being exposed to a laser ablation process to remove any residue remaining (if a release layer was used) on either the flexible substrate stack 202, the patterned lithium containing metal layer 220 / patterned lithium alloy layer 224, or both the flexible substrate stack 202 and the patterned lithium containing metal layer 220 / patterned lithium alloy layer 224. In other embodiments, operation 170 may optionally include one or more of passivation layer formation to protect the exposed lithium metal surface, post-calendering to flatten the exposed lithium metal surface, lithium metal reflow to flatten the exposed lithium metal surface, or slitting to cut the exposed portions of the flexible substrate stack to form electrode structures.

[0052] At operation 180, the anode film stack 200 can optionally be integrated with a cathode structure (not shown), a separator (not shown), or both the cathode structure and the separator to form an energy storage device.

[0053] FIG. 3 illustrates a flow chart of a method 300 for manufacturing an anode film stack 400 in accordance with one or more embodiments of the present disclosure. FIGS. 4A-4G illustrate views of various stages of manufacturing the anode film stack 400 in accordance with one or more embodiments of the present disclosure. Although FIGS. 4A-4G are described in relation to method 300; it will be appreciated that the structures disclosed in FIGS. 4A-4G are not limited to the method 300, but insteadAttorney Docket No.: E165-0161PCT may stand alone as structures independent of the method 300. Similarly, although the method 300 is described in relation to FIGS. 4A-4G, it will be appreciated that the method 300 is not limited to the structures disclosed in FIGS. 4A-4G but instead may stand alone independent of the structures disclosed in FIGS. 4A-4G. It should be understood that FIGS. 4A-4G illustrate only partial schematic views of the energy storage device structure, and the energy storage device structure may contain any number of additional layer and / or additional materials common to energy storage devices, which are not shown for the sake of brevity. It should also be noted that although the method 300 illustrated in FIG. 3 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 embodiments of the disclosure provided herein.

[0054] Referring to FIG. 4A, at operation 310, a flexible substrate stack 202 is provided. The flexible substrate stack 202 can include one or more layers. As shown in FIG. 4A, the flexible substrate stack 202 is a current collector.

[0055] In operation 320, a first lithium metal containing layer 204 is formed on the flexible substrate stack 202 as shown in FIG. 4B similar to operation 120. After operation 320 and prior to operation 330, the flexible substrate stack 202 having the first lithium metal containing layer 204 formed thereon may be transferred from a vacuum coating system to a lamination transfer apparatus for transferring SIDT film stacks.

[0056] In operation 330, a solute layer 402 formed on a flexible solute support stack 404 is laminated to the flexible substrate stack 202, as shown in FIG. 4G. The flexible solute support stack 404 includes a flexible support layer 406. In some embodiments, the flexible solute support stack 404 includes a plurality of sub-layers, such as a release layer (not shown) between the solute layer 402 and the flexible support layer 406. The solute layer 402 may be made of any Li-compatible solute such as Si, SiOx, Zn, Bi, Ag, Sn, Al, ZnO, TiOx, or combinations thereof. For example, the solute layer 402 may be a silicon coating layer formed on the flexible support layer 406. The flexible support layer 406 may be similar to the flexible support layer 212 as described above, for use in SIDT transfer of the solute layer 402 to the flexible substrate stack 202.Attorney Docket No.: E165-0161PCT

[0057] During operation 330, pressure is applied to one or more of the flexible substrate stack 202 and the flexible solute support stack 404 to laminate the solute layer 402 to the flexible substrate stack 202. In an embodiment, the lamination process includes pressing the solute layer 402 to the flexible solute support stack 404 with a magnitude of pressure sufficient to attach the solute layer 402 to the flexible substrate stack 202 without damaging the solute layer 402. In other words, the pressure is such that the solute layer 402 is not mechanically destroyed or degraded, such as by cracking or crushing. Pressure may be applied using any suitable techniques. In one or more embodiments, pressure is applied via a calendering process. The calendering process may include using a pair of calendering rollers 408a-b as is shown in FIG. 4C. For example, pressure may be applied to the backside of the flexible support layer 406 and a backside of the flexible substrate stack 202.

[0058] In operation 340, the solute layer 402 is separated from the flexible solute support stack 404. In one or more embodiments, which can be combined with other embodiments, the release layer (if present) remains on the flexible support layer 406 after operation 340. In one or more embodiments, which can be combined with other embodiments, the solute layer 402 includes a thickness between about 5 micrometers and about 50 micrometers, such as between about 10 micrometers and about 20 micrometers.

[0059] Referring to FIG. 4D, in operation 350, a second lithium containing metal layer 208 of a flexible support layer stack 210 is laminated to the solute layer 402 of the flexible substrate stack 202. In an embodiment, the flexible support layer stack 210 includes the second lithium containing metal layer 208 deposited on a flexible support layer 212. In other embodiments, the flexible support layer stack 210 includes the second lithium containing metal layer 208 deposited on a release layer formed over the flexible support layer 212.

[0060] In operation 360, as shown in FIG. 4E, the flexible support layer stack 210 is exposed to a LLO process, such as the LLO process described above in operation 150. In one or more embodiments, the laser lift-off process of operation 360 similarly induces a lithium transfer process by creating a plurality of void volumes or voids between the second lithium containing metal layer 208 and the flexible support layer 212. The voids or void volume can make separation of the second lithium containingAttorney Docket No.: E165-0161PCT metal layer 208 from the flexible support Iayer 212 easier during transfer of the second lithium containing metal layer 208 from the flexible support layer stack 210 to the flexible substrate stack 202. The void volume can be formed in a pattern such that portions of the second lithium containing metal layer 208 that are above the patterned void volume can be more easily removed thus forming a pattern when transferred onto the flexible substrate stack 202. In addition, exposure to the laser 214 can be used to pattern the second lithium containing metal layer 208 such that a precise pattern of patterned lithium metal can be transferred from the flexible support layer 212 to the flexible substrate stack 202.

[0061] Referring to FIG. 4F, at operation 370, the patterned portion of the second lithium containing metal layer 208 exposed to the laser 214 is separated from the flexible support layer 212 to form the anode film stack 200, including a patterned lithium containing metal layer 220 formed on the solute particles 206 and the flexible substrate stack 202. As shown in FIG. 4G, the void volumes formed during the laser lift-off process in operation 360 remains and results in a plurality of voids to be formed in a top surface of the patterned lithium containing metal layer 220 transferred to the flexible substrate stack 202.

[0062] Referring to FIGS. 4G and 4H, in addition to releasing the second lithium containing metal layer 208 from the flexible support layer 212, energy from the exposure to the laser 214 during the laser lift-off process also causes the patterned lithium containing metal layer 220 and the first lithium metal containing layer 204 to chemically react with the solute layer 402 disposed on the flexible substrate stack 202. Exposure to the laser from the lift-off process therefore causes a reaction between the second lithium containing metal layers 204, 208 and the solute layer 402 to transform the layers into a patterned lithium alloy layer 224. In one or more embodiments, which can be combined with other embodiments, the reaction between the lithium in the patterned lithium containing metal layer 220 and the solute layer 402 comprising silicon on the flexible substrate stack 202 causes the formation of various lithium silicide crystalline phases, such as LiisSis or Li22Si4.

[0063] After the patterned lithium containing metal layer 220 is transferred in operation 370 to form the anode film stack 200, optionally, at operation 380, postprocessing operations may be performed on the anode film stack 200. Operation 380Attorney Docket No.: E165-0161PCT may be similar to the post-processing operations described above for operation 170. For example, operation 380 may optionally include one or more of passivation layer formation to protect the exposed lithium metal surface, post-calendering to flatten the exposed lithium metal surface, lithium metal reflow to flatten the exposed lithium metal surface, or slitting to cut the exposed portions of the flexible substrate stack to form electrode structures.

[0064] At operation 390, the anode film stack 200 can optionally be integrated with a cathode structure (not shown), a separator (not shown), or both the cathode structure and the separator to form an energy storage device.

[0065] In yet a further embodiment, operation 320 in method 300 may alternatively be omitted such that the solute layer 402 is laminated directly on a current collector of the flexible substrate stack 202 in operation 330. In one or more embodiments, which can be combined with other embodiments, the solute layer 402 formed directly on the current collector includes a thickness between about 5 micrometers and about 50 micrometers, such as between about 10 micrometers and about 20 micrometers. In yet another embodiment, which can be combined with other embodiments herein, the solute layer 402 may be deposited directly on the current collector of the flexible substrate stack 202. For example, the solute layer 402 may be deposited on the flexible substrate stack 202 comprising a current collector via a vapor deposition process, such as a physical vapor deposition process.

[0066] FIGS. 5A-5B illustrate schematic views of an anode film stack 500 during lithiation and delithiation processes, in accordance with one or more embodiments of the present disclosure. Specifically, FIGS. 5A and 5B show schematic top and side views of the anode film stack 500 during charging and discharging. Lithiation and delithiation are electrochemical processes that occur when charging and discharging occurs in lithium-ion batteries. In lithium ion batteries, movement of the lithium ions creates free electrons in the anode which create a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered / external circuit to the negative current collector. Accordingly, when the battery is discharging / in use and providing an electric current, the anode releases lithium ions to the cathode (lithiation), generating a flow of electrons from one side toAttorney Docket No.: E165-0161PCT the other. When the battery is being charged, the opposite occurs in which lithium ions are released by the cathode (delithiation) and received by the anode.

[0067] As mentioned above, inherent to the high-capacity electrode materials is material degradation and failure due to the large volumetric changes during the electrochemical cycling, causing fast capacity decay and low cycle life. Similarly, the insertion and diffusion of lithium ions during lithiation and delithiation in lithium ion anodes can cause high volume changes that can adversely affect energy density and cycle life of the batteries. Specifically, without being bound by theory, it is known that lithiation-induced volumetric expansion tends to generate stress concentrations that can cause or lead to chemomechanical fracture of the electrodes. Such fractures consequently can cause the loss of electrical contract between active materials, current collectors, and electrolytes, further resulting in rapid capacity fading and poor cyclability. In some instances, lithiation induces large compressive stress inside the active materials so as to slow down further lithiation, i.e., lithiation retardation. Large volumetric changes during the lithiation / delithiation cycles can also cause repeated breaking and forming of the solid electrolyte interface (SEI) film on the active materials, resulting in unstable SEI growth and converting cycleable live lithium atoms in the electrode and electrolyte to dead lithium atoms in the SEI, eventually leading to lithium exhaustion and battery death.

[0068] FIG. 5A shows a top and side view of the plurality of voids 222 formed in a top surface 502 of the anode film stack 500 during the patterning and laser lift-off process. Prior to lithiation, the plurality of voids 222 have a larger pre-lithiation diameter D1 that allow for mechanical lithiation-induced volume expansion of the patterned lithium alloy layer 224. Specifically, as shown in FIG. 5B, the volume of the plurality of void 222 accommodates for the volume expansion of the core particle therewith during lithiation. Referring to FIG. 5B, lithiation-induced volume expansion causes the diameters of each of the plurality of voids 222 to reduce to a smaller post- lithiation diameter D2. The plurality of voids 222 compensate for the lithiation-induced volume expansion thereby reducing the generation of stress concentrations throughout the anode film stack 500 including the patterned lithium alloy layer 224. Thus, the structure of the patterned lithium alloy layer 224 provides a buffer matrix in which the plurality of voids 222 formed in the patterned lithium alloy layer 224 as partAttorney Docket No.: E165-0161PCT of the patterned laser lift-off operation subsequently minimizes the mechanical degradation of the core lithium alloy material during lithiation and delithiation. By being pre-configured to accomodate for the volumetric changes during electrochemical cyling, advantages of the present disclosure provide for forming anode film stacks that provide for increased cycle life and capacity retention and faster charging in the resulting formed energy storage devices.

[0069] When introducing elements of the present disclosure or exemplary aspects or embodiment(s) thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements.

[0070] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments 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

Attorney Docket No.: E165-0161PCTWhat is claimed is:

1. A method of forming an alloy film stack, comprising: disposing solutes on a flexible substrate stack, the flexible substrate stack comprising a current collector; laminating a lithium metal containing layer to the solutes on the flexible substrate stack, the lithium metal containing layer formed on a polymer substrate of a flexible support layer stack; exposing portions of the lithium metal containing layer to laser energy to create a void volume between the lithium metal containing layer and the flexible support layer stack, wherein exposure to the laser energy causes a reaction between the lithium metal containing layer and the solute layer; and transferring the exposed portions of the lithium metal containing layer from the flexible support layer stack to the flexible substrate stack.

2. The method of claim 1 , wherein the reaction between the lithium metal containing layer and the solutes from exposure to laser energy causes the lithium metal containing layer and the solute layer to form a lithium alloy layer on the substrate stack.

3. The method of claim 2, wherein the void volume formed in the lithium metal containing layer from exposure to laser energy causes a plurality of voids to be formed in a top surface of the lithium alloy layer after the lithium metal containing layer is separated from the flexible support layer stack.

4. The method of claim 1 , further comprising forming a lithium metal layer on the flexible substrate stack prior to disposing the solutes on the flexible substrate stack.

5. The method of claim 1 , wherein disposing solutes on the flexible substrate stack comprises depositing a solute layer on a top surface of the substrate stack using a vapor deposition process.

6. The method of claim 5, wherein the solute layer is deposited to a thickness between about 5 micrometers and about 50 micrometers, such as between about 10 micrometers and about 20 micrometers.

7. The method of claim 1 , wherein disposing the solutes on the flexible substrate stack comprises slurry coating metallurgical grade Si powder on the flexible substrate stack.Attorney Docket No.: E165-0161PCT8. The method of claim 1 , wherein the solutes are selected the group consisting of Si, SiOx, Zn, Bi, Ag, Sn, Al, ZnO, TiOx, or combinations thereof.

9. The method of claim 1 , wherein exposing portions of the lithium metal containing layer to laser energy comprises directing one or more lasers through a backside of the polymer substrate to the lithium metal containing layer.

10. A method of forming an alloy anode film stack, comprising: forming a lithium metal layer on a flexible substrate stack; laminating a solute layer to the lithium metal layer, the solute layer formed on a polymer substrate of a flexible solute support stack; separating the solute layer from the flexible solute support stack; laminating a lithium metal containing layer to the solute layer, the lithium metal containing layer formed on a polymer substrate of a flexible support layer stack; exposing portions of the lithium metal containing layer to laser energy to create a void volume between the lithium metal containing layer and the flexible support layer stack, wherein exposure to laser energy causes a reaction between the lithium metal containing layer and the solute layer; and separating the lithium metal containing layer from the flexible support layer stack to transfer the exposed portions of the lithium metal containing layer to the flexible substrate stack.

11. The method of claim 10, wherein laminating the solute layer to the lithium metal layer comprises applying pressure to one or more of the flexible solute support stack and the flexible substrate stack.

12. The method of claim 10, wherein the reaction between the lithium metal containing layer and the solute layer from exposure to laser energy causes the lithium metal containing layer and the solute layer to form a lithium alloy layer on the substrate stack.

13. The method of claim 12, wherein the void volume formed in the lithium metal containing layer from exposure to laser energy causes a plurality of voids to be formed in a top surface of the lithium alloy layer after the lithium metal containing layer is separated from the flexible support layer stack.

14. The method of claim 10, wherein the solute layer comprises solute particles selected the group consisting of Si, SiOx, Zn, Bi, Ag, Sn, Al, ZnO, TiOx, or combinations thereof.Attorney Docket No.: E165-0161PCT15. The method of claim 10, further comprising optional post-processing operations to heat the exposed portions of the lithium metal layer transferred the flexible substrate stack.

16. A film stack, comprising: a flexible substrate stack; and a lithium alloy layer formed over the flexible substrate stack and having a plurality of voids formed in a top surface of the lithium alloy layer, wherein the lithium alloy layer is formed from a reaction between a solute layer on the flexible substrate stack and a lithium metal containing layer transferred to the flexible substrate stack from a flexible support layer stack using a laser lift-off process.

17. The film stack of claim 16, wherein the plurality of voids are formed from the laser lift-off process used to separate the flexible support layer stack from portions of the lithium metal containing layer exposed to laser energy.

18. The film stack of claim 16, wherein laser energy from the laser lift-off process causes the solute layer to react with the lithium metal containing layer.

19. The film stack of claim 16, wherein the solute layer comprises solute particles selected the group consisting of Si, SiOx, Zn, Bi, Ag, Sn, Al, ZnO, TiOx, or combinations thereof.

20. The film stack of claim 16, wherein the laser lift-off process for transferring the lithium metal containing layer to the flexible substrate stack comprises directing one or more lasers through a backside of the flexible support layer stack to the lithium metal containing layer.

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