Metallic lithium coating via PVD on battery separator and passivated with inorganic layer(s)

Abstract

Embodiments of the disclosure relate generally to Li batteries, methods of making the same, and equipment for making the same. In particular embodiments of the disclosure are relate to a separator stack includes a separator film, a metal lithium (Li) layer disposed on the separator film, and an inorganic passivation layer disposed on the metal Li layer.

Description

METALLIC LITHIUM COATING VIA PVD ON BATTERY SEPARATOR AND PASSIVATED WITH INORGANIC LAYER(S)BACKGROUNDField

[0001] Embodiments of the present disclosure relate generally to Li batteries, methods of making the same, and equipment for making the same.Description of the Related Art

[0002] Rechargeable energy storage devices are currently becoming increasingly essential for many fields of everyday life. High-capacity energy storage devices incorporating alkali metals, such as lithium-ion (Li-ion) batteries, are used in a growing number of applications, including portable electronics, medical, transportation, grid- connected large energy storage, renewable energy storage, and uninterruptible power supply (UPS).

[0003] Like the heavy element homologs of the first main group, alkali metals such as lithium are characterized by a strong reactivity with a variety of substances. Lithium is reactive with water, alcohols and other substances that contain protic hydrogen. Lithium is also unstable in air and reacts with oxygen, nitrogen and carbon dioxide. Lithium is normally handled under an inert gas atmosphere (noble gases such as argon) and with other processing operations that are also performed in an inert gas atmosphere. As a result, lithium provides several challenges when it comes to processing, storage, and transportation.

[0004] In addition, Li batteries generally suffer an irreversible lithium loss during the first operating cycle.

[0005] Thus, there is a need for improved Li battery designs which can readily accommodate for the loss of lithium, methods of making these improved batteries, and equipment for making these improved batteries.SUMMARY

[0006] In an embodiment a separator stack includes a separator film, a metal lithium (Li) layer disposed on the separator film; and an inorganic passivation layer disposed on the metal Li layer.

[0007] In another embodiment a method for forming a separator stack includes providing a separator film, disposing a metal lithium (Li) layer on the separator film, and disposing an inorganic passivation layer on the metal Li layer.

[0008] In another embodiment a battery includes a separator stack comprising, a separator film, a metallic lithium (Li) layer disposed on the separator film, and an inorganic passivation layer disposed over the metal Li layer.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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.

[0010] FIG. 1 is a cross-sectional representation of an example of a lithium ion battery incorporating a separator, according to some embodiments.

[0011] FIGS. 2A-2F are cross-sectional representations of various stages of manufacturing a separator of a lithium ion battery according to some embodiments.

[0012] FIG. 3 is a method for forming a separator of a lithium ion battery according to some embodiments.

[0013] FIG. 4 is a schematic view of an apparatus for forming at least a portion of the separator stack described in accordance some embodiments of the present disclosure.

[0014] FIGS. 5A-5B are plots depicting cell voltage versus capacity for a cell a 1 miliamp hour (1 mAh) plating capacity.

[0015] FIG. 6A-6C are SEM images of a metal lithium (Li) layer of a separator stack for a control cell, a cell in which Li was released onto the separator stack using lithium laser lift-off (LLO) with a high overlap, and a cell in which Li was released onto the separator stack using lithium laser lift-off (LLO) with a low according to implementations described herein.

[0016] FIG. 7 is a plot depicting cumulative capacity loss versus the cycle count for a prelith iated cell and an anode free cell.

[0017] 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.DETAILED DESCRIPTION

[0018] Embodiments of the present disclosure relate generally to Li batteries, methods of making the same, and equipment for making the same.

[0019] Energy storage devices, for example, Li-ion batteries, a lithium ion-cell battery may comprise a positive electrode (a cathode), a negative electrode (an anode) and a separator. During a first few charging cycles of a lithium-ion cell, lithium loss occurs due to formation of byproducts such as the solid electrolyte interphase (SEI) from the reduction of electrolyte. The formation of the SEI on the anode serves as a passivation layer to mitigate further reaction between lithium and other cell constituents. Lithium ions are bound and can no longer be used as charge carriers which reduces the maximum capacity of the cell. Prelithiation can be used to compensate for the lithium loss. During prelithiation, additional lithium is added to the cell prior to the first cycle to compensate for the lithium loss. Typical prelithiation methods include chemical prelithiation, electromechanical prelithiation, prelithiation using additives, and direct contact prelithiation. Currently, prelithiation methods involve complex steps and wasted excess materials. Chemical prelithiation includes long reaction times and uses chemicals and chemical reactions that are unsuitable for upscaling production. Electrochemical prelithiation is a complicated process that uses undesirable liquid electrolyte solutions. Prelithiation using additives is incompatible with the water-based slurries that are commonly used to manufacture lithium cells.Direct contact prelithiation includes laminating a separator stack to an anode. However, the lithium may not have the proper mechanical integrity and may be damaged during the lamination process. To protect the lithium material, a soluble polymer-based protective coating may be formed on the separator stack through calendaring or other processes. However, for prelithiation to take place, the polymer needs to be dissolved to allow a lithium layer of the separator stack to directly contact the anode. This requires a specific electrolyte chemistry and may be detrimental to battery performance.

[0020] Embodiments herein relate to a separator stack that includes an inorganic passivation layer that allows for direct contact prelithiation without having to dissolve the inorganic passivation layer.

[0021] FIG. 1 is an example energy storage device 100 having a separator stack 130 including an inorganic passivation layer. The energy storage device 100 may be a lithium-ion based energy storage device. The energy storage device 100, even though shown as a planar structure, may also be formed into a cylinder by rolling the stack of layers; furthermore, other cell configurations, for example, prismatic cells, button cells, or stacked electrode cells, may be formed. The energy storage device 100 includes a negative current collector 110, a negative electrode 120, a separator stack 130, a positive electrode 140 and a positive current collector 150. It should be understood that the energy storage device 100 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.

[0022] The current collectors 110, 150, on negative electrode 120 and positive electrode 140, respectively, can be identical or different electronic conductors. In some embodiments, at least one of the current collectors 110, 150 is a flexible substrate. In some embodiments, the flexible substrate includes a CPP film (i.e., a casting polypropylene film), an OPP film (i.e., an oriented polypropylene film), or a PET film (i.e., an oriented polyethylene terephthalate film) coated with a metal. Alternatively, the flexible substrate may be a pre-coated paper, a polypropylene (PP) film, a PEN film, a poly lactase acetate (PLA) film, or a PVC film. Examples of metals that the current collectors 110, 150 may be comprised of 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. Furthermore, current collectors may be of any form factor, shape and micro / macro structure. All components except current collectors 110 and 150 contain lithium ion electrolytes.

[0023] The negative electrode 120 may be any material compatible with the material of the positive electrode 140. The negative electrode 120 can be or include alkali metals, alkaline earth metals, and alloys thereof. The negative electrode 120 may have an energy capacity greater than or equal to 372 mAh / g, preferably > 700 mAh / g, and most preferably > 1000 mAh / g. The negative electrode 120 may be constructed from graphite, silicon, silicon-containing graphite, silicon oxide, alkali metals, for example, alkali metal foil or an alkali metal alloy foil (e.g. lithium aluminum alloys or sodium aluminum alloys), or a mixture of an alkali metal and / or an alkali metal alloy and materials such as carbon (e.g. coke, graphite), nickel, copper, tin, indium, silicon, oxides thereof, or a combination thereof. Suitable lithium-containing metal films include lithium metal, lithium metal foil or a lithium alloy foil (e.g. lithium aluminum alloys), or a mixture of a lithium metal and / or lithium alloy and materials such as carbon (e.g. coke, graphite), nickel, copper, tin, indium, silicon, oxides thereof, or a combination thereof. The negative electrode 120 can include intercalation compounds containing lithium or insertion compounds containing lithium.

[0024] In some embodiments of a lithium ion cell of the present disclosure, lithium is contained in atomic layers of crystal structures of carbon graphite (LiCe) at the negative electrode and lithium manganese oxide (LiMnCM), lithium iron phosphate (LiFEPCk), lithium nickel manganese cobalt oxide (LiNixMnyCoi-x-yO2) or lithium cobalt oxide (LiCoC ) at the positive electrode, for example, although in some embodiments the negative electrode may also include lithium absorbing materials such as silicon, tin, etc. The cell, even though shown as a planar structure, may also be formed into a cylinder by rolling the stack of layers; furthermore, other cell configurations may be formed. Electrolytes infused in cell components 120, 130 and 140 can be comprised of a I iquid / gel or a solid polymer and may be different in each.

[0025] In some examples, using direct contact between a metal lithium (Li) layer of the separator stack 130 and the negative electrode 120 is prel i th iated . The negative electrode 120 may be prelithiated due to electron flow caused by a potential differencebetween a metal Li layer 136 (FIGS. 2C-2E) of the separator stack 130 and the negative electrode 120. Stated differently, the potential difference causes lithium ions from the metal Li layer 136 to diffuse into the negative electrode 120 to compensate for lithium ions lost during a first charging cycle of the energy storing device 100.

[0026] FIGS. 2A-2F show an embodiment of the separator stack 130 in more detail. FIG. 3 illustrates a method 300 for forming the separator stack 130 according to one or more embodiments. Although FIGS. 2A-2F are described in relation to the method 300, it will be appreciated that the structures disclosed in FIGS. 2A-2E are not limited to the method 300, but instead may stand alone as structures independent of the method 300. Similarly, although the method 300 is described in relation to FIGS. 2A-2E, it will be appreciated that the method 300 is not limited to the structures disclosed in FIGS. 2A-2E but instead may stand alone independent of the structures disclosed in FIGS. 2A-2E.

[0027] At block 302, and as shown in FIG. 2A, a separator film 131 with pores 132 is provided. The separator may comprise, but it not limited to a polymer material, a ceramic material, or a composite material. Polymer materials may include, but are not limited to polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), or the like. Ceramic materials may include, but are not limited to fiberglass, metal oxides, thioborates, or the like. Composite materials may include, but are not limited to, ceramic-coated polymers, polymer-coated ceramics, metal coated polymers, or the like.

[0028] The separator film 131 may include, a cellulose based substrate, for example, a blend of cellulose nanofibers and aramid fibers, by way of non-limiting example. The separator film 131 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 one or more embodiments which can becombined with other embodiments, 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.

[0029] At block 304, and as shown in FIG. 2B, a coating material 134 is deposited over the separator film 131. In some embodiments, block 304 is optional. In one or more examples, the coating material 134 is deposited using physical vapor deposition (PVD), a slurry coating, or the like. In one example, the coating material 134 is doped with electrolyte additives. The coating material may comprise an alloying metal, including, but not limited to, silver (Ag), gold (Au), tin (Sn), bismuth (Bi), tellurium (Te), aluminum (Al), zinc (Zn), germanium (Ge), indium (In), and antimony (Sb), or the like. In other embodiments, the coating material 134 may comprise a ceramic material or a metal nitride material including, but not, limited to, zirconium oxide (ZrxOy), aluminum oxide (AlxOy), tantalum oxide (TaxOy), a metal boride material, or the like. Advantageously, the coating material 134 may act as a thermal barrier to prevent thermal damage during deposition (i.e. coating) of a metal Li layer 136 (block 306), protects the pores 132, and prevents pore clogging. In one example, the coating material 134 is dissolvable.

[0030] At block 306, and as shown in FIG. 2C, a metal lithium (Li) layer 136 is deposited over the separator film 131 (or the optional coating material 134). In one example, the metal Li layer 136 is deposited using a physical vapor deposition (PVD) process. For example, the PVD process is a thermal evaporation deposition. If the optional coating material 134 comprises an alloying metal and is deposited over the separator film 131 , the alloying metal (i.e., the coating material 134) contacts and diffuses into the bulk of the metal Li layer 136 as the coating material is dissolved. The optional coating material 134 diffusing into the metal Li layer 136 causes the metal Li layer 136 to become an alloyed metal Li layer.

[0031] At block 308, and as shown in FIG. 2D an inorganic passivation layer 138 is deposited over the metal Li layer 136. In one or more embodiments, which can be combined with other embodiments, the inorganic passivation layer 138 includes one or more layers. Each of the layer(s) of the inorganic passivation layer 138 comprises a non-polymer inorganic material. The one or more layers of the inorganic passivation layer 138 may be the same material or different materials.

[0032] In one example, the inorganic passivation layer 138 includes, but is not limited to, a metal material, a fluoride material, a carbon compound material, a metal oxide material, a nitride material, a boride material, or combinations thereof. Metal materials may include, but are not limited to, Ag, Bi, or the like. Fluoride materials may include, but are not limited to, lithium fluoride (LiF), silver fluoride (AgF), bismuth trifluoride (BiFs), or the like. Carbon compound metal materials include, but are not limited to, lithium carbonate (Li2CO3), lithium carbide (l_i2C2), or the like. Metal oxide materials include, but are not limited to, aluminum oxide (AlxOy), zirconium oxide (ZrxOy), or the like. Nitride materials may include, but are not limited to, lithium nitride (LisN). Boride materials may include, but are not limited to, boron nitride (BN). The inorganic passivation layer 138 may be formed by exposing the metal Li layer 136 to a gaseous reactant, plasma treating the metal Li layer 136, PVD, or the like.

[0033] In one example, the inorganic passivation layer 138 may comprise LiF, and may be formed using a gaseous reactant. Stated differently, a processing chamber (such as processing chambers 410-440 in FIG. 4) may be filled with gaseous reactant such as difluoride (F2). The F2 will cause a surface chemical reaction with the metal lithium (Li) layer 136, forming a LiF layer on top of the metal Li layer 136. In another example, the inorganic passivation layer 138 may comprise LiF and Li2C2 and may be deposited by treating the metal Li layer 136 using a carbon fluoride (CF) plasma. The metal Li layer 136 may be exposed to a CF plasma, causing a surface chemistry reaction and alternation, forming a passivation layer comprising LiF and Li2C2. In yet another example, the inorganic passivation layer 138 may be directly deposited onto the metal Li layer 136 using PVD. In another example, the inorganic passivation layer 138 may be a composite passivation layer. For example, at least two of the processes for forming the inorganic passivation layer 138 may be performed in succession. For example, a LiF layer may be formed over the metal Li layer 136 using a gaseous reactant, and an aluminum oxide layer may be deposited over the LiF layer using a PVD process. In one example, both deposition processes may be performed in-situ.

[0034] At block, 310 the separator stack 130 is disposed over the negative electrode 120 as is shown in FIG. 2E. The inorganic passivation layer is disposed over and is in contact with the negative electrode 120. Advantageously due to the inorganic materials that the inorganic passivation layer 138, the Li ions of the metal Li layer 136 are prelithiated into the negative electrode 120. Stated differently, the Liions are prelithiated into the negative electrode 120 using direct contact prelithiation without dissolving (removing) the inorganic passivation layer 138. In other embodiments, the inorganic passivation layer may remain in a cracked state (i.e., a non-conformal coating) during prelithiation. Thus, the negative electrode 120 shown in FIG. 2E is prelithiated. Alternatively, the inorganic passivation layer 138 may be dissolved prior disposing the separator stack 130 onto the negative electrode 120. As shown in FIG. 2F, the positive electrode 140 and the positive current collector can be disposed over the separator stack 130 (i.e., the separator film 131) forming energy storage device 100.

[0035] FIG. 4 illustrates a schematic view of an apparatus 400 for forming at least a portion of the separator stack 130 described in accordance with one or more embodiments of the present disclosure. The apparatus 400 may be a roll-to-roll coating system. The apparatus 400 may be used to perform portions of the method 300.

[0036] According to some embodiments, the apparatus 400 is constituted as a roll-to-roll system including an unwinding module 402, a processing module 404 and a winding module 406. In one or more embodiments, the processing module 404 comprises a plurality of processing modules or chambers 410, 420, 430 and 440 arranged in sequence, each configured to perform one processing operation to the continuous sheet of material 450, for example, the separator film 131 . In one or more embodiments, as depicted in FIG. 4, the processing chambers 410-440 are radially disposed about a coating drum 455. Arrangements other than radial are contemplated. For example, in another embodiment, the processing chambers may be positioned in a linear configuration.

[0037] In one embodiment, the processing chambers 410-440 are stand-alone modular processing chambers wherein each modular processing chamber is structurally separated from the other modular processing chambers. Therefore, each of the stand-alone modular processing chambers, can be arranged, rearranged, replaced, or maintained independently without affecting each other. Although four processing chambers 410-440 are shown, it should be understood that any number of processing chambers may be included in the apparatus 400.

[0038] The processing chambers 410-440 may include any suitable structure, configuration, arrangement, and / or components that enable the apparatus 400 to deposit portions of the separator stack 130 according to embodiments of the present disclosure. For example, but not limited to, the processing chambers may include suitable deposition systems including coating sources, power sources, individual pressure controls, deposition control systems, and temperature control. According to typical embodiments, the chambers are provided with individual gas supplies. The chambers are typically separated from each other for providing a good gas separation. The apparatus 400 according to embodiments described herein is not limited in the number of deposition chambers. For example, but not limited to, apparatus 400 may include 3, 6, or 12 processing chambers.

[0039] The processing chambers 410-440 typically include one or more deposition units 412, 422, 432, and 442. Generally, the one or more deposition units as described herein can be selected from the group of a CVD source, an ALD source, a PECVD source, and a PVD source. The one or more deposition units can include an evaporation source, a sputter source, such as, a magnetron sputter source, a DC sputter source, an AC sputter source, a pulsed sputter source, a radio frequency (RF) sputtering source, or a middle frequency (MF) sputtering source. The one or more deposition units can include an evaporation source. In one embodiment, the evaporation source is a thermal evaporation source or an electron beam evaporation source. In one embodiment, the evaporation source is a lithium (Li) source. Further, the evaporation source may also be an alloy of two or more metals. The material to be deposited (e.g., lithium) can be provided in a crucible. The lithium can, for example, be evaporated by thermal evaporation techniques or by electron beam evaporation techniques.

[0040] In some embodiments, one or some of the chambers may be configured for performing deposition by other methods, such as, but not limited to, chemical vapor deposition, atomic laser deposition or pulsed laser deposition. In some embodiments, one or some of the chambers may be configured for performing a plasma treatment process, such as a plasma oxidation or plasma nitridation process.

[0041] In one or more embodiments, the processing chambers 410-440 are configured to process both sides of the continuous sheet of material 450. Althoughthe apparatus 400 is configured to process the continuous sheet of material 450. In one or more embodiments, the continuous sheet of material 450 is a separator film, for example, the separator film 131 as described.

[0042] In one or more embodiments, the apparatus 400 comprises a transfer mechanism 452. The transfer mechanism 452 may include any transfer mechanism capable of moving the continuous sheet of material 450 through the processing region of the processing chambers 410-440. The transfer mechanism 452 may include a common transport architecture. The common transport architecture may include a reel-to-reel system with a common take-up reel 454 positioned in the winding module 406, the coating drum 455 positioned in the processing module 404, and a feed reel 456 positioned in the unwinding module 402. The common transport architecture may further comprise one or more auxiliary transfer reels 453a, 453b positioned between the take-up reel 454, the coating drum 455, and the feed reel 456. Although the apparatus 400 is depicted as having a single processing region, in one or more embodiments, it may be advantageous to have separated or discrete processing regions for each individual processing chamber 410-440. For embodiments having discrete processing regions, modules, or chambers, the common transport architecture may be a reel-to-reel system where each chamber or processing region has an individual take-up-reel and feed reel and one or more optional intermediate transfer reels positioned between the take-up reel and the feed reel.

[0043] The apparatus 400 may include the feed reel 456 and the take-up reel 454 for moving the continuous sheet of material 450 through the different processing chambers 410-440. In one or more embodiments, which can be combined with other embodiments, each of the processing chambers can be configured to deposit portions of the separator stack 130. In one embodiment, the first processing chamber 410 and the second processing chamber 420 are each configured to deposit one or more of layers of the metal Li layer 136. The third processing chamber 430 and the fourth processing chamber 440 are configured to deposit a portion of the inorganic passivation layer 138.

[0044] In another embodiment, the first processing chamber 410 is configured to deposit the coating material 134 on the continuous sheet of material 450, the second processing chamber 420 is configured to deposit the metal Li layer 136 on the on thecoating material 134, and the third processing chamber 430 and the fourth processing chamber 440 are configured to deposit layers of the inorganic passivation layer 138 on the metal Li layer 136. In another embodiment, the first processing chamber 410 and the second processing chamber are configured to each deposit a layer of the metal Li layer 136 on the continuous sheet of material 450, and the third processing chamber 430 and fourth processing chamber 440 are configured to deposit layers of inorganic passivation layer 138 on the metal Li layer 136. As noted above, the third processing chamber 430 and fourth processing chamber 440 may each use a different or a same process for depositing layers of the inorganic passivation layer 138 that comprise different or the same materials.

[0045] Any suitable lithium deposition process for depositing layer(s) of the metal Li layer 136 may be used. Deposition of the metal Li layer 136 may be by PVD processes, such as evaporation. The chambers for depositing the thin film of lithium metal may include a PVD system, such as an electron-beam evaporator, a thermal evaporator, or a lamination system. As described above the optional coating layer may be deposited using PVD. Any suitable deposition process may be used for depositing the inorganic passivation layer 138 such as using a gaseous reagent, plasma treatment, PVD or the like. The chambers for depositing the inorganic passivation layer 138 may include, a PVD system or a plasma processing system.

[0046] The apparatus 400 can also include a controller 460 for controlling processes performed by the apparatus 400. The controller 460 can be any type of controller used in an industrial setting, such as a programmable logic controller (PLC). The controller 460 includes a processor 462, a memory 464, and input / output (I / O) circuits 466. The controller 460 can further include one or more of the following components (not shown), such as one or more power supplies, clocks, communication components (e.g., network interface card), and user interfaces typically found in controllers for semiconductor equipment.

[0047] The memory 464 can include non-transitory memory. The non-transitory memory can be used to store the programs and settings described below. The memory 464 can include one or more readily available types of memory, such as read only memory (ROM) (e.g., electrically erasable programmable read-only memory(EEPROM), flash memory, floppy disk, hard disk, or random access memory (RAM) (e.g., non-volatile random access memory (NVRAM).

[0048] The processor 462 is configured to execute various programs stored in the memory 464, such as a program configured to execute the method 300 described. During execution of these programs, the controller 460 can communicate to I / O devices through the I / O circuits 466. For example, during execution of these programs and communication through the I / O circuits 466, the controller 460 can control outputs. The memory 464 can further include various operational settings used to control the apparatus 400.

[0049] FIGS. 5A-5B are plots depicting cell voltage versus capacity for a cell a 1 milliamp hour (mAh) plating capacity. The plots demonstrate that a prelithiated battery including the inorganic passivation layer 138 prevents lithium loss during the first few charging cycles. FIG. 5A illustrates a control cell that is not prelithiated. FIG. 5B illustrates a cell including separator stack 130 that includes an inorganic passivation layer 138 comprising Bi. As shown in FIG. 5A the control cell experiences a loss in capacity between plating and stripping. For example, the capacity of the cell decreases to 0.93 mAh hours during stripping due to SEI or disconnected (dead) lithium that cannot be stripped from a current collector. On the other hand, as shown in FIG. 5B, continuous stripping can be performed due to the addition of the metal Li layer 136 of separator stack 130. Stated differently, the capacity of the cell including the separator stack 130 has a strip capacity of 7.068 mAh while the metal Li layer 136 is still accessible through the inorganic passivation layer 138.

[0050] FIG. 6A is an SEM image of a baseline control cell. FIG. 6B is a cell in which the metal Li layer 136 of separator stack 130 was released using lithium laser lift-off (LLO) with a high overlap. FIG. 6C illustrates a cell in which the metal Li layer 136 of separator stack 130 was released using lithium laser lift-off (LLO) with a low overlap. As shown, the cell in FIG. 6C experiences less thermal damage than the cell in FIG. 6B, and thus, enables the pores of the separator stack to remain open (in the same manner as the control cell in FIG. 6A) during charge and discharge.

[0051] In the Summary and in the Detailed Description, and the Claims, and in the accompanying drawings, reference is made to particular features (including method operations) of the present disclosure. It is to be understood that the disclosure in thisspecification includes all possible combinations of such particular features. For example, where a particular feature is disclosed in the context of a particular aspect, embodiment, or example of the present disclosure, or a particular claim, that feature can also be used, to the extent possible in combination with and / or in the context of other particular aspects and embodiments of the present disclosure, and in the present disclosure generally.

[0052] FIG. 7 is a plot depicting cumulative capacity loss versus the cycle count for a prelithiated cell and an anode free cell. As illustrated in FIG. 7, the cumulative capacity loss in mAh is improved (i.e. , reduced) for a prelithiated cell versus an anode free cell.

[0053] Embodiments and all of the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structural means disclosed in this specification and structural equivalents thereof, or in combinations of them. Embodiments described herein can be implemented as one or more non-transitory computer program products, i.e., one or more computer programs tangibly embodied in a machine readable storage device, for execution by, or to control the operation of, data processing apparatus, e.g., a programmable processor, a computer, or multiple processors or computers.

[0054] The term “comprises” and grammatical equivalents thereof are used herein to mean that other components, ingredients, operations, etc. are optionally present. For example, an article “comprising” (or “which comprises”) components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. In addition, whenever a composition, an element or a group of elements is preceded with the transitional phrase “comprising” or grammatical equivalents thereof, it is understood that it is contemplated that the same composition or group of elements may be preceded with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is” preceding the recitation of the composition, element, or elements and vice versa.

[0055] Where reference is made herein to a method comprising two or more defined operations, the defined operations can be carried out in any order orsimultaneously (except where the context excludes that possibility), and the method can include one or more other operations which are carried out before any of the defined operations, between two of the defined operations, or after all of the defined operations (except where the context excludes that possibility).

[0056] 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

What is claimed is:1 . A separator stack comprising: a separator film; a metal lithium (Li) layer disposed on the separator film; and an inorganic passivation layer disposed on the metal Li layer.

2. The separator stack of claim 1 , further comprising a coating material disposed between the separator film and the metal Li layer.

3. The separator stack of claim 2, wherein the coating material comprises silver (Ag), gold (Au), tin (Sn), bismuth (Bi), tellurium (Te), aluminum (Al), zinc (Zn), germanium (Ge), indium (In), antimony (Sb), a ceramic material, a metal oxide material, a metal boride material, or a combination thereof.

4. The separator stack of claim 3, wherein the metal oxide material comprises aluminum oxide (AlxOy), zirconium oxide (ZrxOy), tantalum oxide (TaxOy), or a combination thereof.

5. The separator stack of claim 1 , wherein the inorganic passivation layer comprises one or more layers of a non-polymer inorganic material.

6. The separator stack of claim 5, wherein the one or more layers comprise a metal material, a fluoride material, a carbon compound material, a metal oxide material, a nitride material, a boride material, or a combination thereof.

7. The separator stack of claim 6, wherein the metal material comprises Ag (silver), bismuth (Bi), or a combination thereof.

8. The separator stack of claim 6, wherein the fluoride material comprises lithium fluoride (LiF), silver fluoride (AgF), bismuth trifluoride (BiFs), or a combination thereof, and the metal oxide material comprises aluminum oxide (AlxOy), zirconium oxide (ZrxOy), or a combination thereof.

9. The separator stack of claim 6, wherein the carbon compound material comprises lithium carbonate (U2CO3), lithium carbide (l_i2C2), or a combination thereof, the nitride material comprises lithium nitride (LisN), and the boride material comprises boron nitride (BN).

10. A method for forming a separator stack comprising: providing a separator film; disposing a metal lithium (Li) layer on the separator film; and disposing an inorganic passivation layer on the metal Li layer.11 . The method of claim 10, further comprising disposing a coating material between the separator film and the metal Li layer.

12. The method of claim 11 , wherein the coating material comprises silver (Ag), gold (Au), tin (Sn), bismuth (Bi), tellurium (Te), aluminum (Al), zinc (Zn), germanium (Ge), indium (In), antimony (Sb), a ceramic material, a metal oxide material, a metal boride material, or a combination thereof.

13. The method of claim 12, wherein the metal oxide material comprises at least one of aluminum oxide (AlxOy), zirconium oxide (ZrxOy), tantalum oxide (TaxOy), or a combination thereof.

14. The method of claim 10, wherein the inorganic passivation layer comprises one or more layers of a non-polymer inorganic material.

15. The method of claim 14, wherein the one or more layers comprise a metal material, a fluoride material, a carbon compound material, a metal oxide material, a nitride material, a boride material, or a combination thereof.

16. The method of claim 15, wherein the metal material comprises Ag (silver), bismuth (Bi), or a combination thereof.

17. The method of claim 15, wherein the fluoride material comprises lithium fluoride (LiF), silver fluoride (AgF), bismuth trifluoride (BiFs), or a combinationthereof, the metal oxide material comprises aluminum oxide (AlxOy), zirconium oxide (ZrxOy), or a combination thereof, the carbon compound material comprises lithium carbonate (Li2CO3), lithium carbide (l_i2C2), or a combination thereof, the nitride material comprises lithium nitride (LisN), and the boride material comprises boron nitride (BN).

18. A battery comprising: a separator stack comprising: a separator film; a metallic lithium (Li) layer disposed on the separator film; and an inorganic passivation layer disposed over the metal Li layer.

19. The battery of claim 18, wherein the inorganic passivation layer comprises one or more layers of a non-polymer inorganic material.

20. The battery of claim 19, wherein the one or more layers comprise a metal material, a fluoride material, a carbon compound material, a metal oxide material, a nitride material, a boride material, or a combination thereof.

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