Method of making and storing silicon-containing anodes for lithium-based energy storage devices

Abstract

A method of making an anode for a lithium-ion energy storage device includes forming a lithium storage layer on a current collector by a PVD or a CVD process. The lithium storage layer includes at least 40 atomic % silicon. The atomic % is relative to a total of non-hydrogen atoms. The lithium storage layer may further include at least one of carbon and nitrogen. A total amount of the carbon and nitrogen is in a range 0.5 – 50 atomic %. The method further includes storing the anode in the presence of air at a temperature in a range of 10 – 30 °C for at least 1 month, wherein the air may optionally have a relative humidity of at least 10%.

Description

METHOD OF MAKING AND STORING SILICON-CONTAINING ANODES FOR LITHIUM-BASED ENERGY STORAGE DEVICES CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 755.729 filed February 7. 2025, entitled “‘METHOD OF MAKING AND STORING SILICON-CONTAINING ANODES FOR LITHIUM-BASED ENERGY STORAGE DEVICES”, the entire contents of which is incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to silicon-based anodes for lithium-ion batteries, and more particularly, silicon-based anodes having improved long-term storage stability.BACKGROUND

[0003] Lithium-ion batteries are a cornerstone of modem portable electronics, electric vehicles, and renewable energy storage systems due to their high energy density and long cycle life. However, the performance of these batteries is largely limited by the materials used in their anodes. Traditionally, graphite has been the material of choice for anodes, offering a stable and reliable option with a storage capacity of around 370 mAh / g. Yet, as the demand for higher capacity and more efficient energy storage solutions grows, the limitations of graphite become more apparent, prompting researchers to explore alternative materials.

[0004] Silicon has emerged as a promising candidate for next-generation lithium-ion battery anodes due to silicon’s significantly higher theoretical capacity of approximately 3600 mAh / g. This potential for increased energy storage is due to silicon's ability to alloy lithium. However, the use of silicon in anodes is not without challenges. The alloying and de-alloying of lithium can cause substantial volume changes in silicon, leading to mechanical stresses that can pulverize the material and degrade the battery's structural integrity. This has spurred interest in developing silicon-based anodes that can withstand these stresses. One common approach has been to mix some silicon particles into the graphite system, which may work at low levels of silicon (a few' w eight %), but higher levels of silicon present numerous manufacturing and performance issues. Thus, this approach has been unable to leverage silicon’s energy storage capacity advantages. Other approaches have focused on nano- and micro-structured silicon to mitigate the pulverization issue. These may allow higher % silicon, but nanowires, microwires, and the like can be difficult to manufacture and aretypically fragile, resulting in higher-cost anodes that are not robust to conventional handling. High surface area silicon nanostructures and particles can make them more prone to surface oxidation reactions that degrade the silicon if stored under ambient conditions.

[0005] Despite these efforts, silicon-based anodes have yet to achieve widespread commercial success, primarily due to unresolved issues related to their mechanical stability , storage stability, and manufacturing complexity.SUMMARY

[0006] There remains a desire for lithium-ion batteries based on silicon anodes that are easy to manufacture, robust to handling, high in charge capacity, and that have good cycle life and long-term storage stability. Examples of this disclosure address these and other needs.

[0007] In accordance with an embodiment of this disclosure, a method of making an anode for a lithium-ion energy storage device includes forming a lithium storage layer on a current collector by a PVD or a CVD process. The lithium storage layer includes at least 40 atomic % silicon, wherein the atomic % is relative to a total of non-hydrogen atoms, and at least one of carbon and nitrogen, wherein a total amount of the carbon and nitrogen is in a range 0.5 - 50 atomic %. The method further includes storing the anode in the presence of air at a temperature in a range of 10 - 30 °C for at least 1 month (e.g., 30 days), wherein the air may optionally have a relative humidity of at least 10%.

[0008] A lithium-ion battery may include an anode made by the methods described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a cross-sectional view of a non-limiting example of an anode.

[0010] FIGS. 2A - 2C are non-limiting examples of chemical composition profiles as a function of thickness T of the lithium storage layer.

[0011] FIG. 3 is a cross-sectional view of another non-limiting example of an anode having multiple sublayers.

[0012] FIGS. 4A - 4C are non-limiting examples of chemical composition profiles as a function of thickness T of the lithium storage layer having multiple sublayers.

[0013] FIG. 5 is a cross-sectional view of a non-limiting example of an anode having a lithium storage layer provided on both sides (two-sided anode).

[0014] FIG. 6 is a schematic cross-sectional view of a non-limiting example of a battery cell.DETAILED DESCRIPTION

[0015] It is to be understood that the drawings are for purposes of illustrating the concepts of the disclosure and may not be to scale. Terms like “overlaying”, “over” or the like include, but do not necessarily require, direct contact (unless such direct contact is noted or clearly required for functionality). Herein, an “average” may represent a mean, median, or mode, and an “average thickness” may be based on at least three measurements. Additional details regarding some features of the present application may in some cases be found in U.S. Patent Application Publication No. 2019 / 0267631, U.S. Patent Application Publication No.2020 / 0411851, U.S. Application Publication No. 2021 / 0050584, U.S. Patent Application Publication No. 2021 / 0057733, U.S. Patent Application Publication No. 2021 / 0057757, U.S. Patent Application Publication No. 2021 / 0057755, U.S. Patent Application Publication No.2021 / 0066702, U.S. Patent Application Publication No. 2023 / 0343968, U.S. Patent Application Publication No. 2023 / 0142782, PCT International Publication Number WO2023 / 113813, U.S. Patent Application Publication No. 2022 / 0344627, PCT International Publication Number WO2023 / 129408, PCT International Publication Number WO2023 / 239599, PCT International Publication number WO2024 / 058845, PCT International Publication number WO2024 / 173383, and PCT International Publication number WO2024 / 173390, the entire contents of which are incorporated herein by reference for all uses.

[0016] This disclosure provides an anode for a lithium-ion energy storage device, e.g.. a lithium-ion battery, having improved storage stability. Lithium-ion batteries (LIBs) of the present disclosure may include an anode, an electrolyte (which may be a liquid or an SSE), and a cathode. FIG. 1 is a cross-sectional view of a non-limiting example of an anode 100. For additional reference, XYZ coordinate axes are also provided. Anode 100 includes a current collector 101 and a lithium storage layer 102 overlaying the current collector. The current collector 101 may include an electrically conductive layer 103 and may in some cases also include a surface layer 105 disposed between the electrically conductive layer 103 and the lithium storage layer 102. The surface layer may have properties that improve adherence or charge transport between the lithium storage layer and the current collector. In some cases, the surface layer may include a metal oxide or an oxometallate as described elsewhere herein. Although the figure shows the surface of the current collector as flat for convenience, the current collector may have a rough surface, e.g., the current collector may be characterized by a surface roughness Ra of > 250 nm. as also discussed elsewhere herein. The electricallyconductive layer 103 may in some cases be a metal foil, potentially including nickel, copper, or a copper alloy as discussed elsewhere herein.

[0017] The lithium storage layer can be deposited onto the current collector by a PVD or CVD process, potentially including PECVD. Such processes are discussed elsewhere herein. In some cases, an ALD process may be used to form some or all of the lithium storage layer, but ALD processes may have lower manufacturing throughput. The lithium storage layer 102 may include at least 40 atomic % silicon and at least one of carbon and nitrogen such that the total amount of carbon and nitrogen in the lithium storage layer is in a range 0.5 - 50 atomic %. That is, in addition to the silicon, the lithium storage layer may include as a “silicon additive’': i) carbon, ii) nitrogen, or iii) both carbon and nitrogen. The lithium storage layer may further include other materials or dopants as discussed elsewhere, but the term “silicon additive” herein refers specifically to carbon, nitrogen, or their combination. Stated another way, the lithium storage layer may include at least 40 atomic % silicon and 0.5 - 50 atomic % of “silicon additive”.

[0018] When carbon is present, it may in some cases be provided in a range of 0.5 to 30 atomic %. The carbon may in some cases not include a substantial amount of methylated silicon, i.e., less than 10% of the total carbon of the lithium storage layer is present in -CH3 functional groups.

[0019] As noted, the lithium storage layer may in some cases be characterized by the atomic percentages (atomic %) of its constituent elements. Herein, the use of “atomic %” when describing a lithium storage layer is generally with respect to the sum total of all atoms in the lithium storage layer other than lithium and hydrogen. That is, lithium and hydrogen are generally excluded from the calculation of the sum total of all atoms in the lithium storage layer. The primary exception is when reporting an atomic % of hydrogen, which does include hydrogen in the sum total of all elements in the lithium storage layer, but which still excludes lithium. For purposes of illustration, if a lithium storage layer includes 100 atoms silicon, 20 atoms carbon, 15 atoms nitrogen, 10 atoms oxygen, 3 atoms phosphorus, 2 atoms boron, 5 atoms hydrogen, and 8 atoms lithium (163 total atoms), the following atomic % would be reported herein: 66.7% Si (excluding H and Li); 13.3% C (excluding H and Li); 10.0% N (excluding H and Li); 6.7% O (excluding H and Li); 2.0% P (excluding H and Li), 1.3% B (excluding H and Li), and 4.5% H (excluding Li). Lithium is generally not reported as an atomic % since it is the material being stored by the layer.

[0020] There is no particular limitation on analytical methods for determining atomic %. For example, most elements may be analyzed by X-ray photoelectron spectroscopy (XPS)(optionally with depth profiling of the anode), inductively coupled plasma-optical emission spectroscopy (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), and / or scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX). In some cases, hydrogen may be analyzed by thermal desorption analysis (TDA), inert gas fusion (IGF), or Raman spectroscopy.

[0021] The combination of nitrogen and silicon in the lithium storage layer 102 may form a substoichiometric nitride (which may be conveniently referred to as SiNx, and which is discussed in more detail elsewhere herein). The combination of silicon with carbon may for convenience referred to herein as SiCx. Whether the silicon includes carbon, nitrogen, or both carbon and nitrogen, an improvement in some performance characteristics have been found such as higher battery cycle life and / or long term (>30 days) storage stability of the anode itself. In particular, it has been unexpectedly found that silicon anodes containing nitrogen, carbon, or both carbon and nitrogen, significantly reduces flaking or peeling of the lithium storage layer from the current collector that may occur during long-term storage under ambient room conditions (e.g.. longer than 30 days in air at a temperature of 10 - 30 °C and relative humidity of at least 10%). In some preferred examples, the SiNx or SiCx is at least present at or near the interface of the current collector with the lithium storage layer.

[0022] Long-term storage in air under ambient room conditions may include placement in a room with a consumer-grade temperature control system and / or UVAC system. The air may not have moisture removed through a dehumidifier or other device. Long-term storage may exclude Class 1, Class 10, or Class 100 systems, and / or systems to maintain laminar air flow. In embodiments, long-term storage may exclude filtration units to remove contaminants include volatile organic compounds. Long-term storage may exclude supplying an inert gas (e.g., Ar or N2). Long-term storage may or may not include storing the anode in packaging or a container. The packaging or container may not be vacuum sealed or airtight. Long-term storage may or may not exclude visual inspections of the anode and associated handling during the storage time. Long-term storage may exclude additional processing of the anode to modify a surface or to connect the anode with other parts of a battery. In some embodiments, long-term storage may mean the anode is not handled at all for the duration.

[0023] The lithium storage layer 102 may in some examples have a relatively constant composition across its total thickness TL with respect to silicon and silicon additive). FIG. 2A is anon-limiting example of a chemical composition profile as a function of thickness T of the lithium storage layer 102 from the current collector 101, e.g., the distance from the current collector measured in a direction that is orthogonal to the plane of the upper surfaceof the current collector (corresponding to the z-axis of FIG. 1). Note that TL may be a single representative measurement, or alternatively, an average of 2 or more measurements taken, e.g., across a 1 mm length (x or y axis in this drawing). There is no particular limitation on how to measure thickness, but in some cases the thickness TL may be measured on a crosssection of the anode using SEM or optical microscopy. With respect to the distance from the current collector, the starting point "0" represents the interface of the lithium storage layer with the current collector, TL is the total thickness of the lithium storage layer, and thickness 0.5*TL represents the half-way point through the lithium storage layer. As shown in FIG. 2 A, the atomic % of silicon additive (denoted “C / N”, dotted-dashed line) and silicon (Si, dashed line) are relatively constant throughout the lithium storage layer. Note that this graph is idealized and there may be some small variability (e.g., ± 5%) and the particular atomic % levels shown are arbitrary and merely illustrative. Also, although not shown, the silicon at the very top surface may be subject to some minor oxidation in air.

[0024] In some other examples, the lithium storage layer 102 may have a variable chemical composition across its thickness T with respect to silicon additive (C / N) and / or silicon. FIG.2B is another non-limiting example of a chemical composition profile as a function of thickness T (distance from current collector 101). In addition to noting thickness T = 0.5*TL, for additional reference, T=0.2*TL is also show n. In this example, the atomic % of C / N gradually decreases as a function thickness whereas the atomic % of Si gradually increases as a function of thickness. This is one example of what may be considered a compositional gradient. Although in some cases the gradient directions may be reversed for one or both of C / N and Si, it has been found that in some cases, it can be beneficial for there to be at least some silicon additive near the current collector (not less than 0.5 atomic %). Such benefit may be with respect to long-term storage stability, cycle life, or energy storage capacity, or some combination of these features. Similarly, it may in some cases be beneficial for there to be more silicon additive nearer the current collector than away from it.

[0025] FIG. 2C is another non-limiting example of a chemical composition profile as a function of thickness T (distance from current collector 101). In this example, the atomic % of C / N abruptly decreases as a function thickness whereas the atomic % of Si abruptly increases as a function of thickness. In this illustration, the change occurs at about 0.28*TL. This is one example of what may be considered a lithium storage layer having multiple sublayers of differing compositions. Although in some cases the abrupt increase / decrease may be reversed for one or both of C / N and Si, it has been found that it may be beneficial for there to be at least some silicon additive in the sublayer near the current collector (not lessthan 0.5 atomic %), or alternatively, that there may be more silicon additive in the sublay er near the current collector than in the sublayer away from it. Such benefit may be with respect to long-term storage stability7, cycle life, or energy storage capacity, or some combination of these features.

[0026] Referring again to FIG. 1, in some cases, the lithium storage layer may be characterized by a lower portion 107 (adjacent to the current collector 101) and an upper portion 109 positioned away from the current collector, such that the lower portion 107 has a higher atomic % of silicon additive than the upper portion 109. In some examples, the ratio of atomic % of silicon additive in the upper portion relative to the lower portion is in a range of 0 - 0.8, or alternatively in a range of 0 - 0.5. Optionally, the lower portion 107 may also have a lower atomic % of Si than the upper portion 109. In some cases, the ratio of the atomic % of silicon in the upper portion relative to the lower portion is in a range of 1 - 2.2, or alternatively in a range of 1.1 - 1.8. Line 108 may in some cases represent an arbitrary boundary line for measurement purposes, below which is considered the lower portion, and above which is considered the upper portion. The position of line 108 may be provided at Z*TL, wherein z is a value in a range from 0.05 up to and including 0.95. That is, the lower portion may correspond to the lithium storage layer from T=0 up to Z*TL and the upper portion corresponds to the lithium storage layer between Z*TL and TL. Some convenient, but non-limiting, values of z may be 0.2 or alternatively 0.5. For example, and with reference to FIGS. 2B and 2C, whether measured at 0.2*TL or 0.5*TL. the lower portion 107 clearly has a higher overall atomic % C / N (integrated total % C / N from T=0 to 0.2*TL or from T=0 to 0.5*TL) than the atomic % C / N in the upper portion 109 (integrated total % C / N between 0.2*TL and T or between 0.5*TL and TL). Similarly, the lower portion 107 has a lower overall atomic % Si (integrated total % Si from T=0 to 0.2*T or from T=0 to 0.5*TL) than the atomic % Si in the upper portion 109 (integrated total % Si between 0.2*T and T or between 0.5*T and TL). The same can be said for nearly any selection of z chosen in a range from 0.05 up to and including 0.95, but 0.2 or 0.5 are convenient reference points.

[0027] In the case of FIG. 2C, the abrupt change in composition occurs at about 0.28*T and one may consider a lower portion from T=0 to 0.28*TL to be a first sublayer and a second sublayer corresponds to an upper portion between 0.28*TL and TL. That is, the term “sublayer” is used when there is a distinct change in composition profile over a small thickness range (e.g., on the order of a few hundred nanometers or less). The distinct change may be an absolute atomic percent change of over 10%. 20%. 30%. 40%. or 50%. The distinct change may be a shift in the first derivative or second derivative of the atomic percentover the thickness. FIG. 3 is a cross-sectional view of a non-limiting example of another anode 300. Anode 300 may include a current collector 301 and a lithium storage layer 302 overlaying the current collector. The current collector 301 may include an electrically conductive layer 303 and may in some cases include a surface layer 305 interposed between the electrically conductive layer 303 and the lithium storage layer 302. Anode 300 may be analogous to anode 100, but in this case, there is shown a distinct layer boundary 308 between a first sublayer 307 and a second sublayer 309 overlaying the first sublayer, wherein the second sublayer has a different composition than first sublayer. In some examples, the first sublayer may include at least 40 atomic % silicon and 0.5 - 50 atomic % of silicon additive, whereas the second sublayer may also include at least 40 atomic % silicon (optionally higher than the first sublayer), but relative to the first sublayer, may have less silicon additive (or no silicon additive). In some examples, the ratio of atomic % of silicon additive in the second sublayer relative to the first sublayer is in a range of 0 - 0.8, or alternatively in a range of 0 - 0.5. In some cases, the ratio of the atomic % of silicon in the second sublayer relative to the first sublayer is in a range of 1 - 2.2, or alternatively in a range of 1.1 - 1.8. In some preferred cases, both the first and second sublayers may be deposited by a PVD or CVD process, optionally a PECVD process. In some other cases, the first sublayer may be deposited by one of these processes and the second sublayer may instead be coated from a slurry, e.g., a slurry containing silicon-containing particles and a carbon-based binder.

[0028] The shift in chemical composition between the first and second sublayers may in some cases be similar to that shown in FIG. 2C, but numerous alternative distinct changes or boundaries may be observed. FIG. 4A is anon-limiting composition profile where the first sublayer 307 has a fairly uniform composition through its thickness and the second sublayer 309 has a gradient composition, but one can still observe the distinct change at layer boundary7308. FIG. 4B is another non-limiting composition profile, in this case where the first sublayer 307 has a compositional gradient over its thickness and the second sublayer 309 has a relatively uniform composition, but one can still observe the distinct change at layer boundary 308. In yet another non-limiting example. FIG. 4C is a composition profile where both the first and second sublayers have gradients, but there is still a distinct layer boundary 308. Although not shown, in some cases, a layer boundary may be identified by a second derivative analysis of the composition profile, i.e., by calculating the change in slope as a function of T.

[0029] In some examples, the first sublayer may be thinner than the second sublayer. In some cases, the first sublayer may have a thickness of just a few monolayers, alternatively, a thickness in a range of 10 - 100 nm, 100 - 500 nm, 500 - 1000 nm, 1000 - 2000 nm, 2000 -3000 nm, or any combination of ranges thereof. Alternatively, the first sublayer may be thicker than the second sublayer. In some cases, the second sublayer may have a thickness of just a few monolayers, alternatively, a thickness in a range of 10 - 100 nm, 100 - 500 nm, 500 - 1000, 1000 - 2000 nm, 2000 - 3000 nm, or any combination of ranges thereof. In some examples, the sublayers may have approximately the same thickness.

[0030] Although not illustrated, the compositional profile of the lithium storage layer can have more than the two sublayers shown in FIG. 3 and / or have a gradient profile that is more complex than shown in FIG. 2B. Although not illustrated, if both carbon and nitrogen are used, their ratio may stay the same throughout the lithium storage layer, or alternatively, the ratio may vary.

[0031] In some examples, the lithium storage layer may further include hydrogen, e.g., in a range of 0.1 - 25 atomic %. When the lithium storage layer is formed from a CVD or PECVD process, the presence of hydrogen may be from hydrogen atoms in a precursor gas (e.g. silane) or from H2 gas. In some cases, the lithium storage layer may further include 0.1 -20 atomic % oxygen. The optional oxygen may be co-deposited with silicon and silicon additive. When the optional oxygen is not provided uniformly throughout the lithium storage layer, it may be beneficial in some cases that it be provided in an amount that is less at or near the current collector, e.g., in the lower portion or first sublayer, than in the second portion or second sublayer.

[0032] In some particularly useful examples, the lithium storage layer is deposited by a CVD or PECVD process. These processes described elsewhere herein and generally involve exposing a substrate (which includes the current collector) to a reactive precursor gas in a deposition chamber that may include a gaseous plasma. The substrate may be the current collector itself, or in some cases, the substrate may include the current collector with a portion or sublayer of the lithium storage layer already applied and the deposition is over the pre-existing portion or sublayer. For example, the deposition process may involve exposing the substrate to a silicon precursor gas, which may include silane, dichlorosilane, monochlorosilane, trichlorosilane, silicon tetrachloride, disilane, tetrafluorosilane, triethylsilane, diethylsilane, or any combination thereof. The silicon precursor gas may optionally include a molecule with at least one silicon atom and at least one nitrogen atom, e.g., hexamethyldisilazane (HMDS) which may result in depositing both silicon and nitrogen,or a molecule with at least one silicon atom, at least one nitrogen atom, and at least one oxygen atom, e.g., hexamethyldisiloxane (HMDSO) which may result in depositing silicon, nitrogen, and oxygen. The silicon precursor gas may optionally include a molecule with at least one silicon atom and at least one carbon atom, e.g., diethylsilane, methyltrichlorosilane, or silacyclobutane, which may result in depositing both silicon and carbon. The silicon precursor gas may optionally include a molecule with at least one silicon atom, at least one carbon atom, and at least one nitrogen atom, e.g., methyltris(diethylamino)silane, which may¬ result in depositing silicon, carbon, and nitrogen.

[0033] The CVD / PECVD process may further involve exposing the substrate to a nitrogen precursor gas, which may include N2, ammonia, an organic amine, or any combination thereof. The process may involve exposing the substrate to a carbon precursor gas, which may include a compound having 1 - 5 carbon atoms in an alkane, alkene, or alkyne, that is optionally substituted with one or more substituents including a halogen atom, a nitrogen atom, or an oxygen atom. In some cases, methane is a suitable carbon precursor gas, but it is deposited under conditions to avoid substantial methylated silicon. The process may also involve exposing the substrate to an oxygen precursor gas, for example, O2, ozone, TEOS (tetraethyl orthosilicate), nitrous oxide, or water. Other non-precursor gases may be introduced into a deposition chamber, e.g., when forming a plasma in PECVD, such as helium, argon, xenon, or the like. Note that the precursor gases mentioned above, when introduced into a gaseous plasma used in PECVD, may be in their original form and / or as a gaseous reaction product (e.g., ionized or in some other partially transformed state that leads to deposition onto the substrate).

[0034] Compositional gradients, sublayers, or the like in the lithium storage layer may be made by adjusting the deposition conditions. In the case of PVD, e.g., sputtering, it may be done by changing targets or the intensity of sputtering from one target versus another. In the case of CVD or PECVD, it may be done by changing the precursor gases or other gases, their flow rates, the deposition temperature, pre-heating time / temperature, pressure, substrate bias, location of inlet gases, the plasma power, plasma generation type (capacitive, inductive, remote, or the like). In some cases, a sublayer may be formed in one deposition tool and another sublayer may be formed in a second deposition tool. Alternatively, the deposition conditions may be altered in situ within the same tool, for example, without breaking vacuum or exposing to air.

[0035] For most applications, the lithium storage layer generally has a thickness TL that is at least 100 nm and preferably at least 500 nm. In some cases, TL may be in a range of 500 nm -1000 nm. 1000 nm - 2 pm, 2 - 5 pm, 5 - 10 pm, 10 - 15 pm, 15 - 20 pm, 20 - 30 pm, 30 -40 pm, 40 - 50 pm, or any combination thereof.

[0036] For many applications, a lithium storage layer may be provided on both sides of the current collector. For example, FIG. 5 is a cross-sectional view of anon-limiting example of a two-sided anode. The current collector 501 may include electrically conductive layer 503 and may also include surface layers (505a, 505b) provided on either side of the electrically conductive layer 503. Lithium storage layers (507a, 507b) are disposed on both sides to form anode 500. In some cases, at least one of the silicon-containing lithium storage layers is deposited by a PVD or CVD (optionally PECVD) process. Surface layers 505a and 505b (if present) may be the same or different with respect to composition, thickness, roughness or some other property. Similarly, lithium storage layers 507a and 507b may be the same or different with respect to composition, thickness, porosity or some other property. At least one, or alternatively both, of the lithium storage layers is as described above with respect to any of FIGS. 1 - 4C. In some cases, one lithium storage layer is deposited by a slurry7coating method and may have less than 40 atomic % silicon or even no silicon. In some cases, one of the lithium storage layers includes nanostructures, e.g., silicon nano wires. In some cases, both silicon-containing lithium storage layers are deposited by a PVD or CVD (optionally a PECVD) process.

[0037] Current collector

[0038] In some examples the electrically conductive layer may have a conductivity of at least 103S / m, or alternatively at least 106S / m, or alternatively at least 107S / m, and may include inorganic or organic conductive materials or a combination thereof. Higher conductivity is generally preferred, but practically, most commercially viable electrically conductive materials have a conductivity7of less than 108S / m. For anodes having low capacity and / or w here there are no concerns regarding anode deformation during use, a w ide variety of conductive materials may be used as the electrically7conductive layer.

[0039] In some examples, the electrically7conductive layer includes a metallic material, e.g., titanium (and its alloys), nickel (and its alloys), copper (and its alloys), or stainless steel. In some examples, even metals that may normally react or alloy with lithium, e.g., tin or aluminum, may be suitable if the surface layer is sufficiently protective. In some examples, the electrically conductive layer may include a multilayer structure, e.g., include multiple lay ers of metal. In some examples, the electrically conductive layer may be a clad foil. In some examples, the electrically conductive layer includes an electrically conductive carbon, such as carbon black, carbon nanotubes, graphene, graphene oxide, reduced graphene oxide.and graphite. In some examples the electrically conductive layer may be in the form of a foil, a mesh, a fiber, a fabric, or sheet of conductive material. Herein, a “mesh” includes any electrically conductive structure having openings such as found in interwoven wires, foam structures, foils with an array of holes, or the like. In some examples, the electrically conductive layer may include multiple layers of different electrically conductive materials. The electrically conductive layer may be in the form of a layer deposited onto an insulating substrate (e.g., a polymer sheet or ceramic substrate coated with a conductive material, including but not limited to, nickel or copper, optionally on both sides). In some examples, the electrically conductive layer includes a mesh or sheet of electrically conductive carbon, including but not limited to, those formed from bundled carbon nanotubes or nanofibers, or carbon fiber or fabric.

[0040] When higher tensile strength is desired, e.g., where Rmis greater than 450 MPa, alternatively greater than 500 MPa, alternatively greater than 550 MPa, or alternatively greater than 600 MPa, the electrically conductive layer may include nickel (and certain alloys), or certain copper alloys, such as brass (an alloy primarily of copper and zinc), bronze (an alloy primarily of copper and tin), CuMgAgP (an alloy primarily of copper, magnesium, silver, and phosphorous), CuFe2P (an alloy primarily of copper, iron, and phosphorous), CuNi3Si (an alloy primarily of copper, nickel, and silicon), CuCrZr (an alloy primarily of copper, chromium, and zirconium), and CuCrSiTi (an alloy primarily of copper, chromium, silicon, and titanium). The nomenclature for the metal alloys is not the stoichiometric molecular formula used in chemistry but rather the nomenclature used by those of ordinary’ skill in the alloy arts. For example, CuNi3Si does not mean there are three atoms of nickel and one atom of silicon for each atom of copper. In some examples these nickel- or copperbased higher tensile electrically conductive layers may include roll-formed nickel or copper alloy foils. While there is no particular upper limit, many commercially viable high tensile strength electrically conductive layers may have Rmin a range of 500 - 1200 MPa. In some cases, tensile strength may be measured according to ISO 6892, but other standards or techniques may be used.

[0041] Alternatively, a mesh or sheet of electrically conductive carbon, including but not limited to, those formed from bundled carbon nanotubes or nanofibers, may in some cases provide for higher tensile strength electrically conductive layers. In some examples, an electrically conductive metal interlayer may be interposed between the electrically conductive carbon and an optional surface layer.

[0042] In some examples, any of the above-mentioned electrically conductive layers (low or high tensile strength) may act as a primary electrically conductive layer and further include an electrically conductive interlayer, e.g., a metal interlayer, disposed between the primary electrically conductive layer and the surface layer.

[0043] General surface roughness

[0044] In some examples, the current collector may be characterized as having a surface roughness, e.g., as measured by contact profilometry, optical profilometry, atomic force microscopy, or the like. Herein, surface roughness comparisons and measurements may be made using the Roughness Average (Ra), RMS Roughness (Rq), Maximum Profile Peak Height roughness (Rp), Average Maximum Height of the Profile (Rz), or Peak Density (Pc). In some cases, surface roughness measurements may comply with ISO 21920, but other standards and techniques may be used. In some examples, the current collector may be characterized as having both a surface roughness Rz> 2.5 pm and a surface roughness Ra> 0.25 pm. In some examples, Rzis in a range of 2.5 - 3.0 pm, alternatively 3.0 - 3.5 pm, alternatively 3.5 - 4.0 pm, alternatively 4.0 - 4.5 pm, alternatively 4.5 - 5.0 pm, alternatively 5.0 - 5.5 pm, alternatively 5.5 - 6.0 pm, alternatively 6.0 - 6.5 pm. alternatively 6.5 - 7.0 pm, alternatively 7.0 - 8.0 pm, alternatively 8.0 - 9.0 pm, alternatively 9.0 to 10pm, 10 to 12 pm, 12 to 14 pm or any combination of ranges thereof. In some examples, Rais in a range of 0.25 - 0.30 pm, alternatively 0.30 - 0.35 pm, alternatively 0.35 - 0.40 pm, alternatively 0.40 - 0.45 pm, alternatively 0.45 - 0.50 pm, alternatively 0.50 - 0.55 pm, alternatively 0.55 -0.60 pm, alternatively 0.60 - 0.65 pm, alternatively 0.65 - 0.70 pm, alternatively 0.70 - 0.80 pm, alternatively 0.80 - 0.90 pm, alternatively 0.90 - 1.0 pm, alternatively 1.0 - 1.2 pm, alternatively 1.2 - 1.4 pm, or any combination of ranges thereof.

[0045] In some examples, some or most of the surface roughness of the current collector may be imparted by the electrically conductive layer and / or an optional metal interlayer.Alternatively, some or most of the surface roughness of the current collector may be imparted by the optional surface layer. Alternatively, some combination of the electrically conductive layer, metal interlayer, and surface layer may contribute substantially to the surface roughness.

[0046] In some examples, the electrically conductive layer may include roughening features, e.g., electrodeposited roughening features, to increase surface roughness. In some examples, the electrodeposited roughening features may include copper features. Current collector roughening features may in some cases take the form of nodules, hemispheroids, nanopillars, dendrites, or the like.

[0047] Alternatively, or in combination with the roughening features, the electrically conductive layer may undergo another electrochemical, chemical, or physical treatment to impart a desired surface roughness prior to formation of the surface layer.

[0048] In some examples, roughening of the electrically conductive layer may include, for example, physical abrasion (such as sandpaper, sand blasting, polishing, or the like), ablation (such as by laser ablation), embossing, stamping, casting, imprinting, chemical treatments, electrochemical treatments, or thermal treatments. In some cases, such roughening may be used to form one or more of the roughening features described above, e.g., nodular features, nanopillar features, broad roughness features, pitted features or the like. In some cases, roughening features may be random, or alternatively, may be patterned.

[0049] Surface layer

[0050] In some examples, a surface layer may provide a chemical composition that promotes formation of an adherent lithium storage layer, such as a lithium storage layer deposited by a CVD or PVD process, particularly at commercially useful loadings or thicknesses of the lithium storage layer. In some cases, deposition onto an electrically conductive layer alone may be insufficient to provide even initial adhesion such that the lithium storage layer material readily brushes or peels off. Even when there is satisfactory initial adherence, it may be insufficient during electrochemical formation and cycling. Some non-limiting examples of surface layers are discussed below. In some cases, a surface layer may include two or more distinct surface sublayers having different chemical compositions. In some cases, a surface layer or even a surface sublayer may include a mixture of different surface layer materials.

[0051] The thickness of a surface layer may be as low as a monolayer in some examples. In some examples, the thickness of the surface layer is in a range of 0.0002 pm to 0.0005 pm, alternatively 0.0005 pm to 0.001 pm, alternatively 0.001 pm to 0.005 pm, alternatively 0.002 pm to 0.005 pm, alternatively, 0.005 pm to 0.01 pm, alternatively 0.01 pm to 0.02 pm, alternatively 0.02 pm to 0.03 pm, alternatively 0.03 pm to 0.05 pm, alternatively 0.05 pm to 0.1 pm, alternatively 0.1 pm to 0.2 pm, alternatively 0.2 pm to 0.5 pm, alternatively 0.5 pm to 1 pm, alternatively 1 pm to 2 pm. alternatively 2 pm to 5 pm or any combination of ranges thereof.

[0052] In some examples, the surface layer or sublayer may include a metal-oxygen compound. In some cases, a metal-oxygen compound may include a metal oxide or metal hydroxide, e.g., a transition metal oxide or a transition metal hydroxide. In some cases, a metal-oxygen compound may include an oxometallate, e.g.. a transition oxometallate. In some examples, a surface layer may include a silicon compound including or derived from asiloxane, a silane (i.e., a silane-containing compound), a silazane, or a reaction product thereof. Herein, a ‘“silicon compound” does not include simple elemental silicon such as amorphous silicon or substoichiometric silicon nitride. In some examples, a surface layer may include a silicate compound. In some examples, a surface layer may include a metal silicide, e.g., a transition metal silicide. In some examples, a surface layer may include a metal chalcogenide such as a metal sulfide, e.g., a transition metal sulfide.[0053 J Lithium Storage Layer

[0054] The lithium storage layer (or in some cases, a first sublayer of the lithium storage layer) includes at least 40 atomic % silicon and 0.5 - 50 atomic % of the silicon additive (carbon, nitrogen, or if both are present, their total), and optionally 0.1 - 25 atomic % hydrogen, and generally has a thickness T of at least 100 nm and preferably at least 500 nm. In particular, the lithium storage layer (or first sublayer) may include: i) silicon in a range of 40 - 50 atomic %, 50 - 60 atomic %, 60 - 70 atomic %, 70 - 80 atomic%, 80 - 90 atomic %, 90 - 95 atomic %, 95 - 98 atomic %, or any combination of ranges thereof; and ii) silicon additive in a range of 0.5 - 1 atomic %, 1 - 5 atomic %. 5 - 10 atomic %, 10 - 15 atomic %, 15 - 20 atomic %, 20 - 25 atomic %, 25 - 30 atomic %. 30 - 35 atomic %, 35 - 40 atomic %, 40 - 45 atomic %, 45 - 50 atomic %, or any combination of ranges thereof. In some cases, the lithium storage layer may further include hydrogen in a range of 0.1 - 0.5 atomic %, 0.5 - 1 atomic %, 1 - 5 atomic %, 5 - 10 atomic %, 10 - 15 atomic %, 15 - 20 atomic %, 20 - 25 atomic %, or any combination of ranges thereof. In some cases, the lithium storage layer may further include oxygen in a range of 0.1 - 0.5 atomic %, 0.5 - 1 atomic %, 1 - 5 atomic %, 5 - 10 atomic %, 10 - 15 atomic %, or 15 - 20 atomic %, or any combination of ranges thereof. Preferably, the amount oxygen is less than 15 atomic % or less than 10 atomic %.

[0055] The lithium storage layer may be deposited by a PVD process or a CVD process (which may include PECVD) and is generally substantially free of carbon-based polymeric binders used in conventional anodes that use silicon particles. Some common carbon-based polymeric binders may, for example, include poly vinylidene fluoride (PVDF), polyacrylic acid (PAA), carboxy methyl cellulose (CMC), alginate (Alg), polymerized styrene butadiene rubber (SBR), polyvinyl alcohol (PVA). chitosan (CS), carboxymethyl chitosan, polyacrylonitrile (PAN), polyimide (PI), gum Arabic (GA), guar gum (GG), gelatin, to name a few. By “free of carbon-based binders” it is meant that the lithium storage layer has a weight percentage of carbon-based binders in a range of 0 to 1% (w / w), or alternatively 0 to 0.5% (w / w), or alternatively 0 to 0.1% (w / w).

[0056] In examples having a first sublayer and second sublayer, the second sublayer may also include at least 40 atomic % silicon (optionally higher than the first sublayer), but relative to the first sublayer, may in some cases have more or less silicon additive (or no silicon additive). In some examples, the ratio of atomic % of silicon additive in the second sublayer relative to the first sublayer may be in a range of 0 - 0.1, 0.1 - 0.2, 0.2 - 0.3, 0.3 - 0.4, 0.4 -0.5, 0.5 - 0.6, 0.6 - 0.7, 0.7 - 0.8, 0.8 - 0.9, 0.9 - 1.0, 1.0 - 1.1. 1.1 - 1.2, 1.2 - 1.5, 1.5 - 2.0, or any combination of ranges thereof. In some cases, the ratio of the atomic % of silicon in the second sublayer relative to the first sublayer is in a range of 0.7 - 0.8, 0.8 - 0.9, 0.9 - 1.0, 1.0 - 1.1, 1.1 - 1.2, 1.2 - 1.3, 1.3 - 1.4, 1.4 - 1.6, 1.6 - 1.8, 1.8 - 2.0, 2.0 - 2.2, or any combination of ranges thereof.

[0057] In some cases, before any cycling in a battery, at least some of the lithium storage layer may optionally include a substoichiometric nitride of silicon SiNx. It is noted that, during cycling in a battery, a portion of the SiNx may eventually form other materials such as Si3N4, Li3N, and Li2SiN2.

[0058] A substoichiometric nitride of silicon (SiNx) may have a ratio of nitrogen atoms to silicon that is less than or equal to 1.25:1, e.g., x < 1.25. In some examples, x is in a range of 0.02 to 0.95, alternatively 0.02 to 0.10, alternatively 0.10 to 0.20, alternatively 0.20 to 0.30, alternatively 0.30 to 0.40, alternatively 0.40 to 0.50, alternatively, 0.50 to 0.60, alternatively 0.60 to 0.70, alternatively 0.70 to 0.80, alternatively 0.80 to 0.90, alternatively 0.90 to 0.95, alternatively 0.95 to 1.10, alternatively 1.10 to 1.25, or any combination of ranges thereof.

[0059] In some cases, the majority of the silicon or (SiNx or SiCx) of the lithium storage layer is in an amorphous (non-crystalline) state, e.g., at least 50% of silicon or (SiNx or SiCx) are amorphous, alternatively at least 60%, alternatively, at least 70%, or alternatively at least 80% (wherein % here refers to amorphous silicon vs total Si (excluding SiNx and SiCx), or to amorphous SiNx vs total SiNx, or to amorphous SiCx vs total SiCx, e.g., as measured by weight or some other comparable measurement).

[0060] The lithium storage layer may include voids or interstices (pores), which may be random or non-uniform with respect to size, shape, and distribution. Pores may sometimes collectively form random nano-pathways within the lithium storage layer that may extend to the surface. In some examples, the effective or specific surface area of the lithium storage layer (e.g., as measured by BET) may be between 2 - 10 m2 / g, alternatively 6 - 10 m2 / g, alternatively 10 - 20 m2 / g, alternatively 20 - 50 m2 / g, alternatively 50 - 100 m2 / g. Such porosity generally does not result in. or result from, the formation of any recognizable high aspect ratio lithium storage nanostructures such as nanowires, nanopillars, or the like. Insome examples, the pores may be poly disperse. In some examples, the lithium storage layer, e.g., a continuous porous lithium storage layer, may be characterized as nanoporous.

[0061] In some examples, the majority of active material of the lithium storage layer has substantial lateral connectivity across portions of the current collector, such connectivity extending around random pores and interstices. This may be referred to as a continuous porous lithium storage layer. In some examples, the porous lithium storage layer may be described as a matrix of interconnected silicon (or SiNx or SiCx) with random pores and interstices embedded therein. In some examples, the lithium storage layer, e g., a continuous porous lithium storage layer, may in a cross-sectional view have a sponge-like form. It should be noted that the lithium storage layer, e.g., a continuous porous lithium storage layer, does not necessarily extend across the entire anode without any lateral breaks and may include random discontinuities or cracks and still be considered continuous. In some examples, such discontinuities may occur more frequently on rough current collector surfaces. In some examples, the lithium storage layer, e.g., a continuous porous lithium storage layer, may in a cross-sectional view have abutting columns of active material such as silicon, generally with a height / width aspect ratio of less than 2: 1.

[0062] The desired areal charge capacity of the anode depends in part on the intended use. For many conventional uses, the anode charge capacity may be at least 1 mAh / cm2, alternatively at least 2 mAh / cm2, alternatively at least 3 mAh / cm2, alternatively at least 4 mAh / cm2, alternatively at least 5 mAh / cm2, or alternatively at least 6 mAh / cm2. In some cases, the anode charge capacity may be in a range of 1 - 2 mAh / cm2, 2 - 3 mAh / cm2, 3 - 4 mAh / cm2, 4 - 5 mAh / cm2, 5 - 6 mAh / cm2, 6 - 8 mAh / cm2, 8 - 10 mAh / cm2, or 10 - 15 mAh / cm2, or any combination of ranges thereof. Some microbattery applications may have lower capacities than those listed above, e g., in a range of 0.01 - 0.05 mAh / cm2. 0.05 - 0.10 mAh / cm2, 0.10 - 0.5 mAh / cm2, or 0.5 - 1.0 mAh / cm2, or any combination of ranges thereof.

[0063] CVD

[0064] CVD generally involves flowing a precursor gas, a gasified liquid in terms of direct liquid injection CVD or gases and liquids into a chamber containing one or more objects, typically heated, to be coated. Chemical reactions may occur on and near the hot surfaces, resulting in the deposition of a thin film on the surface. This is accompanied by the production of chemical by-products that are exhausted out of the chamber along with unreacted precursor gases. As would be expected with the large variety of materials deposited and the wide range of applications, there are many variants of CVD that may be used to form the lithium storage layer, the surface layer or sublayer, a supplemental layer (see below) orother layers. It may be done in hot-wall reactors or cold-wall reactors, at sub-torr total pressures to above-atmospheric pressures, with and without carrier gases, and at temperatures typically ranging from 100 - 1600 °C in some examples. There are also a variety of enhanced CVD processes, which involve the use of plasmas, ions, photons, lasers, hot filaments, or combustion reactions to increase deposition rates and / or lower deposition temperatures. Various process conditions may be used to control the deposition, including but not limited to, temperature, precursor material, gas flow rate, pressure, substrate voltage bias (if applicable), and plasma energy (if applicable).

[0065] As mentioned, a lithium storage layer such as a continuous porous lithium storage layer, e.g., a layer of silicon or germanium or both, may be provided by plasma-enhanced chemical vapor deposition (PECVD). Relative to conventional CVD, deposition by PECVD can often be done at lower temperatures and higher rates, which can be advantageous for higher manufacturing throughput. In some examples, the PECVD is used to deposit a substantially amorphous lithium storage layer over the surface layer.

[0066] In PECVD processes, according to various implementations, a plasma gas may be generated in a chamber in which the substrate is disposed or upstream of the chamber and fed into the chamber. Various types of plasmas may be used including, but not limited to, capacitively -coupled plasmas, inductively-coupled plasmas, and conductive coupled plasmas. Any appropriate plasma source may be used, including DC, AC, RF, VHF, combinatorial PECVD and microwave sources may be used. In some examples, magnetron assisted RF PECVD may be used.

[0067] PECVD process conditions (temperatures, pressures, precursor gases, carrier gases, dopant gases, flow rates, energies, and the like) can vary according to the particular process and tool used, as is well known in the art.

[0068] In some implementations, the PECVD process is an expanding thermal plasma chemical vapor deposition (ETP -PECVD) process. In such a process, a plasma generating gas is passed through a direct current arc plasma generator to form a plasma, with a web or other substrate including the current collector optionally in an adjoining vacuum chamber. A silicon source gas is injected into the plasma, with radicals generated. The plasma is expanded via a diverging nozzle and injected into the vacuum chamber and toward the substrate. An example of a plasma generating gas is argon (Ar). In some examples, the ionized argon species in the plasma collide with silicon source molecules to form radical species of the silicon source, resulting in deposition onto the current collector. Exampleranges for voltages and currents for the DC plasma source are 60 to 80 volts and 40 to 70 amperes, respectively.

[0069] In PECVD or CVD, the lithium storage layer is formed on a substrate by reaction of one or more precursor gases. Some non-limiting examples of silicon-, nitrogen-, carbon-, and oxygen-precursor gases are disclosed elsewhere herein. Depending on the gas(es) used, the lithium storage layer may be formed by decomposition or reaction with another compound, such as by hydrogen reduction. In some examples, the gases may include the desired reactive precursor gas (silicon-, nitrogen-, carbon-, etc ), optionally hydrogen, and optionally a noble gas such as helium, argon, neon, or xenon. Additional gases may be introduced to dope the lithium storage layer with another element including, but not limited to, boron, phosphorous, sulfur, fluorine, aluminum, gallium, indium, arsenic, antimony, yttrium, scandium, bismuth, or the like (e.g., at less than 5 atomic %).

[0070] Other anode features

[0071] The anode may optionally include various additional layers and features. The current collector may include one or more features to ensure that a reliable electrical connection can be made in the energy storage device. In some examples, a supplemental layer is provided over the lithium storage layer. In some examples, the supplemental layer is a protection layer to enhance lifetime or physical durability. In some examples, the supplemental layer may improve wetting of a liquid electrolyte, or alternatively, the coatability of the SSE to improve interfacial contact and / or cycling performance. A supplemental layer may be deposited, for example, by ALD, S-ALD, CVD, i-CVD, PECVD, MLD, evaporation, sputtering, solution coating, inkjet or any method that is compatible with the anode. In some examples, the top surface of the supplemental layer may correspond to a top surface of the anode. In some examples, two or more supplemental layers may be used together.

[0072] A supplemental layer should be reasonably conductive to lithium ions, i.e., permit lithium ions to move into and out of the lithium storage layer during charging and discharging. In some examples, the lithium ion conductivity of a supplemental layer is at least 10’9S / cm, alternatively at least 10'8S / cm, alternatively at least 10'7S / cm, alternatively at least 10‘6S / cm. A supplemental layer generally has low electrical conductivity and does not reversibly store lithium (i.e., it is generally not an active lithium storage layer material).

[0073] Some non-limiting examples of materials used in a supplemental layer include metal oxides, nitrides, or oxynitrides, e.g., those containing aluminum, titanium, vanadium, zirconium, hafnium, or tin, or mixtures thereof. The metal oxide, metal nitride or metal oxynitride may include other components such as phosphorous or silicon. In some examples,a supplemental layer may include an inorganic-organic hybrid structure having alternating sublayers of metal oxide and bridging organic materials such as so-called ‘“metalcone” materials (e.g., zincone, titanicone, or zircone). The supplemental layer may include a lithium-containing material such as lithium phosphorous oxynitride (LIPON), lithium phosphate, lithium aluminum oxide, LLZO, LATP, (Li,La)xTiyOz, or LixSiyAhCh (where x, y, and z are not zero). In some cases, the supplemental layer may be an ionically conductive organic polymer. The thickness of a supplemental layer may be in a range of 0.2 - 0.5 nm. alternatively 0.5 - 1.0 nm, 1 - 2 nm, 2 - 5 nm, 5 - 10 nm, 10 - 20 nm, 20 - 50 nm, 50 - 100 nm, or any combination of ranges thereof, or even in some cases thicker than 100 nm. The suitable thickness may depend in part on the lithium-ion conductivity of the supplemental layer. When the supplemental layer is predominantly inorganic in nature, it preferably has a thickness of 100 nm or less.

[0074] In some examples, the lithium storage layer may be at least partially prelithiated prior to battery assembly. That is, some lithium may be incorporated into the lithium storage layer to form a lithiated storage structure even prior to the first battery cycle. Note that “lithiated storage layer” simply means that at least some of the potential storage capacity of the lithium storage layer is filled, but not necessarily all. In some examples, the lithiated storage layer may include lithium in a range of 1% to 5% of the theoretical lithium storage capacity of the lithium storage layer, alternatively 5% to 10%, alternatively 10% to 15%, alternatively 15% to 20%, alternatively, 20% to 30%, alternatively 30% to 40%, alternatively 40% to 50%. alternatively 50% to 60%, alternatively 60% to 70%, alternatively 70% to 80%, alternatively 80% to 90%, alternatively 90% to 100%, or any combination of ranges thereof.

[0075] In some examples the anode may be thermally treated prior to battery assembly. In some examples, thermally treating the anode may improve adhesion of the various layers or electrical conductivity, e.g., by inducing migration of metal from the current collector or atoms from the optional supplemental layer into the lithium storage layer.

[0076] In some cases, the anode may be electrochemically treated prior to battery' assembly. For example, the anode may be subjected to some electrochemical cycling in a lithium-containing electrolyte followed by assembly into a battery. In some cases, the lithium-containing electrolyte may be a prelithiation solution and the electrochemical treatment may include prelithiation where lithium ion is electrochemically reduced at, and incorporated into, the anode.

[0077] In some examples one or more processing steps described above may be performed using roll-to-roll methods wherein the electrically conductive layer or current collector is in the form of a rolled fdm, e.g., a roll of metal foil, mesh or fabric.

[0078] Electrolyte

[0079] The nonaqueous lithium-ion electrolyte may be a liquid, a solid, or a gel, or some multi-phase combination. A typical liquid electrolyte includes one or more solvents and one or more salts, at least one of which includes lithium. During the first few charge cycles (sometimes referred to as formation cycles), the organic solvent and / or the electrolyte may partially decompose on the negative electrode surface to form an SEI (Solid-Electrolyte-Interphase) layer. The SEI is generally electrically insulating but ionically conductive, thereby allowing lithium ions to pass through. The SEI may lessen decomposition of the electrolyte in the later charging cycles.

[0080] Some non-limiting examples of non-aqueous solvents suitable for some lithium ion cells include the following: cyclic carbonates (e.g., ethylene carbonate (EC), fluoroethylene carbonate (FEC). propylene carbonate (PC), butylene carbonate (BC) and vinylethylene carbonate (VEC)), vinylene carbonate (VC), lactones (e.g., gamma-butyrolactone (GBL), gamma-valerolactone (GVL) and alpha-angelica lactone (AGL)), linear carbonates (e.g., dimethyl carbonate (DMC), methyl ethyl carbonate (MEC, also commonly abbreviated EMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC), methyl butyl carbonate (MBC) and dibutyl carbonate (DBC)), ethers (e.g., tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-di oxane, 1,2-dimethoxy ethane (DME), 1,2-diethoxyethane and 1,2-dibutoxy ethane), nitriles (e.g., acetonitrile and adiponitrile) linear esters (e.g., methyl propionate, methyl pivalate, buty l pivalate and octyl pivalate), amides (e.g., dimethyl formamide), organic phosphates (e.g., trimethyl phosphate and trioctyl phosphate), organic compounds containing an S=O group (e.g., dimethyl sulfone and di vinyl sulfone), and combinations thereof.

[0081] Non-aqueous liquid solvents can be employed in combination. Examples of these combinations include combinations of cyclic carbonate-linear carbonate, cyclic carbonatelactone, cyclic carbonate-lactone-linear carbonate, cyclic carbonate-linear carbonate-lactone. cyclic carbonate-linear carbonate-ether, and cyclic carbonate-linear ester. In some examples, a cyclic carbonate may be combined with a linear ester. Moreover, a cyclic carbonate may be combined with a lactone and a linear ester. In some examples, the weight ratio, or alternatively the volume ratio, of a cyclic carbonate to a linear ester is in a range of 1:9 to 10:1, alternatively 2:8 to 7:3.

[0082] A salt for liquid electrolytes may include one or more of the following non-limiting examples: LiPF6. LiBF4, LiCIC , LiAsF6, LiN(CF3SO2)2(“LiTFSI”), LiN(C2F5SO2)2, L1CF3SO3, LIC(CF3SO2)3, LIPF4(CF3)2, LIPF3(C2F5)3, LIPF3(CF3)3, L1PF3 (iso-C3F7)3, LiPFs iso-CsF?), lithium salts having cyclic alky l groups (e.g., (CF2)2(SO2)2xLi and (CF2)3(SO2)2xLi), LiFSI (lithium bis(fluorosulfonyl)imide), LiTDI (lithium 4,5-dicyano-2-(trifluoromethyl)imidazole), and combinations thereof.

[0083] In some examples, the total concentration of a lithium salt in a liquid non-aqueous solvent (or combination of solvents) is at least 0.3 M, alternatively at least 0.7M. The upper concentration limit may be driven by a solubility limit and operational temperature range. In some examples, the concentration of salt is no greater than about 2.5 M, alternatively no more than about 1.5 M. In some examples, the electrolyte may include a saturated solution of a lithium salt and excess solid lithium salt.

[0084] Additives may be included in the electrolyte to serve various functions such as to stabilize the battery'. For example, additives such as polymerizable compounds having an unsaturated double bond may be added to stabilize or modify the SEI. Certain amines or borate compounds may act as cathode protection agents. Lewis acids can be added to stabilize fluorine-containing anion such as (PFef. Safety protection agents include those to protect overcharge, e.g., anisoles, or act as fire retardants, e.g., alky l phosphates. Other additives may include fluorinated materials such as FEC or various hydrofluoroethers, or silane or siloxane derivatives. Other additives may include ionic liquids or materials to scavenge or sequester water, HF, transition metal ions, or the like. In some examples, the electrolyte may be formulated as a localized high concentration electrolyte. In some examples, the electrolyte includes a non-aqueous ionic liquid and a lithium salt.

[0085] SSE

[0086] A solid-state electrolyte includes a source of mobile lithium 10ns that diffuse between the anode and the cathode (to the anode during charging and away from the anode during discharging). The three main families of SSE are solid polymer electrolytes (SPEs), solid inorganic electrolytes (SIEs), and hybrid SSE which uses both SPE and SIE materials. Note that, herein, an SPE includes the category of gel electrolytes. In some cases, the source of lithium ion may include a lithium salt, which may be in the form of a small molecule (e g., LiTSFI, LiPFe or some any other lithium salt described above) suspended or dissolved in a SSE matrix. In some cases, a SPE material may include an anionic functional group that may act as the lithium salt counterion. The SSE may optionally include plasticizers, rheology control agents, or even a small amount of organic solvent(s).

[0087] A few non-limiting examples of polymeric materials that may be used in the SSE composition include poly(ethylene oxide) (PEO), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA), poly(trimethylene carbonate), diester-based polymers, PVdF-based polymers, poly caprolactone, and their derivatives or copolymers, which may be used alone or in combination. The polymer of the SSE may in some cases be cross-linked or branched. The polymer may be a block copolymer. A polymer SSE may be fully amorphous or include some crystallinity. The polymer may include anionic functional groups.

[0088] A few non-limiting classes of SIE material that may be used in the SSE composition include b-aluminas, LISICONs, thio-LISICONs, NASICONs, perovskites, antiperovskites, garnets, complex hydrides, and solid sulfides.

[0089] A few non-limiting classes of solid sulfides include ceramic sulfides, glass sulfides, and glass-ceramic sulfides. Glass sulfides show minimal long-range order that is identified by the lack of peaks in the pattern resulting from x-ray diffraction (XRD) measurements. Glassceramic sulfides include some glass structural regions and some regions with long range order that is identified by characteristic peaks in the pattern resulting from XRD measurements. Ceramic sulfides, also known as crystalline sulfides, are composed of regions that have long range order that is identified by characteristic peaks in the pattern resulting from XRD measurements. Non-limiting examples of ceramic sulfides include argyrodites, silicon thiophosphates, and silicon halide thiophosphates. Exemplary, but non-limiting, solid sulfides comprise a thiophosphate (PS4) that may be identified by a characteristic feature in the pattern resulting from measurement with either infrared spectroscopy or Raman spectroscopy. Some additional examples of solid sulfides may include LiePSsCl, LGPS materials such as LiioGeP2Si2. and LPS materials such as LiyPsSii.

[0090] In some examples, under battery operating conditions, the SSE may have a lithium-ion conductivity in a range of 0.001 mS / cm to 0.01 mS / cm, alternatively in a range of 0.01 mS / cmto 0.1 mS / cm, alternatively in a range of 0.1 mS / cm to 1.0 mS / cm, alternatively higher than 1 mS / cm.

[0091] The thickness of the SSE should be sufficient to prevent shorting between the anode and cathode, but not so thick that it increases resistance or reduces energy density beyond desirable levels. An SSE generally has a thickness greater than 100 nm and less than 800 microns. For micro-batteries, it may be in a range of about 100 nm to 5 microns. For moreconventional battery cells, the SSE may typically have a thickness in a range of 5 - 300 microns.

[0092] In some examples, an SSE may include a relatively small amount of organic solvent, e.g., for increasing lithium-ion conductivity or simply as a vehicle for adding lithium salts. Some non-limiting examples of such solvents include those listed above for liquid electrolytes. In some examples, the weight % of solvent relative to other components of the SSE may be less than 10%, alternatively less than 5%, 2%, 1%. 0.5%, 0.2%, or 0.1%.

[0093] Cathode

[0094] Positive electrode (cathode) active materials include, but are not limited to, lithium metal oxides or compounds (e.g., LiCoCh, LiFePCE, LiMnCh, LiNiCfi. LiM^CE, LiCoPO4, LiNixCoyMnzCh, LiNixCoyAlzCh, LiFe2(SO4)3, or Li2FeSiO4), carbon fluoride, metal fluorides such as iron fluoride (FeF?), metal oxide, sulfur, selenium and combinations thereof. Cathode active materials may operate, e.g., by intercalation, conversion, or a combination. Cathode active materials may in some cases be mixed with one or more binders and coated to form the cathode. In some cases, the cathode may include polymeric, SIE, or hybrid SSE materials like any of those described elsewhere, and which may be the same as or different than the material used in the SSE layer between the anode and cathode. In some cases, a solid electrolyte used in the cathode may be different than the SSE layer, e.g., it may have lower flowability than the SSE layer. Cathode active materials are ty pically provided on, or in electrical communication with, an electrically conductive cathode current collector, often on both sides.

[0095] Battery Format

[0096] In some examples, battery cells can be formed into multilay er stacks of anodes and cathodes, e.g., in a pouch cell, a coin cell, or some prismatic cells. Alternatively, anode / cathode stacks can be formed into a so-called jellyroll and used in cylindrical cells or some other prismatic cells. Such structures are provided into an appropriate housing having desired electrical contacts. A cell may sometimes include confinement features to limit expansion of the cell and / or a compression system that applies a compressive force between the anode and the cathode. Such features may sometimes improve cycle life.

[0097] FIG. 6 is a schematic cross-sectional view of a non-limiting example of battery cell. In this example, battery cell 690 may include a top plate 660, a bottom plate 662, an anode side plate 664 and a cathode side plate 666, which form part of a housing for the stack of anodes 600, cathodes 640 and intervening separators 630. Typically, at least the inside portion of the top plate and bottom plate are made from electrically insulative material. Theanodes and cathodes may include active material provided on both sides of their respective current collectors, but for clarity, these details are not illustrated. The anodes (specifically, the anode current collectors) are electrically connected to an electrically conductive anode bus 620 which may be connected to electrically conductive anode lead 622 that extends through anode side plate 664. The anode side plate may be made from an electrically insulating material, but in some alternative examples, the anode side plate may be electrically conductive. Cathodes (specifically, the cathode current collectors) are electrically connected to an electrically conductive cathode bus 650 which is connected to an electrically conductive cathode lead 652 that extends through cathode side plate 666. The cathode side plate may be made from an electrically insulating material, but in some alternative examples, the cathode side plate may be electrically conductive. Battery cell 690 may further include liquid electrolyte 680 which fills the space and saturates the separators 630. Top compression member 670 and lower compression member 672 may optionally be provided to apply physical pressure (arrows) between the anodes and cathodes. Compression members may be compressible films, e.g., made from a porous polymer or silicone. Alternatively, compression members may include an array of compressible features, e.g., made from porous polymer or silicone. Alternatively, the compression members may include springs or an array of springs. Alternatively, compression members may correspond to two sides of a compression clip or clamp. In some examples, the separator may act as a compressible film. In some examples the top and bottom plates may be formed a material and / or structured to resist deformation thereby confining battery swell. In some cases, compression features may instead be located outside of the cell housing rather than inside. Note that, in some solid-state examples, 630 may instead generally represent solid-state electrolyte and liquid electrolyte 680 may be absent.

[0098] Separator

[0099] The battery may further include a so-called "separator" between the anode and cathode, particularly when using a liquid electrolyte. The current separator allows lithium ions to flow between the anode and cathode but prevents direct electrical contact, e.g., when the SSE is in a state of high flowability. Separators are typically made in the form of a porous sheet of electrically insulative material. In some cases, separators are single layer or multilayer polymer sheets (e.g., based on polyolefins, PET, or PVDF). Separators may alternatively include glass materials, ceramic materials, a ceramic material embedded in a polymer, a polymer coated with a ceramic, or some other composite or multilayer structure, e.g., to provide higher mechanical and thermal stability. In some cases, a separator may have>30% porosity, low ionic resistivity, a thickness of - 10 to 50 pm and high bulk puncture strengths.

[0100] In some examples, electrochemical cycling conditions may be set to utilize only a portion of the theoretical charge / discharge capacity of lithium storage layer materials. This may in some cases increase the lifetime of the battery7cell. In some examples, such portion may be in a range of 30 - 50%, 50 - 70%, 70 - 80%, 80 - 90%. or any combination of ranges thereof.

[0101] Working Examples

[0102] Set I

[0103] In a first set of tests (Set I), a Meyer Burger DepX ETP-CVD tool was used to deposit the anode active material (the lithium storage layer) onto a copper foil current collector. Depositions were conducted at a temperature in a range of about 450 - 550°C at a power in a range of about 1.6 to 2 kW per ETP source. Three in-line ETP sources (aligned perpendicularly to the substrate transport direction) were used. The deposition gas was a mixture of silane (silicon precursor gas) and argon in a gas flow ratio of about 1 to 10, respectively (deposition gas I-A). In examples where nitrogen was co-deposited, the deposition gas mixture further included N2 (nitrogen precursor gas) at a flow rate that was around 1.7 times the silane gas flow rate (deposition gas I-B). Chemical compositions of the lithium storage layers were generally not analyzed for each sample, but atomic % estimates are provided based on analytical testing of related samples. In addition to the atomic % estimates noted below, the lithium storage layer of each example may have further included some hydrogen, but if so, it is estimated to be less than 25 atomic %.

[0104] Anode 1-1 (Si)

[0105] Deposition gas I-A was used to deposit a lithium storage layer onto the current collector. The lithium storage layer had a thickness of about 15 pm and included primarily amorphous silicon. It was estimated this lithium storage layer included greater than 50 atomic % silicon and a relatively low amount of nitrogen (if any) since no nitrogen precursor gas was used.

[0106] Anode 1-2 (SiNx)

[0107] Deposition gas I-B was used to deposit a lithium storage layer onto the current collector. The lithium storage layer had a thickness of about 15 pm and included both silicon and nitrogen. This lithium storage layer was estimated to include greater than 50 atomic % silicon and nitrogen in a range of 10 - 20 atomic %.

[0108] Set II

[0109] In a second set of tests (Set II), an Oxford Plasmalabs System 100 PECVD tool was used to deposit the anode active material (the lithium storage layer) onto a copper foil current collector. Depositions were conducted at a temperature in a range of about 250 - 350°C at an RF power in a range of about 150 to 300 W. The deposition gas was a mixture of silane (silicon precursor gas) and argon in a gas flow ratio of about 1 to 11, respectively (deposition gas II- A). In examples where nitrogen was co-deposited, the deposition gas mixture further included ammonia (nitrogen precursor gas) at a flow rate about half of the silane flow (deposition gas II-B). In examples where carbon was co-deposited, the deposition gas mixture further included methane (carbon precursor gas) at a flow rate that w as similar to the silane gas flow rate (deposition gas II-C). Chemical compositions of the lithium storage layers were generally not analyzed for each sample, but atomic % estimates are provided based on analytical testing of related samples. In addition to the atomic % estimates noted below; the lithium storage layer of each example may have further included some hydrogen, but if so, it is estimated to be less than 25 atomic %.

[0110] Anode II- 1 (Si)

[0111] Deposition gas Il-A was used to deposit a lithium storage layer onto the current collector. The lithium storage layer had a thickness of about 9 pm and included primarily amorphous silicon. It was estimated that this lithium storage layer included greater than 50 atomic % silicon and a relatively low7amount of carbon (if any) since no nitrogen precursor gas was used.

[0112] Anode II-2 (SiNx)

[0113] Deposition gas II-B was used to deposit a lithium storage layer onto the current collector. The lithium storage layer had a thickness of about 9 pm and included both silicon and nitrogen. This lithium storage layer was estimated to include greater than 50 atomic % silicon and nitrogen in a range of 5 - 40 atomic %.

[0114] Anode II-3 (SiNx / Si)

[0115] Deposition gas II-B was used to deposit a first lithium storage sublayer (about 2 pm) onto the current collector. This sublayer was estimated to include greater than 50 atomic % silicon and nitrogen in a range of 5 - 40 atomic %. Next, deposition gas II-A was used to deposit a second lithium storage sublayer (about 7 pm) over the first sublayer. This second sublayer was estimated to have greater than 50 atomic % silicon and less nitrogen (if any) relative to the first sublayer.

[0116] Anode II-4 (SiNx / SiCx)

[0117] Deposition gas II-B was used to deposit a first lithium storage sublayer (about 4.5 pm) onto the current collector. This first sublayer is estimated to include greater than 50 atomic % silicon and nitrogen in a range of 5 - 40 atomic %. Next, deposition gas II-C was used to deposit a second lithium storage (about 4 pm) over the first sublayer. This second sublayer was estimated to have greater than 50 atomic % silicon and carbon in a range of 5 -20 atomic %.

[0118] Anode II-5 (SiCx / SiNx)

[0119] This sample was made like Anode II-4, but with the deposition sequence for the two sublayers reversed such that the first lithium storage sublayer included the carbon and the second lithium storage sublayer included the nitrogen.

[0120] Anode II-6 (SiCx)

[0121] Deposition gas II-C was used to deposit a lithium storage layer onto the current collector. The lithium storage layer had a thickness of about 9 pm and included both silicon and carbon. This lithium storage layer was estimated to include greater than 50 atomic % silicon and carbon in a range of 5 - 20 atomic %.

[0122] Anode 11-7 (Si / SiCx)

[0123] Deposition gas II-A was used to deposit a first lithium storage sublayer (about 4.5 pm) onto the current collector. This sublayer was estimated to include greater than 50 atomic % silicon and a relatively low amount of carbon (if any) since no carbon precursor gas was used. Next, deposition gas II-C was used to deposit a second lithium storage sublayer (about 4 pm) over the first sublayer. This second sublayer was estimated to have greater than 50 atomic % silicon and carbon in a range of 5 - 20 atomic %.

[0124] Anode II-8 (SiCx / Si)

[0125] This sample was made like Anode II-7 but with the deposition sequence for the two sublayers reversed such that the first lithium storage sublayer included the carbon and the second lithium storage sublayer did not.

[0126] Electrochemical Testing

[0127] Pouch cells were constructed such that each anode was paired with a 4 mAh / cm2rated NMC622 cathode and separated by a Celgard™ separator. The standard electrolyte solution included: a) 88 wt.% of 1.2 M LiPFe in 3:7 EC:EMC (weight ratio); b) 10 wt.% FEC; and 2 wt.% VC. The cells first underwent an electrochemical formation step. The electrochemical formation step is used to form an initial SEI layer on the anode. Relatively gentle conditions of low current and / or limited voltages may be used to ensure that the anode is not overly stressed. The total active silicon (mg / cm2) available for reversible lithiation and total chargecapacity (mAh / cm2) were determined from the electrochemical formation step data. The Set I anodes were formed to approximately 4.4 mAh / cm2and it was noted that cells made with Anode 1-2 forms to about 5-10% less capacity than cells made with Anode 1-1. For Set II, reversible capacity values are provided in Table 1 below. While silicon has a theoretical charge capacity of about 3600 mAh / g when used in lithium-ion batteries, it has been found that cycle life may improve if only a portion of the full capacity is used. The performance cycling protocol included C / 2-C / 2 charge-discharge rates over a voltage range of 2.8 - 4.1 (Set I) or 2.5-4.15V (Set II). The number of cycles it took to fall below 80% of the initial discharge capacity (so called 80% state of health cycle life or “80% SOH”) was evaluated.

[0128] Long-Term Storage Testing

[0129] The deposited samples were initially visually inspected for defects after deposition and samples having any type of visual defect were discarded. Remaining samples were packaged in resealable plastic bags and stored in ambient air at a temperature of about 20 °C and a relative humidity of greater than 20% generally for a minimum period of 2 months and evaluated for long-term flaking. None of the anodes showed flaking at the start of the storage test. Periodic visual inspections of the stored anodes, e.g., on a weekly basis, were carried out to determine when and how severely samples were flaking. After at least 2 months, a sample was rated “pass” if no flaking observed, and rated “fail” if flaking was observed in even just one area.

[0130] Table 1 - testing results

[0131] As can be seen from Table 1, samples that included nitrogen or carbon throughout the layer, or at least adjacent to the current collector, have improved cycle life (80% SOH) relative to their comparative silicon (1-2 vs 1-1, or II-2,-3,-4,-5,-6,-8 vs II- 1 ). Interestingly, when carbon was provided in a second sublayer and no nitrogen or carbon was provided inthe first sublayer (II-7), the cycle life was as good as plain silicon (II-l), but not better. A dramatic and unexpected improvement was observed in long-term storage stability when the lithium storage layer included carbon or nitrogen throughout the layer, or at least adjacent to the current collector (1-2 vs 1-1, or II-2,-3,-4,-5,-6,-8 vs II-l). Although the overall anode storage capacity may be a bit lower when nitrogen is present, this is more than offset by the benefits in cycle life and especially long-term storage stability.

[0132] Some of the methods described herein for making anodes are particularly suitable for large-scale processing (e.g., roll-to-roll) and such anodes tend to have the lowest cost when large batches or rolls are made in a production run. Anode material from a large production run may sit in storage for an extended time. It has been found that storage under dry', inert gas (Ar or N2) significantly extends the long-term storage life, but it requires specialized storage areas and packaging which adds considerable cost. The surprising advantage of SiNx or SiCx for long-term storage relative to Si alone under ambient conditions (e.g., in non-desiccated air at about room temperature) fully alleviates the need for special and costly storage facilities. Although the “pass” rating required at least 2 months of storage time, it has been found that samples that pass generally do not flake at all even after much longer storage periods. For example, many' samples have now exceeded 1 year and some more than 2 years of storage. In some embodiments, samples may exceed 3 to 5 years of storage.

[0133] Still further examples herein include the following non-limiting enumerated aspects.

[0134] Enumerated aspect 1. A method of making an anode for a lithium-ion energy storage device, the method including: forming a lithium storage layer on a current collector by a PVD or a CVD process, wherein the lithium storage layer includes at least 40 atomic % silicon and at least one of carbon and nitrogen, wherein a total amount of the carbon and nitrogen is in a range 0.5 - 50 atomic %; and storing the anode in the presence of air at a temperature in a range of 10 - 30 °C for at least 30 days.

[0135] Enumerated aspect 2. The method of enumerated aspect 1, wherein the air has a relative humidity of at least 10%.

[0136] Enumerated aspect 3. The method of enumerated aspect 1 or 2, wherein the anode is stored for at least 60 days.

[0137] Enumerated aspect 4. The method according to any of enumerated aspects 1 - 3, wherein the lithium storage layer includes carbon and nitrogen.

[0138] Enumerated aspect 5. The method according to any of the preceding enumerated aspects, wherein the carbon in the lithium storage layer is in a range of 0.5 - 30 atomic %.

[0139] Enumerated aspect 6. The method according to any of the preceding enumerated aspects, wherein the lithium storage layer includes at least 50 atomic % silicon.

[0140] Enumerated aspect 7. The method according to any of enumerated aspects 1 - 5, wherein the lithium storage layer further includes hydrogen, and the hydrogen is in a range of 0.5 - 25 atomic %.

[0141] Enumerated aspect 8. The method according to any of the preceding enumerated aspects, wherein the CVD process includes PECVD.

[0142] Enumerated aspect 9. The method according to any of the preceding enumerated aspects, further including forming the lithium storage layer at least in part by a roll-to-roll PECVD process.

[0143] Enumerated aspect 10. The method according to any of the preceding enumerated aspects, further including changing the PVD or CVD process conditions while forming the lithium storage layer so that the lithium storage layer is characterized by a composition that varies as a function of thickness, T, measured from the current collector, optionally wherein: a lower portion of the lithium storage layer adjacent the current collector has a higher atomic % of nitrogen or carbon than an upper portion away from the current collector, the lower portion corresponds to the lithium storage layer between T = 0 and Z*TL, where TL is the total thickness of the lithium storage layer, and the upper portion corresponds to the lithium storage layer between Z*TL and TL.

[0144] Enumerated aspect 11. The method according to enumerated aspect 10, wherein z is in a range of 0.05 to 0.95, and optionally wherein z = 0.2 or 0.5.

[0145] Enumerated aspect 12. The method of enumerated aspect 10 or 11, wherein the lithium storage layer includes a first sublayer adjacent to the current collector and a second sublayer overlaying the first sublayer, and optionally wherein the first sublayer has a higher atomic % of carbon or nitrogen than the second sublayer.

[0146] Enumerated aspect 13. The method according to any of the preceding enumerated aspects, wherein the current collector includes a surface layer disposed over an electrically conductive layer, and wherein the method further includes depositing the lithium storage layer onto the surface layer.

[0147] Enumerated aspect 14. The method of enumerated aspect 13, wherein the surface layer includes a metal-oxygen compound, optionally wherein the metal -oxygen compound is an oxometallate or a metal oxide.

[0148] Enumerated aspect 15. The method of enumerated aspect 13 or 14, wherein the electrically conductive layer includes a metal foil.

[0149] Enumerated aspect 16. The method according to any of the preceding enumerated aspects, wherein the lithium storage layer is a first-side lithium storage layer formed on a first side of the current collector, and wherein the method further includes forming a second-side lithium storage layer on a second side of the current collector by a PVD or CVD process.

[0150] Enumerated aspect 17. The method of enumerated aspect 16, wherein the second-side lithium storage layer has a composition that is the same as or different from the first-side lithium storage layer.

[0151] Enumerated aspect 18. The method of enumerated aspect 16 or 17, wherein the current collector includes a second-side surface layer provided on an electrically conductive layer, and method further includes depositing second-side lithium storage layer onto the second-side surface layer.

[0152] Enumerated aspect 19. A lithium-ion battery including an anode made by the method according to any of the preceding enumerated aspects.

[0153] Enumerated aspect 20. An anode made the method according to any of enumerated aspects 1 - 18.

[0154] The specific details of particular embodiments may be combined in any suitable manner without departing from the spirit and scope of embodiments of the invention.However, other embodiments of the invention may be directed to specific embodiments relating to each individual aspect, or specific combinations of these individual aspects.

[0155] The above description of example embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above.

[0156] In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

[0157] Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of w ell-know n processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Additionally, details of any specific embodiment may not always be present in variations of that embodiment or may be added to other embodiments.

[0158] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0159] As used herein and in the appended claims, the singular forms “a”, "an". and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to ‘'a method” includes a plurality of such methods and reference to “the anode” includes reference to one or more anodes and equivalents thereof known to those skilled in the art, and so forth. The invention has now been described in detail for the purposes of clarity and understanding. However, it will be appreciated that certain changes and modifications may be practice w ithin the scope of the appended claims.

[0160] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. None is admitted to be prior art.

Claims

CLAIMSWhat is claimed is:

1. A method of making an anode for a lithium-ion energy storage device, the method comprising:forming a lithium storage layer on a current collector by a PVD or a CVD process, wherein the lithium storage layer comprises at least 40 atomic % silicon, wherein the atomic % is relative to a total of non-hydrogen atoms, wherein the lithium storage layer further comprises at least one of carbon and nitrogen, and wherein a total amount of the carbon and nitrogen is in a range 0.5 - 50 atomic %; andstoring the anode in the presence of air at a temperature in a range of 10 - 30 °C for at least 30 days.

2. The method of claim 1. wherein the air has a relative humidity of at least 10%.

3. The method of claim 1, wherein the anode is stored for at least 60 days.

4. The method of claim 1, wherein the lithium storage layer comprises carbon and nitrogen.

5. The method of claim 1, wherein the carbon in the lithium storage layer is in a range of 0.5 - 30 atomic %.

6. The method of claim 1, wherein the lithium storage layer comprises at least 50 atomic % silicon.

7. The method of claim 1, wherein the lithium storage layer further comprises hydrogen, and the hydrogen is in a range of 0.5 - 25 atomic % relative to a total of all atoms.

8. The method of claim 1, wherein the CVD process includes PECVD.

9. The method of claim 1, further comprising forming the lithium storage layer at least in part by a roll-to-roll PECVD process.

10. The method of claim 1. further comprising changing the PVD or CVD process conditions while forming the lithium storage layer so that the lithium storage layer is characterized by a composition that varies as a function of thickness, T, measured from the current collector, wherein:a lower portion of the lithium storage layer adjacent the current collector has a higher atomic % of nitrogen or carbon than an upper portion away from the current collector;the lower portion corresponds to the lithium storage layer between T = 0 and Z*TL, where TL is a total thickness of the lithium storage layer;the upper portion corresponds to the lithium storage layer between Z*TL and TL; andz is in a range of 0.05 to 0.95.

11. The method of claim 10, wherein z = 0.2 or 0.5.

12. The method of claim 10, wherein the lithium storage layer comprises a first sublayer adjacent to the current collector and a second sublayer overlaying the first sublayer, and wherein the first sublayer has a higher atomic % of carbon or nitrogen than the second sublayer.

13. The method of claim 1. wherein the current collector comprises a surface layer disposed over an electrically conductive layer, and wherein the method further comprises depositing the lithium storage layer onto the surface layer.

14. The method of claim 13, wherein the surface layer comprises a metal-oxygen compound.

15. The method of claim 13, wherein the electrically conductive layer comprises a metal foil.

16. The method of claim 1, wherein the lithium storage layer is a first-side lithium storage layer formed on a first side of the current collector, and wherein the method further comprises forming a second-side lithium storage layer on a second side of the current collector by a PVD or CVD process.

17. The method of claim 16, wherein the second-side lithium storage layer has a composition that is the same as the first-side lithium storage layer.

18. The method of claim 16, wherein the second-side lithium storage layer has a composition that is different from the first-side lithium storage layer.

19. The method of claim 16, wherein the current collector comprises a second-side surface layer provided on an electrically conductive layer, and method further includes depositing second-side lithium storage layer onto the second-side surface layer.

20. A lithium-ion battery comprising the anode made by the method of claim 1.

21. An anode made by the method of claim 1.

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