Multilayer anodes for lithium-ion batteries

Abstract

An anode for an energy storage device includes a current collector, a first lithium storage layer overlaying the current collector, and a second lithium storage layer overlaying the first lithium storage layer. The first lithium storage layer includes an alloying lithium storage material and the second lithium storage layer includes a non-alloying metal compound lithium storage material selected from a conversion-type material or an intercalation -type material. A battery cell may include the anode, a cathode, and an electrolyte interposed between the anode and cathode. The electrolyte may optionally include a solid-state electrolyte.

Description

MULTILAYER ANODES FOR LITHIUM-ION BATTERIES CROSS- REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional ApplicationNo.63 / 560,081 filed March 1, 2024, entitled “MULTILAYER ANODES FOR LITHIUM-ION BATTERIES”, the entire contents of which is incorporated by reference in its entirety for all purposes. TECHNICAL FIELD

[0002] The present disclosure relates to solid-state lithium-ion batteries and relatedenergy storage devices. BACKGROUND

[0003] Silicon has been proposed for lithium-ion batteries to replace the conventionalcarbon-based anodes, which have a storage capacity that is limited to ~370 mAh / g. Silicon readily alloys with lithium and has a much higher theoretical storage capacity (~3600 mAh / g at room temperature) than carbon anodes. Besides improved energy storage density, silicon-based anodes may also provide additional safety benefits, e.g., more robust performance against the well-known “nail penetration test”. To further improve the safety of lithium-ion batteries, work is also ongoing to replace electrolytes based on volatile small molecule solvents with safer solid-state electrolytes (SSEs).

[0004] Unfortunately, insertion and extraction of lithium into the silicon matrix cancause significant volume expansion (>300%) and contraction. This can result in rapid pulverization of the silicon into small particles and electrical disconnection from the current collector. The expansion and contraction of silicon-containing anodes pose additional challenges for making solid-state battery cells. With such volume changes, it can be difficult to maintain functionally sufficient physical contact between the anode active material and the solid-state electrolyte. Further, some solid-state materials can degrade the silicon-SSE interface during operation.

[0005] Despite research into various approaches, batteries based primarily on silicon,have yet to make a large market impact due to unresolved problems. SUMMARY

[0006] There remains a desire for lithium-ion batteries based on silicon anodes that areeasy to manufacture, safer, robust to handling, high in charge capacity, amenable to fast charging, and have good cycle life. Embodiments of this disclosure address these and other needs.

[0007] In accordance with an embodiment of this disclosure, an anode for an energystorage device includes a current collector, a first lithium storage layer overlaying the current collector, and a second lithium storage layer overlaying the first lithium storage layer. The first lithium storage layer includes an alloying lithium storage material, and the second lithium storage layer includes a non-alloying metal compound lithium storage material selected from a conversion-type material or an intercalation-type material. BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a cross-sectional view of a non-limiting example of an anodeaccording to the present disclosure.

[0009] FIGS. 2A and 2B are cross-sectional views of non-limiting examples of anodesaccording to the present disclosure.

[0010] FIG. 3 is a cross-sectional view of lithium storage nanostructures.

[0011] FIGS. 4A and 4B are cross-sectional views of lithium-ion battery cellsaccording to some examples.

[0012] FIG. 5 is a schematic cross-sectional view of a non-limiting example of abattery cell. DETAILED DESCRIPTION

[0013] It is to be understood that the drawings are for purposes of illustrating theconcepts 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 of certain aspects of the present application may in some cases be found in one or more of the following patent documents: 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, U.S. Patent Application Publication No. 2025 / 0062316, 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, PCT International PublicationNumber WO2024 / 226833, PCT International Publication number WO2024 / 173390, and PCT Application Number PCT / US2024 / 62265 the entire contents of which are incorporated herein by reference for all uses.

[0014] Lithium-ion batteries (LIBs) of the present disclosure may include an anode, anelectrolyte (which may be a liquid or an SSE), and a cathode. In particular, the anode may have a multilayer structure of different anode active materials (lithium storage materials). FIG.1 is a cross-sectional view of an anode 100 according to some non-limiting examples. For additional reference, XYZ coordinate axes are also provided. Anode 100 may include a current collector 101 and a lithium storage structure 102 overlaying the current collector. Lithium storage structure 102 includes first lithium storage layer 107 overlaying the current collector. The first lithium storage layer includes an alloying lithium storage material, i.e., a material that is capable of forming an electrochemically reversible alloy with lithium. A few non-limiting examples of alloying lithium storage materials include silicon, germanium, tin, and alloys thereof. In some examples the first lithium storage layer includes at least 40 atomic % silicon, alternatively at least 50 atomic % silicon, alternatively at least 60 atomic % silicon, alternatively at least 70 atomic % silicon, alternatively at least 80 atomic % silicon or even at least 90 atomic % silicon. Alloying lithium storage materials are discussed elsewhere herein.

[0015] A second lithium storage layer 109 overlays the first lithium storage layer. Thesecond lithium storage layer includes a non-alloying metal compound lithium storage material. In some cases, the non-alloying metal compound may be a conversion-type material. Conversion lithium storage materials are sometimes referred to as conversion- type anode materials (“CTAMs”). Alternatively, the non-alloying metal compound may be an intercalation-type material. Conversion-type and intercalation-type materials are discussed elsewhere herein. Note that intercalating-type metal compounds do not include carbon-based intercalating materials such as graphite. Although a minor amount of carbon-based intercalating materials may be present in some cases (constituting less than 50% of the second layer’s lithium storage capacity, e.g., as measured in mAh / cm2), in some preferred examples, the second lithium storage layer is substantially free of carbon- based lithium storage materials (less than 5% by weight, or alternatively, less than 1% by weight, e.g., as measured relative to the total mass of the second lithium storage layer). In some cases, the first lithium storage layer may have a higher lithium storage capacity than the second lithium storage layer, e.g., in terms of mAh / cm2or mAh / g or both. Despite the lower capacity, the second lithium storage layer may provide otheradvantages to the system. For example, the second lithium storage layer may reduce unwanted reactions between the electrolyte (liquid or SSE) and the first lithium storage layer that can degrade various performance metrics (charge / discharge rates, cycle life, overall capacity, or the like). That is, relative to the alloying lithium storage material, the non-alloying metal compound may have superior interfacial properties with the electrolyte to promote faster charging / discharging, higher cycle life, lower resistance, or the like. In addition to lessening direct contact of the alloying lithium storage material with the electrolyte, the non-alloying metal compound is able to provide at least some lithium storage capacity. This is unlike simple protective layers that conduct lithium ions but are otherwise passive (e.g., materials like LIPON). Besides the advantages noted above for the present layer order, testing has found that reversing the lithium storage layer structure, i.e., so that the alloying lithium storage material is on the top, produces an anode that has unexpectedly poor cycle life. The current collector 101 may include an electrically conductive layer 103 and may in some cases further include a surface layer 105 disposed between the electrically conductive layer 103 and the first lithium storage layer 107. The surface layer may have properties that improve adherence or charge transport between the first lithium storage layer and the current collector. Although the figures show the surface of the current collector as flat for convenience, the current collector may have a rough surface as discussed elsewhere herein. In some preferred cases, the first lithium storage layer is provided by a physical vapor deposition (PVD) process, e.g., by sputtering or e-beam, or by a chemical vapor deposition (CVD) process including, but not limited to, hot-wire CVD or plasma- enhanced chemical vapor deposition (PECVD). In some cases, the second lithium storage layer may also be provided by a PVD or CVD process. PVD and CVD deposition methods are highly manufacturable since they may avoid the many extra steps involved in conventional binder-based (particulate) lithium storage layers. In some examples, the second lithium storage layer may be coated from a slurry-based composition that, in addition to the non-alloying metal compound, may optionally include binders or conductive particles.

[0016] Although not illustrated, the first lithium storage layer may itself include amultilayer or gradient structure of different alloying lithium storage materials, i.e., wherein the chemical composition of the first lithium storage layer changes as a function of layer thickness in the z-axis direction. Similarly, the second lithium storage layer may itselfinclude a multilayer or gradient structure of different non-alloying metal compounds, i.e., wherein the chemical composition of the second lithium storage layer changes as a function of layer thickness in the z-axis direction.

[0017] FIGS. 2A and 2B are cross-sectional views of some non-limiting examples of ananode. In FIGS.2A and 2B illustrate anodes 200A and 200B that each include a current collector 201. A segmented first lithium storage layer is provided over the current collector and including a plurality of segments 207 separated by spaces 206. The first lithium storage layer segments include an alloying lithium storage material. The spaces may be uniform or random.

[0018] Anode 200A includes a second segmented lithium storage layer including aplurality of segments 209A provided over the first lithium storage layer segments to form lithium storage structure 202A. The second lithium storage layer segments include a non- alloying metal compound lithium storage material. In some cases, lithium storage structure 202A may be made as a result of electrochemical cycling of an anode such as that shown in FIG.1. While not being bound by theory, it may be that anodes of the present disclosure (in particular, the first lithium storage layer) expand primarily (not necessarily solely) in a Z direction during lithiation, and upon delithiation, may contract in the Z direction and also in the X-Y plane so that the lithium storage structure is reconstituted as a segmented lithium storage layer.

[0019] Anode 200B includes a second lithium storage layer 209B provided over thelithium storage layer segments 207 and also at least partially into spaces 206 to form lithium storage structure 202B. Within spaces 206, the second lithium storage layer may in some cases directly contact the current collector. The second lithium storage layer 209B includes a non-alloying metal compound lithium storage material. Although the second lithium storage layer 209B is illustrated as a planarizing layer, in some alternative examples (not shown), the second lithium storage layer may more conformally coat the first lithium storage layer segments and exposed current collector. In some cases, the second lithium storage layer may be substantially continuous. In some cases (not shown), the second lithium storage layer may only partially extend into the spaces (down sidewalls of the first lithium storage layer segments) and may be discontinuous or segmented.

[0020] In some examples, for the majority of lithium storage segments within at leastone 1 mm by 1 mm area of the anode, a ratio of the average lateral width LW of a lithium storage layer segment (e.g., as measured along the x-axis at half or approximately half of its thickness) to the average thickness T of the lithium storage layer segment (e.g., asmeasured along the z-axis from the current collector to the top of the lithium storage segment), i.e., the ratio or LW / T may be at least 0.3. In some examples, such ratio of LW / T may be less than 50. In some examples, the ratio of LW / T may be in a range of 0.3 – 0.4, alternatively 0.4 – 0.5, alternatively 0.5 – 0.75, alternatively 0.75 – 1.0, alternatively 1.0 – 1.5, alternatively 1.5 – 2, alternatively 2 – 3, alternatively 3 – 4, alternatively 4 – 5, alternatively 5 – 7, alternatively 7 – 10, alternatively 10 – 15, alternatively 15 – 20, alternatively 20 – 25, alternatively 25 – 30, alternatively 30 – 40, alternatively 40 – 50, or any combinations of ranges thereof, or even higher than 50.

[0021] In some examples, the average width of spaces 206 may be in a range of 10 – 20nm, 20 – 50 nm, 50 – 100 nm, 100 – 200 nm, 200 – 300 nm, 300 – 500 nm, 500 – 700 nm, 700 nm – 1 µm, 1 – 2 µm, 2 – 3 µm, 3 – 5 µm, 5 – 7 µm, 7 – 10 µm, 10 – 12 µm, 12 – 15 µm, 15 – 20 µm, or any combination of ranges thereof, In some cases, e.g., when measured across a 1 mm cross-section distance of the anode, the sum of individual spaces may account for a total of 1 – 5% of the cross-section distance, alternatively 5 – 10%, 10 – 15%, 15 – 20%, 20 – 25%, 25 – 30%, 30 – 35%, or 35 – 40% of the cross-section distance, or any combination of ranges thereof. The cross-section distance may be at about 50% of the average thickness of the storage layer segments.

[0022] As mentioned, lithium storage layer segments may form as a result ofelectrochemical cycling (lithiation and delithiation), but other methods exist for producing a segmented lithium storage layer. For example, lithium storage layer material may be removed by patterned laser ablation or by etching through a patterned resist material to form spaced apart lithium storage layer segments.

[0023] In some cases, lithium storage layer segments may be pattern-deposited onto thecurrent collector. For example, the first lithium storage layer may be deposited by CVD or PVD through a shadow mask having a pattern corresponding to the desired pattern of the segments and gaps. In some cases, the surface layer may be patterned such that the first lithium storage layer material selectively forms an adherent deposit over the surface layer, for example, as described in U.S. Patent Application Publication No.2020 / 0411851. In some examples, lithium storage layer segments may be prepatterned on a donor sheet and transferred to the current collector. In some cases, the first lithium storage layer segments may be electrodeposited through a patterned photoresist (e.g., it is known that silicon, tin, and / or germanium can each be electrodeposited from solution). In some cases, lithium storage layer segments may be pattern-printed (e.g., by inkjet, offset, gravure, flexographic, or some other printing technology) from a mixture or slurry containing ahigh weight percent of silicon, tin, or germanium (e.g., a weight percent of at least 40%, or alternatively at least 50%, 60%, 70%, or 80%) followed by drying and / or sintering.

[0024] In some examples, the first lithium storage layer may alternatively include highaspect ratio lithium storage nanostructures such as silicon nanowires rather than a layer or segments. A few examples of such nanostructures are shown in FIG.3 that may optionally be used as the first lithium storage layer instead of the layer or segments. The second lithium storage layer is not illustrated for clarity. For example, high aspect ratio lithium storage nanostructures may include as nanowires 190, nanopillars 192, and nanotubes 194 provided over a current collector 180. Unless noted otherwise, the term “lithium storage nanostructure” herein generally refers to an alloying lithium storage active material structure (for example, a structure of silicon, germanium, or their alloys) having at least one cross-sectional dimension that is less than about 2,000 nm, other than a dimension approximately normal to an underlying substrate (such as a layer thickness) and excluding dimensions caused by random pores and channels. “High aspect ratio” nanostructures have an aspect ratio greater than 4:1, where the aspect ratio is generally the height or length of a feature (which may be measured along a feature axis aligned at an angle of 45 to 90 degrees relative to the underlying current collector surface) divided by the width of the feature (which may be measured generally orthogonal to the feature axis).

[0025] In some cases (as illustrated in FIGS. 1, 2A, and 2B), the first lithium storagelayer may be substantially free of high aspect ratio lithium storage nanostructures. In some examples, the first lithium storage layer, e.g., a continuous porous lithium storage layer, is considered “substantially free” of high aspect ratio lithium storage nanostructures when the anode has an average (e.g., mean, median, or mode) of fewer than 10 lithium storage nanostructures per 1600 square micrometers (in which the number of lithium storage nanostructures is the sum of the number of nanowires, nanopillars, and nanotubes in the same unit area), such lithium storage nanostructures having an aspect ratio of 4:1 or higher. Alternatively, there is an average of fewer than 1 such lithium storage nanostructures per 1600 square micrometers. In some examples, an anode may have patterned regions of lithium storage layer 107 and other regions that may purposefully include lithium storage nanostructures. In such cases, the term “substantially free” may refer just to a particular region of the lithium storage layer.

[0026] FIG. 4A is a cross-sectional view of a lithium-ion battery cell according to somenon-limiting examples. Cell 465 includes an anode 400, a cathode 440, and an electrolyte 430 disposed therebetween. Electrolyte 430 may be a liquid electrolyte or a solid-stateelectrolyte. When liquid, cell 465 typically further includes a porous separator (not shown) between the anode and cathode. Anode 400 may be as described with respect to FIG.1 and include an anode current collector 403 and a lithium storage structure 402 including a first lithium storage layer 407 disposed over current collector 403 and a second lithium storage layer 409 disposed over the first lithium storage layer. Although not illustrated, the anode may instead include a segmented first lithium storage layer as described in FIGS. 2A and 2B. Cathode 440 may include a cathode current collector 443 and a cathode active material layer 447 disposed in contact with the cathode current collector facing the lithium storage structure 402.

[0027] In some examples, electrolyte 430 may be a solid-state electrolyte (SSE 430).SSE materials are described in more detail elsewhere herein. In a non-limiting example, the first lithium storage layer 407 includes at least 50 atomic % silicon (alternatively at least 60%, at least 70%, or at least 80%), the second lithium storage layer 409 includes a lithium titanium oxide (LTO), a titanium niobium oxide (TNO), a niobium oxide, or an aluminum niobium oxide, and SSE 430 includes a solid sulfide. Such non-alloying metal compounds may provide a more robust interface with a sulfide SSE than silicon resulting in improved cell performance. When the anode has a segmented structure similar to that shown in FIG.2A, the SSE 430 may optionally extend into the spaces between segments (partially or fully), or alternatively, may extend across (bridge) the spaces leaving the spaces substantially unfilled.

[0028] The anode and cathode current collectors may be connected to a voltage source(not shown) and the cell may undergo one or more charge / discharge cycles which may also be referred to herein as one or more cycles or voltage cycles. In some cases, a pressure may optionally be applied between the anode and cathode, e.g., during electrochemical formation and / or normal use cycling of the finished cell.

[0029] In some cases, an SSE may include two or more layers of different SSEmaterials. FIG.4B is a cross-sectional view of a lithium-ion battery cell according to some non-limiting examples. Cell 465B may be similar to cell 465, but here the electrolyte is a multilayer SSE 430B. A first SSE layer 430-1 including a first SSE material is provided adjacent to the anode. A second SSE layer 430-2 including a second SSE material is interposed between the first SSE layer 430-1 and the cathode 440. The second SSE material has a chemical composition different from the first SSE material.

[0030] The materials and properties of each SSE layer may be independently selectedand adjacent SSE layers are generally different in some way. Such properties may include,but are not limited to, thickness, elasticity, compressibility, viscosity, melting point, lithium-ion conductivity, electrical conductivity, lithium-ion concentration, lithium counterions, cross-linking agents, additives, chemical composition, compositional gradients, or the like. Each SSE layer may be provided by the same coating / application method or by different methods. In some cases, relative to the second SSE layer 430-2, the first SSE layer 430-1 may have higher elasticity, higher compressibility, and / or lower viscosity. In other examples, opposite properties may exist. In some cases, the SSE layer adjacent the cathode active material may have lower elasticity, lower compressibility, and / or higher viscosity than at least the SSE layer adjacent the anode. In other cases, the opposite properties may exist. In some examples, instead of two SSE layers, there may be three or more. In some cases, the first SSE layer 430-1 includes a solid polymer electrolyte and the second SSE layer 430-2 includes a solid inorganic electrolyte such as a solid sulfide.

[0031] When the anode has a segmented structure similar to that shown in FIG. 2A, theSSE 430B may optionally extend into the spaces between segments (partially or fully), or alternatively, may extend across (bridge) the spaces leaving the spaces substantially unfilled. In some cases, just the first SSE layer 430-1 extends into the spaces.

[0032] Anode

[0033] Current Collector

[0034] In some examples, the electrically conductive layer may have a conductivity ofat 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 conductivity of less than 108S / m. For anodes having low storage capacity and / or where there are no concerns regarding anode deformation during use, a wide variety of conductive materials may be used as the electrically conductive layer.

[0035] In some cases, the electrically conductive 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 layers of metal. In some cases, the electrically conductive layer may be a clad foil. In some examples, the electrically conductive layer includes an electricallyconductive 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 cases, 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.

[0036] When higher tensile strength is desirable, e.g., where Rm is greater than 450MPa, 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 copper-based 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 Rm in a range of 500 – 1200 MPa.

[0037] Alternatively, a mesh or sheet of electrically conductive carbon, including butnot limited to, those formed from bundled carbon nanotubes or nanofibers, may in some cases provide for higher tensile strength electrically conductive layers. In some cases, an electrically conductive metal interlayer may be interposed between the electrically conductive carbon and an optional surface layer.

[0038] 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.

[0039] General surface roughness

[0040] In some examples, the current collector may be characterized as having asurface 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 examples, the current collector may be characterized as having both a surface roughness Rz ≥ 2.5 µm and a surface roughness Ra ≥ 0.25 µm. In some cases, Rz is in a range of 2.5 – 3.0 µm, alternatively 3.0 – 3.5 µm, alternatively 3.5 – 4.0 µm, alternatively 4.0 – 4.5 µm, alternatively 4.5 – 5.0 µm, alternatively 5.0 – 5.5 µm, alternatively 5.5 – 6.0 µm, alternatively 6.0 – 6.5 µm, alternatively 6.5 – 7.0 µm, alternatively 7.0 – 8.0 µm, alternatively 8.0 – 9.0 µm, alternatively 9.0 to 10µm, 10 to 12 µm, 12 to 14 µm or any combination of ranges thereof. In some examples, Rais in a range of 0.25 – 0.30 µm, alternatively 0.30 – 0.35 µm, alternatively 0.35 – 0.40 µm, alternatively 0.40 – 0.45 µm, alternatively 0.45 – 0.50 µm, alternatively 0.50 – 0.55 µm, alternatively 0.55 – 0.60 µm, alternatively 0.60 – 0.65 µm, alternatively 0.65 – 0.70 µm, alternatively 0.70 – 0.80 µm, alternatively 0.80 – 0.90 µm, alternatively 0.90 – 1.0 µm, alternatively 1.0 – 1.2 µm, alternatively 1.2 – 1.4 µm, or any combination of ranges thereof.

[0041] In some examples, some or most of the surface roughness of the currentcollector 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.

[0042] In some examples, the electrically conductive layer may include rougheningfeatures, 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, pitted features, or the like.

[0043] Alternatively, or in combination with the roughening features, the electricallyconductive layer may undergo another electrochemical, chemical, or physical treatment to impart a desired surface roughness prior to formation of the surface layer.

[0044] 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.

[0045] Surface layer

[0046] In some examples, a surface layer may provide a chemical composition thatpromotes 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.

[0047] The thickness of a surface layer may be as low as a monolayer in some cases. Insome examples, the thickness of the surface layer is in a range of 0.0002 µm to 0.0005 µm, alternatively 0.0005 µm to 0.001 µm, alternatively 0.001 µm to 0.005 µm, alternatively 0.002 µm to 0.005 µm, alternatively, 0.005 µm to 0.01 µm, alternatively 0.01 µm to 0.02 µm, alternatively 0.02 µm to 0.03 µm, alternatively 0.03 µm to 0.05 µm, alternatively 0.05 µm to 0.1 µm, alternatively 0.1 µm to 0.2 µm, alternatively 0.2 µm to 0.5 µm, alternatively 0.5 µm to 1 µm, alternatively 1 µm to 2 µm, alternatively 2 µm to 5 µm or any combination of ranges thereof.

[0048] In some examples, the surface layer or sublayer may include a metal-oxygencompound. 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, ametal-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 a siloxane, 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. 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.

[0049] First Lithium Storage Layer / Alloying Lithium Storage Material

[0050] The following discussion is applicable to alloying lithium storage materialsprovided in either the first lithium storage layer or to first lithium storage layer segments. For convenience, the discussion in this section may sometimes simply refer to a lithium storage layer, but it is to be understood that such reference within this section is to the first lithium storage layer or segments having the alloying lithium storage material.

[0051] In some examples, the first lithium storage layer may be a porous materialcapable of reversibly incorporating lithium, e.g., continuous porous lithium storage layer, by an alloying process. In some examples, the first lithium storage layer includes silicon, germanium, antimony, tin, silver, or a mixture of two or more of these elements. The alloying material may further include a minor amount of other metal elements such as Al, Co, Zn, Ni, Cr, Mn, Cu, Ag, Au, or Mo (or a combination). In some examples, the first lithium storage layer is substantially amorphous. In some examples, a first lithium storage layer includes substantially amorphous silicon. Such substantially amorphous storage layers may include a small amount (e.g., less than 20 atomic %) of crystalline material dispersed therein. The first lithium storage layer may include dopants such as hydrogen, boron, phosphorous, carbon, oxygen, sulfur, fluorine, aluminum, gallium, indium, arsenic, antimony, bismuth, nitrogen, or metallic elements. In some examples the first lithium storage layer may include porous substantially amorphous hydrogenated silicon (a-Si:H), having, e.g., a hydrogen content of from 0.1 to 20 atomic %, or alternatively higher. In some examples, the first lithium storage layer may include methylated amorphous silicon. Note that, unless referring specifically to hydrogen content, any atomic % metric used herein for a lithium storage material or layer refers to atoms other than hydrogen.

[0052] In some examples, the first lithium storage layer, e.g., a continuous porouslithium storage layer, may include at least 40 atomic % silicon, germanium or a combination thereof, alternatively at least 50 atomic %, alternatively at least 60 atomic %,alternatively at least 70 atomic %, alternatively, at least 80 atomic %, alternatively at least 90 atomic %. In some examples, a first lithium storage layer, e.g., a continuous porous lithium storage layer, may include at least 40 atomic % silicon, alternatively at least 50 atomic %, alternatively at least 60 atomic %, alternatively at least 70 atomic %, alternatively, at least 80 atomic %, alternatively at least 90 atomic %, alternatively at least 95 atomic %, alternatively at least 97 atomic %, alternatively at least 98%, or alternatively at least 99%. Note that in the case of prelithiated anodes as discussed below, the lithium content is excluded from this atomic % characterization.

[0053] In some examples, a first lithium storage layer, e.g., a continuous porous lithiumstorage layer, is substantially free (i.e., the lithium storage layer includes less than 1 % by weight, alternatively less than 0.5 % by weight, alternatively less than 0.3% by weight, alternatively less than 0.1% by weight, alternatively less than 0.01% by weight) of carbon- based binders, graphitic carbon, graphene, graphene oxide, reduced graphene oxide, carbon black and conductive carbon. A few non-limiting examples of carbon-based binders may include organic polymers such as those based on styrene butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, or polyacrylonitrile.

[0054] The first lithium storage layer, e.g., a continuous porous lithium storage layer,may include voids or interstices (pores), which may be random or non-uniform with respect to size, shape, and distribution. In some cases, this porosity may be tuned (e.g., by adjusting deposition conditions) to produce an internal specific surface area of the first 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 does not result in, or result from, the formation of any recognizable lithium storage nanostructures such as nanowires, nanopillars, nanotubes, ordered nanochannels or the like. In some examples, the pores may be polydisperse. A porous first lithium storage layer, e.g., a continuous porous lithium storage layer, may in some cases have a porosity in a range of 2% - 5%, 5% - 10%, 10% - 20%, 20% - 30%, 30% - 40%, 40% - 50%, or any combination of ranges thereof, e.g., as measured by the Barrett-Joyner-Halena (BJH) measurement.

[0055] In some examples, the first lithium storage layer, e.g., a continuous porouslithium storage layer, may be characterized as nanoporous. In some examples the lithium storage layer, e.g., a continuous porous lithium storage layer, has an average density in a range of 1.0 - 1.1 g / cm3, alternatively 1.1 – 1.2 g / cm3, alternatively 1.2 – 1.3 g / cm3,alternatively 1.3 – 1.4 g / cm3, alternatively 1.4 – 1.5 g / cm3, alternatively 1.5 – 1.6 g / cm3, alternatively 1.6 – 1.7 g / cm3, alternatively 1.7 – 1.8 g / cm3, alternatively 1.8 – 1.9 g / cm3, alternatively 1.9 – 2.0 g / cm3, alternatively 2.0 – 2.1 g / cm3, alternatively 2.1 – 2.2 g / cm3, alternatively 2.2 – 2.25 g / cm3, alternatively 2.25 – 2.29 g / cm3, or any combination ofranges thereof, and includes at least 70 atomic % silicon, 80 atomic % silicon, alternativelyat least 85 atomic % silicon, alternatively at least 90 atomic % silicon, alternatively at least 95 atomic % silicon, alternatively at least 97 atomic % silicon, alternatively at least 98 atomic % silicon, alternatively at least 99 atomic % silicon. Note that a density of less than 2.3 g / cm3is evidence of the porous nature of a-Si containing lithium storage layers. Density is mass divided by volume, each of which (mass and volume) and can be determined by well-known measurement methods. An average density may include 3 measurements made within an active area of the anode, i.e., the anode area suitable for use in a lithium-ion battery. In some cases, as compared to the density of substantially non- porous reference sample of the first lithium storage layer active material, the first lithium storage layer has a “relative density” in a range of 50% - 60%, 60% - 70%, 70% - 80%, 80% - 90%, 90% - 95%, 95% - 98%, or any combination of ranges thereof.

[0056] In some examples, the majority of active material (e.g., silicon, tin, germaniumor alloys thereof) of the first lithium storage layer, e.g., a continuous porous lithium storage layer, has substantial lateral connectivity across portions of the current collector creating, such connectivity extending around random pores and interstices. It should be noted that the first 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 first 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. The abutting columns may be characterized by an average height and average width, and generally have a height-to-width aspect ratio of less than 4:1, alternatively less than 3:1, alternatively less than 2:1, alternatively less than 1:1. Such abutting columns are laterally continuous. In some examples, the first lithium storage layer, e.g., a continuous porous lithium storage layer, may include a matrix of connected nanoparticle aggregates. In some examples, the lithium storage layer may include a mixture of amorphous and crystalline silicon, e.g., nano-crystalline silicon having an average grain size of less than about 100 nm, alternatively less than about 50 nm, 20 nm,10 nm, or 5 nm. In some cases, the first lithium storage layer may include up to 30 atomic % nano-crystalline silicon relative to all silicon in the lithium storage layer.

[0057] Herein, a continuous porous lithium storage layer is one that: i) is porous (e.g.,as evidenced by a relative density in a range of 50% - 95%, or as evidenced by a BJH porosity measurement in a range of 5% - 50%); ii) is substantially free of high aspect ratio nanostructures as discussed above; iii) is substantially free of carbon based binders as discussed above; and iv) is characterized by lateral connectivity as discussed above. Note that in some examples, a first lithium storage layer or a first lithium storage layer segment may be a continuous porous lithium storage layer.

[0058] In some examples, the lithium storage layer, e.g., a continuous porous lithiumstorage layer, includes a substoichiometric oxide of silicon (SiOx), germanium (GeOx) or tin (SnOx) wherein the ratio of oxygen atoms to silicon, germanium or tin atoms is less than 2:1, i.e., x < 2, alternatively less than 1:1, i.e., x < 1. In some examples, x is in a range of 0.02 to 0.95, alternatively 0.02 to 0.10, alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95, alternatively 0.95 to 1.25, alternatively 1.25 to 1.50, or any combination of ranges thereof.

[0059] In some examples, the lithium storage layer, e.g., a continuous porous lithiumstorage layer, includes a substoichiometric nitride of silicon (SiNy), germanium (GeNy) or tin (SnNy) wherein the ratio of nitrogen atoms to silicon, germanium or tin atoms is less than 1.25:1, i.e., y < 1.25. In some examples, y is in a range of 0.02 to 0.95, alternatively 0.02 to 0.10, alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95, alternatively 0.95 to 1.20, or any combination of ranges thereof. Lithium storage layer having a substoichiometric nitride of silicon may also be referred to as nitrogen-doped silicon or a silicon-nitrogen alloy.

[0060] In some examples, the lithium storage layer, e.g., a continuous porous lithiumstorage layer, includes a substoichiometric oxynitride of silicon (SiOxNy), germanium (GeOxNy), or tin (SnOxNy) wherein the ratio of total oxygen and nitrogen atoms to silicon, germanium or tin atoms is less than 1:1, i.e., (x + y) < 1. In some examples, (x + y) is in a range of 0.02 to 0.95, alternatively 0.02 to 0.10, alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95, or any combination of ranges thereof.

[0061] As noted elsewhere, rather than being provided a layer or segments, the firstlithium storage layer may include nanostructures. In some cases, the first lithium storage layer may include nanowires, e.g., as described in US Patent 9,923,201, which are incorporated by reference herein for all purposes.

[0062] The thickness or mass per unit area of the first lithium storage layer depends onthe storage material, desired charge capacity and other operational and lifetime considerations. Increasing the thickness typically provides more capacity. If the first lithium storage layer becomes too thick, electrical resistance may increase and the stability may decrease. In some examples, the anode may be characterized as having an active silicon areal density of at least 0.2 mg / cm2, alternatively at least 0.5 mg / cm2, alternatively at least 1.0 mg / cm2, alternatively at least 1.5 mg / cm2, alternatively at least 3 mg / cm2, alternatively at least 5 mg / cm2. In some examples, the lithium storage structure may be characterized as having an active silicon areal density in a range of 0.2 – 0.5 mg / cm2, alternatively in a range of 0.5 – 1.0 mg / cm2, alternatively in a range of 1.0 – 1.5 mg / cm2, alternatively in a range of 1.5 – 2 mg / cm2, alternatively in a range of 2 – 3 mg / cm2, alternatively in a range of 3 – 5 mg / cm2, alternatively in a range of 5 – 10 mg / cm2, alternatively in a range of 10 – 15 mg / cm2, alternatively in a range of 15 – 20 mg / cm2, or any combination of ranges thereof. “Active silicon” refers to the silicon in electrical communication with the current collector that is available for reversible lithium storage at the beginning of cell cycling, e.g., after anode electrochemical formation. “Areal density” refers to the surface area of the electrically conductive layer over which active silicon is provided. In some examples, not all of the silicon content is active silicon, i.e., some may be tied up in the form of non-active silicides or may be electrically isolated from the current collector.

[0063] In some examples, the first lithium storage layer has an average thickness of atleast 0.5 µm, alternatively at least 1 µm, alternatively at least 2.5 µm, alternatively at least 5 µm, alternatively at least 6.5 µm. In some examples, the first lithium storage layer, e.g., a continuous porous lithium storage layer, has an average thickness in a range of about 0.5 µm to about 50 µm. In some examples, the first lithium storage layer, e.g., a continuous porous lithium storage layer, has a thickness in a range of 1 – 1.5 µm, alternatively 1.5 – 2.0 µm, alternatively 2.0 – 2.5 µm, alternatively 2.5 – 3.0 µm, alternatively 3.0 – 3.5 µm, alternatively 3.5 – 4.0 µm, alternatively 4.0 – 4.5 µm, alternatively 4.5 – 5.0 µm, alternatively 5.0 – 5.5 µm, alternatively 5.5 – 6.0 µm, alternatively 6.0 – 6.5 µm, alternatively 6.5 – 7.0 µm, alternatively 7.0 – 8.0 µm, alternatively 8.0 – 9.0 µm, alternatively 9.0 – 10 µm, alternatively 10 – 15 µm, alternatively 15 – 20 µm, alternatively 20 – 25 µm, alternatively 25 – 30 µm, alternatively 30 – 40 µm, alternatively 40 – 50 µm, or any combination of ranges thereof.

[0064] In some examples, the alloying lithium storage material may have a gravimetriccapacity of at least 300 mAh / g, but preferably at least 500 mAh / g. In some examples, the alloying lithium storage material has a gravimetric capacity in a range of 1000 to 4000 mAh / g.

[0065] Second Lithium Storage Layer / Non-Alloying Metal Compound LithiumStorage Material

[0066] The following discussion is applicable to non-alloying metal compound lithiumstorage materials provided in the second lithium storage layer or second lithium storage layer segments. For convenience, the discussion in this section may sometimes simply refer to a lithium storage layer, but it is to be understood that such reference within this section is to the second lithium storage layer or segments having the non-alloying metal compound lithium storage material.

[0067] In some examples, the non-alloying metal compound is a conversion-typelithium storage material. For example, Equation 1 illustrates a non-limiting generalized electrochemical reaction where M is a metal (often a transition metal, particularly Co, Ni, Fe, or Mn) and X is an anionic species (e.g., an oxide, sulfide, phosphide, nitride, etc.). MX + nLi++ ne- ^^ M + LinX (1)

[0068] Electrochemical reduction of MX may in some cases form nanosized metalparticles M that are dispersed in a LinX matrix. Upon electrochemical oxidation, MX can be reproduced reversibly.

[0069] In some cases, the non-alloying metal compound includes a nickel oxide, acopper oxide, a manganese oxide, a tungsten oxide, a cobalt oxide, a chromium oxide, a zinc oxide, a tin oxide, a germanium oxide, or an antimony oxide. In some cases, the non- alloying metal compound includes a transition metal sulfide, a tin sulfide, a transition metal phosphide, a transition metal nitride, a transition metal fluoride, a transition metal hydroxide, a transition metal selenide, a titanium carbide, or a transition metal oxalate.

[0070] In some examples, the non-alloying metal compound is an intercalation-typelithium storage material. Some particularly useful non-limiting examples of intercalating- type materials may include those based on oxides of titanium, niobium, or vanadium, or combinations thereof. In some cases, the non-alloying metal compound includes a lithium titanium oxide (LTO), a niobium oxide, an aluminum niobium oxide, a titanium niobium oxide (TNO), or a lithium vanadium oxide, any of which, may optionally further include some amount of chromium or cerium.

[0071] In some examples, the non-alloying metal compound lithium storage materialmay have a gravimetric capacity of at least 100 mAh / g, but preferably at least 200 mAh / g. In some examples, the non-alloying metal compound has a gravimetric capacity in a range of 500 to 1400 mAh / g.

[0072] In some examples, the second lithium storage layer may have a thickness (e.g.,as measured from the top of the first lithium storage layer in the z-axis direction) in a range of 10 – 50 nm, alternatively 50 – 100 nm, alternatively 100 – 500 nm, alternatively 500 nm - 1 µm, alternatively 1 – 1.5 µm, alternatively 1.5 – 2.0 µm, alternatively 2.0 – 2.5 µm, alternatively 2.5 – 3.0 µm, alternatively 3.0 – 3.5 µm, alternatively 3.5 – 4.0 µm, alternatively 4.0 – 4.5 µm, alternatively 4.5 – 5.0 µm, alternatively 5.0 – 5.5 µm, alternatively 5.5 – 6.0 µm, alternatively 6.0 – 6.5 µm, alternatively 6.5 – 7.0 µm, alternatively 7.0 – 8.0 µm, alternatively 8.0 – 9.0 µm, alternatively 9.0 – 10 µm, alternatively 10 – 15 µm, alternatively 15 – 20 µm, alternatively 20 – 25 µm, alternatively 25 – 30 µm, alternatively 30 – 40 µm, alternatively 40 – 50 µm, or any combination of ranges thereof.

[0073] Lithium storage structure

[0074] The desired areal charge capacity of the anode, i.e., the combined reversiblecharge capacities of first and second lithium storage layers, 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. In some cases, at least 30% of the total areal charge capacity of anode is assignable to the first lithium storage layer, alternatively at least 50%, alternatively at least 70%. In some cases, relative to the total areal charge capacity of the anode, the areal charge capacity assignable to the first lithium storage layer is in a range of 30 – 50%, 50 – 70%, 70 – 80%, 80 – 90%, 90 – 95%, or 95 – 99%, or any combination ranges thereof.

[0075] In some examples, the second lithium storage layer has a lower gravimetriccapacity than the first lithium storage layer. In some examples, the second lithium storagelayer has lower thickness than the first lithium storage layer. For example, compared to the first lithium storage layer, the second lithium storage layer may have a relative thickness in a range of 1 – 5%, 5 – 10%, 10 – 25%, 25 – 50%, 25 – 50%, or any combination of ranges thereof.

[0076] CVD

[0077] CVD generally involves flowing a precursor gas, a gasified liquid in terms ofdirect 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 first lithium storage layer, the second lithium storage layer, the optional surface layer, an optional supplemental layer (see below) or other 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).

[0078] As mentioned, a lithium storage layer may be provided by plasma-enhancedchemical 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 silicon layer (optionally doped) over the surface layer. In some examples, PECVD is used to deposit a substantially amorphous continuous porous silicon layer over the surface layer.

[0079] In PECVD processes, according to various implementations, a plasma may begenerated 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.

[0080] PECVD process conditions (temperatures, pressures, precursor gases, carriergasses, 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.

[0081] In some cases, rather than depositing a lithium storage layer (or some otherlayer mentioned above) by CVD or PECVD, it may be formed by a physical vapor deposition (PVD) process such as by sputtering. Although the deposition rates of sputtering are typically lower than PECVD, sputtering may be suitable for some applications, e.g., those that require relatively lower loadings of the active material such as silicon. For example, in some examples, a lithium storage layer formed by a sputtering process may have a thickness of less than about 15 µm, alternatively less than about 10 µm, alternatively less than 7 µm, alternatively less than 5 µm, alternatively less than 3 µm. In some examples, the first lithium storage layer may be formed by PECVD and the second lithium storage layer may be formed by PVD such as sputtering.

[0082] Other anode features

[0083] The anode may optionally include various additional layers and features. Thecurrent 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 structure. 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, ink jet 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.

[0084] A supplemental layer should be reasonably conductive to lithium ions, i.e.,permit lithium ions to move into and out of the lithium storage structure 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 electricalconductivity and does not reversibly store lithium (i.e., it is generally not an active lithium storage layer material).

[0085] Some non-limiting examples of materials used in a supplemental layer includemetal 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 LixSiyAl2O3 (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 0.1 – 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.

[0086] In some examples, the lithium storage structure, may be at least partiallyprelithiated prior to battery assembly. That is, some lithium may be incorporated into the lithium storage structure to form a lithiated storage structure even prior to a first battery cycle. Note that “lithiated storage structure” simply means that at least some of the potential storage capacity of the lithium storage structure 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 structure, 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.

[0087] In some examples prelithiation may include depositing lithium metal over thelithium storage structure, e.g., by evaporation, e-beam or sputtering, or by contacting the anode with lithium foil, lithium-containing particles, or the like. In some cases, prelithiation of the first lithium storage layer may be performed prior to deposition of the second lithium storage layer. In some examples, prelithiation may include incorporatinglithium by electrochemical reduction of lithium ion in prelithiation solution. In some examples, prelithiation may include a thermal treatment to aid the diffusion of lithium into the lithium storage layer(s).

[0088] 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 first lithium storage layer.

[0089] In some examples, thermally treating the anode may be done in a controlledenvironment having a low oxygen and water (e.g., less than 10 ppm or partial pressure of less than 0.1 Torr, alternatively less than 0.01 Torr content to prevent degradation). In some examples, anode thermal treatment may be carried out using an oven, infrared heating elements, contact with a hot plate or exposure to a flash lamp. The anode thermal treatment temperature and time depend on the materials of the anode. In some examples, anode thermal treatment includes heating the anode to a temperature of at least 50 ºC, optionally in a range of 50 ºC to 950 ºC, alternatively 100 ºC to 250 ºC, alternatively 250 ºC to 350 ºC, alternatively 350 ºC to 450 ºC, alternatively 450 ºC to 550 ºC, alternatively 550 ºC to 650 ºC, alternatively 650 ºC to 750 ºC, alternatively 750 ºC to 850 ºC, alternatively 850 ºC to 950 ºC, or a combination of these ranges. In some examples, the thermal treatment may be applied for a time period of 0.1 to 120 minutes.

[0090] In some examples one or more processing steps described above may beperformed using roll-to-roll methods wherein the electrically conductive layer or current collector is in the form of a rolled film, e.g., a roll of metal foil, mesh or fabric.

[0091] Electrolyte

[0092] The nonaqueous lithium-ion electrolyte may be a liquid, a solid, or a gel, orsome 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.

[0093] Some non-limiting examples of non-aqueous solvents suitable for some lithiumion cells include the following: cyclic carbonates (e.g., ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), butylene carbonate (BC) andvinylethylene 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-dioxane, 1,2- dimethoxyethane (DME), 1,2-diethoxyethane and 1,2-dibutoxyethane), nitriles (e.g., acetonitrile and adiponitrile) linear esters (e.g., methyl propionate, methyl pivalate, butyl 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 divinyl sulfone), and combinations thereof.

[0094] Non-aqueous liquid solvents can be employed in combination. Examples ofthese combinations include combinations of cyclic carbonate-linear carbonate, cyclic carbonate-lactone, 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 or a linear carbonate is in a range of 1:9 to 10:1, alternatively 2:8 to 7:3.

[0095] A salt for liquid electrolytes may include one or more of the following non-limiting examples: LiPF6, LiBF4, LiClO4, LiAsF6, LiN(CF3SO2)2(“LiTFSI”), LiN(C2F5SO2)2, LiCF3SO3, LiC(CF3SO2)3, LiPF4(CF3)2, LiPF3(C2F5)3, LiPF3(CF3)3, LiPF3 (iso-C3F7)3, LiPF5(iso-C3F7), lithium salts having cyclic alkyl 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.

[0096] 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.

[0097] Additives may be included in the electrolyte to serve various functions such asto 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 aminesor borate compounds may act as cathode protection agents. Lewis acids can be added to stabilize fluorine-containing anion such as (PF6)-. Safety protection agents include those to protect overcharge, e.g., anisoles, or act as fire retardants, e.g., alkyl 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.

[0098] SSE

[0099] The solid-state electrolyte includes a source of mobile lithium ions that diffusebetween 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, LiPF6 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).

[0100] A few non-limiting examples of polymeric materials that may be used in theSSE 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, polycaprolactone, 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.

[0101] A few non-limiting classes of SIE material that may be used in the SSEcomposition include b-aluminas, LISICONs, thio-LISICONs, NASICONs, perovskites, antiperovskites, garnets, complex hydrides, and solid sulfides.

[0102] A few non-limiting classes of solid sulfides include ceramic sulfides, glasssulfides, and glass-ceramic sulfides. Glass sulfides show minimal long-range order that isidentified by the lack of peaks in the pattern resulting from x-ray diffraction (XRD) measurements. Glass-ceramic 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 Li6PS5Cl, LGPS materials such as Li10GeP2S12, and LPS materials such as Li7P3S11.

[0103] In some examples, under battery operating conditions, the SSE may have alithium-ion conductivity in a range of 0.001 mS / cm to 0.01 mS / cm, alternatively in arange of 0.01 mS / cm to 0.1 mS / cm, alternatively in a range of 0.1 mS / cm to 1.0 mS / cm,alternatively higher than 1 mS / cm.

[0104] The thickness of the SSE should be sufficient to prevent shorting between theanode 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 more conventional battery cells, the SSE may typically have a thickness in a range of 5 – 300 microns.

[0105] In some examples, an SSE may include a relatively small amount of organicsolvent, 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%.

[0106] In some examples, the solid-state electrolyte includes a material reversiblytransformable from a low flowability state to a high flowability state and back to a low flowability state. In some cases, this cycle may be available only once and such systems may be referred to as “singly reversible”. For example, an SSE in a first low flowability state may have a first chemical composition or morphology. After the high flowability state excursion, the SSE may revert to a second low flowability state and have a secondchemical composition or morphology different from the first. For example, the SSE may undergo a polymerization or cross-linking reaction during or after the high flowability state to form the second low flowability state that is no longer as readily transformable to a high flowability state. In some other examples, the cycle may be repeatable two or more times (“multiply reversible”). In some cases, the low flowability state may correspond to a glassy state or a solid state. In some examples, a high flowability state may correspond to a liquid state. In some examples, a transformation from a low to high flowability state may approximately correspond to an SSE material’s melting point, or alternatively, to a SSE material’s glass transition temperature (Tg). In some examples, transformation from a low flowability state to a high flowability state may be accomplished by application of energy to the cell so that the temperature of the SSE in the cell is raised to T1 where transformation can occur. In some examples, T1 may be at least 40 ^C, alternatively, at least 50 ^C, 60 ^C, 80 ^C, 100 ^C, 125 ^C, 150 ^C, 175 ^C, or 200 ^C. In some examples, T1may be in a range of 40 – 60 ^C, alternatively in a range of 60 – 80 ^C, 80 – 100 ^C, 100 – 125 ^C, 125 – 150 ^C, 150 – 175 ^C, 175 – 200 ^C, 200 – 225 ^C, 225 – 250 ^C, or any combination of ranges thereof. In some examples, compression may be applied to the cell (between the anode and cathode) while the SSE is in the high flowability state. Such compression may include a force of greater than 1 bar, alternatively greater than 1.5 bar, 2 bar, 3 bar, 4 bar, 5 bar, 7 bar, or 10 bar. In some cases, the compression is in a range of 1.1 – 1.5 bar, 1.5 – 2 bar, 2 – 3 bar, 3 – 4 bar, 4 – 5 bar, 5 – 7 bar, 7 – 10 bar, 10 – 15 bar, 15 – 20 bar, 20 – 30 bar, 30 – 50 bar, 50 – 75 bar, 75 – 100 bar, or any combination of ranges thereof.

[0107] In some examples, a high flowability state may be characterized by a viscositylower than 1 MPa-sec, alternatively less than 500 kPa-sec, 200 kPa-sec, 100 kPa-sec, 50 kPa-sec, 20 kPa-sec, 10 kPa-sec, 5 kPa-sec, 2 kPa-sec, 1 kPa-sec, 500 Pa-sec, 200 Pa-sec, 100 Pa-sec, 50 Pa-sec, 20 Pa-sec, 10 Pa-sec, 5 Pa-sec, 2 Pa-sec, 1 Pa-sec, 0.5 Pa-sec, 0.2 Pa-sec, or 0.1 Pa-sec. In some cases, the high flowability state may be characterized by a viscosity in a range of 0.001 – 0.01 Pa-sec, alternatively 0.01 – 0.1 Pa-sec, 0.1 – 1 Pa-sec, 1 – 10 Pa-sec, 10 – 100 Pa-sec, 100 – 1000 Pa-sec, 1 – 10 kPa-sec, 10 – 100 kPa-sec, 100 – 500 kPa-sec, or any combination of ranges thereof.

[0108] A low flowability state has a higher viscosity than a high flowability state by atleast a factor of 1.1x, alternatively by at least 1.5x, 2x, 5x, 10x, 20x, 50x, 100x, 200x, 500x, 1000x, 104x, or 105x. In some examples, a low flowability state may have aviscosity of at least 100 Pa-sec, alternatively at least 1k Pa-sec, alternatively at least 10k Pa-sec, alternatively at least 100 kPa-sec, alternatively at least 1 MPa-sec.

[0109] Transformation from the high flowability state to the low flowability state mayinclude active cooling to T2(or below), e.g., using chillers, heat pumps, or the like to remove heat from the cell. Alternatively, passive cooling may be used where radiative cooling occurs, e.g., when room temperature is at or below T2. In some cases, T2is less than T1, e.g., T2 may be 1 – 5 ^C lower than T1, or alternatively 5 – 10 ^C lower, 10 – 20 ^C lower, 20 – 30 ^C lower, 30 – 40 ^C lower, 40 – 50 ^C lower, 50 – 75 ^C lower, 75 – 100 ^C lower, 100 – 150 ^C lower, or any combination of ranges thereof, or even more than 150^C lower.

[0110] In some cases, transformation between a low flowability state and a highflowability state may be done during electrochemical formation to allow the SSE material to flow into gaps or spaces that may form in the lithium storage structure during such electrochemical formation. During normal battery operation of charging and discharging (after electrochemical formation), the cell may in some cases stay in the low flowability state, but in some other cases, may be heated to its high flowability state during normal battery operation or periodically during the life of the battery cell.

[0111] Cathode

[0112] Positive electrode (cathode) active materials include, but are not limited to,lithium metal oxides or compounds (e.g., LiCoO2, LiFePO4, LiMnO2, LiNiO2, LiMn2O4, LiCoPO4, LiNixCoyMnzO2, LiNiXCoYAlZO2, LiFe2(SO4)3, or Li2FeSiO4), carbon fluoride, metal fluorides such as iron fluoride (FeF3), 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 typically provided on, or in electrical communication with, an electrically conductive cathode current collector.

[0113] Battery Format

[0114] In some examples, battery cells can be formed into multilayer stacks of anodesand 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.

[0115] FIG. 5 is a schematic cross-sectional view of a non-limiting example of batterycell. 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. The anodes 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 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 belocated 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.

[0116] Separator

[0117] The battery may further include a so-called “separator” between the anode andcathode, 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 µm and high bulk puncture strengths.

[0118] In some examples, electrochemical cycling conditions may be set to utilize onlya portion of the theoretical charge / discharge capacity of lithium storage layer materials. This may in some cases increase the lifetime of the battery cell. 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.

[0119] Enumerated Embodiments

[0120] Still further embodiments herein include the following non-limiting enumeratedembodiments. Enumerated embodiment 1. An anode for an energy storage device, the anode including: a current collector; a first lithium storage layer overlaying the current collector, the first lithium storage layer including an alloying lithium storage material; and a second lithium storage layer overlaying the first lithium storage layer, the second lithium storage layer including a non-alloying metal compound lithium storage material selected from the group consisting of a conversion-type material and an intercalation-type material.Enumerated embodiment 2. The anode of enumerated embodiment 1, wherein the first lithium storage layer includes at least 40 atomic % silicon, tin, germanium, or a combination thereof. Enumerated embodiment 3. The anode of enumerated embodiment 1 or 2, wherein the first lithium storage layer is substantially free of high aspect ratio lithium storage nanostructures. Enumerated embodiment 4. The anode according to any of enumerated embodiments 1 through 3, wherein the first lithium storage layer is a continuous porous lithium storage layer. Enumerated embodiment 5. The anode according to any of enumerated embodiments 1 through 4, wherein the first lithium storage layer includes a sub- stoichiometric nitride of silicon or a sub-stoichiometric oxide of silicon. Enumerated embodiment 6. The anode according to any of enumerated embodiments 1 through 5, wherein the first lithium storage layer includes at least 50 atomic % amorphous silicon, optionally at least 80 atomic % amorphous silicon. Enumerated embodiment 7. The anode of according to any of enumerated embodiments 1 through 6, wherein the first lithium storage layer includes columns of silicon nanoparticle aggregates. Enumerated embodiment 8. The anode according to any of enumerated embodiments 1 through 7, wherein the first lithium storage layer is substantially free of carbon-based binders and conductive carbon. Enumerated embodiment 9. The anode according to any of enumerated embodiments 1 through 8, wherein the first lithium storage layer is a segmented first lithium storage layer. Enumerated embodiment 10. The anode according to any of enumerated embodiments 1 through 9, wherein the first lithium storage layer is deposited onto the current collector by a PVD or CVD process. Enumerated embodiment 11. The anode of enumerated embodiment 10, wherein the first lithium storage layer is deposited onto the current collector by the CVD process, and the CVD process is a PECVD process. Enumerated embodiment 12. The anode according to any of enumerated embodiments 1 through 11, wherein the non-alloying metal compound lithium storage material includes a metal oxide.Enumerated embodiment 13. The anode of enumerated embodiment 12, wherein the non-alloying metal compound lithium storage material includes a titanium oxide, a lithium titanium oxide (LTO), a niobium oxide, an aluminum niobium oxide, or a titanium niobium oxide (TNO). Enumerated embodiment 14. The anode of enumerated embodiment 12, wherein the non-alloying metal compound lithium storage material includes a nickel oxide, a copper oxide, a manganese oxide, a tungsten oxide, a vanadium oxide, a cobalt oxide, a chromium oxide, a zinc oxide, a tin oxide, a germanium oxide, or an antimony oxide. Enumerated embodiment 15. The anode according to any of enumerated embodiments 1 through 11, wherein the non-alloying metal compound lithium storage material includes a transition metal sulfide, a tin sulfide, a transition metal phosphide, a transition metal nitride, a transition metal fluoride, a transition metal hydroxide, a transition metal selenide, a titanium carbide, or a transition metal oxalate. Enumerated embodiment 16. The anode according to any of enumerated embodiments 1 through 15, wherein the second lithium storage layer is deposited by a PVD or CVD process. Enumerated embodiment 17. The anode according to any of enumerated embodiments 1 through 15, wherein the second lithium storage layer is deposited from a slurry including the non-alloying metal compound lithium storage material. Enumerated embodiment 18. The anode according to any of enumerated embodiments 1 through 17, wherein the first lithium storage layer has a higher areal storage capacity than the second lithium storage layer, optionally wherein, relative to a total areal storage capacity of the anode, an areal storage capacity assignable to the first lithium storage layer is in a range of 80 – 99%. Enumerated embodiment 19. The anode according to any of enumerated embodiments 1 through 18, wherein the first lithium storage layer has a greater thickness than the second lithium storage layer, optionally wherein, compared to the first lithium storage layer, the second lithium storage layer has a relative thickness in a range of 1 –– 25%. Enumerated embodiment 20. The anode according to any of enumerated embodiments 1 through 19, wherein the first and second lithium storage layers are segmented lithium storage layers.Enumerated embodiment 21. The anode according to any of enumerated embodiments 1 through 19, wherein the first lithium storage layer is a segmented lithium storage layer including segments, and the second lithium storage layer is provided over the segments and within spaces between the segments. Enumerated embodiment 22. The anode of enumerated embodiment 21, wherein the second lithium storage layer is in contact with the current collector. Enumerated embodiment 23. The anode according to any of enumerated embodiments 1 through 22, wherein the current collector is characterized by a surface roughness Ra ≥ 250 nm. Enumerated embodiment 24. The anode according to any of enumerated embodiments 1 through 23, wherein the current collector includes an electrically conductive layer including a metal or a conductive carbon. Enumerated embodiment 25. The anode of enumerated embodiment 24, wherein the electrically conductive layer includes copper, nickel, titanium, stainless steel, or a combination thereof. Enumerated embodiment 26. The anode of enumerated embodiment 24, wherein the electrically conductive layer includes a copper alloy including copper, magnesium, silver, and phosphorous. Enumerated embodiment 27. The anode of enumerated embodiment 24, wherein the electrically conductive layer includes a copper alloy including copper, iron, and phosphorus. Enumerated embodiment 28. The anode of enumerated embodiment 24, wherein the electrically conductive layer includes a copper alloy including brass or bronze. Enumerated embodiment 29. The anode of enumerated embodiment 24, wherein the electrically conductive layer includes a copper alloy including copper, nickel, and silicon. Enumerated embodiment 30. The anode according to any of enumerated embodiments 24 through 29, wherein the electrically conductive layer or current collector is characterized by a tensile strength in a range of 500 to 1200 MPa. Enumerated embodiment 31. The anode according to any of enumerated embodiments 24 through 30, wherein the electrically conductive layer includes a metal foil.Enumerated embodiment 32. The anode according to any of enumerated embodiments 24 through 29, wherein the current collector further includes an insulating substrate, and wherein the electrically conductive layer overlays the insulating substrate. Enumerated embodiment 33. The anode of enumerated embodiment 24, wherein the electrically conductive layer includes a mesh of electrically conductive carbon. Enumerated embodiment 34. The anode according to any of enumerated embodiments 24 through 33, further including a surface layer interposed between the electrically conductive layer and the first lithium storage layer. Enumerated embodiment 35. The anode of enumerated embodiment 34, wherein the surface layer includes a metal oxygen compound, a metal silicide, a silicon compound, a silicate compound, or a metal sulfide. Enumerated embodiment 36. The anode according to any of enumerated embodiments 1 through 35, further including a supplemental layer disposed over the second lithium storage layer. Enumerated embodiment 37. The anode of enumerated embodiment 36, wherein the supplemental layer has a thickness of 100 nm or less and includes a metal oxide, a metal nitride, a metal oxynitride, a lithium phosphorous oxynitride (LIPON), lithium phosphate, lithium aluminum oxide, (Li,La)xTiyOz, LixSiyAl2O3, or a metalcone. Enumerated embodiment 38. A lithium-ion battery cell including: the anode according to any of enumerated embodiments 1 through 37; a cathode including a cathode active material layer in electrical contact with a cathode current collector; and a lithium-ion-containing electrolyte interposed between the anode and the cathode. Enumerated embodiment 39. The lithium-ion battery cell of enumerated embodiment 38, wherein the electrolyte includes a liquid electrolyte. Enumerated embodiment 40. The lithium-ion battery cell of enumerated embodiment 39, further including a separator disposed between the anode and a cathode.Enumerated embodiment 41. The lithium-ion battery cell according to any of enumerated embodiments 38 through 40, wherein the electrolyte includes a solid-state electrolyte (SSE). Enumerated embodiment 42. The lithium-ion battery cell of enumerated embodiment 41, wherein the SSE includes a solid polymer electrolyte. Enumerated embodiment 43. The lithium-ion battery cell of enumerated embodiment 42, wherein the solid polymer electrolyte includes a poly(ethylene oxide), a poly(acrylonitrile), a poly(methyl methacrylate), a poly(vinyl alcohol), a poly(trimethylene carbonate), a diester-based polymer, a PVdF-based polymer, a polycaprolactone, or any of their derivatives or copolymers. Enumerated embodiment 44. The lithium-ion battery cell of enumerated embodiment 41, wherein the SSE includes a solid inorganic electrolyte. Enumerated embodiment 45. The lithium-ion battery cell of enumerated embodiment 44, wherein the solid inorganic electrolyte includes a solid sulfide, b- alumina, a LISICON, a thio-LISICON, a NASICON, a perovskite, an antiperovskite, a garnet, or a complex hydride. Enumerated embodiment 46. The lithium-ion battery cell of enumerated embodiment 41, wherein the SSE is a hybrid SSE including both a solid polymer electrolyte and a solid inorganic electrolyte. Enumerated embodiment 47. The lithium-ion battery cell of enumerated embodiment 41, wherein the SSE includes i) a first SSE material in a first SSE layer disposed adjacent to the anode, and ii) a second SSE material in a second SSE layer interposed between the cathode and the first SSE layer, wherein the second SSE material has a chemical composition different from the first SSE material. Enumerated embodiment 48. The lithium-ion battery cell of enumerated embodiment 47, wherein the first SSE material includes a solid polymer electrolyte. Enumerated embodiment 49. The lithium-ion battery cell of enumerated embodiment 47 or 48, wherein the second SSE material includes a solid inorganic electrolyte.Enumerated embodiment 50. The lithium-ion battery cell of enumerated embodiment 49, wherein the second SSE material includes a solid sulfide electrolyte. Enumerated embodiment 51. The lithium-ion battery cell according to any of enumerated embodiments 41 through 50, wherein the cathode active material layer includes a solid electrolyte material. Enumerated embodiment 52. The lithium-ion battery cell of enumerated embodiment 51, wherein the solid electrolyte material of the cathode active material layer has a different chemical composition than the SSE interposed between the anode and the cathode. Enumerated embodiment 53. The lithium-ion battery cell according to any of enumerated embodiments 38 – 51, wherein the cathode active material layer includes a lithium metal compound, wherein the lithium metal compound including LiCoO2, LiFePO4, LiMnO2, LiNiO2, LiMn2O4, LiCoPO4, LiNixCoyMnzO2, LiNiXCoYAlZO2, LiFe2(SO4)3, or Li2FeSiO4. Enumerated embodiment 54. The lithium-ion battery cell according to any of enumerated embodiments 38 – 51, wherein the cathode active material layer includes sulfur, selenium, or both sulfur and selenium.

[0121] The specific details of particular examples may be combined in any suitablemanner without departing from the spirit and scope of examples of the invention. However, other examples of the invention may be directed to specific examples relating to each individual aspect, or specific combinations of these individual aspects.

[0122] The above description of example examples of the invention has been presentedfor 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.

[0123] In the preceding description, for the purposes of explanation, numerous detailshave been set forth in order to provide an understanding of various examples of the present technology. It will be apparent to one skilled in the art, however, that certain examples may be practiced without some of these details, or with additional details.

[0124] Having described several examples, it will be recognized by those of skill in theart that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuringthe present invention. Additionally, details of any specific example may not always be present in variations of that example or may be added to other examples.

[0125] Where a range of values is provided, it is understood that each interveningvalue, 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.

[0126] 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 within the scope of the appended claims.

[0127] All publications, patents, and patent applications cited herein are herebyincorporated by reference in their entirety for all purposes. None is admitted to be prior art.

Claims

We claim:

1. An anode for an energy storage device, the anode comprising: a current collector; a first lithium storage layer overlaying the current collector, the first lithium storage layer comprising an alloying lithium storage material; and a second lithium storage layer overlaying the first lithium storage layer, the second lithium storage layer comprising a non-alloying metal compound lithium storage material selected from the group consisting of a conversion-type material and an intercalation-type material.

2. The anode of claim 1, wherein the first lithium storage layer comprises at least 40 atomic % silicon, tin, germanium, or a combination thereof.

3. The anode of claim 1, wherein the first lithium storage layer is substantially free of high aspect ratio lithium storage nanostructures.

4. The anode of claim 1, wherein the first lithium storage layer is a continuous porous lithium storage layer.

5. The anode of claim 1, wherein the first lithium storage layer comprises a sub-stoichiometric nitride of silicon.

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

7. The anode of claim 1, wherein the first lithium storage layer comprises columns of silicon nanoparticle aggregates.

8. The anode of claim 1, wherein the first lithium storage layer is substantially free of carbon-based binders and conductive carbon.

9. The anode of claim 1, wherein the first lithium storage layer is a segmented first lithium storage layer.

10. The anode of claim 1, wherein the first lithium storage layer is deposited onto the current collector by a PVD or CVD process.

11. The anode of claim 10, wherein the first lithium storage layer is deposited onto the current collector by the CVD process, and the CVD process is a PECVD process.

12. The anode of claim 1, wherein the non-alloying metal compound lithium storage material comprises a metal oxide.

13. The anode of claim 12, wherein the non-alloying metal compound lithium storage material comprises a titanium oxide, a lithium titanium oxide (LTO), a niobium oxide, an aluminum niobium oxide, or a titanium niobium oxide (TNO).

14. The anode of claim 12, wherein the non-alloying metal compound lithium storage material comprises a nickel oxide, a copper oxide, a manganese oxide, a tungsten oxide, a vanadium oxide, a cobalt oxide, a chromium oxide, a zinc oxide, a tin oxide, a germanium oxide, or an antimony oxide.

15. The anode of claim 1, wherein the non-alloying metal compound lithium storage material comprises a transition metal sulfide, a tin sulfide, a transition metal phosphide, a transition metal nitride, a transition metal fluoride, a transition metal hydroxide, a transition metal selenide, a titanium carbide, or a transition metal oxalate.

16. The anode of claim 1, wherein the second lithium storage layer is deposited by a PVD or CVD process.

17. The anode of claim 1, wherein the second lithium storage layer is deposited from a slurry comprising the non-alloying metal compound lithium storage material.

18. The anode of claim 1, wherein the first lithium storage layer has a higher areal storage capacity than the second lithium storage layer.

19. The anode of claim 1, wherein the first lithium storage layer has a greater thickness than the second lithium storage layer.

20. The anode of claim 1, wherein the first and second lithium storage layers are segmented lithium storage layers.

21. The anode according of claim 1, wherein the first lithium storage layer is a segmented lithium storage layer comprising segments, and the second lithium storage layer is provided over the segments and within spaces between the segments.

22. The anode of claim 21, wherein the second lithium storage layer is in contact with the current collector.

23. The anode according to any of claims 1 – 22, wherein the current collector is characterized by a surface roughness Ra≥ 250 nm.

24. The anode according to any of claims 1 – 23, wherein the current collector comprises an electrically conductive layer comprising a metal or a conductive carbon.

25. The anode of claim 24, wherein the electrically conductive layer comprises copper, nickel, titanium, stainless steel, or a combination thereof.

26. A lithium-ion battery cell comprising: the anode of claim 1; a cathode comprising a cathode active material layer in electrical contact with a cathode current collector; and a lithium-ion-containing electrolyte interposed between the anode and the cathode.

27. The lithium-ion battery cell of claim 26, wherein the electrolyte comprises a liquid electrolyte.

28. The lithium-ion battery cell of claim 27, further comprising a separator disposed between the anode and a cathode.

29. The lithium-ion battery cell of claim 26, wherein the electrolyte comprises a solid-state electrolyte (SSE).

30. The lithium-ion battery cell of claim 29, wherein the SSE comprises a solid polymer electrolyte.

31. The lithium-ion battery cell of claim 30, wherein the solid polymer electrolyte comprises a poly(ethylene oxide), a poly(acrylonitrile), a poly(methyl methacrylate), a poly(vinyl alcohol), a poly(trimethylene carbonate), a diester-based polymer, a PVdF-based polymer, a polycaprolactone, or any of their derivatives or copolymers.

32. The lithium-ion battery cell of claim 29, wherein the SSE comprises a solid inorganic electrolyte.

33. The lithium-ion battery cell of claim 32, wherein the solid inorganic electrolyte comprises a solid sulfide, b-alumina, a LISICON, a thio-LISICON, a NASICON, a perovskite, an antiperovskite, a garnet, or a complex hydride.

34. The lithium-ion battery cell of claim 29, wherein the SSE is a hybrid SSE comprising both a solid polymer electrolyte and a solid inorganic electrolyte.

35. The lithium-ion battery cell of claim 29, wherein the SSE comprises i) a first SSE material in a first SSE layer disposed adjacent to the anode, and ii) a second SSE material in a second SSE layer interposed between the cathode and the first SSE layer, wherein the second SSE material has a chemical composition different from the first SSE material.

36. The lithium-ion battery cell of claim 35, wherein the first SSE material comprises a solid polymer electrolyte.

37. The lithium-ion battery cell of claim 35, wherein the second SSE material comprises a solid inorganic electrolyte.

38. The lithium-ion battery cell of claim 37, wherein the second SSE material comprises a solid sulfide electrolyte.

39. The lithium-ion battery cell of claim 29, wherein the cathode active material layer comprises a solid electrolyte material.

40. The lithium-ion battery cell of claim 39, wherein the solid electrolyte material of the cathode active material layer has a different chemical composition than the SSE interposed between the anode and the cathode.

41. The lithium-ion battery cell of claim 26, wherein the cathode active material layer comprises a lithium metal compound, wherein the lithium metal compound comprising LiCoO2, LiFePO4, LiMnO2, LiNiO2, LiMn2O4, LiCoPO4, LiNixCoyMnzO2, LiNiXCoYAlZO2, LiFe2(SO4)3, or Li2FeSiO4.

42. The lithium-ion battery cell of claim 26, wherein the cathode active material layer includes sulfur, selenium, or both sulfur and selenium.

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