Anode for lithium-based energy storage devices

Abstract

An anode for an energy storage device, which includes a current collector having a conductive layer and a surface layer disposed above the conductive layer. The surface layer may include a first surface sub-layer adjacent to the conductive layer and a second surface sub-layer disposed above the first surface sub-layer. The first surface sub-layer may include zinc. The second surface sub-layer may include a metal-oxide compound, wherein the metal-oxide compound includes a transition metal other than zinc. The current collector may be characterized by a surface roughness Ra≥250 nm. The anode further includes a continuous porous lithium storage layer covering the surface layer. The continuous porous lithium storage layer may have an average thickness of at least 7 μm, may include at least 40 atomic % of silicon, germanium, or a combination thereof, and may be substantially free of a carbon-based binder.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 045,570, filed Jun. 29, 2020, and U.S. Provisional Application No. 63 / 179,971, filed Apr. 26, 2021, each of which is incorporated herein by reference in its entirety. Technical field

[0003] This disclosure relates to lithium - ion batteries and related energy storage devices. Background art

[0004] Silicon has been proposed for use in lithium - ion batteries to replace traditional carbon - based anodes, whose storage capacity is limited to ∼370 mAh / g. Silicon readily forms an alloy with lithium and has a much higher theoretical storage capacity (∼3600 to 4200 mAh / g at room temperature) compared to carbon anodes. However, the insertion and extraction of lithium into and from the silicon matrix results in significant volume expansion (>300%) and contraction. This can cause the silicon to rapidly pulverize into small particles and disconnect electrically from the current collector.

[0005] The industry has recently turned its attention to nano - or micro - structured silicon, i.e., silicon in the form of spaced - apart nano - or micro - wires, tubes, columns, particles, etc. to reduce the pulverization problem. The theory is that making the structures nano - sized avoids crack propagation and spacing them apart allows more room for volume expansion, enabling the silicon to absorb lithium with reduced stress and improved stability compared to, for example, a macroscopic bulk silicon layer.

[0006] Despite research into various methods, silicon - based batteries have not had a significant market impact due to the problems not being solved. Summary of the invention

[0007] There is still a need for anodes for lithium - based energy storage devices such as, for example, lithium - ion batteries, which are easy to manufacture, robust to handle, suitable for high charge capacities for fast charging, e.g., at least 1C, and resistant to dimensional changes.

[0008] According to an embodiment of the present disclosure, an anode for an energy storage device includes a current collector having a conductive layer and a surface layer disposed above the conductive layer. The surface layer may include a first surface sublayer adjacent to the conductive layer and a second surface sublayer disposed above the first surface sublayer. The first surface sublayer may include zinc. The second surface sublayer may include a metal-oxide compound, wherein the metal-oxide compound includes a transition metal other than zinc. The current collector may be characterized by a surface roughness Ra≥250 nm. The anode further includes a continuous porous lithium storage layer covering the surface layer. The continuous porous lithium storage layer may have an average thickness of at least 7 μm, may include at least 40 atomic % of silicon, germanium, or a combination thereof, and may be substantially free of a carbon-based binder.

[0009] The present disclosure provides an anode for an energy storage device, which may have more than one of the following advantages over conventional anodes: improved stability at an aggressive ≥1C charging rate; higher overall areal charge capacity; higher charge capacity relative to each gram of lithium storage material (such as silicon); improved physical durability; simplified manufacturing process; more reproducible manufacturing process; or reduced dimensional change during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view of a non-limiting example of an anode according to some embodiments.

[0011] FIG. 2 is a cross-sectional view of an anode of the prior art.

[0012] Figure 3 is a cross-sectional view of a non-limiting example of an anode according to some embodiments.

[0013] Figure 4 is a cross-sectional view of a non-limiting example of an anode according to some embodiments.

[0014] Figure 5A is a cross-sectional view of a non-limiting example of a current collector having a first type of nanowire according to some embodiments.

[0015] Figure 5B is a cross-sectional view of a non-limiting example of a current collector having a second type of nanowire according to some embodiments.

[0016] Figure 5C is a SEM cross-sectional view of a non-limiting example of a current collector having a wide roughness feature according to some embodiments.

[0017] Figure 6 is a cross-sectional view of a non-limiting example of an anode according to some embodiments.

[0018] Figure 7 It is a cross-sectional SEM of the anode E-1A of the embodiment.

[0019] Figure 8A It is a top-down SEM image of the current collector used in the embodiment E-14B.

[0020] Figure 8B It is a cross-sectional SEM of the current collector used in the embodiment E-14B.

[0021] Figure 8C It is a cross-sectional SEM of the anode of the embodiment E-14B.

[0022] Figure 9 It is a cross-sectional SEM of the current collector used in the embodiment E-16B.

[0023] Figure 10A It is a 45-degree SEM perspective view of the current collector used in the embodiment E-14B.

[0024] Figure 10B It is a cross-sectional SEM of the current collector used in the embodiment E-14B.

[0025] Figure 10C It is a cross-sectional SEM of the anode of the embodiment E-14B.

[0026] Figure 11 It is a 45-degree SEM perspective view of the current collector used in the embodiment E-3B. Detailed implementation mode

[0027] It should be understood that the drawings are for illustrating the concepts of the present disclosure and may not be to scale. Terms such as "cover", "above", etc. do not necessarily mean direct contact, unless such direct contact is presented or explicitly required for the function. However, embodiments of "cover" or "above" may include layers in direct contact.

[0028] Figure 1Cross-sectional view of an anode according to some embodiments of the present disclosure. Anode 100 includes a current collector 101 and a continuous porous lithium storage layer 107 covering the current collector. Current collector 101 includes a surface layer 105 disposed above a conductive layer 103, such as a conductive metal layer. Although for convenience the surface of the current collector is shown as flat in this figure, the current collector can have a rough surface, as described below. Continuous porous lithium storage layer 107 is disposed above surface layer 105. In some embodiments, the top of continuous porous lithium storage layer 107 corresponds to the top surface 108 of anode 100. In some embodiments, continuous porous lithium storage layer 107 is in physical contact with surface layer 105. In some embodiments, the continuous porous lithium storage layer includes a material capable of forming an electrochemically reversible alloy with lithium. In some embodiments, the continuous porous lithium storage layer includes silicon, germanium, tin, or an alloy thereof. In some embodiments, the continuous porous lithium storage layer includes at least 40 atomic % of silicon, germanium, or a combination thereof. In some embodiments, the continuous porous lithium storage layer is provided by a chemical vapor deposition (CVD) method, including but not limited to hot wire CVD or plasma enhanced chemical vapor deposition (PECVD).

[0029] In the present disclosure, the continuous porous lithium storage layer is substantially free of nanostructures with high aspect ratios, such as in the form of spaced-apart wires, columns, tubes, etc., or in the form of regular linear vertical channels extending through the lithium storage layer. FIG. 2 shows a cross-sectional view of a prior art anode 170, which includes some non-limiting examples of lithium storage nanostructures, such as nanowires 190, nanocolumns 192, nanotubes 194, and nanochannels 196 disposed above a current collector 180. Unless otherwise specified, the term "lithium storage nanostructure" herein generally refers to a lithium storage active material structure (e.g., a structure of silicon, germanium, or an alloy thereof) having at least one cross-sectional dimension less than about 2000 nm, rather than a dimension approximately orthogonal to an underlying substrate (e.g., layer thickness) and not including dimensions caused by random pores and channels. Similarly, the terms "nanowire," "nanocolumn," and "nanotube" refer to a wire, column, and tube, respectively, in which at least a portion has a diameter less than 2000 nm. A "high aspect ratio" nanostructure has an aspect ratio greater than 4:1, where the aspect ratio is generally the height or length of the feature (which can 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 can generally be measured orthogonally to the feature axis). In some embodiments, when the anode has fewer than 10 lithium storage nanostructures per 1600 square microns on average (e.g., an average, median, or mode), where the number of lithium storage nanostructures is the sum of the number of nanowires, nanocolumns, and nanotubes in the same unit area, the continuous porous lithium storage layer is considered to be "substantially free" of lithium storage nanostructures having an aspect ratio greater than 4:1. Alternatively, there is an average of fewer than 1 such lithium storage nanostructure per 1600 square microns. As described below, the current collector may have a high surface roughness or include nanostructures, but these features are separate from the continuous porous lithium storage layer and are different from the lithium storage nanostructures.

[0030] In some embodiments, deposition conditions are selected in combination with the current collector such that the continuous porous lithium storage layer is relatively smooth, providing an anode having a diffuse reflectance or total reflectance of at least 10%, or at least 20% (measured on the side of the continuous porous lithium storage layer) at 550 nm. In some embodiments, an anode having such a diffuse reflectance or total reflectance may be less prone to damage due to physical handling. In some embodiments, an anode substantially free of lithium storage nanostructures may have a lower reflectance and may be more prone to damage due to physical handling.

[0031] The anodes of the present disclosure can optionally be double-sided. For example, Figure 3Cross-sectional view of a dual-sided anode according to some embodiments. The current collector 301 may include a conductive layer 303 and surface layers (305a, 305b) disposed on both sides of the conductive layer 303. Continuous porous lithium storage layers (307a, 307b) are disposed on both sides to form the anode 300. The surface layers 305a and 305b may be the same or different in terms of composition, thickness, roughness, or some other properties. Similarly, the continuous porous lithium storage layers 307a and 307b may be the same or different in terms of composition, thickness, porosity, or some other properties.

[0032] Current collector

[0033] In some embodiments, the current collector or the conductive layer may be characterized by the tensile strength Rm or the yield strength Re. In some cases, the tensile strength and yield strength properties of the current collector mainly depend on the conductive layer, and in some embodiments, the conductive layer may be thicker than the surface layer. If the tensile strength is too high or too low, it may be difficult to operate during manufacturing, for example, in a roll-to-roll process. During the electrochemical cycling of the anode, if the tensile strength is too low, deformation of the anode may occur, or if the tensile strength is too high, the adhesion of the continuous porous lithium storage layer may be jeopardized.

[0034] Anode deformation is not necessarily a problem for all products, and such deformation may sometimes occur only at higher capacities, i.e., higher loadings of the lithium storage layer material. For such products, the current collector or the conductive layer may be characterized by a tensile strength Rm in the range of 100–150 MPa, optionally 150–200 MPa, optionally 200–250 MPa, optionally 250–300 MPa, optionally 300–350 MPa, optionally 350–400 MPa, optionally 400–500 MPa, optionally 500–600 MPa, optionally 600–700 MPa, optionally 700–800 MPa, optionally 800–900 MPa, optionally 900–1000 MPa, optionally 1000–1200 MPa, optionally 1200–1500 MPa, or any combination of its ranges.

[0035] In some embodiments, significant anode deformation should be avoided, but low battery capacity may be unacceptable. For example, when the anode includes amorphous silicon of more than 7 μm and / or the electrochemical cycling capacity is 1.5 mAh / cm 2Above, the characteristics of the current collector or conductive layer may lie in that the tensile strength Rm is greater than 600 MPa. In such an embodiment, the tensile strength may be in the range of 601–650 MPa, optionally 650–700 MPa, optionally 700–750 MPa, optionally 750–800 MPa, optionally 800–850 MPa, optionally 850–900 MPa, optionally 900–950 MPa, optionally 950–1000 MPa, optionally 1000–1200 MPa, optionally 1200–1500 MPa, or any combination of these ranges. In some embodiments, the current collector or conductive layer may have a tensile strength greater than 1500 MPa. In some embodiments, the current collector or conductive layer is in the form of a foil, with a tensile strength greater than 600 MPa and an average thickness in the range of 4–8 μm, optionally 8–10 μm, optionally 10–15 μm, optionally 10–15 μm, optionally 15–20 μm, optionally 20–25 μm, optionally 25–30 μm, optionally 30–40 μm, optionally 40–50 μm, or any combination of these ranges.

[0036] In some embodiments, the conductive layer may have at least 10 3 S / m, or optionally at least 10 6 S / m, or optionally at least 10 7 S / m of conductivity and may include inorganic or organic conductive materials or a combination thereof. For anodes with low capacity and / or when there is no concern about anode deformation during use, a variety of conductive materials can be used as the conductive layer.

[0037] In some embodiments, the conductive layer includes a metallic material, such as titanium (and its alloys), nickel (and its alloys), copper (and its alloys), or stainless steel. In some embodiments, the conductive layer includes conductive carbon, such as carbon black, carbon nanotubes, graphene, graphene oxide, reduced graphene oxide, and graphite. In some embodiments, the conductive layer may be in the form of a foil, mesh, or sheet of a conductive material. Here, "mesh" includes any conductive structure having openings found, for example, in interwoven wires, foam structures, foils with an array of holes, etc. In some embodiments, the conductive layer may include multiple layers of different conductive materials. The conductive layer may be in the form of a layer deposited on an insulating substrate (e.g., a polymer sheet or ceramic substrate coated with a conductive material, which includes but is not limited to nickel or copper, optionally on both sides). In some embodiments, the conductive layer includes a mesh or sheet of conductive carbon, which includes but is not limited to those formed by bundles of carbon nanotubes or nanofibers.

[0038] When higher tensile strength is desired, the conductive layer can include nickel (and certain alloys), or certain copper alloys such as brass (an alloy mainly of copper and zinc), bronze (an alloy mainly of copper and tin), CuMgAgP (an alloy mainly of copper, magnesium, silver and phosphorus), CuFe2P (an alloy mainly of copper, iron and phosphorus), CuNi3Si (an alloy mainly of copper, nickel and silicon). The nomenclature of metal alloys is not the stoichiometric molecular formula used in chemistry, but the nomenclature used by those of ordinary skill in the art of alloys. For example, CuNi3Si does not mean that for every copper atom there are three nickel atoms and one silicon atom. In some embodiments, these nickel-based or copper-based higher tensile conductive layers can include roll-formed nickel or copper alloy foils.

[0039] Optionally, a network or sheet of conductive carbon, including but not limited to a network or sheet formed of bundled carbon nanotubes or nanofibers, can provide a conductive layer with higher tensile strength. In some embodiments, a conductive metal interlayer can be interposed between the conductive carbon and the surface layer.

[0040] In some embodiments, any of the above conductive layers (low or high tensile strength) can serve as the primary electrically conductive layer, and further includes a conductive interlayer, for example, a metal interlayer, which is disposed between the primary conductive layer and the surface layer. Figure 4 Is a cross-sectional view of such an anode according to some embodiments, in this case a double-sided anode. The current collector 401 can include a conductive layer 403 and surface layers (405a, 405b) disposed on both sides of the conductive layer 403. Continuous porous lithium storage layers (407a, 407b) can be disposed on both sides to form the anode 400. The conductive layer 403 includes a primary conductive layer 402 with metal interlayers (404a, 404b) disposed on both sides. The metal interlayers 404a and 404b can be the same or different in terms of composition, thickness, roughness or some other property. Similarly, the surface layers 405a and 405b can be the same or different in terms of composition, thickness, roughness or some other property. Similarly, the continuous porous lithium storage layers 407a and 407b can be the same or different in terms of composition, thickness, porosity or some other property.

[0041] The metal interlayer can be applied by, for example, sputtering, vapor deposition, electrolytic electroplating or electroless plating or any convenient method. The average thickness of the metal interlayer is typically less than 50% of the average thickness of the total conductive layer, i.e., the combined thickness of the primary conductive layer and the metal interlayer. In some embodiments, compared with the primary conductive layer, the surface layer can be formed more uniformly over the metal interlayer or adhere better to the metal interlayer.

[0042] In some embodiments, the current collector can be characterized as having a surface roughness. In some embodiments, the top surface 108 of the lithium storage layer 107 can have a lower surface roughness than the surface roughness of the current collector 101. Here, the roughness average (Ra), RMS roughness (Rq), maximum profile peak height roughness (Rp), average maximum height of the profile (Rz), or peak density (Pc) can be used for surface roughness comparison and measurement. In some embodiments, the current collector can be characterized as having both a surface roughness Rz≥2.5 μm and a surface roughness Ra≥0.25 μm. In some embodiments, Rz is in the range of 2.5–3.0 μm, optionally 3.0–3.5 μm, optionally 3.5–4.0 μm, optionally 4.0–4.5 μm, optionally 4.5–5.0 μm, optionally 5.0–5.5 μm, optionally 5.5–6.0 μm, optionally 6.0–6.5 μm, optionally 6.5–7.0 μm, optionally 7.0–8.0 μm, optionally 8.0–9.0 μm, optionally 9.0–10 μm, 10–12 μm, 12–14 μm, or any combination of its ranges. In some embodiments, Ra is in the range of 0.25–0.30 μm, optionally 0.30–0.35 μm, optionally 0.35–0.40 μm, optionally 0.40–0.45 μm, optionally 0.45–0.50 μm, optionally 0.50–0.55 μm, optionally 0.55–0.60 μm, optionally 0.60–0.65 μm, optionally 0.65–0.70 μm, optionally 0.70–0.80 μm, optionally 0.80–0.90 μm, optionally 0.90–1.0 μm, optionally 1.0–1.2 μm, optionally 1.2–1.4 μm, or any combination of its ranges.

[0043] In some embodiments, some or most of the surface roughness of the current collector can be imparted by the conductive layer and / or the metal interlayer. Alternatively, some or most of the surface roughness of the current collector can be imparted by the surface layer. Alternatively, some combination of the conductive layer, the metal interlayer, and the surface layer can contribute significantly to the surface roughness.

[0044] In some embodiments, the conductive layer, such as the metal interlayer, can include electrodeposited copper roughening features to increase the surface roughness. For example, a relatively smooth copper foil can be provided to a first acidic copper plating solution having 50 to 250 g / L sulfuric acid and less than 10 g / L copper provided in the form of copper sulfate. Cathodic polarization of the copper foil can be carried out at room temperature and a current density of about 0.05 to 0.3 A / cm 2The current density is used to deposit copper features for several seconds to several minutes. In some embodiments, a copper foil can then be provided to a second acidic copper plating solution having 50 to 200 g / L sulfuric acid and greater than 50 g / L copper provided in the form of copper sulfate. Optionally, the second acidic copper bath can be heated to a temperature of about 30 °C to 50 °C. A thin layer of copper can be electroplated over the copper features to fix the particles to the copper foil by cathodic polarization and applying a current density of about 0.05 to 0.2 A / cm 2 for several seconds to several minutes.

[0045] Optionally, or in combination with electroplating copper roughening features, the conductive layer can be subjected to other electrochemical, chemical, or physical treatments to impart the desired surface roughness before forming the surface layer.

[0046] In some embodiments, a metal foil, including but not limited to rolled copper foil, can first be heated in an oven in air (e.g., between 100 °C and 200 °C) for a period of time (e.g., 10 minutes to 24 hours) to remove any volatile materials on its surface and cause some surface oxidation. In some embodiments, the heat-treated foil can then be subjected to additional chemical treatment, e.g., immersion in a chemical etchant such as an acid or a hydrogen peroxide / HCl solution, optionally followed by rinsing with deionized water. The chemical etchant removes the oxidized metal. This treatment can increase the surface roughness. In some embodiments, instead of heating, treatment is carried out with a chemical etchant including an oxidant. In some embodiments, the oxidant can be dissolved oxygen, hydrogen peroxide, or some other suitable oxidant. This chemical etchant can further include an organic acid such as methanesulfonic acid or an inorganic acid such as hydrochloric acid or sulfuric acid. Optionally, rinsing with deionized water can be carried out after the chemical etchant. This treatment described in this paragraph can be referred to herein as a "chemical roughening" treatment. In the case of a copper foil, any chemical roughening treatment carried out in an ambient environment is expected to form at least a monolayer of copper oxide after rinsing and drying. This copper oxide (or other metal oxide) surface can be suitably subjected to further treatment, e.g., with a silicon compound reagent.

[0047] In some embodiments, the electroplated copper roughening features can be characterized as nano-column features. Figure 5AA cross-sectional view showing a non-limiting example of an electroplated copper roughening feature according to some embodiments is presented. In some cases, the current collector 501 may include a plurality of nanocolumn features 520 (electroplated copper roughening features) disposed above the conductive layer 503. The nanocolumn features 520 differ from the nanocolumns 192 of FIG. 2 at least in terms of their composition, their layers, their dimensions, the process used to form the nanocolumns, their surface density, and / or their orientation. The nanocolumn features 520 may include a metal-containing nanocolumn core 522 (e.g., a copper-containing core) and a surface layer 505 that is at least partially disposed above the nanocolumn core and optionally above the conductive layer in the gap regions between the nanocolumn features. The nanocolumn features may each be characterized by a height H, a bottom width B, and a maximum width W. The bottom width B may be the minimum width from one side to the other at the bottom end or base of the nanocolumn feature. The maximum width W may be measured in the widest cross-section orthogonal to the nanocolumn feature axis. The height H from the bottom to the end of the nanocolumn feature may be measured along the nanocolumn feature axis. The nanocolumn axis is the longitudinal axis of the nanocolumn feature. In some cases, the nanocolumn feature axis may pass through the centroid of the nanocolumn feature.

[0048] In some embodiments, the nanocolumn features may be characterized as first-type and second-type nanocolumns. The second type may not be as desirable as the first type. In some cases, the first-type nanocolumns may be characterized in that: H is in the range of 0.4 μm to 3.0 μm; B is in the range of 0.2 μm to 1.0 μm; the W / B ratio is in the range of 1 to 1.5; the H / B ratio (aspect ratio) is in the range of 0.8 to 4.0; and the angle of the longitudinal axis of the nanocolumn feature relative to the plane of the conductive layer is in the range of 60° to 90°. For example, Figure 5A all of the nanocolumn features in Figure 8A and 8B may be first-type nanocolumns. SEM cross-sectional examples can be found in Figure 5A as shown.

[0049] In some cases, the second type of nanocolumns may be characterized in that H is at least 1.0 μm and the W / B ratio is greater than 1.5. That is, the second type of nanocolumns tend to widen away from their bottoms. SEM cross-sectional examples can be found in Figure 9 discussed later. Figure 5B is a cross-sectional view of a non-limiting example of the second type of nanocolumns. For clarity, the nanocolumn core and the surface layer are not defined separately. The second type of nanocolumns may have a significantly wide upper part (sometimes referred to herein as "wide-top roughening features"), such as nanocolumn feature 524. Alternatively, the second type of nanocolumns may include a branched or dendritic structure such as nanocolumn feature 526. Although both the "trunk" and the "branches" are similar in width, this feature is generally significantly wider towards the top, as shown by the effective cross-sectional profile 526'. The effective cross-sectional profile 526' is the shape formed by drawing a line between the outermost points of the continuous branches or trunks of the nanocolumn feature. Such a branched structure may have the same effect as a solid nanocolumn feature such as 524. In some embodiments, in an optical or SEM analysis, the average 20-μm-long cross-section of the current collector may include fewer second-type nanocolumns than the first type of nanocolumns. In some embodiments, in an optical or SEM analysis, the average 20-μm-long cross-section of the current collector may include fewer than four (4), optionally fewer than 3, fewer than 2, or fewer than 1 second-type nanocolumns.

[0050] In some embodiments, with respect to Ra or Rz, the surface roughness may be relatively large, but the feature itself may be a wide roughness feature, e.g., as bumps and hills with an average spacing of at least about 2 μm. Figure 5CSEM cross-sectional view of a portion of a current collector having a wide roughness feature. The current collector 501C includes a conductive layer 503C (the surface layer is not easily distinguishable in the SEM). The measured surface roughness Ra of this current collector is 508 nm. The wide roughness feature can be characterized by the peak height P and the valley-to-valley spacing V. The ratio P / V represents the aspect ratio of the wide roughness feature. In some embodiments, on average, V is greater than at least 3 μm, or alternatively at least 4 μm, and P / V is less than 0.8, alternatively less than 0.6. In some embodiments, for V and P / V, on average, V is in the range of 3–4 μm, alternatively 4–5 μm, alternatively 5–6 μm, alternatively 6–8 μm, alternatively 8–10 μm, alternatively 10–12 μm, alternatively 12–15 μm, and P / V is in the range of 0.2–0.3, alternatively 0.3–0.4, alternatively 0.4–0.5, alternatively 0.5–0.6, alternatively 0.6–0.7, alternatively 0.7–0.8, or any combination of its ranges. In some embodiments, V is the same as the peak-to-peak spacing. Refer later to Figure 8A and 8B discuss the same current collector.

[0051] In some embodiments, the chemically roughened current collector surface may be pitted, cratered, or corroded. Figure 11Non-limiting examples are shown. Some regions corresponding approximately to the original surface can still be seen, for example in the A-type regions - one can still recognize the lines from the original roll-formed surface. Most of the surface has been etched, resulting in a very rough, random, pitted topology, much rougher than the original surface. In some embodiments, at least 50% of the surface of the conductive layer has been etched to a depth of at least 0.5 μm, optionally at least 1.0 μm from the original surface, where the surface roughness Ra is at least 400 nm, optionally at least 500 nm, optionally at least 600 nm, optionally at least 700 nm. Many dimples / pits are visible. In some embodiments, when examined by SEM analysis, the average 100 square micron area of the chemically roughened current collector can include at least 1 recognizable dimple, optionally at least 2, 3, or 4. In some embodiments, a "pit" can be a feature characterized by width and depth, where the depth-to-width ratio is at least 0.25, optionally at least 0.5. The pit can be a recess defined by the current collector. The top of the pit can be the top surface of the current collector. In some embodiments, the pit can be at least 2 μm wide. In some embodiments, the pits can occupy 2% to 5%, optionally 5% to 10%, optionally 10% to 20%, optionally 20% to 30%, optionally 30% to 40%, optionally 40% to 50% of the surface area of the current collector. In some embodiments, some of the etched regions or dimple regions can have a micro-roughened structure formed by the coalescence of secondary smaller dimples or pits. The average width or diameter of such secondary dimples can be less than about 2 μm, optionally less than about 1 μm. In some embodiments, the secondary dimples can occupy 5% to 10%, optionally 5% to 10%, optionally 10% to 20%, optionally 20% to 30%, optionally 30% to 40%, optionally 40% to 50%, optionally 50% to 60%, optionally 60% to 70%, optionally 70% to 90% of the surface area of the current collector.

[0052] Surface layer

[0053] In some embodiments, the surface layer can include zinc, metal-oxide compounds, or silicon compounds, or combinations thereof. In some embodiments, in addition to zinc or silicon compounds or both zinc and silicon compounds, the surface layer further includes at least metal-oxide compounds. The surface layer can optionally include additional materials. In some embodiments, the surface layer can include more than two sub-layers. Each of the more than two sub-layers can have a composition different from that of an adjacent sub-layer. The composition within each sub-layer can be homogeneous or heterogeneous. In some embodiments, at least one sub-layer includes zinc, metal-oxide compounds, or silicon compounds. In some embodiments, at least one sub-layer includes metal-oxide compounds and at least one other sub-layer includes zinc or silicon compounds. Figure 6Non-limiting examples are shown in which a surface layer 605 having up to four surface sub-layers is shown. The surface sub-layer 605-1 covers the conductive layer 603. The surface sub-layer 605-2 covers the surface sub-layer 605-1, the surface sub-layer 605-3 covers the surface sub-layer 605-2, and the surface sub-layer 605-4 covers the surface sub-layer 605-3. A continuous porous lithium storage layer 607 is disposed above the topmost surface sub-layer, i.e., the sub-layer farthest from the conductive layer 603, in Figure 6 In Figure 6 , if all four sub-layers are present, this sub-layer can be sub-layer 605-4.

[0054] In some embodiments, the surface layer or sub-layer can include zinc (“surface material A”). In some embodiments, the surface layer or sub-layer can include a metal-oxide (“surface material B”). In some embodiments, the surface layer or sub-layer can include a silicon compound that includes siloxane, silane (i.e., a silane-containing compound), silazane, or a reaction product or derivative thereof from siloxane, silane (i.e., a silane-containing compound), silazane, or a reaction product thereof (“surface material C”). Here, “silicon compound” does not include simple elemental silicon, such as amorphous silicon. In some embodiments, the sub-layer can include a metal oxide or a metal chalcogenide (“surface material D”). These materials will be described in more detail below. Using Figure 6 to assist in the illustration, Table 1 provides some non-limiting examples of surface layers where the surface materials are listed as A, B, C, and / or D, and where the sub-layers. In some cases, “B&C” refers to a mixture of both in a single surface sub-layer. In embodiments where more B or D is provided in sub-layer 605-2 compared to A in sub-layer 605-1, the metal of B or D is not zinc.

[0055] Table 1

[0056]

[0057] Zinc (surface material A)

[0058] In some embodiments, the surface layer or sub-layer includes metallic zinc or a zinc alloy, which can be deposited, for example, by electrolytic electroplating, electroless plating, physical vapor deposition, chemical vapor deposition, or sputtering. Representative electrolytic electroplating solutions include those based on zinc pyrophosphate, zinc chloride, zinc cyanide, or zinc sulfate electroplating. For example, a zinc pyrophosphate electroplating solution with a zinc concentration of 5 g / l to 30 g / l, a potassium pyrophosphate concentration of 50 g / l to 500 g / l, and a pH of 9 to pH 12 can be used. Electroplating can be carried out at a solution temperature of 20 °C to 50 °C, by applying a current density of 0.003 A / cm 2 to 0.10 A / cm 2The cathodic polarization of the conductive layer is carried out for several seconds to several minutes at a current density. In some embodiments, the galvanizing solution may further include a manganese salt, a stannous salt, or a nickel salt to form a zinc-manganese alloy, a zinc-tin alloy, or a zinc-nickel alloy. Here, the zinc alloy includes a zinc-containing layer in which less than 98 atomic% of all metal atoms are zinc. In contrast, the non-alloy zinc includes a zinc-containing layer in which at least 98 atomic% is zinc. In some embodiments, the zinc-nickel alloy may include 3–5 atomic% nickel, optionally 5–10 atomic% nickel, optionally 10–15 atomic% nickel, optionally 15–20 atomic% nickel, optionally 20–30 atomic% nickel, optionally 30–45 atomic% nickel. Many other electroplating compositions and conditions are available and can be used alternatively.

[0059] In some embodiments, the amount of zinc in the surface layer or sublayer can be at least 1 mg / m 2 , optionally at least 2 mg / m 2 , optionally at least 5 mg / m 2 . In some embodiments, the amount of zinc is less than 1000 mg / m 2 . In some embodiments, the amount of zinc can be in the range of 1–2 mg / m 2 , optionally 2–5 mg / m 2 , optionally 5–10 mg / m 2 , optionally 10–20 mg / m 2 , optionally 20–50 mg / m 2 , optionally 50–75 mg / m 2 , optionally 75–100 mg / m 2 , optionally 100–250 mg / m 2 , optionally 250–500 mg / m 2 , optionally 500–1000 mg / m 2 , optionally 1000–2000 mg / m 2 , optionally 2000–3000 mg / m 2 , optionally 3000–4000 mg / m 2 , optionally 4000–5000 mg / m 2 of the range, or any combination of its ranges. In some embodiments, the surface layer or surface sublayer including a zinc-nickel alloy may include at least 500 mg / m 2 of zinc. In some embodiments, the surface layer or surface sublayer including non-alloy zinc may be less than 500 mg / m 2In some embodiments, the surface layer or sublayer having a zinc-containing material may be at least 0.2 nm thick, alternatively at least 0.5 nm thick, alternatively at least 1 nm thick, or at least 2 nm thick. In some embodiments, the surface layer or sublayer having a zinc-containing material has a thickness in the range of 0.2–0.5 nm, alternatively 0.5–1.0 nm, alternatively 1.0–2.0 nm, alternatively 2.0–5.0 nm, alternatively 5.0–10 nm, alternatively 10–20 nm, alternatively 20–50 nm, alternatively 50–100 nm, alternatively 100–200 nm, alternatively 200–300 nm, alternatively 300–400 nm, alternatively 400–500 nm, 500–700 nm, or any combination of ranges thereof.

[0060] Metal-oxygen compound (surface material B)

[0061] In some embodiments, the surface layer or surface sublayer includes a metal-oxygen compound comprising a transition metal. Unless otherwise specified, the term "transition metal" used anywhere in this application includes any element in Groups 3 to 12 of the periodic table, including lanthanides and actinides. The metal-oxygen compound may include a transition metal oxide, a transition metal hydroxide, a transition metal oxoate, or a mixture thereof. Note that metal oxoates can be considered as a subset of metal oxides, wherein the metal oxide is essentially anionic and is combined with a cation, which can optionally be an alkali metal, an alkaline earth metal, or a transition metal (the same or different from the transition metal of the metal oxoate). In some embodiments, the transition metal of the metal-oxygen compound includes titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium, or niobium. In some embodiments, the metal-oxygen compound may include or be derived from a transition metal oxoate, including but not limited to chromate, tungstate, or molybdate. The metal-oxygen compound may be coated by solution, electrolytic plating, or chemical plating (which may include "immersion plating"). In some embodiments, such electrolytic plating or chemical plating may use a solution comprising a transition metal oxoate. In some cases, the nature of the deposited coating may include a mixture of transition metal oxides, hydroxides, and / or oxometalates.

[0062] A non-limiting representative electrolytic chromate solution may have a chromic acid or potassium chromate concentration of 2 g / l to 7 g / l and a pH of 10 to 12. The solution may optionally be warmed to a temperature of 30°C to 40°C and a current of 0.02 to 8 A / cm 2 A cathodic current density of 1000 nm is applied to the conductive layer, typically for a few seconds, to deposit a chromium-containing metal-oxygen compound. In some embodiments, this surface layer or surface sublayer may be referred to as a chromate treatment layer. The deposited chromium-containing metal-oxygen compound may include one or more of chromium oxide, chromium hydroxide, or chromate. At least a portion of the chromium may be in the form of chromium (III).

[0063] In some embodiments, the amount of chromium in the surface layer or sub-layer can be at least 0.5 mg / m 2 , optionally at least 1 mg / m 2 , optionally at least 2 mg / m 2 . In some embodiments, the amount of chromium is less than 250 mg / m 2 . In some embodiments, the amount of chromium can be in the range of 0.5–1 mg / cm 2 , optionally 1–2 mg / m 2 , optionally 2–5 mg / m 2 , optionally 5–10 mg / m 2 , optionally 10–20 mg / m 2 , optionally 20–50 mg / m 2 , optionally 50–75 mg / m 2 , optionally 75–100 mg / m 2 , optionally 100–250 mg / m 2 , or any combination of its ranges. In some embodiments, the surface layer or sub-layer having a chromium-containing material can be at least 0.2 nm thick, optionally at least 0.5 nm thick, optionally at least 1 nm thick, at least 2 nm thick. In some embodiments, the thickness of the surface layer or sub-layer having a chromium-containing material is in the range of 0.2–0.5 nm, optionally 0.5–1.0 nm, optionally 1.0–2.0 nm, optionally 2.0–5.0 nm, optionally 5.0–10 nm, optionally 10–20 nm, optionally 20–50 nm, optionally 50–100 nm, or any combination of its ranges.

[0064] Silicon compound (surface material C)

[0065] In some embodiments, the surface layer or sub-layer comprises a silicon compound formed by treatment with a silane, siloxane or silazane compound, any of which may be referred to herein as a silicon compound reagent. In some embodiments, treatment with a silicon compound reagent can increase the adhesion to an overlying sub-layer or to a continuous porous lithium storage layer. In some embodiments, the silicon compound can be a polymer including but not limited to polysiloxane. In some embodiments, the siloxane compound can have a general structure as shown in formula (1):

[0066] Si(R) n (OR’) 4-n (1)

[0067] wherein n = 1, 2 or 3, and R and R’ are independently selected substituted or unsubstituted alkyl, alkenyl or aryl groups.

[0068] The silicon compound of the layer or sublayer may be derived from a silicon compound reagent but have a chemical structure different from that of the reagent used to form it. In some embodiments, the silicon compound may react with the underlying surface to form bonds such as metal-oxygen-silicon bonds, and in doing so, the silicon compound may lose one or more functional groups (e.g., the OR' group from a siloxane). In some embodiments, the silicon compound reagent may include groups that polymerize to form a polymer. In some embodiments, the silicon compound reagent may form a Si-O-Si crosslinked matrix. In some embodiments, the PECVD deposition of the lithium storage material may alter the chemical structure of the silicon compound reagent or even form a secondary derived chemical. The silicon compound includes silicon. The silicon compound may be the result of the reaction of the silicon compound reagent with 1, 2, 3, or 4 reactants in 1, 2, 3, or 4 different reactions.

[0069] The silicon compound reagent may be provided, for example, in a solution at about 0.3 g / l to 15 g / l in water or an organic solvent. The adsorption methods of the silicon compound reagent include the immersion method, the showering method, and the spraying method, without particular limitation. In some embodiments, the silicon compound reagent may be provided in the form of a vapor and adsorbed onto the underlying sublayer. In some embodiments, the silicon compound reagent may be deposited by initiated chemical vapor deposition (iCVD). In some embodiments, the silicon compound reagent may include an olefin-functionalized silane moiety, an epoxy-functionalized silane moiety, an acryloyl-functionalized silane moiety, an amino-functionalized silane moiety, or a mercapto-functionalized silane moiety, optionally combined with a siloxane or silazane group. In some embodiments, the silicon compound reagent may be a siloxysilane. In some embodiments, the silicon compound reagent may undergo polymerization during or after deposition. Some non-limiting examples of the silicon compound reagent include hexamethyldisilazane (HMDS), vinyltrimethoxysilane, vinylphenyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 4-glycidylbutyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane, imidazole silane, triazine silane, 3-mercaptopropyltrimethoxysilane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, pentavinylpentamethylcyclopentasiloxane, and octavinyl-T8-silsesquioxane. In some embodiments, the layer or sublayer including the silicon compound may include silicon, oxygen, and carbon and may further include nitrogen or sulfur.

[0070] In some embodiments, after treatment with a silicon compound reagent, a step of distilling off the solvent or initiating polymerization or other chemical transformation may follow, where the step may involve heating, contacting with a reactive reagent, or both. The surface sublayer formed by the silicon compound reagent should not be so thick as to create a significant barrier to charge conduction between the current collector and the continuous porous lithium storage layer. In some embodiments, the silicon content of the sublayer formed by the silicon compound reagent is in the range of 0.1–0.2 mg / m 2 optionally in the range of 0.1–0.25 mg / m 2 optionally in the range of 0.25–0.5 mg / m 2 optionally in the range of 0.5–1 mg / m 2 optionally in the range of 1–2 mg / m 2 optionally in the range of 2–5 mg / m 2 optionally in the range of 5–10 mg / m 2 optionally in the range of 10–20 mg / m 2 optionally in the range of 20–50 mg / m 2 optionally in the range of 50–100 mg / m 2 optionally in the range of 100–200 mg / m 2 optionally in the range of 200–300 mg / m 2 , or any combination of ranges. In some embodiments, the surface layer or sublayer formed by the silicon compound reagent may comprise up to one monolayer, optionally up to two monolayers, of the silicon compound reagent or its reaction product; optionally up to 4 monolayers, optionally up to 6 monolayers, optionally up to 8 monolayers, optionally up to 10 monolayers, optionally up to 15 monolayers, optionally up to 20 monolayers, optionally up to 50 monolayers, optionally up to 100 monolayers, optionally up to 200 monolayers. The surface layer or surface sublayer having the silicon compound may be porous. In some embodiments, the silicon compound may decompose or partially decompose during the deposition of the lithium storage layer.

[0071] Metal oxide or metal chalcogenide (surface material D)

[0072] In some embodiments, the surface sublayer may comprise a metal oxide, and such a surface sublayer may be referred to as a metal oxide sublayer. In some embodiments, the metal oxide sublayer comprises a transition metal oxide. In some embodiments, the metal oxide sublayer comprises oxides of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium, or niobium. In some embodiments, the metal oxide sublayer is a conductive doped oxide, including but not limited to indium-doped tin oxide (ITO) or aluminum-doped zinc oxide (AZO). In some embodiments, the metal oxide sublayer comprises an alkali metal oxide or an alkaline earth metal oxide. In some embodiments, the metal oxide sublayer comprises an oxide of lithium. The metal oxide sublayer may comprise a mixture of metals. For example, "oxide of nickel" may optionally include other metals in addition to nickel. In some embodiments, the metal oxide sublayer comprises an oxide of an alkali metal (such as lithium or sodium) or an alkaline earth metal (such as magnesium or calcium) and an oxide of a transition metal (such as titanium, nickel, or copper). In some embodiments, the metal oxide sublayer may comprise a small amount of hydroxide such that the ratio of oxygen atoms in the hydroxide form to the oxide is less than 1 to 4, respectively. The metal oxide sublayer may comprise stoichiometric oxides, non-stoichiometric oxides, or both. In some embodiments, the metals within the metal oxide sublayer may exist in multiple oxidation states. Generally, metal oxysalts may be considered a subclass of metal oxides. For clarity, any mention of "metal oxide" in the context of the surface sublayer in this document does not include metal oxysalts.

[0073] In some embodiments, the thickness of the metal oxide sublayer may be at least 1 monolayer, optionally at least 2, 3, 5, or 10 monolayers. In some embodiments, the average thickness of the metal oxide sublayer may be at least 0.1 nm, optionally at least 0.2 nm. In some embodiments, the average thickness of the metal oxide sublayer is less than 5000 nm, optionally less than 3000 nm. In some embodiments, the average thickness of the metal oxide sublayer is in the range of 0.5–1 nm, optionally 1–2 nm, optionally 2–5 nm, optionally 5 to 10 nm, optionally 10–20 nm, optionally 20–50 nm, optionally 50–100 nm, optionally 100–200 nm, optionally 200–500 nm, optionally 500–1000 nm, optionally 1000–1500 nm, optionally 1500–2000 nm, optionally 2000–2500 nm, optionally 2500–3000 nm, optionally 3000–4000 nm, optionally 4000–5000 nm, or any combination of these ranges.

[0074] In some embodiments, the metal oxide sublayer is formed by atomic layer deposition (ALD), chemical vapor deposition (CVD), hot gas phase deposition, or sputtering.

[0075] In some embodiments, as described above, the metal oxide sublayer precursor composition can be coated or printed over a current collector having one or more surface sublayers and then processed to form the metal oxide sublayer. Some non-limiting examples of metal oxide precursor compositions include sol-gels (metal alkoxides), metal carbonates, metal acetates (including organic acetates), metal hydroxides, and metal oxide dispersions. The metal oxide precursor composition can be heat-treated to form the metal oxide sublayer.

[0076] In some embodiments, the metal oxide sublayer precursor composition includes a metal, such as a metal-containing particle or a sputtered metal layer. The metal can then be oxidized in the presence of oxygen (e.g., heat), electrochemically oxidized, chemically oxidized in an oxidizing liquid or gas medium, etc. to form the metal oxide sublayer.

[0077] In some embodiments, the sublayer can include a metal chalcogenide, such as a metal sulfide or a metal selenide. The metal chalcogenide can be deposited by ALD, CVD, hot gas phase deposition, or sputtering. Alternatively, the metal chalcogenide can be deposited from a solution or mixture by a coating method. In some embodiments, the metal chalcogenide sublayer can be formed by a chemical reaction of a metal with a metal sulfide-forming reactant. In some embodiments, the average thickness of the metal chalcogenide sublayer is at least 0.1 nm, optionally at least 0.2 nm. In some embodiments, the average thickness of the metal chalcogenide sublayer can be less than 5000 nm, optionally less than 3000 nm. In some embodiments, the average thickness of the metal oxide sublayer is in the range of 0.5–1 nm, optionally 1–2 nm, optionally 2–5 nm, optionally 5 to 10 nm, optionally 10–20 nm, optionally 20–50 nm, optionally 50–100 nm, optionally 100–200 nm, optionally 200–500 nm, optionally 500–1000 nm, optionally 1000–1500 nm, optionally 1500–2000 nm, optionally 2000–2500 nm, optionally 2500–3000 nm, optionally 3000–4000 nm, optionally 4000–5000 nm, or any combination of ranges thereof.

[0078] In some embodiments, the ratio of the average thickness of the surface layer (including all sublayers, if present) to the average thickness of the conductive layer is less than 1, optionally less than 0.5, optionally less than 0.2, optionally less than 0.1, optionally less than 0.05, optionally less than 0.02, optionally less than 0.01, optionally less than 0.005.

[0079] In some embodiments, before depositing a continuous porous lithium storage layer, the current collector can be heat-treated (optionally under inert conditions). This heating can improve the physical properties of the current collector, for example, by reducing internal stress, improving the adhesion between the various layers and sub-layers of the current collector, or both. The temperature and time of the above heat treatment step largely depend on the material selection. In some embodiments, the heat treatment includes heating to a temperature in the range of 100–200 °C, optionally 200–300 °C, optionally 300–400 °C, optionally 400–500 °C, or any combination of these ranges. In some embodiments, the heat treatment step includes exposure to one of the above temperature ranges for a duration in the range of 1–10 minutes, optionally 10–30 minutes, optionally 30–60 minutes, optionally 1–2 hours, optionally 2–4 hours, optionally 4–8 hours, optionally 8–16 hours, optionally 16–24 hours, or any combination of these ranges.

[0080] Lithium storage layer

[0081] In some embodiments, the lithium storage layer can be a continuous porous lithium storage layer, which includes a porous material capable of reversibly binding lithium. In some embodiments, the continuous porous lithium storage layer includes silicon, germanium, antimony, tin, or a mixture of two or more of these elements. In some embodiments, the continuous porous lithium storage layer is substantially amorphous. In some embodiments, the continuous porous lithium storage layer includes substantially amorphous silicon. Such a substantially amorphous storage layer can include a small amount (e.g., less than 20 atomic %) of crystalline material dispersed therein. The continuous porous lithium storage layer can include dopants, such as hydrogen, boron, phosphorus, sulfur, fluorine, aluminum, gallium, indium, arsenic, antimony, bismuth, nitrogen, or metal elements. In some embodiments, the continuous porous lithium storage layer can include porous substantially amorphous hydrogenated silicon (a-Si:H) with a hydrogen content of, for example, 0.1 to 20 atomic % or higher. In some embodiments, the continuous porous lithium storage layer can include methylated amorphous silicon. Note that unless otherwise specifically mentioned, any measure of atomic % for the lithium storage material or lithium storage layer here refers to atoms other than hydrogen.

[0082] In some embodiments, the continuous porous lithium storage layer comprises at least 40 atomic % of silicon, germanium, or a combination thereof, optionally at least 50 atomic %, optionally at least 60 atomic %, optionally at least 70 atomic %, optionally at least 80 atomic %, optionally at least 90 atomic %. In some embodiments, the continuous porous lithium storage layer comprises at least 40 atomic % of silicon, optionally at least 50 atomic %, optionally at least 60 atomic %, optionally at least 70 atomic %, optionally at least 80 atomic %, optionally at least 90 atomic %, optionally at least 95 atomic %, optionally at least 97 atomic %. Note that in the case of the prelithiated anodes discussed below, the lithium content is excluded from this atomic % characterization.

[0083] In some embodiments, the continuous porous lithium storage layer comprises less than 10 atomic % of carbon, optionally less than 5 atomic %, optionally less than 2 atomic %, optionally less than 1 atomic %, optionally less than 0.5 atomic %. In some embodiments, the continuous porous lithium storage layer is substantially free (i.e., the continuous porous lithium storage layer comprises less than 1 wt%, optionally less than 0.5 wt%) of carbon-based binders, graphite carbon, graphene, graphene oxide, reduced graphene oxide, carbon black, and conductive carbon. Some non-limiting examples of carbon-based binders can include organic polymers such as polymers based on styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, or polyacrylonitrile.

[0084] The continuous porous lithium storage layer can include voids or gaps (pores) that can be random or non-uniform with respect to size, shape, and distribution. Such porosity does not result from the formation of any recognizable lithium storage nanostructures such as nanowires, nanocolumns, nanotubes, ordered nanochannels, etc., or cause the formation of any recognizable lithium storage nanostructures such as nanowires, nanocolumns, nanotubes, ordered nanochannels, etc. In some embodiments, the pores can be polydisperse. In some embodiments, the continuous porous lithium storage layer can be characterized as nanoporous. In some embodiments, the average density of the continuous porous lithium storage layer is in the range of 1.0–1.1 g / cm 3 optionally 1.1–1.2 g / cm 3 optionally 1.2–1.3 g / cm 3 optionally 1.3–1.4 g / cm 3 optionally 1.4–1.5 g / cm 3 optionally 1.5–1.6 g / cm 3 optionally 1.6–1.7 g / cm 3 optionally 1.7–1.8 g / cm 3 optionally 1.8–1.9 g / cm 3 optionally 1.9–2.0 g / cm 3, optionally 2.0–2.1 g / cm 3 , optionally 2.1–2.2 g / cm 3 , optionally 2.2–2.25 g / cm 3 , optionally 2.25–2.29 g / cm 3 , within the range of, or any combination of its ranges, and including at least 70 atomic % silicon, 80 atomic % silicon, optionally at least 85 atomic % silicon, optionally at least 90 atomic % silicon, optionally at least 95 atomic % silicon. Note that a density less than 2.3 g / cm 3 is evidence of the porous nature of the lithium storage layer containing a-Si.

[0085] In some embodiments, most of the active material (e.g., silicon, germanium, or their alloys) in the continuous porous lithium storage layer has substantial lateral connectivity across portions of the current collector coating, and this connectivity extends around random pores and gaps. Referring again to Figure 1 , in some embodiments, "substantial lateral connectivity" means that the active material at a point X in the continuous porous lithium storage layer 107 can be connected to the active material at a second point X' in the layer by a linear lateral distance LD that is at least as large as the average thickness T of the continuous porous lithium storage layer, optionally a lateral distance that is at least 2 times the thickness, optionally a lateral distance that is at least 3 times the thickness. Not shown, the total path distance of the material connection (including bypassing pores and following the topography of the current collector) can be longer than LD. In some embodiments, the continuous porous lithium storage layer can be described as a matrix of interconnected silicon, germanium, or their alloys, in which random pores and gaps are embedded. In some embodiments, the continuous porous lithium storage layer can have a sponge-like form. It should be noted that the continuous porous lithium storage layer does not necessarily extend through the entire anode without any lateral breaks, can include random discontinuities or cracks, and is still considered continuous. In some embodiments, such discontinuities can occur more frequently on a rough current collector surface. In some embodiments, the continuous porous lithium storage layer can include adjacent columns of silicon and / or silicon nanoparticle aggregates.

[0086] In some embodiments, the continuous porous lithium storage layer includes oxides of sub-stoichiometric silicon (SiO x ), germanium (GeO x ), or tin (SnO x ), where the ratio of oxygen atoms to silicon, germanium, or tin atoms is less than 2:1, i.e., x < 2, optionally less than 1:1, i.e., x < 1. In some embodiments, x is in the range of 0.02 to 0.95, optionally 0.02 to 0.10, optionally 0.10 to 0.50, or optionally 0.50 to 0.95, optionally 0.95 to 1.25, optionally 1.25 to 1.50, or any combination of its ranges.

[0087] In some embodiments, the continuous porous lithium storage layer comprises a nitride of sub-stoichiometric silicon (SiN y ), germanium (GeN y ), or tin (SnN y ), 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 embodiments, y ranges from 0.02 to 0.95, optionally from 0.02 to 0.10, optionally from 0.10 to 0.50, or optionally from 0.50 to 0.95, optionally from 0.95 to 1.20, or any combination of its ranges. The lithium storage layer having sub-stoichiometric silicon nitride may also be referred to as nitrogen-doped silicon or silicon-nitrogen alloy.

[0088] In some embodiments, the continuous porous lithium storage layer comprises an oxynitride of sub-stoichiometric silicon (SiO x N y ), germanium (GeO x N y ), or tin (SnO x N y ), wherein the total number of oxygen and nitrogen atoms to silicon, germanium, or tin atoms is less than 1:1, i.e., (x + y) < 1. In some embodiments, (x + y) ranges from 0.02 to 0.95, optionally from 0.02 to 0.10, optionally from 0.10 to 0.50, or optionally from 0.50 to 0.95, or any combination of its ranges.

[0089] In some embodiments, the above sub-stoichiometric oxides, nitrides, or oxynitrides are provided by a CVD process, including but not limited to a PECVD process. Oxygen and nitrogen can be provided uniformly within the continuous porous lithium storage layer, or optionally, the oxygen or nitrogen content can vary as a function of the storage layer thickness.

[0090] CVD

[0091] CVD generally involves introducing precursor gases, vaporized liquids or gas and liquid inlets according to direct liquid injection CVD into a chamber containing one or more objects to be coated, typically heated. Chemical reactions may occur on and near the hot surface, resulting in film deposition on the surface. This is accompanied by the production of chemical by-products, which are exhausted from the chamber together with the unreacted precursor gases. Due to the wide variety of deposited materials and their extensive applications, many variations of CVD can be expected, which can be used to form lithium storage layers, surface layers or sub-layers, supplementary layers (see below) or other layers. In some embodiments, it can be carried out in a hot-wall reactor or a cold-wall reactor at pressures from sub- torr to above atmospheric pressure, with or without a carrier gas, and at temperatures typically in the range of 100 - 1600 °C. There are also a variety of enhanced CVD processes, which involve using plasma, ions, photons, lasers, hot filaments or combustion reactions to increase the deposition rate and / or reduce the deposition temperature. Various process conditions can be used to control the deposition, including but not limited to temperature, precursor materials, gas flow rate, pressure, substrate bias (if applicable) and plasma energy (if applicable).

[0092] As described above, a continuous porous lithium storage layer, such as a layer of silicon or germanium or both, can be provided by plasma enhanced chemical vapor deposition (PECVD). Relative to conventional CVD, deposition by PECVD can generally be carried out at lower temperatures and higher rates, which is advantageous for higher manufacturing yields. In some embodiments, PECVD is used to deposit a substantially amorphous silicon layer (optionally doped) above the surface layer. In some embodiments, PECVD is used to deposit a substantially amorphous continuous porous silicon layer above the surface layer.

[0093] In the PECVD process, according to various embodiments, the plasma can be generated in the chamber in which the substrate is configured or upstream of the chamber and fed into the chamber. Various types of plasma can be used, including but not limited to capacitively coupled plasma, inductively coupled plasma and conductively coupled plasma. Any suitable plasma source can be used, including DC, AC, RF, VHF, and a combined PECVD and microwave source can be used. In some embodiments, magnetron-assisted RF PECVD can be used.

[0094] As is well known in the art, the PECVD process conditions (temperature, pressure, precursor gas, carrier gas, dopant gas, flow rate, energy, etc.) can vary depending on the specific process and tool used.

[0095] In some embodiments, the PECVD process is an extended thermal plasma chemical vapor deposition (ETP-PECVD) process. In such a process, a plasma generating gas forms a plasma through a DC arc plasma generator, optionally together with a mesh or other substrate including a current collector in an adjacent vacuum chamber. A silicon source gas is injected into the plasma to generate free radicals. The plasma is expanded via a diverging nozzle and is injected into the vacuum chamber and towards the substrate. An example of the plasma generating gas is argon (Ar). In some embodiments, the ionized argon species in the plasma collide with the silicon source molecules to form free radical species of the silicon source, resulting in deposition onto the current collector. Example ranges for the voltage and current of the DC plasma source are 60 to 80 volts and 40 to 70 amperes, respectively.

[0096] Any suitable silicon source can be used to deposit silicon. In some embodiments, the silicon source can be a silane-containing gas, including but not limited to silane (SiH4), dichlorosilane (H2SiCl2), monochlorosilane (H3SiCl), trichlorosilane (HSiCl3), silicon tetrachloride (SiCl4), and diethylsilane. Depending on the gas used, the silicon layer can be formed by decomposition or reaction with other compounds, such as by hydrogen reduction. In some embodiments, the gas can include a silicon source, such as silane, an inert gas, such as helium, argon, neon, or xenon, optionally one or more dopant gases, and substantially no hydrogen. In some embodiments, the gas can include argon, silane, and hydrogen, and optionally some dopant gases. In some embodiments, the gas flow ratio of argon to the combined gas flow of silane and hydrogen is at least 3.0, optionally at least 4.0. In some embodiments, the gas flow ratio of argon to the combined gas flow of silane and hydrogen is in the range of 3–5, optionally 5–10, optionally 10–15, optionally 15–20, or any combination of ranges. In some embodiments, the gas flow ratio of hydrogen to silane is in the range of 0–0.1, optionally 0.1–0.2, optionally 0.2–0.5, optionally 0.5–1, optionally 1–2, optionally 2–5, or any combination of ranges. In some embodiments, when the gas flow ratio of silane to the combined gas flow of silane and hydrogen increases, silicon with a higher porosity can be formed and / or the silicon deposition rate can be increased. In some embodiments, the dopant gas is borane or phosphine, which can be optionally mixed with a carrier gas. In some embodiments, the gas flow ratio of the dopant gas (e.g., borane or phosphine) to the silicon source gas (e.g., silane) is in the range of 0.0001–0.0002, optionally 0.0002–0.0005, optionally 0.0005–0.001, optionally 0.001–0.002, optionally 0.005-0.01, optionally 0.002–0.005, optionally 0.005–0.01, optionally 0.01–0.02, optionally 0.02–0.05, optionally 0.05–0.10, or any combination of ranges. Such gas flow ratios as described above can refer to relative gas flow rates, e.g., in standard cubic centimeters per minute (SCCM). In some embodiments, the PECVD deposition conditions and gases can be changed during the deposition process.

[0097] In some embodiments, during at least a portion of the PECVD deposition, the temperature at the current collector is in the range of 20 °C to 50 °C, 50 °C to 100 °C, optionally 100 °C to 200 °C, optionally 200 °C to 300 °C, optionally 300 °C to 400 °C, optionally 400 °C to 500 °C, optionally 500 °C to 600 °C, or any combination of these ranges. In some embodiments, the temperature may vary during the PECVD deposition. For example, the temperature may be higher during the early stage of PECVD than during the later stage. Alternatively, the temperature during the later stage of PECVD may be higher than during the early stage.

[0098] The thickness or mass per unit area of the continuous porous lithium storage layer depends on the storage material, the desired charge capacity, and other operational and lifetime considerations. Increasing the thickness generally provides greater capacity. If the continuous porous lithium storage layer becomes too thick, the resistance may increase and the stability may decrease. In some embodiments, the anode may be characterized as having an active silicon areal density of at least 1.0 mg / cm 2 , optionally at least 1.5 mg / cm 2 , optionally at least 3 mg / cm 2 , optionally at least 5 mg / cm 2 . In some embodiments, the lithium storage structure may be characterized as having an active silicon areal density in the range of 1.5–2 mg / cm 2 , optionally in the range of 2–3 mg / cm 2 , optionally in the range of 3–5 mg / cm 2 , optionally in the range of 5–10 mg / cm 2 , optionally in the range of 10–15 mg / cm 2 , optionally in the range of 15–20 mg / cm 2 , or any combination of its continuous ranges. "Active silicon" refers to the silicon that is electrically connected to the current collector and is available for reversible lithium storage at the start of battery cycling, e.g., after the "electrochemical formation" of the anode discussed later. "Areal density" refers to the surface area of the conductive layer on which the active silicon is provided. In some embodiments, not all of the silicon content is active silicon, i.e., some may be occupied in the form of non-active silicides or may be electrically isolated from the current collector.

[0099] In some embodiments, the continuous porous lithium storage layer has an average thickness of at least 1 μm, optionally at least 2.5 μm, optionally at least 6.5 μm. In some embodiments, the continuous porous lithium storage layer has an average thickness in the range of about 0.5 μm to about 50 μm. In some embodiments, the continuous porous lithium storage layer comprises at least 80 atomic % amorphous silicon and / or has a thickness in the range of 1–1.5 μm, optionally 1.5–2.0 μm, optionally 2.0–2.5 μm, optionally 2.5–3.0 μm, optionally 3.0–3.5 μm, optionally 3.5–4.0 μm, optionally 4.0–4.5 μm, optionally 4.5–5.0 μm, optionally 5.0–5.5 μm, optionally 5.5–6.0 μm, optionally 6.0–6.5 μm, optionally 6.5–7.0 μm, optionally 7.0–8.0 μm, optionally 8.0–9.0 μm, optionally 9.0–10 μm, optionally 10–15 μm, optionally 15–20 μm, optionally 20–25 μm, optionally 25–30 μm, optionally 30–40 μm, optionally 40–50 μm, or any combination of ranges thereof.

[0100] Other anode features

[0101] The anode may optionally include various additional layers and features. The current collector may include more than one feature to ensure reliable electrical connection in the energy storage device. In some embodiments, a supplementary layer is provided over the patterned lithium storage structure. In some embodiments, the supplementary layer is a protective layer to enhance the lifespan or physical durability. The supplementary layer may be an oxide formed from the lithium storage material itself, e.g., silicon dioxide in the case of silicon, or some other suitable material. The supplementary layer may be deposited, for example, by ALD, CVD, PECVD, evaporation, sputtering, solution coating, inkjet, or any method compatible with the anode. In some embodiments, the top surface of the supplementary layer may correspond to the top surface of the anode.

[0102] The supplementary layer should reasonably conduct lithium ions and allow lithium ions to move into and out of the patterned lithium storage structure during charging and discharging. In some embodiments, the lithium ion conductivity of the supplementary layer is at least 10 -9 S / cm, optionally at least 10 - 8 S / cm, optionally at least 10 -7 S / cm, optionally at least 10 -6 S / cm. In some embodiments, the supplementary layer acts as a solid-state electrolyte.

[0103] Some non-limiting examples of materials used in the supplementary layer include metal oxides, nitrides, or oxynitrides, such as those oxides, nitrides, or oxynitrides containing aluminum, titanium, vanadium, zirconium, hafnium, or tin, or mixtures thereof. The metal oxides, metal nitrides, or metal oxynitrides may include other components, such as phosphorus or silicon. The supplementary layer may include a lithium-containing material, such as lithium phosphorus oxynitride (LIPON), lithium phosphate, lithium aluminum oxide, (Li,La) x Ti y O z or Li x Si y Al2O3. In some embodiments, the supplementary layer comprises a metal oxide, metal nitride, or metal oxynitride and has an average thickness of less than about 100 nm, such as in the range of about 0.1 to about 10 nm, or optionally in the range of about 0.2 nm to about 5 nm. LIPON or other solid electrolyte materials with excellent lithium transport properties may have a thickness greater than 100 nm, but optionally, it may be in the range of about 1 to about 50 nm.

[0104] In some embodiments, the continuous porous lithium storage layer may be at least partially prelithiated before the first electrochemical cycle after battery assembly, or optionally before battery assembly. That is, even before the first battery cycle, some lithium can be incorporated into the continuous porous lithium storage layer to form a lithiated storage layer. In some embodiments, the lithiated storage layer may break into smaller structures, including but not limited to small flakes, which remain electrochemically active and continuously and reversibly store lithium. Note that "lithiated storage layer" simply means that at least some of the potential storage capacity of the lithium storage layer is filled, but not necessarily all. In some embodiments, the lithiated storage layer may include lithium in the range of 1% to 5%, optionally 5% to 10%, optionally 10% to 15%, optionally 15% to 20%, optionally 20% to 30%, optionally 30% to 40%, optionally 40% to 50%, optionally 50% to 60%, optionally 60% to 70%, optionally 70% to 80%, optionally 80% to 90%, optionally 90% to 100% of the theoretical lithium storage capacity of the continuous porous lithium storage layer, or any combination of its ranges. In some embodiments, the surface layer may capture some lithium, and one may need to consider this capture to achieve the desired lithium range in the lithiated storage layer.

[0105] In some embodiments, prelithiation may include depositing lithium metal, for example, by evaporation, electron beam, or sputtering, over a continuous porous lithium storage layer, or between more than one lithium storage sub-layer, or both. Alternatively, prelithiation may include contacting the anode with a reducing lithium organic compound, such as lithium naphthalide, n-butyllithium, etc. In some embodiments, prelithiation may include binding lithium by electrochemically reducing lithium ions in a prelithiation solution. In some embodiments, prelithiation may include heat treatment to assist in the diffusion of lithium into the lithium storage layer.

[0106] In some embodiments, the anode may be heat treated prior to battery assembly. In some embodiments, heat treating the anode, for example, by inducing migration of metal from the current collector or atoms from an optional supplementary layer into the continuous porous lithium storage layer, may improve the adhesion or conductivity of the various layers. In some embodiments, the continuous porous lithium storage layer comprises at least 80 atomic % amorphous silicon and at least 0.05 atomic % copper, optionally at least 0.1 atomic % copper, optionally at least 0.2 atomic % copper, optionally at least 0.5 atomic % copper, optionally at least 1 atomic % copper. In some embodiments, the continuous porous lithium storage layer may comprise at least 80 atomic % amorphous silicon and further comprise copper in an atomic % range of 0.05–0.1%, optionally 0.1–0.2%, optionally 0.2–0.5%, optionally 0.5–1%, optionally 1–2%, optionally 2–3%, optionally 3–5%, optionally 5–7%, or any continuous combination of ranges thereof. In some embodiments, the foregoing atomic % copper ranges may correspond to a cross-sectional area of the continuous porous lithium storage layer of at least 1 μm 2 which may be measured, for example, by energy dispersive x-ray spectroscopy (EDS). In some embodiments, there is a gradient where the copper concentration in the portion of the continuous porous lithium storage layer near the current collector is higher than the portion away from the current collector. In some embodiments, for example, when the surface layer comprises a metal oxide layer of TiO2, instead of or in addition to copper, the continuous porous lithium storage layer may comprise other transition metals, such as zinc, chromium, or titanium. The atomic % of such transition metal (Zn, Cr, or Ti) may be present in the continuous porous lithium storage layer in any of the atomic % ranges described above relative to copper. In some embodiments, the continuous porous lithium storage layer may comprise more copper than other transition metals. Special heat treatment is not always necessary to effect migration of the transition metal into the lithium storage layer.

[0107] In some embodiments, the heat treatment of the anode can be carried out in a controlled environment with low oxygen and water (e.g., less than 10 ppm or a partial pressure of less than 0.1 Torr, optionally less than 0.01 Torr to prevent decomposition). In some embodiments, the anode heat treatment can be carried out using an oven, an infrared heating element, contact with a hot plate, or exposure to a flash lamp. The temperature and time of the anode heat treatment depend on the material of the anode. In some embodiments, the anode heat treatment includes heating the anode to at least 50 °C, optionally in the range of 50 °C to 950 °C, optionally 100 °C to 250 °C, optionally 250 °C to 350 °C, optionally 350 °C to 450 °C, optionally 450 °C to 550 °C, optionally 550 °C to 650 °C, optionally 650 °C to 750 °C, optionally 750 °C to 850 °C, optionally 850 °C to 950 °C, or a combination of these ranges. In some embodiments, the heat treatment can be applied for a time of 0.1 to 120 minutes.

[0108] In some embodiments, the above-described one or more processing steps can be carried out using a roll-to-roll method, where the conductive layer or current collector is in the form of a rolled-up film, such as a roll of metal foil, mesh, or fabric.

[0109] Battery characteristics

[0110] The foregoing description mainly relates to the anode / negative electrode of a lithium-ion battery (LIB). An LIB typically includes a cathode / positive electrode, an electrolyte, and a separator (if a solid-state electrolyte is not used). It is well known that a battery can be formed as a multi-layer stack of an anode and a cathode with a separator in between. Alternatively, the anode / cathode stack can be formed into a so-called jelly-roll. Such a structure is placed into a suitable housing with the required electrical contacts.

[0111] Cathode

[0112] Positive electrode (cathode) materials include, but are not limited to, lithium metal oxides or compounds (e.g., LiCoO2, LiFePO4, LiMnO2, LiNiO2, LiMn2O4, LiCoPO4, LiNi x Co y Mn z O2, LiNi X Co Y Al Z O2, LiFe2(SO4)3 or Li2FeSiO4), carbon fluoride, metal fluorides such as iron fluoride (FeF3), metal oxides, sulfur, selenium, and combinations thereof. The cathode active material can operate, for example, by insertion, conversion, or combination. The cathode active material is typically disposed on a conductive cathode current collector or is in electrical communication with a conductive cathode current collector.

[0113] Current separator

[0114] The current separator allows ions to flow between the anode and the cathode, but prevents direct electrical contact. Such a separator is typically a porous sheet. The non-aqueous lithium-ion separator is a single-layer or multi-layer polymer sheet, usually made of polyolefin, especially for small batteries. Most commonly, these are based on polyethylene or polypropylene, but polyethylene terephthalate (PET) and polyvinylidene fluoride (PVdF) can also be used. For example, the separator can have a porosity > 30%, low ionic resistivity, a thickness of ~10 to 50 μm, and high volume puncture strength. For example, to provide higher mechanical and thermal stability, the separator can optionally include a glass material, a ceramic material, a ceramic material embedded in the polymer, a polymer coated with a ceramic, or some other composite or multi-layer structure.

[0115] Electrolyte

[0116] The electrolyte in a lithium-ion battery can be liquid, solid, or gel. Typical liquid electrolytes include more than one solvent and more than one salt, at least one of which includes lithium. During the first few charge cycles (sometimes called formation cycles), the organic solvent and / or the electrolyte can partially decompose on the negative electrode surface to form a SEI (solid-electrolyte-interphase) layer. SEI is usually electrically insulating but ion-conductive, thus allowing lithium ions to pass through. SEI can reduce the decomposition of the electrolyte in later charge cycles.

[0117] Some non-limiting examples of non-aqueous solvents suitable for some lithium-ion batteries include the following: cyclic carbonates (e.g., ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), butylene carbonate (BC), and vinylene ethylene carbonate (VEC)), vinylene carbonate (VC), lactones (e.g., γ-butyrolactone (GBL), γ-valerolactone (GVL), and α-angelica lactone (AGL)), linear carbonates (e.g., dimethyl carbonate (DMC), methyl ethyl carbonate (MEC, usually also abbreviated as EMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC), methyl butyl carbonate (NBC), 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., dimethylformamide), 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.

[0118] Non-aqueous liquid solvents can be used in combination. Examples of such combinations include combinations of cyclic carbonates-linear carbonates, cyclic carbonates-lactones, cyclic carbonates-lactones-linear carbonates, cyclic carbonates-linear carbonates-lactones, cyclic carbonates-linear carbonates-ethers, and cyclic carbonates-linear carbonates-linear esters. In some embodiments, cyclic carbonates can be combined with linear esters. Additionally, cyclic carbonates can be combined with lactones and linear esters. In some embodiments, the weight ratio or optionally the volume ratio of cyclic carbonates to linear esters ranges from 1:9 to 10:1, optionally from 2:8 to 7:3.

[0119] Salts for use in the liquid electrolyte can include more than one of the following non-limiting examples: LiPF6, LiBF4, LiClO4, LiAsF6, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiCF3SO3, LiCF4(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) 2x Li and (CF2)3(SO2) 2x Li), LiFSI (lithium bis(fluorosulfonyl)imide), LiTDI (lithium 4,5-dicyano-2-(trifluoromethyl)imidazole), and combinations thereof.

[0120] In some embodiments, the total concentration of the lithium salt in the liquid non-aqueous solvent (or solvent combination) is at least 0.3 M, optionally at least 0.7 M. The upper concentration limit can be driven by solubility limits and the operating temperature range. In some embodiments, the concentration of the salt is no greater than about 2.5 M, optionally no greater than about 1.5 M. In some embodiments, the electrolyte can include a saturated solution of a lithium salt and an excess of solid lithium salt.

[0121] In some embodiments, the battery electrolyte includes a non-aqueous ionic liquid and a lithium salt. Additives can be included in the electrolyte to serve various functions, such as stabilizing the battery. For example, an additive such as a polymerizable compound having an unsaturated double bond can be added to stabilize or modify the SEI. Certain amine or borate compounds can be used as cathode protectants. A Lewis acid can be added to stabilize fluorinated anions, such as PF6. Safety protectants include those for protecting against overcharging, such as anisole, or those used as flame retardants, such as alkyl phosphates.

[0122] A solid electrolyte can be used without a separator because it itself acts as a separator. It is electrically insulating, ion-conductive, and electrochemically stable. In a solid electrolyte configuration, a lithium salt is used, which can be the same as in the above liquid electrolyte battery, but instead of being dissolved in an organic solvent, it is held in a solid polymer composite. Examples of solid polymer electrolytes can be ion-conductive polymers prepared from monomers containing atoms with lone pairs of electrons (the lithium ions of the electrolyte salt can attach to the lone pairs of electrons and move between the lone pairs of electrons) during conduction, such as polyvinylidene fluoride (PVDF) or its chloride or copolymer derivatives, poly(chlorotrifluoroethylene), poly(ethylene-chlorotrifluoroethylene) or poly(fluorinated ethylene-propylene), polyethylene oxide (PEO) and oxyethylene-linked PEO, PEO-PPO-PEO crosslinked with trifunctional polyurethane, poly(bis(methoxy-ethoxy-ethanolate))-phosphazene (MEEP), triol-type PEO crosslinked with difunctional polyurethane, poly((oligo)oxyethylene) methacrylate-co-methacrylic acid alkali metal salt, polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polymethacrylonitrile (PMAN), polysiloxane and its copolymers and derivatives, acrylate-based polymers, other similar solvent-free polymers, combinations of the foregoing polymers that are condensed or crosslinked to form different polymers, and physical mixtures of any of the foregoing polymers. Other polymers with relatively poor conductivity that can be used in combination with the above polymers to improve the strength of the thin laminate include polyester (PET), polypropylene (PP), polyethylene naphthalate (PEN), polyvinylidene fluoride (PVDF), polycarbonate (PC), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE). Such solid polymer electrolytes can further include a small amount of organic solvents, such as those listed above. The polymer electrolyte can be an ionic liquid polymer. Such polymer-based electrolytes can be coated using any number of conventional methods, such as curtain coating, slot coating, spin coating, inkjet coating, spray coating, or other suitable methods.

[0123] In some embodiments, the pristine non-cycled anode may undergo structural or chemical changes during electrochemical charge / discharge, e.g., originating from normal battery use or from an earlier "electrochemical formation step". As is known in the art, the electrochemical formation step is typically used to form the initial SEI layer and involves relatively mild conditions of low current and limited voltage. Despite such structural and / or chemical changes relative to the pristine non-cycled anode, the modified anode prepared, in part, by such electrochemical charge / discharge cycles may still have excellent performance. In some embodiments, the lithium storage layer of the cycled anode may no longer appear as a continuous layer, but rather as discrete columns or islands, typically having an aspect ratio of height to width of less than 2. While not bound by theory, in the case of amorphous silicon, it may be that there is some delamination during cycling in high stress regions. Optionally, or additionally, it may be that the structural changes during lithiation and delithiation may be asymmetric, resulting in such islands or columns.

[0124] In some embodiments, the electrochemical cycling conditions may be set to utilize only a portion of the theoretical charge / discharge capacity of silicon (3600 mAh / g). In some embodiments, the electrochemical charge / discharge cycles may be set to utilize 400–600 mAh / g, optionally 600–800 mAh / g, optionally 800–1000 mAh / g, optionally 1000–1200 mAh / g, optionally 1200–1400 mAh / g, optionally 1400–1600 mAh / g, optionally 1600–1800 mAh / g, optionally 1800–2000 mAh / g, optionally 2000–2200 mAh / g, optionally 2200–2400 mAh / g, optionally 2400–2600 mAh / g, optionally 2600–2800 mAh / g, optionally 2800–3000 mAh / g, optionally 3000–3200 mAh / g, optionally 3200–3400 mAh / g, or any combination of ranges thereof.

[0125] Examples

[0126] Test Group A

[0127] Comparative Anode C-1A

[0128] The current collector sample CC-1A is a 26-μm thick copper foil with a surface roughness of Ra = 0.164 μm and Rz = 1.54 μm. CC-1 does not have the surface layer of the present disclosure. An attempt was made to deposit silicon on one side of CC-1 for 30 minutes at about 300 °C and an RF power of about 225 W using an Oxford Plasmalabs System 100 PECVD tool. The deposition gas was a mixture of silane and argon with a gas flow ratio of about 1 to 12, respectively. Hydrogen was not used. For the electrochemical tests, the silicon did not adhere well and no further characterization was performed.

[0129] Example anode E-1A

[0130] The current collector sample CC-2A is a commercially available 10-μm thick copper foil with a surface roughness of Ra = 0.325 μm and Rz = 2.85 μm. Based on product literature and analytical data, it is believed that CC-2A includes the surface layer of the present disclosure, which has a first surface sublayer of zinc, a second surface sublayer of a metal-oxide compound including chromium, and a third surface sublayer of a silicon compound. An adherent amorphous silicon film (continuous porous lithium storage layer) with a thickness of about 9 μm was deposited using the same method as the comparative anode C-1A described above, with a density of about 1.9 mg / cm 3 but a deposition time of 50 minutes. Figure 7 The SEM cross-section shown in [reference] shows a continuous porous lithium storage layer 707 (amorphous Si) disposed above the current collector 701. The surface roughness of the current collector 701 (only a part is shown) is mainly caused by the conductive layer 703 (i.e., the copper foil). The surface layer 705 is difficult to resolve in the SEM, but is generally conformally deposited over the copper and can have a thickness of less than about 200 nm. Two regions of the continuous porous lithium storage layer were analyzed by energy dispersive x-ray spectroscopy (EDS). It was found that region 1 closest to the current collector had about 5 atomic % copper and 95 atomic % silicon. It was found that region 2 farther from the current collector had about 1 atomic % copper and 99 atomic % silicon. As described above, in some embodiments, the migration of metal from the current collector can improve the conductivity within the continuous porous lithium storage layer or other physical properties of the anode. The EDS of anode E-1A indicates some migration of copper from the current collector to the continuous porous lithium storage layer, which can improve the conductivity within the continuous porous lithium storage layer.

[0131] Example anode E-2A

[0132] The current collector sample CC-3A is a commercially available copper foil with a thickness of 18 μm, a surface roughness Ra = 0.285 μm, and Rz = 2.79 μm. Based on product literature and analytical data, it is believed that CC-3A includes the surface layer of the present disclosure, which has a first surface sublayer of zinc, a second surface sublayer of a metal-oxide including chromium, and a third surface sublayer of a silicon compound. Except that the gas flow ratio of silane to argon is about 1 to 11 respectively, a boron dopant gas is added, and the deposition time is 46 minutes, a boron-doped amorphous silicon film with an adhesion of about 12 μm thick is deposited using a method similar to that of the above comparative anode 1, having a density of about 1.7 g / cm 3 .

[0133] Example anode E-3A

[0134] The current collector CC-4A is the same as CC-3A, but 50 nm of TiO2 is deposited by ALD as the topmost surface sublayer. The surface roughness of CC-4A is also comparable to that of CC-3A. Except for a deposition time of 50 minutes, an adhesion boron-doped amorphous silicon film with a thickness of about 14 μm and a density of about 1.7 g / cm 3 is deposited using the same conditions as anode E-2.

[0135] Electrochemical testing - half cell

[0136] Half cells are constructed using a punch with a diameter of 0.80 cm for each anode. Lithium metal is used as the counter electrode and is separated from the test anode using a CelgardTM separator. The electrolyte solution includes: a) 88 wt% of 1.0 M LiPF6 in 3:7 EC:EMC (weight ratio); b) 10 wt% FEC; and 2 wt% VC. The anode first undergoes an electrochemical formation step. As is known in the art, the electrochemical formation step is used to form an initial SEI layer. Relatively mild conditions with low current and / or limited voltage can be used to ensure that the anode is not overly stressed. In this example, the electrochemical formation includes several cycles over a wide voltage range (0.01 or 0.06 to 1.2 V) at a C-rate in the range of C / 20 to C / 10. The total active silicon (mg / cm 2 ) available for reversible lithiation and the total charge capacity (mAh / cm 2 ) are determined from the electrochemical formation step data. Although the theoretical charge capacity of silicon for lithium-ion batteries is about 3600 mAh / g, it has been found that if only a portion of the total capacity is used, the cycle life is significantly improved. For all anodes in test group A, the performance cycle is set to use approximately one-third of the total capacity, i.e., about 1200 mAh / g. The performance cycle scheme includes 3C or 1C charging (considered aggressive in the industry) and C / 3 discharging to a state of charge of approximately 20%. A 10-minute rest is provided between charge and discharge cycles.

[0137] Table 2 summarizes the properties and cycling performance of Example anodes E-1A, E-2A, and E-3A. The Comparative anode C-1A could not be tested because the silicon adhesion was not good enough. In some commercial applications, an anode should have a charge capacity of at least 1.5 mAh / cm 2 and be able to charge at a rate of 1C with a cycle life of at least 100 cycles, which means the charge capacity should not be lower than 80% of the initial charge capacity after 100 cycles. The number of cycles required for the anode to drop below 80% of the initial charge is commonly referred to as its "80% SoH ("State of Health") cycle life". All Example anodes achieved these goals. The boron-doped a-Si in Example anode E-2 can be combined with the surface layer of the present invention to achieve higher charge capacity and life. As shown by Example anode E-3A, the cycle life of Example anode E-2A can be improved by setting a TiO2 sublayer above the silicon compound sublayer. Therefore, when the surface layer includes a metal oxide sublayer, the life can be improved.

[0138] Table 2

[0139] Performance E-1A E-2A E-3A Charge Rate 3C 1C 1C <![CDATA[Active Si (mg / cm 2 )]]> 1.4 1.6 1.7 <![CDATA[Initial charge capacity (mAh / cm 2 )]]> 1.6 2.1 2.0 Number of Cycles to 80% of Initial Charge Capacity 130 151 224

[0140] Test Group B

[0141] Silicon was deposited onto various current collectors using an Oxford Plasmalabs System 100 PECVD tool. Unless otherwise stated, the deposition was carried out at approximately 300 °C with an RF power in the range of approximately 225 to 300 W. The deposition gases were a mixture of silane and argon with a gas flow ratio of approximately 1 to 12, respectively. For most tests, a deposition time of 40 minutes was used to deposit a porous amorphous silicon layer approximately 7 μm thick. For higher loadings, a deposition time of 70 to 75 minutes was used to deposit approximately 11 to 12 μm. For some tests, a sub-stoichiometric silicon nitride coating (SiNx) was prepared. The conditions were similar to those above, except that ammonia was included in the gas flow ratio of silane to ammonia at approximately 2.25 to 1, and a deposition time of 75 minutes was used to produce approximately 11 to 12 μm of SiNx.

[0142] Three starting foils are used to prepare the current collectors. Copper foil A (high purity copper) is 25 μm thick, has a tensile strength of about 275 MPa, and a surface roughness Ra of 167 nm. Copper foil B (rolled C70250 alloy, sometimes called CuNi3Si) is 20 μm thick, has a tensile strength in the range of about 690 to 860 MPa, a yield strength greater than about 655 MPa, and a surface roughness Ra of 280. Nickel foil A (rolled nickel) is 20 μm thick, has a tensile strength in the range of about 680 to 750 MPa, a yield strength greater than about 550 MPa, and a surface roughness Ra of 279.

[0143] Unless otherwise stated, electrodeposition is carried out on the metal foil using an electroplating jig such that only one side of the metal foil is exposed for electrodeposition. The counter electrode is a platinum / niobium mesh spaced 1.9 cm from the metal foil.

[0144] The authors have previously found that the above PECVD conditions are ineffective in depositing commercially available loadings of silicon onto the surface of freshly cleaned copper or nickel foils that do not have a surface layer. The silicon does not adhere and flakes off.

[0145] Compare anode C-1B

[0146] In this test, it was shown that electrodepositing copper roughening features alone is generally not sufficient to improve the adhesion of silicon. Copper foil A was first cleaned in acetone, then sonicated in IPA for 10 minutes, then rinsed with deionized water. The foil was treated with 10% concentrated sulfuric acid for 30 seconds, rinsed in deionized water, and placed in an electroplating jig. The jig was immersed in a 0.01 M CuSO4(aq) bath containing 1 M H2SO4. A current of 100 mA / cm 2 was supplied to the foil for 100 seconds (conditions suitable for depositing copper roughening features), the foil was removed and rinsed in deionized water and air dried. The surface roughness Ra was 246 nm and the surface roughness Rz was 2.3 μm. When silicon was deposited by PECVD as described above, it flaked off easily.

[0147] Compare anode C-2B

[0148] This test is similar to C-1B, except that after deposition of the copper roughening features, the foil is further treated with silicon compound A (3-glycidoxypropyltriethoxysilane). Specifically, the foil is placed in a tray, covered with a solution of 1 mL of silicon compound A in 180 mL of ethanol, and then filled with deionized water to 200 mL. The foil is immersed for 30 seconds and then hung to dry. After drying, the foil is placed in an oven at 140 °C for 30 minutes to dry / cure the silicon compound. The surface roughness Ra is 233 nm and the surface roughness Rz is 2.0 μm. When silicon is deposited by PECVD as described above, it peels off easily. Thus, on newly electrodeposited copper, even with copper roughening features, this silicon compound does not provide an effective surface layer. As shown below, the silicon compound may be effective for chemically roughened copper foils, rather than for electrochemically roughened foils with electrodeposited copper roughening features.

[0149] Example Anode E-1B

[0150] First, copper foil A is cleaned in acetone, then ultrasonically treated in IPA for 10 minutes, and then rinsed with deionized water. The foil is treated with 10% concentrated sulfuric acid for 30 seconds, rinsed in deionized water, and placed in an electroplating fixture. The fixture is immersed in a 0.01 M CuSO4(aq) bath containing 1 M H2SO4. Current is supplied to the foil at 50 mA / cm 2 for 200 seconds (conditions suitable for depositing copper roughening features). Then the fixture is placed in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4 and current is supplied at a current density of 10 mA / cm 2 for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then the fixture is removed and rinsed with deionized water. After rinsing, the fixture is placed in a bath of 0.1 M ZnSO4 and 1 M H2SO4 and current is supplied at a current density of 10 mA / cm 2 for 100 seconds. Thereafter, the fixture is rinsed again with deionized water. Then the fixture is placed in a bath of 4 g / L K2CrO4 (pH ~ 12) and current is supplied at a current density of 10 mA / cm 2 for 40 seconds. Thereafter, the fixture is rinsed again with deionized water and air-dried. The surface roughness Ra of the current collector is 418 nm and the surface roughness Rz is 5.3 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sublayer of zinc and a second surface sublayer of a chromium-containing metal-oxide, such surface sublayers being disposed above the metal foil roughened with electrodeposited copper roughening features.

[0151] Example Anode E-2B

[0152] Example anode E-2B is similar to E-1B, except that after depositing a chromium-containing metal-oxide compound, the foil is further treated with silicon compound A (3-glycidoxypropyltriethoxysilane). Specifically, the foil is placed in a tray, covered with a solution of 1 mL of silicon compound A in 180 mL of ethanol, and then filled with deionized water to 200 mL. The foil is immersed for 30 seconds and then hung to dry. After drying, the foil is placed in an oven at 140 °C for 30 minutes to dry / cure the silicon compound. The surface roughness Ra is 401 nm and the surface roughness Rz is 4.7 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface layer of zinc, a second surface layer of a chromium-containing metal-oxide compound, and a third surface layer of a silicon compound, such surface sub-layers being provided above a metal foil roughened with electrodeposited copper roughening features.

[0153] Example anode E-3B

[0154] First, copper foil A is cleaned in acetone, then ultrasonically treated in IPA for 10 minutes, and then rinsed with deionized water. The foil is treated with 10% concentrated sulfuric acid for 30 seconds, rinsed in deionized water, and placed in a tray in an MSA roughening bath and rotated gently for 10 seconds. The MSA roughening bath consists of 40 g / L H2O2, 100 g / L methanesulfonic acid (MSA), 3 g / L 5-aminotetrazole, and 8 g / L benzotriazole. The foil is removed for a short time, quenched in deionized water, and then immersed in the MSA bath again. A total of six (6) 10-second immersions are carried out, which is sufficient to impart a certain surface roughness. The foil is rinsed with deionized water and air-dried. It is expected that air-drying forms at least a monolayer, perhaps more, of copper oxide. Then the foil is placed in a tray and covered with a mixture of 100 μL of water added to silicon compound A (100 μL) and tetrabutylammonium molybdate (0.0322 g) in 10 mL of dichloromethane. The foil is immersed for 30 seconds and then hung to dry. After drying, the foil is placed in an oven at 140 °C for 30 minutes to dry / cure the silicon compound / molybdate mixture. The surface roughness Ra is 723 nm and the surface roughness Rz is 10.3 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of copper oxide and a second surface sub-layer including a mixture of a transition metalate (molybdate) and a silicon compound, such surface sub-layers being provided above a chemically roughened copper foil.

[0155] Example anode E-4B

[0156] Example anode E-4B is similar to E-3B, except that after the MSA bath treatment, the foil is further treated with silicon compound B (3-aminopropyltriethoxysilane). Specifically, the foil is placed in a tray, covered with a solution of 1 mL of silicon compound B in 180 mL of ethanol, and then filled with deionized water to 200 mL. The foil is immersed for 30 seconds and then hung to dry. After drying, the foil is placed in an oven at 140 °C for 30 minutes to dry / cure the silicon compound. The surface roughness Ra is 902 nm and the surface roughness Rz is 12.5 μm. An adherent layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sublayer of copper oxide and a second surface sublayer with a silicon compound, such surface sublayers being provided above the chemically roughened copper foil.

[0157] Example anode E-5B

[0158] First, copper foil A is cleaned in acetone, then ultrasonically treated in IPA for 10 minutes, and then rinsed with deionized water. The foil is treated with 10% concentrated sulfuric acid for 30 seconds, rinsed in deionized water, and placed in an electroplating jig. The jig is immersed in a bath containing 0.01 M CuSO4(aq) in 1 M H2SO4. A current of 20 mA / cm 2 is supplied to the foil for 500 seconds (conditions suitable for depositing copper roughening features). Then the jig is placed in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4, and a current density of 10 mA / cm 2 is supplied for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then the jig is removed and rinsed with deionized water. After rinsing, the jig is placed in a bath of 0.26 M ZnCl2, 0.13 M NiCl2 and 1 M KCl, the pH is adjusted to about 5, and a current density of 10 mA / cm 2 is supplied for 100 seconds. Thereafter, the jig is rinsed again with deionized water. Then the jig is placed in a bath of 4 g / L K2CrO4 (pH ~ 12), and a current density of 10 mA / cm 2 is supplied for 40 seconds. Thereafter, the jig is rinsed again with deionized water and air-dried. The surface roughness Ra of the current collector is 254 nm and the surface roughness Rz is 2.5 μm. An adherent layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 75 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sublayer of zinc-nickel alloy and a second surface sublayer of chromium-containing metal-oxide, such surface sublayers being provided above the metal foil roughened with electrodeposited copper roughening features. The zinc-nickel alloy includes about 8–9 atomic % nickel.

[0159] Example anode E-6B

[0160] First, clean nickel foil A in acetone, then sonicate it in IPA for 10 minutes, and then rinse it with deionized water. Treat the foil with 10% concentrated sulfuric acid for 30 seconds, rinse it in deionized water, and place it in an electroplating fixture. Immerse the fixture in a bath containing 0.01 M CuSO4(aq) with 1 M H2SO4. Supply current to the foil at 100 mA / cm 2 for 100 seconds (conditions suitable for depositing copper roughening features). Then place the fixture in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4, and supply current at a density of 10 mA / cm 2 for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then remove the fixture and rinse it with deionized water. After rinsing, place the fixture in a bath of 0.1 M ZnSO4 and 1 M H2SO4, and supply current at a density of 10 mA / cm 2 for 100 seconds. After that, rinse the fixture with deionized water again. Then place the fixture in a bath of 4 g / L K2CrO4 (pH ~ 12), and supply current at a density of 10 mA / cm 2 for 40 seconds. After that, rinse the fixture with deionized water again and air-dry it. The surface roughness Ra of the current collector is 464 nm, and the surface roughness Rz is 5.0 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc and a second surface sub-layer of a chromium-containing metal-oxide, and such a surface layer is disposed above the nickel foil roughened with electrodeposited copper roughening features.

[0161] Example Anode E-7B

[0162] Example Anode E-7B is similar to E-6B, except that after depositing the chromium-containing metal-oxide, the foil is further treated with silicon compound A (3-glycidoxypropyltriethoxysilane). Specifically, place the foil in a tray, cover it with a solution of 1 mL of silicon compound A in 180 mL of ethanol, and then fill it with deionized water to 200 mL. Immerse the foil for 30 seconds, and then hang it to dry. After drying, place the foil in an oven at 140 °C for 30 minutes to dry / cure the silicon compound. The surface roughness Ra is 409 nm, and the surface roughness Rz is 4.6 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc, a second surface sub-layer of a chromium-containing metal-oxide, and a third surface layer of a silicon compound, and such a surface layer is disposed above the nickel foil roughened with electrodeposited copper roughening features.

[0163] Example Anode E-8B

[0164] First, clean the copper foil B in acetone, then sonicate it in IPA for 10 minutes, and then rinse it with deionized water. Place the foil in an oven at 180 °C (in air) for 15 hours. Cover the foil with 10% sulfuric acid for 5 minutes to remove at least some of the oxides developed during the oven treatment. Rinse the foil in deionized water and place it in an electroplating jig. Immerse the jig in a bath containing 0.001 M CuSO4(aq) in 1 M H2SO4. Supply a current of 10 mA / cm 2 to the foil for 100 seconds (conditions suitable for depositing copper roughening features). Then place the jig in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4 and supply a current of 10 mA / cm 2 at a current density for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then remove the jig and rinse it with deionized water. After rinsing, place the jig in a bath of 0.1 M ZnSO4 and 1 M H2SO4 and supply a current of 10 mA / cm 2 at a current density for 100 seconds. After that, rinse the jig with deionized water again. Then place the jig in a bath of 4 g / L K2CrO4 (pH ~ 12) and supply a current of 10 mA / cm 2 at a current density for 40 seconds. After that, rinse the jig with deionized water again and air-dry it. The surface roughness Ra of the current collector is 453 nm, and the surface roughness Rz is 5.2 μm. An amorphous silicon adhesion layer (continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sublayer of zinc and a second surface sublayer of a chromium-containing metal-oxide, such surface sublayers being provided above a nickel foil roughened with electrodeposited copper roughening features.

[0165] Example Anode E-9B

[0166] First, clean copper foil B in acetone, then sonicate it in IPA for 10 minutes, and then rinse it with deionized water. Place the foil in an oven at 180 °C (in air) for 15 hours. Cover the foil with 10% sulfuric acid for 5 minutes to remove at least some of the oxides developed during the oven treatment. Rinse the foil in deionized water and place it in a tray, and gently rotate it in a peroxide / HCl solution (10 mL 30% H2O2, 240 mL deionized water, 50 mL concentrated HCl) for 30 seconds. Rinse the foil with deionized water and air-dry it. It is expected that air-drying forms at least a single layer, perhaps more, of copper oxide. Further treat the foil with silicon compound A (3-glycidoxypropyltriethoxysilane). In particular, place the foil in a tray, cover it with a solution of 1 mL silicon compound A in 180 mL ethanol, and then fill it with deionized water to 200 mL. Immerse the foil for 30 seconds and then hang it to dry. After drying, place the foil in an oven at 140 °C for 30 minutes to dry / cure the silicon compound. The surface roughness Ra is 591 nm and the surface roughness Rz is 11.4 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of copper oxide and a second surface sub-layer with a silicon compound, and such surface sub-layers are disposed above the chemically roughened copper foil.

[0167] Example Anode E-10B

[0168] First, clean copper foil B in acetone, then sonicate it in IPA for 10 minutes, and then rinse it with deionized water. Place the foil in an oven at 180 °C (in air) for 20 minutes. Cover the foil with 10% sulfuric acid for 30 minutes, rinse it in deionized water, and place it in an electroplating jig. Immerse the jig in a bath containing 0.01 M CuSO4(aq) with 1 M H2SO4. Current is supplied to the foil at 20 mA / cm 2 for 500 seconds (conditions suitable for depositing copper roughening features). Then place the jig in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4 and supply current at a density of 10 mA / cm 2 for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then remove the jig and rinse it with deionized water. After rinsing, place the jig in a bath of 0.26 M ZnCl2, 0.13 M NiCl2, and 1 M KCl, adjust the pH to about 5, and supply current at a density of 10 mA / cm 2 for 100 seconds. Thereafter, rinse the jig with deionized water again. Then place the jig in a bath of 4 g / L K2CrO4 (pH ~ 12) and supply current at a density of 10 mA / cm 2A current density is supplied for 40 seconds. Thereafter, the fixture is rinsed again with deionized water and air-dried. The surface roughness is not optically measurable. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 70 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc-nickel alloy and a second surface sub-layer of a chromium-containing metal-oxide, such surface sub-layers being provided above a metal foil roughened with electrodeposited copper roughening features. The zinc-nickel alloy includes about 8–9 atomic % nickel.

[0169] Example anode E-11B

[0170] First, copper foil B is cleaned in acetone, then ultrasonically treated in IPA for 10 minutes, and then rinsed with deionized water. The foil is placed in an oven at 180 °C (in air) for 20 minutes. The foil is covered with 10% sulfuric acid for 30 minutes, rinsed in deionized water, and placed in an electroplating fixture. The fixture is immersed in a bath containing 0.01 M CuSO4(aq) in 1 M H2SO4. A current is supplied to the foil at 50 mA / cm 2 for 200 seconds (conditions suitable for depositing copper roughening features). Then the fixture is placed in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4, and a current is supplied at 10 mA / cm 2 for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then the fixture is removed and rinsed with deionized water. After rinsing, the fixture is placed in a bath of 0.1 M ZnSO4 and 1 M H2SO4, and a current is supplied at 10 mA / cm 2 for 100 seconds. Thereafter, the fixture is rinsed again with deionized water. Then the fixture is placed in a bath of 4 g / L K2CrO4 (pH ~ 12), and a current is supplied at 10 mA / cm 2 for 40 seconds. The fixture is rinsed again with deionized water and air-dried. The surface roughness Ra is 418 nm and the surface roughness Rz is 5.3 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 70 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc and a second surface sub-layer of a chromium-containing metal-oxide, such surface sub-layers being provided above a metal foil roughened with electrodeposited copper roughening features.

[0171] Example anode E-12B

[0172] Example anode E-12B is similar to E-11B, except that after depositing a chromium-containing metal-oxide compound, the foil is further treated with silicon compound A (3-glycidoxypropyltriethoxysilane). Specifically, the foil is placed in a tray, covered with a solution of 1 mL of silicon compound A in 180 mL of ethanol, and then filled with deionized water to 200 mL. The foil is immersed for 30 seconds and then hung to dry. After drying, the foil is placed in an oven at 140 °C for 30 minutes to dry / cure the silicon compound. The surface roughness Ra is 344 nm and the surface roughness Rz is 3.9 μm. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface layer of zinc, a second surface layer of a chromium-containing metal-oxide compound, and a third surface layer of a silicon compound, such surface sub-layers being provided above a metal foil roughened with electrodeposited copper roughening features.

[0173] Example anode E-13B

[0174] The current collector sample CC-1B is a commercially available copper foil 18 μm thick, with a surface roughness Ra = 508 nm and Rz = 5.2 μm. Based on product literature and analytical data, it is believed that CC-1B includes the surface layer of the present disclosure, which has a first surface sub-layer of zinc and a second surface sub-layer of a metal-oxide compound including chromium. As will be shown later with some SEM, the surface has a certain roughness, but CC-1B generally does not include electrodeposited roughening features. An adhesion layer of amorphous silicon (a continuous porous lithium storage layer) is deposited by PECVD for 40 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc and a second surface sub-layer of a chromium-containing metal-oxide compound, such surface sub-layers being provided above a rough copper foil without electrodeposited copper roughening features.

[0175] Example anode E-14B

[0176] First, copper foil A is cleaned in acetone, then ultrasonically treated in IPA for 10 minutes, and then rinsed with deionized water. The foil is treated with 10% concentrated sulfuric acid for 30 seconds, rinsed in deionized water, and placed in an electroplating jig. The jig is immersed in a bath containing 0.01 M CuSO4(aq) in 1 M H2SO4. The current is supplied to the foil at 20 mA / cm 2 for 500 seconds (conditions suitable for depositing copper roughening features). Then the jig is placed in a bath of 0.4 M CuSO4(aq) and 1 M H2SO4, and at 10 mA / cm 2The current density is supplied for 100 seconds. This second copper deposition covers the copper roughening features and can help anchor them to the foil. Then the fixture is removed and rinsed with deionized water. After rinsing, the fixture is placed in a bath of 0.26 M ZnCl2, 0.13 M NiCl2, and 1 M KCl, with the pH adjusted to approximately 5, and a current density of 10 mA / cm 2 is supplied for 100 seconds. Thereafter, the fixture is rinsed again with deionized water. Then the fixture is placed in a bath of 4 g / L K2CrO4 (pH ~ 12), and a current density of 10 mA / cm 2 is supplied for 40 seconds. Thereafter, the fixture is rinsed again with deionized water and air-dried. The surface roughness Ra of the current collector is 254 nm, and the surface roughness Rz is 2.5 μm. The sub-stoichiometric silicon nitride adhesion layer (continuous porous lithium storage layer) is deposited by PECVD for 70 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc-nickel alloy and a second surface sub-layer of chromium-containing metal-oxide, such surface sub-layers being disposed above the metal foil roughened with electrodeposited copper roughening features. The zinc-nickel alloy includes approximately 8–9 atomic % nickel.

[0177] Example anode E-15B

[0178] Example anode E-16B is the same as E-14B except that the sub-stoichiometric silicon nitride (continuous porous lithium storage layer) is deposited by PECVD for 70 minutes under the above conditions. The surface layer of this example can be characterized as including a first surface sub-layer of zinc and a second surface sub-layer of chromium-containing metal-oxide, such surface sub-layers being disposed above the rough copper foil without electrodeposited copper roughening features.

[0179] Example anode

[0180] The current collector sample CC-2B is a commercially available 18-μm thick copper foil with a surface roughness Ra = 580 nm and Rz = 6.0 μm. Based on product literature and analytical data, it is believed that CC-2B includes a first surface sub-layer of zinc, a second surface sub-layer of chromium-containing metal-oxide, and a third surface sub-layer of silicon compound. The chemical structure of the silicon compound is unknown ("Si cpd X"). The amorphous silicon layer (continuous porous lithium storage layer) is deposited by PECVD for 65 minutes under the above conditions. In electrochemical tests (see below and Table 3), although this anode has very good capacity, the cycle life is generally not as good as that of other examples.

[0181] SEM analysis

[0182] Figures 8–11 show the topologies of the various current collectors described above. The current collector from Example E-14B is representative of current collectors with electrodeposited copper roughening features. Figure 8AShows a top view, Figure 8B is a cross-sectional view. These roughening features can be characterized as nanocolumn features as described above. These features are very dense, relatively small, mostly at 60 to 90 degrees relative to the foil, where relatively few of them have a significantly wider "top" than their bottom. Most of these features can be characterized as type-I nanocolumn features. Figure 8C Shows Example Anode E-14B. As can be seen, the electrodeposited copper roughening features (nanocolumn features) can have a suitable geometry to generally embed in the SiNx layer. This can contribute to the adhesion of the continuous porous lithium storage layer. This current collector surface structure can create some void space at the current collector-SiNx interface. This can allow additional space for silicon expansion during the lithiation cycle and reduce structural degradation. Although not shown here, similar images were observed using amorphous silicon instead of SiNx.

[0183] In Figure 9 the current collector of Example E-16B (CC-2B) is shown in cross-section. Although there are many features similar to Figure 8B , there are many features where their top is significantly wider than their bottom (type-II nanocolumns, circled in the figure). As described above, the electrochemical performance of anodes using this current collector can be acceptable, but such anodes are generally not as good as other anodes of the present disclosure. The reason is not fully clear, but it has also been found that other current collectors with similar physical properties (wide "tops") do not perform well. Without being bound by theory, it may be that the wide tops prevent the roughening features from embedding in the silicon. Alternatively, these structures may be structurally fragile and may break at the bottom. In any case, in some embodiments, current collectors with too many such structures may not perform well with PECVD-deposited lithium storage materials.

[0184] The current collectors of Examples E-14B and E-16B are shown in FIG. 10. Figure 10A is a 45-degree view of the surface, Figure 10B is a cross-sectional view. There is obvious roughness, but no fine roughening features such as nanocolumns, etc. The current collector can be considered a representative example of a current collector with broad roughening features characterized by protrusions and hills, as discussed previously. Figure 10C is a cross-section further showing the profile of Example Anode E-16B. Different from Example E-14B ( Figure 8C ), this current collector does not seem to create void space at the interface with the continuous porous lithium storage layer of SiNx.

[0185] In Figure 11The current collector E-3B of the embodiment is shown in a 45-degree perspective view. The chemically roughened (etched) current collectors look very different from other current collectors. In some cases, they can be characterized as having indentations or pits that produce significant roughness. These indentations and associated structures can form strong anchors for a continuous porous lithium storage layer.

[0186] Electrochemical testing - half cells

[0187] Half cells were constructed using a punch with a diameter of 0.80 cm for each anode. Lithium metal was used as the counter electrode, and Celgard TM separator was used to separate it from the test anode. The standard electrolyte solution ("standard") includes: a) 88 wt% of 1.2 M LiPF6 in 3:7 EC:EMC (weight ratio); b) 10 wt% FEC; and 2 wt% VC. Some tests were conducted using a commercially available electrolyte that was very similar to the standard, except that more than one additive (supplier proprietary) was used. The anode first undergoes an electrochemical formation step. As is known in the art, the electrochemical formation step is used to form an initial SEI layer. Relatively mild conditions with low current and / or limited voltage can be used to ensure that the anode is not overly stressed. In this embodiment, the electrochemical formation includes several cycles over a wide voltage range (0.01 or 0.06 to 1.2 V) within a C-rate range of C / 20 to C / 10. The total active silicon (mg / cm 2 ) available for reversible lithiation and the total charge capacity (mAh / cm 2 ) were determined from the electrochemical formation step data. The formation loss was calculated by dividing the change in the charge capacity of the active area (initial first charge capacity minus the final formation discharge capacity) by the initial area first charge capacity. Although the theoretical charge capacity of silicon when used in lithium-ion batteries is approximately 3600 mAh / g, it has been found that the cycle life can be improved if only a portion of the total capacity is used. For all anodes, the performance cycle is set to use a portion of the total capacity, typically in the range of 950 - 1700 mAh / g. The performance cycle scheme includes a 3.2C or 1C charge (considered aggressive in the industry) and a C / 3 discharge to approximately 15% state of charge. A 10-minute rest is provided between charge and discharge cycles.

[0188] Table 3 summarizes the properties and cycle performance of the comparative anodes and the embodiment anodes from test group B. Note that the surface sublayer with chromium-containing metal-oxide is simply labeled "CrOx", and the copper oxide surface sublayer is simply labeled "CuOx". The comparative anodes C-1 or C-2 could not be tested because the silicon did not adhere well enough. The comparative anode C-3B failed during the electrochemical formation and therefore did not cycle.

[0189] For some commercial applications, the anode should have a charge capacity of at least 1.5 mAh / cm 2 and be able to charge at a rate of 1C with a cycle life of at least 100 cycles, meaning that after 100 cycles, the charge capacity should not be less than 80% of the initial charge capacity. The number of cycles required for the anode to drop below 80% of the initial charge is commonly referred to as its "80% SoH ("State of Health") cycle life". All example anodes achieved these goals. One sample (E-1B) cycled >1000 times and was still cycling before being removed from the test cycler. Several others had reached >500 cycles and some were still cycling. It was also noted that all a-Si samples had very low formation losses. High formation losses are often observed to be an indicator of an unstable anode (although there may be exceptions to this rule). Generally, a formation loss of less than 15% is considered very good and may sometimes be an indicator of a stable a-Si anode.

[0190] For surface layers including zinc and chromium-containing metal-oxide sublayers, it appears that the anode can perform better without an additional silicon compound sublayer (E-1B vs E-2B, E-6B vs E-7B, and E-18B vs E-12B). Such anodes with a silicon compound (third surface sublayer) can have good performance regarding cycle life but are generally not as good as anodes using a current collector without a silicon compound layer. Although coating the battery foil with a silicon compound may be common for traditional slurry-based anodes, in some cases, anodes based on PECVD-deposited lithium storage layers are advantageous when there is no third surface sublayer of silicon compound.

[0191] It has generally been observed that using a zinc-nickel alloy as the first surface sublayer (with a chromium-containing metal-oxide as the second surface sublayer) can provide more reliable performance at higher silicon loadings and / or higher charge rates compared to similar anodes using pure zinc or near-pure zinc instead of an alloy (e.g., E-IOB vs E-11B). However, as can be seen, there are many examples of batteries using pure zinc or near-pure zinc that perform excellently.

[0192] Generally, when the current collector roughening treatment includes electrodeposited copper roughening features (e.g., the nanocolumnar structure discussed above), anodes with a zinc-based first surface sublayer and a chromium-containing metal-oxide as the second surface sublayer have the best performance compared to roughening structures with wider or less fine structures (e.g., bumps and hills) – E-8B vs E-13B or E-14B vs E15B.

[0193] For SiNx samples, due to nitrogen doping, there is a large loss during formation. However, despite this, anodes using SiNx have been successfully fabricated with a very high charge capacity (3 mAh / cm 2 ), a high cycle life (up to 518 cycles), and a fast 1C charge rate. In some embodiments, SiNx-based anodes can exhibit less swelling than a-Si-based anodes.

[0194] For chemically roughened samples, it has been found that a simple silicon compound layer (generally having at least a monolayer of surface copper oxide material) over copper is usually sufficient to provide a well-performing anode. These samples (E-3B, E-4B, E-9B) do not require an electrochemical step and may thus be easier to fabricate. In some cases, adding a metal-oxide compound (e.g., a metal oxalate, such as molybdate) (E-3B) to the silicon compound can provide additional cycle life benefits.

[0195] In some embodiments, the anodes of the present disclosure can provide a charge capacity of at least 1.6 mAh / cm at a charge rate of at least 1C and a discharge rate of at least C / 3 for at least 150 cycles of 80% SoH cycle life. In some embodiments, when tested at 1C charge and C / 3 discharge at 1.7 mAh / cm 2 , the anodes of the present disclosure can have a cycle life of at least 300 cycles, optionally at least 400, 500, 600, 700, 800, 900, or 1000 cycles. In some embodiments, the anodes of the present disclosure can be capable of providing a charge capacity of 3 mAh / cm at 1C charge and C / 3 discharge and having an 80% SoH cycle life of at least 150 cycles, optionally at least 300 cycles, or at least 500 cycles. In some embodiments, the anodes of the present disclosure can be capable of charging at 3C with a charge capacity of 2 mAh / cm 2 and an 80% SoH cycle life of at least 400 cycles. 2 2

[0196] Table 3

[0197]

[0198] 1 = Electroplated copper roughened features (e.g., nanocolumns); 2 = Chemically roughened (e.g., indentations); 3 = Wide roughness features (e.g., protrusions / hills); 4 = Wide-top roughened features

[0199] * Still cycling

[0200] ^ Using commercially available electrolyte

[0201] ​​It should be noted that the anode using copper foil A is prone to deformation during cycling even though the battery is generally stable during cycling. For example, under these silicon loadings, wrinkles in the foil are often noticed upon disassembly. It is likely that the expansion and contraction of silicon under these high loadings exert stress on copper foil A, causing these deformations. Copper foil A has a relatively low tensile strength. Surprisingly, despite the deformation, the anode performs well during cycling. However, in some battery applications, such deformation can be problematic. It was found that embodiments using high-tensile copper foil B or nickel foil A do not have such deformation, or the problem is greatly reduced.

[0202] Test Group C

[0203] Example E-1C

[0204] In this test, the prelithiated anode was tested in a full-cell format. Specifically, the same anode as described in Example E-15B was used. Before full-cell assembly, the anode similar to that described in Example E-15B was constructed into a half coin cell together with lithium metal as the counter electrode, Celgard TM separator and a commercial electrolyte. Then the anode was electrochemically charged (prelithiated) to about 2.2 mAh / cm 2 . The amount of prelithiation was determined by adding the anode formation loss (previously determined by half-cell formation tests) and the desired anode lithium inventory (about 15%), and then subtracting the expected permanent loss of the cathode to be paired with the prelithiated anode. After prelithiation, the anode was removed from the half-cell and reassembled into a full coin cell together with an NMC-based cathode (rated at about 4 mAh / cm 2 ), as well as a new separator and electrolyte (commercial).

[0205] The newly constructed cell was allowed to stand for 16 hours and then electrochemically formed at a slow cycling rate of about 2.5 to 4.2 V. The cell was rated at an initial charge capacity of about 3 mAh / cm 2 , and then cycled at 1C (to 4.05 V, current cutoff at C / 20), followed by a 10-minute rest, and then discharged at C / 3 to 2.8 V, followed by a 10-minute rest. At the time of writing, full-cell Example E-1C has received 233 cycles, and the initial charge capacity of 3.27 mAh / cm 2 has dropped to only 2.93 mAh / cm 2 (~90% SoH).

[0206] Example E-1C shows that the strong cycling performance of the anodes of the present invention is not limited to only the half-cell format. In addition, Example E-1C illustrates that the anodes of the present invention can be successfully prelithiated.

[0207] In some embodiments, the current collectors of the present disclosure can be used with a PECVD deposition method that can deposit a lithium storage layer having at least 40 atomic percent of silicon, germanium, or a combination thereof, where such a lithium storage layer can be characterized as being different from a continuous porous lithium storage layer. In some embodiments, the current collectors of the present disclosure can be used with a coatable lithium storage material, for example, those materials that include a carbon-based binder and silicon-containing particles. In some embodiments, the current collectors of the present disclosure can be used with a sputter-deposited lithium storage material such as sputter-deposited silicon. In some embodiments, the current collectors of the present disclosure can be used with a substantially pore-free silicon such as crystalline silicon, polycrystalline silicon, or high-density amorphous silicon (e.g., having a density higher than 2.95 g / cm 3 ).

[0208] Although the anodes of the present invention have been discussed with reference to batteries, in some embodiments, the anodes of the present invention can be used in hybrid lithium-ion capacitor devices.

[0209] Further embodiments herein include the embodiments listed below.

[0210] 1. An anode for an energy storage device, the anode comprising:

[0211] a) A current collector comprising a conductive layer and a surface layer disposed above the conductive layer, the surface layer comprising a first surface sublayer adjacent to the conductive layer and a second surface sublayer disposed above the first surface sublayer,

[0212] wherein:

[0213] (i) The first surface sublayer comprises zinc,

[0214] (ii) The second surface sublayer comprises a metal-oxide compound, wherein the metal-oxide compound comprises a transition metal other than zinc, and

[0215] (iii) The current collector is characterized by a surface roughness Ra≥250 nm; and

[0216] b) A continuous porous lithium storage layer covering the surface layer, wherein the continuous porous lithium storage layer:

[0217] (i) Has an average thickness of at least 7 μm,

[0218] (ii) Contains at least 40 atomic percent of silicon, germanium, or a combination thereof, and

[0219] (iii) Is substantially free of a carbon-based binder.

[0220] 2. The anode according to embodiment 1, wherein the surface layer further comprises a third surface sublayer disposed above the second surface sublayer, the third surface sublayer comprising a silicon compound.

[0221] 3. The anode according to embodiment 2, wherein the silicon compound comprises a siloxane, a siloxysilane or a silazane, or is derived from a siloxane, a siloxysilane or a silazane.

[0222] 4. The anode according to embodiment 2 or 3, wherein the surface layer further comprises a fourth surface sublayer disposed above the third surface sublayer, and the fourth surface sublayer comprises a metal oxide.

[0223] 5. The anode according to embodiment 4, wherein the metal oxide is a transition metal oxide.

[0224] 6. The anode according to embodiment 4, wherein the metal oxide comprises oxides of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium or niobium.

[0225] 7. The anode according to embodiment 1, wherein the surface layer does not comprise a silicon compound.

[0226] 8. The anode according to embodiment 1 or 7, wherein the surface layer further comprises a third surface sublayer disposed above the second surface sublayer, and the third surface sublayer comprises a metal oxide.

[0227] 9. The anode according to embodiment 8, wherein the metal oxide is a transition metal oxide.

[0228] 10. The anode according to embodiment 8, wherein the metal oxide comprises oxides of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium or niobium.

[0229] 11. The anode according to any one of embodiments 1–10, wherein the first surface sublayer comprises at least 98 atomic % of zinc relative to all metal atoms in the first surface sublayer.

[0230] 12. The anode according to any one of embodiments 1–10, wherein the first surface sublayer comprises a zinc alloy.

[0231] 13. The anode according to embodiment 12, wherein the first surface sublayer comprises less than 98 atomic % of zinc relative to all metal atoms in the first surface sublayer.

[0232] 14. The anode according to embodiment 12 or 13, wherein the zinc alloy comprises zinc and nickel.

[0233] 15. The anode according to embodiment 14, wherein the first surface sublayer comprises 3 to 30 atomic % of nickel.

[0234] 16. The anode according to any one of embodiments 1–15, wherein the first surface sublayer comprises from 10 to 3000 mg / m2 Zinc within the range.

[0235] 17. The anode according to embodiment 11, wherein the first surface sub-layer comprises zinc within the range of 10 to 100 mg / m 2 Zinc within the range.

[0236] 18. The anode according to any one of embodiments 12 - 15, wherein the first surface sub-layer comprises zinc within the range of 500 to 3000 mg / m 2 Zinc within the range.

[0237] 19. The anode according to any one of embodiments 1 - 18, wherein the metal - oxide compound comprises a metal oxide.

[0238] 20. The anode according to any one of embodiments 1 - 19, wherein the metal - oxide compound comprises a metal oxalate.

[0239] 21. The anode according to any one of embodiments 1 - 20, wherein the transition metal of the metal - oxide compound comprises titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium or niobium.

[0240] 22. The anode according to any one of embodiments 1 - 20, wherein the transition metal of the metal - oxide compound comprises chromium.

[0241] 23. The anode according to embodiment 22, wherein the second surface sub-layer comprises chromium within the range of 2 to 50 mg / m 2 Chromium within the range.

[0242] 24. The anode according to any one of embodiments 1 - 23, wherein the current collector further comprises a plurality of nano - pillar features disposed above the conductive layer, wherein each of the plurality of nano - pillar features comprises a copper - containing nano - pillar core, and the surface layer is at least partially located above the copper - containing nano - pillar core.

[0243] 25. The anode according to embodiment 24, wherein each of the nano - pillar features is characterized by a height H, a bottom width B and a maximum width W, and

[0244] wherein a 20 - μm long cross - section of the current collector comprises:

[0245] (i) At least five first - type nano - pillars, each first - type nano - pillar being characterized by

[0246] A) H within the range of 0.4 μm to 3.0 μm,

[0247] B) B within the range of 0.2 μm to 1.0 μm,

[0248] C) The W / B ratio within the range of 1 to 1.5,

[0249] D) The H / B aspect ratio is in the range of 0.8 to 4.0, and

[0250] E) The angle of the longitudinal axis with respect to the plane of the conductive layer is in the range of 60° to 90°; and

[0251] (ii) fewer than four type-II nanocolumns, each type-II nanocolumn being characterized by

[0252] A) H is at least 1.0 μm, and

[0253] B) The W / B ratio is greater than 1.5.

[0254] 26. The anode according to embodiment 24 or 25, wherein the continuous porous lithium storage layer includes voids within 5 μm of the interface with the nanocolumn features.

[0255] 27. The anode according to any one of embodiments 1–27, wherein the conductive layer comprises nickel in a nickel layer.

[0256] 28. The anode according to embodiment 27, wherein the conductive layer further comprises a metal interlayer between the nickel layer and the surface layer.

[0257] 29. The anode according to embodiment 28, wherein the metal interlayer comprises copper.

[0258] 30. The anode according to embodiment 28 or 29, wherein the average interlayer thickness of the metal interlayer is less than 50% of the total average thickness of the conductive layer.

[0259] 31. The anode according to any one of embodiments 1–26, wherein the conductive layer comprises copper.

[0260] 32. The anode according to embodiment 31, wherein the conductive layer comprises a copper alloy comprising copper, magnesium, silver, and phosphorus.

[0261] 33. The anode according to embodiment 31, wherein the conductive layer comprises a copper alloy comprising copper, iron, and phosphorus.

[0262] 34. The anode according to embodiment 31, wherein the conductive layer comprises a copper alloy comprising brass or bronze.

[0263] 35. The anode according to embodiment 31, wherein the conductive layer comprises a copper alloy comprising copper, nickel, and silicon.

[0264] 36. The anode according to any one of embodiments 1–35, wherein the conductive layer comprises a network of conductive carbon.

[0265] 37. The anode according to any one of embodiments 1–36, wherein the current collector further comprises an insulating substrate, and the conductive layer covers the insulating substrate.

[0266] 38. An anode according to any one of embodiments 1–37, wherein the conductive layer or current collector is characterized by a tensile strength of at least 500 MPa.

[0267] 39. An anode according to any one of embodiments 1–37, wherein the conductive layer or current collector is characterized by a tensile strength greater than 600 MPa.

[0268] 40. An anode according to any one of embodiments 1–37, wherein the conductive layer or current collector is characterized by a tensile strength of at least 700 MPa.

[0269] 41. An anode according to any one of embodiments 1–40, wherein the conductive layer comprises a roll-formed metal foil.

[0270] 42. An anode for an energy storage device, the anode comprising:

[0271] a) A current collector comprising a conductive layer and a surface layer disposed above the conductive layer, the surface layer comprising a first surface sublayer and a second surface sublayer disposed above the first surface sublayer,

[0272] wherein:

[0273] (i) The first surface sublayer comprises a metal oxide,

[0274] (ii) The second surface sublayer comprises a silicon compound, wherein the silicon compound comprises a siloxane, a siloxysilane or a silazane, or is derived from a siloxane, a siloxysilane or a silazane, and

[0275] (iii) The current collector is characterized by a surface roughness Ra≥400 nm; and

[0276] b) A continuous porous lithium storage layer covering the surface layer, wherein the continuous porous lithium storage layer:

[0277] (i) Has an average thickness of at least 7 μm,

[0278] (ii) Contains at least 40 atomic % of silicon, germanium or a combination thereof, and

[0279] (iii) Is substantially free of a carbon-based binder.

[0280] 43. An anode according to embodiment 42, wherein the metal oxide comprises a transition metal.

[0281] 44. An anode according to embodiment 42, wherein the metal oxide comprises an oxide of one of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium or niobium.

[0282] 45. The anode according to embodiment 42, wherein the metal oxide comprises at least a single layer of copper oxide.

[0283] 46. The anode according to embodiment 42, wherein the second surface sublayer contains 1 to 100 mg / m 2 of silicon from a silicon compound.

[0284] 47. The anode according to any one of embodiments 42–46, wherein the second surface sublayer further comprises a metal-oxide compound, wherein the metal-oxide compound comprises a transition metal other than copper.

[0285] 48. The anode according to embodiment 47, wherein the metal-oxide compound comprises a metal oxide.

[0286] 49. The anode according to embodiment 47 or 48, wherein the metal-oxide compound comprises a metal oxalate.

[0287] 50. The anode according to any one of embodiments 47–49, wherein the transition metal of the metal-oxide compound comprises titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium or niobium.

[0288] 51. The anode according to any one of embodiments 47–50, wherein the transition metal of the metal-oxide compound comprises molybdenum.

[0289] 52. The anode according to any one of embodiments 42–51, wherein the conductive layer comprises nickel in a nickel layer.

[0290] 53. The anode according to embodiment 52, wherein the conductive layer further comprises a metal interlayer between the nickel layer and the surface layer.

[0291] 54. The anode according to embodiment 53, wherein the metal interlayer comprises copper.

[0292] 55. The anode according to embodiment 52 or 53, wherein the average interlayer thickness of the metal interlayer is less than 50% of the total average thickness of the conductive layer.

[0293] 56. The anode according to any one of embodiments 42–51, wherein the conductive layer comprises copper.

[0294] 57. The anode according to embodiment 56, wherein the conductive layer comprises a copper alloy comprising copper, magnesium, silver and phosphorus.

[0295] 58. The anode according to embodiment 56, wherein the conductive layer comprises a copper alloy comprising copper, iron and phosphorus.

[0296] 59. The anode according to embodiment 56, wherein the conductive layer comprises a copper alloy comprising brass or bronze.

[0297] 60. The anode according to embodiment 56, wherein the conductive layer comprises a copper alloy comprising copper, nickel and silicon.

[0298] 61. The anode according to any one of embodiments 42–60, wherein the conductive layer comprises a network of conductive carbon.

[0299] 62. The anode according to any one of embodiments 42–61, wherein the current collector further comprises an insulating substrate, and the conductive layer covers the insulating substrate.

[0300] 63. The anode according to any one of embodiments 42–62, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 500 MPa.

[0301] 64. The anode according to any one of embodiments 42–62, wherein the conductive layer or the current collector is characterized by a tensile strength greater than 600 MPa.

[0302] 65. The anode according to any one of embodiments 42–62, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 700 MPa.

[0303] 66. The anode according to any one of embodiments 42–65, wherein the conductive layer comprises a roll-formed metal foil.

[0304] 67. The anode according to any one of embodiments 42–66, wherein the silicon compound comprises or is derived from a compound according to formula (1)

[0305] Si(R) n (OR’) 4-n (1)

[0306] wherein n = 1, 2 or 3, and R and R’ are independently selected from substituted or unsubstituted alkyl, alkenyl or aryl.

[0307] 68. An anode for an energy storage device, the anode comprising:

[0308] a) a current collector comprising a conductive layer and a surface layer disposed above the conductive layer, the surface layer comprising at least a metal-oxide containing a transition metal,

[0309] wherein:

[0310] (i) the surface layer further comprises a silicon compound, zinc or both a silicon compound and zinc,

[0311] (ii) when the surface layer comprises zinc, the metal-oxide comprises a transition metal other than zinc, and

[0312] (iii) the current collector is characterized by a surface roughness Ra≥250 nm; and

[0313] b) A continuous porous lithium storage layer covering the surface layer, wherein the continuous porous lithium storage layer:

[0314] (i) has an average thickness of at least 7 μm,

[0315] (ii) contains at least 40 atomic % of silicon, germanium or a combination thereof, and

[0316] (iii) is substantially free of carbon-based binders.

[0317] 69. The anode according to embodiment 68, wherein the surface layer comprises a mixture of a silicon compound and a metal-oxide compound.

[0318] 70. The anode according to embodiment 68, wherein the surface layer comprises a first surface sub-layer adjacent to the conductive layer and a second surface sub-layer disposed above the first surface sub-layer.

[0319] 71. The anode according to embodiment 70, wherein the first surface sub-layer comprises zinc and the second surface sub-layer comprises a metal-oxide compound.

[0320] 72. The anode according to embodiment 71, wherein the second surface sub-layer further comprises a silicon compound.

[0321] 73. The anode according to embodiment 71, wherein the surface layer further comprises a third surface sub-layer disposed above the second surface sub-layer, and the third surface sub-layer comprises a silicon compound.

[0322] 74. The anode according to embodiment 70, wherein the first surface sub-layer comprises a metal-oxide compound and the second surface sub-layer comprises a silicon compound.

[0323] 75. The anode according to embodiment 74, wherein the metal-oxide compound comprises a transition metal oxide.

[0324] 76. The anode according to embodiment 75, wherein the metal-oxide compound comprises at least a single layer of copper oxide.

[0325] 77. The anode according to any one of embodiments 68–76, wherein the silicon compound comprises a siloxane, a siloxysilane or a silazane, or is derived from a siloxane, a siloxysilane or a silazane.

[0326] 78. The anode according to any one of embodiments 1–77, further comprising one or more supplementary layers covering the continuous porous lithium storage layer.

[0327] 79. The anode according to any one of embodiments 1–78, wherein the continuous porous lithium storage layer is substantially free of lithium storage nanostructures.

[0328] 80. The anode according to any one of embodiments 1 - 79, wherein the continuous porous lithium storage layer comprises sub-stoichiometric silicon nitride.

[0329] 81. The anode according to any one of embodiments 1 - 79, wherein the continuous porous lithium storage layer comprises at least 80 atomic % amorphous silicon.

[0330] 82. The anode according to embodiment 81, wherein the density of the continuous porous lithium storage layer is in the range of 1.1 to 2.25 g / cm 3 range.

[0331] 83. The anode according to any one of embodiments 1 - 82, wherein the continuous porous lithium storage layer has an average thickness of at least 10 μm.

[0332] 84. A lithium-ion battery comprising an anode and a cathode according to any one of embodiments 1 - 83.

[0333] 85. The lithium-ion battery according to embodiment 84, wherein the anode is pre-lithiated.

[0334] 86. The lithium-ion battery according to embodiment 84 or 85, wherein the battery is characterized in operation by an initial charge capacity of at least 1.6 mAh / cm 2 and a cycle life of 80% SoH for at least 150 cycles at a charge rate of at least 1C and a discharge rate of at least C / 3.

[0335] 87. The lithium-ion battery according to embodiment 86, wherein the cycle life is at least 500 cycles.

[0336] 88. The lithium-ion battery according to embodiment 87, wherein the initial charge capacity is at least 3.0 mAh / cm 2 .

[0337] 89. The lithium-ion battery according to embodiment 86, wherein the charge rate is at least 3C and the cycle life is at least 400 cycles.

[0338] 90. The lithium-ion battery according to embodiment 89, wherein the initial charge capacity is at least 2.0 mA / cm 2 .

[0339] 91. The lithium-ion battery according to embodiment 90, wherein the cycle life is at least 500 cycles.

[0340] 92. The lithium-ion battery according to any one of embodiments 84 - 91, wherein the cathode comprises nickel, manganese, and cobalt.

[0341] 93. The lithium-ion battery according to any one of embodiments 84 - 91, wherein the cathode comprises sulfur, selenium, or both sulfur and selenium.

[0342] 94. A lithium-ion battery, comprising an anode and a cathode, wherein the anode is prepared by subjecting a non-cycled anode to at least one electrochemical charge / discharge cycle, and the non-cycled anode comprises an anode according to any one of embodiments 1–83.

[0343] 95. A current collector for an anode of a lithium-ion storage device, the current collector comprising:

[0344] a) a conductive layer; and

[0345] b) a plurality of nanocolumn features disposed above the conductive layer, each of the nanocolumn features being characterized by a height H, a bottom width b, and a maximum width W, wherein each of the plurality of nanocolumn features comprises a copper-containing nanocolumn core, and a surface layer is at least partially disposed above the copper-containing nanocolumn core,

[0346] wherein a 20-μm long average cross-section of the current collector comprises:

[0347] (i) at least five first-type nanocolumns, each first-type nanocolumn being characterized by:

[0348] A) H is in the range of 0.4 μm to 3.0 μm,

[0349] B) b is in the range of 0.2 μm to 1.0 μm,

[0350] C) the W / b ratio is in the range of 1 to 1.5,

[0351] D) the H / b aspect ratio is in the range of 0.8 to 4.0, and

[0352] E) the angle of the longitudinal axis relative to the plane of the conductive layer is in the range of 60° to 90°; and

[0353] (ii) fewer than four second-type nanocolumns, each second-type nanocolumn being characterized by:

[0354] A) H is at least 1.0 μm, and

[0355] B) the W / b ratio is greater than 1.5.

[0356] 96. The current collector according to embodiment 95, wherein the surface layer comprises a first surface sublayer disposed above the copper-containing nanocolumn core and a second surface sublayer disposed above the first surface sublayer.

[0357] 97. The current collector according to embodiment 96, wherein:

[0358] (i) the first surface sublayer comprises zinc,

[0359] (ii) The second surface sublayer includes a metal-oxide compound, wherein the metal-oxide compound includes a transition metal other than zinc.

[0360] 98. The current collector according to any one of embodiments 95–97, wherein a cross-section with an average length of 20 μm includes at least eight first-type nanocolumns and less than three second-type nanocolumns.

[0361] 99. The current collector according to any one of embodiments 95–98, wherein the conductive layer includes nickel in a nickel layer.

[0362] 100. The current collector according to embodiment 99, wherein the conductive layer further includes a metal interlayer between the nickel layer and the surface layer.

[0363] 101. The current collector according to embodiment 100, wherein the metal interlayer includes copper.

[0364] 102. The current collector according to any one of embodiments 95–98, wherein the conductive layer includes copper.

[0365] 103. The current collector according to embodiment 102, wherein the conductive layer includes a copper alloy, and the copper alloy includes copper, magnesium, silver, and phosphorus.

[0366] 104. The current collector according to embodiment 102, wherein the conductive layer includes a copper alloy, and the copper alloy includes copper, iron, and phosphorus.

[0367] 105. The current collector according to embodiment 102, wherein the conductive layer includes a copper alloy, and the copper alloy includes brass or bronze.

[0368] 106. The current collector according to embodiment 102, wherein the conductive layer includes a copper alloy, and the copper alloy includes copper, nickel, and silicon.

[0369] 107. The current collector according to any one of embodiments 95–106, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 500 MPa.

[0370] 108. The current collector according to any one of embodiments 95–106, wherein the conductive layer or the current collector is characterized by a tensile strength greater than 600 MPa.

[0371] 109. The current collector according to any one of embodiments 95–106, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 700 MPa.

[0372] 110. The current collector according to any one of embodiments 95–109, wherein the conductive layer includes a roll-formed metal foil.

[0373] 111. The current collector according to any one of embodiments 95–110, wherein the surface layer is further disposed above a conductive layer in a gap region between the nanocolumn features.

[0374] 112. The current collector according to any one of embodiments 95–111, wherein the copper-containing nanocolumn core is formed by electrochemical deposition.

[0375] 113. The current collector according to any one of embodiments 96–112, wherein the first surface sublayer comprises at least 98 atomic % zinc relative to all metal atoms in the first surface sublayer.

[0376] 114. The current collector according to any one of embodiments 96–113, wherein the first surface sublayer comprises a zinc alloy.

[0377] 115. The current collector according to embodiment 114, wherein the first surface sublayer comprises less than 98 atomic % zinc relative to all metal atoms in the first surface sublayer.

[0378] 116. The current collector according to embodiment 114 or 115, wherein the zinc alloy comprises zinc and nickel.

[0379] 117. The current collector according to embodiment 116, wherein the first surface sublayer comprises 3 to 30 atomic % nickel.

[0380] 118. The current collector according to any one of embodiments 96–117, wherein the first surface sublayer comprises zinc in the range of 10 to 3000 mg / m 2 range.

[0381] 119. The current collector according to embodiment 113, wherein the first surface sublayer comprises zinc in the range of 10 to 100 mg / m 2 range.

[0382] 120. The current collector according to any one of embodiments 114–117, wherein the first surface sublayer comprises zinc in the range of 500 to 3000 mg / m 2 range.

[0383] 121. The current collector according to any one of embodiments 97–120, wherein the metal-oxide compound comprises a metal oxide.

[0384] 122. The current collector according to any one of embodiments 97–121, wherein the metal-oxide compound comprises a metal oxysalt.

[0385] 123. The current collector according to any one of embodiments 97–122, wherein the transition metal of the metal-oxide compound comprises titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium or niobium.

[0386] 124. A current collector according to any one of embodiments 97–122, wherein the transition metal of the metal-oxide comprises chromium.

[0387] 125. The current collector according to embodiment 124, wherein the second surface sublayer comprises chromium in the range of 2 to 50 mg / m 2 range.

[0388] 126. A current collector for an anode of a lithium-ion storage device, the current collector comprising a conductive layer and a surface layer disposed above the conductive layer, the surface layer comprising a first surface sublayer and a second surface sublayer disposed above the first surface sublayer,

[0389] wherein:

[0390] (i) The first surface sublayer comprises a metal oxide,

[0391] (ii) The second surface sublayer comprises a silicon compound, wherein the silicon compound comprises a siloxane, a siloxysilane or a silazane, or is derived from a siloxane, a siloxysilane or a silazane, and

[0392] (iii) The current collector is characterized in that the surface roughness Ra≥400 nm.

[0393] 127. The current collector according to embodiment 126, wherein the metal oxide comprises a transition metal.

[0394] 128. The current collector according to embodiment 126, wherein the metal oxide comprises oxides of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium or niobium.

[0395] 129. The current collector according to embodiment 126, wherein the metal oxide comprises at least a single layer of copper oxide.

[0396] 130. The current collector according to any one of embodiments 126–129, wherein the second surface sublayer comprises 1 to 100 mg / m 2 of silicon.

[0397] 131. The current collector according to any one of embodiments 126–130, wherein the second surface sublayer further comprises a metal-oxide, wherein the metal-oxide comprises a transition metal other than copper.

[0398] 132. The current collector according to embodiment 131, wherein the metal-oxide comprises a metal oxide.

[0399] 133. The current collector according to embodiment 131 or 132, wherein the metal-oxide comprises a metal oxalate.

[0400] 134. The current collector according to any one of embodiments 131–133, wherein the transition metal of the metal-oxide compound includes titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium, or niobium.

[0401] 135. The current collector according to any one of embodiments 131–133, wherein the transition metal of the metal-oxide compound includes molybdenum.

[0402] 136. The current collector according to any one of embodiments 126–135, wherein the conductive layer includes nickel in the nickel layer.

[0403] 137. The current collector according to embodiment 136, wherein the conductive layer further includes a metal interlayer between the nickel layer and the surface layer.

[0404] 138. The current collector according to embodiment 137, wherein the metal interlayer includes copper.

[0405] 139. The current collector according to any one of embodiments 136–138, wherein the average interlayer thickness of the metal interlayer is less than 50% of the total average thickness of the conductive layer.

[0406] 140. The current collector according to any one of embodiments 126–135, wherein the conductive layer includes copper.

[0407] 141. The current collector according to embodiment 140, wherein the conductive layer includes a copper alloy, and the copper alloy includes copper, magnesium, silver, and phosphorus.

[0408] 142. The current collector according to embodiment 140, wherein the conductive layer includes a copper alloy, and the copper alloy includes copper, iron, and phosphorus.

[0409] 143. The current collector according to embodiment 140, wherein the conductive layer includes a copper alloy, and the copper alloy includes brass or bronze.

[0410] 144. The current collector according to embodiment 140, wherein the conductive layer includes a copper alloy, and the copper alloy includes copper, nickel, and silicon.

[0411] 145. The current collector according to any one of embodiments 126–144, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 500 MPa.

[0412] 146. The current collector according to any one of embodiments 126–144, wherein the conductive layer or the current collector is characterized by a tensile strength greater than 600 MPa.

[0413] 147. The current collector according to any one of embodiments 126–144, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 700 MPa.

[0414] 148. A current collector according to any one of embodiments 126–147, wherein the conductive layer comprises a roll-formed metal foil.

[0415] 149. A current collector according to any one of embodiments 121–143, wherein the silicon compound comprises or is derived from a compound according to formula (1)

[0416] Si(R) n (OR’) 4-n (1)

[0417] wherein n = 1, 2 or 3, and R and R’ are independently selected from substituted or unsubstituted alkyl, alkenyl or aryl.

[0418] 150. A current collector according to any one of embodiments 126–149, wherein the surface of the current collector is characterized by indentations.

[0419] 151. A current collector according to embodiment 150, wherein the indentations are formed by chemical roughening using a chemical etchant.

[0420] 152. A current collector according to any one of embodiments 126–151, wherein the current collector is characterized in that the surface roughness Ra ≥ 550 nm.

[0421] 153. An anode for a lithium-ion energy storage device, the anode comprising a current collector according to any one of embodiments 95–152 and a lithium storage layer disposed above the current collector.

[0422] 154. An anode according to embodiment 153, wherein the lithium storage layer comprises silicon.

[0423] 155. An anode according to embodiment 153 or 154, wherein the lithium storage layer comprises at least 40 atomic % of silicon, germanium or a combination thereof.

[0424] 156. An anode according to any one of embodiments 153–155, wherein the lithium storage layer further comprises a carbon-based binder.

[0425] 157. An anode according to any one of embodiments 153–155, wherein the lithium storage layer is substantially free of a carbon-based binder.

[0426] 158. An anode according to embodiment 157, wherein the lithium storage layer comprises substoichiometric silicon nitride.

[0427] 159. An anode according to embodiment 157, wherein the lithium storage layer comprises at least 80 atomic % of amorphous silicon and has a density in the range of 1.2 to 2.25 g / cm 3 range.

[0428] 160. The anode according to any one of embodiments 157–159, wherein the lithium storage layer is a continuous porous lithium storage layer.

[0429] 161. The anode according to any one of embodiments 157–160, wherein the lithium storage layer is deposited by a PECVD process.

[0430] 162. A method of manufacturing a current collector for an energy storage device, the method comprising:

[0431] chemically roughening the surface of a conductive layer containing copper by treating with a chemical etchant to form a roughened conductive layer; and

[0432] forming a surface layer over the conductive layer by contacting the roughened conductive layer with a silicon compound reagent comprising a siloxane, a siloxysilane, or a silane, the surface layer comprising a silicon compound reagent or a silicon compound derived from the silicon compound reagent.

[0433] Wherein:

[0434] (i) The current collector is characterized in that the surface roughness Ra≥400nm,

[0435] (ii) The chemical roughening does not include electrodeposition, and

[0436] (iii) The formation of the surface layer does not include electrodeposition.

[0437] 163. The method according to embodiment 162, wherein the silicon compound reagent is provided in the form of a solution or a vapor.

[0438] 164. The method according to embodiment 162 or 163, further comprising heating the roughened conductive layer to a temperature of at least 100 °C after contacting with the silicon compound reagent.

[0439] 165. The method according to any one of embodiments 162–164, wherein the silicon compound reagent comprises a compound according to formula (1):

[0440] Si(R) n (OR’) 4-n (1)

[0441] wherein n = 1, 2 or 3, and R and R’ are independently selected from substituted or unsubstituted alkyl, alkenyl or aryl.

[0442] 166. The method according to any one of embodiments 162–165, wherein the silicon compound reagent is provided in the form of a solution, the solution further comprising a metal-oxide compound, wherein the metal-oxide compound comprises a transition metal.

[0443] 167. The method according to embodiment 166, wherein the metal-oxide comprises a metal oxysalt.

[0444] 168. The method according to embodiment 166 or 167, wherein the transition metal of the metal-oxide comprises titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium or niobium.

[0445] 169. The method according to embodiment 166 or 167, wherein the transition metal of the metal-oxide comprises molybdenum.

[0446] 170. The method according to any one of embodiments 162–169, wherein forming the surface layer further comprises forming a first surface sub-layer adjacent to the roughened conductive layer and forming a second surface sub-layer over the first surface sub-layer.

[0447] 171. The method according to embodiment 170, wherein the first surface sub-layer comprises a metal oxide and the second surface sub-layer comprises a silicon compound.

[0448] 172. The method according to embodiment 171, wherein the metal oxide comprises a transition metal.

[0449] 173. The method according to embodiment 171, wherein the metal oxide comprises oxides of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium or niobium.

[0450] 174. The method according to embodiment 171, wherein the metal oxide comprises at least a single layer of copper oxide.

[0451] 175. The method according to any one of embodiments 162–174, wherein the chemical etchant comprises an oxidizing agent.

[0452] 176. The method according to any one of embodiments 162–175, wherein the chemical etchant comprises an organic acid.

[0453] 177. The method according to any one of embodiments 162–176, further comprising etching a plurality of dimples into the surface of the conductive layer.

[0454] 178. A current collector for an anode of a lithium-ion storage device, the current collector comprising a conductive layer and a surface layer disposed over the conductive layer, the surface layer comprising a first surface sub-layer adjacent to the conductive layer and a second surface sub-layer disposed over the first surface sub-layer,

[0455] wherein:

[0456] (i) the first surface sub-layer comprises zinc,

[0457] (ii) The second surface sublayer comprises a metal-oxide compound, wherein the metal-oxide compound comprises a transition metal other than zinc, and

[0458] (iii) The current collector is characterized in that the surface roughness Ra ≥ 250 nm.

[0459] 179. The current collector according to embodiment 178, wherein the surface layer further comprises a third surface sublayer disposed above the second surface sublayer, and the third surface sublayer comprises a silicon compound.

[0460] 180. The current collector according to embodiment 179, wherein the silicon compound comprises siloxane, siloxysilane or silazane, or is derived from siloxane, siloxysilane or silazane.

[0461] 181. The current collector according to embodiment 179, wherein the silicon compound comprises or is derived from a compound according to formula (1):

[0462] Si(R) n (OR’) 4-n (1)

[0463] wherein n = 1, 2 or 3, and R and R’ are independently selected from substituted or unsubstituted alkyl, alkenyl or aryl.

[0464] 182. The current collector according to any one of embodiments 179–181, wherein the surface layer further comprises a fourth surface sublayer disposed above the third surface sublayer, and the fourth surface sublayer comprises a metal oxide.

[0465] 183. The current collector according to embodiment 182, wherein the metal oxide is a transition metal oxide.

[0466] 184. The current collector according to embodiment 182, wherein the metal oxide comprises oxides of the following metals: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium or niobium.

[0467] 185. The current collector according to embodiment 178, wherein the surface layer does not comprise a silicon compound.

[0468] 186. The current collector according to embodiment 178 or 185, wherein the surface layer further comprises a third surface sublayer disposed above the second surface sublayer, and the third surface sublayer comprises a metal oxide.

[0469] 187. The current collector according to embodiment 186, wherein the metal oxide is a transition metal oxide.

[0470] 188. The current collector according to embodiment 186, wherein the metal oxide comprises an oxide of a metal selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, silver, zirconium, hafnium, tin, aluminum, indium, or niobium.

[0471] 187. The current collector according to any one of embodiments 178–188, wherein the first surface sublayer comprises at least 98 atomic % zinc relative to all metal atoms in the first surface sublayer.

[0472] 188. The current collector according to any one of embodiments 178–188, wherein the first surface sublayer comprises a zinc alloy.

[0473] 189. The current collector according to embodiment 188, wherein the first surface sublayer comprises less than 98 atomic % zinc relative to all metal atoms in the first surface sublayer.

[0474] 190. The current collector according to embodiment 188 or 189, wherein the zinc alloy comprises zinc and nickel.

[0475] 191. The current collector according to embodiment 190, wherein the first surface sublayer comprises from 3 to 30 atomic % nickel.

[0476] 192. The current collector according to any one of embodiments 178–191, wherein the first surface sublayer comprises zinc in the range of 10 to 3000 mg / m 2 range.

[0477] 193. The current collector according to embodiment 187, wherein the first surface sublayer comprises zinc in the range of 10 to 100 mg / m 2 range.

[0478] 194. The current collector according to any one of embodiments 188–191, wherein the first surface sublayer comprises zinc in the range of 500 to 3000 mg / m 2 range.

[0479] 195. The current collector according to any one of embodiments 178–194, wherein the metal-oxide compound comprises a metal oxide.

[0480] 196. The current collector according to any one of embodiments 178–195, wherein the metal-oxide compound comprises a metal oxysalt.

[0481] 197. The current collector according to any one of embodiments 178–196, wherein the transition metal of the metal-oxide compound comprises titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium, or niobium.

[0482] 198. A current collector according to any one of embodiments 178–196, wherein the transition metal of the metal-oxide comprises chromium.

[0483] 199. A current collector according to embodiment 198, wherein the second surface sublayer comprises chromium in the range of 2 to 50 mg / m 2 range.

[0484] 200. A current collector according to any one of embodiments 178–199, wherein the conductive layer comprises nickel in the nickel layer.

[0485] 201. A current collector according to embodiment 200, wherein the conductive layer further comprises a metal interlayer between the nickel layer and the surface layer.

[0486] 202. A current collector according to embodiment 201, wherein the metal interlayer comprises copper.

[0487] 203. A current collector according to embodiment 201 or 202, wherein the average interlayer thickness of the metal interlayer is less than 50% of the total average thickness of the conductive layer.

[0488] 204. A current collector according to any one of embodiments 178–199, wherein the conductive layer comprises copper.

[0489] 205. A current collector according to embodiment 204, wherein the conductive layer comprises a copper alloy comprising copper, magnesium, silver, and phosphorus.

[0490] 206. A current collector according to embodiment 204, wherein the conductive layer comprises a copper alloy comprising copper, iron, and phosphorus.

[0491] 207. A current collector according to embodiment 204, wherein the conductive layer comprises a copper alloy comprising brass or bronze.

[0492] 208. A current collector according to embodiment 204, wherein the conductive layer comprises a copper alloy comprising copper, nickel, and silicon.

[0493] 209. A current collector according to any one of embodiments 178–208, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 500 MPa.

[0494] 210. A current collector according to any one of embodiments 178–208, wherein the conductive layer or the current collector is characterized by a tensile strength greater than 600 MPa.

[0495] 211. A current collector according to any one of embodiments 178–208, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 700 MPa.

[0496] 212. A current collector according to any one of embodiments 178–211, wherein the conductive layer comprises a roll-formed metal foil.

[0497] 213. A method of manufacturing an anode for an energy storage device, the method comprising:

[0498] providing a current collector according to any one of embodiments 95–152 or 178–212, or providing a current collector manufactured by a method according to any one of embodiments 162–177; and

[0499] forming a lithium storage layer disposed over the current collector by chemical vapor deposition using a silane-containing gas.

[0500] 214. The method according to embodiment 213, wherein the chemical vapor deposition comprises a PECVD process.

[0501] 215. The method according to embodiment 214, wherein the PECVD process comprises forming a capacitively coupled plasma or an inductively coupled plasma.

[0502] 216. The method according to embodiment 214, wherein the PECVD process comprises a DC plasma source, an AC plasma source, an RF plasma source, a VHF plasma source, or a microwave plasma source.

[0503] 217. The method according to embodiment 214, wherein the PECVD process comprises magnetron-assisted RF PECVD.

[0504] 218. The method according to embodiment 214, wherein the PECVD process comprises expanding a thermal plasma chemical vapor deposition.

[0505] 219. The method according to embodiment 214, wherein the PECVD process comprises hollow cathode PECVD.

[0506] 220. The method according to any one of embodiments 213–219, wherein the lithium storage layer comprises at least 40 atomic % of silicon, germanium, or a combination thereof.

[0507] 221. The method according to any one of embodiments 213–220, wherein the lithium storage layer comprises less than 10 atomic % of carbon.

[0508] 222. The method according to any one of embodiments 213–221, wherein the lithium storage layer is substantially free of lithium storage nanostructures.

[0509] 223. The method according to any one of embodiments 213–222, wherein the lithium storage layer is a continuous porous lithium storage layer.

[0510] 224. A method according to any one of embodiments 213–223, wherein the lithium storage layer comprises substoichiometric silicon nitride.

[0511] 225. A method according to any one of embodiments 213–224, wherein the lithium storage layer comprises substoichiometric silicon oxide.

[0512] 226. A method according to any one of embodiments 213–225, wherein the lithium storage layer comprises at least 80 atomic % amorphous silicon.

[0513] 227. A method according to embodiment 226, wherein the density of the lithium storage layer is in the range of 1.1 to 2.25 g / cm 3 range.

[0514] 228. A method according to any one of embodiments 213–225, wherein the lithium storage layer comprises up to 30% nanocrystalline silicon.

[0515] 229. A method according to any one of embodiments 213–228, wherein the lithium storage layer comprises columns of aggregates of silicon nanoparticles.

[0516] 230. A method according to any one of embodiments 213–229, wherein the lithium storage layer has an average thickness of at least 7 μm.

[0517] 231. A method according to any one of embodiments 213–230, wherein the silane-containing gas is silane.

[0518] 232. A method according to any one of embodiments 213–231, further comprising adding hydrogen during chemical vapor deposition, wherein the ratio of the silane-containing gas to hydrogen is 2 or less.

[0519] 233. A method according to any one of embodiments 213–232, further comprising doping the lithium storage layer with boron, phosphorus, sulfur, fluorine, aluminum, gallium, indium, arsenic, antimony, or bismuth, or a combination thereof.

[0520] 234. A method for preparing a prelithiated anode, the method comprising:

[0521] i) providing an anode according to any one of embodiments 1–83 or 153–161, or an anode manufactured according to any one of embodiments 213–232; and

[0522] ii) incorporating lithium into the lithium storage layer of the anode to fill at least 5% of the lithium storage capacity, thereby forming a prelithiated anode.

[0523] 235. A method according to embodiment 234, further comprising depositing lithium metal over the lithium storage layer.

[0524] The method according to embodiment 234 further comprises contacting the lithium storage layer with a reducing lithium organic compound.

[0525] The method according to embodiment 234 further comprises electrochemically reducing lithium ions at the anode in a prelithiation solution.

[0526] Without departing from the spirit and scope of the embodiments of the present invention, the specific details of particular embodiments may be combined in any suitable manner. However, other embodiments of the present invention may be directed to particular embodiments related to each individual aspect or a particular combination of these individual aspects.

[0527] For purposes of illustration and description, the foregoing description of example embodiments of the present invention has been presented. 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 above teachings.

[0528] In the foregoing description, for purposes of explanation, numerous details have been set forth in order to provide an understanding of the various embodiments of the present technology. However, it will be apparent to one of ordinary skill in the art that some embodiments may be practiced without some of these details or with additional details.

[0529] Several embodiments have been described and those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, in order to avoid unnecessarily obscuring the present invention, many well-known processes and elements have not been described. Moreover, the details of any particular embodiment may not always be present in variations of that embodiment or may be added to other embodiments.

[0530] Where a numerical range is provided, it is understood that each intermediate value between the upper and lower limits of that range to one-tenth of the lower limit unit is also specifically disclosed, unless the context clearly dictates otherwise. Each smaller range between any of the specified values or any intermediate value in the specified range and any other specified value or any other intermediate value in the specified range is also encompassed. The upper and lower limits of these smaller ranges may independently be included in or excluded from the range, and each range that includes one, excludes one, or includes both of the limits in the smaller range is also encompassed within the present invention and is subject to any specifically excluded limit within the specified range. When the range includes one or both of the limits, ranges excluding one or both of the included limits are also included.

[0531] 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, reference to "an anode" includes reference to one or more anodes and equivalents thereof known to those of ordinary skill in the art, and so forth. For purposes of clarity and understanding, the invention has been described in detail. However, it should be understood that certain changes and modifications may be practiced within the scope of the appended claims.

[0532] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. None of them are admitted to be prior art.

Claims

1. An anode for an energy storage device, the anode comprising: a) A current collector, which includes: A conductive layer; A plurality of nanocolumn features disposed above the conductive layer, wherein each of the plurality of nanocolumn features includes a copper-containing nanocolumn core; Wherein each nanocolumn feature has a longitudinal axis passing through the centroid of the nanocolumn feature; and A surface layer disposed above the conductive layer, wherein the surface layer is at least partially located above the copper-containing nanocolumn core, and the surface layer includes a first surface sublayer adjacent to the conductive layer and a second surface sublayer disposed above the first surface sublayer, Wherein: (i) The first surface sublayer includes zinc, (ii) The second surface sublayer includes a metal-oxide compound, wherein the metal-oxide compound includes a transition metal other than zinc, and (iii) The current collector is characterized by a surface roughness Ra≥250nm; and b) A continuous porous lithium storage layer covering the surface layer, wherein the continuous porous lithium storage layer: (i) Has an average thickness of at least 2.5μm, (ii) Contains at least 40 atomic% of silicon, germanium or a combination thereof, and (iii) Is substantially free of carbon-based binders.

2. The anode according to claim 1, wherein the surface layer further includes a third surface sublayer disposed above the second surface sublayer, and the third surface sublayer contains a silicon compound, wherein the silicon compound includes siloxane, siloxysilane or silazane, or is derived from siloxane, siloxysilane or silazane.

3. The anode according to any one of claims 1-2, wherein the first surface sublayer includes at least 98 atomic% of zinc relative to all metal atoms in the first surface sublayer.

4. The anode according to any one of claims 1-2, wherein the first surface sublayer includes a zinc alloy.

5. The anode according to claim 4, wherein the zinc alloy includes zinc and nickel.

6. The anode according to claim 5, wherein the first surface sublayer includes 3 to 30 atomic% of nickel.

7. The anode according to any one of claims 1-2, wherein the metal-oxide compound includes a metal oxide.

8. The anode according to any one of claims 1-2, wherein the metal-oxide compound includes a metal oxalate.

9. The anode according to any one of claims 1-2, wherein the average thickness of the continuous porous lithium storage layer is at least 4μm.

10. The anode according to any one of claims 1-2, wherein the average thickness of the continuous porous lithium storage layer is at least 7μm.

11. The anode according to any one of claims 1-2, wherein the transition metal of the metal-oxide compound includes titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, tungsten, zirconium or niobium.

12. The anode according to any one of claims 1-2, wherein each of the nanocolumn features is characterized by a height H, a bottom width B and a maximum width W, and Wherein the average 20μm long cross-section of the current collector includes: (i) At least five first-type nanocolumns, each first-type nanocolumn being characterized by, A) H ranges from 0.4 μm to 3.0 μm, B) B ranges from 0.2 μm to 1.0 μm, C) the W / B ratio ranges from 1 to 1.5, D) the H / B aspect ratio ranges from 0.8 to 4.0, and E) the angle of the longitudinal axis with respect to the plane of the conductive layer ranges from 60° to 90°; and (ii) less than four type-II nanocolumns, each type-II nanocolumn being characterized by A) H being at least 1.0 μm, and B) the W / B ratio being greater than 1.

5.

13. The anode according to any one of claims 1-2, wherein the conductive layer comprises nickel in a nickel layer.

14. The anode according to claim 13, wherein the conductive layer further comprises a metal interlayer between the nickel layer and the surface layer.

15. The anode according to any one of claims 1-2, wherein the conductive layer comprises copper.

16. The anode according to claim 15, wherein the conductive layer comprises a copper alloy comprising copper, nickel and silicon.

17. The anode according to any one of claims 1-2, wherein the conductive layer comprises a network of conductive carbon.

18. The anode according to any one of claims 1-2, wherein the conductive layer or the current collector is characterized by a tensile strength of at least 700 MPa.

19. The anode according to any one of claims 1-2, wherein the continuous porous lithium storage layer comprises at least 80 atomic % amorphous silicon.

20. The anode according to claim 19, wherein the density of the continuous porous lithium storage layer is in the range of 1.1 to 2.25 g / cm 3 3

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