Source: http://patents.com/us-10044046.html
Timestamp: 2018-11-17 17:06:47
Document Index: 612769669

Matched Legal Cases: ['application No. 2012', 'application No. 201180019460', 'application No. 100120247', 'application No. 201180019460', 'application No. 2012', 'application No. 11751259', 'application No. 11751259', 'application No. 201510674597', 'application No. 2016', 'application No. 10', 'Application No. 61']

US Patent # 1,004,4046. Deposition on two sides of a web - Patents.com
United States Patent 10,044,046
Mosso , et al. August 7, 2018
Mosso; Ronald J. (Fremont, CA), Loveness; Ghyrn E. (Mountain View, CA)
Amprius,Inc.
Family ID: 44143243
14/252,633
US 20140302232 A1 Oct 9, 2014
12637727 Dec 14, 2009
Current CPC Class: C23C 16/0209 (20130101); C23C 16/52 (20130101); C23C 16/545 (20130101); C23C 16/56 (20130101); H01M 4/0421 (20130101); H01M 4/139 (20130101); H01M 4/386 (20130101); H01M 6/40 (20130101); C23C 16/42 (20130101); C23C 16/26 (20130101); C23C 16/22 (20130101); C23C 16/042 (20130101); C23C 16/0272 (20130101); C23C 16/24 (20130101); B05D 1/62 (20130101); B05D 2252/02 (20130101); B05D 2252/10 (20130101); H01M 4/366 (20130101); Y10S 977/843 (20130101); Y10S 977/897 (20130101); B82Y 40/00 (20130101)
Current International Class: C23C 16/00 (20060101); C23C 16/56 (20060101); C23C 16/54 (20060101); C23C 16/52 (20060101); C23C 16/02 (20060101); H01M 6/40 (20060101); H01M 4/04 (20060101); C23C 16/42 (20060101); C23C 16/26 (20060101); H01M 4/139 (20100101); H01M 4/38 (20060101); C23C 16/04 (20060101); C23C 16/22 (20060101); C23C 16/24 (20060101); B05D 1/00 (20060101); H01M 4/36 (20060101); B82Y 40/00 (20110101)
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This application is a divisional of and claims priority to U.S. application Ser. No. 12/637,727, titled "APPARATUS FOR DEPOSITION ON TWO SIDES OF THE WEB," filed Dec. 14, 2009, all of which is incorporated herein by this reference for all purposes.
1. A method comprising: (a) receiving a continuous web at an inlet of a first deposition station and passing the web through the first deposition station; and (b) using a dry deposition process to produce nanowires rooted to the web surface on both sides of the web, wherein the nanowires are crystalline silicon.
2. The method of claim 1, wherein the dry deposition process comprises a chemical vapor deposition process or a physical vapor deposition process.
3. The method of claim 1, further comprising: (c) receiving the continuous web with rooted nanowires at an inlet of a second deposition station and passing the web through the second deposition station; and (d) using a dry deposition process to deposit a second material onto the nanowires on both sides of the web.
4. The method of claim 3, wherein the second material comprises electrochemically active material.
5. The method of claim 4, wherein the electrochemically active material comprises at least one of lithium and amorphous silicon.
6. The method of claim 3, wherein the second material comprises battery electrolyte material.
7. The method of claim 3, wherein the second material comprises polymer binder.
8. A method comprising: (a) receiving a continuous web at an inlet of a first deposition station and passing the web through the first deposition station; and (b) using a dry deposition process to produce nanowires rooted to the web surface on both sides of the web, wherein the nanowires are silicide nanowires.
9. The method of claim 8, wherein in passing the web through the first deposition station, the web does not physically contact any hardware components.
10. The method of claim 8, wherein the receiving the continuous web comprises unwinding a substrate web from a roll.
11. The method of claim 8, wherein the web is made of a material selected from the group consisting of copper, copper alloy, nickel, nickel alloy, and steel.
12. The method of claim 8, wherein the web has a width of at least about 500 millimeters.
13. The method of claim 8, wherein the web has a thickness of between about 5 micrometers and 50 micrometers.
14. The method of claim 8, wherein the dry deposition process comprises a chemical vapor deposition process or a physical vapor deposition process.
15. The method of claim 8, further comprising: (c) receiving the continuous web with rooted nanowires at an inlet of a second deposition station and passing the web through the second deposition station; and (d) using a dry deposition process to deposit a second material onto the nanowires on both sides of the web.
16. The method of claim 15, wherein the second material comprises electrochemically active material.
17. The method of claim 16, wherein the electrochemically active material comprises at least one of lithium and amorphous silicon.
18. The method of claim 15, wherein the second material comprises battery electrolyte material.
19. The method of claim 15, wherein the second material comprises polymer binder.
20. The method of claim 8, wherein the passing the web through the first deposition station comprises feeding the web through the first deposition station at a speed of between about 1 meter per minute and 3 meters per minute.
21. The method of claim 8, wherein a web residence time in the first deposition station is at least about 5 minutes.
22. The method of claim 8, wherein a web residence time in the first deposition station is no greater than about 40 minutes.
23. The method of claim 8, further comprising depositing one or more layers on the web prior to (a).
24. The method of claim 8, further comprising, prior to (a), forming a mask on the web to exclude or promote, respectively, deposition of nanowires on the web.
25. The method of claim 8, further comprising, prior to (a), preheating the web.
26. The method of claim 8, further comprising, prior to (a), depositing electrochemically active electrode material on at least a portion the web.
27. The method of claim 15, further comprising passing the web through a cooling station after one or more of (b) and (d).
Further, during the second side deposition, the web with material already deposited on the first side is again exposed to process conditions, which may involve high temperature and/or reactive processing gases. The first side, which contacts the supporting surface under these conditions, often experiences substantial compressive and/or shear forces exerted by the supporting surface. Such approach may not be suitable for depositing fragile materials. For example, silicon nanowires may easily break when compressed or sheared at a temperature above 350.degree. C. A first side deposited materials (e.g., an active electrode layer) may collapse or break during second side deposition and become unsuitable for use in batteries or other applications.
An apparatus may include one or more deposition stations arranged to receive a web passing in a substantially vertical direction through the deposition apparatus. In certain embodiments, a deposition station may include a first port for delivering an electrode component material, or a precursor thereof, to a first side of the web as it passes through the deposition station. The station may also include a second port for delivering said electrode component material, or a precursor thereof, to a second side of the web as it passes through the deposition station. In some cases, the ports are designed to deliver materials employed in "dry" deposition processes such as CVD and PVD. Accordingly, dry process deposition may be performed on both sides of the web in the same station in a single pass. Typically, the apparatus is designed so that no hardware components come in physical contact with the web during deposition, while the web is passed through the deposition station.
Certain applications, such as fabrication of battery electrodes, require depositing materials on both sides of a substrate. Typically, the substrate is supplied on a roll, which is unwound and processed to deposit materials and eventually fabricate battery electrodes. Unwound substrate is also referred to as a "web". A web is typically first passed through a deposition station where one or more electrode component materials are deposited. For example, in a conventional process, wet slurry prepared by mixing active material, binder, and optionally conductive additives with solvent (e.g., water, NMP) is coated on both sides (one at a time) of the moving web. After coating of the first side, the resulting coat is dried and the process is repeated to coat the other side.
Certain materials can be deposited using various dry process techniques. A "dry process" is defined in this document as a process that does not involve liquids coming in contact with a web during deposition. For example, a CVD technique with a liquid precursor is considered a dry process if, e.g., the precursor evaporates or is atomized prior to contacting the deposition surface. Therefore, dry deposition techniques do not include slurry coating, which is conventionally used to deposit active materials in lithium ion battery fabrication. However, an apparatus used for dry deposition may also include one or more station for slurry coating and/or other non dry processes. Examples of dry processes include Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD), electrospinning, and aerosol spraying. For example, an electrochemically active layer containing silicon nanowires with crystalline cores and amorphous shells may be deposited on a conductive substrate using a combination of thermal CVD and Plasma Enhanced CVD (PECVD) and used for battery fabrication. In certain embodiments, methods and apparatus described in this document may used to deposit materials using techniques other than dry process techniques. For example, electrospinning and aerosol spraying techniques may involve a solvent that comes in contact with the substrate.
In certain embodiments, a method of fabricating an electrode involves passing a web in a substantially vertical direction through a deposition station of the deposition apparatus and depositing electrode component material on both sides of the web via a dry process. In particular embodiments, the web does not contact any hardware components while passing through a deposition station. Further, the web may pass through two or more deposition stations in between two web-contact points. In particular embodiments, the web may have an intermittent support in between two successive deposition stations. For example, a roller may be used to align the web in between two stations and to prevent wobbling of the web. Such roller may apply minimal force on the web relative to other rollers in the apparatus and only nominally change the direction of the web (e.g., less than about 10.degree. or, more specifically, less than about 5.degree.).
Sometimes deposition on both side of the web coincide with each other. In other words, the starting and ending points within a deposition station are the same for both sides of the web. However, in certain embodiments, deposition on one side may start and/or end earlier than on the other side. In the same or other embodiments, deposition on one side may be completed before deposition on the other side starts. For simplicity, when deposition on both sides is performed in the same deposition station, deposition is said to be performed "at the same time" or "simultaneously" regardless of how the deposition zone on one side aligns with the deposition on the other side.
For the purposes of this application, "electrochemically active material" (or, simply, "active material") is defined as an electrode's component that provides electrochemically reactive sites (e.g., ion insertion sites). Each electrode in an electrochemical cell has at least one corresponding active material. In traditional lithium ion cells, a cathode active material is generally lithium cobalt oxide powder, lithium iron phosphate, etc., while an anode active material is generally graphite powder. In certain embodiments of the present invention, active materials are deposited as or formed into nanostructures, such as nanowires and include one or more of the following components: silicon, germanium, tin, tin oxide, and titanium oxide.
An "active layer" is an electrode layer that contains active material and, generally, does not include substrate. However, in some cases, boundaries between the active layer and the substrate are not sharp or abrupt. This may be the case, for example, where the substrate is or includes mesh or foam. In certain embodiments, conductive substrate may abut one or two active layers of the electrode. For example, active material may be deposited as nanowires onto a metallic foil forming an active layer in the contact with the metallic foil. In other embodiments, an active layer may intertwine with a substrate, such as mesh substrate or a substrate that is reconfigured after nanowires deposition. An active layer may also contain other components that are not active materials, such as conductive additives and binders, collectively referred to as "additives."
In certain embodiments, deposited materials are "substrate-rooted", which means that such materials are physically and conductively attached to a substrate. Additional examples and description of sub-rooted structures are provided in U.S. patent application Ser. No. 12/437,529 (published as 2010/0285358) entitled "ELECTRODE INCLUDING NANOSTRUCTURES FOR RECHARGEABLE CELLS" filed on May 7, 2009, which is incorporated herein by reference in its entirety for purposes of describing "substrate rooted" structures.
As indicated, in some embodiments, the web may be pre-heated prior to the deposition operation 106. For example, a CVD process may require that the web be at a temperature of greater than about 300.degree. C. In particular embodiments, the web is pre-heated to at least about 250.degree. C. or, more specifically, to at least about 350.degree. C. prior to entering into a deposition station. Heating may be performed in an inert environment to prevent substrate oxidation. Further, a pre-heating station may be positioned immediately before the deposition station to minimize heat losses in between. It should be noted that some heating may be performed in the deposition station itself. However, in order to optimize utilization of space in the deposition station, in-situ heating may be limited to temperature control (e.g., minimal heating, controlling temperature ensuring), while most of the heating is performed in a pre-heating station. Additional description of heater examples and feature is provided in the context of FIG. 2.
As indicated, an overall process 100 may include one or more dry deposition operations 106. In certain embodiments, dry deposition operation involves a CVD process. For example, CVD may be used to deposit silicon containing nanoparticles or, more specifically, silicon containing nanowires onto a conductive substrate. Specific examples of silicon and other high capacity materials are described in U.S. patent application Ser. No. 12/437,529 entitled "Electrode Including Nanostructures for Rechargeable Cells" filed on May 7, 2009, which is incorporated by reference herein in its entirety for purposes of describing silicon and other high capacity materials. In particular embodiments, a process gas containing silane is introduced into the deposition station. Silane flow rate may be between about 10 sccm and 5,000 sccm for 1-meter wide substrate moving at a speed of about 1 meter per minute in a 1-20 meter long deposition zone. These parameters generally depend on the growth rate. While higher growth rate may be preferable, quality of the deposited materials and resulting battery performance may be unacceptable for such growth rates. In a particular embodiment, a web speed is about 1 meter per minute through a 5 meter deposition zone resulting in a 5 minute residence time. In other embodiments, residence time is between about 1 minute and 60 minutes or, more specifically between about 10 minutes and 30 minutes, which can be achieved by a taller deposition station and/or slower web speed. The web may be kept at between about 400.degree. C. and 600.degree. C. more specifically at about 500.degree. C. Deposition station pressure may be kept at between about 1 Torr and 600 Torr. Other dry deposition processes that may be employed include Atomic Layer Deposition (ALD), Physical Vapor Deposition (PVD), and E-Beam deposition, and the like.
In certain embodiments, process parameters are kept uniform for the entire web surface positioned within the deposition station. In other embodiments, the process parameters are varied along the traveling direction of the web. For example, deposition parameters such as substrate temperature, process gas composition, plasma energy, and the like, may be adjusted from top to bottom in a deposition station. In a specific embodiment, such variations are employed to deposit silicon containing nanostructures with crystalline cores/amorphous shells in the deposition station. In certain embodiments, crystalline silicon nanowires are grown at about 500.degree. C. in a process gas containing between about 1% to 100% molar concentration of silane by volume at a total pressure or between about 10 Torr and 600 Torr. The deposition time may vary from about 1 minute to about 30 minutes. Amorphous silicon coatings can be deposited at higher temperatures (e.g., at about 550.degree. C.) and/or higher silane concentrations. Changing process parameters (increasing temperature and/or silane concentration) may create sidewall deposition during the crystalline growth process. In some embodiments, an amorphous silicon coating is added in a separate operation after completing deposition of the crystalline silicon structures. Amorphous silicon can be deposited using either thermal or plasma enhanced CVD. Examples of conditions for amorphous silicon PECVD include temperature of between about 200.degree. C. and 400.degree. C., pressure of between about 1 Torr and 100 Torr, and silane concentrations of between about 1% to 50% in either argon, nitrogen, helium, hydrogen, or various combinations thereof. Deposition of amorphous silicon may be performed for between about 30 seconds and 30 minutes. In certain embodiments, CVD is performed at pressure levels that are higher than 100 Torr, more specifically, at about atmospheric pressure or even slightly above atmospheric pressure. Higher pressure in the deposition chamber may help to improve deposition rates.
In certain embodiments, multiple dry deposition operations are performed in separate stations, each depositing additional material on the web. For example, one operation may be performed to form a core structure (e.g., a nanowire core). Another operation may follow to form one or more shells around the core. Core-shell structures used for battery electrode are described in details in U.S. Patent Application No. 61/181,637 entitled "Core-Shell High Capacity Nanowires for Battery Electrodes" filed on May 27, 2009, which is incorporated herein by reference in its entirety for purposes of describing core-shell structures. Further, materials that may be deposited concurrently or sequentially with an electrochemically active material include, e.g., lithium, carbon, silicide forming materials (e.g., cobalt, nickel, etc.), and the like. Additionally, conductivity enhancing materials such as carbon, lithium, and the like may be deposited concurrently or sequentially with the active material. In still other embodiments, a separator material may be dry deposited on the active material. For example, a polymer electrolyte may be deposited by either physical vapor deposition or from monomers by chemical vapor deposition.
Process conditions may be selected to deposit materials with a desired weight per unit area. Usually, this is achieved by maintaining sufficiently high deposition rates and sufficient residence time in the deposition station. In particular embodiments, a silicon containing active material is deposited to a loading, defined as a weight per unit area, of between about 1 mg/cm.sup.2 and 7 mg/cm.sup.2 or, more specifically between about 3 mg/cm.sup.2 and 5 mg/cm.sup.2. In the same or other embodiments, a portion of the web that is within the deposition station has a length of between about 1 m and 20 m or, more specifically between about 5 m and 15 m. Further, in the same or other embodiments, a web speed is between about 0.1 m/min and 10 m/min or, more specifically, between about 0.5 m/min and 5 m/min. The residence time in the deposition station or, more specifically, in the deposition zone may be between about 1 min and 100 min or, more specifically, between about 5 min and 25 min.
In certain embodiments, some or all active material is deposited after operation 106. For example, dry deposition may be used to deposit one or more intermediate layers and then active materials are deposited with wet slurry coating or some other deposition technique. In the same or other embodiments, a binder, conductive additives, and lithium containing materials are deposited into the web after operation 106. Lithium may be mechanically deposited as lithium metal nanoparticles, nano-dots, or a nano-powder, lithium foil and then integrated into the active materials (e.g., annealed. resputtered). As indicated, in certain embodiments, lithium is added to the anode such that its amount corresponds to between about 5% and 50% of the theoretical capacity of the active material used on the anode or, more specifically, to between about 5% and 25% of that capacity. Additional examples and description of lithium preloading are presented in U.S. patent application Ser. No. 12/944,593 entitled "PRELOADING LITHIUM ION CELL COMPONENTS WITH LITHIUM" filed on Nov. 11, 2010, which is incorporated herein by reference in its entirety for purposes of describing lithium pre-loading.
In certain embodiments, a web with previously deposited materials may be annealed, for example, to establish bonds among deposited particles (e.g., nanowires) and/or between the particles and the substrate. Annealing may involve exposing a web to elevated temperatures (e.g., by passing through a heater), such as at least about 400.degree. C. or, more specifically, at least about 500.degree. C. In particular embodiments, a web with deposited material is passed through compression rollers that exert a constant pressure on the web or force the web through a constant gap. The rollers may be heated to at least about 80.degree. C. or, more specifically, at least about 100.degree. C.
Prior to winding a web to a take-up roll (or processing it in other ways, e.g., cutting into plates), the web may be cooled down. As mentioned above, cooling may be necessary to strengthen a deposited layer(s) prior to exerting pressure on this layer or contacting it to certain surfaces. In certain embodiments, a web is cooled down to below about 100.degree. C. or, more specifically, below about 50.degree. C.
In some embodiments, a mesh can be used as a substrate. Meshes are generally characterized by a wire diameter, opening size, overall thickness, and weave type. For example, meshes having a wire diameter of between about 50 nm and 500 .mu.m and an opening size of between about 50 nm and 500 .mu.m may be used. Various weave types may be used, in particular ones that are expandable and can easily change configuration during battery cycling in order to minimize fluctuation of the overall electrode thickness and, maintain pressure to the nanostructures during full discharge to ensure electrical connectivity between various components of the electrode.
In certain embodiments, substrate is a metallic foil with a thickness of at least 5 .mu.m or, more specifically, at least about 10 .mu.m. A thickness is generally determined by substrate's mechanical properties (e.g., flexibility, tensile stress) and electrical properties (e.g., conductivity). In particular embodiments, a copper foil with a thickness of between about 5 .mu.m and 30 .mu.m or, more specifically, between about 5 .mu.m and 20 .mu.m coated with nickel having a thickness of between about 0.5 .mu.m and 2 .mu.m is used. In other embodiments, a stainless steel foil with a thickness of between about 5 .mu.m and 50 .mu.m or, more specifically, between about 20 .mu.m and 30 .mu.m is used. Other examples of foil substrates are presented in the table below.
TABLE-US-00001 TABLE Material Thickness Ranges, micrometers Nickel 5-50; 10-30 Titanium 5-25; 10-20 Aluminum 10-50; 20-30 Copper 5-50; 10-30
Another factor in a substrate selection process is substrates ability to withstand weights of the substrate and any deposited materials as well as any tension exerted by tension control mechanisms. Further, deposition is usually performed on the heated web, which may substantially affect its strength. For example, yield strength of pure copper drops almost tenfold when it is heated from 20.degree. C. to about 500.degree. C., which may be a temperature during a CVD process. While a copper foil can support its own weight of up to 400 m at this temperature, when a 5 mg/cm.sup.2 coating is added on both side of a 10 .mu.m copper foil it can only support of up to 200 m. Thicker coatings, higher deposition temperatures, and additional tension form the apparatus may require thicker substrates.
In certain embodiments, substrate has an open structure. Such substrate may take various forms including, for example, a porous block, foam, or mesh. Additionally, such substrate may be a perforated sheet or a rough sheet (e.g., a sheet having a roughness of at least about 0.1 .mu.m R.sub.a). In general, the solid portion of open structure substrate contains a plurality of openings such as, for example, voids, pores, cavities, punctures, and/or scratches. In certain embodiments, the substrate's ratio of surface area to volume (volume defined by an outer surface of the substrate that does not follow the contours defined by the void spaces) is greater than that of the corresponding solid version of the substrate (one having the same volume as the open structure). In certain embodiments, a substrate layer with open structures has a fractional void volume of at least about 10% or, more specifically, at least about 20%, at least about 30%, at least about 50%, at least about 60%, or at least about 70%, or at least about 90%, or at least about 95%. Additional examples and description of open structure substrates are presented in U.S. Pat. No. 8,637,185, entitled "OPEN STRUCTURES IN SUBSTRATES FOR ELECTRODES" issued on Jan. 28, 2014, which is incorporated herein by reference in its entirety for purposes of describing open structure substrates.
In certain embodiments, apparatuses and methods described above are used to deposit electrochemically active materials onto a web. Examples of electrochemically active materials include silicon containing materials (e.g., crystalline silicon, amorphous silicon, silicides, silicon oxides, sub-oxides, oxynitrides), tin-containing materials (e.g., tin, tin oxide), germanium, carbon-containing materials, a variety of metal hydrides (e.g., MgH.sub.2), silicides, phosphides, and nitrides. Other examples include: carbon-silicon combinations (e.g., carbon-coated silicon, silicon-coated carbon, carbon doped with silicon, silicon doped with carbon, and alloys including carbon and silicon), carbon-germanium combinations (e.g., carbon-coated germanium, germanium-coated carbon, carbon doped with germanium, and germanium doped with carbon), and carbon-tin combinations (e.g., carbon-coated tin, tin-coated carbon, carbon doped with tin, and tin doped with carbon. Examples of positive electrochemically active materials include various lithium metal oxides (e.g., LiCoO.sub.2, LiFePO.sub.4, LiMnO.sub.2, LiNiO.sub.2, LiMn.sub.2O.sub.4, LiCoPO.sub.4, LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2, LiNi.sub.XCo.sub.YAl.sub.ZO2, LiFe.sub.2(SO4).sub.3), carbon fluoride, metal fluoride, metal oxide, sulfur, and combination thereof. Doped and non-stoichiometric variations of these materials may be used as well. Examples of dopant includes elements from the groups III and V of the periodic table (e.g., boron, aluminum, gallium, indium, thallium, phosphorous, arsenic, antimony, and bismuth) as well as other materials (e.g., sulfur and selenium). In certain embodiments, one or more dopants have concentration of between about 10.sup.14 and 10.sup.19 atoms per centimeter cubed. In other embodiments, one or more dopants have concentration of between about 10.sup.19 and 10.sup.21 atoms per centimeter cubed. In yet another embodiment, concentration is between about 10.sup.21 and 10.sup.23 atoms per centimeter cubed.
A nanostructure may include different materials (both active and non-active) and distribution of these materials within the nanostructure may vary as well. For example, each material may form its own layer within a nanostructure. One example is a nanostructure where one material forms a "core" and another material forms a "shell" around the core. The nanostructure may have multiple shells. It should be understood that any number of concentric shells may be used. Furthermore, a core may be a hollow (e.g., tube-like) structure. Typically, at least one of the materials in a core-shell is an active material. In one embodiment, a core-shell structure forms nested layers in a rod or wire, where one layer is surrounded by another outer layer, e.g., forming a set of concentric cylinders. In other embodiments, each layer of the nanostructure is a sheet that is rolled around itself and other layers to form a spiral. For simplicity, each of these embodiments is referred to as a core-shell structure.
Particular examples of core-shell structures deposited with the above described methods and apparatus include: crystalline silicon core/amorphous silicon shell, nickel silicide core/amorphous silicon shell, carbon core/silicon shell, silicon core/carbon shell, and carbon core/silicon inner shell/carbon outer shell. More detailed description of core-shell structures is provided in U.S. patent application Ser. No. 12/787,168 entitled "CORE-SHELL HIGH CAPACITY NANOWIRES FOR BATTERY ELECTRODES" filed on May 25, 2010, which is incorporated herein by reference in its entirety for purposes of describing core-shell structures.
In certain embodiments, a "nanowire" is defined as a structure that has, on average, an aspect ratio of at least about four. In certain examples, the average aspect ratio may be at least about ten, at least about one hundred, or even at least about one thousand. In some cases, the average nanowire aspect ratio may be at least about ten thousand, and can even reach about one hundred thousand. Nanowire active materials can undergo substantial swelling without disrupting the overall structure of the active layer, provide better electrical and mechanical connections with the layer, and can be easily realized using the vapor-liquid-solid and vapor-solid template free growth methods or other templated methods. Nanowires can be terminally rooted to the substrate to form an active layer as illustrated.
In certain embodiments, apparatuses and methods described above are used to deposit intermediate layers onto a web prior to depositing electrochemically active materials. One or more intermediates layers may be used to protect the substrate from reactants used to deposit active materials, to facilitate deposition of active materials (e.g., contain a catalyst), to facilitate catalyst or active material distribution over the substrate surface (e.g., forming catalyst islands/nanowires), to enhance bonding between the substrate and active materials during deposition and operation of electrochemical cells, and other purposes. Additional examples and description of intermediate layers are presented in U.S. Application 61/260,297 entitled "INTERMEDIATE LAYERS FOR ELECTRODE FABRICATION" filed on Nov. 11, 2009, which incorporated herein by reference in its entirety for purposes of describing intermediate layers.
FIG. 7 illustrates an example of a process 700 used for depositing substrate rooted silicon nanowires in apparatuses described above. The process 700 may start with preheating a web (block 702) to a predetermined temperature (e.g., at least about 400.degree. C.). Crystalline silicon nanowires may be then grown on both sides of the web using thermal CVD (block 704). For example, silane mixed with hydrogen and inert diluents may be injected into the deposition station. The process may continue with PECVD, LACVD, or other deposition technique to coat the nanowires with amorphous silicon (block 706). For example, silane may be cracked in the gas phase by additional energy input (e.g., plasma) to promote very rapid deposition of onto the existing nanowire structures. The web may be then cooled down and feed to other stations for additional processing or wound onto a take-up roll. In particular embodiments, there is no contact between the web and any hardware elements of the apparatus during operations 704, 706, and 708.
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