Patent Publication Number: US-2011070488-A1

Title: High performance electrodes

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/244,826 filed Sep. 22, 2009, and U.S. Provisional Application No. 61/245,121 filed Sep. 23, 2009, which are both hereby incorporated by reference herein in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to forming electrodes, and more particularly to techniques for forming electrodes containing nanostructured materials. 
     BACKGROUND OF THE INVENTION 
     Electrodes are used to supply and remove electrons from some medium, and are typically manufactured from metals or metal alloys. Electrochemical cells use electrodes to facilitate electron transport and transfer during electrochemical interactions. Batteries, or electrochemical storage devices, may use electrodes in both galvanic and electrolytic capacities, corresponding to discharging or charging processes, respectively. Electrochemical reactions generally occur at or near the interfaces of an electrolyte and the electrodes, which may extend to an external circuit through which electric power can be applied or extracted. Electrodes are typically placed in contact with current collectors in order to draw and/or supply electrical power. 
     Mechanical and chemical processes are typically used to manufacture electrodes that feature desired performance metrics such as charging/discharging rates or cycle life. These performance metrics often depend on the materials that are used. Moreover, some electrochemical materials undergo volumetric change during charging or discharging processes. For example, the volumetric change between some active materials may be as much as several hundred percent. This may impart substantial stresses and strains on the electrodes. Repeated volumetric changes of these active materials may lead to pulverization and reduced electrode cycle life. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, techniques, compositions, and arrangements are provided for incorporating nanostructured materials into electrodes. In some embodiments, nanostructured materials are added to slurries or other mixtures to form electrodes. In some embodiments, nanostructured materials are deposited directly onto surfaces of electrode components. In some approaches, the use of nanostructured materials in electrodes may modify properties of electrodes. For example, in some embodiments, carbon nanotubes may be incorporated into electrodes to increase electronic conductivity, thermal conductivity, durability, any other suitable property or suitable combination of properties thereof. Moreover, in some approaches, the use of nanostructured materials in electrodes may reduce volumetric changes during charging and discharging. 
     In some embodiments, a slurry may be prepared by combining one or more active materials, electronically conductive materials, binders, liquid agents, or other suitable materials or suitable combinations thereof. One or more of the components of the slurry may be a nanostructured material including nanostructured elements such as, for example, nanoparticles (e.g., LiMPO 4 , LiMO 2 , in which “M” is any suitable metal), nanowires (e.g., silicon nanowires, zinc nanowires), single-walled or multi-walled nanotubes (e.g., carbon nanotubes), closed fullerenes (e.g., C60 buckminsterfullerene), any other suitable nanostructured elements, any suitable nanostructured composite elements or any suitable combinations or arrays thereof. The slurry may be placed in contact with or otherwise applied to an electrode component such as, for example, a metallized foam, substrate, any other electrode component or subassembly of components, or any suitable combinations thereof. At least one substantially contiguous layer of the slurry may be formed on one more surfaces of the electrode component. The layers may be uniform or non-uniform in thickness and may be contiguous or non-contiguous on the one or more surfaces of the electrode component. In some embodiments, more than one contiguous layer may be formed on a particular surface of the electrode component. The slurry may be dried on the electrode component, forming an electrode. Drying may require substantially all (i.e., all or almost all) of the liquid agent to be removed from the at least one contiguous layer of the slurry to leave a solid material, which may remain in contact with the surface of the electrode component. The electrode may be sized, calendared, treated, or otherwise processed before or after drying. 
     In some embodiments, a plurality of active material particles may be modified with one or more nanostructured materials. Active material particles may be coated with any suitable material such as, for example, iron (Fe), aluminum (Al), alumina (Al 2 O 3 ), manganese salts, magnesium salts, silicon (Si), any other suitable material or any suitable combination thereof, to aid in forming nanostructures on the active material particles. Deposition techniques (e.g., chemical vapor deposition, physical vapor deposition, electrophoresis) may be used to form nanostructured materials on coated active materials. The deposition technique may include introducing a precursor such as, for example, hydrocarbons, hydrogen, silanes (e.g., SiH 4 ), inert species, or other suitable precursors or mixtures thereof, to the coated particles. Nanostructured materials may include arrays of nanostructured elements such as, for example, nanoparticles (e.g., LiFePO 4  nanoparticles), nanowires (e.g., silicon nanowires, zinc nanowires), single-walled or multi-walled nanotubes (e.g., carbon nanotubes), closed fullerenes, any other suitable nanostructured elements, any suitable nanostructured composite elements or any suitable combinations thereof. Active material particles that have been modified by deposition of nanostructured materials may be included in a slurry, which may be applied to an electrode component and dried to form an electrode. 
     In some embodiments, an electrode component may be modified with one or more nanostructured materials. Electrode components may be coated with any suitable material, or combinations of materials, which may act as a catalyst for deposition of nanostructured materials. Deposition techniques (e.g., chemical vapor deposition, physical vapor deposition, electrophoresis) may be used to form nanostructured materials on coated electrode components. The deposition technique may include introducing a precursor such as, for example, hydrocarbons, hydrogen, silanes (e.g., SiH 4 ), inert species, or other suitable precursors or mixtures thereof, to the coated electrode component. Nanostructured materials may include arrays of nanostructured elements such as, for example, nanoparticles (e.g., LiFePO 4  nanoparticles), nanowires (e.g., silicon nanowires, zinc nanowires), single-walled or multi-walled nanotubes (e.g., carbon nanotubes), closed fullerenes, any other suitable nanostructured elements, any suitable nanostructured composite elements or any suitable combinations thereof. Active materials may be added to electrode components that have been modified by deposition of nanostructured materials. In some embodiments, active materials may be included in a slurry that is applied to an electrode component and dried to form an electrode. Active materials may be added before or after modification of the electrode component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  shows a schematic cross-sectional view of an illustrative structure of a bi-polar electrode unit (BPU) in accordance with some embodiments of the present invention; 
         FIG. 2  shows a schematic cross-sectional view of an illustrative structure of a stack of BPUs of  FIG. 1  in accordance with some embodiments of the present invention; 
         FIG. 3  shows a schematic cross-sectional view of an illustrative structure of a mono-polar electrode unit (MPU) in accordance with some embodiments of the present invention; 
         FIG. 4  shows a schematic cross-sectional view of an illustrative structure of a device containing two MPUs of  FIG. 3  in accordance with some embodiments of the present invention; 
         FIG. 5  shows a diagram of illustrative transport processes at an active interface in accordance with some embodiments of the present invention; 
         FIG. 6  shows an illustrative partial cross-section schematic view of an active interface region in accordance with some embodiments of the present invention; 
         FIG. 7  shows an illustrative electrode structure with a cutaway section in accordance with some embodiments of the present invention; 
         FIG. 8  shows side elevation views of two illustrative electrode structures in accordance with some embodiments of the present invention; 
         FIG. 9  shows an illustrative diagram of nanostructured materials in accordance with some embodiments of the present invention; 
         FIG. 10  shows an illustrative diagram of nanostructured materials in accordance with some embodiments of the present invention; 
         FIG. 11  is a flow diagram of illustrative steps for forming electrodes in accordance with some embodiments of the present invention; 
         FIG. 12  is a flow diagram of illustrative steps for forming electrodes in accordance with some embodiments of the present invention; 
         FIG. 13  is a flow diagram of illustrative steps for forming modified particles in accordance with some embodiments of the present invention; 
         FIG. 14  is a flow diagram of illustrative steps for forming electrodes in accordance with some embodiments of the present invention; 
         FIG. 15  is a flow diagram of illustrative steps for forming electrodes in accordance with some embodiments of the present invention; 
         FIG. 16  shows an illustrative side elevation view of a slurry in contact with a substrate in accordance with some embodiments of the present invention; 
         FIG. 17  shows an illustrative top plan view of the elements of  FIG. 16 , taken from line XVII-XVII, in accordance with some embodiments of the present invention; 
         FIGS. 18 and 19  show illustrative particles undergoing modification in accordance with some embodiments of the present invention; 
         FIG. 20  shows an illustrative side elevation view of an electrode component in contact with a substrate in accordance with some embodiments of the present invention; 
         FIG. 21  shows an illustrative top plan view of the elements of  FIG. 20 , taken from line XXI-XXI, in accordance with some embodiments of the present invention; and 
         FIG. 22  shows several illustrative partial cross-sectional views of an electrode component in accordance with some embodiments or the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides techniques, compositions, and arrangements for forming electrodes and electrode structures that include nanostructured materials. In some embodiments, the nanostructured materials may be formed directly on electrodes or electrode components. The nanostructured materials may be active materials, electronically conducting materials, any other suitable materials or any suitable combinations thereof for use in energy storage devices (ESDs). The electrode structures and assemblies of the present invention may be applied to energy storage devices such as, for example, batteries, capacitors or any other energy storage device which may store or provide electrical energy or current, or any combination thereof. For example, the electrode structures and assemblies of the present invention may be implemented in a mono-polar electrode unit (MPU) or a bi-polar electrode unit (BPU), and may be applied to one or more surfaces of the MPU or BPU. It will be understood that while the present invention is described herein in the context of stacked energy storage devices, the concepts discussed are applicable to any intercellular electrode configuration including, but not limited to, parallel plate, prismatic, folded, wound and/or bipolar configurations, any other suitable configurations or any combinations thereof. 
     In some embodiments, electrodes may contain nanostructured materials to increase active interface area, and to improve transport of molecules (e.g., water), ions (e.g., hydroxyl anions), electrons, or any combination thereof to the interface area. For example, carbon nanotubes (CNTs) may be added to electrodes to increase active interface area and improve electronic conductivity. Electrochemical reactions may occur at or near the interface area between an active material, an electrolyte and an electronically conducting component. Increased interface area may allow increased charge or discharge rates for electrochemical devices. 
     In some embodiments, electrodes may contain nanostructured materials to reduce volumetric changes during charging and discharging. Active materials may be nanostructured to reduce material stresses and strains that may develop from volumetric changes. For example, silicon nanowires (SiNWs) may be used as an active material (e.g., negative electrode material) in a lithium-ion ESD to reduce volumetric changes during lithium uptake, removal, or both. In some embodiments, electrodes containing SiNWs as an active material may undergo reduced volumetric change as a result of relative motion of the nanostructured material. 
     The present invention includes techniques, compositions, and arrangements for forming electronically conductive electrodes that include nanostructured materials. In some embodiments, the electrodes may be formed, for example, by combining nanostructured materials, or materials with nanostructured features, into a slurry which may applied to an electrode component, such as an electronically conductive substrate or metallized foam, for example, and dried. In some embodiments, materials may be modified, for example, by depositing nanostructured materials onto suitable surfaces of materials, particles, components, other surfaces, or combinations of surfaces. In some embodiments, the electrodes may be formed, for example, by depositing nanostructured materials onto the surfaces of electrode components such as electronically conductive substrates or metallized foams, or other suitable components or combinations of components. Active materials may be introduced to the electrodes or electrode components before, after, or during deposition of nanostructured materials. 
     The invention will now be described in the context of  FIGS. 1-22 , which show illustrative embodiments. 
       FIG. 1  shows a schematic cross-sectional view of an illustrative structure of BPU  100  in accordance with some embodiments of the present invention. Exemplary BPU  100  may include a positive active material electrode layer  104 , an electronically conductive, impermeable substrate  106 , and a negative active material electrode layer  108 . Positive electrode layer  104  and negative electrode layer  108  are provided on opposite sides of substrate  106 . 
       FIG. 2  shows a schematic cross-sectional view of an illustrative structure of a stack  200  of BPUs  100  of  FIG. 1  in accordance with some embodiments of the present invention. Multiple BPUs  202  may be arranged into stack configuration  200 . Within stack  200 , electrolyte layer  210  may be provided between two adjacent BPUs, such that positive electrode layer  204  of one BPU is opposed to negative electrode layer  208  of an adjacent BPU, with electrolyte layer  210  positioned between the BPUs. A separator may be provided in one or more electrolyte layers  210  to electrically separate opposing positive and negative electrode layers. The separator allows molecular and ionic transfer between the adjacent electrode units, but may substantially prevent electronic transfer between the adjacent electrode units. As defined herein, a “cell” or “cell segment”  222  refers to the components included in substrate  206  and positive electrode layer  204  of a first BPU  202 , negative electrode layer  208  and substrate  206  of a second BPU  202  adjacent to the first BPU  202 , and electrolyte layer  210  between the first and second BPUs  202 . Each impermeable substrate  206  of each cell segment  222  may be shared by applicable adjacent cell segment  222 . 
       FIG. 3  shows a schematic cross-sectional view of an illustrative structure of MPU  300  in accordance with some embodiments of the present invention. Exemplary MPU  300  may include active material electrode layer  304  and electronically conductive, impermeable substrate  306 . Active material layer  304  may be any suitable positive or negative active material. 
       FIG. 4  shows a schematic cross-sectional view of an illustrative structure of a device containing two MPUs of  FIG. 3  in accordance with some embodiments of the present invention. Two MPUs  300  having a positive and negative active material, respectively, may be stacked to form electrochemical device  400 . Electrolyte layer  410  may be provided between two MPUs  300 , such that positive electrode layer  404  of one MPU  300  is opposed to negative electrode layer  408  of the other MPU  300 , with electrolyte layer  410  positioned between the MPUs. A separator may be provided electrolyte layers  410  to electrically separate opposing positive and negative electrode layers. Although not shown, in some embodiments two MPUs having positive and negative active materials, respectively, may be added to stack  200  of  FIG. 2 , along with suitable layers of electrolyte, to form a bi-polar energy storage device. Bi-polar ESDs and ESD stacks are discussed in more detail in Ogg et al. U.S. Pat. No. 7,794,877, Ogg et al. U.S. patent application Ser. No. 12/069,793, and West et al. U.S. patent application Ser. No. 12/258,854, all of which are hereby incorporated by reference herein in their entireties. 
     The substrates used to form electrode units (e.g., substrates  106 ,  206 ,  406 , and  416 ) may be formed of any suitable electronically conductive and impermeable or substantially impermeable material, including, but not limited to, a non-perforated metal foil, aluminum foil, stainless steel foil, cladding material including nickel and aluminum, cladding material including copper and aluminum, nickel plated steel, nickel plated copper, nickel plated aluminum, gold, silver, any other suitable electronically conductive and impermeable material or any suitable combinations thereof. In some embodiments, substrates may be formed of one or more suitable metals or combination of metals (e.g., alloys, solid solutions, plated metals). Each substrate may be made of two or more sheets of metal foils adhered to one another, in certain embodiments. The substrate of each BPU may typically be between 0.025 and 5 millimeters thick, while the substrate of each MPU may be between 0.025 and 30 millimeters thick and act as terminals or sub-terminals to the ESD, for example. Metallized foam, for example, may be combined with any suitable substrate material in a flat metal film or foil, for example, such that resistance between active materials of a cell segment may be reduced by expanding the conductive matrix throughout the electrode. 
     The positive electrode layers provided on the substrates to form the electrode units of the invention (e.g., positive electrode layers  104 ,  204  and  404 ) may be formed of any suitable active material, including, but not limited to, nickel hydroxide (Ni(OH) 2 ), nickel oxyhydroxide (NiOOH), zinc (Zn), lithium iron phosphate (LiFePO 4 ), lithium manganese phosphate (LiMnPO 4 ), lithium cobalt oxide (LiCoO 2 ), lithium manganese oxide (LiMnO 2 ), any other suitable material, or combinations thereof, for example. The positive active material may be sintered and impregnated, coated with a suitable binder (e.g., aqueous, non-aqueous, organic, inorganic) and pressed, or contained by any other suitable technique for containing the positive active material with other supporting chemicals in a conductive matrix. The positive electrode layer of the electrode unit may have particles, including, but not limited to, metal hydride (MH), palladium (Pd), silver (Ag), any other suitable material, or combinations thereof, infused in its matrix to reduce swelling, for example. This may increase cycle life, improve recombination, and reduce pressure within the cell segment, for example. These particles, such as MH, may also be in a bonding of the active material paste, such as Ni(OH) 2 , to improve the electrical conductivity within the electrode and to support recombination. 
     The negative electrode layers provided on the substrates to form the electrode units of the invention (e.g., negative electrode layers  108 ,  208 , and  408 ) may be formed of any suitable active material, including, but not limited to, MH, cadmium (Cd), manganese (Mn), Ag, carbon (C), silicon (Si), silicon-carbon composites, silicon carbide (SiC), any other suitable material, or combinations thereof, for example. The negative active material may be sintered, coated with an aqueous binder and pressed, coated with an organic binder and pressed, or contained by any other suitable technique for containing the negative active material with other supporting chemicals in a conductive matrix, for example. The negative electrode side may have chemicals including, but not limited to, Ni, Zn, Al, any other suitable material, or combinations thereof, infused within the negative electrode material matrix to stabilize the structure, reduce oxidation, and extend cycle life, for example. 
     Various suitable binders, including, but not limited to, organic carboxymethylcellulose (CMC), Creyton rubber, PTFE (Teflon), polyvinylidene fluoride (PVDF), any other suitable material or any suitable combinations thereof, for example, may be mixed with or otherwise introduced to the active material to maintain contact between the active material and a substrate, solid-phase foam, any other suitable component, or any suitable combination thereof. Any suitable binders may be included in slurries or any other mixtures to increase adherence, cohesion or other suitable property or combination thereof. In some embodiments, n-methyl-2-pyrrolidone (NMP) may be used as liquid agent (e.g., a solvent) in slurries. 
     The separator of each electrolyte layer of an ESD may be formed of any suitable material that electrically isolates its two adjacent electrode units while allowing ionic transfer between those electrode units. The separator may contain cellulose super absorbers to improve filling and act as an electrolyte reservoir to increase cycle life, wherein the separator may be made of a polyabsorb diaper material, for example. The separator may, thereby, release previously absorbed electrolyte when charge is applied to the ESD. In certain embodiments, the separator may be of a lower density and thicker than normal cells so that the inter-electrode spacing (IES) may start higher than normal and be continually reduced to maintain the capacity (or C-rate) of the ESD over its life as well as to extend the life of the ESD. 
     The separator may be a relatively thin material bonded to the surface of the active material on the electrode units to reduce shorting and improve transport mechanics. This separator material may be sprayed on, coated on, pressed on, or combinations thereof, for example. The separator may have a recombination agent attached thereto. This agent may be infused within the structure of the separator (e.g., this may be done by physically trapping the agent in a wet process using a polyvinyl alcohol (PVA or PVOH) to bind the agent to the separator fibers, or the agent may be put therein by electro-deposition), or it may be layered on the surface by vapor deposition, for example. The separator may be made of any suitable material such as, for example, polypropylene, polyethylene, any other suitable material or any combinations thereof. The separator may include an agent that effectively supports recombination, including, but not limited to, lead (Pb), Ag, platinum (Pt), Pd, any other suitable material, or any suitable combinations thereof, for example. In some embodiments, an agent may be substantially insulated from (e.g., not contact) any electronically conductive component or material. For example, the agent may be positioned between sheets of the separator material such that the agent does not contact electronically conductive electrodes or substrates. While the separator may present a resistance if the substrates of a cell move toward each other, a separator may not be provided in certain embodiments of the invention that may utilize substrates stiff enough not to deflect. 
     The electrolyte of each electrolyte layer of an ESD may be formed of any suitable chemical compound that may ionize when dissolved or molten to produce an electrically conductive medium. The electrolyte may be a standard electrolyte of any suitable ESD, including, but not limited to, NiMH and lithium-ion ESDs, for example. The electrolyte in a lithium-ion based ESD may include, for example, ethylene carbonate (C 3 H 4 O 3 ), diethyl carbonate (C 5 H 10 O 3 ), lithium hexafluorophosphate (LiPF 6 ), any other suitable lithium salt, any other organic solvent, any other suitable material or any suitable combination thereof. The electrolyte in a NiMH based ESD may be, for example, an aqueous solution. The electrolyte may contain additional suitable materials, including, but not limited to, lithium hydroxide (LiOH), sodium hydroxide (NaOH), calcium hydroxide (CaOH), potassium hydroxide (KOH), any other suitable metal hydroxide, any other suitable material, or combinations thereof, for example. The electrolyte may also contain additives to improve recombination, including, but not limited to, Pt, Pd, any suitable metal oxides (e.g., Ag 2 O), any other suitable additives, or any combination thereof, for example. The electrolyte may also contain rubidium hydroxide (RbOH), or any other suitable material, for example, to improve low temperature performance. The electrolyte may be frozen within the separator and then thawed after the ESD is completely assembled. This may allow for particularly viscous electrolytes to be inserted into the electrode unit stack of the ESD before the gaskets have formed substantially fluid tight seals with the electrode units adjacent thereto. 
     Electrodes may contain an electronically conductive network or component. The electronically conductive network or component may be an electronically conductive foam (e.g., metal-plated foam), collection of contacting electronically conductive particles (e.g., sintered metal particles), array of nanostructured material (e.g., array of CNTs), any other electronically conductive material, component, or network, or any suitable combinations thereof. The electronically conductive network or component may reduce ohmic resistance and may allow increased interface area for electrochemical interactions. For example, in stack  400  shown in  FIG. 4 , the interface between electrolyte  410  and positive electrode layer  404 , and the interface between electrolyte  410  and negative electrode layer  408 , appear to be a planar, two dimensional surfaces. While a planar interface may be employed in some embodiments of energy storage devices, the electrode may also have porous structure with substantially three-dimensional surface. The porous structure may increase the interface area between electrode and electrolyte, which may therefore increase the achievable charge or discharge rate. Active materials may be mixed with or applied to the conductive component or network to extend the interface over a greater surface area. Electrochemical interactions may occur at the interface between an active material, an electrolyte, and an electronically conductive material. 
     The electronically conductive substrate may be impermeable, preventing leakage or short circuiting for example. In some arrangements, one or more porous electrodes may be maintained in contact with a substrate, as shown in  FIGS. 1-4 . This arrangement may allow for electronic transfer among an external circuit and the electrode. 
       FIG. 5  shows illustrative transport diagram  500  in accordance with some embodiments of the present invention. Electrons, ions, and molecules may be transported to and from active interface  502 , located at the intersection of an active material, electronically conductive material, and an electrolyte phase. The charge and discharge rate of ESDs may increase as the area of active interface  502  increases. Active interface  502  may represent the active surface area of active materials within ESDs. Electrochemical reactions may occur at active interface  502 . In some embodiments, nanostructured materials may increase the active surface area, thereby increasing charge and discharge rates. Nanostructured materials may, for example, increase transport rates by increasing active surface area. In some embodiments, the use of nanostructured materials may improve electrode performance by improving properties such as, for example, electronic conductivity, thermal conductivity, durability, any other suitable property or any suitable combinations thereof. 
     Electrons may be transported between electronically conductive region  506  (e.g., metallized foam, substrate  106 ,  206 ,  306 ,  406 , or  416 ) and active interface  502  along path  504 , which may represent a path through a contiguous, electronically conductive material or combination of materials. Conduction electrons may be transported between electronically conductive region  506  and external circuit  510  along path  508 , which may represent a path through a contiguous, electronically conductive material or combination of materials (e.g., metal wires, circuitry). Ions (e.g., hydroxyl anion, lithium cation) may undergo transport (e.g., migration, diffusion) between electrolyte region  516  (e.g., electrolyte  210 ,  410 ) and active interface  502  along path  514 , which may represent a path through a substantially contiguous electrolyte material which may be solid or liquid. For example, during charging or discharging of lithium-ion-based ESDs, lithium cations may be transported through an electrolyte to and from active interfaces by diffusion, migration, or both. Compounds may undergo transport between bulk compound region  526  (e.g., bulk active material, bulk electrolyte, bulk gas phase) and active interface  502  along path  524 , which may represent a path through a substantially contiguous medium or combination of mediums which may allow suitable molecular transport (e.g., electrolyte, active materials). For example, during charging or discharging of NiMH-based ESDs, water may diffuse to and from active interfaces due to concentration gradients in an aqueous electrolyte. In some embodiments, electrons, ions, compounds, or suitable combinations thereof, may undergo transport within the same material (e.g., mixed conductor) or suitable combination of materials. The term “bulk” as used herein shall refer to regions of material away from nano-scale interfaces or nanostructures (e.g., reservoirs, non-nanostructured materials). The term “active interface” as used herein shall refer to area or region in space at or near interfaces in which electrochemical reactions substantially occur. The term “transport” as used herein shall refer to net spatial movement of electrons, ions, atoms, molecules, particles, or collections and combinations thereof, in response to gradients in physical quantities (e.g., pressure, concentration, temperature, electronic potential, chemical potential), including phenomenon such as diffusion, migration, convection, surface diffusion, and any other suitable mechanism. 
       FIG. 6  shows illustrative partial cross-sectional schematic view of interface region  600  in accordance with some embodiments of the present invention. Interface region  600  may include substrate  608 , active material  604 , electronically conductive material  606 , and pore network  620 . Active interface  602  (dotted region) may represent the area at or near the intersection of active material  604 , electronically conductive material  606 , and electrolyte (not shown, but which may substantially fill pore network  620 ). In some embodiments, active interface  602  may correspond to, or represent a close-up view of, active interface  502  described in  FIG. 5 . It will be understood that an illustrative, schematic two dimensional section representation of a three dimensional porous solid, such as that shown by  FIG. 6 , may not show some connectivity of the solids (or pores) but that connectivity may nonetheless exist. 
     Electrons may undergo transport between active interface  602 , electronically conductive material  606  (e.g., electronic conduction region  506  of  FIG. 5 ), and electronically conductive substrate  608  (e.g., electronic conduction region  506  of  FIG. 5 ) via conduction path  610  (e.g., path  504  of  FIG. 5 ). Ions may undergo transport between active interface  602  and the bulk electrolyte, which resides in pore network  620 , via transport path  612  (e.g., path  514  of  FIG. 5 ). For example, hydroxyl anions (OH − ) may diffuse or migrate to and from active interface  602  via illustrative transport path  612  in pore network  620  which may be substantially filled with aqueous electrolyte. Any suitable ions, or combination of ions, in any suitable electrolyte may undergo transport along illustrative path  612 . Compounds may undergo transport between active interface  602  and one or more of active material  604  (via transport path  616 ), bulk electrolyte (via path  614 ) which may reside in pore network  620 , a gas phase region containing gaseous materials (not shown), any other material or region of material, or any suitable combination thereof. For example, water molecules may undergo transport to and from active interface  602  via diffusion along illustrative path  614  in pore network  620  which may be substantially filled with aqueous electrolyte. Any suitable compounds, or combination of compounds, in any suitable medium may undergo transport along illustrative path  614 . Transport paths  610 ,  612 , and  614  are illustrative, and are meant to represent nominal paths by which transport may occur. It will be understood that the actual paths of electrons, ions, and compounds may not follow these illustrative paths. It will also be understood that an illustrative, schematic two dimensional section representation of a three dimensional porous solid, such as that shown by  FIG. 6 , may not show some connectivity of the solids (or pores) but that connectivity may nonetheless exist. 
       FIG. 7  shows illustrative electrode structure  700  with a cutaway section in accordance with some embodiments of the present invention. Electrode structure  700  may include porous electrode  702  and non-porous substrate  706 . Electrode  702  and substrate  706  may share interface  710  as a plane of contact. Interface  610  represents the plane or path in space where at least two components, materials or suitable combination thereof meet in contact. The term “interface” as used herein describes the substantially planar area of contact between a slurry and a substrate, a solid foam and a substrate, any two suitable components, any suitable component and a non-solid phase, or any other plane of contact between two distinct materials or components. Although shown as a planar disk geometry, electrode structure  700  may have any suitable shape, curvature, thickness (of either layer), relative size (among substrate and foam), relative thickness (among substrate and foam), any other property or any suitable combination thereof. Electrode  702  may include one or more electronically conductive components (e.g., metals), one or more active materials (e.g., Ni(OH) 2 ), one or more binders, one or more nanostructured materials, any other suitable materials or any combination thereof. In some embodiments, active materials may be introduced to electrode  702  following assembly or creation of structure  700 . In some embodiments, nanostructured materials may be introduced to electrode  702  following assembly or creation of structure  700 . 
     Active materials may undergo significant volumetric expansion or contraction as a result of charging or discharging. The volumetric change may result from material phase transitions, intercalation of atoms or molecules within an active material, or other physical or chemical processes, or combinations thereof. For example, the volumetric change between active material silicon (Si) and lithium-silicon complexes (e.g., Li 4.4 Si) formed from lithium insertion and removal may be several hundred percent. 
       FIG. 8  shows side elevation views of illustrative electrode structures  800  and  850  in accordance with some embodiments of the present invention. Illustrative electrode  802  of electrode structure  800  may undergo a volumetric change, which may result in a size increase to outline  812 . Substrate  806  may not undergo substantial volumetric change, which may cause stresses and strains to develop during volumetric change of the electrode. Repeated expansion and contraction may lead electrode  802  to crumble or otherwise lose structural integrity. Repeated expansion and contraction may also lead electrode  802  to suffer reduced electronic conductivity, as the electronically conductive network in the electrode may be interrupted. Illustrative electrode  852  of electrode structure  850  may include nanostructured particles. The presence of nanostructured materials in electrode  852  may reduce volumetric changes of electrode  852  (as shown by outline  862 ), relative to electrode  802 , during charging and discharging. The presence of nanostructured materials (e.g., carbon nanotubes, silicon nanowires) in electrode  852  may allow relative motion and volumetric changes amongst regions within electrode  852 , which may reduce the stresses and strains that develop throughout electrode  852 . In some embodiments, reduction of stresses and strains within an electrode may cause, for example, a reduction in deformation, cracking, pulverization, leaking, and any other failure modes or combinations thereof, of electrode components. In some embodiments, incorporation of a nanostructured material an electrode may improve the durability and cycle life of the electrode during charging and discharging processes. 
       FIG. 9  shows illustrative diagram  900  of nanostructured materials in accordance with some embodiments of the present invention. The array of nanostructured material shown in diagram  900  may include one or more of nanostructured element  902 . Nanostructured element  902  may be a nanoparticle (e.g., LiFePO 4 , LiMnPO 4 , LiMnO 2  nanoparticle), nanowire (e.g., SiNW, ZnNW, SiC nanowire), single-walled or multi-walled nanotube (e.g., CNT), closed fullerene (e.g., C60 buckminsterfullerene), any other nanostructured element or any suitable combination thereof. In some embodiments, nanostructured element  902  may be a unit cell of a thin layer of nanostructured material, arranged into an array. For example, in some embodiments, nanostructured element  902  may be one unit cell of a graphene sheet, and a suitable array of these unit cells may collectively be a graphene sheet. One or more nanostructured elements  902  may be arranged in any orientation, or distribution of orientations. An array of nanostructured elements  902  may include elements with any suitable shape and size distribution. 
       FIG. 10  shows illustrative diagram  1000  of nanostructured materials in accordance with some embodiments of the present invention. Diagram  1000  may include one or more of nanostructured material  1030  (including illustrative nanostructured elements  1002  and  1003 ), coating  1040  (of coating material  1004 ), bulk surface  1050  (of bulk material  1006 ), and environment  1020 . In some embodiments, bulk material  1006  may be coated with coating material  1004 , which may assist in forming nanostructured elements such as, for example, nanostructured element  1002 . In some embodiments, coating material  1004  may act as a catalyst for deposition of nanostructured material  1030 . In some embodiments, a coating material may not be used, and nanostructured material  1030  may be deposited directly onto bulk surface  1050 . 
     Nanostructured elements may be arranged in any suitable orientation, or distribution of orientations, as shown by the different orientations of nanostructured elements  1002  and  1003 . In some embodiments, plasma-enhanced chemical vapor deposition (CVD) may be used to form nanostructured elements with a particular orientation (e.g., normal to the coating surface). In some embodiments, more than one nanostructured material may be deposited, and different nanostructured materials may have different orientations. For example, in some embodiments, SiNWs may be deposited onto a bulk Si surface, substantially normal to the bulk surface. An additional layer of CNTs may then be deposited among the SiNW array, substantially parallel to the bulk surface. Any suitable nanostructured material or combination of nanostructured materials, having any suitable orientations, may be deposited onto coating  1040  or bulk surface  1050 . 
     In some embodiments, environment  1020  may be controlled during deposition of nanostructured material  1030 . For example, in some embodiments, environment  1020  may be a reducing gaseous environment that may include hydrocarbons, hydrogen, silanes, inert gases, any other suitable gases or combinations thereof. Gaseous environments may include a precursor material which may deposit onto coating  1040  or bulk surface  1050 . In some embodiments, environment  1020  may be a liquid. The liquid may include, for example, suspended nanoparticles, nanowires, nanotubes, or other suitable nanostructured elements which may be deposited (e.g., by electrophoresis) onto coating  1040  or bulk surface  1050 . In some embodiments, environment  1020  may be a supercritical fluid, which may include a suitable precursor. Environment  1020  may include any suitable environmental conditions (e.g., temperature, pressure, composition) controlled by any suitable process schedule (e.g., flowrate, ramp times, hold times). 
       FIG. 11  shows illustrative flow diagram  1100  for forming electrodes in accordance with some embodiments of the present invention. At process step  1102  shown in  FIG. 11 , a slurry may be prepared including, for example, active materials (e.g., SiNWs, LiFePO 4 , MH, Ni(OH) 2 ), electronically conductive particles (e.g., CNTs, metal particles), one or more liquid agents (e.g., organic solvent, water, alcohol, NMP), binders (e.g., PTFE, PVDF), graphitic carbon, amorphous carbon, any other suitable materials, or any suitable combinations thereof. In some embodiments, the active materials may be particles with any suitable shape or size distribution. The electronically conductive particles may have any suitable shape or size distribution. In some embodiments, the electronically conducting particles and the active material particles may not necessarily be of the same size and shape. Process step  1102  may include mixing, blending, stirring, sonicating, ball milling, grinding, sizing (e.g., sieving), drying, any other suitable preparation process or any suitable combination thereof. For example, in some embodiments, process step  1102  may entail preparing a slurry including Si particles, carbon particles, an NMP aqueous solution, and PVDF particles to form a slurry. In some embodiments, for example, process step  1102  may entail preparing a slurry including LiFePO 4  particles, carbon particles, an NMP aqueous solution, and PVDF particles to form a slurry. The slurry prepared in accordance with process step  1102  may include any suitable combination of materials. 
     Process step  1103  may include preparing an electrode component onto which the slurry of process  1102  may be applied. The electrode component may include an electronically conductive substrate, an electronically nonconductive substrate, a metallized foam, any other suitable components, a subassembly of one or more components (e.g., metallized foam and substrate subassembly), and any suitable combinations thereof. Process step  1103  may include preparation steps such as cleaning the electrode component, adjusting the surface finish of the electrode component (e.g., polishing, roughening), etching the surface of electrode component, adjusting the size or shape of the electrode component (e.g., cutting, grinding, splitting, drilling, machining), any other suitable preparation steps or any suitable combination thereof. 
     At process step  1104  shown in  FIG. 11 , the slurry of process step  1102  may be applied to one or more surfaces of the electrode component of process step  1103 . Process step  1104  may include doctor-blading, spin coating, screen printing, any other suitable slurry application technique or any suitable combination thereof. In some embodiments one or more molds of any suitable shape may be used to maintain the slurry of process step  1102  in a particular shape on the electrode component of process step  1103 . For example, a rectangular prism mold in contact with a substrate may be used to maintain the slurry of process step  1102  in a rectangular prism shape while preventing the slurry of process step  1102  from flowing or otherwise deforming. In some embodiments, the slurry of process step  1102  may be dried prior to application to the electrode component. In some embodiments, a slurry may be tape-cast, dried, sized, any other suitable preparation step and any suitable combination thereof, prior to application to the electrode component. Application of a dried slurry to the electrode component may include bonding, or otherwise adhering the dried slurry to the electrode component. 
     At process step  1106  shown in  FIG. 11 , the slurry in contact with the electrode component may be dried (e.g., some fraction or substantially all of one or more liquid components may be removed). Drying process  1106  may impart rigidity to the residual components (e.g., remaining slurry components). In some embodiments, drying process  1106  may allow for the residual components to maintain shape such that the mold, if used, may be removed. In some embodiments, drying process  1106  may form a gas-filled porous network throughout the dried slurry. In some embodiments, drying process  1106  may include heating, immersing the electrode component and slurry in a prescribed gaseous environment (e.g., heated argon), any other suitable drying process or combination thereof. Process step  1106  may be skipped in some embodiments, such as, for example, embodiments in which the slurry is dried prior to application to the electrode component. 
     The electrode component in contact with the dried slurry of process  1106 , may be sized, shaped, or both, in accordance with process step  1108 . Process step  1108  may include punching (with any suitable die and press), bending, folding, trimming, shaving, calendering, machining, any other suitable sizing or shaping technique, or any suitable combinations thereof. In some embodiments, process step  1108  may be omitted. For example, in some embodiments the electrode component may be sized or formed as desired at process step  1103 , and further sizing or shaping may not be desired at process step  1108 . 
     Process step  1110 , as shown in  FIG. 11 , may include further processing of the electrode component. Process step  1110  may include chemical treatment such as, for example, applying a hydrophobic coating (e.g., PTFE) to the electrode component. Application of a hydrophobic coating may reduce flooding (e.g., buildup of liquid water) within the porous electrode. Process step  1110  may include chemical vapor deposition (CVD), physical vapor deposition (PVD), any other deposition technique or any suitable combination thereof, of one or more suitable materials to the surface of the electrode component. In some embodiments, process step  1110  may include, for example, sintering, charging discharging, any other suitable processing or any suitable combination thereof. Process step  1110  may include techniques to adjust the surface properties of the electrode component. 
       FIG. 12  shows illustrative flow diagram  1200  for forming electrodes in accordance with some embodiments of the present invention. The processes of flow diagram  1200  may include modifying the surface of electrode components, which may increase interface area, electronic conductivity, porosity, any other suitable property or any suitable combination thereof. 
     Process step  1202 , as shown in  FIG. 12 , may include preparing an electrode component. The electrode component may include an electronically conductive substrate, an electronically nonconductive substrate, a metallized foam, any other suitable components, a subassembly of one or more components (e.g., metallized foam and substrate subassembly), and any suitable combinations thereof. Process step  1202  may include preparation steps such as cleaning the electrode component, adjusting the surface finish of the electrode component (e.g., polishing, roughening), etching the surface of electrode component, adjusting the size or shape of the electrode component (e.g., cutting, grinding, splitting, drilling, machining), any other suitable preparation steps or any suitable combination thereof. In some embodiments, process step  1202  may include coating the surface of the electrode component with a catalyst, deposition substrate, any other suitable material or any suitable combination thereof. 
     A base matrix may be formed on the surface of the electrode component in accordance with process step  1204 , as shown in  FIG. 12 . The base matrix may be an array of nanostructured material (e.g., CNT array, SiNW array, ZnNW array), which may have, for example, an increased surface area relative to the electrode component without the base matrix. Process step  1204  may include chemical vapor deposition (CVD), plasma-enhanced CVD, physical vapor deposition (PVD), any other suitable deposition technique or any suitable combination thereof, of one or more suitable materials to the surface of the electrode component, thereby forming the base matrix. 
     A second material may be introduced to the base matrix of the electrode component as shown by process step  1206  of  FIG. 12 . Process step  1206  may include chemical vapor deposition (CVD), physical vapor deposition (PVD), any other deposition technique or any suitable combination thereof, of one or more suitable materials to the base matrix. The second material may be an active material, an electronically conductive material, a nanostructured material, any other suitable material, and any suitable combinations thereof. For example, in some embodiments, process step  1204  may include depositing an array of CNTs onto an electrode component, and process step  1206  may include depositing an array of SiNWs onto the base matrix of CNTs. In some embodiments, for example, process step  1204  may include depositing an array of SiNWs onto an electrode component, and process step  1206  may include depositing an array of CNTs on the base matrix of SiNWs. 
     The electrode component may be sized, shaped, or both, in accordance with process step  1208 , as shown in  FIG. 12 . Process step  1208  may include punching (with any suitable die and press), bending, folding, trimming, shaving, calendering, machining, any other suitable sizing or shaping technique, or any suitable combinations thereof. In some embodiments, process step  1208  may be not be included. For example, in some embodiments the electrode component may be sized or formed as desired at process step  1202 , and further sizing or shaping may not be desired at process step  1208 . 
     Process step  1210 , as shown in  FIG. 12 , may include further processing of the electrode component. Process step  1210  may include chemical treatment such as, for example, applying a hydrophobic coating (e.g., PTFE) to the electrode component. Application of a hydrophobic coating may reduce flooding (e.g., buildup of liquid water) within the porous electrode. Process step  1210  may include chemical vapor deposition (CVD), physical vapor deposition (PVD), any other deposition technique or any suitable combination thereof, of one or more suitable materials onto the surface of the electrode component. Process step  1210  may include techniques to adjust the surface properties of the electrode component. In some embodiments, process step  1210  may include sintering, charging, discharging, any other suitable processing technique, and any suitable combination thereof applied to the electrode component. 
       FIG. 13  shows illustrative flow diagram  1300  for modifying active particles in accordance with some embodiments of the present invention. Active material particles may be coated with a material at process step  1302  of  FIG. 13 . Any suitable active material may be coated, including both negative electrode active materials and positive electrode active materials. Process step  1302  may include coating the active material particles with a material such as, for example, nickel (Ni), iron (Fe), aluminum (Al), alumina (Al 2 O 3 ), manganese salts, magnesium salts, Si, any other suitable material or any suitable combination thereof, to aide in forming nanostructures on the active material particles. The coating material may be dissolved in a liquid solution, which may be applied to the active material particles. The liquid solution may be any suitable liquid such as, for example, an acid solution. Process step  1302  may include immersion, electroplating, electroless plating, electrophoresis, sputtering, atomic layer deposition, chemical solution deposition (e.g., sol-gel process), CVD, PVD, any other suitable coating technique or any suitable combination thereof. In some embodiments, process step  1302  may not be used. For example, in some embodiments, the active material particles may be Si particles, and no coating may be desired. In some embodiments, the active material particles may be Si particles, and a coating material of CNTs may be desired. The active material particles and coating material may include any suitable material or combination of materials. Process step  1302  may include sizing, cleaning, etching, or other processing technique to prepare active material particles for application of the coating material. 
     Coated particles may be processed at process step  1304 . Process step  1304  may include sizing (e.g., sieving), sintering, annealing, agglomerating, drying, any other suitable processing technique or any suitable combination thereof. For example, in some embodiments, coated particles may be heated in a prescribed gaseous environment (e.g., inert, reducing) to improve durability, improve adherence, increase coating material grain size, any other suitable coating property or any suitable combinations thereof. 
     Nanostructured materials may be deposited onto coated particles in accordance with process step  1306 . Process step  1306  may include CVD, plasma-enhanced CVD, PVD, any other suitable technique for depositing nanostructured materials or any suitable combination thereof. Process step  1306  may include placing the coated particles in a deposition chamber, controlling the environment of the coated particles (e.g., maintaining a reducing environment), heating the coated particles, any other suitable technique for depositing a nanostructured material onto particles or any suitable combination thereof. Process step  1306  may include providing a gas phase precursor to the deposition chamber. The gas phase precursor may include, for example, a hydrocarbon, carbon monoxide, silane, any other suitable precursor or any suitable combination thereof. The gas phase precursor may be combined with any suitable gaseous material such as, for example, hydrogen, inert species (e.g., helium), any other suitable gas species or any suitable combination thereof. For example, in some embodiments, a gas mixture of hydrogen and one or more hydrocarbons may be introduced to particles in a deposition chamber, which may be maintained between 300 and 1200 degrees centigrade. In some embodiments, the precursor may be a solid phase material that may undergo thermal, laser, or other suitable treatment, or combinations thereof, to release material into the vapor phase. In some embodiments, the precursor material may be included in solution such as, for example, a supercritical mixture. In some embodiments, a suspension (e.g., solid particles in a liquid medium) including nanostructured material may be applied to coated particles to deposit nanostructured material onto the coated particles. For example, in some embodiments, electrophoresis may be used to apply nanostructured materials contained in a solution to the coated particles. Any suitable precursor, additional material, deposition temperature (e.g., ramp temperature, soak temperature), deposition pressure, other process control and any suitable combination thereof, may be used to deposit nanostructured materials onto particles. 
     In some embodiments, particles resulting from process step  1306  may have modified properties such as, for example, composition, electronic conductivity, thermal conductivity, surface area, surface morphology, size, any other suitable modified property or any combination thereof. In some embodiments, the modified particles resulting from process step  1306  may be used as active material particles in the slurry of process step  1102  of  FIG. 11 . 
     In some embodiments, all or some of the techniques of flow diagram  1300  may be repeated in any order to form more than one array of nanostructured materials on active material particles. Any suitable combination of active materials, coatings, nanostructured materials, other suitable materials or combination thereof may be used in accordance with the techniques of flow diagram  1300 . 
       FIG. 14  shows illustrative flow diagram  1400  for forming electrodes in accordance with some embodiments of the present invention. Process step  1402  may include introducing active materials to electrode components. Any suitable active material may be introduced to the electrode component, including negative electrode active materials, positive electrode active materials, or both (e.g., BPU). The electrode component may include an electronically conductive substrate, an electronically nonconductive substrate, a metallized foam, any other suitable components, a subassembly of one or more components (e.g., metallized foam and substrate subassembly), and any suitable combinations thereof. In some embodiments, the active material may be applied to the electrode component as a slurry (e.g., the process described in flow diagram  1100  of  FIG. 11 ). In some embodiments, the active material may be applied to the electrode component as a nanostructured material. For example, process step  1402  may include CVD, plasma-enhanced CVD, PVD, any other suitable technique for depositing nanostructured materials or any suitable combination thereof. Process step  1402  may include cleaning, etching, sintering, any other preparation technique or any suitable combination thereof, for introducing an active material to an electrode component. 
     The electrode component may be coated with a material at process step  1404  of  FIG. 14 . Process step  1404  may include coating the electrode component with a material such as, for example, Ni, Fe, Al, Al 2 O 3 , manganese salts, magnesium salts, Si, any other suitable material or any suitable combination thereof, to aide in forming nanostructures on the electrode component. The coating material may be dissolved in a liquid solution, which may be applied to the active material particles. The liquid solution may be any suitable liquid. Process step  1404  may include immersion, electroplating, electroless plating, electrophoresis, sputtering, atomic layer deposition, chemical solution deposition (e.g., sol-gel process), CVD, PVD, any other suitable coating technique or any suitable combination thereof. In some embodiments, process step  1404  may not be used. The electrode component, active material, and coating material may include any suitable material or combination of materials. Process step  1404  may include sizing, cleaning, etching, or other processing technique to prepare the electrode component for application of the coating material. 
     The coated electrode component may be processed at process step  1406 . Process step  1406  may include sintering, annealing, drying, any other suitable processing technique or any suitable combination thereof. For example, in some embodiments, the coated electrode component may be heated in a prescribed gaseous environment (e.g., inert, reducing) to improve durability, improve adherence, increase coating material grain size, any other suitable coating property or any suitable combinations thereof. 
     Nanostructured materials may be deposited onto the coated electrode component in accordance with process step  1408 . Process step  1408  may include CVD, plasma-enhanced CVD, PVD, any other suitable technique for depositing nanostructured materials or any suitable combination thereof. Process step  1408  may include placing the electrode component in a deposition chamber, controlling the environment of the coated electrode component (e.g., maintaining a reducing environment), heating the coated electrode component, any other suitable technique for depositing a nanostructured material onto the electrode component or any suitable combination thereof. Process step  1408  may include providing a gas phase precursor to the deposition chamber. The gas phase precursor may include, for example, a hydrocarbon, carbon monoxide, silane, any other suitable precursor or any suitable combination thereof. The gas phase precursor may be combined with any suitable gaseous material such as, for example, hydrogen, inert species (e.g., helium), any other suitable gas species or any suitable combination thereof. For example, in some embodiments, a gas mixture of hydrogen and one or more hydrocarbons may be introduced to the coated electrode component in a deposition chamber, which may be maintained between 300 and 1200 degrees centigrade. In some embodiments, the precursor may be a solid phase material that may undergo thermal, laser, or other suitable treatment, or combinations thereof, to release material into the vapor phase. In some embodiments, the precursor material may be included in solution such as, for example, a supercritical mixture. In some embodiments, a suspension (e.g., solid particles in a liquid medium) including nanostructured material may be applied to a coated electrode component to deposit nanostructured material onto the coated electrode component. For example, in some embodiments, electrophoresis may be used to apply nanostructured materials contained in a solution to an electrode component. Any suitable precursor, additional material, deposition temperature (e.g., ramp temperature, soak temperature), deposition pressure, other process control and any suitable combination thereof, may be used to deposit nanostructured materials onto an electrode component. 
     The modified component that may result from process step  1408  may include an electronically conductive network (e.g., metallized foam, CNT array), an active material, a current collector (e.g., substrate, tab), any other suitable component or any suitable combination thereof. The modified component that may result from process step  1408  may be termed an electrode, BPU, MPU, electrode subassembly, or any other suitable designation. 
     For example, in some embodiments, an active material including metal hydrides (MHs) may be introduced to an electrode component including a Ni foam and an electronically conductive substrate, in accordance with process step  1402 . The active material may be included in a slurry which is applied to the electrode component (e.g., the slurry described in process step  1102  of  FIG. 11 ). The active material and electrode component may be sintered in accordance with process step  1402 . The electrode component and MH may be coated with a catalyst material in accordance with process step  1404 . The catalyst material coating may be dried and sintered in accordance with process step  1406 . The coated electrode component and MH may be placed in a CVD oven, and a hydrocarbon/hydrogen gaseous precursor may be introduced to the CVD oven at a temperature between 300 and 1600 degrees centigrade. An array of CNT may be deposited onto the coated electrode component and MH at process step  1408 . The array of CNTs may modify one or more properties of the electrode component, including, for example, electronic conductivity, thermal conductivity, surface area, any other suitable property or any combination thereof. This exemplary process in accordance with flow diagram  1400  is illustrative and is meant to illustrate some embodiments of the present invention, and not to limit the scope of the present invention. 
       FIG. 15  shows illustrative flow diagram  1500  for forming electrodes in accordance with some embodiments of the present invention. An electrode component may be coated with a material at process step  1502  of  FIG. 15 . In some embodiments, process step  1502  may correspond to process step  1404  of  FIG. 14 . Process step  1502  may include coating the electrode component with a material such as, for example, Ni, Fe, Al, Al 2 O 3 , manganese salts, magnesium salts, Si, any other suitable material or any suitable combination thereof, to aide in forming nanostructures on the electrode component. The coating material may be dissolved in a liquid solution, which may be applied to the active material particles. The liquid solution may be any suitable liquid. Process step  1502  may include immersion, electroplating, electroless plating, electrophoresis, sputtering, atomic layer deposition, chemical solution deposition (e.g., sol-gel process), CVD, PVD, any other suitable coating technique or any suitable combination thereof. In some embodiments, process step  1502  may not be used. The electrode component, active material, and coating material may include any suitable material or combination of materials. Process step  1502  may include sizing, cleaning, etching, or other processing technique to prepare the electrode component for application of the coating material. 
     The coated electrode component may be processed at process step  1504 . Process step  1504  may include sintering, annealing, drying, any other suitable processing technique or any suitable combination thereof. For example, in some embodiments, the coated electrode component may be heated in a prescribed gaseous environment (e.g., inert, reducing) to improve durability, improve adherence, increase coating material grain size, any other suitable coating property or any suitable combinations thereof. 
     Nanostructured materials may be deposited onto the coated electrode component in accordance with process step  1506 . In some embodiments, process step  1506  may correspond to process step  1408  of  FIG. 14 . Process step  1506  may include CVD, plasma-enhanced CVD, PVD, electrophoresis, any other suitable technique for depositing nanostructured materials or any suitable combination thereof. Process step  1506  may include placing the electrode component in a deposition chamber, controlling the environment of the coated electrode component, heating the coated electrode component, ablating a solid phase precursor, thermally treating a solid phase precursor, any other suitable technique for depositing a nanostructured material onto the electrode component or any suitable combination thereof. Process step  1506  may include providing a gas phase precursor to the deposition chamber, a solid phase precursor, or a precursor that may be included in solution. Any suitable precursor, additional material, deposition temperature (e.g., ramp temperature, soak temperature), deposition pressure, other process control and any suitable combination thereof, may be used to deposit nanostructured materials onto an electrode component. 
     Process step  1508  may include introducing active materials to a modified electrode component. In some embodiments, process step  1508  may correspond to process step  1402  of  FIG. 14 . Any suitable active material may be introduced to the electrode component, including negative electrode active materials, positive electrode active materials, or both (e.g., BPU). The electrode component may include an electronically conductive substrate, an electronically nonconductive substrate, a metallized foam, any other suitable components, a subassembly of one or more components (e.g., metallized foam and substrate subassembly), and any suitable combinations thereof. In some embodiments, the active material may be applied to the electrode component as a slurry (e.g., the process described in flow diagram  1100  of  FIG. 11 ). In some embodiments, the active material may be applied to the electrode component as a nanostructured material. For example, process step  1508  may include CVD, plasma-enhanced CVD, PVD, any other suitable technique for depositing nanostructured materials or any suitable combination thereof. Process step  1508  may include cleaning, etching, sintering, any other preparation technique or any suitable combination thereof, for introducing an active material to an electrode component. 
     For example, in some embodiments, one or more surfaces of an electrode component including a Ni foam rigidly affixed to an electronically conductive substrate may be coated with a catalyst in accordance with process step  1502 . The coated electrode component may be sintered in accordance with process step  1504 . The coated electrode component may be placed in a CVD oven, and a hydrocarbon/hydrogen precursor may be introduced to the CVD oven at a temperature between 600 and 1200 degrees centigrade. An array of CNTs may be deposited onto the coated electrode component at process step  1506 . An active material including, for example, Ni(OH) 2  may be added to the modified electrode component as a slurry (e.g., the slurry described in process step  1102  of  FIG. 11 ), which may be dried in accordance with process step  1508 . The array of CNTs may provide a base matrix (e.g., as described in process step  1204  of  FIG. 12 ) for application of the active material (e.g., Ni(OH) 2 ). This exemplary process in accordance with flow diagram  1500  is illustrative and is meant to illustrate some embodiments of the present invention, and not to limit the scope of the present invention. 
     It will be understood that the steps of flow diagrams  1100 - 1500  of  FIGS. 11-15  are illustrative. Any of the steps of flow diagrams  1100 - 1500  may be modified, omitted, rearranged, combined with other steps of flow diagrams  1100 - 1500 , or supplemented with additional steps, without departing from the scope of the present invention. 
     An illustrative process for making an electrode structure in accordance with some embodiments of the present invention will be discussed further in the context of  FIGS. 16 and 17 . 
       FIG. 16  shows an illustrative side elevation view of slurry  1602  in contact with substrate  1606  in accordance with some embodiments of the present invention. Shown in  FIG. 17  is an illustrative top plan view of the elements of  FIG. 16 , taken from line XVII-XVII of  FIG. 16  in accordance with some embodiments of the present invention. Slurry  1602  is shown in contact with substrate  1606  at interface  1610 . Substrate  1606  and slurry  1602  may have any suitable shape, cross-section shape, curvature (e.g., dome shaped), thickness (of either layer  1606  and  1602 ), relative size (among substrate and composite material), relative thickness (among substrate and composite material), any other property or any suitable combinations thereof. In some embodiments, slurry  1602  may include the slurry discussed above in process steps  1102  and  1104  of  FIG. 11 . In some embodiments, slurry  1602  may include the dried slurry discussed above in process step  1106  of  FIG. 11 . Slurry  1602  may include any material or suitable combination of materials. 
       FIG. 18  shows illustrative processes for modifying particles in accordance with some embodiments of the present invention. Illustrative particle  1800  may include active material  1802  as shown in  FIG. 18(I) . Active material  1802  may be positive active material, any other suitable materials or any combinations thereof, or active material  1802  may be negative active material, any other suitable materials or any combinations thereof. Although shown illustratively as spherical, particle  1800  may have any suitable shape or size, or both, and may belong to and be representative of a collection of active material particles having any suitable size and shape distribution. In some embodiments, particle  1800  may be porous, nonporous, cenospherical (e.g., hollow), any other morphological designation, or any suitable combination thereof. 
     Coating material  1824  may be introduced to particle  1800  (e.g., by process  1302  of  FIG. 13 ), forming coated particle  1820 , as shown in FIG.  18 (II). Coated active material  1802  may correspond substantially to active material  1802 . Coating material  1824  may include Fe, Al, Al 2 O 3 , manganese salts, magnesium salts, Si, any other suitable material or any suitable combination thereof, to aide in forming nanostructures on the coated particles. In some embodiments, coating material  1824  may cover substantially all of the surface of active material  1822 . In some embodiments coating material  1824  may cover part of the surface of active material  1802 . The coating formed by coating material  1824  may be contiguous or non-contiguous. The layer of coating material  1824  may be any suitable thickness. 
     Nanostructured material  1846  may be deposited onto the surface of coated particle  1820 , to form modified particle  1840  (e.g., as described by process step  1306  of  FIG. 13 ), as shown in FIG.  18 (III). Nanostructured material  1846  resides on coating material  1824  which may partially or substantially fully coat the surface of active material  1802 . Nanostructured material  1846  may be any suitable material or combination of materials, and may have any suitable orientation or distribution of orientations. For example, in some embodiments, nanostructured material  1846  may include an array of CNTs arranged substantially parallel to the surface of coating material  1824 . In some embodiments, for example, nanostructured material  1846  may include an array of ZnNWs arranged substantially normal to the surface of coating material  1824 . In some embodiments, nanostructured material  1846  may include more than one material. For example, in some embodiments, an array of SiNWs may be deposited on coating material  1824 , and an array of CNTs may be deposited on top of the array of SiNWs. Any suitable number of nanostructured materials, arrays of nanostructured materials, layers, or suitable combinations thereof may be deposited onto particle  1820  in any suitable order to form modified particle  1840 . 
     Modified particle  1840  may be combined with other modified particles, other particles or both, as shown by modified particle collection  1860  in FIG.  18 (IV). Modified particle collection  1860  may include modified particles  1840  and particles  1870 , which may include, for example, polymer particles, active material particles, electronically conductive particles (e.g., metal particles, CNTs), any other suitable particles or any suitable combinations thereof. Modified particle collection  1860  may be a slurry, and may include a liquid agent (not shown in  FIG. 18 ). Modified particle collection  1860  may have modified properties relative to a collection of non-modified particles such as, for example, increased electronic conductivity, increased thermal conductivity, increased surface area, increased inter-particle contact area (e.g., contact area  1868  of  FIG. 18 ), any other suitable property or combination thereof. Modified particle collection  1860  may be included in the slurry of flow diagram  1100  of  FIG. 11 . 
       FIG. 19  shows illustrative processes for modifying particles in accordance with some embodiments of the present invention. Illustrative particle  1900  includes active material  1902  as shown in  FIG. 19(I) . Active material  1902  may be any suitable positive active material or negative active material, or any suitable combination of materials thereof. Although shown illustratively as spherical, particle  1900  may have any suitable shape and size, or both, and may belong to and be representative of a collection of active material particles having any suitable size and shape distribution. In some embodiments, particle  1900  may be porous, nonporous, cenospherical (e.g., hollow), any other morphological designation, or any suitable combination thereof. 
     Nanostructured material  1946  may be deposited onto the surface of active material particle  1900 , to form modified particle  1940  (e.g., as described by process step  1306  of  FIG. 13 ), as shown in FIG.  19 (II). Nanostructured material  1946  may reside on the surface of active material  1902 . Nanostructured material  1946  may be any suitable material or combination of materials, and may have any suitable orientation or distribution of orientations. For example, in some embodiments, nanostructured material  1946  may include an array of CNTs arranged substantially parallel to the surface of active material  1902 . In some embodiments, for example, nanostructured material  1946  may include an array of SiNWs arranged substantially normal to the surface of active material  1902 . In some embodiments, nanostructured material  1946  may include more than one material. For example, in some embodiments, an array of ZnNWs may be deposited on active material  1902 , and an array of CNTs may be deposited on top of the array of ZnNWs. Any suitable number of nanostructured materials, arrays of nanostructured materials, layers, or suitable combinations thereof may be deposited onto particle  1900  in any suitable order to form modified particle  1940 . 
     Modified particle  1940  may be combined with other modified particles, other particles or both, as shown by modified particle collection  1960  in FIG.  19 (III). Modified particle collection  1960  may include modified particles  1940  and particles  1970 , which may include, for example, polymer particles, active material particles, electronically conductive particles (e.g., metal particles, CNTs), any other suitable particles or any suitable combinations thereof. Modified particle collection  1960  may be a slurry, and may include a liquid agent (not shown in  FIG. 19 ). Modified particle collection  1960  may have modified properties relative to a collection of non-modified particles such as, for example, increased electronic conductivity, increased thermal conductivity, increased surface area, increased inter-particle contact area (e.g., contact area  1968  of  FIG. 19 ), any other suitable property or combination thereof. Modified particle collection  1960  may be included in the slurry of flow diagram  1100  of  FIG. 11 . 
       FIG. 20  shows an illustrative side elevation view of electrode component  2002  in contact with substrate  2006  in accordance with some embodiments of the present invention. Shown in  FIG. 21  is an illustrative top plan view of the elements of  FIG. 20 , taken from line XXI-XXI of  FIG. 20  in accordance with some embodiments of the present invention. Electrode component  2002  is shown in contact with substrate  2006  at interface  2010 . Substrate  2006  and electrode component  2002  may have any suitable shape, cross-section shape, curvature (e.g., dome shaped), thickness (of either layer  2006  and  2002 ), relative size (among substrate and composite material), relative thickness (among substrate and composite material), any other property or any suitable combinations thereof. In some embodiments, electrode component  2002  may include the slurry discussed above in process steps  1102  and  1104  of  FIG. 11 . In some embodiments, electrode component  2002  may include the dried slurry discussed above in process step  1106  of  FIG. 11 . Electrode component  2002  may include any other suitable material, or any suitable combination of materials. 
       FIG. 22  shows several illustrative partial cross-sectional views of an electrode component in accordance with some embodiments of the present invention.  FIG. 22(I)  shows a close-up view of illustrative electrode component  2200  which may be a subassembly which may include metallized foam  2204  and substrate  2206 . Metallized foam  2204  may include pore network  2210 , which may impart porosity. In some embodiments, electrode component  2200  may correspond substantially to the electrode component of flow diagrams  1100  of  FIG. 11 ,  1200  of  FIG. 12 ,  1400  of  FIG. 14  or  1500  of  FIG. 15 . In this illustrative example,  FIG. 22(I)  may show the interface region between metallized foam  2204  and substrate  2206  for convenience. 
     FIG.  22 (II) shows a close-up view of illustrative coated electrode component  2220 , which may be a subassembly which may include metallized foam  2204  and substrate  2206 . Coating  2222  may cover some surfaces of electrode component  2200 , forming coated electrode component  2220 . Coating  2222  may include any suitable material such as, for example, Fe, Al, Al 2 O 3 , manganese salts, magnesium salts, Si, any other suitable material or any suitable combination thereof, to aide in forming nanostructures on the active material particles. Coating  2222  may correspond substantially to the coating of flow diagrams  1400  of  FIG. 14  or  1500  of  FIG. 15 . As shown in illustrative FIG.  22 (II), coating  2202  may coat more than one surface, including both exterior (e.g., boundary) and interior (e.g., surfaces along pore network  2210 ) surfaces. 
     FIG.  22 (III) shows a close-up view of illustrative modified electrode component  2240 , which may include coated electrode component  2220 . Nanostructured material  2248  may be deposited on some surfaces of coated electrode component  2220 , forming modified electrode component  2240 . The deposition of nanostructured material  2248  may correspond substantially to the deposition steps discussed in flow diagrams  1300  of  FIG. 13 , flow diagrams  1400  of  FIG. 14  or  1500  of  FIG. 15 . Nanostructured material  2248  may include any suitable type of nanostructured elements including, for example, nanoparticles, nanowires, single-walled or multi-walled nanotubes, closed fullerenes, any other suitable nanostructured elements, any suitable nanostructured composite elements or any suitable combinations or arrays thereof. Although shown as being substantially normal to the surfaces of coated electrode component  2220 , nanostructured material  2248  may include nanostructured elements having any suitable size, shape, orientation distributions. It will also be understood that an illustrative, schematic two dimensional section representation of a three dimensional porous solid, such as that shown by  FIG. 22 , may not show some connectivity of the solid (or pores) but that connectivity may nonetheless exist. 
     It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications may be made by those skilled in the art without departing from the scope and spirit of the invention. It will also be understood that various directional and orientational terms such as “horizontal” and “vertical,” “top” and “bottom” and “side,” “length” and “width” and “height” and “thickness,” “inner” and “outer,” “internal” and “external,” and the like are used herein only for convenience, and that no fixed or absolute directional or orientational limitations are intended by the use of these words. For example, the devices of this invention, as well as their individual components, may have any desired orientation. If reoriented, different directional or orientational terms may need to be used in their description, but that will not alter their fundamental nature as within the scope and spirit of this invention. Those skilled in the art will appreciate that the invention may be practiced by other than the described embodiments, which are presented for purposes of illustration rather than of limitation, and the invention is limited only by the claims that follow.