Abstract:
Various methods, systems, and apparatus for implementing aspects of the use of alloy anodes in three-dimensional lithium-ion batteries are disclosed, while accounting for volume change that occurs in these alloy anodes during charging and discharging. A three-dimensional lithium-ion battery according to certain embodiments comprises a battery enclosure, and an anode protruding from a first surface within the enclosure, with the anode having a first state and an expanded state, where the volume occupied by said anode is larger in the expanded state than in the first state. A first cathode is separated from the anode along a first direction, and a second cathode is separated from the anode along a second direction. A separator contacts the first cathode, the second cathode, and a portion of the anode. A gap is provided between the anode and the separator, the gap being larger in the first state than in the expanded state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. section 119(e) to U.S. Provisional Application No. 60/884,836, entitled “Electrodes For Three Dimensional Lithium Batteries And Methods Of Manufacturing Thereof,” filed on Jan. 12, 2007, and U.S. Provisional Application No. 60/884,828, entitled “Three-Dimensional Batteries and Methods of Manufacturing Using Backbone Structure,” filed on Jan. 12, 2007, both of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Implementations consistent with the principles of the invention generally relate to the field of battery technology, more specifically to electrodes, such as anodes or negative electrodes, for three-dimensional lithium batteries and their methods of manufacture. 
     2. Background 
     Existing energy storage devices, such as batteries, fuel cells, and electrochemical capacitors, typically have planar architectures with an actual surface area of each component being roughly equivalent to a geometrical area, with a porosity being responsible for any area increase over the geometrical area. Energy storage devices such as lithium batteries are the state of the art power sources for many electronic devices due to their high energy density, high power, and long shelf life. 
       FIG. 1  shows a cross sectional view of an existing energy storage device, such as a lithium-ion battery. The battery  15  includes a cathode current collector  10 , on top of which a cathode  11  is assembled. This layer is covered by a separator  12 , over which an assembly of an anode current collector  13  and an anode  14  are placed. This stack is then sometimes covered with another separator layer (not shown) above the anode current collector  13 , and is then rolled and stuffed into a can to assemble the battery  15 . During a charging process, lithium leaves the cathode  11  and travels through the separator  12  as a lithium ion into the anode  14 . Depending on the anode  14  used, the lithium ion either intercalates (e.g., sits in a matrix of an anode material without forming an alloy) or forms an alloy. During a discharge process, the lithium leaves the anode  14 , travels through the separator  12  and passes through to the cathode  11 . 
     Anodes for lithium ion batteries generally fall into two categories: 1) anodes that hold lithium within a material matrix, which are referred to as intercalation anodes; and 2) anodes that form an alloy in the presence of lithium, which are referred to as alloy anodes. Carbon is an example of a material for forming intercalation anodes, while aluminum, silicon, and tin are examples of materials for forming alloy anodes. 
     In the process of formation of a Li—X alloy (where X is a material that can form an alloy with lithium), there can be a significant volume difference between an alloyed and an un-alloyed state. In particular, the alloyed state can occupy a significantly greater volume than the un-alloyed state. In other words, alloy anodes can change volume by a significant fraction during every charge-discharge cycle. This can pose a significant problem for the stability and cycle life of the anodes when incorporated into batteries. In particular, alloy anodes can have capacity loss by way of cracks that are formed during volume change. During repeated cycling, these cracks can propagate and cause parts of an anode material to separate from a matrix. This can cause a decrease in the amount of the anode material that is electrically connected to a current collector, thereby causing capacity loss. In some instances, the volume change in alloy anodes can be as high as 300%. Certain methods have been proposed to overcome the problems of capacity loss due to expansion and contraction of alloy anodes. Unfortunately, these methods suffer from a number of deficiencies, and often involve a traditional planar architecture for a battery. 
     Three-dimensional batteries have been proposed in the literature as ways to improve battery capacity and active material utilization. It has been proposed that a three-dimensional architecture can be used to provide higher surface area and higher energy as compared to a two-dimensional, flat battery architecture. 
       FIG. 2A  illustrates one possible design for a structured silicon anode that is assembled into a lithium-ion battery with a planar cathode in a discharged state, as has been proposed in the literature. For example, reference to Green et al., “Structured Silicon Anodes for Lithium Battery Applications,”  Electrochemical and Solid State Letters,  6, 2003 A75-A79, may help to illustrate the state of the art in structured silicon anodes, and is therefore incorporated by reference as non-essential subject matter herein. Referring to  FIG. 2A , a cathode sheet including a cathode current collector  20  along with a cathode active porous material  21  is assembled on top of a separator material  22 . This dual-layered material is then attached to a structured silicon anode material  23 , which is in the form of pillars that are connected to an anode current collector  24 . During charging, lithium ion transport occurs from the cathode active material  21  through the separator material  22  into the anode material  23 . Since the anode material  23  in this case is made out of silicon, the charging process expands it. As can be seen in  FIG. 2B , top portions of the anode material  23 , which are geometrically closer to the cathode active material  21  than bottom portions of the anode material  23 , experience larger amounts of expansion. This non-uniform expansion can cause a non-uniform current density and, thereby, a non-uniform capacity utilization. This is pictorially shown in  FIG. 2B , where the top portions of the anode material  23  are in an expanded state due to preferential alloying. In certain cases, the top portions can close off before the bottom portions can be lithiated. 
     The following references may also help to illustrate the state of the art, and are therefore incorporated by reference as non-essential subject matter herein: Shin et al., “Porous Silicon Negative Electrodes For Rechargeable Lithium Batteries,”  Journal of Power Sources,  139 (2005) 314-320; Long et. al., “Three-Dimensional Battery Architectures,”  Chemical Reviews , (2004), 104, 4463-4492; Broussely and Archdale, “Li-ion batteries and portable power source prospects for the next 5-10 years,”  Journal of Power Sources,  136, (2004), 386-394; Canadian Patent CA 02388711 by Ikeda et al.; Chang Liu, F OUNDATIONS OF  MEMS, Chapter 10, pages 1-55 (2006); V. Lehmann, “The Physics of Macropore Formation in Low Doped n-Type Silicon,”  J. Electrochem. Soc.  140 (1993), 10, 2836-2843; Vyatkin et al., “Random and Ordered Macropore Formation in p-Type Silicon,”  J. Electrochem. Soc.  149, 1, G70-G76 (2002); van den Meerakker et al., “Etching of Deep Macropores in 6 in. Si Wafers,”  J. Electrochem. Soc.  147, 7, 2757-2761 (2000); Kanamura et. al., “Electrophoretic Fabrication of LiCoO 2  Positive Electrodes for Rechargeable Lithium Batteries,”  Journal of Power Sources,  97-98 (2001) 294-297; Caballero et al., “LiNi 0.5 Mn 1.5 O 4  thick-film electrodes prepared by electrophoretic deposition for use in high voltage lithium-ion batteries,”  Journal of Power Sources,  156 (2006) 583-590; Wang and Cao, “Li + -intercalation Electrochemical/Electrochromic Properties Of Vanadium Pentoxide Films By Sol Electrophoretic Deposition,”  Electrochimica Acta,  51, (2006), 4865-4872; Nishizawa et al., “Template Synthesis of Polypyrrole-Coated Spinel LiMn 2 O 4  Nanotubules and Their Properties as Cathode Active Materials for Lithium Batteries,”  Journal of the Electrochemical Society,  1923-1927, (1997); and Shembel et. al., “Thin Layer Electrolytic Molybdenum Oxysulfides For Lithium Secondary Batteries With Liquid And Polymer Electrolytes,” 5 th    Advanced Batteries and Accumulators, ABA -2004, Lithium Polymer Electrolytes. 
     It would be desirable to make three-dimensional electrochemical energy devices that may provide higher energy and power density, while reducing capacity loss due to expansion and contraction of alloy anodes and the resulting disintegration (also known as attrition) of anode material. 
     SUMMARY 
     Various methods and apparatus relating to electrodes in three-dimensional battery structures are disclosed and claimed. Certain embodiments of the invention relate to electrochemical energy storage systems and devices including anodes that form alloys with lithium. Some embodiments of the invention relate to a battery that can be formed with a wide range of thicknesses, such as from 1 μm to 10,000 μm, and using any of a number of materials that can act as an alloy anode with lithium. This can be achieved by making a structured anode with different methods. In addition, a cathode can also be structured by similar or different methods, and the cathode can extend substantially into a matrix of the anode. In other words, every anode sub-structure can have a corresponding cathode sub-structure that is nearby and is separated by a separator material. This allows for a uniform current distribution and, thereby, uniform expansion of the anode. 
     A three-dimensional lithium-ion battery according to certain embodiments comprises a battery enclosure, and an anode protruding from a first surface within the enclosure, with the anode having a first state and an expanded state, where the volume occupied by said anode is larger in the expanded state than in the first state. A first cathode is separated from the anode along a first direction, and a second cathode is separated from the anode along a second direction. A separator contacts the first cathode, the second cathode, and a portion of the anode. A gap is provided between the anode and the separator, the gap being larger in the first state than in the expanded state. 
     Other aspects and advantages of the present invention can be seen upon review of the figures, the detailed description, and the claims that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are for the purpose of illustrating and expounding the features involved in the present invention for a more complete understanding, and not meant to be considered as a limitation: 
         FIG. 1  is a generic cross-section of an existing two-dimensional energy storage device such as a lithium ion battery. 
         FIG. 2A  is a schematic illustration of a cross-section of a lithium-ion cell in a discharged state that has a structured anode assembled in a planar configuration. 
         FIG. 2B  is a pictorial representation of the configuration of the lithium-ion cell of  FIG. 2A , but in a charged state. 
         FIG. 3A  is a cross-sectional schematic of a lithium-ion battery where an anode is in a discharged (de-lithiated) state, according to an embodiment of the invention. 
         FIG. 3B  is a cross-sectional schematic of the lithium-ion battery depicted in  FIG. 3A  where the anode is in a charged (lithiated) state, according to an embodiment of the invention. 
         FIG. 4  is a schematic representation of some non-limiting examples of various shapes that anodes can be structured in order to provide relief during volumetric expansion, according to an embodiment of the invention. 
         FIGS. 5A-5E  depict a schematic representation of a subtractive process for obtaining a graded anode using a reactive ion etch process, according to an embodiment of the invention. 
         FIGS. 6A-6D  depict a schematic representation of a subtractive process for obtaining a graded anode using an electrochemical etch process, according to an embodiment of the invention. 
         FIGS. 7A-7D  depict a schematic representation of an additive electrodeposition process for obtaining a graded anode, according to an embodiment of the invention. 
         FIGS. 8A-8D  depict a schematic representation of the formation of a semiconductor anode material by photo-electrochemical etch process, according to an embodiment of the invention. 
         FIGS. 9A-9D  depict a representation of a process for assembling a three-dimensional cell where a cathode and an anode are formed separately before being assembled together, according to an embodiment of the invention. 
         FIGS. 10A-10F  show another process for assembling a lithium-ion cell where the cathode has been previously structured using a LIGA process, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Certain embodiments of the invention relate to the design of a lithium-ion battery. The design in certain embodiments utilizes structured alloy anodes that provide room for expansion and contraction during cycling, thereby mitigating the loss of cycle life and providing a uniform current distribution along a graded structure.  FIG. 3A  is a cross-sectional schematic of an improved design for a lithium-ion battery in which an anode is in a discharged (de-lithiated) state. The assembly shown includes a cathode current collector  30  on which a cathode material  31  and a separator material  32  are assembled in a three-dimensional fashion. A structured anode material  34  is assembled in gaps  33  and is connected to an anode current collector  35 .  FIG. 3B  shows the assembly in a charged state, where expansion from charging of the anode material  34  is accommodated in the gaps  33 . 
     The cathode material  31  and the anode material  34  can be assembled in any three-dimensional fashion. This can include, for example, inter-penetrating pillars, plates, honeycomb structures, waves, spirals, and other configurations where anode structures and cathode structures are in proximity to each other in more than one plane. For example, in  FIG. 3A , each anode structure is in close proximity to two cathode structures, one on either side. In structures such as pillars, each electrode could be in proximity to surfaces from more than two counter electrodes. The anode and cathode current collectors  30  and  35  can be separate (top and bottom connection as shown in  FIG. 3A ) or co-planar. 
     Some examples of three-dimensional architectures with co-planar cathodes and anodes are shown in  FIG. 4 .  FIG. 4A  shows a three-dimensional assembly with cathodes and anodes in the shape of pillars,  FIG. 4B  shows a three-dimensional assembly with cathodes and anodes in the shape of plates,  FIG. 4C  shows a three-dimensional assembly with cathodes and anodes in the shape of concentric circles, and  FIG. 4D  shows a three-dimensional assembly with cathodes and anodes in the shape of waves. In these figures, cathodes  40  and anodes  41  are in the same plane and are alternating in a periodic fashion. Also, in these figures, a first cathode is separated from an anode along a first direction, and a second cathode is separated from the anode along a second direction. A separator (not shown in  FIGS. 4A-4D ) contacts the first cathode, the second cathode, and a portion of the anode. A gap is provided between the anode and the separator, the gap being larger in the first state than in the expanded state. 
     Referring back to  FIG. 3A  and  FIG. 3B , since the anode and cathode structures are in proximity to each other in more than one plane, expanding alloy anode structures can undergo more uniform expansion in this architecture. For each anode pillar shown in  FIG. 3A , lithium ions are transported into the anode pillar from multiple sides that have the cathode material  31  nearby. This causes transport of lithium from different directions, thereby causing more uniform expansion than in the case of the design of  FIG. 2 . In order to accommodate the increase in volume, the gaps  33  in the structure shown in  FIGS. 3A and 3B  can be designed judiciously along a height dimension. Referring to  FIG. 3B , connection points from the anode structures to the anode current collector  35  undergo little or no expansion. The illustrated design also improves cycle life of the battery by optimizing ion transport lengths along the three-dimensional structure. Therefore, each ion has a higher probability of cycling back and forth at the same geometrical spot in the structure in order to minimize or reduce transport lengths, and this increases cycle life. 
     Several methods can be used to create and assemble a battery described herein. One way is for two electrodes to be structured separately before being assembled together. One such method of structuring an anode is shown in  FIGS. 5A-5E . The method involves a process of reactively etching anode materials in areas that are to be removed with a halide plasma. This process works for a variety of solid anode materials that can be removed with reactive ion etching. For example, silicon can be patterned in this fashion using a fluoride plasma. As shown in  FIG. 5A , the process involves starting with an anode substrate  50 . A masking layer  51  is deposited on top of the substrate  50  by methods such as vacuum deposition, thermal oxidation, surface coating, and wet chemical deposition. 
     In case of silicon as the substrate  50 , a thermally grown silicon dioxide layer of a particular thickness can serve as the masking layer  51 . This layer  51  is subsequently patterned by standard patterning techniques such as lithography in order to provide a pattern suitable for further processing to create a graded anode structure. In some embodiments of the invention, the masking layer  51  is covered with a second masking layer  52  that is used to pattern the first masking layer  51 . In this case, the first masking layer  51  is patterned by using the second masking layer  52  as a stencil (see  FIGS. 5B-5C ). For the silicon/silicon dioxide case, a standard photoresist can be used as the second masking layer  52 . The second masking layer  52  can be patterned with standard optical lithography techniques. The second masking layer  52  is selectively removed using selective wet or dry methods, leaving behind the patterned first masking layer  51  (see  FIG. 5D ). This combination of the substrate  50  and the patterned first masking layer  51  is then subjected to a directional plasma  53  in a controlled environment in order to transfer the image of the first masking layer  51  onto the substrate  50  (also shown in  FIG. 5D ). This reactive etch process in the presence of a directional plasma source can provide excellent anisotropic etching of the substrate  50  while etching the masking layer  51  itself at a very low rate. After the reactive etch of the substrate  50  is complete, the masking layer  51  can be removed to leave the patterned substrate  50  behind, thereby forming the graded anode structure (see  FIG. 5E ). 
     The following example further explains concepts described with reference to  FIGS. 5A-5E . Single crystal or polycrystalline silicon can be used as the anode substrate  50  that can be etched directionally in the presence of a plasma. The first masking layer  51  can be a thermally grown silicon dioxide layer of a particular thickness. A standard photoresist, such as AZ4620™ and AZP4620™ (commercially available from Clariant Corporation), can be used as the second masking layer  52 . This layer  52  can be spin coated on top of the silicon dioxide layer, and subsequently patterned with standard optical lithography techniques. The areas of the AZ4620™ resist that are exposed to light can be developed away using a developer solution, such as AZ400K™ (commercially available from Clariant Corporation). This patterned structure is then dipped in a solution of HF, NH 3 F, and water (Buffered Oxide Etch), wherein exposed silicon dioxide surfaces are dissolved. The remaining photoresist can be selectively removed by using a compatible organic solvent, such as N-methyl-2-Pyrrolidone, leaving behind the patterned silicon dioxide layer. This combination of the silicon and patterned silicon dioxide can then be subjected to a directional fluoride plasma source in order to etch an image of the silicon dioxide layer onto the substrate  50 . The directionality of the plasma  53  is controlled by a bias voltage between an anode and a cathode in a conventional plasma reactive ion etcher. A difference in rate between etch of silicon and silicon dioxide causes a pattern to be transferred to the substrate  50  without much etching in a lateral direction. After the reactive etch of silicon is complete, the masking layer  51  can be removed by immersion in the Buffered Oxide Etch solution to leave the patterned substrate  50  behind. 
       FIGS. 6A-6D  depict a schematic representation of a process for manufacturing an alloying anode using a subtractive electrochemical etch process. This process can be used for materials that can be etched in the presence of an electrical driving force. Materials that form alloy anodes such as aluminum, silicon, and tin can be patterned in this fashion. In this particular embodiment, an anode substrate  60  is patterned using an electrically insulating masking layer  61  that is deposited on top of the substrate  60  by methods such as vacuum deposition, thermal oxidation, surface coating, and wet chemical deposition. This layer  61  is subsequently patterned by standard patterning techniques such as lithography in order to provide a pattern suitable for further processing to create the anode. In some embodiments of the invention, the masking layer  61  is covered with a second masking layer  62  that is used to pattern the first masking layer  61  (see  FIG. 6A ). In this case, the first masking layer  61  is patterned by using the second masking layer  62  as a stencil. The second masking layer  62  is selectively removed using selective wet or dry methods, leaving behind the patterned first masking layer  61  (see  FIG. 6B ). The combination of the substrate  60  and the first masking layer  61  is placed in an electrochemical cell  63  that has a counter electrode  64  and a nozzle  65  that delivers a solution used to electrochemically remove a material in areas that are exposed to the solution (see  FIG. 6C ). In certain embodiments, the whole workpiece can be dipped into the solution that can dissolve the material that is in contact with the solution. However, the illustrated process can be more isotropic in nature, and typically an amount of material removed in the depth direction D can be substantially the same as the amount of material removed in each side of the width direction W. A dip-tank solution can be used for making features in which gaps G between neighboring anode structures are significantly narrower than the width W. A DC power source  66  is used to apply a potential that is sufficient to remove the material in contact with the solution. The process is complete when the desired amount of material is removed, which can be controlled based on the rate of etching that has been previously determined. In certain other cases, a current can be monitored, and a drop in the current can correspond to an end-point of the electrochemical reaction. After the reaction is substantially complete, the workpiece is removed, and the masking layer  61  can be removed to leave the patterned substrate  60  behind, thereby forming the anode (see  FIG. 6D ). 
     The following example further explains concepts described with reference to  FIGS. 6A-6D . One example of the substrate  60  for electrochemical patterning is an aluminum sheet. A sheet of a desired thickness corresponding to an anode height can be used as the substrate  60 , and is patterned using the electrically insulating masking layer  61  (e.g., commercially available photoresist AZ4620™ or AZP4620™) that is deposited on top of the substrate  60  by spin coating. This layer  61  can be exposed to light in the presence of a photomask that blocks light to areas in which the resist should be left behind. The workpiece is put into a solution that selectively removes the exposed areas. The combination of the substrate  60  and the first masking layer  61  is placed in the electrochemical cell  63  that has the counter electrode  64  (platinum) and the nozzle  65  that delivers the electrochemical etch solution used to electrochemically remove the metal in areas that are exposed to the solution. A solution containing 5 wt % potassium hydroxide can be delivered through the nozzle  65  to the workpiece. The DC power source  66  can be used to apply an anodic potential to the substrate  60 , which removes aluminum in areas where the solution comes in contact with the aluminum anode and the platinum cathode at the same time, thereby forming a local electrochemical cell. After the reaction is substantially complete, the workpiece is removed, and the masking layer  61  is removed with N-methyl-2-pyrrolidone to leave the patterned substrate  60  behind. 
     In certain other embodiments of the invention, additive processes can be used to process electrodes of an energy storage device.  FIGS. 7A-7D  show a schematic representation of a process for manufacturing an anode using an additive electrochemical deposition process. This process can be referred to as a LIGA process, which stands for “lithography, galvano-forming and molding (Abformung).” In this process, a conductive or non-conductive substrate  70  is used. In case of a non-conducting substrate, a conducting layer  71  is deposited. Photoresist  72  is coated on top of this substrate  70 , and is patterned by standard lithography techniques using a photomask  73  to leave behind the photoresist  72  in areas where an electrode material is not to be deposited (see  FIGS. 7A and 7B ). The workpiece is placed in an electroplating bath with a potential enough to reduce metallic ions present in solution to form a metal  74  (see  FIG. 7C ). The metallic ions are reduced at a conductive surface and are not deposited where the photoresist  72  is present. When the process is substantially complete, the workpiece including components  70 ,  72 , and  74  is removed from a plating cell, and the photoresist  72  is removed to leave the electrode structure (including components  70  and  74 ) behind (see  FIG. 7D ). 
     The following example further explains concepts described with reference to  FIGS. 7A-7D  to produce a tin anode structure. In this process, a silicon wafer can be used as the semi-conductive substrate  70 . Copper can be deposited using sputter deposition to create the conductive layer  71  on top of the silicon. A positive or negative tone photoresist  72  (e.g., AZ4620™ or AZP4620™) can be coated on top of this substrate  70  and is patterned by standard lithography techniques to leave behind the photoresist  72  in areas where an anode material is not to be deposited. This workpiece can be placed in a methane sulfonic acid-based tin electroplating bath along with a platinum counter electrode and a potential enough to reduce stannous ions present in the solution to tin metal  74 . The metal ions are reduced at a conductive surface and are not deposited where the photoresist  72  is present. When the process is substantially complete, the workpiece including the silicon wafer  70 , photoresist  72 , and tin metal  74  can be removed. Subsequently, the photo resist  72  can be removed using N-methyl-2-pyrrolidone to leave a backbone structure of the silicon wafer  70 , the copper seedlayer  71 , and the tin metal  74  behind. The remaining copper metal in the area where the photoresist  72  was present can then be removed by a chemical etch involving 2% sulfuric acid and 1% hydrogen peroxide. 
     In the case where a material to be templated is semi-conductive, a process called photoelectrochemical etch can be used for patterning the material. For example, silicon is a material that can be patterned and used directly as an anode material.  FIGS. 8A-8D  shows a pictorial representation of a semiconductor patterning process for anodes in a lithium-ion battery. In the case of silicon, a silicon substrate  80  to be patterned can be a single crystal or polycrystalline and can be n-type or p-type. A first masking layer  81  can be deposited on top of the substrate  80 . In case of silicon, the masking layer  81  can either be SiO 2  or Si 3 N 4 . This masking layer  81  can then be patterned using a standard lithographic process using a photoresist  82  as a template for etching the first masking layer  81  (see  FIGS. 8A and 8B ). After the image is transferred to the masking layer  81  (see  FIG. 8C ), the remaining photoresist can be removed before patterning the substrate  80 . This combination of substrate  80  and masking layer  81  can then be immersed in an etch solution containing dilute HF (0.1-10 wt %) and ethanol (5-25 wt %), and an anodic potential can be applied in the presence of backside illumination  83  (see  FIG. 8D ). This backside illumination  83  can cause an excess of holes at a pit end of the substrate  80 , thereby causing preferential anisotropic etching (see  FIG. 8D ). The resulting structured anode can then be used for assembly in a three-dimensional battery with a cathode and a separator having been separately formed using a process that produces a structured shape. Some examples of assembling the battery are explained below. 
       FIGS. 9A-9D  depict a schematic representation of the assembly of a complete cell with a structured anode, a separator, and a cathode. Common cathode materials for lithium ion batteries include mixed metal oxide materials, such as LiCoO 2 , or other oxides of Nickel, Cobalt, and Manganese. These oxides are typically in a powder form and are compacted into flat shapes along with conducting carbon particles and binders. The schematic example shown in  FIGS. 9A-9D  depict a methodology to compact a cathode material into a three-dimensional structured shape before assembling the anode. The process involves generating a mandrel  90  with the inverse shape of a cathode material shape (see  FIG. 9A ). This mandrel  90  can be made using conventional methodologies such as casting, extrusion, and so forth. The mandrel  90  can be made from metals, ceramics, plastics, and combinations thereof. A polymer material that acts as a separator  91  for the lithium-ion battery can be laid on top of the mandrel  90  and made into a conformal shape over the mandrel  90  with the assistance of a vacuum to remove air in channels. Due to vacuum application, the separator  91  can be conformally shaped on top of the mandrel  90  (see  FIGS. 9A-9B ). Once this is substantially complete, a cathode material slurry  92 , which is typically in the form of cathode material oxides, conducting carbon, and binders, can be applied and vacuum-filled into trenches left behind by the mandrel  90  (see  FIG. 9C ). Since the separator  91  is a porous film, application of vacuum can force the cathode material slurry  92  to compact into the trenches in the mandrel  90 . Once the cathode material slurry  92  and the separator  91  are substantially compacted, the mandrel  90  can be removed by either a mechanical or thermal release. In certain other embodiments, a cathode current collector can also be deposited or placed on top of the resulting cathode. The resulting cathode and separator  91  can be assembled along with an anode material  93  and an anode current collector  94  that has been formed separately using some of the concepts discussed herein (see  FIG. 9D ). 
     Due to expansion and contraction of an anode material that forms an alloy with lithium, it may be desirable to form gaps between a separator and the anode material. If the anode material is physically connected to the separator, repeated cycling of the anode material can mechanically deform the separator. In order to avoid this deformation, the separator can be conformally coated or assembled over a cathode material, rather than the anode material. The method explained earlier by way of  FIGS. 8A-8D  is one such methodology to conformally coat the separator over the cathode material while leaving gaps to allow anode expansion. 
       FIGS. 10A-10F  show another example of a lithographically defined cathode material along with a deposited separator that is subsequently assembled into an anode structure that has been structured separately. The process involves taking a substrate  100  and depositing a conductive layer  101  on top by vacuum deposition or electroless deposition. Photoresist  102  is coated on top of this substrate  100  and is patterned by standard lithography techniques using a photo mask  103  to leave behind the photoresist  102  where an electrode material is not to be deposited (see  FIGS. 10A-10B ). This assembly is placed in an electroplating bath with a potential sufficient to reduce metallic ions present in solution to metal  104 . The metal ions are reduced at a conductive surface and are not deposited where the photoresist  102  is present (see  FIG. 10C ). When the process is substantially complete, the workpiece including components  100 ,  102 , and  104  is removed from a plating cell, and the photoresist  102  is removed to leave a cathode structure including components  100  and  104  behind (see  FIG. 10D ). 
     A separator film  105  can be deposited on the cathode structure using techniques for deposition of porous materials, such as spin or spray coating, physical or chemical vapor deposition, and electrophoretic deposition (see  FIG. 10E ). The thickness of the separator film  105  can be tailored according to specific process and specific parameters that are being used for deposition. A cathode  106  is then assembled on top of this structure to yield a battery (see  FIG. 10F ). 
     A variety of cathode materials that can be electrodeposited can be used for the techniques described earlier. These techniques can also be used to deposit materials electrophoretically or using techniques such as co-deposition, sol-gel deposition, and so forth. For example, in the case of a lithium-ion battery, a LiCoO 2 , LiNi 0.5 Mn 1.5 O 4 , or V 2 O 5  cathode material can be electrophoretically deposited onto a conductive substrate. Cathode materials can also be co-deposited along with a polypyrrole matrix. In addition, certain cathode materials for lithium-ion batteries can be electrochemically deposited, such as molybdenum oxysulfides. 
     In some embodiments, a backbone structure is made out of a metal, semiconductor, organic, ceramic, or glass using a subtractive formation technique. These materials can be processed by reactively etching a substrate using a selective etch mask and a plasma etch process. Alternatively, or in conjunction, electrochemical etching, stamping, or electrical discharge machining can be used to selectively remove material preferentially in areas where these materials are not desired. 
     In certain embodiments, a backbone structure is made out of a metal, semiconductor, organic, ceramic, or glass using an additive formation technique. These materials can be processed by making a sacrificial mold using a technique such as conventional lithography, and depositing a backbone material using techniques such as electrochemical deposition, electroless deposition, electrophoretic deposition, vacuum assisted filling, stencil assisted filling, and so forth. In certain cases, the backbone structure can be assembled directly using a wirebonding process. In other cases, the backbone structure can be made on a flat plate using conventional lithography and deposition techniques, and subsequently assembled by “pick and place” and soldering or gluing techniques. 
     In certain embodiments, a backbone material can be shaped using printing techniques, such as three-dimensional printing and inkjet printing, to form a backbone structure using single or multiple layers of printing to obtain a desired shape and thickness. Alternatively, or in conjunction, the backbone material can be assembled in the form of layered sheets, with sacrificial layers deposited in between. After stacking of the sheets is substantially complete, a resulting structure may be cut into pieces of a desired height, assembled together, and the sacrificial material may be released to provide the backbone structure. 
     In the case of an electrically conductive backbone structure, an active material may be directly assembled on top of and around the backbone structure by various techniques, such as electrochemical deposition, electroless deposition, co-deposition in an organic or inorganic matrix, electrophoretic deposition, mechanical filling and compacting, and vacuum assisted flow deposition. 
     In case of an electrically non-conductive backbone structure, a conducting layer can be deposited by various techniques, such as electrochemical or electroless deposition, vapor assisted vacuum deposition such as Atomic Layer Deposition (ALD) and Chemical Vapor Deposition (CVD), sputter deposition, evaporation, and electrophoretic deposition. This conductive layer can be subsequently removed in order to remove an electrical connection between an anode and a cathode. This removal can be accomplished using techniques such as sputter etching, ion milling, and liftoff. In addition, techniques such as chemical dissolution can be used with standard techniques such as lithography to protect areas that do not need to be removed. 
     Some of the concepts outlined herein can be used to make two-dimensional as well as three-dimensional energy storage and retrieval systems and devices. 
     While the invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention as defined by the appended claims. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, method, operation or operations, to the objective, spirit, and scope of the invention. All such modifications are intended to be within the scope of the claims appended hereto. In particular, while the methods disclosed herein have been described with reference to particular operations performed in a particular order, it will be understood that these operations may be combined, sub-divided, or re-ordered to form an equivalent method without departing from the teachings of the invention. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the invention.