Nanomachined structures for porous electrochemical capacitors

Abstract

Embodiments of the invention describe energy storage devices, porous electrodes, and methods of formation. In an embodiment, an energy storage device includes a porous structure containing multiple main channels that extend into an electrically conductive structure at an acute angle. In an embodiment, an energy storage device includes a porous structure containing an array of V-groove or pyramid recesses.

What is claimed is: 
     
         1 . An energy storage device comprising:
 a porous structure within an electrically conductive structure, the porous structure containing an array of V-groove or pyramid recesses in a main surface of the porous structure; and   a plurality of main channels extending into the electrically conductive structure for each V-groove or pyramid recess, wherein each main channel has an opening in the corresponding V-groove or pyramid recess.   
     
     
         2 . The energy storage device of  claim 1 , further comprising a second porous structure within a second electrically conductive structure, and a separator between the porous structure and the second porous structure, wherein the separator extends into the array of V-groove or pyramid recesses. 
     
     
         3 . The energy storage device of  claim 2 , wherein the second porous structure extends into the array of V-groove or pyramid recesses. 
     
     
         4 . The energy storage device of  claim 2 , wherein the second electrically conductive structure is a material selected from the group consisting of: carbon, a carbon-based material, and a pseudocapacitive material. 
     
     
         5 . The energy storage device of  claim 2 , wherein the second porous structure contains a second array of V-groove or pyramid recesses in a second main surface of the second porous structure; and
 a second array of main channels extending into the second electrically conductive structure, wherein each main channel has an opening in the corresponding V-groove or pyramid recess, wherein the second porous structure extends into the V-groove or pyramid recesses of the porous structure.   
     
     
         6 . The energy storage device of  claim 2 , wherein separator completely fills the array of V-groove or pyramid recesses. 
     
     
         7 . The energy storage device of  claim 1 , wherein the energy storage device is incorporated within an electronic device, the energy storage device being associated with a microprocessor. 
     
     
         8 . The energy storage device of  claim 1 , wherein each of the main channels extends into the electrically conductive structure with sidewalls including a primary surface shape and a secondary surface shape superimposed on the primary surface shape. 
     
     
         9 . The energy storage device of  claim 8 , wherein the primary surface shape is a linear taper. 
     
     
         10 . The energy storage device of  claim 9 , wherein the secondary surface shape is sinusoidal 
     
     
         11 . The energy storage device of  claim 8 , wherein each of the main channels includes alternating reservoir regions and connecting regions. 
     
     
         12 . The energy storage device of  claim 2 , wherein the second porous electrode comprises lithium-doped carbon. 
     
     
         13 . The energy storage device of  claim 2 , wherein the second porous electrode comprises a nanodiamond film. 
     
     
         14 . A method of forming a porous electrode comprising:
 immersing an electrically conductive substrate in an electrochemical etching bath; and   applying an etching current across the electrically conductive substrate;   wherein applying the etching current comprises:
 varying the etching current in a non-linear fashion to create a porous structure containing multiple main channels in the electrically conductive substrate, wherein each one of the main channels has an opening to a main surface of the porous structure; or 
 superimposing a secondary etching current variation on a primary etching current variation. 
   
     
     
         15 . The method of  claim 14 , wherein varying the etching current in a non-linear fashion comprises varying the etching current in alternating nodes of relatively higher and lower current. 
     
     
         16 . The method of  claim 15 , wherein varying the etching current in a non-linear fashion comprises continuously lowering the etching current. 
     
     
         17 . The method of  claim 14 , wherein the primary etching current variation is a non-linear current variation and the secondary etching current variation is a linear addition of a sinusoidal function. 
     
     
         18 . The method of  claim 17 , wherein the non-linear current variation is approximated by a second or third order polynomial. 
     
     
         19 . The method of  claim 14 , wherein the electrochemical etching bath includes a concentration of HF:alcohol of 2:1 or greater concentration of HF. 
     
     
         20 . The method of  claim 14 , further comprising maintaining the electrochemical etching bath at approximately room temperature or less while applying the etching current. 
     
     
         21 . A method of forming an energy storage device comprising:
 electrochemically etching an electrically conductive substrate to release a porous structure from the electrically conductive substrate; and   joining the porous structure with a separator layer and a second porous structure.   
     
     
         22 . The method of  claim 21 , wherein joining comprises depositing the separator layer on the porous structure. 
     
     
         23 . The method of  claim 22 , wherein joining comprises stacking the porous structure on the separator layer or stacking the separator layer on the porous structure. 
     
     
         24 . The method of  claim 21 , further comprising electrochemically etching a second electrically conductive substrate to release the second porous structure from the second electrically conductive substrate.