Enhanced cycle lifetime with gel electrolyte for mno2 nanowire capacitors

Abstract

A nanowire energy storage device such as a nanowire battery or a capacitor having a cathode comprising a plurality of nanowires and an anode comprising a plurality of nanowires interlaced with the plurality of nanowires of the cathode, and embedded in a PMMA gel electrolyte.

What is claimed: 
     
         1 . A nanowire energy storage device comprising:
 a cathode,   an anode, wherein one or more of the cathode and the anode comprises a plurality of nanowires,   a poly(methylmethacrylate) (PMMA) electrolyte gel, wherein the cathode and the anode are embedded in the PMMA electrolyte gel.   
     
     
         2 . The storage device of  claim 1 , wherein the storage device is one of a battery and a capacitor. 
     
     
         3 . The storage device of  claim 1 , wherein the anode and cathode are coupled to metal contacts. 
     
     
         4 . The storage device of  claim 3 , wherein the metal contacts are gold contacts. 
     
     
         5 . The storage device of  claim 1 , wherein the plurality of nanowires has a reversible cycle stability of more than 100,000 cycles. 
     
     
         6 . The storage device of  claim 1 , wherein the plurality of nanowires has a reversible cycle stability of more than 200,000 cycles. 
     
     
         7 . The storage device of  claim 1 , wherein the plurality of nanowires are symmetrical δ-MnO 2  nanowires. 
     
     
         8 . A nanowire energy storage device, comprising:
 a first nanowire energy storage device according to  claim 1 , and   a second nanowire energy storage device according to  claim 1 ,   wherein a total poly(methylmethacrylate) (PMMA) gel layer thickness of the nanowire energy storage device is 2 μm.   
     
     
         9 . The storage device of  claim 8 , wherein the first nanowire energy storage device and the second nanowire storage device are pressed together such that electrical contacts are on opposite ends of the storage device with sufficient offset of a glass layer of the first nanowire storage device and a glass layer of the second nanowire storage device. 
     
     
         10 . The storage device of  claim 8 , wherein the device is hermetically sealed using hot glue. 
     
     
         11 . The storage device of  claim 8 , wherein an operating voltage of the storage device is 1.8V. 
     
     
         12 . The storage device of  claim 8 , wherein the storage device has a reversible cycle stability of more than 100,000 cycles. 
     
     
         13 . A method of manufacturing a nanowire energy storage device, comprising:
 thermally evaporating a nickel firm onto a glass substrate;   spin-coating a positive photoresist layer onto the nickel film;   photo-patterning the photoresist layer and developing the pattern in developer solution;   etching exposed nickel and undercutting an edge of the photoresist layer to produce a horizontal trench;   electrodepositing gold nanowires into the horizontal trench by immersing the patterned photoresist layer into a gold plating solution;   evaporating gold contacts onto ends of the gold nanowires;   electrodepositing δ-MnO 2  onto the gold nanowires; and   spin-coating poly(methylmethacrylate) (PMMA) gel electrolyte onto the device.   
     
     
         14 . The storage device of  claim 13 , wherein the PMMA gel is heated to 115° C. on a hot plate for 10 minutes before spincoating in order to reduce its viscosity. 
     
     
         15 . A method of manufacturing a two-layer (“sandwich”) capacitor, comprising:
 pressing a first storage device according to  claim 13  together with a second storage device of  claim 13 , wherein electrical contacts are on opposite ends of the capacitor; and 
 hermetically sealing edges of the capacitor with hot glue. 
 
     
     
         16 . The method of  claim 15 , wherein a total poly(methylmethacrylate) (PMMA) gel layer thickness of the capacitor is 2 μm. 
     
     
         17 . The method of  claim 13 , wherein the glass substrate is 2.5 cm×2.5 cm.