Solvent independent reference electrodes for use with non-aqueous electrolytes

Abstract

The present disclosure relates to a reference electrode apparatus for use in electrochemical testing applications. The apparatus may have a hollow tube and a frit disposed adjacent one end of the hollow tube. A layer of material may secure the frit to the one end of the hollow tube to close off the one end. A silver wire is included which has a coating that helps to prevent a voltage potential change in an output of the apparatus during a test in which the silver wire is in contact with an ionic liquid. The silver wire with the coating is disposed at least partially in the hollow tube. An ionic liquid is disposed in the hollow tube in which at least a portion of the sulfide coated wire is disposed.

What is claimed is: 
     
         1 . A reference electrode apparatus for use in electrochemical testing applications, the apparatus comprising:
 a hollow tube;   a frit disposed adjacent one end of the hollow tube;   a layer of material securing the frit to the one end of the hollow tube to close off the one end;   a silver wire coated with a coating that helps to prevent a voltage potential change in an output of the apparatus during a test in which the silver wire is in contact with an ionic liquid, the silver wire with the coating thereon being disposed in the hollow tube; and   an ionic liquid disposed in the hollow tube in which at least a portion of the silver wire is disposed.   
     
     
         2 . The apparatus of  claim 1 , wherein the coating comprises a silver sulfide coating. 
     
     
         3 . The apparatus of  claim 1 , wherein the hollow tube comprises a hollow glass tube. 
     
     
         4 . The apparatus of  claim 1 , wherein the frit comprises a porous glass frit. 
     
     
         5 . The apparatus of  claim 1 , wherein the layer of material securing the frit to the one end of the hollow tube comprise a layer of shrink wrap material. 
     
     
         6 . A reference electrode apparatus for use in electrochemical testing applications, the apparatus comprising:
 a hollow tube;   a frit disposed adjacent one end of the hollow tube;   a layer of material securing the frit to the one end of the hollow tube to close off the one end;   a silver sulfide coated silver wire disposed within the hollow tube; and   an ionic liquid solution disposed in the hollow tube in which at least a portion of the silver sulfide coated silver wire is disposed.   
     
     
         7 . The apparatus of  claim 6 , wherein the hollow tube comprises a hollow glass tube. 
     
     
         8 . The apparatus of  claim 7 , wherein the hollow glass tube comprises a diameter of no more than about 4 mm. 
     
     
         9 . The apparatus of  claim 7 , wherein the frit comprises a glass frit. 
     
     
         10 . The apparatus of  claim 7 , wherein the layer of material comprises a shrink wrap. 
     
     
         11 . A method for forming a reference electrode for use in electrochemical testing applications, the method comprising:
 positioning a glass frit against one end of a hollow glass tube;   arranging a portion of shrink wrap over portions of the glass frit and the glass tube;   heating the portion of shrink wrap, the glass tube and the glass frit to shrink the shrink wrap onto the portions of the glass frit and the glass tube to form an assembly;   boiling the assembly in a solution to remove organic contaminants;   boiling the assembly in water;   drying the assembly;   forming a silver sulfide coated silver wire;   filling the glass tube with an ionic liquid; and   inserting at least a portion of the silver sulfide coated silver wire into the ionic liquid in the glass tube.   
     
     
         12 . The method of  claim 11 , wherein boiling the assembly in a solution comprises boiling the assembly in hydrogen peroxide. 
     
     
         13 . The method of  claim 11 , wherein drying the assembly comprises drying the assembly in an oven at a temperature of about 140° C. 
     
     
         14 . The method of  claim 11 , wherein heating the portion of shrink wrap comprises heating the portion of shrink wrap to a temperature of about 350° C. for two hours. 
     
     
         15 . The method of  claim 11 , wherein forming a silver sulfide coated silver wire comprises:
 placing a quantity of sulfur on a hot plate;   arranging a silver wire over the sulfur; and   using the hot plate to heat the sulfur to cause sublimation of the sulfur and   subsequent reaction with the silver wire, to thus form the silver sulfide coated silver wire.   
     
     
         16 . A reference electrode apparatus for use in electrochemical testing applications, the apparatus comprising:
 a silver wire; and   a silver sulfide coating formed on the wire to produce a silver sulfide coated silver wire;   the silver sulfide coating helping to prevent a voltage potential change in an output of the apparatus during a test in which the silver sulfide coated silver wire is in contact with an ionic liquid for some period of time during a testing application.   
     
     
         17 . The apparatus of  claim 16 , further comprising a glass tube in which the silver sulfide coated silver wire is positioned during the testing application, the glass tube further containing the ionic liquid. 
     
     
         18 . The apparatus of  claim 17 , further comprising a glass frit secured to an end of the glass tube. 
     
     
         19 . The apparatus of  claim 18 , further comprising a shrink wrap which secures the glass frit to the glass tube.