Method for reducing current leakage and enhancing UV stability in electrochemichromic solutions and devices

A method for reducing leakage current and enhancing UV stability in an electrochemichromic cell having spaced plates, each having an inwardly facing conductive surface, and a solution located in said cell between said plates, said solution comprising a redox chemical pair which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage, said redox pair comprising a cathodic material selected from the group consisting of one of methyl, ethyl, benzyl and heptylviologen or mixtures thereof, with a counterion selected from the group consisting of one of perchlorate, tetrafluoroborate, trifluoromethanesulfonate, hexafluorophosphate, hexafluoroarsenate and mixtures thereof and an anodic material selected from the group consisting of:

• DMPA--5,10-dihydro-5,10-dimethylphenazine,
• DEPA--5,10-dihydro-5,10-diethylphenazine,
• DOPA--5,10-dihydro-5,10-dioctylphenazine,
• TMPD--N,N,N',N'-tetramethylphenylenediamine,
• TMBZ--N,N,N',N'-tetramethylbenzidine,
• TTF--Tetrathiafulvalene and mixtures thereof,
• said method comprising:
• using a solvent for said redox chemical pair comprising at least 25% by volume glutaronitrile.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage;
• said solvent including at least 25% by volume of glutaronitrile.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• and
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage;
• said solvent including glutaronitrile and 3-methylsulfolane in a ratio by volume of from about 75:25 to about 25:75.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• and
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage;
• said solvent including glutaronitrile and 3,3'-oxydipropionitrile in a ratio by volume of from about 75:25 to about 25:75.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• and
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage;
• said solvent including glutaronitrile and 3,3'-oxydipropionitrile in a ratio by volume of from about 75:25 to about 25:75.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• and
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage;
• said solvent including 3-hydroxypropionitrile and glutaronitrile in a ratio by volume of from about 75:25 to about 25:75.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• and
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage, said redox pair comprising a cathodic material selected from the group consisting of one of methyl, ethyl, benzyl and heptylviologen or mixtures thereof, with a counterion selected from the group consisting of one of perchlorate, tetrafluoroborate, trifluoromethanesulfonate, hexafluorophosphate, hexafluoroarsenate and mixtures thereof and an anodic material selected from the group consisting of:
• DMPA--5,10-dihydro-5,10-dimethylphenazine,
• DEPA--5,10-dihydro-5,10-diethylphenazine,
• DOPA--5,10-dihydro-5,10-dioctylphenazine,
• TMPD--N,N,N',N'-tetramethylphenylenediamine,
• TMBZ--N,N,N',N'-tetramethylbenzidine,
• TTF--Tetrathiafulvalene and mixtures thereof,
• said solvent including at least 25% by volume of glutaronitrile.

An electrochemichromic cell comprising:

• spaced plates, each having an inwardly facing conductive surface;
• an electrochemichromic solution in said cell, between said spaced plates, said solution comprising:
• solvent;
• and
• a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage, said redox pair including a cathodic material and an anodic material, said cathodic material consisting of one of methyl and ethylviologen and mixtures thereof, using one of hexafluorophosphate, hexafluoroarsenate and mixtures thereof as counterion, and said anodic material is 5,10-dihydro-5,10-dimethylphenazine,
• said solvent including at least 25% by volume of glutaronitrile.

A method for filling an electrochemichromic cell having relatively closely spaced plates, each having an inwardly facing conductive surface, said spaced plates being sealed around the periphery by a seal, said filling method comprising:

• introducing a small gap int said seal of an empty cell;
• placing said cell in a chamber along with a container of an electrochemichromic solution and evacuating said chamber;
• lowering said cell into said container of electrochemichromic solution such that said gap is located under the surface of the electrochemichromic solution which solution comprises a solvent, a redox chemical pair in solution in said solvent which colors in the presence of an applied voltage and which bleaches to a colorless condition in the absence of an applied voltage, said solvent including at least 25% by volume of glutaronitrile;
• said peripheral seal enclosing an area of each of said plates;
• said solvent having a vapor pressure such that said vapor pressure, expressed in units of millimeters of mercury, multiplied by said area, expressed in units of square centimeters, is less than 5.969;
• exposing said electrochemichromic solution to a source of inert gas of pressure greater than that in said cell to thereby cause said solution to flow into said cell;
• sealing said gap in said peripheral seal of said cell.