Electrolytes for use in a capacitor

Abstract

An electrolyte for activating an electrolytic or electrochemical capacitor is described. The electrolyte preferably includes a mixed solvent of water and ethylene glycol having an ammonium salt dissolved therein. An acid such as phosphoric or acetic acid is used to provide a pH of about 3 to 6. The electrolyte is particularly useful for activating a ruthenium oxide/tantalum capacitor having an anode breakdown voltage in the range of 175 to 300 volts.

What is claimed is: 
     
       1. An electrolyte for an electrochemical energy storage device, the electrolyte consisting essentially of:
 a) a mixed solvent of water and at least one second solvent selected from the group consisting of ethylene glycol, polyethylene glycol, formamide, dimethyl formamide, γ-butyrolactone, and mixtures thereof, wherein the water is present, by weight, up to about 85% and the second solvent is present, by weight, up to about 95%;   b) an ammonium salt dissolved in the mixed solvent; and   c) an acid.   
     
     
       2. The electrolyte of  claim 1  wherein the ammonium salt is selected from the group consisting of ammonium acetate, ammonium formate, ammonium hydrogen maleate, ammonium hydrogen phosphate, and mixtures thereof. 
     
     
       3. The electrolyte of  claim 1  wherein the acid is selected from the group consisting of citric acid, oxalic acid, formic acid, maleic acid, phosphoric acid, malonic acid, maltic acid, sulfuric acid, adipic acid, succinic acid, nitric acid, acetic acid, and mixtures thereof. 
     
     
       4. The electrolyte of  claim 1  having a pH between about 1 to about 7. 
     
     
       5. An electrolyte for a capacitor, the electrolyte comprising:
 a) a mixed solvent of water and ethylene glycol, wherein the water is present, by weight, up to about 85% and the ethylene glycol is present, by weight, up to about 95%;   b) a solute of ammonium acetate; and   c) a mixed acid of acetic acid and phosphoric acid.   
     
     
       6. The electrolyte of  claim 5  wherein the ammonium acetate is present, by weight, up to about 50%. 
     
     
       7. The electrolyte of  claim 5  wherein the acetic acid is present, by weight, up to about 80% and the phosphoric acid is present, by weight, up to about 6%. 
     
     
       8. The electrolyte of  claim 5  wherein the capacitor comprises a ruthenium oxide cathode and a tantalum anode. 
     
     
       9. The electrolyte of  claim 8  wherein the ruthenium oxide is provide on a titanium substrate. 
     
     
       10. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising:
 i) a mixed solvent of water and ethylene glycol, wherein the water is present, by weight, up to about 85% and the ethylene glycol is present, by weight, up to about 95%; 
 ii) an ammonium salt dissolved in the solvent; and 
 iii) an acid. 
   
     
     
       11. The capacitor of  claim 10  including providing the electrolyte having ammonium acetate up to about 50%, by weight. 
     
     
       12. The capacitor of  claim 10  including providing the electrolyte having acetic acid up to about 80%, by weight, and phosphoric acid up to about 6%, by weight. 
     
     
       13. The capacitor of  claim 10  comprising a ruthenium oxide cathode and a tantalum anode. 
     
     
       14. The capacitor of  claim 10  wherein the ruthenium oxide is provide on a titanium substrate. 
     
     
       15. The capacitor of  claim 10  wherein the electrolyte includes, by weight, about 49.41% de-ionized water, about 19.45% ethylene glycol, about 15.55% ammonium acetate, about 0.31% phosphoric acid and about 15.28% acetic acid. 
     
     
       16. The capacitor of  claim 15  rated to about 175 volts. 
     
     
       17. The capacitor of  claim 10  wherein the electrolyte includes, by weight, about 44.46% de-ionized water, about 34.61% ethylene glycol, about 10.04% ammonium acetate, about 0,51% phosphoric acid and about 10.39% acetic acid. 
     
     
       18. The capacitor of  claim 17  rated to about 200 volts. 
     
     
       19. The capacitor of  claim 10  wherein the electrolyte includes, by weight, about 46.52% de-ionized water, about 36.05% ethylene glycol, about 8.29% ammonium acetate, about 0.44% phosphoric acid and about 8.70% acetic acid. 
     
     
       20. The capacitor of  claim 19  rated to about 250 volts. 
     
     
       21. The capacitor of  claim 10  wherein the electrolyte includes, by weight, about 46.59% de-ionized water, about 41.45% ethylene glycol, about 5.60% ammonium acetate, about 0.48% phosphoric acid and about 5.88% acetic acid. 
     
     
       22. The capacitor of  claim 21  rated to about 250 volts. 
     
     
       23. The capacitor of  claim 10  wherein the electrolyte includes, by weight, about 51.94% de-ionized water, about 40.29% ethylene glycol, about 3.54% ammonium acetate, about 0.59% phosphoric acid and about 3.64% acetic acid. 
     
     
       24. The capacitor of  claim 23  rated to about 300 volts. 
     
     
       25. A method for providing an electrolyte, consisting essentially of the steps of:
 a) mixing water and ethylene glycol to provide a solvent mixture, wherein the water is present, by weight, up to about 85% and the second solvent is present by weight, up to about 95%;   b) dissolving an ammonium salt in the solvent mixture; and   c) providing an acid in the solvent mixture.   
     
     
       26. The method of  claim 25  including selecting the ammonium salt from the group consisting of ammonium acetate, ammonium formate, ammonium hydrogen maleate, ammonium hydrogen phosphate, and mixtures thereof. 
     
     
       27. The method of  claim 25  including selecting the acid from the group consisting of citric acid, oxalic acid, formic acid, maleic acid, phosphoric acid, malonic acid, maltic acid, sulfuric acid, adipic acid, succinic acid, nitric acid, acetic acid, and mixtures thereof. 
     
     
       28. A method for providing a capacitor, comprising the steps of:
 a) providing an anode of tantalum;   b) providing a cathode of ruthenium oxide; and   c) activating the anode and the cathode with an electrolyte, the electrolyte comprising:
 i) a mixed solvent of water and ethylene glycol, wherein the water is present, by weight, up to about 85% and the ethylene glycol is present, by weight, up to about 95%; 
 ii) an ammonium salt dissolved in the solvent; and 
 iii) an acid. 
   
     
     
       29. The method of  claim 28  including providing the electrolyte having ammonium acetate present, by weight, up to about 50%. 
     
     
       30. The method of  claim 28  including providing the electrolyte having acetic acid present, by weight, up to about 80% and phosphoric acid present, by weight, up to about 6%. 
     
     
       31. The method of  claim 28  comprising a ruthenium oxide cathode and a tantalum anode. 
     
     
       32. The method of  claim 28  wherein the ruthenium oxide is provided on a titanium substrate. 
     
     
       33. An electrolyte for activating a capacitor, the electrolyte consisting essentially of:
 a) a mixed solvent of water and ethylene glycol; 
 b) a solute of ammonium acetate present, by weight, up to about 50%; and 
 c) a mixed acid of acetic acid and phosphoric acid. 
 
     
     
       34. An electrolyte for activating a capacitor, the electrolyte consisting essentially of:
 a) a mixed solvent of water and ethylene glycol; 
 b) a solute of ammonium acetate; and 
 c) a mixed acid of acetic acid and phosphoric acid, wherein the acetic acid is present, by weight, up to about 80% and the phosphoric acid is present, by weight, up to about 6%. 
 
     
     
       35. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising:
 i) a mixed solvent of water and ethylene glycol; 
 ii) an ammonium salt dissolved in the solvent, wherein the ammonium salt is ammonium acetate present in the electrolyte at a concentration up to about 50%, by weight; and 
 iii) an acid. 
   
     
     
       36. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising:
 i) a mixed solvent of water and ethylene glycol; 
 ii) an ammonium salt dissolved in the solvent; and 
 iii) a mixed acid of acetic acid and phosphoric acid, wherein the acetic acid is present at a concentration up to about 80%, by weight, and phosphoric acid is present at a concentration up to about 6%, by weight. 
   
     
     
       37. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising, by weight, about 49.41% de-ionized water, about 19.45% ethylene glycol, about 15.55% ammonium acetate, about 0.31% phosphoric acid and about 15.28% acetic acid.   
     
     
       38. The capacitor of  claim 37  rated to about 175 volts. 
     
     
       39. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising, by weight, about 44.46% de-ionized water, about 34.61% ethylene glycol, about 10.04% ammonium acetate, about 0.51% phosphoric acid and about 10.39% acetic acid.   
     
     
       40. The capacitor of  claim 39  rated to about 200 volts. 
     
     
       41. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising, by weight, about 46.52% de-ionized water, about 36.05% ethylene glycol, about 8.29% ammonium acetate, about 0.44% phosphoric acid and about 8.70% acetic acid.   
     
     
       42. The capacitor of  claim 41  rated to about 250 volts. 
     
     
       43. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising, by weight, about 46.59% de-ionized water, about 41.45% ethylene glycol, about 5.60% ammonium acetate, about 0.48% phosphoric acid and about 5.88% acetic acid.   
     
     
       44. The capacitor of  claim 43  rated to about 250 volts. 
     
     
       45. A capacitor, which comprises:
 a) an anode of a valve metal;   b) a cathode of ruthenium oxide; and   c) an electrolyte activating the anode and the cathode, the electrolyte comprising, by weight, about 51.94% de-ionized water, about 40.29% ethylene glycol, about 3.54% ammonium acetate, about 0.59% phosphoric acid and about 3.64% acetic acid.   
     
     
       46. The capacitor of  claim 45  rated to about 300 volts. 
     
     
       47. A method for providing a capacitor, comprising the steps of:
 a) providing an anode of tantalum;   b) providing a cathode of ruthenium oxide; and   c) activating the anode and the cathode with an electrolyte, the electrolyte comprising:
 i) a mixed solvent of water and ethylene glycol; 
 ii) an ammonium salt dissolved in the solvent, wherein the ammonium salt is ammonium acetate present, by weight, up to about 50%; and 
 iii) an acid. 
   
     
     
       48. A method for providing a capacitor, comprising the steps of:
 a) providing an anode of tantalum;   b) providing a cathode of ruthenium oxide; and   c) activating the anode and the cathode with an electrolyte, the electrolyte comprising:
 i) a mixed solvent of water and ethylene glycol; 
 ii) an ammonium salt dissolved in the solvent; and 
 iii) a mixed acid of acetic acid and phosphoric acid, wherein the acetic acid is present at a concentration up to about 80%, by weight, and the phosphoric acid is present at a concentration up to about 6%, by weight. 
   
     
     
       49. The electrolyte of claim 33, having a conductivity in the range of 13.7 to 47.5 mS/cm. 
     
     
       50. The electrolyte of claim 33, having a resistivity in the range of 21.0 to 72.8 Ωcm. 
     
     
       51. The electrolyte of claim 33, having an anode breakdown voltage in the range of 245 to 320 volts when the breakdown voltage is measured using a tantalum anode. 
     
     
       52. The electrolyte of claim 51, wherein the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       53. The electrolyte of claim 33, wherein the electrolyte has:
 a) a conductivity in a range of 29.6 to 47.5 mS/cm; and   b) an anode breakdown voltage in a range of 245 to 270 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       54. The electrolyte of claim 53, wherein the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       55. The electrolyte of claim 53, having a pH in a range of 4.87 to 4.89. 
     
     
       56. The electrolyte of claim 53, having a resistivity in a range of 21.0 to 33.8 Ωcm. 
     
     
       57. The electrolyte of claim 53, wherein the electrolyte does not generate gas at 85° C. 
     
     
       58. The electrolyte of claim 33, wherein the electrolyte has:
 a) a conductivity in a range of 25.6 to 29.6 mS/cm; and   b) an anode breakdown voltage in a range of 270 to 275 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       59. The electrolyte of claim 58, wherein the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       60. The electrolyte of claim 58, having a pH in a range of 4.83 to 4.87. 
     
     
       61. The electrolyte of claim 58, having a resistivity in a range of 33.8 to 39.1 Ωcm. 
     
     
       62. The electrolyte of claim 58, wherein the electrolyte does not generate gas at 85° C. 
     
     
       63. The electrolyte of claim 33, wherein the electrolyte has:
 a) a conductivity in a range of 18.8 to 25.6 mS/cm; and   b) an anode breakdown voltage in a range of 275 to 300 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       64. The electrolyte of claim 63, wherein the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       65. The electrolyte of claim 63, having a pH in a range of 4.80 to 4.83. 
     
     
       66. The electrolyte of claim 63, having a resistivity in a range of 39.1 to 53.3 Ωcm. 
     
     
       67. The electrolyte of claim 63, wherein the electrolyte does not generate gas at 85° C. 
     
     
       68. The electrolyte of claim 33, wherein the electrolyte has:
 a) a conductivity in a range of 13.7 to 18.8 mS/cm; and   b) an anode breakdown voltage in a range of 300 to 320 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       69. The electrolyte of claim 68, wherein the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       70. The electrolyte of claim 68, having a pH in a range of 4.70 to 4.80. 
     
     
       71. The electrolyte of claim 68, having a resistivity in a range of 53.3 to 72.8 Ωcm. 
     
     
       72. The electrolyte of claim 68, wherein the electrolyte does not generate gas at 85° C. 
     
     
       73. The electrolyte of claim 33, wherein the electrolyte has:
 a) a pH in a range of about 3 to 6;   b) a resistivity in a range of 21.0 to 72.8 Ωcm; and   c) an anode breakdown voltage in the range of 245 to 320 volts when the anode breakdown voltage is measured using a tantalum anode.   
     
     
       74. The electrolyte of claim 73, wherein the electrolyte has said pH and said resistivity when the electrolyte is at an operating temperature. 
     
     
       75. The electrolyte of claim 33, wherein:
 a) water is in the range of about 44.46% to about 51.94%, by weight;   b) ethylene glycol is in the range of about 19.45% to about 41.45%, by weight;   c) ammonium acetate is in the range of about 3.54% to about 15.55%, by weight;   d) acetic acid is in the range of about 3.64% to about 15.28%, by weight; and   e) phosphoric acid is in the range of about 0.31% to about 0.59%, by weight.   
     
     
       76. The electrolyte of claim 75, wherein the electrolyte has a pH in a range of 4.7 to 4.89. 
     
     
       77. The electrolyte of claim 75, wherein the electrolyte has a conductivity in a range of 13.7 mS/cm to 47.5 mS/cm. 
     
     
       78. The electrolyte of claim 75, wherein the electrolyte has a resistivity in a range of 21.0 to 72.8 Ωcm. 
     
     
       79. The electrolyte of claim 75, wherein the electrolyte does not generate gas at 85° C. 
     
     
       80. An electrolyte for a capacitor comprising a tantalum anode, the electrolyte consisting of:
 a) a mixed solvent of water and ethylene glycol;   b) a solute of ammonium acetate; and   c) a mixed acid of acetic acid and phosphoric acid, wherein:
 i) water is in a range of about 44.46% to about 51.94%, by weight; 
 ii) ethylene glycol is in a range of about 19.45% to about 41.45%, by weight; 
 iii) ammonium acetate is in a range of about 3.54% to about 15.55%, by weight; 
 iv) phosphoric acid is in a range of about 0.31% to about 0.59%, by weight; and 
 v) acetic acid is in a range of about 3.64% to about 15.28%, by weight. 
   
     
     
       81. A capacitor, which comprises:
 a) an anode comprising tantalum;   b) a cathode of ruthenium oxide; and   c) an electrolyte contacting the anode and the cathode, the electrolyte consisting of:
 i) a mixed solvent of water and ethylene glycol, wherein the water is present, by weight, up to about 85% and the ethylene glycol is present, by weight, up to about 95%; 
 ii) a solute of ammonium acetate present, by weight, up to about 50%; and 
 iii) a mixed acid of acetic acid and phosphoric acid, wherein the acetic acid is present, by weight, up to about 80% and the phosphoric acid is present, by weight, up to about 6%. 
   
     
     
       82. The capacitor of claim 81, wherein the electrolyte has a pH between about 1 to about 7. 
     
     
       83. The capacitor of claim 81, wherein the electrolyte has a conductivity in the range of 13.7 to 47.5 mS/cm. 
     
     
       84. The capacitor of claim 81, wherein the electrolyte has a resistivity in the range of 21.0 to 72.8 Ωcm. 
     
     
       85. The capacitor of claim 81, wherein the electrolyte has an anode breakdown voltage in the range of 245 to 320 volts when the breakdown voltage is measured using a tantalum anode. 
     
     
       86. The capacitor of claim 85, wherein the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       87. The capacitor of claim 81, wherein the electrolyte has:
 a) a conductivity in a range of 29.6 to 47.5 mS/cm; and   b) an anode breakdown voltage in a range of 245 to 270 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       88. The capacitor of claim 87, wherein in the electrolyte, the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       89. The capacitor of claim 87, wherein the electrolyte has a pH in a range of 4.87 to 4.89. 
     
     
       90. The capacitor of claim 87, wherein the electrolyte has a resistivity in a range of 21.0 to 33.8 Ωcm. 
     
     
       91. The capacitor of claim 87, wherein the electrolyte does not generate gas at 85° C. 
     
     
       92. The capacitor of claim 81, wherein the electrolyte has:
 a) a conductivity in a range of 25.6 to 29.6 mS/cm; and   b) an anode breakdown voltage in a range of 270 to 275 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       93. The capacitor of claim 82, wherein in the electrolyte, the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       94. The capacitor of claim 82, wherein the electrolyte has a pH in a range of 4.83 to 4.87. 
     
     
       95. The capacitor of claim 82, wherein the electrolyte has a resistivity in a range of 33.8 to 39.1 Ωcm. 
     
     
       96. The capacitor of claim 82, wherein the electrolyte does not generate gas at 85° C. 
     
     
       97. The capacitor of claim 81, wherein the electrolyte has:
 a) a conductivity in a range of 18.8 to 25.6 mS/cm; and   b) an anode breakdown voltage in a range of 275 to 300 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       98. The capacitor of claim 97, wherein in the electrolyte, the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       99. The capacitor of claim 97, wherein the electrolyte has a pH in a range of 4.80 to 4.83. 
     
     
       100. The capacitor of claim 97, wherein the electrolyte has a resistivity in a range of 39.1 to 53.3 Ωcm. 
     
     
       101. The capacitor of claim 97, wherein the electrolyte does not generate gas at 85° C. 
     
     
       102. The capacitor of claim 81, wherein the electrolyte has:
 a) a conductivity in a range of 13.7 to 18.8 mS/cm; and   b) an anode breakdown voltage in a range of 300 to 320 volts when the breakdown voltage is measured using a tantalum anode.   
     
     
       103. The capacitor of claim 102, wherein in the electrolyte, the anode breakdown voltage is measured when the electrolyte is at an operating temperature. 
     
     
       104. The capacitor of claim 102, wherein the electrolyte has a pH in a range of 4.70 to 4.80. 
     
     
       105. The capacitor of claim 102, wherein the electrolyte has a resistivity in a range of 53.3 to 72.8 Ωcm. 
     
     
       106. The capacitor of claim 102, wherein the electrolyte does not generate gas at 85° C. 
     
     
       107. The capacitor of claim 81, wherein the electrolyte has:
 a) a pH in a range of about 3 to 6, a resistivity in a range of 21.0 to 72.8 Ωcm, and an anode breakdown voltage in the range of 245 to 320 volts; and   b) the anode breakdown voltage is measured using a tantalum anode.   
     
     
       108. The capacitor of claim 107, wherein the electrolyte has said pH and said resistivity when the electrolyte is at an operating temperature. 
     
     
       109. The capacitor of claim 81, wherein in the electrolyte:
 a) water is in the range of about 44.46% to about 51.94%, by weight;   b) ethylene glycol is in the range of about 19.45% to about 41.45%, by weight;   c) ammonium acetate is in the range of about 3.54% to about 15.55%, by weight;   d) acetic acid is in the range of about 3.64% to about 15.28%, by weight; and   e) phosphoric acid is in the range of about 0.31% to about 0.59%, by weight.   
     
     
       110. The capacitor of claim 109, wherein the electrolyte has a pH in a range of 4.7 to 4.89. 
     
     
       111. The capacitor of claim 109, wherein the electrolyte has a conductivity in a range of 13.7 mS/cm to 47.5 mS/cm. 
     
     
       112. The capacitor of claim 109, wherein the electrolyte has a resistivity in a range of 21.0 to 72.8 Ωcm. 
     
     
       113. The capacitor of claim 109, wherein the electrolyte does not generate gas at 85° C. 
     
     
       114. The electrolyte of claim 33, having a pH between about 1 to about 7. 
     
     
       115. A capacitor, which comprises:
 a) an anode of tantalum;   b) a cathode of ruthenium oxide; and   c) an electrolyte contacting the anode and the cathode, the electrolyte consisting of:
 i) a mixed solvent of water and ethylene glycol; 
 ii) a solute of ammonium acetate present, by weight, up to about 50%; and 
 iii) a mixed acid of acetic acid and phosphoric acid. 
   
     
     
       116. A capacitor, which comprises:
 a) an anode of tantalum;   b) a cathode of ruthenium oxide; and   c) an electrolyte contacting the anode and the cathode, the electrolyte consisting of:
 i) a mixed solvent of water and ethylene glycol; 
 ii) a solute of ammonium acetate; and 
 iii) a mixed acid of acetic acid and phosphoric acid, wherein the acetic acid is present at a concentration up to about 80%, by weight, and phosphoric acid is present at a concentration up to about 6%, by weight. 
   
     
     
       117. A method for providing a capacitor, comprising the steps of:
 a) providing an anode of tantalum;   b) providing a cathode of ruthenium oxide; and   c) contacting the anode and the cathode with an electrolyte, the electrolyte consisting of:
 i) a mixed solvent of water and ethylene glycol; 
 ii) a solute of ammonium acetate present, by weight, up to about 50%; and 
 iii) a mixed acid of acetic acid and phosphoric acid. 
   
     
     
       118. A method for providing a capacitor, comprising the steps of:
 a) providing an anode of tantalum;   b) providing a cathode of ruthenium oxide; and   c) contacting the anode and the cathode with an electrolyte, the electrolyte consisting of:
 i) a mixed solvent of water and ethylene glycol; 
 ii) a solute of ammonium acetate; and 
 iii) a mixed acid of acetic acid and phosphoric acid, wherein the acetic acid is present at a concentration up to about 80%, by weight, and the phosphoric acid is present at a concentration up to about 6%, by weight.