GB1003532A - - Google Patents

Abstract

1,003,532. Electrolytic capacitors. TELEGRAPH CONDENSER CO. Ltd. May 19, 1964 [June 7, 1963], No. 20604/64. Drawings to Specification. Heading H1M. An electrolyte for an electrolytic capacitor includes a non-metallic cation having at least one group reducible by hydrogen evolved at the capacitor cathode. This enables the build up of pressure inside the capacitor due to the release of hydrogen at the cathode to be avoided. The solvent for the electrolyte may be any of those usually used, e.g. water, ethylene glycol, dimethylformamide, dimethylacetamide or propylene carbonate. The electrolyte also contains a film-forming anion, which may be taken from the pentaborates, phosphates, condensed polyphosphates, nitrates, thiocyanates and picrates. The reducible group can be contained in a non-metallic cation of the quaternary ammonium, quaternary phosphonium, sulphonium or arsonium type. Preferred reducible substituents include nitro, quinono, carboxyl, nitroso, azoxy, azo and nitrile groups. Thus examples of suitable cations include N-(2,4 dinitrophenyl) pyridinium, p-nitrophenyl trimethyl ammonium, p- and m-nitrobenzyl triethyl ammonium, α- and #-anthraquinonyl triethyl ammonium, phenacyl triethylammonium. An example of a suitable salt for use in the electrolyte system is N-(2,4-dinitrophenyl) pyridinium pentaborate. Other examples are given in the Specification. The electrolyte may be used with rolled tantalum foil capacitors having a Kraft paper spacing. Other metals such as aluminium or zirconium may be used. The rolled unit is enclosed in a Kraft paper tube enclosed within a can of silver or silver-plated copper and sealed with resinous end seals. Alternatively the capacitor anode may be an etched tantalum wire positioned inside a silver can acting as cathode.