Unetched Titanium Cathode Foil for Pulse Discharge Capacitors

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Solution Overview

Problem

Conventional chemically etched aluminum cathodes in electrolytic capacitors fail to provide sufficient capacitance for high energy density applications, especially in implantable cardioverter defibrillators, leading to issues like oxide buildup, electrolysis, and capacitor swelling due to inadequate cathode capacitance compared to anode capacitance.

Innovation Solution

Employing an unetched and uncoated titanium or similar metal alloy foil as the cathode in a multiple anode flat, stacked capacitor configuration, which inhibits gas production and maintains acceptable energy delivery without swelling, using a simple water and alcohol rinse for preparation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional chemically etched aluminum cathodes are used, then manufacturing is straightforward, but cathode capacitance is insufficient leading to oxide buildup, electrolysis, and capacitor swelling

Engineering Contradiction:

Improvecathode capacitance sufficiencyVSAvoidoxide buildup, electrolysis, and capacitor swelling

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the material parameter of the cathode from conventional chemically etched aluminum to unetched titanium or titanium alloy foil. This material substitution fundamentally alters the electrochemical properties, providing sufficient cathode capacitance to match anode capacitance, thereby preventing oxide buildup, electrolysis, and capacitor swelling while maintaining manufacturing simplicity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses unetched titanium foil that requires only simple water and alcohol rinse preparation, eliminating complex chemical etching processes. This simplifies manufacturing while achieving the desired capacitance performance, making the cathode more reliable without adding process complexity

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Quantity of substance

If multiple anodes are stacked to increase energy density, then capacitance per unit volume increases, but cathode capacitance becomes even more insufficient relative to anode capacitance

Engineering Contradiction:

Improvecapacitance per unit volumeVSAvoidcathode capacitance coverage

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent changes the cathode material parameter to unetched titanium or titanium alloy foil, which provides inherently higher and more stable capacitance. This enables the cathode to support multiple anode stacking configurations without becoming the limiting factor, allowing energy density to be increased while maintaining reliable capacitance coverage

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If cathode thickness is reduced to minimize device size, then volume is reduced, but cathode capacitance decreases further exacerbating the capacitance mismatch

Engineering Contradiction:

Improvecathode volumeVSAvoidcathode capacitance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the material composition parameter from aluminum to titanium or titanium alloy, which provides higher specific capacitance per unit volume. This material substitution allows the cathode to be made thinner to reduce overall device size while maintaining sufficient capacitance to match the anode, resolving the contradiction between miniaturization and capacitance sufficiency

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The use of unetched titanium foil as a cathode achieves sufficient capacitance and energy delivery in pulse discharge applications, with minimal swelling and reduced manufacturing complexity, sustaining over 2500 discharge cycles with negligible expansion.

Implementation Method 1

the capacitance of an electrolytic capacitor is provided by the anodes... the cathode capacitance must be nearly two orders of magnitude higher than the anode stack capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

an electrically conductive electrolyte... A typical electrolyte may be a mixture of a weak acid and a salt of a weak acid, preferably a salt of the weak acid employed, in a polyhydroxy alcohol solvent

Methodology Applied

Scientific EffectIon transport: Electrolyte

Data Source

PatentUS7715174B1Electrolytic capacitors with alternate cathode materials for use in pulse discharge applications

Publication Date: 2010.05.11 PACESETTER INC

AI summary

A metal or metal alloy foil substrate, preferably an unetched and uncoated metal or metal alloy foil substrate, such as but not limited to titanium, palladium, lead, nickel, tin, platinum, silver, gold, zirconium, molybdenum, tantalum, palladium-silver alloy, platinum-rhodium alloy, platinum-ruthenium alloy, and/or platinum-iridium alloy, is used as the cathode in an electrolytic capacitor, preferably an aluminum electrolytic capacitor having a multiple anode flat, stacked capacitor configuration. Despite a 120 Hz bridge capacitance measurement lower than with etched aluminum, the use of an unetched and uncoated metal or metal alloy foil cathode according to the present invention will inhibit gas production and not cause the capacitor to swell. Furthermore, an electrolytic capacitor built with a 30 micron unetched and uncoated foil cathode according to the present invention can deliver a stored to discharge energy ratio sufficient for use in pulse discharge applications, such as an in an ICD.