Planar Anode for High Voltage Wet Electrolytic Capacitors
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Solution Overview
Problem
High voltage electrolytic capacitors used in implantable medical devices face challenges in achieving high energy density and volumetric efficiency due to high equivalent series resistance (ESR) and sensitivity to frequency, particularly at high voltages, which limits their size reduction and integration in medical devices.
Innovation Solution
A planar anode for high voltage wet electrolytic capacitors is developed, formed from anodically oxidized pellets made from pressed and sintered flake particles, which are oriented perpendicular to the anode lead wire, allowing for a thin, high-aspect-ratio structure that reduces ESR and increases energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple anodes are stacked together to increase energy density, then the number of anodes increases and device size reduces, but the path through anodes becomes tortuous and equivalent series resistance increases
Solution Approach 1:
The anode is segmented into multiple thin planar layers stacked together, with each layer having thickness of 5mm or less. This segmentation allows charge to flow through multiple shorter paths rather than one long tortuous path, reducing overall ESR while maintaining high energy density through the stacked configuration
Solution Approach 2:
The anodes are arranged in a stacked configuration along the thickness dimension rather than being connected in series along a single tortuous path. This dimensional arrangement allows charge to flow through multiple parallel paths across the stacked layers, reducing equivalent series resistance while increasing the effective surface area for energy storage
2Quantity of substance
If the operating voltage of the capacitor is increased to reduce device size, then the number of capacitors needed reduces, but the surface area decreases and capacitance reduces
Solution Approach 1:
The capacitor utilizes a stacked anode configuration that increases the effective surface area by adding layers in the thickness dimension. This allows the capacitor to maintain high capacitance at higher operating voltages, eliminating the need for multiple capacitors in series while preserving sufficient surface area for energy storage
3Area of stationary object
If porous sintered pellets are used to increase surface area, then internal surface area increases, but the pellets are larger in size and volumetric efficiency decreases
Solution Approach 1:
Instead of using a single large porous pellet, the anode is segmented into multiple thin planar layers. Each layer maintains a manageable thickness of 5mm or less, improving volumetric efficiency while the cumulative surface area of all layers provides sufficient area for high capacitance and energy density
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 solution results in a capacitor with improved volumetric efficiency, high energy density, and reduced ESR, enabling smaller, more efficient capacitors suitable for medical devices like implantable defibrillators.
Implementation Method 1
The anode includes an anodically oxidized pellet formed from a pressed and sintered powder
Implementation Method 2
Etching is normally carried out either by the method (chemical etching) of conducting immersion into a solution of hydrochloric acid or by the method (electrochemical etching) of carrying out electrolysis in an aqueous solution of hydrochloric acid
Data Source
AI summary
A relatively thin planar anode for use in a wet electrolytic capacitor is provided. Through a combination of specific materials and processing techniques, the present inventors have surprisingly discovered that the resulting anode may possess a high volumetric efficiency, yet still be able to operate at a high voltage and capacitance, resulting in a capacitor with a high energy density. The anode is a pressed pellet formed from an electrically conductive powder that contains a plurality of particles (including agglomerates thereof) having a flake-like morphology. The present inventors have discovered that such a morphology can optimize packing density, which reduces the thickness of the anode and improves volumetric efficiency. Such particles can provide a short transmission line between the outer surface and interior of the anode and a highly continuous and dense wire-to-anode connection with high conductivity. The particles may also increase the breakdown voltage and help lower ESR.