High Voltage Capacitor Electrolyte ESR Reduction
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Solution Overview
Problem
High voltage electrolytic capacitors used in implantable medical devices, such as implantable cardioverter defibrillators, face challenges in achieving high energy density and reliability due to high equivalent series resistance (ESR) in multi-anode configurations and the need for high operating voltages, which complicates device design and size reduction.
Innovation Solution
A conductive electrolyte composition based on γ-butyrolactone, acetonitrile, and glycerol, optionally with additional components like diisopropylethylamine and 3-nitrobenzyl alcohol, is used to reduce ESR and enhance conductivity, allowing for reliable operation at very high voltages without excessive increase in resistance, enabling the use of a single capacitor in ICDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a multi-anode stack configuration is used to increase energy density and reduce device size, then the number of cathodes and paper spacers is reduced, but the equivalent series resistance (ESR) increases due to the tortuous charge path through outer anodes
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrolyte by selecting specific solvents (γ-butyrolactone, N-methylpyrrolidinone) with high dielectric constants and appropriate viscosities, along with specific cosolvents and alcohol additives. This parameter optimization enables the electrolyte to maintain low ESR even in multi-anode configurations where charge must flow through multiple anode layers, thereby resolving the contradiction between energy density and ESR.
Solution Approach 2:
The patent employs a composite electrolyte system combining multiple components: primary solvents (γ-butyrolactone, N-methylpyrrolidinone), cosolvents (acetonitrile, dimethyl sulfoxide), and alcohol additives (glycerol, diethylene glycol monoalkyl ether, 2-alkoxy ethanol). This composite formulation synergistically achieves both high conductivity for low ESR and appropriate viscosity for effective charge transport through the tortuous path of multi-anode stacks.
2Device complexity
If the operating voltage is increased to allow a single capacitor design in ICDs, then packaging efficiency is improved and device size is reduced, but the capacitor requires operating voltages well over 400 Volts which demands very high voltage components
Solution Approach 1:
The patent changes the electrolyte's electrical parameters by selecting solvents with high dielectric constants (γ-butyrolactone, N-methylpyrrolidinone) and optimizing the composition ratios to achieve both very high breakdown voltage (exceeding 400V) and high ionic conductivity. This enables the capacitor to operate at high voltages with improved packaging efficiency while maintaining reliability through the electrolyte's inherent electrical properties.
3Reliability
If very low resistivity electrolytes are used in multi-anode configurations, then the increase in ESR is reduced, but the electrolyte viscosity and other physical properties must be optimized to prevent excessive ESR
Solution Approach 1:
The patent systematically optimizes multiple electrolyte parameters simultaneously: solvent type (γ-butyrolactone, N-methylpyrrolidinone), cosolvent selection (acetonitrile, dimethyl sulfoxide), alcohol additives (glycerol, diethylene glycol monoalkyl ether, 2-alkoxy ethanol), and their respective concentrations. This multi-parameter optimization achieves the dual goal of very low resistivity for ESR control while maintaining appropriate viscosity and other physical properties for manufacturability and performance.
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 electrolyte composition achieves low viscosity and high conductivity, reducing ESR and increasing reliability, enabling capacitors to function effectively at voltages exceeding 500 volts, potentially allowing for a single capacitor design in ICDs, thus simplifying construction and improving packaging efficiency.
Implementation Method 1
A conductive electrolyte composition based on γ-butyrolactone, acetonitrile, and glycerol, optionally with additional components like diisopropylethylamine and 3-nitrobenzyl alcohol, is used to reduce ESR and enhance conductivity
Data Source
AI summary
An electrolyte including γ-butyrolactone, a cosolvent and an alcohol is disclosed, which may be used in an electrolytic capacitor with very high operating voltage. Optional additional additives are added to the electrolyte to enhance its conductivity and reliability.