Solid Electrolytic Capacitor Electrolyte for ESR Stability
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Solution Overview
Problem
In solid electrolytic capacitors, the use of amines with high acid dissociation constants leads to increased equivalent series resistance (ESR) due to undoping of the conductive polymer dopant, and the presence of hydroxy groups in these amines promotes esterification reactions, limiting solvent choice and conductivity.
Innovation Solution
A solid electrolytic capacitor design that includes a solvent and solute with an oxygen-containing amine lacking hydroxy groups, along with a polyol compound, to prevent undoping and esterification, maintaining conductivity over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an amine with high acid dissociation constant (pKa) is used as the basic component of the solute, then the conductivity is improved, but the equivalent series resistance (ESR) increases due to undoping of the dopant
Solution Approach 1:
The patent changes the chemical parameters of the amine by selecting compounds with specific pKa values (14.0 or less) and specific structural features (no hydroxy group). This parameter optimization allows the amine to maintain appropriate conductivity while preventing excessive undoping of the dopant, thus resolving the contradiction between conductivity and ESR increase.
Solution Approach 2:
The patent specifies local structural characteristics of the amine molecule, particularly the absence of hydroxy groups and the presence of specific functional groups. This local quality control prevents esterification reactions while maintaining the desired electrical properties, allowing the amine to function effectively without causing harmful side reactions.
2Object-generated harmful factors
If an amine with hydroxy group is used as the basic component, then the ESR increase is suppressed to some extent, but the conductivity easily decreases due to esterification with the acid component
Solution Approach 1:
The patent extracts the harmful hydroxy group from the amine structure while retaining the beneficial basic properties. By selecting amines without hydroxy groups, the patent eliminates the source of esterification reactions that would otherwise reduce conductivity, while still maintaining the ability to suppress dopant undoping through appropriate pKa selection.
Solution Approach 2:
The patent converts the potential harm of amine-acid reactions by selecting amines with specific properties (low pKa, no hydroxy group). These properties prevent harmful esterification while allowing controlled interaction with the dopant, transforming what could be a harmful reaction pathway into a beneficial doping mechanism that maintains conductivity.
3Object-generated harmful factors
If an amine with hydroxy group is used, then the ESR increase is suppressed, but the solvent selection is limited to aprotic solvents due to promoted esterification reaction
Solution Approach 1:
The patent changes the chemical parameters of the amine by eliminating hydroxy groups and selecting specific pKa values. This modification removes the limitation on solvent selection, allowing the use of protic solvents that would otherwise promote esterification. The amine maintains its ability to suppress ESR increase while gaining versatility in solvent compatibility.
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 design effectively suppresses ESR increase and ensures a long capacitor lifetime by preventing undoping and esterification, even under high-temperature conditions.
Implementation Method 1
the basic component contains an amine represented by the general formula (1)... undoping of the dopant of the conductive polymer can be suppressed
Implementation Method 2
the amine described in PTL 2 has a hydroxy group at the end and thus has a problem because the conductivity easily decreases due to esterification of the amine and the acid component in the electrolytic solution
Data Source
AI summary
A solid electrolytic capacitor includes a solid electrolyte and an electrolyte between electrode foils, and a method for manufacturing the solid electrolytic capacitor can suppress a rise in ESR and realize a longer life. As a solution, in a solid electrolytic capacitor, a basic component of an electrolytic solution contains an amine represented by formula (1). In the formula, R1 represents hydrogen or an alkyl group, R2 represents an alkylene group, R3 represents an alkyl group. n represents an integer of 1 to 100, wherein R2's may be the same or different when n is 2 or more. m represents an integer of 1 to 3, wherein R1's may be the same or different when m is 1, and when m is 2 or 3, R2's may be the same or different, n's may be the same or different, and R3's may be the same or different.NR1(3-m)(—(R2O)n—R3)m (1)