Conductive Polymer Electrolyte for Low-ESR Capacitor Stability
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Solution Overview
Problem
Existing electrically conductive polymer solutions for electrolytic capacitors face challenges in achieving high capacity and low equivalent series resistance (ESR) characteristics, with existing compositions tending to aggregate when made acidic, impairing physical properties and making it difficult to maintain low ESR over time.
Innovation Solution
An electrically conductive polymer solution containing specific structural units of polythiophene, epoxy compounds, and water, with a pH of 1.5 to 5.0, is applied and dried to form a film on a dielectric oxide film, producing an electrolytic capacitor with improved stability and low ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrically conductive polymer solution is made acidic to improve conductivity, then the ESR characteristic is improved, but the polymer aggregates and physical properties are impaired
Solution Approach 1:
The patent introduces a specific epoxy compound as an intermediary substance that mediates between the acidic environment (needed for conductivity) and the polymer structure (sensitive to aggregation). The epoxy compound has a pKa value of 5.0 to 9.0, which allows it to buffer the solution and prevent excessive acidification that would cause aggregation, while still permitting the necessary acidic conditions for low ESR performance.
Solution Approach 2:
The patent changes the pH parameter to a specific range of 2.0 to 4.0, which is optimized to balance conductivity and stability. Additionally, the epoxy compound concentration is controlled at 0.01 to 5.0 wt% relative to the polythiophene, and the pKa of the epoxy compound is selected within 5.0 to 9.0, creating a multi-parameter optimization that resolves the contradiction between acidity-induced conductivity and aggregation prevention.
2Quantity of substance
If existing polythiophene-based solutions are used to achieve conductivity, then the capacitor capacity is improved, but the ESR characteristic deteriorates over time
Solution Approach 1:
The patent creates a composite system combining polythiophene (for high capacity) with a specifically selected epoxy compound (for ESR stability). This composite approach allows the polythiophene to provide the necessary capacitor capacity while the epoxy compound maintains structural integrity and prevents degradation over time, thereby stabilizing the ESR characteristic.
Solution Approach 2:
The epoxy compound acts as a protective intermediary that stabilizes the polythiophene structure during long-term operation. By controlling the epoxy compound's pKa and concentration, the patent prevents the polythiophene from degrading or aggregating over time, thus maintaining both capacity and ESR stability throughout the capacitor's operational lifetime.
3Stability of the object's composition
If the epoxy compound concentration is increased to improve stability, then the polymer aggregation is reduced, but the solution viscosity increases
Solution Approach 1:
The patent optimizes the epoxy compound concentration to a specific range of 0.01 to 5.0 wt% relative to the polythiophene content. This parameter optimization ensures sufficient stability and aggregation resistance while preventing excessive viscosity increase that would complicate processing and application. The balanced concentration range resolves the contradiction between stability enhancement and viscosity control.
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 enables the production of electrolytic capacitors with high capacity and low ESR characteristics, maintaining these properties over time, suitable for use in electronic equipment with increased speed and frequency demands.
Implementation Method 1
an epoxy compound (B) having at least two epoxy groups; and water, a pH of the electrically conductive polymer solution being 1.5 to 5.0
Implementation Method 2
An electrically conductive polymer solution containing: 0.01% by mass to 10% by mass of polythiophene (A)... and water
Data Source
AI summary
Provided is an electrically conductive polymer solution which can provide an electrolytic capacitor having a high capacity and exhibiting a low ESR characteristic. An electrically conductive polymer solution is used which contains: 0.01 to 10% by mass of polythiophene (A) including at least one structural unit selected from the group consisting of a structural unit represented by a general formula (1) below and a structural unit represented by a general formula (2) below; 0.001 to 20% by mass of an epoxy compound (B) having at least two epoxy groups; and water, and in which a pH is 1.5 to 5.0,where R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.