Solid Electrolyte Composition for Low-ESR Capacitors
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Solution Overview
Problem
Existing solid electrolytic capacitors face challenges in reducing leak current and equivalent series resistance (ESR) at high use frequencies, particularly due to insufficient oxide film repair capabilities and the impairment of electroconductivity caused by polyglycerin entering the electroconductive polymer compound particles.
Innovation Solution
Incorporating a polyol compound with a small molecular weight and multiple hydroxy groups as a first water-soluble compound, along with a glycol compound as a second water-soluble compound in the solid electrolyte, to enhance the oxide film repair capability and reduce ESR by improving the alignment and conductivity of the electroconductive polymer compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyglycerin is contained in the solid electrolyte to remain after solvent removal, then the oxide film repair capability is enhanced, but the electroconductivity is impaired due to polyglycerin entering among particles of the electroconductive polymer compound
Solution Approach 1:
The patent changes the molecular weight parameter of the polyol compound from high (polyglycerin) to low (molecular weight 200 or less), which fundamentally alters its behavior. The low molecular weight polyol can penetrate and repair oxide films effectively while being small enough not to block electroconductive polymer particles, thus resolving the contradiction between repair capability and electroconductivity
Solution Approach 2:
The patent extracts the problematic component (high molecular weight polyglycerin) and replaces it with a modified version (low molecular weight polyol compound). This extraction of the harmful aspect while retaining the beneficial function allows the system to achieve oxide film repair without sacrificing electroconductivity
2Ease of manufacture
If glycerin is used as the water-soluble compound in the dispersing liquid, then the manufacturing process is simplified, but glycerin is removed along with the solvent in the formation of the solid electrolyte, reducing oxide film repair capability
Solution Approach 1:
The patent changes the molecular weight parameter of the polyol compound to 200 or less, which provides a new property: the ability to remain in the solid electrolyte after solvent removal while still being water-soluble enough to repair oxide films. This parameter change allows the compound to achieve dual functionality that glycerin cannot provide
3Loss of energy
If the ESR is reduced by using an electroconductive polymer compound, then the capacitor performance is improved, but the ESR cannot be reduced to the target level for solid electrolytic capacitors with further reduced ESR at use frequencies of 100 kHz
Solution Approach 1:
The patent creates a composite solid electrolyte system combining electroconductive polymer compound particles with low molecular weight polyol compound. This composite structure allows the polyol to fill gaps between particles and provide additional conduction pathways, achieving lower ESR at high frequencies than the electroconductive polymer alone can provide
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 proposed configuration achieves a significant reduction in ESR at high frequencies, enhances leak current reduction, and maintains electrostatic capacity stability under high temperature conditions, preventing electrode foil deterioration.
Implementation Method 1
a polyol compound having a molecular weight of less than 200 and a number of hydroxy groups of 4 or more as a first water-soluble compound to improve the contact to the oxide film
Implementation Method 2
a solid electrolyte formed of an electroconductive polymer compound in a fine particle form
Implementation Method 3
a water-soluble compound solution containing a second water-soluble compound having an order of the average molecular weight regulated with respect to the polyol compound is used
Data Source
AI summary
A solid electrolytic capacitor (1) includes an anode foil (2a) having formed thereon an oxide film, a cathode foil (2c), and a separator (2d), and is equipped with a solid electrolyte (20) formed of an electroconductive polymer compound in a fine particle form, and a water-soluble compound solution (30) introduced to surround the solid electrolyte (20), the solid electrolyte (20) contains a polyol compound having a molecular weight of less than 200 and a number of hydroxy groups of 4 or more as a first water-soluble compound (2f1), the water-soluble compound solution (30) contains one kind or multiple kinds of a glycol compound in a liquid form as a second water-soluble compound (2f2), and the second water-soluble compound (2f2) has an average molecular weight of less than 400.