Gelled Wet Electrolytic Capacitor Electrolyte for Low Leakage Stability
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Solution Overview
Problem
Existing wet electrolytic capacitors for implantable medical devices face challenges with high DCL and sensitivity to frequency, particularly at high voltages, and gelled electrolytes exhibit instability or degradation during gelation.
Innovation Solution
A wet electrolytic capacitor with an anodically oxidized pellet anode and a gel-forming electrolyte containing specific concentrations of ammonium salt, inorganic oxide particles, acid, and gelation activator, which forms a viscoelastic gel with controlled gelation times and neutral pH, maintaining low leakage current and high conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gelled electrolytes are used to overcome high DCL and frequency sensitivity, then electrical stability improves, but gelation time becomes unpredictable and electrolyte stability degrades
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by specifying precise concentrations of ammonium salt (1-40 wt%), acid (0.01-10 wt%), and gelation activator (0.01-1 wt%). These parameter adjustments control the gelation process to occur within a predictable timeframe while maintaining electrical stability, resolving the contradiction between reliability improvement and time loss.
Solution Approach 2:
The patent introduces an ammonium salt of an organic acid as an intermediary substance that mediates the gelation process. This intermediary enables controlled gelation at neutral pH without requiring extreme conditions or external energy input, making the gelation time predictable while maintaining electrolyte stability and electrical performance.
2Reliability
If gelled electrolytes are used to improve electrical properties, then capacitance stability improves, but electrolyte degradation occurs
Solution Approach 1:
The patent maintains electrolyte stability by controlling the pH to be neutral (using ammonium salt buffers) and specifying precise concentrations of stabilizing components. The ammonium salt concentration (1-40 wt%) and acid concentration (0.01-10 wt%) are carefully balanced to prevent degradation while ensuring capacitance stability, resolving the contradiction between reliability and compositional stability.
Solution Approach 2:
The patent creates a composite electrolyte system combining ammonium salt, organic acid, inorganic oxide particles, and gelation activator in specific proportions. This composite formulation provides mutual stabilization where each component supports the others, preventing degradation while maintaining electrical properties and capacitance stability over extended periods.
3Object-generated harmful factors
If neutral pH gelled electrolyte is used to reduce leakage current, then DCL decreases to 625 μA or less, but gelation control becomes challenging
Solution Approach 1:
The patent uses ammonium salt as an intermediary that enables gelation at neutral pH without requiring strong acids or bases. This intermediary facilitates controlled gelation while maintaining low leakage current (625 μA or less), resolving the contradiction between reducing harmful leakage current and maintaining ease of manufacture through predictable gelation control.
Solution Approach 2:
The electrolyte composition is designed to self-gel within a predictable timeframe without requiring external energy input or complex catalysis. The ammonium salt, acid, and gelation activator work together to automatically control the gelation process at neutral pH, making manufacturing easy while achieving low leakage current specifications.
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 capacitor achieves low leakage current (DCL) and high energy density without high equivalent series resistance (ESR), with stable electrical properties over extended periods, even at elevated temperatures.
Implementation Method 1
inducing gelation of the mixture so that it exhibits a first phase angle δ of from about 50° to 90°; placing the gelled mixture into communication with an anode, cathode, or both
Implementation Method 2
an anode comprising an anodically oxidized pellet formed from a pressed and sintered powder
Implementation Method 3
the capacitance of the electrolytic capacitor is determined by the extent of roughing (the surface area) of the anode foil and the thickness and the dielectric constant of the oxide film
Implementation Method 4
The working electrolyte is in the form of a gel and has a pH value of from about 5.0 to about 8.0. Moreover, the wet electrolytic capacitor exhibits a leakage current (DCL) of about 625 μA or less
Data Source
AI summary
A wet electrolytic capacitor is provided. The capacitor contains an anode comprising an anodically oxidized pellet formed from a pressed and sintered powder, a cathode, and a working electrolyte in communication with the anode and the cathode. The working electrolyte is in the form of a gel and comprises an ammonium salt of an organic acid, inorganic oxide particles, a gelation activator, an acid, and a solvent system that comprises water. The working electrolyte has a pH value of from about 5.0 to about 8.0.