Capacitor with Functional Group Controlled Activated Carbon
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Solution Overview
Problem
Conventional electric double layer capacitors using γ-butyl-lactone or γ-valerolactone electrolytes face degradation issues during long-time charge/discharge cycles in harsh environments, leading to aged deterioration.
Innovation Solution
A capacitor design incorporating an electrolyte with a lactone compound and activated carbon electrodes, where the entire surface functional group amount at the average sectional area of pores is limited to 0.152 meq/g/nm², reducing the influence of surface functional groups on the electrolyte and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an electrolyte containing γ-butyl-lactone or γ-valerolactone is used to improve heat resistance and reduce gas generation, then the capacitor can operate in high-temperature atmospheres, but the capacitor suffers from aged deterioration during long-time charge/discharge cycles in harsh environments
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by specifying precise compositional ratios (γ-butyrolactone 10-30 vol%, γ-valerolactone 70-90 vol%, lithium salt 0.5-2.0 mol/L) to optimize both thermal stability and long-term cycling performance, resolving the contradiction between heat resistance and durability
Solution Approach 2:
The patent uses a composite electrolyte system combining two different lactone compounds (γ-butyrolactone and γ-valerolactone) with a lithium salt, where each component contributes different properties: γ-butyrolactone provides heat resistance while γ-valerolactone reduces gas generation and improves cycling stability, achieving both requirements simultaneously
2Reliability
If the entire surface functional group amount D of activated carbon is reduced to 0.152 meq/g/nm² or less, then the influence of surface functional groups on the electrolyte is reduced and durability is enhanced, but the manufacturing precision requirement increases
Solution Approach 1:
The patent establishes a precise quantitative parameter (D ≤ 0.152 meq/g/nm²) for surface functional group density, combining both the total functional group amount F and pore area S into a single controlling metric that simplifies the manufacturing control process while ensuring durability
Solution Approach 2:
The patent specifies the surface functional group amount D as a predetermined parameter that must be controlled during the activated carbon preparation stage, allowing manufacturers to select or treat activated carbon to meet this specification before assembly, thereby ensuring durability without requiring complex in-process adjustments
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 exhibits reduced direct current resistance (DCR) changes after a load test, indicating improved stability and prolonged service life, suitable for use in harsh environments such as electric vehicles.
Implementation Method 1
An electric double layer capacitor makes use of a storage function of an electric double-layer formed on an interface between a polarized electrode and an electrolyte
Implementation Method 2
The pair of polarized electrodes is impregnated with the electrolyte
Data Source
AI summary
A capacitor includes a capacitor element and an electrolyte containing a lactone compound. At least one of a positive electrode and a negative electrode of the capacitor element contains activated carbon Entire surface functional group amount D (meq/g/nm2) in an average sectional area of pores of the activated carbon is calculated at 0.152 or less by the following equation:D=F/S where F represents an entire surface functional group amount per unit weight (meq/g) of the activated carbon,and S represents an area (nm2) of a circle of which diameter is an average diameter of the pores of the activated carbon.