Activated Carbon Pore Structure for Durable Electric Double-Layer Capacitors
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Solution Overview
Problem
Existing carbonaceous materials for electric double-layer capacitors face challenges in achieving high durability and withstand voltage, particularly under severe conditions, due to limitations in BET specific surface area, average pore size, and pore distribution, which affect capacitance and internal resistance.
Innovation Solution
A carbonaceous material with a BET specific surface area of 1,900 to 2,500 m2/g, average pore size of 2.2 to 2.6 nm, and a specific pore volume distribution is developed, utilizing a plant-derived precursor like coconut shells, through a process involving carbonization, primary and secondary activation with water vapor, and careful washing to minimize impurities, resulting in enhanced micropore and mesopore development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If activated carbon with large pore size is used to improve durability, then durability is improved, but bulk density is reduced and capacitance per volume is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pore size distribution within the narrow range of 0.8-2.0 nm average pore size, and adjusting the BET specific surface area to 1500-3000 m²/g range. This optimization of physical parameters enables simultaneous improvement of durability and maintenance of bulk density, resolving the contradiction between durability and volume efficiency.
2Quantity of substance
If BET specific surface area is increased to improve capacitance, then capacitance is improved, but internal resistance increases
Solution Approach 1:
The patent applies local quality by creating a specific pore size distribution where micropores (0.5-2.0 nm) provide high surface area for capacitance while mesopores (2.0-50 nm) serve as transport channels for ion movement. This spatial differentiation of pore functions allows high capacitance from micropores while mesopores maintain low internal resistance by facilitating efficient ion transport.
3Quantity of substance
If pore volume is increased to improve capacitance per volume, then capacitance per volume is improved, but durability under severe conditions deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the total pore volume to 0.25-0.65 cm³/g within a controlled pore size distribution. This specific parameter range ensures sufficient pore volume for high capacitance per volume while maintaining pore sizes that provide mechanical stability and durability under severe operating conditions such as temperature variations and high voltage stress.
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 optimized carbonaceous material reduces internal resistance, maintains capacitance, and improves durability and withstand voltage, making it suitable for high-performance electric double-layer and lithium ion capacitors.
Implementation Method 1
Electric double-layer capacitors, which are one type of energy storage devices, utilize the capacity (electric double-layer capacity) obtained solely from physical adsorption and desorption of ions
Implementation Method 2
a process involving carbonization, primary and secondary activation with water vapor
Implementation Method 3
utilizing a plant-derived precursor like coconut shells, through a process involving carbonization
Data Source
AI summary
A carbonaceous material for electric double-layer capacitors that is based on a plant-derived carbon precursor, in which carbonaceous material: a BET specific surface area is 1,900 to 2,500 m2/g; an average pore size is 2.2 to 2.6 nm as determined by a nitrogen adsorption method; a volume of micropores having a pore size of 2 nm or smaller is 0.84 to 1.30 cm3/g as determined by the MP method; a ratio of a volume of micropores having a pore size of 1 to 2 nm with respect to the volume of the micropores having a pore size of 2 nm or smaller is 25 to 50% as determined by the MP method; and a volume of mesopores having a pore size of 2 to 50 nm is 0.16 to 0.4 cm3/g as determined by the BJH method; and a method of producing same.