Activated Carbon Pore Distribution for High-Density Capacitor Electrodes
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Solution Overview
Problem
Existing activated carbons used in electrochemical devices face challenges in achieving high capacitance per volume and durability due to imbalances in pore distribution, specific surface area, and average pore size, leading to reduced bulk density and increased internal resistance.
Innovation Solution
A carbonaceous material with a BET specific surface area of 1,500 to 1,900 m²/g, average pore size of 1.84 to 2.05 nm, and a controlled pore distribution, with 65 to 90% of pores ≤3 nm and 10 to 20% of pores between 1 to 2 nm, optimized through a production method involving carbonization, primary and secondary activation with water vapor, and washing, to enhance capacitance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If activated carbon with high pore volume ratio of mesopores (20Å or larger) is used, then the specific surface area and pore volume are improved, but the bulk density of the electrode is reduced and capacitance per volume decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pore size distribution within specific ranges (micro pores: 0.3-1.5 nm, meso pores: 1.5-3 nm) and adjusting the pore volume ratios (micro pores: 40-70%, meso pores: 30-60%) to optimize both capacitance and bulk density, resolving the contradiction between pore volume and bulk density
Solution Approach 2:
The patent applies local quality by creating different pore size zones within the activated carbon structure, with specific micropores (0.3-1.5 nm) for high capacitance and specific mesopores (1.5-3 nm) for ion transport, where each pore size range serves a localized function to simultaneously improve capacitance per volume and maintain bulk density
2Quantity of substance
If activated carbon with relatively large pore size is used, then the pore volume is improved, but the bulk density of the electrode is reduced and initial capacitance per volume decreases
Solution Approach 1:
The patent applies parameter changes by setting specific pore size ranges (micro pores: 0.3-1.5 nm, meso pores: 1.5-3 nm) and controlling the average pore size within 1.0-2.0 nm, which optimizes the balance between pore volume and initial capacitance per volume, preventing the deterioration caused by excessively large pores
3Area of stationary object
If activated carbon with excessively high pore volume ratio of micropores is used, then the specific surface area is improved, but the durability and internal resistance are worsened
Solution Approach 1:
The patent applies parameter changes by controlling the micropore volume ratio to 40-70% (not excessively high) and setting the micropore size range to 0.3-1.5 nm, which maintains high specific surface area while preventing excessive internal resistance and durability issues, achieving a balanced pore distribution
Solution Approach 2:
The patent applies local quality by creating a hierarchical pore structure where micropores (0.3-1.5 nm) provide high specific surface area for capacitance while mesopores (1.5-3 nm) provide ion transport pathways, with each pore type serving its local function to simultaneously improve specific surface area and durability
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 improves capacitance per volume and durability by reducing internal resistance and maintaining electrode density, suitable for high-performance electric double-layer capacitors and lithium ion capacitors.
Implementation Method 1
secondary activation with water vapor
Implementation Method 2
utilize the capacity (electric double-layer capacitance) obtained solely from physical adsorption and desorption of ions
Data Source
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AI summary
An object of the present invention is to provide: a carbonaceous material which has a high capacitance per volume as well as a high durability; and a method of producing the same. The present invention relates to a carbonaceous material, wherein a BET specific surface area is 1,500 to 1,900 m2/g, an average pore size is 1.84 to 2.05 nm at a nitrogen relative pressure P/Po of 0.93 in a nitrogen adsorption isotherm measured at a temperature of 77.4 K, a ratio of a volume of pores having a pore size of 3 nm or smaller, which volume is determined by the BJH method, is 65 to 90% with respect to a total pore volume calculated based on a nitrogen adsorption amount at a relative pressure P/P0 of 0.93 in the nitrogen adsorption isotherm, and a ratio of a volume of pores having a pore size of 1 to 2 nm, which volume is determined by the MP method, is 10 to 20% with respect to the total pore volume calculated based on the nitrogen adsorption amount at a relative pressure P/P0 of 0.93 in the nitrogen adsorption isotherm.