Activated Carbon Pore Structure for High-Density Electrodes
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Solution Overview
Problem
Existing electrochemical devices, such as electric double-layer capacitors and lithium ion capacitors, face challenges in achieving high capacitance per volume and durability due to excessive mesopore distribution, large pore size, and high internal resistance, which affect their performance and longevity under stringent service conditions.
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 pore distribution ratio of 65 to 90% for pores ≤3 nm and 10 to 20% for pores 1 to 2 nm, optimized through carbonization, primary activation with water vapor, washing, and secondary activation, is developed to enhance capacitance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pore volume ratio of mesopores is increased to improve ion accessibility, then the initial capacitance per volume is improved, but the bulk density of the electrode is reduced
Solution Approach 1:
The patent optimizes the pore size distribution by controlling the volume ratio of micropores (0.5-2 nm) to be 20-80% and mesopores (2-50 nm) to be 20-80% of total pore volume, with specific target ranges for average pore size (1.5-3.0 nm). This parameter optimization balances ion accessibility and electrode density, resolving the contradiction between capacitance per volume and bulk density.
2Quantity of substance
If the pore size is increased to improve ion transport, then the initial capacitance per volume is improved, but the bulk density of the electrode is reduced
Solution Approach 1:
The patent creates different pore size zones within the activated carbon structure, with micropores (0.5-2 nm) providing high surface area for capacitance and mesopores (2-50 nm) providing transport channels. This local differentiation of pore qualities allows simultaneous optimization of ion transport and electrode density.
Solution Approach 2:
The patent specifies optimal pore size parameters including average pore size of 1.5-3.0 nm, micropore volume ratio of 20-80%, and mesopore volume ratio of 20-80%. These parameter changes balance ion accessibility and electrode bulk density to maximize capacitance per volume.
3Area of stationary object
If the pore volume ratio of micropores is increased to improve surface area, then the specific surface area is improved, but the durability is reduced
Solution Approach 1:
The patent optimizes the micropore volume ratio to 20-80% of total pore volume with pore sizes of 0.5-2 nm, balancing surface area for capacitance with structural stability for durability. This parameter optimization prevents excessive micropore formation that would compromise electrode integrity under severe service conditions.
4Quantity of substance
If the specific surface area is increased to improve capacitance, then the capacitance per volume is improved, but the internal resistance is increased
Solution Approach 1:
The patent creates a hierarchical pore structure where micropores (0.5-2 nm) provide high surface area for capacitance and mesopores (2-50 nm) serve as transport channels for ion movement. This local functional differentiation reduces ion transport resistance while maintaining high specific surface area for capacitance.
Solution Approach 2:
The patent optimizes pore distribution parameters including micropore volume ratio (20-80%), mesopore volume ratio (20-80%), and average pore size (1.5-3.0 nm). These parameter changes ensure adequate ion accessibility to high surface area regions, reducing internal resistance while maintaining high capacitance per volume.
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 high capacitance per volume, and improves durability, making it suitable for high-performance electrochemical devices like electric double-layer capacitors and lithium ion capacitors.
Implementation Method 1
Electric double-layer capacitors, which are one type of electrochemical devices, utilize the capacity (electric double-layer capacitance) obtained solely from physical adsorption and desorption of ions
Data Source
AI summary
A carbonaceous material may have a high capacitance per volume as well as a high durability, and/or may have 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/P0 of 0.93 in a nitrogen adsorption isotherm measured at 77.4 K, a ratio of pore volume having a pore size of 3 nm or smaller, determined by the BJH method, is 65 to 90% relative to 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 pore volume having a pore size of 1 to 2 nm, determined by the MP method, is 10 to 20% relative to total pore volume calculated based on the nitrogen adsorption amount at a relative pressure P/P0 of 0.93 in the nitrogen adsorption isotherm.