Raw-Material Carbon Composition for Electric Double-Layer Capacitor Electrodes
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Solution Overview
Problem
Existing carbon materials for electric double-layer capacitors, such as those derived from petroleum coke or coal pitch coke, fail to achieve sufficient capacitance per unit volume and high performance, with issues related to excessive carbonization, insufficient specific surface area, and increased internal resistance.
Innovation Solution
A raw-material carbon composition with controlled microstrength and volatile content, activated using an alkali metal compound, specifically sodium hydroxide, to produce a carbon material with a high specific surface area and optimal pore structure, enhancing capacitance and reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If activated carbon is produced by activating hard-graphitization carbon with gas or chemical agent to increase specific surface area, then capacitance per unit mass increases, but bulk density decreases and capacitance per unit volume does not increase proportionally
Solution Approach 1:
The invention changes the raw material parameter from hard-graphitization carbon to easy-graphitization carbon, which has different physical and chemical properties. This parameter change allows the carbon to form a denser structure upon activation while still achieving high specific surface area, thereby resolving the contradiction between surface area and bulk density
Solution Approach 2:
The invention uses a composite approach by combining easy-graphitization carbon with specific pore-forming agents and controlling the activation process to create a composite structure that maintains high density while providing sufficient surface area for capacitance
2Quantity of substance
If activated carbon is produced from hard-graphitization carbon, then specific surface area can be increased, but electric conductivity decreases and internal resistance increases
Solution Approach 1:
The invention changes the fundamental parameter of the carbon material from hard-graphitization to easy-graphitization type. Easy-graphitization carbon inherently possesses better electrical conductivity due to its molecular structure, and this property is preserved during the activation process while still achieving the required surface area
3Volume of stationary object
If mesophase pitch and mesophase pitch carbon fiber are used to produce activated carbon, then bulk density and electrical conductivity improve, but manufacturing cost increases due to expensive materials and complicated infusibilizing/carbonizing process
Solution Approach 1:
The invention replaces expensive mesophase pitch and mesophase pitch carbon fiber with cheaper easy-graphitization carbon materials such as petroleum coke or coal-tar pitch coke. This substitution significantly reduces raw material cost while still achieving the desired bulk density and electrical conductivity properties in the final activated carbon product
Solution Approach 2:
The invention extracts and eliminates the infusibilizing/carbonizing process step from the manufacturing sequence. By using easy-graphitization carbon that can be directly activated without prior infusibilizing treatment, the process is simplified and manufacturing cost is reduced while maintaining product quality
4Quantity of substance
If petroleum coke or coal pitch coke is carbonized to satisfy volatile content and H/C atom ratio conditions, then activation can be performed, but capacitance per unit volume remains insufficient
Solution Approach 1:
The invention optimizes the carbonization parameters specifically for easy-graphitization carbon, controlling temperature, time, and atmosphere to achieve the ideal balance between specific surface area and bulk density. This parameter optimization ensures that the activated carbon achieves both high surface area and high density, resolving the contradiction in capacitance per unit 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 approach results in an electric double-layer capacitor with increased capacitance per volume and reduced internal resistance, meeting the requirement for high-performance capacitors with capacitance exceeding 30 F/cc.
Implementation Method 1
fine pores are formed from the surface of a particle by an oxidative reaction
Implementation Method 2
obtained by carbonizing petroleum coke and coal-tar pitch coke
Data Source
AI summary
The capacitance per volume of an electric double-layer capacitor can be increased by using a raw-material carbon composition for use in a carbon material for an electrode of the electric double-layer capacitor by applying an activation process, characterized in that the raw-material carbon composition has a volatile content of 1.3% by mass to 15% by mass (both inclusive), and microstrength of 5 to 30% when the volatile content is less than 6% by mass while microstrength of 5 to 20% when the volatile content is 6% or more.