Activated Carbon Purification for Supercapacitor Electrodes

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Solution Overview

Problem

Existing methods for producing activated carbon for supercapacitors are inadequate in removing corrosive ions and impurities, leading to leakage currents, capacity losses, and corrosion in aluminum electrodes, due to their limited effectiveness in purifying the material for sensitive applications.

Innovation Solution

A method involving a mixture of green coke, a base, and a chemically inert hydrophilic polymer, followed by pressing and oxidative activation, with a subsequent washing step using citric acid to produce activated carbon with high purity and specific properties suitable for supercapacitors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional washing methods (water, concentrated acids) are used to purify activated carbon, then some impurities are removed, but aggressive ions remain and the activated carbon becomes contaminated due to irreversible adsorption

Engineering Contradiction:

Improvepurity of activated carbonVSAvoidcorrosive ions and contamination

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical parameters of the washing solution by using citric acid at controlled concentrations (1-10% by weight) instead of conventional water or concentrated acids. This parameter change enables effective removal of corrosive ions (Cu²⁺, Fe³⁺, Cl⁻, NO₃⁻, SO₄²⁻, HCOO⁻, CH₃COO⁻) while preventing contamination of the activated carbon, achieving both high purity and absence of harmful factors

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Citric acid acts as an intermediary substance that mediates between the activated carbon and corrosive ions. It selectively chelates metal ions and removes aggressive anions through controlled chemical reactions, serving as a bridge that eliminates harmful impurities without introducing new contaminants that would adhere irreversibly to the carbon surface

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If activated carbon contains impurities from raw material or activation method, then production cost is reduced, but corrosive processes occur leading to leakage current and capacity losses

Engineering Contradiction:

Improveproduction simplicity and costVSAvoidcapacitor performance and stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary purification action by washing the activated carbon with citric acid solution immediately after activation. This preliminary treatment removes corrosive ions and impurities before the activated carbon is used in supercapacitor assembly, preventing subsequent corrosive processes, leakage currents, and capacity losses while maintaining production simplicity

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If aggressive ions are present in activated carbon, then manufacturing process is simpler, but aluminum foil corrosion occurs and activated carbon layer detaches

Engineering Contradiction:

Improvepurification process complexityVSAvoidadhesion of activated carbon layer to current collector

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The patent uses a disposable citric acid washing solution that is inexpensive and effective for removing aggressive ions. The washing solution is used once and then discarded, providing simple and effective ion removal without requiring complex reusable purification systems, thereby maintaining both process simplicity and preventing aluminum foil corrosion that would lead to detachment

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 method results in activated carbon with high specific and volumetric capacity, minimizing corrosion risks and enhancing energy storage density in double-layer capacitors, while maintaining cost-effectiveness and simplicity.

Implementation Method 1

washing the pellet with a citric acid solution, in particular a dilute citric acid solution

Methodology Applied

Scientific EffectChelation:

Implementation Method 2

washing the pellet with a solution of citric acid, particularly preferably dilute citric acid

Methodology Applied

Scientific EffectAcid washing:

Implementation Method 3

activating the compact produced in step b) pellets produced, and d) washing the pellet with a solution of citric acid

Methodology Applied

Scientific EffectOxidative chemical activation: Oxidation

Implementation Method 4

a hydrophilic polymer that is chemically inert to the base

Methodology Applied

Scientific EffectHydrophilicity: Hydrophile

Implementation Method 5

An essential functional principle of the supercapacitors is based on the electrical energy storage through charge separation

Methodology Applied

Scientific EffectCharge separation: Electrical Accumulator

Data Source

PatentEP2590897B1High-purity porous carbon for double-layered capacitors

Publication Date: 2017.10.04 CORNING INC

AI summary

The invention relates to the use of an activated carbon in electrodes for electrical double-layered capacitors, which can be obtained by a method comprising activating of a carbon-containing, green coke-based material, treating the carbon-containing material with an acid at a temperature between 30°C and 200°C, wherein the acid is citric acid, and removing the acid from the carbon-containing material.