Humic Acid Graphene Supercapacitor Electrodes
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Solution Overview
Problem
Current supercapacitors face challenges with low volumetric capacitances and energy densities due to limitations in electrode thickness, active material mass loading, and the tendency of graphene sheets to re-stack, leading to reduced specific surface areas and tap densities.
Innovation Solution
A supercapacitor electrode comprising a mixture of graphene sheets and humic acid, with humic acid occupying 0.1% to 99% by weight, and graphene sheets selected from pristine or non-pristine materials, achieving high specific surface areas and preventing graphene re-stacking, allowing for thicker electrodes with higher active material mass loading and tap densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphene sheets are used as electrode material to increase specific surface area, then capacitance density is improved, but graphene sheets tend to re-stack which reduces specific surface area and tap density
Solution Approach 1:
Humic acid acts as an intermediary substance between graphene sheets, preventing them from re-stacking while maintaining electrical conductivity. The humic acid molecules fill the spaces between graphene sheets and provide conductive pathways, thus preserving the high specific surface area needed for capacitance while preventing structural degradation.
Solution Approach 2:
The patent creates a composite material system combining graphene sheets with humic acid. This composite structure leverages the high surface area of graphene while using humic acid to maintain sheet separation and provide additional conductive networks, thereby achieving both high capacitance and structural stability.
2Volume of stationary object
If electrode thickness is increased to improve volumetric energy density, then energy storage capacity is improved, but mass loading and tap density are limited by material constraints
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrode material system by introducing humic acid, which enables increased electrode thickness without compromising mass loading density. The humic acid provides structural support and conductivity that allows thicker electrodes to maintain high active material content and tap density throughout the increased volume.
3Device complexity
If conventional supercapacitor structures are used to maintain simplicity, then device complexity is low, but volumetric capacitance and energy density remain limited
Solution Approach 1:
The patent utilizes the porous structure formed by the humic acid-graphene composite to achieve high volumetric capacitance. The porous architecture provides extensive surface area for charge storage while maintaining a compact structure that fits within conventional device form factors, thereby increasing volumetric capacitance without significantly increasing device complexity.
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 solution enables the formation of supercapacitors with significantly higher active material mass loading, tap density, and volumetric energy density, overcoming the limitations of conventional supercapacitors by preventing graphene sheet re-stacking and optimizing electrode structure.
Implementation Method 1
preventing graphene sheet re-stacking
Implementation Method 2
storing energy in the diffuse double layer. This double layer, created naturally at a solid-electrolyte interface when voltage is imposed
Implementation Method 3
This surface area must be accessible by electrolyte and the resulting interfacial zones must be sufficiently large to accommodate the so-called electric double-layer charges
Data Source
AI summary
A supercapacitor electrode comprises a mixture of graphene sheets and humic acid. The humic acid occupies 0.1% to 99% by weight of the mixture and the graphene sheets are selected from a pristine graphene material having essentially zero % of non-carbon elements, or a non-pristine graphene material having 0.001% to 5% by weight of non-carbon elements. The non-pristine graphene is selected from graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, or a combination thereof. The mixture has a specific surface area greater than 500 m2/g.