3D Graphene Framework Electrode for Supercapacitor Ion Transport

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Solution Overview

Problem

Electrochemical capacitors (ECs) face challenges in achieving high energy density while maintaining power density and cycle life, with graphene electrodes experiencing reduced surface area and ion diffusion due to π-π interactions leading to unsatisfactory capacitances and low charging/discharging rates.

Innovation Solution

A three-dimensional (3D) graphene framework with a hierarchical porous structure is used as a binder-free electrode, providing high electrical conductivity, ion transport rate, and ion-accessible surface area, resulting in enhanced gravimetric and volumetric capacitances and energy densities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If graphene sheets are used as electrode material, then theoretical surface area and gravimetric capacitance are greatly improved, but π-π interactions cause re-stacking that decreases surface area and reduces ion diffusion rate

Engineering Contradiction:

Improvetheoretical surface areaVSAvoidion diffusion rate

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

The patent employs a three-dimensional porous graphene framework where controlled porosity prevents complete restacking of graphene sheets. The porous structure maintains high surface area while creating channels for ion diffusion, resolving the contradiction between maximizing surface area and enabling ion transport.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent transitions from two-dimensional graphene sheets to a three-dimensional framework structure. This dimensional change prevents planar restacking while maintaining high surface area, and introduces vertical pathways for ion diffusion that were absent in flat sheet configurations.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If highly porous electrode structure is used, then gravimetric capacitance is improved, but volumetric capacitance decreases due to low packing density

Engineering Contradiction:

Improvegravimetric capacitanceVSAvoidvolumetric capacitance

Core Design Contradiction:

Quantity of substanceVSVolume of stationary object

Solution Approach 1:

The patent optimizes the porosity parameter of the graphene framework, creating a balanced pore size distribution that allows sufficient ion access for high gravimetric capacitance while maintaining adequate packing density for high volumetric capacitance. The specific surface area is tuned to approximately 1000 m²/g, which balances both metrics.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite three-dimensional framework combining graphene sheets with spacer materials or functional groups that prevent complete collapse while maintaining porosity. This composite approach achieves both high surface area utilization and high packing density simultaneously.

Inventive Principle:

Principle #40Composite materials

3Volume of stationary object

If more compact electrode structure is used, then volumetric capacitance is improved, but ion-accessible surface area and ion diffusion rate decrease

Engineering Contradiction:

Improvevolumetric capacitanceVSAvoidion-accessible surface area

Core Design Contradiction:

Volume of stationary objectVSQuantity of substance

Solution Approach 1:

The patent introduces a hierarchical porous structure with multiple pore size levels. Macro-pores provide ion transport pathways in compact regions, while micro-pores provide high surface area for capacitance. This porous design allows compact packaging without sacrificing ion accessibility.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent segments the electrode into multiple functional zones with different porosity levels. Outer regions have higher porosity for ion access, while inner regions are more compact for high density. This segmentation allows simultaneous optimization of both volumetric capacitance and ion-accessible surface area.

Inventive Principle:

Principle #1Segmentation

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 3D graphene framework achieves gravimetric and volumetric capacitances of up to 440 F/g and 360 F/cm³, respectively, and energy densities comparable to lead acid batteries, bridging the gap between ECs and batteries for diverse applications.

Implementation Method 1

Graphene has recently been investigated as an EC electrode material because of its high intrinsic electrical conductivity

Methodology Applied

Scientific EffectElectrical conductivity: Conduction (electrical)

Implementation Method 2

mechanically compressed graphene frameworks... high ion transport rate and ion-accessible surface area

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Implementation Method 3

gravimetric capacitance of about 550 F g−1... deliver a gravimetric capacitance of about 298 F g−1

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10692660B2Three-dimensional graphene framework-based high-performance supercapacitors

Publication Date: 2020.06.23 RGT UNIV OF CALIFORNIA

AI summary

An electrochemical capacitor includes a pair of electrodes and an electrolyte disposed between the pair of electrodes. At least a first electrode of the pair of electrodes includes a graphene framework film, and the graphene framework film includes interconnected graphene sheets with nanopores formed in the graphene sheets.