Graphene-CNT Hybrid Electrode for Lithium-Ion Supercapacitors
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Solution Overview
Problem
Conventional supercapacitors and lithium ion capacitors have high power density but low energy density, short product life, and limited charging/discharging cycles, necessitating an improvement in energy storage performance.
Innovation Solution
A lithium-ion supercapacitor using a graphene/CNT composite electrode with a CNT concentration of 17 wt% to 33 wt% is developed, where CNTs are arranged between graphene layers to enhance conductivity and pore accessibility, increasing energy density and charging/discharging cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional supercapacitors or lithium ion capacitors are used, then power density is high, but energy density is low
Solution Approach 1:
The patent employs a composite electrode structure combining graphene and carbon nanotubes (CNTs). The graphene provides high surface area and capacitance for increased energy density, while the CNT network maintains electrical conductivity for high power density. This composite approach allows simultaneous optimization of both energy and power characteristics that are typically traded off against each other in conventional capacitors or batteries.
Solution Approach 2:
The patent creates a hierarchical structure where graphene sheets form the primary capacitance-storing matrix, while CNTs are strategically positioned at specific locations to maintain conductivity pathways and provide structural support. The CNT concentration is optimized at 17-33 wt% to ensure sufficient conductivity without compromising the high surface area of graphene that enables high energy density.
2Duration of action of stationary object
If conventional supercapacitors or lithium ion capacitors are used, then power density is high, but product life is short
Solution Approach 1:
The graphene-CNT composite structure provides enhanced mechanical strength and structural stability compared to pure graphene or conventional activated carbon electrodes. The CNT network acts as a robust scaffold that prevents electrode degradation during repeated charging/discharging cycles, thereby extending product life while maintaining high power density through the conductive CNT pathways.
Solution Approach 2:
Instead of using conventional porous materials like activated carbon that rely on random pore structures, the patent inverts the approach by using exfoliated graphene sheets with controlled interlayer spacing. This inverted structure provides more uniform ion transport pathways and reduces mechanical stress during cycling, leading to extended product life.
3Duration of action of moving object
If conventional supercapacitors or lithium ion capacitors are used, then power density is high, but charging/discharging cycles are limited
Solution Approach 1:
The graphene-CNT composite electrode combines the high surface area of graphene for capacitance with the excellent electrical conductivity and mechanical strength of CNTs. The CNT network maintains continuous conductive pathways even after extensive cycling, preventing electrode fragmentation and maintaining high power density over thousands of charging/discharging cycles.
Solution Approach 2:
The patent performs preliminary exfoliation and functionalization of graphene to create a stable, defect-minimized structure before assembly. This pre-treatment reduces structural weaknesses that would otherwise lead to degradation during cycling, thereby extending the charging/discharging cycle life while maintaining high power density.
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 lithium-ion supercapacitor achieves high energy and power density, extended charging/discharging cycles, and a longer product life, enabling efficient energy storage.
Implementation Method 1
the CNT having high electric conductivity improves conductivity in the thickness direction of the graphene
Implementation Method 2
the electric conductivity decreases due to the influence of restocking and a functional group according to a Van der waals force
Implementation Method 3
lithium ions eluted from LiCoO2 of the cathode 2 into the electrolytic solution 3 move between electrodes in the electrolytic solution 3
Implementation Method 4
According to an electric field, lithium ions eluted from LiCoO2 of the cathode 2 into the electrolytic solution 3 move between electrodes
Implementation Method 5
cations and anions disposed inside the electrolytic solution 6 are respectively moved to the surfaces of mutually-different electrodes
Implementation Method 6
are attached to the surfaces, and form an electric double layer on the surfaces of the electrodes
Implementation Method 7
many pores having a pore diameter of 2 nm or more and 50 nm or less are formed to be uniformly distributed, and electrolytic ions can easily access a graphene activation face
Data Source
Figure 1~2
Figure 3~4(b)
Figure 5(a)~6
AI summary
As an object to provide a lithium-ion supercapacitor having a high energy density and a high power density, capable of being charged and discharged many times, and having a long product life, there is provided a lithium-ion supercapacitor using a graphene/CNT composite electrode, the lithium-ion supercapacitor including: an anode; a cathode that is arranged to be separated from the anode; and a lithium ion electrolytic solution that fills in a space between the anode and the cathode, wherein either or both of the cathode and the anode are formed by a graphene/CNT composite, and a CNT concentration in the graphene/CNT composite is 17 wt% or more and 33 wt% or less.