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Synthesis of carbon-based nanomaterials and composites toward energy storage applications

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Abstract
In this dissertation work, we mainly study the carbon-based nanomaterials and
composites for energy storage applications, like anode materials for Li-ion materials
and electrode materials for supercapacitors.
Urchin-like MnO2/carbon nanofiber composites was prepared for anode
materials of Li-ion battery, The carbon nanofibers (CNFs) are uniformly deposited on
u-MnO2 to improve the electrical conductivity and to utilize the hierarchical
architecture of u-MnO2. As the anode electrode of Li-ion batteries, the u-MnO2/CNFs
nanocomposites exhibit an comparable cycle performance of 988 mAh·g−1 after 100
cycles with a good rate capability. The superior electrochemical performances of the
u-MnO2/CNFs nanocomposites can be attributed to the hierarchical urchin-like
structures and the superior electrical conductivity of the nanocomposites, which can
facilitate fast electron and ion transport and accommodate a large volume change
during charge/discharge.
Then obtained q-MC//CC composite is employed as a binder-free electrode of
supercapacitor. The g-C3N4 quantum dots could effectively enhance the interface
electrical conductivity and ion transportation of MnCO3 electrode, which results in
superior electrochemical performances. The q-MC//CC electrode delivers a high
specific capacity of 1001 F·g-1 at a current density of 1 A·g-1 and a good cycling
stability of 96% capacity retention after 5000 cycles. Moreover, asymmetric flexible
supercapacitor (ASC) are assembled with q-MC//CC as a positive electrode and
carbon cloth as a negative electrode, which exhibits a high energy density of 27.1
Wh·kg-1 at a power density of 500 W·kg-1. Also, the fabricated ASC device
demonstrates to power the light-emitting diode effectively under mechanical bending.
Also, as electrode materials of supercapacitors, GH-CN (graphene
hydrogel-g-C3N4 quantum dots) composites were prepared by hydrothermal method.
The results demonstrated that the addition of g-C3N4 QDs into graphene hydrogel
improved the electrochemical performance distinctly, because the nitrogen-riched
quantum dots embedded in graphene hydrogel which has high theoretically surface
area, the quantum dots can provide more active sites for faradic reactions, then promote ion diffusion\transport capability at the electrode/electrolyte interface and
enhance the faradic reaction and electron transfer, leading to the observed increased
capacitance. The symmetric supercapacitor (SSC) was assembled using GH-2.5CN as
positive electrode and negative electrode. The assembled SSC exhibited a high energy
density of 22.5 Wh kg-1 at 250 W kg-1, and illuminated a red light-emitting diode
(LED). It also exhibited excellent flexibility and reached 83.3% capacitance retention
after 15000 cycles at 5 A g-1. These results demonstrate the potential GH-CN as a
next-generation electrode material for energy storage system.
The novel hierarchical N-GQDs/MnCO3/ZnMn2O4 (N/MC/ZM) composite was
grown directly on Ni foam by simple hydrothermal method followed by calcinations
treatment for applications as high rate electrodes in supercapacitors. The N/MC/ZM
composites exhibited excellent electrochemical properties, including a high specific
capacitance of 960.6 F g-1, as well as better cycling stability than MC/ZM (450.3 F g-1).
The homogenously dispersed N-GQDs can increase the conductivity and activity sites.
Results clearly indicate that the combination of N-GQDs and MC/ZM can constitute a
promising binary metal-based electrode material with superior supercapacitive
performance, which can provide an alternative to design the quantum dots decorated
novel binary metal compounds materials with sample methods for a wide variety of
energy storage devices such as supercapacitors, batteries.
Author(s)
류적
Issued Date
2021
Awarded Date
2021-08
Type
Dissertation
Keyword
Carbon-based materialscompositesenergy storage
URI
https://oak.ulsan.ac.kr/handle/2021.oak/6007
http://ulsan.dcollection.net/common/orgView/200000501160
Alternative Author(s)
LIU DI
Affiliation
울산대학교
Department
일반대학원 화학공학전공
Advisor
Won Mook Choi
Degree
Doctor
Publisher
울산대학교 일반대학원 화학공학전공
Language
eng
Rights
울산대학교 논문은 저작권에 의해 보호받습니다.
Appears in Collections:
Chemical Engineering > 2. Theses (Ph.D)
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