Search results

(1 - 2 of 2)
DESIGN, SYNTHESIS AND CHARACTERIZATION OF NOVEL MATERIALS TO CONSTRUCT HIGH-ENERGY-DENSITY RECHARGEABLE CELLS
Title
DESIGN, SYNTHESIS AND CHARACTERIZATION OF NOVEL MATERIALS TO CONSTRUCT HIGH-ENERGY-DENSITY RECHARGEABLE CELLS
Creator
Yue, Zheng
Date
2018
Description
ABSTRACTRechargeable electrical energy storage cells, especially lithium-ion cells, are the critical technology that realized the great...
Show moreABSTRACTRechargeable electrical energy storage cells, especially lithium-ion cells, are the critical technology that realized the great development of the portable electronic devices, such as laptop computers and cell phones. But in some other areas, such as the renewable energy industries and electrical vehicles, which are developing fast and more and more important for environment protection, the current rechargeable energy storage cells cannot meet their requirements, because of their limited energy density.Two types of cells, lithium sulfur batteries (LSBs) and supercapacitors, are attracting peoples’ attention for their potential to be developed as the future high-energy-density rechargeable cells. However, Li-S batteries are suffering from the fast discharging capacity fading, which is still a barrier for the large-scale commercialization. Although supercapacitors have been widely used in various areas, their energy density is much lower than current lithium-ion batteries, which limited their application only in assistant systems, such as regenerative brakes.To solve these problems, novel design for both the electrode material and electrolytes are required. In this thesis work, we focused our study in four areas: (1) New electrolytes for LSBs; (2) Cathode material for LSBs; (3) Activated carbon electrodes for electrical double layer capacitors (EDLCs); and (4) Electrolyte formulations for EDLCs. We investigated three types of new compounds as a co-solvent for the electrolyte of LSBs: fluorinated ethers, fluoroether sulfones and sulfonium ILs, which have improved the discharging capacity and cycling stability of LSBs. A novel S@HCN@MnO2 cathode material was designed and synthesized, which performed excellent long-term performance. A novel porous AC material with very high SSA was synthesized, and EDLCs with new electrolyte formulations were tested, which showed wide electrochemical potential window and high energy density.
Show less
HIGH SURFACE AREA CARBONS FOR ENERGY STORAGE TECHNOLOGIES
Title
HIGH SURFACE AREA CARBONS FOR ENERGY STORAGE TECHNOLOGIES
Creator
Lee, Youngjin
Date
2021
Description
Energy storage systems play a pivotal role in harvesting energy from various sources and converting it to the energy forms required for...
Show moreEnergy storage systems play a pivotal role in harvesting energy from various sources and converting it to the energy forms required for applications in several sectors, such as utility, industry, building and transportation. The outstanding growth of portable electronic devices and electric vehicle/hybrid electric vehicles (EVs/HEVs) has promoted the urgent and increasing demand for high‐power energy resources. The most common electrical energy‐storage device is the battery due to the large amount of energy stored in a relatively small volume and weight while providing suitable levels of power for many applications and requirements of everyday life. These days, lithium-sulfur batteries (LSBs) have been drawing attention with their potential to provide 3-5 times more energy than that of current lithium-ion batteries (LIBs) at lower cost. Thus, realization of a practical Li-S technology can move the U.S. rapidly toward a more sustainable transportation future. The electrochemical double-layer capacitor (EDLC) is also an emerging technology, which really plays a key part in fulfilling the demands of electronic devices and systems, for present and future. The EDLC technology strongly depends on the properties of electrode materials. Activated carbons play an important role in developing new electrodes for both LSB and supercapacitor technologies. For example, carbon electrode-based supercapacitors require very high specific surface area and superior pore size distribution for easy accessibility of ions. Thus, the primary objective of this study is to develop a new high surface area carbon material and assess its applicability for both LSB and supercapacitor technologies. In this thesis work, we have designed and synthesized several active carbon materials. One of them displayed very high surface area (1,832 m2/g) and excellent pore diameter (3.6 nm). We investigated the applicability of this carbon material for supercapacitor electrodes. We have also modified this carbon material with a nickel-rich phosphide in order to make it suitable for LSB cathode applications.
Show less