DOI

https://doi.org/10.25772/CQ56-ET57

Author ORCID Identifier

0000-0001-6626-3012

Defense Date

2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Hani M. El-Kaderi

Abstract

Synthesis and Application of Redox-Active Covalent Organic Frameworks in Rechargeable Batteries

Mohammad K. Shehab

Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States

Abstract

In recent years, lithium-ion batteries (LIBs) have been considered the dominant energy storage devices for portable electronics and electric vehicles due to their high energy density, low self-discharge rate, and long cycle life. In LIBs, the traditional positive electrodes employed are mainly derived from metal-containing inorganic compounds composed of cobalt, iron, nickel, or manganese (LiCoO2, LiMn2O4, and LiFePO4) coupled with graphite as the negative electrode. Despite the outstanding performance of LIBs, their manufacturing runs short in sustainability due to the toxicity of the metal oxides used. To solve the sustainability issues associated with lithium and metal-containing inorganic compounds in LIBs, the overarching goal of our research is to synthesize and develop green, efficient, inexpensive, and durable cathodes derived from redox-active covalent organic frameworks (COFs), a class of crystalline porous organic polymers, for use in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (LSBs), and supercapacitors. Our approach has the potential to make batteries more sustainable and less toxic. In addition to suitability and toxicity, the ability of the COFs’ design to control the pore shape and size allows for the use of naturally abundant and cost-effective metals with comparable electrochemistry to lithium, such as sodium, potassium, and aluminum, which is essential to solving the scarcity problem of lithium. Our studies indicate that the ability to tailor COFs at the molecular level endows the battery with high power density, high specific capacity, and great gravimetric capacity because of the dense redox-active sites in the skeleton of COFs and the low molecular weight of the organic repeating units. We have successfully synthesized crystalline, porous Aza-COF, polyimide-based COF, and benzimidazole-linked polymers and investigated their potential in SIBs. Their crystallinity, porosity, and conductivity helped a rapid surface-controlled Faradic process, facile sodium ions diffusion into the bulk electrode, and the accessibility of abundant redox-active sites. Therefore, the aforementioned COFs showed outstanding electrochemical performance as electrode materials in LIB and SIBs, and supercapacitors, making COFs a promising material for developing sustainable and efficient electrochemical energy storage devices.

Rights

© Mohammad K. Shehab

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-12-2023

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