- Title
- Low-temperature catalytic graphitization of amorphous carbon as a renewable carbon material
- Creator
- Khoshk Rish, Salman
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- For the development of advanced high-performance lithium-ion batteries, the demand for anode materials with high capacity and excellent performance is increasing. Various anode materials have been proposed in the past few years. However, a special focus has been concentrated on the development of graphene-like materials. These materials possess excellent properties such as high electrical conductivity, high thermal conductivity, excellent mechanical strength, and large surface area. Conventional 2D graphene suffers from aggregation due to the presence of van der Waals forces, rendering the effectiveness of graphene. 3D structured graphene-like materials are believed to retain graphene’s unique properties when deployed in various applications. This study aims at an in-depth understanding of the conversion of amorphous carbon into 3D multilayer graphene nanostructures through microwave catalytic graphitization-liquid oxidation-thermal reduction in bulk quantities, with the ultimate goal of applying the resultant material as anode materials for lithium-ion batteries and understanding the conversion process. Coconut-shell-derived activated carbon was used to as the starting material. The graphitization experiments were carried out under various experimental conditions. The methodology, sample preparation process, experimental procedure, and analytical techniques used in this study are described in detail in Chapter 2. The degree of graphitization in various graphitized samples was measured using the Rietveld refinement method. The impact of various parameters on the degree of graphitization and crystalline structure was investigated using X-ray diffraction analysis and Raman spectroscopy. The changes in the physical structure of the graphitized samples were studied using N2 adsorption-desorption analysis and the Brunner-Emmet-Teller method was used to calculate the surface area. The activated carbon with the greatest number of multilayer graphene nanostructures (higher degree of graphitization) was chosen for the subsequent liquid oxidation to segregate the graphene-like nanostructures. Ultimately, the final product was applied anode material in a half cell lithium-ion battery. The impact of microwave catalytic graphitization on the crystalline structure and physical structure of graphitized activated carbon was systematically investigated. The results showed that higher temperature, longer holding time, higher catalyst, and catalyst precursors with high dispersion (Ni(NO3)2 and Ni(CH3CO2)2) resulted in a higher degree of graphitization and well-developed crystalline structure. The highest degree of graphitization (~94%) was achieved at 1400 °C and 30 min with 20 wt.% Ni [Ni(NO3)2] loading. The findings of this study also showed that the catalytic graphitization process was accompanied by the elimination of micropores and the formation of mesopores, leading to a decrease in surface area as the degree of graphitization increased. This study found that Ni nanoparticles were mobile throughout the activated carbon matrix during the graphitization process, graphitizing more amorphous structures. This mobility was not observed when conventional heating was used. The in-situ studies suggested the presence of two graphitization formation mechanisms, i.e., (1) catalyst-induced graphitization during the heating stage and (2) dissolution-precipitation mechanism during the cooling stage. The On/Off or pulsive heating nature of microwave enhanced the dissolution and precipitation cycles by causing temperature fluctuation at the nano particle level, which allowed for the graphitization of amorphous carbon in a relatively more efficient process. The catalytically graphitized activated carbon was then used to synthesize nanostructured few-layered graphene and the impact of various graphitization catalysts (Fe, Ni, and Co) on the characteristics of the resultant 3D multilayer graphene nano structures was studied. The different graphitization catalysts resulted in a graphitized activated carbon with different structures, which led to the formation of 3D graphene-like few-layered structures with different thicknesses. The results showed that when Co was used as the graphitization catalyst, the thickness of graphene-like materials was in the range of 1.5-2 nm as opposed to Fe and Ni yielded a similar thickness of 4-6 nm. The difference in the structure led to varying lithium storage performances. In the Co, the sample outperformed the other catalyst and was able to deliver an ultrahigh capacity of 1695 mAh/g at 0.1 A/g with a capacity retention of ~180%. Also, the sample synthesized via Co had a superior rate performance; It delivered 357 mAh/g at 5 A/g with 94% capacity retention after 1000 cycles.
- Subject
- microwave catalytic graphitization; in situ studies; multilayer graphene nanostructures; advanced anode materials; ultrahigh specific capacity
- Identifier
- http://hdl.handle.net/1959.13/1512510
- Identifier
- uon:56626
- Rights
- Copyright 2022 Salman Khoshk Rish
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 14 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 454 KB | Adobe Acrobat PDF | View Details Download |