Investigation of Sulfide Materials for Supercapacitors

Date

2024-1-26

Author

Uçar, Ali Deniz

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Supercapacitors are energy storage devices distinguished by their ability to rapidly store and release energy. The combination of low internal resistance, high power density, and extended cycle life renders them invaluable for a diverse array of applications, spanning from substantial endeavors like grid stabilization systems, electric vehicles, and regenerative braking to more compact uses, including wearable electronics and sensors. Supercapacitors hold a pivotal position in meeting the escalating need for efficient and sustainable energy solutions. Layer-structured transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) are one of the mostly investigated materials for energy storage applications. Titanium disulfide (TiS2) is one of the lightest member of TMDs. However, its susceptibility to oxidation restricts the use of TiS2 in aqueous environments. In the first part of the thesis, bulk TiS2 powders were synthesized from elemental titanium and sulfur powders. Two-dimensional (2D) TiS2 flakes, in semi-metallic 1T phase, were then fabricated from bulk TiS2 powders using organolithium chemistry. Mechanically flexible and self-standing TiS2 films were prepared through the incorporation of carbon nanotubes (CNTs) and used as supercapacitor electrodes. Oxidation resistance of the TiS2 electrodes were improved through dopamine-treatment. Electrodes yielded a Coulombic efficiency of 99% and capacity retention of 93% after 10 000 charge-discharge cycles in aqueous electrolytes. A power density of 2000 W.kg-1 was reported. Iron sulfide, a member of the metal sulfide family, holds promise as a superior material for supercapacitors owing to its outstanding electrical conductivity and remarkable electrochemical performance. Furthermore, the abundance of iron and sulfur, along with their cost-effectiveness, establishes iron sulfide as an economically viable choice for supercapacitor applications. In the second part of the thesis, asymmetric supercapacitors were fabricated with cobalt metal-organic framework (Co-MOF) positive and iron sulfide/graphene (FexSy/Graphene) negative electrodes. The fabrication of both electrodes involved depositing active materials onto commercially available carbon fabrics. The gel electrolyte was formulated using deionized water, potassium hydroxide (KOH), and hydroxyethyl cellulose (HEC). The fabricated asymmetric supercapacitors were encapsulated within polyvinyl chloride, achieving an areal capacitance of 111 mF.cm-2 at a scan rate of 10 mV.s-1. Fabricated supercapacitor was kept at room conditions and remained functional even after 5 days.

Subject Keywords

2D Materials, Supercapacitors, Energy storage, Transition metal dichalcogenides, Metal sulfides

URI

https://hdl.handle.net/11511/108775

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Graduate School of Natural and Applied Sciences, Thesis