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Access Type

WSU Access

Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical Engineering

First Advisor

Leela M. Arava

Abstract

Stabilizing polysulfide-shuttle process while ensuring high sulfur loading holds the key to realize high theoretical energy density (2500 Wh/kg) of lithium-sulfur (Li-S) batteries. Though several carbon based porous materials have been used as host structures for sulfur and its intermediate polysulfides, the week adsorption of polysulfides on carbon surface and its poor reaction kinetics limits them from practical application. Here, we preset a novel ‘electcatalysis’ approach to stabilize polysulfide shuttle process and also enhance its red-ox kinetics. As a proof of concept, we have studied in-detail using conventional electrocatalyst i.e Pt/graphene composite, further the same extended to cost-effective electrocatalysts such as WS2 nanosheets and Metal carbides for viable practical applications. Nature of electrocatalyst, concentration of polysulfides, temperature of the cell etc., on electrochemical properties will be discussed. We reveal substantial improvement in electrochemical properties such as specific capacity, rate capability, coulombic efficiency etc. and corroborate our findings with systematic experimental studies. Interaction between electrocatalyst and polysulfides has been evaluated by conducting X-ray photoelectron spectroscopy and electron microscopy studies at various electrochemical conditions. Thus, introducing a catalyst in the Li−S system will open a new avenue for improving electrochemical performance.

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