Off-campus WSU users: To download campus access dissertations, please use the following link to log into our proxy server with your WSU access ID and password, then click the "Off-campus Download" button below.
Non-WSU users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Access Type
WSU Access
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Mechanical Engineering
First Advisor
Md Mahbubul Islam
Abstract
The widespread integration of Lithium-ion (Li-ion) batteries into grid systems underscores the critical need for further reductions in energy storage costs, particularly to support renewable energy sources such as wind and solar power. However, the limitations of current Li-ion technology, notably resource constraints, particularly concerning metals like lithium (Li) and cobalt (Co), are increasingly evident. With the escalating demand for lower costs and higher energy density, alongside growing concerns regarding natural resource depletion, research into "beyond Li-ion" technologies has garnered significant attention. Metal-sulfur (M-S) batteries are emerging as promising successors to Li-ion batteries due to their superior energy density, specific capacity, cost-effectiveness of S, and environmental friendliness. Among these, LiS batteries have demonstrated remarkable advancements in high capacity, rate capability, and extended cycle life, positioning them closer to market readiness. However, constraints related to the cost and availability of Li resources presently impede their suitability for large-scale applications. From sustainability and economic standpoints, sodium (Na) emerges as a superior choice over Li for pairing with S cathodes owing to their analogous chemical properties and significantly greater natural abundance.
Room temperature sodium-sulfur batteries (RT Na-S) hold promise as potential replacements forLi-ion batteries, yet their development faces significant hurdles, including issues such as poor reversible capacity, rapid capacity fade, and inadequate Coulombic efficiency. The limited accessible capacity stems from S's insulating nature and its sluggish reactivity with Na, resulting in incomplete reduction rather than complete Na2S formation. Moreover, the dissolution of polysulfides into the electrolyte during cycling, known as the "shuttle effect," stands as the primary cause behind rapid capacity degradation. Through meticulous investigation, our aim is to mitigate the shuttle effect and improve electrochemical reaction kinetics. Conventional methods of addressing the shuttle effect and enhancing performance in RT Na-S batteries, predominantly relying on physical and chemical adsorption, face challenges in overcoming poor reaction kinetics and limited capacity. Traditional materials tailored for Li-S batteries may not adequately meet the demands of RT Na-S batteries due to heightened shuttle effects and sluggish reaction kinetics. Consequently, there is a pressing need for innovative approaches to overcome these obstacles.
Employing electrocatalytic concepts presents a promising strategy for addressing these challengesin RT Na-S batteries. By utilizing electrocatalytic materials, we not only reduce the energy barrier of electrochemical reactions but also serve as an anchor for polysulfides, thus containing them to the cathode and minimizing their shuttle effect. In this study, we conducted fundamental mechanistic investigations into the S-electrocatalyst interface to develop an optimized catalytic cathode. We explored polysulfide adsorption and S electrochemical reaction kinetics on various electrocatalytic surfaces, including VS2, single transition metal (TM) atom-doped graphene, and MoS2, focused on understanding the effectiveness of these surfaces in influencing the S reaction kinetics during both discharging and charging processes. We calculate the adsorption energies of solid/liquid polysulfide species onto substrates. This investigation includes a comparative assessment of energetics against commonly employed electrolyte solvents like 1,3- dioxolane (DOL) and 1,2-dimethoxyethane (DME), elucidating the efficacy of our studied cathode electrocatalysts in mitigating the polysulfide shuttle phenomenon. Furthermore, we explore the adsorption mechanisms of various TM-doped substrates, employing d-band theory, and Bader charge analysis. The electronic structure evolution of our studied cathode electrocatalysts, both pre- and post-reaction with Na2Sn, is comprehensively analyzed through density of states (DOS). To address kinetic challenges associated with polysulfide conversion during discharge, we conduct Gibbs free energy analyses for the studied electrocatalysts. This endeavor seeks to elucidate the role of catalysts in enhancing reaction kinetics and facilitating Na2S deposition on cathode surfaces. Moreover, a detailed examination of charging behavior in RT Na-S batteries utilizing our studied electrocatalysts is conducted through nudged elastic band analysis. This endeavor aims to unravel the significance of chosen electrocatalysts in modulating the activation barrier of Na2S decomposition, crucial for facilitating rapid charging phenomena in Na-S batteries. Overall, our study significantly advances the understanding of tailoring polysulfide chemistry at electrocatalyst interfaces, thereby representing a pivotal step towards the systematic design of cathode materials tailored for Na-S batteries. Furthermore, our findings underscore the efficacy of enhancing active sites through the strategic engineering of TMDs and graphene surfaces, offering valuable insights into the precise modulation of electrochemical reactions involving polysulfides. Additionally, this research is poised to catalyze further computational and experimental explorations into a diverse array of 2D anchoring materials, thereby fostering the progressive development of cathodes tailored for Na-S batteries, characterized by diminished reversible capacity loss and improved performance metrics
Recommended Citation
Jayan, Rahul, "First-Principles Investigation Of Interfacial Chemistries In Room Temperature Sodium-Sulfur Batteries" (2024). Wayne State University Dissertations. 4040.
https://digitalcommons.wayne.edu/oa_dissertations/4040
