PhD Thesis Defense: Chuanlong Wang

For info on how to attend this videoconference, please email chuanlong.wang.TH@dartmouth.edu

"Advanced Materials Design and Synthesis for Sodium-Sulfur Batteries"

Abstract

Combining two abundant element resources of sodium (Na) and sulfur (S), Na-S electrochemistry is a promising cost-effective system beyond the current lithium (Li)-ion technologies. The Na-S batteries can deliver a theoretical specific energy of ~1250 Wh Kg^-1 at room-temperature (RT), which is more than 3 times higher compared to that of Li-ion batteries (LIBs). Current RT Na-S batteries suffer from a series of fundamental materials challenges, resulting in poor battery performance, and these problems could be severely aggravated with decreasing operating temperatures, especially below −20°C. Thus, it is critical to tackle the fundamental problems through multi-faceted investigations on the electrochemical reaction mechanism as well as on the design, synthesis and processing of functional electrode and electrolyte materials. This thesis places emphasis on three major components in the Na-S system, namely Na metal anode, S-rich cathode and ether-based electrolyte.

The first part of the thesis focuses on the design of highly stable Na metal anode to solve the large volume change and severe metal dendrite growth issues, using a chemically engineered porous matrix as stable host and a protective solid electrolyte interphase (SEI) enabled by an electrolyte additive. The second part of this work investigates advanced S-rich cathode materials that are beyond conventional elemental S, including hollow sodium sulfide nanospheres and novel sodium phosphorothioates. These two strategies, respectively, mitigate the structural damage caused by volume expansion of elemental S and prevent the undesired precipitation of short-chain polysulfide. In the final part, electrolyte formulation is performed to optimize an ether-based electrolyte that can expand the temperature threshold of thermostability and contribute to a small increase on electrolyte resistance across temperatures. Using this electrolyte, long term stability of Na-S batteries operating over a wide temperature range (down to −80°C) is demonstrated.

Thesis Committee

• Prof. Weiyang Li, PhD (Chair)
• Prof. Jifeng Liu, PhD
• Prof. William Scheideler, PhD
• Prof. Jingyi Chen, PhD (UARK)

Contact

For more information, contact Daryl Laware at daryl.a.laware@dartmouth.edu.