The Woodruff School

SUMMARY

With significant demand of decreasing the dependency of carbon-based energy to overcome the climate crisis, renewable energy systems utilizing abundant and clean natural resources such as sun, wind and oceans were developed. However, one of the main issues for the clean energy system is intermittency that energy production is inconsistent and difficult to meet the energy demand. In this regard, energy storage and conversion device gained much of attention. Among the storage and conversion devices, electrochemical energy storage (ESS) and conversion devices such as batteries and water electrolyser are the most promising system.
Proton exchange membrane water electrolyser plays an important role for storing electricity to hydrogen. In general, Iridium is usually chosen in acid solution for oxygen evolution reaction (OER) due to its high stability. However, expensive cost of iridium hinders the usage of the metal as an OER catalyst. In this study, we have synthesized iridium-free OER catalyst, yttrium ruthenium pyrochlore oxide (YRO), with sol-gel method. Not only the synthesized catalyst demonstrated performance improvement of more than double compared to conventional IrO2 catalyst, the OER performance was more improved by surface modification.
Lithium metal battery is an advanced system compared to lithium-ion batteries, which have advantages of high theoretic capacity, low reduction potential, and low density. However, dendrite formation during charge and discharge cycles presents a major challenge for lithium metal batteries. In this study, we have utilized two nanomaterials to suppress dendrite formation and improve the cycling stability of the battery. First, cross-linked carboxyl group functionalized polymer with intrinsic microporosity (PIM-COOH) was deposited on lithium metal anode. The introduction of polymerized PIM-COOH is expected to improve lithium-ion selectivity, suppress the dendrite formation, improving the cycle stability. Second, chemically exfoliated Molybdenum disulfide (MoS2) nanosheet is applied to metal anode interface. exfoliated 1T-MoS2 interlayer is expected to not only suppress the dendrite formation but also affect the lithium deposition morphology during the cycle.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Keun Hee Kim

TIME:	Wednesday, June 5, 2024, 10:30 a.m.

PLACE:	MRDC Building, 3515

TITLE:	Comprehensive understanding of electrochemical energy storage and conversion by surface modification of inorganic OER catalyst and introduction of nanomaterials to improve electrochemical performance

COMMITTEE:	Dr.Seung Woo Lee, Chair (Mechanical Engineering) Dr.Jinho Park (Georgia Tech Research Institute) Dr.Matthew T. McDowell (Material Science of Engineering) Dr.Hailong Chen (Mechanical Engineering) Dr.Seung-Kyum Choi (Mechanical Engineering)

SUMMARY With significant demand of decreasing the dependency of carbon-based energy to overcome the climate crisis, renewable energy systems utilizing abundant and clean natural resources such as sun, wind and oceans were developed. However, one of the main issues for the clean energy system is intermittency that energy production is inconsistent and difficult to meet the energy demand. In this regard, energy storage and conversion device gained much of attention. Among the storage and conversion devices, electrochemical energy storage (ESS) and conversion devices such as batteries and water electrolyser are the most promising system. Proton exchange membrane water electrolyser plays an important role for storing electricity to hydrogen. In general, Iridium is usually chosen in acid solution for oxygen evolution reaction (OER) due to its high stability. However, expensive cost of iridium hinders the usage of the metal as an OER catalyst. In this study, we have synthesized iridium-free OER catalyst, yttrium ruthenium pyrochlore oxide (YRO), with sol-gel method. Not only the synthesized catalyst demonstrated performance improvement of more than double compared to conventional IrO2 catalyst, the OER performance was more improved by surface modification. Lithium metal battery is an advanced system compared to lithium-ion batteries, which have advantages of high theoretic capacity, low reduction potential, and low density. However, dendrite formation during charge and discharge cycles presents a major challenge for lithium metal batteries. In this study, we have utilized two nanomaterials to suppress dendrite formation and improve the cycling stability of the battery. First, cross-linked carboxyl group functionalized polymer with intrinsic microporosity (PIM-COOH) was deposited on lithium metal anode. The introduction of polymerized PIM-COOH is expected to improve lithium-ion selectivity, suppress the dendrite formation, improving the cycle stability. Second, chemically exfoliated Molybdenum disulfide (MoS2) nanosheet is applied to metal anode interface. exfoliated 1T-MoS2 interlayer is expected to not only suppress the dendrite formation but also affect the lithium deposition morphology during the cycle.