Harbin Institute of Technology (Shenzhen)
Dr. Kaikai Li obtained his PhD degree from the Hong Kong University of Science and Technology. He joined the School of Materials Science and Engineering at Harbin Institute of Technology (Shenzhen) as an Assistant Professor in 2020. His current research interest focuses on understanding the phase transformations and mechanics of materials during electrochemical ion insertion using in-situ experimental probes as well as theoretical calculations and modeling, and exploring the potential applications that could be inspired by these findings. He has published more than 40 papers in peer-reviewed journals like Nature Communications, EES, Nano Letters.
Structural evolutions are often observed during lithium/sodium insertion/extraction and are highly relevant to the numerous performance metrics of materials. For example, a first-order phase transition occurs in ion-insertion materials to store energy reversibly with formation of a distinct new structural phase. Or sometimes, the ion insertion may not involve with crystal structural changes, but with obvious electronic structure changes and lattice expansion/distortion. This kind of structural evolution often endows the host materials with interesting properties. An in-depth study of the structural evolutions of the materials is of significance for not only improving their performance but also expanding their applications.
This presentation explores the evolution of crystal and electronic structures in MoS2 and RuO2 during electrochemical lithium/sodium ion insertion. It reveals that MoS2 undergoes distinct phase transformation pathways in ether-based and ester-based electrolytes, leading to the exfoliation of bulk 2H-MoS2 into few-layer nanosheets with 1T-phase and controlled layers. The resulting bilayer 1T-MoS2 nanosheets exhibit enhanced electrocatalytic performance for hydrogen evolution compared to pristine 2H-MoS2. This approach can be easily extended to exfoliate various transition metal dichalcogenides (TMDs). Additionally, the presentation shows that electrochemical lithium/sodium insertion into RuO2 induces lattice strain/distortion and changes in electronic structure of the metal cations, demonstrating promising applications in oxygen evolution reactions.
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