(Invited) Reversible Co-Intercalation of Sodium and Solvent in Graphite

Thursday, October 15, 2015: 16:00
101-B (Phoenix Convention Center)
H. Kim (Seoul National University), J. Hong (Seoul National University), G. Yoon (Seoul National University, Center for nanoparticle research, IBS), H. Kim (Department of Energy Science, Sungkyunkwan University), K. Y. Park (Seoul National University), M. S. Park (Korea Electronics Technology Institute), W. S. Yoon (Department of Energy Science, Sungkyunkwan University), and K. Kang (Center for Nanoparticles Research, IBS)
Graphite is a universal host materials that can accommodate various guest species in its galleries. Its capability of reversible lithium de/intercalation facilitates graphite as a standard anode for lithium ion batteries, while the thermodynamic instability of sodium intercalation made it not suitable for sodium ion batteries. We recently discovered that reversible solvated-Na ion intercalation enables graphite to become a promising anode for sodium ion batteries. As a continuous effort to exploit the graphite as an anode in sodium ion batteries, here we investigate the solvated-Na intercalation mechanism through in operando X-ray diffraction analysis, electrochemical titration, real-time observation of graphite expansion and density functional theory-based calculations. This work demonstrates the formation of first-stage graphite intercalation compound where the solvated-Na ions are doubly stacked in parallel with graphene layers. We further provide insights on tuning energy storage potentials of solvated ion intercalation electrodes by introducing various solvents.