Free Energy Landscape of Sodium Solvation into Graphite

Sodium Ion Batteries (SIBs) are the most cost-effective alternative to current generation lithium ion batteries (LIBs), ^[1,2] but Na is known to deliver very low energy capacity for sodium intercalation compared to Lithium. We report here first principles moleculars dynamics aided by metadynamics ^[3] to obtain the free energy landscape including changes in the electronic coupling as a sodium ion in Dimethyl sulfoxide solvent intercalates into graphite, the first step in understanding how the local environment affects the free energy of solvation. We analyze the free energy landscape for all the possible sodium solvation scenarios, while quantifying their free energy barriers. Our simulations indicate that solvent plays an important role in stabilizing the sodium intercalation into graphite through shielding of the sodium while modulating the interaction of the solvent with the graphite sheets ^[4].

References

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2. H. Kim, J. Hong, G. Yoon, H. Kim, K. Y. Park, M. S. Park, W. S. Yoon, K. Kang. Energy Environ. Sci. 2015, 8, 2963−2969.
3. CP2K version 2.6.2 (Development Version), CP2K is freely available from http://www.cp2k.org
4. A. Kachmar, W. A. Goddard. J. Phys. Chem. C. 2018, 122(35), 20064-20072.