Toward a Better Understanding on Na-Air Batteries

Na-air battery (or Na-oxygen battery) is a newly developed member of metal-air batteries and is attracting increasing research interest due to its environmentally benign characteristics and high theoretical energy density, which can be comparable to gasoline, making them attractive candidates for use in electrical vehicles.1–3 The concept of sodium-air batteries (SABs) are similar to lithium-air batteries (LABs) that were widely studied over the last decades.4 However, the poor cycling life and low energy efficiency (high charging overpotential) of LABs and SABs hinder their commercialization.4-5 Compared to the numerous reports of LABs, the research on SABs is still in its infancy. Although SABs show a number of attractive properties such as low charging overpotential and high round-trip energy efficiency, their cycling life is currently limited to a few tens of cycles. Lithium and sodium elements share similar chemical properties, however, the chemistry and electrochemistry of LABs and SABs are not the same. While the discharge product of LABs is well-recognized to be lithium peroxide (Li2O2), both sodium peroxide (Na2O2) and superoxide (NaO2) have been detected as the discharge product of SABs in a number of different studies. Therefore, understanding the chemistry behind SABs is critical towards enhancing their performance and advancing their development. In order to deepen the understandings on Na-air batteries, our group have applied nanostructured carbon materials as cathodes to investigate various effects including functional groups on graphene,6 surface area of porous carbon black,7 current density on CNTs/NCNTs,8 building 3D electrodes,9 and influence of humidity on rechargeability.10 Furthermore, the determining kinetics factors for controlling the chemical composition of the discharge products in SABs will be discussed and the potential research directions toward improving SABs are proposed. The perspectives in this field will be also anticipated. This poster will present the summary of the recent studies 6-10 and newfound results 11 on Na-air batteries from our group. 1.  E. Peled, D. Golodnitsky, H. Mazor, M. Goor, S. Avshalomov, J. Power Sources 2011, 196, 6835. 2.  Q. Sun, Y. Yang, Z. W. Fu, Electrochem. Commun. 2012, 16, 22. 3.  P. Hartmann, C. L. Bender, M. Vracar, A. K. Durr, A. Garsuch, J. Janek, P. Adelhelm, Nat. Mater. 2013, 12, 228. 4.  J. Wang, Y. Li, X. Sun, Nano Energy 2013, 2, 443. 5.  H. Yadegari, Q. Sun, X. Sun, Na-O2 Batteries-A Review, submitted. 2015 6.  Y. Li, H. Yadegari, X. Li, M. N. Banis, R. Li, X. Sun, Chem. Commun. 2013, 49, 11731. 7.  H. Yadegari, Y. Li, M. N. Banis, X. Li, B. Wang, Q. Sun, R. Li, T. K. Sham, X. Cui, X. Sun, Energy Environ. Sci. 2014, 7, 3747. 8.  Q. Sun, H. Yadegari, M. N. Banis, J. Liu, B. Xiao, B. Wang, S. Lawes, X. Li, R. Li, X. Sun, Nano Energy, 2015, 12, 698. 9.  H. Yadegari, M. N. Banis, B. Xiao, Q. Sun, X. Li, A. Lushington, B. Wang, R. Li, T. K. Sham, X. Cui, X. Sun, Chem. Mater. 2015, 27, 3040. 10.  Q. Sun, H. Yadegari, M. N. Banis, J. Liu, B. Xiao, X. Li, C. Langford, R. Li, X. Sun, J. Phys. Chem. C 2015, 119, 13433. 11.  X. Sun et al., submitted.