Influence of Synthesis Parameters on the Electrochemical and Interfacial Properties of Na2Ti3O7 As Anode for Na Ion Batteries
While for cathode materials many lithium analogues can be successfully used in SIB , the challenge is to find alternative anode materials , the reasons being the impossibility of sodium insertion into graphite and the formation of a stable SEI layer (Solid Electrolyte Interphase).
Na2Ti3O7 has been reported as the oxide with the lowest sodium insertion/deinsertion voltage at 0.3 V vs . Na+/Na and a capacity close to 200 mAh/g , becoming a very promising anode candidate both in terms of energy density and cost. However the reported capacity retention needs to be improved [4, 5] and the formation of a stable SEI layer remains to be proved.
Here we present a study were the role of several synthesis parameters, such as the sodium source precursor and the atmosphere during the cooling process, is correlated with the electrochemical properties of the sodium titanate, in particular, with the capacity retention which has been dramatically improved . The composition of the SEI layer has also been studied at different points of galvanostatic curve by means of XPS (X-ray photoelectron spectroscopy) combined in some cases with ion bombardment depth profiling.
 V. Palomares, M. Casas-Cabanas, E. Castillo-Martínez, M.H. Man, T. Rojo, Energy Environ. Sci., 2013, 6, 2312-2337.
 M. Dahbi, N. Yabuuchi, K. Kubota, S. Komaba, Phys. Chem. Chem. Phys., 2014, 16, 15007-15028.
 P. Senguttuvan, G. Rousse, V. Seznec, J.M. Tarascon, M.R. Palacín, Chem. Mater., 2011, 23, 4109-4111.
 H. Pan, X. Lu, X. Yu, Y.S. Hu, H. Li, X.Q. Yang, L. Chen, Adv. Energy Mater., 2013, 3, 1186-1194.
 A. Rudola, K. Saravanan, C.W Mason, P. Balaya, J. Mater. Chem. A, 2013, 1, 2653-2662.
 M. Zarrabeitia, E. Castillo-Martínez, J.M López del Amo, A. Eguía-Barrio, M.A. Muñoz-Márquez, T. Rojo, M. Casas-Cabanas (submitted)