TiO2 is a welll known material for energy (batteries and supercapacitors) aplications. This have been widely used as anode in Li-ion batteries thanks to its easy processing, relatively abudance, reversibility and that storage Li-ion in a safe potential avoiding the reduction of the organic electrolyt to form the SEI. Among all the TiO2 polymorphs, the monoclininc TiO2(B) exhibit the best performance thanks to its larger interstitials to storage ions, largers ionic conductivity and the alignment of open chanels to transport the ions. Nevertheless, this polymorph have not been widely employed as anode in Na-ion batteries and its performance remain bellow to that of the TiO2 anatase. Furthermore, incorporing carbon nanoestructures to TiO2 based materials is a widely employed strategy to improve the performance of the material thanks to the increment of the conductivity of the composite and the larger surface area. For this reason, the effect of incorporing carbon nanoestructures (graphene oxide and carbon nanotubes) during the synthesis of TiO2(B) over their morphology and performance in the Na-ion storage process, is studied in the present work.

TiO2(B) was synthesized by hydrothermal treatment in 10 M NaOH followed by hydrolysis and thermal treatment at 400 °C during 4 h. Carbon nanoestructures were incorporated by previously forming a core@shell structure with amorphous TiO2 through controlled hydrolisis of Titanium isopropoxide under reflux, or by preparing a suspension of the carbon nanostructure and amorphous TiO2, and then the TiO2(B) was formed as indicated before. The materials were characterized by XRD, Raman, XPS, SEM, TEM and BET. A two-electrode swagelock cell was assembled by coating a copper foil with a ink of active material:carbon black:PVDF (80:10:10) in N-methyl-Pyrrolidone, and metallic Na as counter and reference electrode. A Whatman glass-fiber separator soaked in 1 mol L− 1 NaPF6 in 1:1 dimethyl carbonate/ethylene carbonate electrolyte was used as separator. The materials were characterized by Cyclic voltammetry, charge-discharge curves and electrochemical impedance spectroscopy. The impact of carbon nanostructure over the specific capacity of Na-ion storage and apparent Na-ion diffusion coeficient in the TiO2(B) willl be discussed in the presentation of the work.