Effect of Titanium Substitution in a P2-NaCoTiO Cathode Material on the Structural and Electrochemical Properties.

Worries about lithium supplies have led to the development of research on sodium batteries. Sodium-ion batteries are regarded as the next generation of energy-storage devices thanks to the generous resources of sodium. In spite of that, structural changes in the electrode materials remain the main challenge of this storage technology. NaCoO has been widely investigated as a competitive candidate for LiCoO. It has been found that the electrochemical cycling curves of this material present numerous potential steps as a result of electronic transitions and/or structural ordering. From this standpoint, this paper reports a novel cathode material, NaCoTiO, where 5% of cobalt was replaced by titanium, prepared via a facile solid-state route. The sodiation/desodiation mechanism of this layered material was investigated. Na//NaCoTiO exhibits a first initial capacity of 119 mAh/g in the potential window 2-4.2 V with less potential jumps in the potential versus capacity curve compared to NaCoO. Genuinely, the electrochemistry of this material demonstrated a reversibility upon the insertion/desinertion process with low polarization. In situ synchrotron investigations on NaCoTiO reveal the occurrence of reversible ordered phases. Ex situ magic-angle-spinning NMR disclosed different environments around sodium starting from the pristine state to the end of charge.