Development of titanium and yttrium doped sodium-cobalt oxide cathods and their behaviour in cells with electrolytes based on NaTDI Hückel salt with NaPF6 salt additive

Abstract

To meet the needs for the increasing demands for portable energy storages, the alternatives for Li-ion batteries must be researched. One of the ideas is sodium-ion technology, where the development of the novel cathodic material and electrolytes is crucial. In this paper, the new types of electrodes based on the sodium-cobalt oxide doped with yttrium or cobalt are presented. For testing them in cells, at first only two electrolytes were introduced (0.75 M NaTDI in EC:DMC and 0.75M NaTDI in EC:DMC+3% FEC). However, during experiments, the performance of some cells was poor, even after initiating the new protocol of cell assembly. That is why new formulations with the best conductivity performance, physicochemical stability, and interfacial contact with metallic sodium electrodes were used for further testing of cathodes. During the SEM, Raman, EDS, and XRPD analysis, the full characterization of the active materials and electrodes was performed and the best composition of electrode and electrolyte have been chosen basing on the electrochemical cycling of the half-cell, which achieved 143.64 mAh·g −1 discharge capacity value. Also, the metallic sodium electrode stability studies were performed to study the influence of the electrolyte on the anodic side of the cell.