Over the last century, the energy storage industry has continued to evolve, adapt, and innovate in response to changing energy requirements and advances in technology. Currently, energy storage systems are available for various large-scale applications and are classified into different types. In particular, electrical energy storage systems (EESS) in terms of electrochemical capacitors (ECs) and batteries have demonstrated great potential. In the last decades, research has focused on the development of all aspects of EES, electrolyte material among them. The perovskite-derived material Rb2Ti2O5 (RTO), has been recently found to display very interesting dielectric and conduction properties, showing an equivalent relative permittivity up to 10^9 at room temperature, high ionic conductivity, and very low electronic conductivity.