Hollow Spherical Oxygen-Rich Vacancy B-Site Ordered Double Perovskites for Advanced Supercapacitor Application

The high ionic conductivity, large surface area, and ion-diffusion characteristics, among other compelling qualities, make perovskite oxides promising for supercapacitor (SC) application. Particularly, La based double perovskites possess high charge storage capacity and meritorious redox capabilities. Nevertheless, attaining improved electrochemical performance without structural transformation is still lacking. This work presents a hollow spherical-double perovskite (HSDP) structure, designed by exploiting the (1) B-site in double perovskite (B′ and B″) structure to incorporate more than one active element, (2) high oxygen vacancy concentration for maximum anion intercalation, and (3) hollow spherical structures to retain their structural integrity during ion intercalation. The prepared HSDP has a specific surface area that is 10x higher than the original double perovskite (DP) structure. When applied as an electrode material for SC, HSDP shows a high specific capacity of 805 F g⁻¹ at the current density of 0.5 A g⁻¹. When assembled against active carbon electrode as an asymmetric supercapacitor, an energy density as high as 38 Wh kg⁻¹ at a power density of 750 W kg⁻¹ is achieved with a capacity retention of 88%. The formation of single-phase HSDP with ample oxygen vacancies, as well as the anion intercalation mechanism, are explored in detail.