Spintronic state-induced interface reconfiguration of 2H-perovskite related oxides for pseudocapacitance increase

Perovskite oxides are able to realize pseudocapacitive energy storage through oxygen anion intercalation. Herein, it is demonstrated that, based on the three 2H-perovskite related oxides Sr${}_6$Co${}_5$O${}_{15-x}$, Sr${}_5$Co${}_4$O${}_{12-x}$, and Sr${}_5$Co${}_3$NiO${}_{12-x}$ as the research objects, metal oxyhydroxides generated through surface reconfiguration during electrochemical processes can contribute extra capacity besides the oxygen-anion intercalation. This is because the electron spin state controlled by the transition metal valence state in the pseudo trigonal prisms for the 2H-perovskite structure will affect the Jahn-Teller (JT) distortion. The strong JT distortion of Co${}^{2+}$ and Ni${}^{3+}$ would elongate metal-O bonds, thereby helping the formation of metal oxyhydroxides on the surface of the pristine material. Among the three 2H-perovskite related oxides, the specific capacity of Sr${}_5$Co${}_3$NiO${}_{12-x}$ having the most Co${}^{2+}$ and Ni${}^{3+}$ contents showed the highest capacity increase. This study will provide a promising pathway to develop advanced perovskite-like oxide pseudocapacitive materials. (© 2023 Wiley-VCH GmbH)