An anode material for lithium‐ion batteries based on oxygen‐deficient perovskite Sr${}_2$Fe${}_2$O${}_{6-\delta }$

The application of oxygen‐deficient perovskites as anode for lithium‐ion batteries has been explored through case study of Sr${}_2$Fe${}_2$O${}_{6-\delta }$. The structure of this material was studied through Rietveld refinements with X‐ray diffraction data, while X‐ray photoelectron spectroscopy and iodometric titration were utilized to determine the oxidation state of the transition metal and the degree of oxygen‐deficiency. As anode, Sr${}_2$Fe${}_2$O${}_{6-\delta }$ delivers discharge capacity of 393 mAh g${}^{-1}$ at a current of 25 mA g${}^{-1}$ after 50 cycles. This capacity is higher than the theoretical capacity of graphite anode, 372 mAh g${}^{-1}$. It is also higher than that of the calcium‐analogue reported before. At different current densities from 25–500 mA g${}^{-1}$, the charge‐discharge cycles remain highly reversible, indicating the great potential of Sr${}_2$Fe${}_2$O${}_{6-\delta }$ for application as anode for lithium‐ion batteries. The mechanism of lithium intercalation and de‐intercalation has been discussed. (© 2020 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)