Fig. 1

Characterization of pristine materials and electrochemical properties. a Typical morphology of S-ZFO (scale bar: 10 nm) and b the corresponding SAED pattern. c Typical morphology of L-ZFO (scale bar: 10 nm) and d the corresponding SAED pattern. e HAADF-STEM image showing the spinel structure along the <101> zone axis, compared to an overlaid atomic model along the same projection. Scale bar: 1 nm. f Size distribution of S-ZFO (blue) and L-ZFO (green). g Discharge profile of S-ZFO (blue) and L-ZFO (green) measured at the rate of 200 mAg⁻¹. Inset shows the OCV profile of S-ZFO and L-ZFO, respectively