Advanced Electrode Materials Based on Brownmillerite Calcium Ferrite for Li‐Ion Batteries

Abstract Iron‐based materials are considered potential anode materials for lithium‐ion batteries thanks to their low cost, abundancy, non‐flammability, good safety, environmental benignity, and high specific capacity. Here, a series of calcium iron oxides materials having brownmillerite structure (i. e., Ca₂Fe_2‐xM_xO₅, where M=Mn, Ni and Cu and x=0 and 0.1) has been extensively studied for their use as conversion anodes in lithium cell. In particular, a mechanochemical approach has been used either to synthesize the samples and to prepare electrodes for the tests in lithium cell. Ca₂Fe₂O₅ based electrodes proved excellent performance in lithium cell, approaching the theoretical capacity and being stable upon prolonged cycling (529 mAh g⁻¹ at C/10 and a capacity retention of 81 % after 100 cycles). Through the use of ex‐situ diffraction measurements, we have analyzed the conversion mechanism and proved the partial reversibility of its electrochemical reaction. Also, the incorporation of dopants into the structure of calcium iron oxide resulted in further improvement of its electrochemical performance as is the case of Mn doped sample that show a considerable specific capacity of 567 mAh g⁻¹ and the capacity retention is almost 99 % after 100 cycles.