To further investigate how a Fe2O3/XC cathode could lead to a lower charge overpotential, the morphologies of both XC and Fe2O3/XC cathodes after discharge and charge were examined, as presented in Fig. 4. After discharge to 2.0V at a current density of 200 mA g1 , the products in both cathodes exhibit a disc-like morphology (Fig. 4c and d), which is consistent with the previous reported Li2O2 morphology [27–29]. After the charge process, some mud-like aggregates still remain in the XC cathode (Fig. 4e), which is consistent with the charge profile of a low coulombic efficiency (94.2%) and other reported results [52], indicating the poor rechargeability of XC cathode. In contrast, for the Fe2O3/XC cathode, the generated Li2O2 product is completely decomposed, leaving a clear cathode (Fig. 4f), which is identical to the initial one.
This implies that Fe2O3 can effectively catalyze the decomposition of Li2O2 during the charge process. The introduction of Fe2O3 nanoparticles onto the carbon surface can induce many more deposition sites for Li2O2, and this result in a thinner disc-like morphology of Li2O2, providing more interfaces between the cathode/Li2O2 and Li2O2/electrolyte, and thus resulting in an enhanced rechargeability [53–55].