Effect of binder materials on cycling performance of Fe ₂O ₃ electrodes in alkaline solution

To investigate the effects of binder materials on the electrochemical properties of Fe ₂O ₃ electrodes in alkaline solution, four different materials were applied as binders: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethelene (PE), and poly tetrafluoroethylene- co-vinylidene (P(TFE-VDF)). In KOH aqueous solutions, electrodes containing different binders showed quite different properties. The PE-containing electrode showed the highest capacity retention up to 14 cycles (330 mAh g ^-1, 82.7%). However, capacity fading was observed subsequently, and only 24.6% capacity remained after 30 cycles. In contrast, the PTFE-containing electrode showed continuous capacity fading but the best capacity retention of 38.6% after 30 cycles. Comparing the amount of dropout Fe ₂O ₃ from electrodes after charge/discharge measurements, it was reasonable to find that the electrodes with better cycling performance showed less Fe ₂O ₃ dropout. When K ₂S additives were applied, both the electrodes fabricated with PTFE and PE showed superior cycling performance, which was attributed to the good stability of PTFE and PE binders. However, when the effect of the K ₂S additive on the Fe ₂O ₃ dropout was studied with PTFE-containing electrodes, heavier Fe ₂O ₃ dropout was observed in the K ₂S-added electrolyte. This indicated that Fe ₂O ₃ dropout was not a dominant factor for the capacity fading of the electrodes.