Enhanced high rate performance of α-Fe2O3nanotubes with alginate binder as a conversion anode

Abstract

Interactive binders are of current interest to the lithium-ion battery community because they are beneficial for alloy-based anodes. They can accommodate the extra stress generated during the reaction with lithium well and alleviate the pulverization problem associated with the alloying–dealloying process. One of the best examples of an interactive binder is sodium alginate, which has recently being used in silicon-based anodes. The silicon–alginate binder combination has exhibited excellent electrochemical reactivity and stability. Herein, we have utilized the interactive properties of the alginate binder along with the hollow nanostructural features of α-Fe₂O₃ nanotubes in order to achieve an excellent conversion-based anode for lithium-ion batteries. In this regard, α-Fe₂O₃ is synthesized using a simple hydrothermal method and the hollow nanostructured α-Fe₂O₃ nanotubes have shown a stable high capacities of about 800 mAh g⁻¹ at 503 mA g⁻¹ for 50 cycles with alginate binder. Even at a high current rate of 1007 mA g⁻¹ (∼1C), high capacity of 732 mAh g⁻¹ and 600 mAh g⁻¹ has been achieved after 50 and 100 cycles respectively. The same electrode assembly has shown an excellent high rate capability and delivered a capacity of 400 mAh g⁻¹ even at a very high current density of 10 A g ⁻¹. In this report we propose that weak hydrogen bonding between the surface hydroxyl groups on the metal oxide (Fe₂O₃) and the carboxylic functional groups on the alginate binder is responsible for the enhanced battery performance at very high current rates.