Anodic Potential and Conversion Chemistry of Anhydrous Iron (II) Oxalate in Na-Ion Batteries

Anhydrous ferrous (II) oxalate (AFO) outperforms its hydrated form when used as an anode material in Li-ion batteries (LIBs). With the increasing interest in Na-ion batteries (NIBs) in mind, we examine the potential of AFO as the anode in NIBs through first principles calculations involving both periodic and non-periodic structures. Our analysis based on periodic (non-periodic) modeling scheme shows that the AFO anode generates a low reaction potential of 1.22 V (1.45 V) in the NIBs, and 1.34 V (1.24 V) in the LIBs, which is much lower than the potential of NIBs with mixed oxalates. The conversion mechanism in the underlying electrochemical process involves the reduction of Fe2+ with the addition of Na or Li. Such conversion electrodes can achieve high capacities through the Fe2+ valence states of iron.

Automated summary

Anhydrous ferrous oxalate performs better than its hydrated form as an anode in Li-ion batteries. By conducting first principles calculations, we investigate the potential of anhydrous ferrous oxalate as an anode in Na-ion batteries. Our analysis shows that anhydrous ferrous oxalate generates a lower reaction potential in Na-ion batteries and Li-ion batteries compared to mixed oxalate-based Na-ion batteries. This conversion electrode achieves high capacities through the Fe2+ valence states of iron.