Evaluation of Sn0.9Fe0.1O2‐δ as Potential Anode Material for Sodium‐Ion Batteries

New insights: Doping SnO₂ with iron combined with a carbon coating and fluoroethylene carbonate as electrolyte additive results in a triplication of the reversible capacity. The comprehensive electrochemical characterization coupled with ex situ/operando XRD and TEM yields valuable insights into the impact of the iron dopant and the remaining challenges.

Abstract

The introduction of transition metals such as iron in oxides of alloying elements as, for instance, SnO₂ has been proven to enable higher capacities and superior charge storage performance when used as lithium-ion electrode materials. Herein, we report the evaluation of such electrode materials, precisely (carbon-coated) Sn_0.9Fe_0.1O_2−δ (−C), for sodium-ion battery applications. The comparison with SnO₂ as reference material reveals the beneficial impact of the presence of iron in the tin oxide lattice, enabling higher specific capacities and a greater reversibility of the de-/sodiation process – just like for lithium-ion battery applications. The overall achievable capacity, however, remains relatively low with about 300 mAh g⁻¹ and up to more than 400 mAh g⁻¹ for Sn_0.9Fe_0.1O_2-δ and Sn_0.9Fe_0.1O_2−δ -C, respectively, compared to the theoretical specific capacity of more than 1,300 mAh g⁻¹ when assuming a completely reversible alloying and conversion reaction. The subsequently performed ex situ/operando XRD and ex situ TEM/EDX analysis unveils that this limited capacity results from an incomplete de-/sodiation reaction, thus, providing valuable insights towards an enhanced understanding of alternative reaction mechanisms for sodium-ion anode material candidates.

Zum Volltext