Effect of Mn Substitution on GeFe2O4 as an Anode for Sodium Ion Batteries

Abstract

GeFe2O4 (GFO), with its intriguing intercalation mechanism based on alloying–conversion reactions, was recently proposed as an anode material for sodium ion batteries (SIBs). However, drawbacks related to excessive volume expansion during intercalation/deintercalation and poor electronic conductivity enormously hinder its practical application in batteries. In this regard, some experimental strategies such as cation substitutions and proper architectures/carbon coatings can be adopted. In this paper, pure and Mn-doped GFO samples were prepared by hydrothermal synthesis. The doped samples maintained the spinel cubic structure and the morphology of pure GFO. The electrochemical tests of the samples, performed after proper carbon coating, showed the expected redox processes involving both Ge and Fe ions. The Mn doping had a positive effect on the capacity values at a low current density (about 350 mAh/g at C/5 for the Mn 5% doping in comparison to 300 mAh/g for the pure sample). Concerning the cycling stability, the doped samples were able to provide 129 mAh/g (Mn 10%) and 150 mAh/g (Mn 5%) at C/10 after 60 cycles.

Pure and (Sn or Mg) Doped GeFe2O4 as Anodes for Sodium-Ion Batteries

“…As previously explained, doping could be a winning approach to improve the electrochemical performances of electrode materials. In the literature, there is only one paper reporting the effect of doping on GFO samples obtained from hydrothermal synthesis, in particular, the Mn doping on Fe crystallographic sites [30]. In the current case, doping was supposed to occur on Ge sites, and the dopants were chosen with two different aims.…”

“…As discussed, doping for electrode materials could be a strategy to improve their structural stability and increase electron conductivity [9,29]. For GFO, up to now, only Mn doping has been reported [30].…”