Iron(III) Oxalate Tetrahydrate: A New Positive Electrode for Li Batteries
LiFePO4 polyaionic compound offers low cost, environmental compatibility, high theoretical specific capacity (170 mAh/g) and has become the most praised material for the next generation of Li-ion batteries for EV’s [3-4].
Aside from the inorganics polyanionic compounds, we have recently shown the cost-wise attractiveness of some Fe-based phases having organic polyanions such as carbonates, oxalates, malonates, etc. These materials could be attractive electrodes due to their cost, low molecular weight and electronegativity. Herein, we report a new synthesis route to prepare Fe2(C2O4)3·4H2O and determine its crystal structure through X-ray powder diffraction coupled with neutron powder diffraction (Figure 1). We also show for the first time that iron(III) oxalate compound is electrochemical active versus lithium as it can reversibly insert 1.6 Li atom per formula unit at 3.35 V versus Li+/Li0 (Figure 2).
Beside reporting the synthesis and the crystal structure of Fe2(C2O4)3·4H2O phase, we will determine the structural changes driven by Li insertion using both in situ XRD and Operando Mössbauer measurements as will be discussed.
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