Chemistry and electrochemistry of nanostructured iron oxyhydroxides as lithium intercalation compounds for energy storage Original Research Article

The structural characterization and electrochemical performance of three nanosized iron oxyhydroxides (β-FeOOH, γ-FeOOH and δ-FeOOH) are reported in this work. The interest of having small particle sizes is to be able to circumvent the low intrinsic ionic conductivity of these materials through the increase of the active volume proportion of the operating grain, during the insertion process. Low temperature synthesis routes, in aqueous media, were thus used to obtain such crystallites with nanometer dimensions. The theoretical specific capacity of these materials is as high as 300 mA h g−1 which is actually very interesting for lithium batteries applications. However, the electrochemical behaviour greatly depends on the structure of the compounds. A phase transformation was, for example, evidenced in the case of γ-FeOOH first lithiation whereas the best performance were obtained with β-FeOOH, which develops a stable capacity of 180 mA h g−1, after 10 cycles, at C/10.