Biomineralized α-Fe2O3: texture and electrochemical reaction with Li
Sustainable batteries call for the development of new eco-efficient processes for preparation of electrode materials based on low cost and abundant chemical elements. Here we report a method based on bacterial iron biomineralization for the synthesis of α-Fe2O3 and its subsequent use as a conversion-based electrode material in Li batteries. This high-yield synthesis approach enlists (1) the room temperature formation of γ-FeOOH via the use of an anaerobic Fe(II)-oxidizing bacterium Acidovorax sp. strain BoFeN1 and (2) the transformation of these BoFeN1/γ-FeOOH assemblies into an alveolar bacteria-free α-Fe2O3 material by a short heat treatment under air. As the γ-FeOOH precursor particles are precipitated between the two membranes of the bacterial cell wall (40 nm–thick space), the final material consists of highly monodisperse nanometric (∼40 × 15 nm) and oriented hematite crystals, assembled to form a hollow shell having the same size and shape as the initial bacteria (bacteriomorph). This double level of control (nanometric particle size and particle organization at the micrometric scale) provided powders exhibiting (1) enhanced electrochemical reversibility when fully reacted with Li and (2) an impressive high rate capability when compared to non-textured primary α-Fe2O3 particles of similar size. This bacterially induced eco-efficient and scalable synthesis method opens wide new avenues to be explored at the crossroads of biomineralization and electrochemistry for energy storage.