α-Fe2O3 Nanostructures: Inorganic Salt-Controlled Synthesis and Their Electrochemical Performance toward Lithium Storage

By applying the concept of an inorganic structure-directing agent, uniform alpha-Fe2O3 nanospheres of about 300 nm in diameter and well-defined nanorhombohedra of about 50-80 nm in size have been successfully synthesized using the simple inorganic sodium salt of NaAc and NaCl as the only structure-directing agent in the hydrothermal system, respectively. In comparison, only micrometer sphere-like aggregates composed of irregular nanoparticles of about 80-120 nm were obtained without the presence of any inorganic salt additives. All three nanostructures are investigated with XRD, SEM, TEM, and electrochemical tests toward lithium storage. It is found that the particle size and shape hits a remarkable effect on the lithium insertion/extraction behavior. Among the three alpha-Fe2O3 nanostructures, nanospheres show a very high specific capacity of >600 mA h g(-1) in the initial 10 cycles and >414 mA h g(-1) after 60 cycles as well as good cycling performance, exhibiting great potential as anode materials in lithium-ion batteries. It benefits from the proper submicrometer size with the right surface area and the spherical shape.