The controlled synthesis and improved electrochemical cyclability of Mn-doped α-Fe₂O₃ hollow porous quadrangular prisms as lithium-ion battery anodes

A two-step process of initial oxalate co-precipitation and subsequent thermal decomposition facilitates the formation of hydrated oxalate precursors with hollow quadrangular prism shapes, and then confers a porous nature for the prismatic shells of synthetic hematite (α-Fe₂O₃) and its Mn-doped derivative. When applied as lithium-ion battery anodes, Mn-doped α-Fe₂O₃ exhibits an improved electrochemical performance compared with undoped α-Fe₂O₃. At a current density of 200 mA g^-1, the pure α-Fe₂O₃ electrode gives an initial discharge capacity of ∼1280 mA h g^-1 with a low retention ratio of 13.9% (i.e., capacity ∼ 178 mA h g^-1) over 80 cycles, while the Mn-doped product, rhombohedral Fe_1.7Mn_0.3O₃, delivers a relatively low initial value of ∼1190 mA h g^-1 and retains an 80^th cycle reversible capacity of ∼1000 mA h g^-1 (i.e., retention ratio ∼ 84.0%). These, together with the better high-rate capability and the lower charge-transfer resistance of the Mn-doped α-Fe₂O₃ anode, simultaneously demonstrate a successful mass production of hollow porous configurations and an effective doping with elemental Mn for potential application. © The Royal Society of Chemistry 2015.