Low-cost Fe-based electrode materials for Li-ion energy storage devices attract lots of attention. In this work, porous Fe2O3 nanoparticles are synthesized by a simple route. Firstly, their lithium storage performance is investigated by assembling half-cell configurations with Li foil as the counter electrode. During initial dozens of cycles, capacities of Fe2O3 nanoparticles fall off rapidly, which is related to continuous growth of solid electrolyte interphase (SEI). Amazingly, the capacities show an upturn in extended cycles. The pseudocapacitance of activated capacities is revealed by executing cyclic voltammetry (CV) tests at various scan rates on 500-cycled Fe2O3 electrodes. Based on electrochemical results, we speculate this special cycling performance of Fe2O3 nanoparticles may be associated with reversible electrochemical processes of SEI under the catalysis of nano-size Fe. Further, 500-cycled Fe2O3 anodes are reassembled with activated carbon cathodes for Li-ion capacitors (LICs). The LICs show energy densities of 110 Wh kg−1 at power densities of 136 W kg−1, and 72.8% capacity retention after 3000 cycles at 2 A g−1. We report an interesting electrochemical behavior of porous Fe2O3 nanoparticles, and a high-performance LIC based on activated Fe2O3 as an anode. This work may offer a new understanding for lithium storage capacities of metal oxide anodes.

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