Controlling Electrochemical Lithiation/Delithiation Reaction Paths for Long-cycle Life Nanochain-structured FeS2 Electrodes

Pyrite (FeS2) stands out from other metal sulfides due to its abundance, low toxicity and high specific energy density. However, the low utilization and short cycle life of FeS2 caused by irreversible side reactions and dramatic structural changes during charge/discharge process seriously hinders its practical application. In this work, we designed FeS2 nanochains to address these issues because this unique structure not only shortens the ion/electron diffusion distance, increases the electrode/electrolyte contact area, but also accommodates the strain associated with Li ion intercalation and deintercalation reactions. Compared with nanoparticles, the FeS2 nanochains synthesized by magnetic-field-assisted aerosol pyrolysis could cycle up to 800 cycles at 0.5C, remained a discharge capacity of 342.4 mA h g−1 in the voltage range of 1.0-2.6 V and achieved a remarkable capacity fading rate of 0.02% per cycle, which is among the best values demonstrated so far for Li/FeS2 cells. In-situ Raman experiments revealed that the irreversible side reactions could be suppressed through controlling the voltage window, which can be benefit for further improving the performance of Li/FeS2 cells. © 2016 Elsevier Ltd