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

Abstract Pyrite (FeS 2 ) 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 FeS 2 caused by irreversible side reactions and dramatic structural changes during charge/discharge process seriously hinders its practical application. In this work, we designed FeS 2 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 FeS 2 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/FeS 2 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/FeS 2 cells.