Stable Cycling of Lithium Batteries Utilizing Iron Disulfide Nanoparticles

Of the many factors that control whether a battery chemistry is realistic or not, the harmony between the anode and cathode is of the upmost importance. To design a lithium-based battery that utilizes conversion chemistry, any optimization of the anode or cathode must not sacrifice the performance of the other electrode. Here, for the first time, we demonstrate the application of synthesized FeS2 nanoparticles (npFeS2) as a cathode material specifically coupled with an optimized electrolyte for lithium metal cycling. Additionally, implementing a voltage-limited cycling protocol for this system produces a stable-cycling npFeS2–Li battery. Using a suite of spectroscopy and microscopy techniques, along with elemental and thermogravimetric analyses, we show that the FeS2 nanoparticles have the crystal structure of pyrite and contains less than 12 wt % ligand. Cycling of these nanoparticles in a lithium cell with a maximum charging voltage of 2.4 V shows a high average capacity of 421 mA h/g over 80 cycles. Furthermore, we show that uniform submicron FeS2 particles are essential for avoiding detrimental polysulfides, even with a 2.4 V limited charging voltage. Nanoparticle design, consideration of the electrolyte, and voltage conditions are the necessary steps for using FeS2 in practical energy-dense lithium batteries.