Solid State Enabled Reversible Four Electron Storage

We report that a solid-state battery architecture enables the reversible, four electron storage of fully utilized solvothermally synthesized cubic-FeS2 (pyrite). With a sulfide based glass electrolyte we successfully confine electro-active species and permit the safe use of a lithium metal anode. These FeS2/Li solid-state cells deliver a theoretical specific capacity of 894 mAh g-1 at 60 degrees C. We find that nanoparticles of orthorhombic-FeS2 (marcasite) are generated upon recharge at 30-60 degrees C which explains a coincident change in rate kinetics.