The redox mechanism of FeS2 in non-aqueous electrolytes for lithium and sodium batteries

Primary Li/FeS2 batteries have been commercialized and rechargeable Li-alloy/FeS2 batteries have been successfully operated at 375-500 degrees C by employing LiCl-based molten electrolytes. However, non-aqueous electrolyte rechargeable Li/FeS2 batteries have not yet been fulfilled due to poor reversibility and rapid capacity fading. The redox mechanism of FeS2 in non-aqueous electrolytes at ambient temperature is poorly understood and is still debated. In this mini-review, we analyse the experimental observations reported previously and propose a suitable mechanism that can explain all of the phenomena observed from the non-aqueous electrolyte Li/FeS2 and Na/FeS2 batteries.