Confining sulfur within a zeolite host wrapped inside conducting polymer sheaths as cathode for Li-S battery

Abstract

We discuss here the efficient confinement of sulfur and polysulfides within a non-carbonaceous ion conducting zeolite (NaY) host wrapped inside electronically conducting polyaniline (PAni) sheaths as a low-cost, high performance cathode for rechargeable lithium-sulfur battery. The sulfur is observed to be confined within the intra crystallite and interstitial spaces of the NaY zeolite and the (PAni) sheaths prevent leakage of sulfur (and polysulfides). Additionally, this NaY-PAni assembly provides distinct pathways for electrons (through PAni) and ions (through NaY channels and across PAni sheaths) during battery operation. Raman spectroscopy confirms the presence of sulfur in diradical S₈* chain forms in the cylindrical pores of NaY and as far our knowledge is concerned, this is the very first result demonstrating the stabilization of sulfur in its metastable state only under confinement at ambient conditions. Sulfur content as high as 75% could be loaded in the NaY-PAni assembly. However, extremely stable battery performance is obtained for slightly lower S-loadings. At sulfur content of 65%, capacity of around 600 mAh g^-1 is obtained at the end of 200 cycles.