PIM-1-based carbon-sulfur composites for sodium-sulfur batteries that operate without shuttle effect
Room temperature sodium-sulfur (RT Na-S) batteries have distinct advantages over other next generation batteries because of its use of abundant and inexpensive resources with high theoretical capacity of 1166 and 1675 mA h g-1, namely sodium and sulfur. However, problematic side reaction, called shuttle effect, leads to low coulombic efficiency during cycling. Here, we propose a new strategy to fundamentally suppress the shuttle phenomenon by combining two widely used concepts, covalent bonds and physical confinement, through the preparation of PIM-1-based carbon-sulfur composite. This sulfur-carbon material was prepared through one-step heat treatment of the mixture of sulfur and PIM-1. The resulted sulfur-carbon composites have characteristics of both ~0.5-nm-sized ultra-micropores and covalent bonding in a single material, which fundamentally obstruct the dissolution of polysulfide into electrolyte. This strategy led to long cycling stability over 250 cycles, with a capacity of 556 mA h gs-1 and a coulombic efficiency of approximately 100%.