PIM-1-based carbon-sulfur composites for sodium-sulfur batteries that operate without the shuttle effect

Abstract

Room temperature sodium-sulfur (RT Na-S) batteries have distinct advantages over other next generation batteries because of their use of abundant and inexpensive resources with high theoretical capacities of 1166 and 1675 mA h g(-1), namely for sodium and sulfur. However, problematic side reactions, called the shuttle effect, lead 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 a PIM-1-based carbon-sulfur composite. This sulfur-carbon material was prepared through one-step heat treatment of a mixture of sulfur and PIM-1. The resulting sulfur-carbon composites have characteristics of both similar to 0.5 nm-sized ultra-micropores and covalent bonding in a single material, which fundamentally obstruct the dissolution of polysulfide into the electrolyte. This strategy led to long cycling stability over 250 cycles, with a capacity of 556 mA h g(s)(-1) and a coulombic efficiency of approximately 100%.