Long‐Life Room‐Temperature Sodium–Sulfur Batteries by Virtue of Transition‐Metal‐Nanocluster–Sulfur Interactions

Abstract

Room-temperature sodium-sulfur (RT-Na/S) batteries hold significant promise for large-scale application because of low cost of both sodium and sulfur. However, the dissolution of polysulfides into the electrolyte limits practical application. Now, the design and testing of a new class of sulfur hosts as transition-metal (Fe, Cu, and Ni) nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres (S@M-HC) for RT-Na/S batteries is reported. A chemical couple between the metal nanoclusters and sulfur is hypothesized to assist in immobilization of sulfur and to enhance conductivity and activity. S@Fe-HC exhibited an unprecedented reversible capacity of 394 mAh g^-1 despite 1000 cycles at 100 mA g^-1 , together with a rate capability of 220 mAh g^-1 at a high current density of 5 A g^-1 . DFT calculations underscore that these metal nanoclusters serve as electrocatalysts to rapidly reduce Na₂ S₄ into short-chain sulfides and thereby obviate the shuttle effect.