Trace Metal Impurities\nInduce Differences in Lithium–Sulfur\nBatteries

Carbon nanotubes (CNTs) with exceptional conductivity\nhave been\nwidely adopted in lithium–sulfur (Li–S) batteries. While\ntrace metal impurities in CNTs have demonstrated electrocatalytic\nactivity in various catalytic processes, their influence on sulfur\nelectrocatalysis in Li–S batteries has been largely overlooked.\nHerein, we reveal that the trace metal impurities content in CNTs\nsignificantly improves the specific capacity and cycling performance\nof Li–S batteries by analyzing both our own results and previous\nliterature with CNTs as the sulfur hosts. Even under lean electrolyte\nconditions (E/S ratio of 5 μL mg<sub>s</sub><sup>–1</sup>), we demonstrate that a small content of metal impurities in CNTs\n(∼2 wt %) could account for a 14.3% increase in specific capacity\nand a 14.1% increase in capacity retention under a high sulfur loading\nof 3.5 mg cm<sup>–2</sup>. The electron transfer from confined\nmetal catalysts within CNTs leads to electron accumulation at the\ncarbon interface, facilitating electron donation to adsorbed sulfur\nspecies and lowering the energy barrier for Li<sub>2</sub>S formation.