Defect-Engineered Vertically Aligned Carbon Nanotube Cathodes with High Sulfur Loading for High-Energy Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries hold exceptional promise due to their high gravimetric energy density and affordability, yet their practicality is limited by the poor conductivity of sulfur, polysulfide shuttling between the electrodes, and volume expansion. Conventional sulfur cathodes demand excessive carbon additives, and the fabrication of thick electrodes remains challenging, both of which dilute the active sulfur content and diminish the attainable energy density. To overcome this disadvantage, we introduce a ultrathick three-dimensional (3D) cathode architecture comprising vertically aligned carbon nanotubes (CNTs), directly grown via chemical vapor deposition (CVD), and functionalized by filling the hollow CNTs with sulfur via infusion (S@CNT). The engineered cathode is additionally subjected to reactive ion etching (RIE) to optimize the surface chemistry for robust polysulfide a…