Enhancing the electrochemical performances of a tellurium-based cathode for a high-volumetric capacity Li battery via a high-energy ball mill with sulfur edge-functionalized carbon

Tellurium (Te) is a promising material for large-scale energy storage systems since it has the highest electrical conductivity among chalcogen-based cathodes, including sulfur and selenium, and a high volumetric capacity. In this work, we introduce a new compositing method for Te and carbon using a high-energy ball mill (HEBM). In particular, when functionalizing the edges of carbon with a small amount of sulfur (S), the spontaneous impregnation of nanoscale Te particles into carbon is facilitated. To study the mechanism of effective impregnation, three types of chalcogen/carbon cathodes are prepared by the HEBM method: (i) sulfur/carbon (S/C), (ii) tellurium/C (Te/C), and (iii) Te/sulfur edge-functionalized C (Te/Sef-C). Among these, Te/Sef-C shows the highest average volumetric capacity (2275 mAh cm(-3)) and the smallest capacity decrement (similar to 5.7 mAh cm(-3) per cycle), with a high Coulombic efficiency of 99.1% during 250 cycles. This enhanced performance of Te/Sef-C can be attributed to a protective self-coated carbon surface layer formed by spontaneous impregnation and growth of Te nanorods surrounded with Sef-C, which improves the electrical/ionic conductivities and reduces the direct exposure of the active materials to the electrolyte.