Creating Effective Nanoreactors on Carbon Nanotubes with Mechanochemical Treatments for High-Areal-Capacity Sulfur Cathodes and Lithium Anodes

Abstract

Li-S batteries can potentially deliver high energy density and power, but polysulfide shuttle and lithium dendrite formations on Li metal anode have been the major hurdle. The polysulfide shuttle becomes severe particularly when the areal loading of the active material (sulfur) is increased to deliver the high energy density and the charge/discharge current density is raised to deliver high power. This study reports a novel mechanochemical method to create trenches on the surface of carbon nanotubes (CNTs) in free-standing 3D porous CNT sponges. Unique spiral trenches are created by pressures during the chemical treatment process, providing polysulfide-philic surfaces for cathode and lithiophilic surfaces for anode. The Li-S cells made from manufacturing-friendly sulfur-sandwiched cathodes and lithium-infused anodes using the mechanochemically treated electrodes exhibit a strikingly high areal capacity as high as 13.3 mAh cm(-2), which is only marginally reduced even with a tenfold increase in current density (16 mA cm(-2)), demonstrating both high cell-level energy density and power. The outstanding performance can be attributed to the significantly improved reaction kinetics and lowered overpotentials coming from the reduced interfacial resistance and charge transfer resistance at both cathodes and anodes. The trench-wall CNT sponge simultaneously tackles the most critical problems on both the cathodes and anodes of Li-S batteries, and this method can be utilized in designing new electrode materials for energy storage and beyond.