Design and interface optimization of a sandwich-structured cathode for lithium-sulfur batteries

The high-energy and low-cost lithium-sulfur (Li-S) battery is regarded as a new generation energy-storage device. However, the Li-S battery mostly suffers from low electronic conductivity and poor cycle capability. This study reports on a novel sandwich-structured cathode with optimized electrode architecture and interface design of the current collector (named as M-S-LTO) made by a facile layer-by-layer slurry coating process. The new integrated electrode is composed of a micro-cracked current collector (MCC) based on multi-wall carbon nanotubes, a middle layer of sulfur/carbon material and an upper current collector&interlayer (UCC&I) based on multi-wall carbon nanotubes and Li4Ti5O12 nanospheres. The M-S-LTO cathode produces a better electrochemical performance because of its improved internal electrical and ionic conductivity, stable structure and mitigation of shuttle effect, in contrast to the sulfur electrode with either an MCC (M-S cathode) or a smooth aluminum foil current collector (S cathode). At a current density of 0.2 C, the Li-S battery with the M-S-LTO cathode delivers a high initial capacity of 1248.6 mAh g−1 and retains a reversible capacity of 960.3 mAh g−1 after 200 cycles. Even at 1 C, its capacity can reach 773.4 mAh g−1 after 200 cycles. The battery with the M-S-LTO cathode shows a higher cycle performance than most of other reported cells based on the interlayer design with a comparable sulfur loading. With the enhanced electrochemical performance, the new cathode offers a promising avenue to fabricate high-performance Li-S batteries.