Asymmetric self-supporting hybrid fluorinated carbon nanotubes/carbon nanotubes sponge electrode for high-performance lithium-polysulfide battery

Abstract

Lithium-polysulfide (Li-polysulfide) battery has been considered as a developed energy storage device of the conventional lithium-sulfur battery with efficient active material utilization and good reaction kinetics. However, the weak interaction between soluble polysulfide and carbonaceous electrode is unable to restrict the soluble polysulfide shuttle effect, leading to the short cycling life. Herein, we innovatively design an asymmetric self-supporting hybrid sponge electrode whose one side is covered by deeply fluorinated carbon nanotubes (F-CNTs, F/C ratio of 0.88) with the appropriate thickness of ∼0.5 μm and the other side is kept bare as the current collector for the high-performance Li-polysulfide battery. The carbon nanotubes sponges (CSP) provides enough space for a high sulfur loading, three-dimensional net structure for fast ions diffusion and connective electrical conductive networks for electrons transfer. The F-CNTs layer shows a strong affinity to soluble polysulfide according to first-principles calculations, which restrains the diffusion of soluble polysulfide from CSP to anode and suppress the shuttle effect significantly. As a result, a high specific capacity of 1344 mAh g−1 at 0.2 C, an excellent rate capability of 780.9 mAh g−1 at 2 C and a great cycling stability for 400 cycles with ∼0.11% capacity decay per cycle have been achieved at the sulfur loading of 2.55 mg cm−2. Particularly, at a high sulfur loading of 5.1 mg cm−2, the hybrid electrode even shows a reversible capacity of 868.9 mAh g−1 after 100 cycles at 0.1 C.