High-performance lithium sulfur batteries enabled by a synergy between sulfur and carbon nanotubes

The urgent demand on high performance energy storage devices makes lithium sulfur batteries with a high energy density up to 2600 Wh kg(-1) extremely attractive. However, the low capacity reversibility and poor rate capability still pose a significant hurdle on their real-world applications. Here, a freestanding thin-film composite containing sulfurized polyacrylonitrile with conductive backbone of carbon nanotubes has been fabricated by an electrospinning method followed by vulcanization, and employed as the binder-free cathode for lithium sulfur batteries without any aid of current collectors. A synergic effect from sulfur and carbon nanotubes, when co-spun together, has been discovered on promoting the electrochemical performance of the cathodes by simultaneously creating material porosity and conductive pathway. The optimized composite fibers made from a ternary precursor solution containing 20% carbon nanotubes present the best performance, delivering a high initial discharge capacity of 1610 mAh g(-1) at 0.2C and outstanding cycle stability of 1106 mAh g(-1) at 1C over 500 cycles. It is anticipated that the porous composite nanofibers and the multivariant fabrication methodology reported here can be extended to more energy storage applications, particularly for flexible lithium sulfur batteries.