Strongly bonded CFx@S composite assisting the long-cycle stability of Li-S battery

Abstract

Lithium‑sulfur battery (LSB) has drawn extensive concentration for its high energy density. Nevertheless, the “shuttle effect” of polysulfides leads to inferior sulfur utilization and short service life. Herein, CFx@S composites with a strongly bonded interface of S and CFx have been prepared by a simple solvent evaporation method. The research shows that CFx in the composites will be preferentially discharged to form F-doped carbon (F@C) conductive network and LiF, which improve the electronic and ionic conductivities of electrodes, separately. Numerous polar sites on F@C cooperate with the polar LiF to adsorb polysulfides effectively and then inhibit the “shuttle effect”. The robust F@C conductive network and the SEI film enhanced by LiF can work together to relieve the volumetric dilatation of S in the charge/discharge cycles. Profiting by the above-mentioned merits, even the as-prepared 10-CFx@S composite loads a sulfur content as high as 87.6 %, it manifests an excellent rate capability and stable cycling performance. Under a high current of 1600 mAh g−1, 10-CFx@S delivered a high capacity of 573 mAh g−1 in the initial discharge, and it remained as 334 mAh g−1 after 800 cycles with an average capacity decay of 0.052 % per cycle. This research supplies an easy and feasible approach to promote the performances of LSB.