Bifunctional separator as a polysulfide mediator for highly stable Li–S batteries

Abstract

CitationBifunctional separator as a polysulfide mediator for highly stable Li-S batteries 2016 J. Graphical Abstract ABSTRACTThe shuttling process involving lithium polysulfides is one of the major factors responsible for the degradation in capacity of lithium-sulfur batteries (LSBs). Herein, we demonstrate a novel and simple strategy-using a bifunctional separator, prepared by spraying poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on pristine separator-to obtain long-cycle LSBs. The negatively charged SO 3 -groups present in PSS act as an electrostatic shield for soluble lithium polysulfides through mutual coulombic repulsion, whereas PEDOT provides chemical interactions with insoluble polysulfides (Li 2 S, Li 2 S 2 ). The dual shielding effect can provide an efficient protection from the shuttling phenomenon by confining lithium polysulfides to the cathode side of the battery. Moreover, coating with PEDOT:PSS transforms the surface of the separator from hydrophobic to hydrophilic, thereby improving the electrochemical performance. We observed an ultralow decay of 0.0364% per cycle when we ran the battery for 1000 cycles at 0.25 C-far superior to that of the pristine separator and one of the lowest recorded values reported at a low current density. We examined the versatility of our separator by preparing a flexible battery that functioned well under various stress conditions; it displayed flawless performance. Accordingly, this economical and simple strategy appears to be an ideal platform for commercialization of LSBs.

Mechanistic understanding of the role separators playing in advanced lithium‐sulfur batteries

“…To maximize the inhibition effect of the separator on polysulfide migration, several materials have been developed with the combination of ion‐trap, charge‐shield, and ion‐sieve effects . Huang et al prepared a GO‐coated Celgard separator.…”

“…Besides, the capacity decay rate is reduced from 0.49% to 0.23% per cycle during 100 cycles at 0.1 C , suggesting good suppression of the polysulfide shuttle effect. Abbas et al prepared a poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) coated Celgard separator, in which the large amount of sulfonate groups in PSS effectively suppresses the shuttle effect of the negatively charged polysulfide molecules through electrostatic repulsion, while the PEDOT provides strong chemical interactions with polysulfides. The batteries incorporating this PEDOT/PPS modified separator exhibit a discharge capacity of 985 mAh g −1 with a capacity decay rate of 0.0364% per cycle during 1000 cycles at 0.25 C , superior to those with commercial separators (981 mAh g −1 , 0.0932%).…”

Recent advances on flexible electrodes for Na-ion batteries and Li–S batteries

“…Table 6 depicts the working potential range, capacity, and cycling stability of recently reported various kinds of Li-S batteries with flexible cathode materials [57, . Table 7 shows the working potential range, capacity, cycling stability, lighting LED at bent state, and cycling stability at bent state of recently reported several types of flexible Li-S batteries [57,[159][160][161][162][163][164][165][166][167][168][169][170][171][172][173][174][209][210][211] . Foldable Li-S battery can be fabricated by impregnation of the active materials into the super-elastic carbon-nanotube current-collector film in a checkerboard pattern.…”

Multifunctional Separator with Porous Carbon/Multi‐Walled Carbon Nanotube Coating for Advanced Lithium−Sulfur Batteries

“…In a battery system, separator plays an important role in offering ion transport pathway and preventing electrons from passing through anode to cathode, the separator modification is an effective approach and receives ever increasing attention. The additives, such as conductive polymers, carbon materials like porous carbon, CNTs, graphene, and functionalized graphene, have been used to modify the separator. In order to strengthen the adsorption capacity of polysulfide, metal oxides as another strategy for modifying the separator.…”