Turning Soluble Polysulfide Intermediates Back into Solid State by a Molecule Binder in Li-S Batteries.

The shuttle effect of dissolved polysulfides produced during the operation of lithium-sulfur batteries is the most serious and fundamental problem among many challenges. We propose a strategy via in situ formation of a functionalized molecule with a dual-terminal coupling function to bind the dissolved polysulfide intermediates, thus turning them back into solid-state organopolysulfide complexes by molecule binding, and then the polysulfides can be pinned on the cathode firmly. The dual-terminal coupling functional molecule binder (MB), which is formed in situ by reaction between quinhydrone (QH) and lithium, can not only bind polysulfides by reversible chemical coordination but also promote the conversion of polysulfides during cycling synchronously. In theory, with the dual-terminal coupling function, MB can bind polysulfide intermediates to copolymerize them, forming -[MB-Li2Sn]- that has faster reaction activity and redox conversion kinetics in comparison with simple Li2Sn. With the MB, the Li-S battery exhibits a large initial capacity of 1347 mAh g-1 at 0.1 C. The remaining capacity of 963 mAh g-1 at 1 C shows no obvious decay for more than 400 cycles, and the retention of the first 300 cycles can reach 96.9%, in particular. This study delivers an alternative approach to resolving the shuttle effect and achieving excellent Li-S battery performance, with the potential significance going way beyond battery systems.