Construction of Soft Base Tongs on Separator to Grasp Polysulfides from Shuttling in Lithium-Sulfur Batteries.

Rechargeable lithium-sulfur batteries, which use sulfur as the cathode material, promise great potentials to be the next-generation high-energy system. However, higher-order lithium polysulfides, Li2 Sx (x = 4, 6, and 8), regardless of in charge or in discharge, always form first, dissolve subsequently in the electrolyte, and shuttle to the cathode and the anode, which is called "shuttle effect." The polysulfides shuttle effect leads to heavy loss of the active-sulfur materials. Literature works mostly "cover or fill" the pores to block polysulfides from shuttling, which also hinder the lithium ion transfer. Here a protocol is invented to grasp polysulfides based on the "soft and hard acid-base" theory. Tertiary amine layer (TAL) polymerized on a polypropylene separator selectively coordinates with the dissolved high-order Li2 Sx in the cathode. Meanwhile, the transportation of lithium cations is not interrupted because of enough pores left for their transportation. After 400 cycles of charge/discharge at 0.5C, the TAL modified separator battery still possesses a capacity of 865 mAh g-1 , which is among the best of the state-of-the-art performances of lithium-sulfur batteries. The flexible "polysulfides tongs" construction method paves a new way for Li-S batteries to reach desired performances with less worry about polysulfides shuttle.