Free-Standing Sulfur Cathodes Enabled by a Cationic Polymer for Lean Electrolyte Lithium-Sulfur Batteries

It is well-known that, under lean electrolyte and high sulfur loading conditions, it is challenging to achieve a high discharge platform, discharge capacity, and cycling stability for lithium-sulfur (Li-S) batteries. Here we report a free-standing sulfur cathode that can efficiently adsorb and electrochemically catalyze polysulfides. A cationic polymer, polyquaternium-10 (P10), is adopted as a new binder that produces viscoelastic fibers during casting, facilitates lithium-ion transportation, and electrostatically regulates polysulfides. The cationic polymer promotes the formation of the free-standing cathode with a desirable web-like microstructure. The Li-S battery constructed by the free-standing cathode with sulfur mass loading of 6 mg cm-2 achieves a high initial areal capacity of 7.09 mAh cm-2 (i.e., 344.5 Wh kg-1 and 471.6 Wh l-1) and stable areal capacity of 4.48 mAh cm-2 (i.e., 217.6 Wh kg-1 and 235.8 Wh l-1) during cycling at a low electrolyte/ sulfur ratio of 4 mu L mg-1.

Automated summary

In this study, a free-standing sulfur cathode with efficient polysulfide adsorption and electrochemical catalysis is reported. A cationic polymer binder is used to produce a viscoelastic microstructure, facilitate lithium-ion transportation, and regulate polysulfides electrostatically. The resulting Li-S battery exhibits a high initial areal capacity of 7.09 mAh cm-2 (equivalent to 344.5 Wh kg-1 and 471.6 Wh l-1) and stable areal capacity of 4.48 mAh cm-2 (equivalent to 217.6 Wh kg-1 and 235.8 Wh l-1) during cycling at a low electrolyte/sulfur ratio of 4 mu L mg-1.