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 μL mg–1.