Selenium-Doped Sulfurized Polyacrylonitrile Coatings as the Cathode for Lithium–Sulfur Battery

Sulfurized poly(acrylonitrile) (SPAN) is a promising cathode for lithium–sulfur (Li–S) batteries due to its solid–solid conversion mechanism that avoids the shuttle effect. However, most reported SPAN cathodes have low areal loadings (<2 mg cm –2 ), insufficient for commercial requirements. Here, a high-loading selenium-doped SPAN (Se 0.1 SPAN) ultrathick electrode is prepared via a simple freeze-drying method, avoiding cracking issues associated with thermal drying. The sublimation of ice crystals creates microcracks that enhance electrolyte infiltration and Li + transport, improving thick-electrode reaction kinetics. At 5.8 mg cm –2, the cathode delivers 719 mAh g –1 at 0.2 C with 89.1% active material utilization, along with excellent rate capability and cycling stability. Under ultrahigh loading (17.0 mg cm –2 ) and lean-electrolyte conditions, it maintains outstanding performance, achieving areal capacity far exceeding that of commercial Li-ion batteries. This work offers a practical strategy for constructing high-energy Li–S batteries.