Evaluation on a 400 Wh kg⁻¹ lithium–sulfur pouch cell

Lithium–sulfur (Li–S) batteries are highly regarded as next-generation energy storage devices due to their ultrahigh theoretical energy density of 2600 Wh kg⁻¹. However, practical high-energy-density Li–S pouch cells suffer from limited cycling lifespan with rapid loss of active materials. Herein, systematic evaluation on a 400 Wh kg⁻¹ Li–S pouch cell is carried out to reveal the working and failure mechanism of Li–S batteries under practical conditions. Electrode morphology, spatial distribution and species analysis of sulfur, and capacity retention of electrodes are respectively evaluated after the first cycle of discharge or charge. Considerable lithium polysulfides are found in electrolyte even at the end of discharge or charge, where the sulfur redox reactions are reversible with high capacity retention. Meanwhile, severe morphology change is identified on lithium metal anode, yet there remains substantial active lithium to support the following cycles. This work not only demonstrates unique behaviors of Li–S batteries under practical conditions, which is essential for promoting the progress of Li–S pouch cells, but also affords a systematic evaluation methodology to guide further investigation on high-energy-density Li–S batteries.