Constructing a 700 Wh kg⁻¹-level rechargeable lithium–sulfur pouch cell

Lithium–sulfur (Li–S) batteries are considered as highly promising energy storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg⁻¹. The highest practical energy density of Li–S batteries reported at pouch cell level has exceeded 500 Wh kg⁻¹, which significantly surpasses that of lithium-ion batteries. Herein, a 700 Wh kg⁻¹-level Li–S pouch cell is successfully constructed. The pouch cell is designed at 6 Ah level with high-sulfur-loading cathodes of 7.4 mg_S cm⁻², limited anode excess (50 μm in thickness), and lean electrolyte (electrolyte to sulfur ratio of 1.7 g_electrolyte g_S⁻¹). Accordingly, an ultrahigh specific capacity of 1563 mA h g⁻¹ is achieved with the addition of a redox comediator to afford a practical energy density of 695 Wh kg⁻¹ based on the total mass of all components. The pouch cell can operate stably for three cycles and then failed due to rapidly increased polarization at the second discharge plateau. According to failure analysis, electrolyte exhaustion is suggested as the key limiting factor. This work achieves a significant breakthrough in constructing high-energy-density Li–S batteries and propels the development of Li–S batteries toward practical working conditions.