Elastic three-dimensional Fe-doped polypyrrole aerogel current collector for high-loading and high-energy-density lithium-sulfur batteries

Development of high-loading and high-energy-density lithium-sulfur (Li-S) batteries has aroused increasing research interests recently. However, the performance of a conventional two-dimensional Al foil current collector is limited by its smooth/nonporous surface and poor flexibility, which is unfavorable for the achievement of high sulfur loading and sufficient polysulfide adsorption. Hence, a three-dimensional porous Fe-doped polypyrrole aerogel (FPA) is developed by a simple and scalable strategy combing the solution reaction with the freeze-drying technique, aiming at acting as the current collector of cathode to address these issues in Li-S batteries. This FPA possesses a conductive porous network structure with high elasticity and abundant Fe dopants , which can not only buffer the large volume change of sulfur and ensure fast ion/electron transfer, but also effectively anchor the polysulfides and lower the negative polarization effect during cycling. As a result, the FPA@S cathode delivers a high initial capacity of 1196.7 mAh g −1 at 0.2 C and a retained capacity of 829.5 mAh g −1 after 200 cycles, with stabilized Coulombic efficiency and excellent rate performance. This FPA@S cathode also achieves a high cell-level gravimetric energy density of 199.7 Wh kg cell −1 even under a high sulfur-loading (8.57 mg cm −2 ) and low electrolyte/sulfur ratio (6 mL g −1 ), demonstrating its practical potential in future advanced high-energy battery systems.