In Situ Formation of Copper-Based Hosts Embedded within 3D N-Doped Hierarchically Porous Carbon Networks for Ultralong Cycle Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg(-1) and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co-doped hierarchically porous graphitic carbon network developed through a freeze-drying method (denoted as 3D Cu@NC-F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li-S batteries. The porous carbon network consisting of 2D cross-linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N-doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC-F network, the in situ grown copper sulfide (CuxS) embedded within CuxS@NC/S-F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the CuxS@NC/S-F composites' electrode exhibits an initial capacity of 1432 mAh g(-1) and maintains 1169 mAh g(-1) after 120 cycles, with a coulombic efficiency of nearly 100%.