Ultrahigh rate and high-performance lithium-sulfur batteries with resorcinol-formaldehyde xerogel derived highly porous carbon matrix as sulfur cathode host

Lithium-Sulfur Battery (LSB) is looked upon as a promising energy storage device to be used in high end applications due to their high energy metrics. However, the successful commercialization of LSBs is hauled by limitations of low sulfur utilization, insulating sulfur, and poor cyclic stability. Restricting polysulfide shuttling and improving electrochemical kinetics are important in developing high-performance LSBs. Here, we have resolved these critical problems associated with LSBs even at extreme operating current conditions using highly porous N-doped resorcinol-formaldehyde (RF) carbon xerogel as sulfur host. We developed a RF xerogel-derived highly porous N-doped carbon matrix by two-step carbonization-activation strategy for anchoring polysulfides and accelerating their redox transformation simultaneously. The high amount of N-doping (10%) and graphitic domains, amid the porous amorphous carbon, possess active sites to entrap polysulfides. Besides, they provide pathways for high electron transfer for their electro-catalysis. First principle calculations also establish that the enhanced performance is attributed to high pyrrolic nitrogen content in the porous carbon structure. As a result, the A-N-RFC/S cathode composite exhibits excellent cycling stability, maintaining a specific capacity of 631 mAh g(-1) at 4 C even after 500 cycles, corresponding to an extremely low capacity decay of 0.0017% per cycle with coulombic efficiency of more than 95%. Additionally, the composite material displays astonishing rate performance exhibiting an outstanding discharge capacity of 359 mAh g(-1) even at an ultra-high current rate 20 C. The synthesized material overcomes the two key parameters, cyclic stability and rate performance required for commercial LSBs by suppressing the detrimental polysulfide shuttling.