Nitrogen-doped 3-D porous carbon network derived from lotus leaves as interlayer for lithium sulfur batteries

Abstract

Various nitrogen doped 3-D porous carbon networks (PCNs) were prepared by a facile hydrothermal treatment of lotus leaves using urea and dicyandiamide (DCDA) as the nitrogen agent. The un-doped and N-doped PCNs were used as an interlayer for lithium sulfur batteries. The N-doped PCNs prepared by urea exhibited a maximum surface area and broader pore size distribution due to formation of more defects. After 100 charge-discharge cycles the improved discharge capacity and capacity retention were obtained. Surprisingly, a superior rate performance was observed. Under 5 C rate the N-doped interlayers exhibited the higher discharge capacity of 442 mA h g−1 than the undoped interlayers, 293 mA h g−1 and the N-doped interlayer by DCDA, 370 mA h g−1. This was associated with the enhanced lithium ion diffusivity and reduced charge transfer resistance, resulting from the presence of more pyridinic-N and pyrrolic-N and appropriate pore size distribution that enabled to capture more soluble lithium polysulfide.