Confining selenium in nitrogen-containing hierarchical porous carbon for high-rate rechargeable lithium–selenium batteries

Abstract

A novel nitrogen-containing hierarchical porous carbon (NCHPC) was prepared by a simple template process and chemical activation and a selenium/carbon composite based on NCHPC was synthesized for lithium–selenium batteries by a melt-diffusion method. The Se–NCHPC composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements. It is found that the elemental selenium was dispersed inside the hierarchical pores of NCHPC. It is demonstrated from cyclic voltammetry (CV) and galvanostatic discharge–charge processes that the Se–NCHPC composite has a large reversible capacity and high rate performance as cathode materials. The Se–NCHPC composite with a selenium content of 56.2 wt% displays an initial discharge capacity of 435 mA h g−1 and a reversible discharge capacity of 305 mA h g−1 after 60 cycles at a 2 C charge–discharge rate. In particular, the Se–NCHPC composite presents a long electrochemical stability at a high rate of 5 C. The results reveal that the electrochemical reaction constrained inside the interconnected macro/meso/micropores of NCHPC would be the dominant factor for the enhancement of the high rate performance of the selenium cathode, and the nitrogen-containing hierarchical porous carbon network would be a promising carbon matrix structure for lithium–selenium batteries.