Nitrogen-doped porous hollow carbon sphere-decorated separators for advanced lithium–sulfur batteries

• NHCs are prepared by pyrolysis of a PDA carbon precursor.
• NHC-decorated separator exhibits excellent electrochemical performance.
• NHC-decorated separator would be a promising solution for Li–S batteries.

Lithium–sulfur (Li–S) batteries have a distinct advantage over other rechargeable battery systems since their high specific energy and low cost. However, the diffusion of polysulfides from cathode to anode leads to poor electrochemical stability of Li–S batteries, which is a main factor that restricts their further development. Herein, for the first time we present a separator with nitrogen-doped porous hollow carbon sphere (NHC) coating, with which Li–S cells enormously improve the utilization of active material and enhance excellent electrochemical performance. An initial discharge capacity of 1656 mAh g−1 (0.2 C) and a low fading rate of 0.11% per cycle within 500 cycles (1 C) are achieved, which ascribe to the chemical and physical adsorption properties of porous and nitrogen-doped NHCs. The NHC-decorated separator is of low cost and can effectively improve energy density of Li–S cells, exhibiting potential for further development of Li–S batteries.

Nitrogen-doped porous hollow carbon spheres are prepared by pyrolysis of a polydopamine (PDA) carbon precursor on the surface of silicon dioxide (SiO2) temple. After washed with HF, the NHCs are coated onto one side of the separator with a slurry-coated method. With the NHC-decorated separator, an initial discharge capacity of 1656 mAh g−1 (0.2 C) and a low fading rate of 0.11% per cycle within 500 cycles (1 C) are achieved. The excellent results are attributed to the high specific surface area and pore volume of the NHCs which ensure electrolyte infiltration and act as a barrier for polysulfides. Furthermore, the high nitrogen content in NHCs can improve electronic conductivity and enhance interaction between nitrogen atoms and polysulfides.Figure optionsDownload as PowerPoint slide