From agaric hydrogel to nitrogen-doped 3D porous carbon for high-performance Li–S batteries

Reproducible massive biochar with low cost has attracted great attentions due to their potential applications in the future environment and energy. In this work, a nitrogen-doped 3D porous agaric carbon (N-AC) with high specific surface area (1568.2 m2 g−1) was fabricated without adding any activator by using the agaric hydrogel as a precursor. And when employed as a sulfur host, the resulted N-AC–sulfur composite electrode with 60 wt% sulfur content illustrates a high reversible capacity of 875 mAh g−1 at 0.2 C (1 C = 1675 mA g−1) over 100 cycles as well as an excellent rate capability of 620 mAh g−1 at 2 C. Such excellent electrochemical performances could attribute to (1) the conductive carbon skeleton of N-AC that provides rapid electron/ion transfer; (2) abundant pores range from micropores to macropores in N-AC that are beneficial to accommodating the active sulfur and polysulfides and (3) the nitrogen dopants that provide polarized sites in chemical binding of polysulfides. In a word, this work provides a compelling avenue to the design of multifunctional sulfur host for advanced Li–S batteries.