Template‐Derived Submicrometric Carbon Spheres for Lithium–Sulfur and Sodium‐Ion Battery Electrodes

Abstract

AbstractHighly microporous submicrometric carbon spheres were synthesized by etching a sol–gel derived silicon oxycarbide (SiOC) material with aqueous hydrofluoric acid solution. The resulting material shows a large total pore volume of 0.63 cm3 g−1 and thus acts as an ideal host for elemental sulfur. Melt impregnation was used to synthesize a carbon–sulfur composite (50:50 wt %) as a cathode for lithium–sulfur batteries. Characterization by electron microscopy clearly showed that the sulfur is homogeneously distributed within the carbon particles. Electrodes prepared from the composite show good cyclic stability at higher specific currents (e.g., at 500 mA g−1); capacities (related to the active material content) as high as 241 mAh g−1 were retained after 100 cycles and coulombic efficiencies quickly reached values close to 100 %. The material was also tested as an anode in sodium‐ion batteries. Compared to the SiOC precursor, the carbon shows significantly improved electrochemical performance. For instance, at a specific current of 100 mA g−1, a capacity as high as 89 mAh g−1 was retained after 100 cycles, whereas SiOC showed a lower capacity of approximately 70 mAh g−1.