A high-performance carbon with sulfur doped between interlayers and its sodium storage mechanism as anode material for sodium ion batteries

Abstract

A type of sulfur-doped carbon (SC) was synthetized by pyrolyzing the freeze-dried gel of agarose and sulfur powder as anode material for sodium ion batteries (SIBs), and its sodium-storage mechanism was assayed by structure and electrochemical characterizations. The most sulfur atoms were doped between (002) interlayers of carbon matrix probably because of the perfect structure of agarose sourced carbon, as the (002) interplanar spacing has increased from 0.323 nm to 0.393 nm, which benefits the faster diffusion of Na+-ions inside carbon lattice. The optimized SC material exhibited an initial discharge capacity more than 420 mAh g−1 at 100 mA g−1. When cycled at various current densities from 0.1, 0.2, 0.3, 0.5, 1.0, 2.0–3.0 A g−1, the reversible specific capacity changed from 331, 293, 273, 245, 207, 152 to 110 mAh g−1 respectively, which displayed high rate performance. When cycled to the 1000th time at 500 mA g−1 and 1000 mA g−1, the capacity retention was still kept at 91.6% and 91.8% based on the stable reversible capacity during the charge/discharge processes, respectively. The advantage of stable cycling performance makes the low cost S-doped carbon derived from natural seaweed be a promising candidate as anode material for rechargeable SIB.