Pre-crosslinking enables a promising cyclodextrin-derived carbon anode with large plateau capacity for sodium ion batteries

Cyclodextrin, which has the advantages of being resource-rich, low cost, eco-friendly, high purity and good stability, is a potential precursor to prepare hard carbons for sodium ion batteries (SIBs), but is rarely explored so far. In this work, a simple and commercializable pre-crosslinking strategy was developed to modulate the local structure of cyclodextrin-derived carbons, because the direct carbonization of cyclodextrin leads to a limited capacity of 154.7 mA h g−1. The original cyclic monomer structure of cyclodextrin is transformed into a three-dimensional cross-linked structure via carbonyl groups as binding sites. The cross-linking reaction tends to produce more sp3-hybrid carbon, which finally results in more curved and shorter carbon layers as well as much more closed pores. Thus, the best sample obtained with a thirty-minute pre-crosslinking treatment delivers an improved reversible specific capacity of 332.5 mA h g−1 at a current density of 30 mA g−1 with an initial Coulombic efficiency of 83.4%, where the low-voltage plateau region (230.1 mA h g−1) contributes up to 70% of the total capacity. To the best of our knowledge, this work offers a tentative exploration of cyclodextrin-derived carbons for the first time, which possibly opens up the investigation of this new kind of carbon anode.