Anode of Anthracite Hard Carbon Hybridized by Phenolic Epoxy Resin toward Enhanced Performance for Sodium-Ion Batteries

Anthracite-based carbon is considered one of the most promising anodes for sodium-ion batteries (SIBs) due to its abundant natural resource and low cost. However, their performance is very poor. In this article, the microstructure of anthracite is hybridized by phenolic epoxy resin. The cross-linking reaction between anthracite and the resin generates hybrid carbon. The structure of anthracite transforms from graphite-like phase to pseudographite phase, accompanied by the increase of interlayer spacing. Due to the formation of oxygen-containing functional groups, abundant defects are generated on the surface and inside. Phenolic epoxy resin generates a microhard carbon structure around anthracite, in which curved and intertwined disordered structure are formed. This can effectively reduce the degree of graphitization of anthracite, promote rearrangement, and inhibit the regular accumulation of carbon layers. The performance of the anthracite anode with 5% resin pyrolyzed at 1200 °C is improved obviously, delivering capacity of 357.7 mAh g–1 at a current density of 50 mA g–1 and excellent capacity retention of 89% after 500 cycles at 500 mA g–1. According to the in situ Raman analysis, it can be seen that Na+ is mainly adsorbed on the defect sites and open pore gaps on the material surface and then inserted in the pseudographitic region. This research proposes an effective strategy to enhance the performance of natural coal carbon material, providing huge opportunity for the commercialization of low-cost anthracite anodes for SIBs.