Understanding the carbonization-controlled microstructure regulation in coal-based hard carbon to strengthen sodium...

Hard carbon materials have emerged as promising anode materials for sodium-ion batteries (SIBs) due to their abundant resources, low cost, and tunable pore structures. However, the relationship between preparation conditions, material structure, and electrochemical performance remains unclear. In this study, coal-based hard carbon was synthesized via a one-step carbonization method. By characterizing the structure of hard carbons derived from different carbonization temperatures and analyzing their electrochemical performance, we have established the correlation between carbonization temperature, graphite microcrystal structure, and sodium storage behavior. The as-prepared sample at a carbonization temperature of 900 °C showed abundant graphite microcrystals with a layer spacing of 0.383 nm, and CO surface functional groups. It showed a high reversible capacity of 277.7 mA h g^-1, a long plateau discharge capacity of 111.76 mA h g^-1, and an excellent rate capacity retention of 76% at 1 A g^-1. This work offers guidance for the production of coal-based hard carbon materials, and provides the possibility of high energy density SIBs.