Molecular Templating and Boron-Doping Guides Twisted Microcrystalline Formation in Coal-Derived Hard Carbons for...

The development of hard carbon (HC) anodes with the low-cost coal precursor for sodium-ion batteries (SIBs) is usually limited by sluggish kinetics and low capacity. The main reason is that the abundant aromatic frameworks in coal produce over-stacked microcrystalline during high-temperature carbonization, restricting sodium ion intercalation and diffusion. Here, we propose a molecular templating and doping strategy using phenylboronic acid (PhB) to regulate the microcrystalline structure of coal-derived HCs. The π-π interaction between PhB and coal aromatic suppresses the excessive stacking, while boron (B) doping perturbs charge distribution and introduces intra-domain defects. These effects lead to the formation of twisted turbostratic domains with an expanded interlayer spacing, enabling high ionic and electronic conductivity for sodium ion storage. The reduced surface electronegativity by B-doping also favors the formation of a stable anion-derived interface. As a result, the optimized HC delivers a high reversible capacity of 321 mAh g^-1 at 50 mA g^-1 and maintains a capacity of 249 mAh g^-1 at the high current density of 2.5 A g^-1. This work demonstrates that molecular templating offers an effective route to balance capacity and reaction kinetics in coal-based HC anodes.