Insights into the Na + Storage Mechanism of Phosphorus‐Functionalized Hard Carbon as Ultrahigh Capacity Anodes

Abstract Hard carbon as a typical anode material for sodium ion batteries has received much attention in terms of its low cost and renewability. Herein, phosphorus‐functionalized hard carbon with a specific “honeycomb briquette” shaped morphology is synthesized via electrospinning technology. When applied as an anode material for Na + storage, it exhibits an impressively high reversible capacity of 393.4 mA h g −1 with the capacity retention up to 98.2% after 100 cycles. According to first‐principle calculation, the ultrahigh capacity of the as‐prepared anode is ascribed to the enhancement of Na‐absorption through formation of PO and PC bonds in graphitic layers when doped with phosphorus. Moreover, the increase of electron density around the Fermi level is found to be mainly caused by O atoms instead of P atoms.