Boron-doping and pore architecture synergistic regulating the microstructure in resin-based hard carbon for enhanced sodium storage performance

Hard carbon has emerged as one of the most promising anode materials for sodium-ion batteries (SIBs) due to its favorable electrochemical properties and cost-effectiveness. However, it remains a significant challenge to effectively tailor the microstructure of hard carbon to enhance its sodium storage performance. Herein, Zn(BF 4 ) 2 ·xH 2 O serves as a dopant as well as a pore-creating agent to synergistically modulate the microstructure of resin-derived hard carbon through boron (B) doping and pore architecture, thereby improving its sodium storage properties. The introduction of B atoms effectively substitutes C sites, forming B–C and B–N bonds that provide abundant active sites and expand the interlayer spacing. Meanwhile, Zn(BF 4 ) 2 ·xH 2 O crosslinks with the resin during heating to form ZnO intermediates, which etch the carbon material and generate a large number of open pores. During high-temperature carbonization, some of the open pores are converted into closed pores, which improve the plateau region capacity. The synergistic effect of Zn(BF 4 ) 2 ·xH 2 O simultaneously regulates and enhances both the plateau and slope regions of sodium storage in hard carbon, thereby improving its overall capacity and reaction kinetics. Consequently, the optimized BNHC-1 electrode exhibits a high reversible capacity of 375.8 mAh g −1 at 30 mA g −1 and a remarkable rate capability with 303.5 mAh g −1 retained at 2000 mA g −1 . This work offers a practical and effective strategy for constructing high-performance hard carbon anodes for next-generation SIBs.