Porous Hard Carbon Derived from Indian Trumpet Flower Seeds as a High-Capacity Sodium-Ion Battery Anode Material

Sodium-ion batteries (SIBs) have garnered significant attention as a promising alternative to lithium-ion batteries (LIBs) owing to their lower cost and abundant availability of natural resources. Hard carbon (HC) is broadly recognized as the most favorable anode material for SIBs because of its superior Na-storage capabilities and economic viability. However, significant challenges persist, such as the limited electrical conductivity, poor cycling stability, and low initial Coulombic efficiency (ICE). In this work, utilizing Indian trumpet flower seeds (ITSs) as a precursor, we successfully developed an innovative HC anode, which delivers a high reversible capacity of 380 mAh g^-1, exceptional rate capability with 65% capacity retention at 1500 mA g^-1, and high ICE of 89.18%. In addition, it exhibits noteworthy cycling stability, maintaining 98% of its stable capacity after 400 cycles. These improved performances are ascribed to the expanded carbon layer spacing and increased formation of closed mesopores, achieved through a simple and efficient synthetic approach incorporating acid treatment and P-induced pore-forming. This work presents a promising anode material precursor and an innovative synthetic strategy for producing advanced HC anodes for SIBs.