Agar-Derived Slope-Dominated Carbon Anode with Puparium Like Nano-Morphology for Cost-Effective SIBs

The microstructure of hard carbons (HCs) including interlayer distance and lateral ab direction and pore size distribution plays a key role in regulating the sodium ions storage performance. Herein, by employing the gelatinous agar as a model precursor, series P-doping HCs (P-HC-x, x = 1, 2, 3, 4) are facilely prepared in batches via controllably regulating its crosslinking state by phytic acid (PA) at a low carbonization temperature of 750 °C, in which PA plays three roles (acid, flame retardant, and P-doping precursor) in promoting the final structure of P-HC-x. Among those, the puparium like P-HC-2 with expanded carbon interlayer distance of 3.91 Å and shortened lateral ab direction of 9.4 nm delivers a high reversible capacity of 394 mAh g^-1 at 0.1 A g^-1 with high increased slope capacity of 363 mAh g^-1 as well as an ultrafast charge-discharge feature and a superlong cycle life. Pairing with the Na₃V₂(PO₄)₃ cathode, the fabricated sodium-ion full cells exhibit the 132 mAh g^-1 reversible capacity at 0.1 A g^-1, and 86% capacity retention after 100 cycles. This work successfully develops slope-dominated high-performance carbon anode, which will provide new insights for the microstructure regulation and design of other precursor-derivedHCs.