Sodium amide as a bifunctional agent: Activating and doping sago starch into porous carbon anodes for sodium-ion batteries

Carbon based materials have been used as anode materials for various rechargeable battery system, including sodium ion battery (SIBs). Although hard carbons are the common anode materials for SIBs, porous carbons can be one of the alternative and prospective anode materials. In this work, we use sago starch as a carbon precursor for N doped porous carbon anodes for sodium ion batteries (SIBs). The N doped porous carbons were prepared by using sodium amide (NaNH 2 ) which plays a bifunctional role (an activating agent as well as a nitrogen doping source). The preparation methods consisted of hydrothermal treatment of sago starch followed by the dry mixing at various NaNH₂-to-hydro-char weight ratios (1:1, 2:1 and 3:1) and finalized with pyrolysis carbonization at 700 °C. The resulting porous carbons exhibit an expanded interlayer spacing, high surface area, hierarchical porous structures and N- containing functional groups. When evaluated as an anode for SIBs, the optimized material which was obtained at 2:1 NaNH 2 to hydro-char ratio (NPC-2), delivers an initial reversible capacity of 283 mAh g⁻¹ and retains 268 mAh g⁻¹ after 300 cycles at current density of 500 mA g −1 for half-cell configurations. Preliminary full-cell studies were conducted by coupling NPC-2 with commercial sodium vanadium phosphate (NVP). The full cell delivers a reversible capacity of 70 mAh g⁻¹ under a current density of 100 mA g⁻¹ after 100 cycles, corresponding to a capacity retention of 58.8%. This work demonstrates that sago starch, combined with NaNH₂ activation, is a low-cost, sustainable, and scalable route to producing nitrogen-doped porous carbons with promising sodium storage properties.