N/O Co‐Doped Hard Carbon Derived from Cocklebur Fruit for Sodium‐Ion Storage

Abstract Hard carbon is one of the most promising anode materials for sodium‐ion batteries (SIBs). However, it still faces the obstacle of low reversible capacity. Modifying the carbon skeleton with heteroatoms is an effective method to improve the electrochemical properties of carbon electrodes. Herein, cocklebur fruit, a plant which is rich in natural alkaloids, is selected as the precursor to prepare N/O co‐doped hard carbon. The obtained sample pyrolyzed at 1100 °C (H1100) can exhibit 366.07 mAh g −1 specific discharge capacity and 69.08 % initial coulombic efficiency. The balance between the suitable configuration of N/O groups and graphitization forms a carbon material with a high sodium‐ion storage capability. The storage mechanism is analyzed by cyclic voltammetry (CV), differential capacity (dQ/dV), galvanostatic intermittent titration technique (GITT), and ex‐situ Raman. The results show that the sodium ions are first adsorbed on defect sites, then filled with micropores and embedded in graphite sheets.