Mn-Assisted Microstructural Reconstruction and Nitrogen Doping Engineering of Graphitic Domains and Pore Architecture for Superior Sodium Storage in Hard Carbon

Sodium-ion batteries (SIBs) are promising for large-scale energy storage, yet their performance is limited by intrinsic trade-offs in hard carbon (HC) anodes among capacity, rate capability, cycling stability, and initial coulombic efficiency (ICE). Conventional strategies often enhance interlayer spacing or defect density at the expense of ICE due to uncontrolled defect generation and side reactions. Herein, we propose a novel transient Mn-assisted microstructural reconstruction strategy to break the intrinsic coupling between key structural parameters in HC. Using a rationally designed Mn- and ammonium-based precursor, we orchestrate concurrent Mn species volatilization and in situ gas release during pyrolysis to independently tailor the HC architecture. The transient presence of Mn-containing species promotes graphitic-domain reconstruction, optimizes graphitic microcrystallites, and regulates pore evolution. The vacancy creation and gas etching cobuild a hierarchical pore network that prevents pore blockage and offers unobstructed ion pathways. Simultaneously, this process enriches active pyridinic nitrogen for accelerated reaction kinetics. The synergistic combination of Mn-assisted microstructural reconstruction and nitrogen doping endow the resulting HC anode with a high discharge specific capacity of 337.46 mAh g –1 at 0.1 C, outstanding rate capability (209.17 mAh g –1 at 5 C), a high initial coulombic efficiency of 90.91%, and 82.24% capacity retention over 2000 cycles. Further, the full-cell demonstrations confirm practical viability of this strategy. This work offers a generalizable route to decouple and independently tune critical structural parameters of high-performance HC anodes.