Interface‐Engineered P2‐Type Cathode and Biomass‐Derived Anode for Stable Sodium‐Ion Full Cells

ABSTRACT This work presents a sustainable and high‐performance sodium‐ion full‐cell architecture by combining a core@shell Na 0 . 67 Mn 0 . 5 Fe 0 . 5 O 2 @Al 2 O 3 cathode with a hard carbon anode derived from cherry seed biowaste. The P2‐type cathode material is synthesized via a conventional solid‐state method and coated with Al 2 O 3 using a scalable wet‐chemical route. Structural and surface analyses confirmed the formation of a uniform Al 2 O 3 shell, which enhanced the cathode's electrochemical stability by mitigating Mn 3 ⁺‐induced distortion and suppressing electrolyte side reactions. In parallel, the hard carbon anode is produced from cherry seeds—a low‐cost and abundant byproduct—through high‐temperature pyrolysis, delivering high capacity and excellent cycling performance. Electrochemical evaluation of both electrodes in half‐cell and full‐cell configurations revealed favorable sodium‐ion diffusion, robust structural integrity, and improved interfacial properties. The half‐cell, assembled with Na 0 . 67 Mn 0 . 5 Fe 0 . 5 O 2 @Al 2 O 3 cathode, demonstrated remarkable cycling stability and rate capability within a practical 1.5–3.5 V window, retaining 94.5% capacity after 100 cycles. In situ XRD studies further elucidated the phase transitions and stability of the cathode during cycling. This study demonstrates a sustainable and scalable pathway for sodium‐ion battery development by integrating surface‐engineered cathodes and biomass‐derived anodes.