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 Na0.67Mn0.5Fe0.5O2@Al2O3 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 Al2O3 using a scalable wet-chemical route. Structural and surface analyses confirmed the formation of a uniform Al2O3 shell, which enhanced the cathode's electrochemical stability by mitigating Mn3⁺-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 Na0.67Mn0.5Fe0.5O2@Al2O3 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.