An eco-friendly Na-ion battery utilizing biowaste-derived carbon and birnessite with enhanced high voltage reaction

Abstract

Trigonal birnessite (Na0.5MnO2·0.7H2O) with quasi-hexagonal-stacked particles is synthesized by a simple procedure. The MnO6 layers are expanded (ca. 7.1 Å as confirmed by HRTEM) by sodium ion and water molecules permitting the cyclability of the cathode up to 4.4 V without anionic redox effect. This particular phase exhibits sodium storage performance with 181.2 mA h g−1 reversible capacity, high Coulombic efficiency (99.8%), good rate performance (20–640 mA g−1), and 80% capacity retention over 200 cycles. X-ray adsorption near-edge structure (XANES) spectra at Mn-k edge confirmed that the main redox component is Mn3+/Mn4+. An environmental-friendly Na-ion full cell is assembled with this cathode and biowaste-derived carbon (obtained from trash of lemon peels) anode and provided ∼ 330 Wh kg−1 energy density (at the material's level) which is preserved at ∼71% over 200 cycles. Manganese, sodium, and carbon are cheap and eco-friendly materials for practical energy storage eagerly sought after in the industry.