Cost-effective sodium-ion batteries using a Na_0.67Mn_0.9Ni_0.1O₂ cathode and lavender-flower-waste-derived hard carbon with a comparative presodiation approach

The development of cost-effective, high-performance sodium-ion batteries (SIBs) is essential for large-scale energy storage systems. In this study, low-cost SIBs are fabricated using P2-type Na_0.67Mn_0.9Ni_0.1O₂ as the cathode and hard carbon (HC) derived from lavender flower waste as the anode. The synthesis of both electrode materials from widely accessible precursors ensures scalability and environmental sustainability. To address the sodium deficiency of HC, three different presodiation strategies—electrochemical, chemical, and direct contact—are systematically investigated, and the electrochemical performances of the full cells are compared. This evaluation reveals significant variations in the initial capacity, capacity retention, Coulombic efficiency, and rate performance. Although the direct-contact method delivers the highest initial capacity, electrochemical presodiation delivers superior long-term cycling stability and enhanced energy density. This comprehensive comparison of the electrochemical performance emphasizes the vital role of presodiation in enhancing the full-cell efficiency, while highlighting the potential methods for developing cost-effective and sustainable SIBs.