Intercalating Graphite-Based Na-Ion Battery Anodes with Integrated Magnetite

Graphite is known as the most successful anode material found for Li-ion batteries. However, unfortunately, graphite delivers an ordinary capacity as anode material for the next-generation Na-ion batteries (SIBs) due to difficulties in intercalating larger Na⁺ ions in between the layers of graphene due to incompatible d-spacing. The methodologies investigated in deriving suitable anode structures for SIBs are found to be either less effective, expensive, or rather too complex in most cases. Herein, a simple strategy is introduced to derive suitable anode materials for SIBs through a modified electrochemical exfoliation of graphite. The introduced exfoliation process is able to graft Fe₃O₄ (magnetite) on graphite allowing the structure to expand, supporting a swift intercalation and deintercalation of Na ions. The synthesized magnetite-functionalized graphene nanoplatelets are identified as a well-suited anode material for SIBs, with its efficient intercalation obtained through the expanded interlayer spacing of 3.9 Å and the surface redox pseudocapacitive activity attained through the surface-grafted magnetite. The effectiveness of the synthesized is reflected in the obtained high discharge capacitance of 420 mAh g^-1, with 96% capacitive retention over 1000 cycles. The study opens new opportunities for prospective low-cost anode materials for energy storage applications.