A Sandwich-Structured Na₂Ti₆O₁₃/Reduced Graphene Oxide Composite for Improved Energy Storage in Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have the potential to be a cost-effective and sustainable solution for large-scale energy storage systems (ESSs) due to the abundance of sodium reserves. Na₂Ti₆O₁₃ has been considered as a suitable candidate for use as an anode material in SIBs owing to its environmental friendliness, low cost, and excellent cycling stability. Despite its advantages, Na₂Ti₆O₁₃ has intrinsic limitations such as electrical conductivity. To overcome these obstacles, a sandwich-structured Na₂Ti₆O₁₃/reduced graphene oxide (rGO) composite is synthesized through a liquid-phase exfoliation and restacking method using electrostatic interactions. The Na₂Ti₆O₁₃/rGO composite showed remarkable improvement in both reversible discharge capacity and cycle stability. In comparison to bare Na₂Ti₆O₁₃ with a discharge capacity of 20.1 mAh g⁻¹ after 500 cycles, the Na₂Ti₆O₁₃/rGO1 composite displayed a discharge capacity of 196.5 mAh g⁻¹ at a current density of 0.1 A g⁻¹ and a voltage range of 0.01–2.5 V. Furthermore, the Na₂Ti₆O₁₃/rGO1||Na₃V₂(PO₄)₃ full cell are assembled, discharging an energy density of 251.3 Wh kg⁻¹_anode with a power density of 228.1 W kg⁻¹_anode after 100 cycles in a voltage range of 1.0–4.0 V.