3D nanocomposite archiecture constructed by reduced graphene oxide, thermally-treated protein and mesoporous NaTi₂(PO₄)₃ nanocrystals as free-standing electrodes for advanced sodium ion battery

NaTi₂(PO₄)₃ (NTP) with NASICON structure has been regarded as a promising material for sodium-ion batteries (SIBs). However, NTP always exhibits poor cycling stability and rate performance due to slow electronic conductivity. In this work, a free-standing 3D nanocomposite constructed by reduced graphene oxide (rGO), thermally-treated protein (TP) and mesoporous NaTi₂(PO₄)₃ nanocrystals (denoted as MNTP-TP@rGO) is reported. The fabrication includes an electrostatic self-assembly, freeze-drying, mechanical pressing and thermal treatment. In the MNTP-TP@rGO nanocomposite, 3D interconnected carbon network of rGO and TP acts as both a support for the anchored well-distributed MNTP nanocrystals and a current collector. When free-standing MNTP-TP@rGO is used directly as anode in coin-type half-cell, it delivers a high-rate capacity (52.8 mAhg⁻¹ at 50C) and robust cycling stability with the capacity retention of 80% after 1000 cycles at 5C. Furthermore, a full Na-ion battery is constructed using Na₃V₂(PO₄)₃/C (NVP/C) as a cathode and free-standing MNTP-TP@rGO as an anode and it exhibits a high specific capacity (58 mAhg⁻¹ at 1C) and outstanding cycling stability (98% capacity retention over 100 cycles at 1C). Our results suggest great potential of the free-standing electrode of MNTP-TP@rGO composite in high-performance SIBs.