A facile Ball-Milling preparation strategy of Nitrogen-Doped carbon coated Na4Fe3(PO4)2P2O7 Nano-Flakes with superior sodium ion storage performance

• Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) nano-flakes were synthesized by solid-phase reaction. • Nano-flakes shorten the Na + migration path and accelerate the diffusion of Na + . • The formation of uniform nano-flakes benefits from the control of heating rate. • Nitrogen-doped carbon coated Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) nano-flakes demonstrate excellent electrochemical performance. Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) is expected to be a promising cathode material for sodium ion batteries (SIBs) applied to large-scale energy storage systems owing to its abundant resource and low cost of the raw materials. However, the currently reported methods for preparing NFPP either cannot be applied to mass-production on a large scale because of their high energy consumption, or result in the production of NFPP materials that have poor electrochemical performance. Herein, we prepared a hierarchical nitrogen-carbon-coated NFPP nanoflake by a facile and easily scalable solid-phase ball milling method, in which oleic acid as the surfactant and carbon source. The formation mechanism of this hierarchical open structure constructed by uniform nano-flakes was investigated by a heating-rate controlled experiment, which indicated that heating rates play an important role in morphology and structure of the final products. When used as a cathode material, the present NFPP nano-flakes composites are able to operate in a wide temperature range (−20 ∼ 50 °C) and, can provide specific capacity of 129 mAh/g at 0.1C, with excellent cycling stability (81 % capacity retention at 10C after 1500 cycles) at 25 °C. Furthermore, the NFPP cathode is coupled with the MoS 2 anode (MoS 2 /rGO) to assemble the sodium ion full battery, it exhibits outstanding rate/cycling performances. The present work provides a method of preparing NFPP electrode materials with good performance for s SIBs, which can be easily amplified production.