Scalable and Economic Synthesis of High-Performance Na₃V₂(PO₄)₂F₃ by a Solvothermal–Ball-Milling Method

Abstract

Na3V2(PO4)2F3 has been emerging as one of the most promising cathodes for sodium-ion batteries due to its stable NASICON structure and fast Na+ diffusion. However, present methods for preparation of Na3V2(PO4)2F3 suffer from either high energy consumption or generating poor rate performance. Herein, a cost-effective solvothermal–ball-milling method is proposed to solve the problem. In the solvothermal process, the morphology of Na3V2(PO4)2F3 varies from 0D to 3D with changing pH, in which 3D Na3V2(PO4)2F3 at pH = 3 shows optimal purity due to the fastest growth rate. With Ketjenblack (KB) coating by short-time ball-milling, the Na3V2(PO4)2F3 can be further nanosized with a highly graphited carbon coating layer. The purest Na3V2(PO4)2F3@KB from pH = 3 exhibited an initial capacity of 138 mAh g–1 @ 0.5 C and 122 mAh g–1 @ 40 C. Moreover, ultrahigh dosage over an 80 mmol of V source in one 100 mL Teflon-lined autoclave has been achieved for the first time.