Dually Decorated Na₃V₂(PO₄)₂F₃ by Carbon and 3D Graphene as Cathode Material for Sodium‐Ion Batteries with High Energy and Power Densities

Abstract

The dually decorated Na 3 V 2 (PO 4) 2 F 3 by in-situ formed carbon and three-dimensional graphene (NVPF/C@3DG) is prepared via two hydrothermal steps and a high-temperature calcination. Benefiting from the high electronic conductivity of carbon and 3DG, high surface area and the resulted high diffusion coefficients of Na + , NVPF/C@3DG displays superior electrochemical performance to the control NVPF/C. Between 2.5 and 4.5 V (vs. Na + /Na), NVPF/C@3DG presents the initial discharge capacity of 123.6 mAh g À 1 at 0.2 C (25.6 mA g À 1) and capacity retention of 92.1 % after 60 cycles, while NVPF/C shows initial discharge capacity of 119 mAh g À 1 and capacity retention of 84.1 % under the identical test conditions. Even at 15 C, the initial discharge capacity and capacity retention after 1000 cycles of NVPF/C@3DG are as high as 91.2 mAh g À 1 and 82.9 %, respectively, much better than the initial discharge capacity of 71.2 mAh g À 1 and the corresponding capacity retention of 76.4 % for NVPF/C, respectively.

Realizing outstanding electrochemical performance with Na3V2(PO4)2F3 modified with an ionic liquid for sodium-ion batteries

“…2e ) reveals that the pore diameter of NVPF-CNB-30 is distributed around 2–35 nm, and it has mesoporous structure. 61 The distribution of mesopores could contribute to inhibiting the agglomeration of the material. 62 The specific surface area calculated according to the Brunauer–Emmett–Teller (BET) model for NVPF-CNB-30 is 45 m 2 g −1 .…”

Enhancing the performance of NaVPO4F cathode materials for sodium-ion batteries through graphite incorporation and polyethylene glycol 6000 modification

“…Among these components, graphite, due to its cost-effectiveness, serves as an economical conductive carbon material, leading to an enhancement in the electrochemical performance of NVPF. The increased conductivity facilitates more rapid and efficient electron transport; 7,27 PEG6K is a general term for ethylene glycol polymers containing a large number of hydroxyl groups, NVPF and graphite composites are combined with hydroxyl groups with an adhesive function in PEG6K under the incorporation of PEG6K, so that the graphite sheet layer is more firmly attached to the NVPF sample, thereby enhancing the coordination strength between Na + ions and other molecules within the raw material. It also inhibits volatilization, while the presence of -OH functional groups improves the wettability of sodium metal and restricts dendrite growth.…”

Phase Formation in NaH2PO4–VOSO4–NaF–H2O System and Rapid Synthesis of Na3V2O2x(PO4)2F3-2x

“…They are also safer, made from cheaper raw resources, and show a higher working potential. These compounds are usually synthesized using a two-step solid-state reaction [8], hydrothermal reactions [14], or the sol-gel method [15]. These processes are time-consuming or complicated.…”