Effect of Crystal Structure and Morphology on Na₃V₂(PO₄)₂F₃ Performances for Na‐Ion Batteries

Abstract

Na‐ion batteries (SIB) are considered promising systems for energy storage devices, however diversity of available cathode materials is lower compared to lithium ion batteries. Recently, Na3V2(PO4)2F3 (NVPF) has been demonstrated as promising cathode material for SIB owing to high specific capacity and electrochemical reversibility. However, most of reports demonstrates capacities lower than theoretical value and optimization of electrochemical performances by controlled morphology and crystal structure was not demonstrated yet. Here, we demonstrate a scalable synthesis strategy to tailor the crystal structure and morphology of NVPF and showed that our approach enables to optimize the Na+ ion accommodation, diffusion and stability. A flower morphology (NVPF‐F) crystalizes in tetragonal structure, demonstrates discharge capacity of 109.5 mA.h.g−1 and 98.1 % columbic efficiency whereas a hollow spherical morphology (NVPF‐S) with orthorhombic structure exhibits discharge capacity of 124.8 mA.h.g−1 (very close to theoretical value) and 99.5 % columbic efficiency. The observed discharge capacity for NVPF‐S is highest reported value which is ascribed due to stable crystal structure and monodispersed morphology. Long term stability with negligible capacity loss is demonstrated over 550 cycles. Our findings shed light on importance of crystal structure and morphology of NVPF on electrochemical response, and realization as cathode material for SIB.

Optimization Design and Application of Niobium‐Based Materials in Electrochemical Energy Storage

“…The three main characteristics of nanoscale materials are their small size, high specific surface area, and easy stress relaxation processes. [94] A-H) Reproduced with permission. [84] Copyright 2020, Elsevier.…”

Rationally Designed Vanadium Pentoxide as High Capacity Insertion Material for Mg‐Ion

“…The shifting of the pattern supports the claim of multiple intercalation/deintercalation of Mg +2 ions and accounted for obvious increase in the interplanar spacing ( d ). [ 49,50 ] Figure S4a,b (Supporting Information) shows the low magnification and high magnification SEM image of the cycled V 2 O 5 electrode. It is distinctly observed that the V 2 O 5 retained its spherical morphology and monodispersion eventually after the electrochemical cycling.…”

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

“…However, the rate capability and cyclability of Na 3 V 2 (PO 4 ) 2 F 3 are significantly restricted by its low electronic conductivity. The previous reports proved that electrochemical performance of Na 3 V 2 (PO 4 ) 2 F 3 was substantially enhanced by synthesis of composites of Na 3 V 2 (PO 4 ) 2 F 3 and carbonaceous materials, and this improvement is mainly ascribed to the introduction of carbonaceous substances with high electronic conductivity and hence the increase of electronic conductivity of composites. Within these composites, the dually modified composites such as Na 3 V 2 (PO 4 ) 2 F 3 @C/CNTs, double‐shelled carbon coated Na 3 V 2 (PO 4 ) 2 F 3 @C, Na 3 V 2 (PO 4 ) 2 F 3 @C/mesoporous carbon matrix and Na 3 V 2 (PO 4 ) 2 F 3 /C@rGO have much better electrochemical performance, especially rate performance, suggesting that electronic conductivity and microstructure of surface modifiers are important factors to influence the electrochemical performance of electroactive Na 3 V 2 (PO 4 ) 2 F 3 .…”