Effect of carbon source on electrochemical properties of spray-dried Na3V2(PO4)2F3/carbon composites as cathode material for Na-ion batteries

In recent years, fluorophosphates with the NASICON (Na Super-Ionic Conductor) type structure were studied as positive electrode materials for Li/Na-ion batteries, because they exhibit rich chemistry, attractive lithium/sodium... [ view full abstract ]

In recent years, fluorophosphates with the NASICON (Na Super-Ionic Conductor) type structure were studied as positive electrode materials for Li/Na-ion batteries, because they exhibit rich chemistry, attractive lithium/sodium insertion properties and thus offer promising electrochemical performance [1]. Among them, Na₃V₂(PO₄)₂F₃ (NVPF) deserves attention because of promising electrochemical properties and favorable characteristics. The NASICON-type crystallographic structure displays a highly covalent three-dimensional framework generating large interstitial spaces and providing three-dimensional tunnels for fast ion diffusion. The inductive effects of both PO₄^3- and F^- offer high working potential combined with a high theoretical specific capacity due to the multiple oxidation states of vanadium [2-3].

In this work, NVPF and NVPF/carbon composite powders were prepared using the spray-drying method. Spray drying is a cost-effective and easily up-scalable route to prepare homogeneous multi-component powders [2]. We studied the effect of different carbon sources such as conductive carbons or organic sources generating carbon upon heat treatment on NVPF/carbon composites.  XRD, TGA, SEM, TEM, Electrochemical impedance spectroscopy and Raman spectroscopy characterizations were performed in order to understand the influence of carbon source on the structure, morphology, reaction mechanism and most importantly electrochemical performance of NVPF and NVPF/carbon composite powders in Na-ion batteries. 

References:

[1] R. a. Shakoor, D.-H. Seo, H. Kim, Y.-U. Park, J. Kim, S.-W. Kim, H. Gwon, S. Lee, K. Kang, J. Mater. Chem. 22 (2012) 20535–20541.

[2] N. Eshraghi, S. Caes, A. Mahmoud, R. Cloots, B. Vertruyen, F. Boschini, Electrochimica Acta, 228, (2017), 319-324.

[3] W. Song, S. Liu, Solid State Sci. 15 (2013) 1–6.