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Disordered Bilayered V 2 O 5 ⋅ n H 2 O Shells Deposited on Vertically Aligned Carbon Nanofiber Arrays as Stable High‐Capacity Sodium Ion Battery Cathodes ⋅
Author(s) -
Brown Emery,
Acharya Jagaran,
Elangovan Ayyappan,
Pandey Gaind P.,
Wu Judy,
Li Jun
Publication year - 2018
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201800363
Subject(s) - materials science , dielectric spectroscopy , ion , raman spectroscopy , faraday efficiency , orthorhombic crystal system , cathode , analytical chemistry (journal) , electrochemistry , cyclic voltammetry , electrode , nanotechnology , chemical engineering , crystallography , crystal structure , chemistry , physics , organic chemistry , chromatography , optics , engineering
Due to the large radius of Na + ions, it has been challenging to find suitable host materials for sustainable sodium ion batteries (SIBs). This study investigates sputter‐coated thin V 2 O 5 shells on vertically aligned carbon nanofiber (VACNF) arrays as a novel three‐dimensional (3D) core‐shell material for SIB cathodes. SEM, TEM, XRD and Raman spectroscopy revealed that the as‐deposited V 2 O 5 shell has a highly disordered bilayered V 2 O 5 ⋅ n H 2 O structure with a large interlayer spacing of 11.0 Å, which can accommodate Na + ions better than orthorhombic α‐V 2 O 5 crystals. This hydrated metastable structure has been systematically characterized for Na + storage. A high initial insertion capacity of 277 mAh g −1 can be achieved at a current density of 250 mA g −1 in the potential window of 4.0–1.0 V (vs Na/Na + ). Using higher charge‐discharge rate or narrower potential windows, the electrode becomes more reversible, able to reach a coulombic efficiency of ∼99 %. Cyclic voltammetry, galvanostatic charge‐discharge and electrochemical impedance spectroscopy measurements indicate that the Na + storage is dominated by a large pseudocapacitive contribution due to fast surface reactions, which facilitates the improved stability and high power density. Such highly disordered bilayered V 2 O 5 ⋅ n H 2 O material in the 3D core‐shell architecture provides new insights for developing future SIB materials.