Kinetic insight into the electrochemical sodium insertion-extraction mechanism of the puckered γ′-V2O5 polymorph. (1st November 2019)

• Record Type: Journal Article
• Authors: Safrany Renard, M.; Baddour-Hadjean, R.; Pereira-Ramos, J.P.
• Is Part Of: Electrochimica acta. Volume 322(2019)
• Publication Date: 2019-11-01
• Subjects: γ′-V2O5 -- Cathode material -- Kinetics -- Na diffusion -- Na-ion battery; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2019.134670
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: The kinetics of the electrochemical Na reaction in the γ′-V2 O5 polymorph prepared by the carboreduction route is investigated by electrochemical impedance spectroscopy. This cathode material with puckered layer structure is capable of delivering a high discharge capacity of 143 mAh g −1 at a relatively high operating voltage of 3.3 V vs. Na + /Na. In spite of a good cyclability, a low efficiency of the first charge process limits yet the value of the stable capacity of this material upon cycling. The present study intends to give further insight into the sodium insertion-extraction mechanism in γ′-V2 O5 by achieving a picture of the main kinetic parameters as a function of Na uptake in γ-Nax V2 O5 electrodes (0 ≤ x ≤ 0.97). We show that the evolution of cathode impedance, charge transfer resistance, double layer capacity and apparent chemical Na diffusion coefficient are highly correlated to the structural changes induced upon sodiation. A faster Na diffusion is revealed in the richest 0.6 < x ≤ 0.97 solid solution region while electron transport is slowed down in that composition domain due to the highly localized electron character of the sodiated phase. A significant modification of the surface area is also underlined, undoubtedly caused by the high volume expansion experienced during sodiation. The low efficiency of the first cycle, characterized by an important polarization at the end of the charge, is explained by a huge increase in the electrode impedance.