Fast discharge process of layered cobalt oxides due to high Na+ diffusion

Takayuki Shibata, Yuya Fukuzumi, Wataru Kobayashi, Yutaka Moritomo

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Sodium ion secondary battery (SIB) is a low-cost and ubiquitous secondary battery for next-generation large-scale energy storage. The diffusion process of large Na+ (ionic radius is 1.12 Å), however, is considered to be slower than that of small Li+ (0.76 Å). This would be a serious disadvantage of SIB as compared with the Lithium ion secondary battery (LIB). By means of the electrochemical impedance spectroscopy (EIS), we determined the diffusion constant (D) of Na+ in thin films of O3- and P2-type NaCoO2 with layered structures. We found that the D values (∼ 0.5-1.5 × 10-10 cm2/s) of Na+ are higher than those (<1 × 10-11 cm2/s) of Li+ in layered LiCoO2. Especially, the D values of O3-NaCoO2 are even higher than those of P2-NaCoO2, probably because O3-NaCoO2 shows successive structural phase transitions from the O3, O'3, P'3, to P3 phases with Na+ deintercalation. We further found that the activation energy (E D ∼ 0.4eV) for the Na+ diffusion is significantly low in these layered cobalt oxides. We found a close relation between the relative capacity and the renormalized discharge rate (= L2/DT, where L and T are the film thickness and discharge time, respectively).

Original languageEnglish
Article number9006
JournalScientific Reports
Volume5
DOIs
Publication statusPublished - 2015 Mar 11
Externally publishedYes

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storage batteries
cobalt oxides
sodium
ions
energy storage
film thickness
lithium
impedance
activation energy
radii
thin films
spectroscopy

ASJC Scopus subject areas

  • General

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Fast discharge process of layered cobalt oxides due to high Na+ diffusion. / Shibata, Takayuki; Fukuzumi, Yuya; Kobayashi, Wataru; Moritomo, Yutaka.

In: Scientific Reports, Vol. 5, 9006, 11.03.2015.

Research output: Contribution to journalArticle

Shibata, Takayuki ; Fukuzumi, Yuya ; Kobayashi, Wataru ; Moritomo, Yutaka. / Fast discharge process of layered cobalt oxides due to high Na+ diffusion. In: Scientific Reports. 2015 ; Vol. 5.
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