In operando X-ray absorption fine structure studies of polyoxometalate molecular cluster batteries: Polyoxometalates as electron sponges

Heng Wang, Shun Hamanaka, Yoshio Nishimoto, Stephan Irle, Toshihiko Yokoyama, Hirofumi Yoshikawa, Kunio Awaga

Research output: Contribution to journalArticlepeer-review

387 Scopus citations

Abstract

We carried out in operando Mo K-edge X-ray absorption fine structure measurements on the rechargeable molecular cluster batteries (MCBs) of polyoxometalates (POMs), in which a Keggin-type POM, [PMo 12O 40] 3-, is utilized as a cathode active material with a lithium metal anode. The POM-MCBs exhibit a large capacity of ca. 270 (A h)/kg in a voltage range between V = 4.0 V and V = 1.5 V. X-ray absorption near-edge structure analyses demonstrate that all 12 Mo 6+ ions in [PMo 12O 40] 3- are reduced to Mo 4+ in the discharging process. This means the formation of a super-reduced state of the POM, namely, [PMo 12O 40] 27-, which stores 24 electrons, and this electron number can explain the large capacity of the POM-MCBs. Furthermore, extended X-ray absorption fine structure analyses reveal the molecular structure of [PMo 12O 40] 27-, which is slightly reduced in size compared to the original [PMo 12O 40] 3- and involves Mo 4+ metal-metal-bonded triangles. Density functional theory calculations suggest that these triangles are formed because of the large number of additional electrons in the super-reduced state.

Original languageEnglish
Pages (from-to)4918-4924
Number of pages7
JournalJournal of the American Chemical Society
Volume134
Issue number10
DOIs
StatePublished - Mar 14 2012
Externally publishedYes

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