Photon Factory Activity Report 2016 #34 (2017)

AR-NW2A/2015P004

Construction of Solid Electrolytes by using Inorganic-Organic Hybrid Crystals

Takeru Ito1,* Yoshiki Kiyota, Jun Kobayashi, and Tatsuhiro Kojima2
1
Department of Chemistry, School of Science, Tokai University, Hiratsuka 259-1292, Japan.
2
Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 5600043, Japan
1 Introduction
Solid electrolytes are crucial materials for lithium-ion
or fuel-cell battery technology due to their structural
stability and easiness for handling. Emergence of highconductivity in the solid electrolytes requires precise
control of the composition and structure. A promisingstrategy toward highly conductive solid electrolytes is toemploy thermally stable inorganic component andstructurally flexible organic moiety to construct
inorganic-organic hybrid materials. [1]We report here syntheses and structures of Li+ cationcontaining hybrid crystals by using decavadate ([V10O28]6-,V10)
anion
andsurfactant(n-octylammonium,[C8H17NH3]+, C8NH3) cations. [2] Two types of crystals
with and without Li+ cation, C8NH3-V10 and C8NH3-LiV10, were obtained as single crystals.

C8NH3 and two Li+ cations were associated with one V10anion (Fig. 1b).
The Li+ cations exhibited fourcoordination geometry, connected to O atoms of watermolecules and of V10 anion to form an anion formulated
as {[Li(H2O)3]2[V10O28]}4- (denoted as Li2V10). The
crystal packing consisted of alternating Li2V10 inorganicmonolayers and C8NH3 organic layers (Fig. 1b) with alayered distance of 21.5 Å.
The anhydrous conductivities at the intermediate
temperature range were 8.2 x 10-8 S cm-1 for C8NH3-V10,and 1.1 x 10-8 S cm-1 for C8NH3-Li-V10. The lower
conductivity of C8NH3-Li-V10 may be because the Li+cations were in the O-H···O hydrogen bonding network
through the water ligands, which plausibly prevented easy
movement of the Li+ cations.

2 Experiment
The synthetic procedures are simple ion-exchange
reactions. C8NH3-V10 without Li+ cation was synthesized
by adding pH-adjusted V2O5 aqueous solution (pH 6.0) toC8NH3 ethanol solution. Obtained yellow-orange
precipitates of C8NH3-V10 were filtered off, and washedwith ethanol. Yellow rod crystals were obtained from thefiltrate or aqueous solution of C8NH3-V10. Yellow platelet
crystals of C8NH3-Li-V10 with Li+ cation were obtained
from the washing ethanol solution of the precipitates ofC8NH3-V10. Conductivity measurements were carried out
by alternating current (AC) impedance method under a
dry Ar atmosphere at 403 or 413 K. X-ray diffraction
measurements were performed at the PF-AR NW2A
beamline as well as with a laboratory diffractometer.
3 Results and Discussion
The precise control of synthetic procedure enabled theintroduction of Li+ cation by compositional control. TheC8NH3-Li-V10 is the first polyoxometalate-surfactant
crystal with Li+ cation introduced.
The formula of C8NH3-V10 without Li+ cation was[(C8H17)NH3]6[V10O28]·2H2O, revealed by the single
crystal X-ray analysis. Six C8NH3 cations (1+ charge)
were associated with one V10 anion (6- charge) due to thecharge compensation. No other small counter cation wasincluded, although V10 anion tends to be hybridized withseveral numbers of proton in the crystals. The crystal
packing consisted of alternating V10 inorganic monolayers
parallel to the bc plane and C8NH3 surfactant organiclayers with a layered distance of 20.8 Å (Fig. 1a).
C8NH3-Li-V10 with Li+ cation was formulated to be[(C8H17)NH3]4Li2[V10O28]·4C2H5OH·6H2O, and fourFig. 1: Crystal structures of (a) C8NH3-V10 and (b)C8NH3-Li-V10.
References[1] T. Ito, Crystals, 6, 24 (2016).
[2] Y. Kiyota, M. Taira, S. Otobe, K. Hanyuda, H. Naruke,and T. Ito, CrystEngComm, 19, 3037 (2017).
* takeito@keyaki.cc.u-tokai.ac.jp