Journal of Materials Chemistry A
Paper
observed in ab initio molecular dynamic simulations (MD) at
room temperature in the time scale of a picosecond (see ESI†).
The maximum energy barrier for the Li-ion to migrate in the
crystals is 0.4 eV, which is lower than in other solid state elec-
trolytes used in Li metal batteries.49–51 These calculations are
consistent with the experimental activation energy of 55 kJ molꢀ1
measured in the unsymmetrical (Li metal/PP13PF6 + 10 wt%
LiTFSI)/(Stainless Steel block) cell geometry.
6 T. Belhocine, S. A. Forsyth, H. Q. N. Gunaratne,
M. Nieuwenhuyzen, A. V. Puga, K. R. Seddon, G. Srinivasan
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8 H. Matsumoto, H. Sakaebe, K. Tatsumi, M. Kikuta, E. Ishiko
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9 G. A. Snook, A. S. Best, A. G. Pandolfo and A. F. Hollenkamp,
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4. Conclusions
10 H. Sakaebe and H. Matsumoto, Electrochem. Commun., 2003,
5, 594–598.
A high-purity ionic crystal of PP13PF6 stable to water and air has
been successfully synthesized and characterized. XRD analysis of
the crystal structure conrms that the formation of a solid crystal
at room temperature is due to the strong interaction between the
F of the PF6 anion and the H in the PP13 cation. This ionic crystal
showed a wide electrochemical potential window of stability of
7.2 V. Electrodeposition of electropositive Sn metal results in a
rod shaped morphology that may be of interest in microelec-
tronic applications. Ionic crystals showed enhanced Li-ion
transport with an ionic conductivity of 2.4 ꢃ 10ꢀ4 S cmꢀ1 at
45 ꢁC. The calculated energy barrier for the Li-ion conductivity of
only 0.4 eV matches well with the experimentally determined
activation energy. Further, MD simulations indicate that the
ionic crystal exhibits facile molecular motions which facilitate Li-
ion transport.
11 H.-H. Lee, Y.-Y. Wang, C.-C. Wan, M.-H. Yang, H.-C. Wu and
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13 S. Murugesan, A. Akkineni, B. P. Chou, M. S. Glaz,
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14 L. Jin, K. M. Nairn, C. M. Forsyth, A. J. Seeber,
D. R. MacFarlane, P. C. Howlett, M. Forsyth and
J. M. Pringle, J. Am. Chem. Soc., 2012, 134, 9688–9697.
15 J. M. Pringle, P. C. Howlett, D. R. MacFarlane and M. Forsyth,
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16 J. M. Pringle, Phys. Chem. Chem. Phys., 2013, 15, 1339–1351.
17 J. Sunarso, Y. Shekibi, J. Ehimiadis, L. Jin, J. Pringle,
A. Hollenkamp, D. MacFarlane, M. Forsyth and P. Howlett,
J. Solid State Electrochem., 2012, 16, 1841–1848.
18 P. M. Bayley, A. S. Best, D. R. MacFarlane and M. Forsyth,
Phys. Chem. Chem. Phys., 2011, 13, 4632–4640.
19 U. L. Bernard, E. I. Izgorodina and D. R. MacFarlane, J. Phys.
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20 J. B. Goodenough, Acc. Chem. Res., 2013, 46, 1053–1061.
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22 G. Ceder, S. P. Ong, O. Andreussi, Y. B. Wu and N. Marzari,
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23 A. M. O'Mahony, D. S. Silvester, L. Aldous, C. Hardacre and
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Acknowledgements
This work was supported as part of the program “Under-
standing Charge Separation and Transfer at Interfaces in
Energy Materials (EFRC: CST)”, an Energy Frontier Research
Center funded by the U.S. Department of Energy Office of
Science, Office of Basic Energy Sciences, under Award no. DE-
SC0001091. Authors Q.A.O and C.P.B thank The Welch Foun-
dation and The University of Texas at Austin for support via the
Welch Summer Scholar Program. S.M. thanks Vladimir I.
Bakhmutov for solid state NMR analysis. R.A.J. thanks The
Welch Foundation (F-816) and ACS-PRF (52682-ND10) for
nancial support.
25 H. Ye, J. Huang, J. J. Xu, A. Khalfan and S. G. Greenbaum,
J. Electrochem. Soc., 2007, 154, A1048–A1057.
26 H. Sakaebe and H. Matsumoto, Electrochem. Commun., 2003,
5, 594–598.
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