Page 9 - ICIFMS
P. 9
201-002
Mechanical spectroscopy for the investigation of materials for energy applications
Paolone, A.(1); Palu mbo, O.(1); Trequattrini, F.(2);
(1) CNR-ISC; (2) S;
Presenter: Annalisa Paolone (CNR-ISC)
Keyword: mechanical spectroscopy, materials for energy applications, tension modulus,
local dynamics
Abstract:
Storage and transformation of energy is one of the priorities for the future. The basis for
improvements in this field is the synthesis and characterization of new materials with
better performances in energy devices. In order to achieve optimized applications, a deep
knowledge of the basic physical and chemical properties of these compounds is needed.
In this framework, we conducted an investigation of many materials with potential
applications in the field of energy storage and conversion by means of mechanical
spectroscopy. Our investigations exploited the full potential of mechanical spectroscopy:
in fact, both the real and the imaginary part of mechanical modulus can give useful
information about applicative materials. Indeed, on one side, in applications there a need
of optimized mechanical properties of materials; for example, we measured the tension
modulus of polymeric membranes useful as polymeric electrolyte membranes of fuel cells
and its evolution with the addition of inorganic fillers. Moreover, both the shear and
tension modulus of cellulose based membranes, intended as water compatible, gel
electrolytes, are reported. Finally, we investigated the changes induced by a hot pressing
process of the tension modulus and of the electrolyte uptake of electrospun polymeric
membranes used as separators in lithium batteries. On the other side, mechanical
spectroscopy can provide useful parameters of the local motion of atoms and defects or
of the occurrence of phase transitions. In the field of electrodes materials for lithium
batteries, LiMn1.5Ni0.5O4 was investigated by mechanical spectroscopy in order to
study the manganese dynamics. An intense thermally activated peak, detectable only in
off-stoichiometric samples, was attributed to a polaronic conduction due to an electron
transfer from Mn3+ to a Mn4+, and the consequent motion of the Jahn–Teller lattice
distortion. In order to have a good fit of the experimental data, the Jonscher model for
ionic dynamics was adopted for the first time in this spinel structure. A value of about 0.3
eV for the energy barrier of the polaronic conduction was obtained. Moreover, in the last
years we investigated ionic liquids (ILs) by means of mechanical spectroscopy. ILs
present peculiar physical and chemical properties: an extremely low vapor pressure, a
high ionic conductivity, a high thermal, chemical and electrochemical stability, a high
thermal capacity and a good solvent capacity. Due to these peculiarities, ILs have been
proposed for a large variety of applications in chemistry and physics, such as electrolytes
for electrochemical devices, lubricants, ingredients for pharmaceuticals and heat
exchangers. By modifying the method of measurement of a Dynamical Mechanical
Analyzer, we could measure relaxation processes occurring in the liquid phase, due to the
internal movements of the composing ions. Moreover, one can easily detect phase
transitions towards solid phases. Due to the occurrence of vitrification at low
temperatures in most ILs, proper theoretical models for the relaxation peaks should be
considered. A survey of the results obtained in this field will be presented. REFERENCES
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