1
Structure, thermal properties, conductivity and electrochemical
stability of di-urethanesil hybrids doped with LiCF3SO3
M. C. Gonçalvesa, V. de Zea Bermudeza,* , M. M. Silvab, M. J. Smithb, E. Moralesc,
R. A. Sá Ferreirad, L. D. Carlosd
a
Departamento de Química/CQ-VR, Universidade de Trás-os-Montes e Alto Douro
5001-801 Vila Real, Portugal
b
Departamento de Química, Universidade do Minho, Gualtar, 4710-057 Braga, Portugal
c
Instituto de Ciencia y Tecnología de Polímeros del CSIC
Calle Juan de la Cierva 3, 28007 Madrid, Spain
d
Departamento de Física/ CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal
Abstract
Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid
networks were prepared by application of a sol-gel strategy. These materials, designated
as di-urethanesils (represented as d-Ut(Y’), where Y’ indicates the average molecular
weight of the polymer segment), were doped with lithium triflate (LiCF3SO3). The two
host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with
approximately 6 and 13 (OCH2CH2) repeat units, respectively. All the samples studied,
with compositions  > n  1 (where n is the molar ratio of (OCH2CH2) repeat units per
Li+),, are entirely amorphous. The di-urethanesils are thermally stable up to at least 200
ºC. At room temperature the conductivity maxima of the d-Ut(300)- and d-Ut(600)based di-urethanesil families are located at n = 1 (approximately 2.0x10-6 and 7.4x10-5
Scm-1, respectively). At about 100 ºC, both these samples also exhibit the highest
*
Phone: 00-351-259-350253; Fax: 00-351-259-350480; E-mail: vbermude@utad.pt
2
conductivity of the two electrolyte systems (approximately 1.6x10-4 and 1.0x10-3 Scm-1,
respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability.
Keywords: di-urethanesils, lithium triflate, DSC, TGA, XRD, complex impedance,
cyclic voltammetry
INTRODUCTION
Polymer electrolytes (PEs), obtained through the dissolution of an inorganic salt in
a polymer matrix, represent a unique class of solid coordination compounds. They have
potential applications in various all-solid-state devices, including rechargeable lithium
batteries, flexible electrochromic displays and smart windows. To be considered a good
candidate for the electrolyte component of such devices, a PE should fulfill certain
prerequisites:
high
ionic
conductivity
and
good
mechanical,
thermal
and
electrochemical stability.
POE has an extraordinary capacity for dissolving a variety of ionic salts and
consequently has been the most widely investigated host macromolecule for PE
applications [1-3]. For nearly three decades the high degree of crystallinity of POEbased systems was considered to be the main limitation to their practical application as
electrolytes, as it was believed that crystalline polymer/salt complexes were poor ionic
conductors [4]. As a result the development of 2nd and 3rd generation electrolytes placed
some emphasis on the reduction or suppression of crystallinity through tailoring of
polymer architecture and/or the choice of the guest salt [3]. This view prevailed until the
pioneering work of Gadjourova et al. [5] was published. These authors demonstrated
that ion transport could take place in crystalline polymer phases, although with
relatively low conductivities. A few years later Christie et al. [6] showed that suitable
3
additives could enhance the conductivity of crystalline PEs, a result that represented a
significant breakthrough in the development of novel electrolytes.
Over the last two decades our group has extensively investigated di-urea and diurethane cross-linked POE/siloxane-based systems (designated as di-ureasils [7,8] and
di-urethanenesils [9] (Scheme 1 [10]) doped with mono-, di- and trivalent cations. The
two families of hybrids were identified by the notations d-U(Y) and d-Ut(Y’), where d
represents di, U and Ut denote urea and urethane, respectively, and Y = 600, 900 or
2000 and Y’= 300 or 600 indicate the average molecular weight of the organic
precursors (corresponding to about 8.5, 15.5 or 40.5 and 6 or 13 oxyethylene repeat
units, respectively) (Scheme 1 (a) and (b), respectively). The overall synthetic strategy
relies on the combination of the organic/inorganic hybrid concept [11] with the sol-gel
route [12] to produce the host hybrid networks that are subsequently doped with guest
compounds in the light of the host/guest approach inherited from the domain of PEs. In
these POE/siloxane hybrid electrolytes, designated as ormolytes (organically modified
silicate electrolytes), the most useful features of POE (solvating ability of the ether units
and great flexibility) are combined with the amorphous nature, good mechanical
resistance and remarkable thermal stability provided by the siliceous component. The
non-hygroscopic character, high transparency, ready processability into thin monolithic
films and remarkable capacity to incorporate higher guest salt concentrations than other
candidate materials, attracted our interest.
Di-ureasil matrices were considered to be promising hosts for applications in the
domain of optics, both in the non-doped state [13,14] and doped with lanthanide salts or
complexes [15]. The potential of di-ureasils for the field of magnetism
[16]/biomimetism [17] has become apparent and their suitability as electrolytes for solid
state electrochemical devices has also been demonstrated. Di-ureasil networks have
4
been doped with alkali (Li+ [18-20], Na+ [21] and K+ [22]), alkaline-earth (Mg2+ [23]),
transition (Zn2+ [24]) and lanthanide (Eu3+ [25], Er3+ [26] and La3+ [27]) metal ions.
Studies reporting the properties of di-urethanesils are significantly less abundant.
Although the optical properties of non-doped [28] and lanthanide-doped (Eu3+ [29-32]
and Nd3+ [10]) di-urethanesils have been examined, their interest for solid state
electrochemistry remains uncertain. This lack of data motivated the present work. The
moderate levels of conductivity displayed by the Li+-containing di-ureasil ormolytes
encouraged us to characterise the thermal behaviour, the structure, the morphology and
the electrochemical properties of d-Ut(300)- and d-Ut(600)-based di-urethanesils
containing a wide range of LiCF3SO3 concentration.
EXPERIMENTAL
Materials
Lithium trifluoromethanesulphonate (or triflate) (LiCF3SO3, Aldrich) and 3isocyanatepropyltriethoxysilane (ICPTES, Fluka) were used as received. The
poly(ethylene glycol)s (PEGs, Aldrich), tetrahydrofurane (THF, Merck) and ethanol
(CH3CH2OH, Merck) were dried by storage over molecular sieves. High purity distilled
water was used in all experiments.
Synthesis of the d Ut(300)nLiCF3SO3 and d-Ut(600)nLiCF3SO3 di-urethanesils
The first stage of the synthesis of the d-Ut(300)- and d-Ut(600)-based di-urethanesils
involved the formation of covalent urethane linkages between the terminal hydroxyl
groups of a poly(ethylene glycol) including about 6 oxyethylene or 13 units, PEG(300)
or PEG(600), respectively, and the isocyanate groups of the alkoxysilane precursor
ICPTES. In the second stage of the synthesis water and ethanol were added to promote
the hydrolysis and condensation reactions characteristic of the sol-gel process. The
5
guest salt, LiCF3SO3¸ was added in the second step. D-Ut(300)- and d-Ut(600)-based
di-urethanesil materials d with n = , 400, 200, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10,
5, 3, 2 and 1 and n = , 100, 40, 20, 10, 5, 3 and 1, respectively, were prepared. In
agreement with the terminology adopted in previous publications [9,10,29-32], the
doped ormolytes examined were identified using the notation d-Ut(Y’)nLiCF3SO3.
Step 1 - Synthesis of the di-urethanesil hybrids precursors, d-UtPTES(300) and
d-UtPTES(600) (Schemes 1(a) and (b), respectively): 1.5 g of PEG(300) or PEG(600),
respectively, were dissolved in 10 mL of THF by stirring. A volume VICPTES (Table 1)
was added to this solution in a fume cupboard (molar proportion 2 ICPTES:1
PEG(300)). The flask was then sealed and the solution stirred for 24 h at moderate
temperature (approximately 70 °C). The grafting process was infrared monitored.
During the formation of the urethane cross-links the intensity of the prominent and
sharp absorption band located at 2273 cm-1, ascribed to the stretching vibration of the
isocyanate group of the Si-(CH2)3-N=C=O moiety, progressively decreased, until it
disappeared upon completion of the reaction. These spectral changes were accompanied
by the growth of a series of new bands produced by the urethane group in the 17601530 cm-1 spectral region. The d-UtPTES(300) and d-UtPTES(600) compounds were
obtained as transparent oils.
Step 2 - Synthesis of the di-urethanesil hybrid xerogels, d-Ut(300)nLiCF3SO3 and dUt(600)nLiCF3SO3: Volumes VCH3CH2OH and VH2O (Table 1) and an appropriate mass of
LiCF3SO3 (Table 1) were added to the solutions prepared in the first stage of the
synthetic procedure (molar proportion 1 ICPTES: 4 CH3CH2OH: 1.5 H2O). The
mixtures were stirred in a sealed flask for 30 min and then cast into a Teflon mould
which was covered with Parafilm and left in a fume cupboard for 24 h. After a few
hours gelation was already visible. The mould was transferred to an oven at 60 °C and
6
the sample was aged for a period of 2 weeks. The resulting xerogels were obtained as
transparent and slightly yellowish monoliths (Fig. 1). The d-Ut(600)-based samples
were considerably more flexible than the di-urethanesils prepared using the lower
molecular weight PEG(300).
X-ray diffraction (XRD)
The diffractograms of the d-Ut(600)-based di-urethanesils were recorded using a
PW1729 Philips X-ray generator and a PW 1840 Philips diffractometer. The samples
were exposed to the CuKradiation ( = 1.54 Å) at room temperature in the 2range
between 1 and 70º. XRD patterns of the d-Ut(300)-based samples were recorded at
room temperature with a Rigaku Geigerflex D/max-c diffractometer system using
monochromated CuK radiation ( = 1.54 Å) over the 2 range of between 4 and 80 º at
a resolution of 0.05 º. The xerogel samples, analyzed as films, were not subjected to any
thermal pre-treatment.
Thermogravimetric Analysis (TGA) and Differental Scanning Calorimetry (DSC)
The thermogravimetric analyses were performed using Mettler TGA/SDTA 851
equipment. Samples of about 5 mg mass were heated at 5 ºC min-1 from room
temperture to 650 ºC under a high purity nitrogen (N2) atmosphere. This gas was
supplied at a constant 20 cm3 min-1 flow rate. The decomposition temperatures were
obtained by extrapolating curve segments from the thermogram to obtain an estimate of
the onset temperature of weight loss. A DSC131 Setaram Differental Scanning
Calorimeter was employed to determine the thermal behaviour of the xerogel
compounds. A disk section with a mass of approximately 20 mg was removed from
each di-urethanesil film, placed in a 40 μl aluminium can and stored in a desiccator over
phosphorous pentoxide for at least 12 h at room temperature and under vacuum. After
this drying treatment the can was hermetically sealed and the thermogram of the sample
7
was recorded. The sample was heated from room temperature to 300 °C at 10 °C min-1
under high purity N2 supplied at a constant 35 cm3 min-1 flow rate.
Complex impedance measurements
Bulk conductivity measurements were carried out on an electrolyte disk was placed
between two 10 mm diameter ion-blocking gold electrodes (Goodfellow, >99.9%). The
electrode/electrolyte/electrode assembly was secured in a suitable constant volume
support installed in a Buchi TO51 tube oven and the sample temperature was evaluated
by a type K thermocouple placed close to the electrolyte disk. Measurements were
obtained during heating cycles using the complex plane impedance technique
(Schlumberger Solartron 1250 frequency response analyzer and 1286 electrochemical
interface) over a temperature range of between 25 and 100 oC and at approximately 7 ºC
intervals.
Cyclic Voltammetry (CV)
The electrochemical stability of the most conducting ormolyte of the two series
synthesized was examined by means of CV using a Radiometer/Copenhagen Voltalab
32 potentiostat/galvanostat. A stainless steel working electrode and lithium foil counter
and reference electrodes were employed. Swagelok type test cells (6 mm diameter) were
assembled and sealed in an argon-filled glove box. Prior to characterisation, the
ormolyte sample was dried under vacuum at 60 ºC for about 24 hours. The experiment
was run at 80 ºC at a sweep rate of 10 mVs-1.
RESULTS AND DISCUSSION
Structure
The diffractograms of selected d-Ut(300)nLiCF3SO3 and d-Ut(600)nLiCF3SO3
samples are illustrated in Figs. 2(a) and (b), respectively. From the analysis of these
8
XRD data we may immediately conclude that both families of xerogels are totally
amorphous. No crystalline phases (e.g., POE or POE/salt complexes or free salt) are
formed in the d-Ut(300) and dUt(600) media in the range of compositions inspected.
The only other aspect of the XRD patterns of Figs. 2(a) and (b) worth mentioning is the
existence of a characteristic amorphous broad peak centred at about 21.6 º, attributed to
the coherent diffracting domains of the siliceous framework [13]. The structural unit
distance, calculated using the Bragg law, is ca. 4.1 Å.
Thermal stability
The TGA curves of representative d-Ut(300)nLiCF3SO3and d-Ut(600)nLiCF3SO3
diurethanesils, collected in Figs. 3(a) and (b), respectively, indicate that in both series of
hybrids the presence of increasing amounts of the guest lithium salt does not appear to
destabilize significantly the hybrid host structure in a non-oxidizing atmosphere. In both
families of diurethanesils with n > 5 thermal decomposition begins at approximately
200-225 ºC (assuming a mass loss ≤ 5 %) and is a three-step process (Figs. 3(a) and
(b)). In the case of the d-Ut(600)nLiCF3SO3 samples, the progressive loss of mass that
occurs immediately after starting the experiment, clearly seen in the most concentrated
sample (Fig. 3(b)), is probably associated with the release of liquids (LiCF3SO3
hydration water molecules, adsorbed water, and occluded CH3CH2OH and/or THF).
The absence of events in the DSC thermograms of the d-Ut(300)nLiCF3SO3 and dUt(600)nLiCF3SO3 di-urethanesils (Figs. 4(a) and (b), respectively) confirm the
amorphous character of all the samples examined, supporting the XRD data. The DSC
curves of the salt-rich xerogels d-Ut(600)3LiCF3SO3 and d-Ut(600)5LiCF3SO3 display a
broad endothermic peak centred at ca. 175 ºC, with onset at about 80 ºC (Fig. 4(b)). On
the basis of the TGA results (Fig. 3(b)), this thermal event is attributed to the loss of
9
chemically and/or physically bonded water molecules and with the evaporation of
solvents.
Conducting properties and electrochemical stability domain
The Arrhenius conductivity plots of selected d-Ut(300)nLiCF3SO3 and dUt(600)nLiCF3SO3 di-urethanesils are illustrated in Figs. 5(a) and (b) and the
corresponding conductivity isotherms are depicted in Figs. 6(a) and (b), respectively.
The curves of Figs. 5(a) and (b) clearly demonstrate that the levels of ionic conductivity
exhibited by the d-Ut(300)nLiCF3SO3 hybrids are considerable lower than those of the
d-Ut(600)nLiCF3SO3 xerogels over the whole range of temperatures studied. This result
was expected as the POE chains of the latter series of POE/siloxane hybrids double the
length of those in the lower molecular weight network. The use of shorter chains to link
siliceous domains results in a mechanically more rigid network and restricted chain
segment mobility.
The ionic conductivity of the non-doped host hybrid di-urethanesils (at 24 ºC the
value observed for d-Ut(600) is 2x10-8 Scm-1 (Fig. 5(b)) is higher than the values
produced by the d-Ut(300)-based xerogels with n =100 and 20 (Fig. 5(a)). This residual
conductivity of the host matrix has been attributed to proton hopping between the
urethane cross-links [8]. It is noteworthy that in both series of di-urethanesils the
maximum ionic conductivity is located at n = 1 (Figs. 6(a) and (b)). At 24 ºC while the
conductivity of d-Ut(300)1LiCF3SO3 is 3.1x10-6 Scm-1 that of d-Ut(600)1LiCF3SO3 is
7.4x10-5 Scm-1. At about 100 ºC the values observed are 1.6x10-4 and 1.3x10-3 S cm-1,
respectively.
Let us now compare these results with those reported for the d-U(600)-based diureasils incorporating a number of oxyethylene repeat units (about 8.5) that lies between
those of the d-Ut(300)nLiCF3SO3 and d-Ut(600)nLiCF3SO3 (about 6 and 13,
10
respectively). At room temperature the d-U(600)1LiCF3SO3 sample exhibits the highest
conductivity (4.3x10-6 Scm-1), whereas at 94 ºC, the latter compound and that with n =
0.5 display the highest conductivity (2.0x10-4 Scm-1) [18].
In the early 1980s, Rigaud [33] concluded that, although the CF3SO3- ion was not a
suitable anion to be used in POE-based PEs for secondary lithium batteries, LiCF3SO3
may be employed safely in primary batteries, because the insoluble layer of LiF that is
formed exerts a protecting effect on the lithium electrode. The remarkable ormolyte
stability of the d-Ut(600)1LiCF3SO3 composition at which the conductivity maximum is
observed is confirmed by the negligibly small currents registered at extreme potentials
(e.g., 5 nA/cm2 at 5 V vs. Li/Li+) and the lack of cathodic or anodic peaks (Fig. 7). This
finding is in agreement with previous studies of a poly(urethane) electrolyte doped with
lithium perchlorate for which a redox stability window of approximately 4.0 V was
reported [34].
CONCLUSION
The structure, thermal behaviour, ionic conductivity and electrochemical stability
of two series of di-urethanesils incorporating POE chains of two different molecular
weights and doped with a wide concentration range of lithium triflate (LiCF3SO3) were
investigated.
The d-Ut(600)1LiCF3SO3 sample exhibits the highest ionic conductivity examined
(about 7.4x10-5 Scm-1 at 24 ºC and 1.0x10-3 Scm-1 at 100 ºC) of all the xerogels
examined and is transparent, flexible, entirely amorphous and thermally stable up to
about 200 ºC. In addition, this composition displays an excellent redox stability.
The encouraging results obtained with the d-Ut(600)nLiCF3SO3 hybrids in terms of
ionic conductivity and mechanical properties, lead us to suggest that further research on
11
Li+-doped d-Ut(600)-based di-urethanesils is justified. It is expected that the
replacement of LiCF3SO3 by a more suitable 3rd generation lithium salt (e.g., lithium
bis(trifluoromethanesulfonyl)imide (TFSI)) will provide access to xerogels with higher
ionic conductivities.
ACKNOWLEDGEMENT
The authors acknowledge financial support from Fundação para a Ciência e a
Tecnologia (contract POCI/QUI/59856/2004).
REFERENCES
[1] P. V. Wright, Br. Polym. 7 (1975) 319
[2] M. Armand, M. T. Duclot, J. M. Chabagno, In Proceedings of the Second
International Meeting on Solid State Electrolytes, St. Andrews, Scotland, 1978
[3] F. M. Gray, Polymer Electrolytes, RSC Materials Monographs, The Royal Society
of Chemistry, London, 1997
[4] C. Berthier, W. Gorecki, M. Minier, M. B. Armand, J. M. Chabagno and P. Rigaud,
Solid State Ionics, 11 (1983) 91
[5] Z. Gadjourova, Y. G. Andreev, D. P. Tunstall and P. G. Bruce, Nature, 412 (2001)
520
[6] A. M. Christie, S. J. Lilley, E. Staunton, Y. G. Andreev, P. G. Bruce, Nature 433, 53
(2005) 50
[7] M. Armand, C. Poinsignon, J.-Y. Sanchez and V. de Zea Bermudez, U.S. Pat.
5,283,310, 1994
[8] V. de Zea Bermudez, C. Poinsignon and M. B. Armand, J. Mater. Chem., 7(9)
(1997) 1677
12
[9] M. C. Gonçalves, V. de Zea Bermudez, D. Ostrovskii and L. D. Carlos, Ionics,
8(1&2) (2002) 62
[10] M. C. Gonçalves, N. J. O. Silva, V. de Zea Bermudez, R. A. Sá Ferreira, L. D.
Carlos, K. Dahmouche, C. V. Santilli, D. Ostrovskii, I. C. Correia Vilela and A. F.
Craievich, J. Phys. Chem. B, 109 (2005) 20093
[11] P. Gomez-Romero and C. Sanchez, Functional Hybrid Materials, Wiley
Interscience: New York, 2003
[12] C. J. Brinker and G. W. Scherer, Sol-gel Science: The Physics and Chemistry of
Sol-Gel Processing, Academic Press: San Diego, CA, 1990
[13] L. D. Carlos, V. de Zea Bermudez, R. A. Sá Ferreira, L. Marques and M.
Assunção, Chem. Mater., 11(3) (1999) 581
[14] L. Fu, R. A. Sá Ferreira, N. J. O. Silva, L. D. Carlos, V. de Zea Bermudez and J.
Rocha, Chem. Mater., 16 (2004) 1507
[15] L. D. Carlos, R. A. Sá Ferreira, V. de Zea Bermudez and S. J. L. Ribeiro, Adv.
Mater., 20 (2008) 1
[16] N. J. O. Silva, V. S. Amaral, L. D. Carlos, B. Rodríguez-González, L. M. LizMarzán, A. Millan, F. Palacio and V. de Zea Bermudez, J. Appl. Phys., 100 (2006)
054301 (1-6)
[17] N. J. O. Silva, V. S. Amaral, V. de Zea Bermudez, S. C. Nunes, D. Ostrovskii, J.
Rocha and L. D. Carlos, J. Mater. Chem., 15 (2005) 484
[18] S. M. Gomes Correia, V. de Zea Bermudez, M. M. Silva, S. Barros, R. A. Sá
Ferreira, L. D. Carlos, A. P. Passos de Almeida and M. J. Smith, Electrochim. Acta,
47/15 (2002) 2421
13
[19] S. C. Nunes, V. de Zea Bermudez, D. OstrovskiI, M. M. Silva, S. Barros, M. J.
Smith, R. A. Sá Ferreira, L. D. Carlos, J. Rocha and E. Morales, J. Electrochem. Soc.,
152(2) (2005) A429
[20] M. M. Silva, P. C. Barbosa, S. C. Nunes, V. de Zea Bermudez and M. J. Smith,
Electrochim. Acta, 52(4) (2006) 1542
[21] S. M. Gomes Correia, V. de Zea Bermudez, M. M. Silva, S. Barros, R. A. Sá
Ferreira, L. D. Carlos, A. P. Passos de Almeida and M. J. Smith, Solid State Ionics,
156/1-2 (2003) 85
[22] S. C. Nunes, V. de Zea Bermudez, M. M. Silva, M. J. Smith, D. Ostrovskii, R. A.
Sá Ferreira, L. D. Carlos, J. Rocha, A. Gonçalves and E. Fortunato, J. Mater. Chem., 17
(2007) 4239
[23] S. C. Nunes, V. de Zea Bermudez, M. M. Silva, S. Barros, M. J. Smith, E. Morales,
L. D. Carlos and J. Rocha, Solid State Ionics, 176/17 (2005) 1591
[24] S. C. Nunes, V. de Zea Bermudez, M. M. Silva, M. J. Smith, E. Morales, R. A. Sá
Ferreira, L. D. Carlos and J. Rocha, Solid State Sciences, 8 (2006) 1484
[25] M. M. Silva, V. de Zea Bermudez, L. D. Carlos, A. P. Passos de Almeida and M. J.
Smith, J. Mater. Chem., 9 (1999) 1735
[26] S. M. Gomes Correia, V. de Zea Bermudez, R. A. Sá Ferreira, L. D. Carlos, M. M.
Silva, S. Barros and M. J. Smith, Ionics, 8(1&2) (2002) 73
[27] S. M. Gomes Correia, V. de Zea Bermudez, M. M. Silva, S. Barros, R. A. Sá
Ferreira, L. D. Carlos and M. J. Smith, Electrochim. Acta, 47/15 (2002) 2551
[28] L. D. Carlos, R. A. Sá Ferreira, V. de Zea Bermudez, S. J. L. Ribeiro, Adv. Funct.
Mater., 11(2) (2001) 111
[29] M. C. Gonçalves, V. de Zea Bermudez, R. A. Sá Ferreira, D. Ostrovskii and L. D.
Carlos, MRS Proceedings, 847 (2005) EE13.1
14
[30] L. D. Carlos, R. A. Sá Ferreira, M. C. Gonçalves and V. de Zea Bermudez, J.
Alloys & Compds, 374 (2004) 50
[31] M. C. Gonçalves, V. de Zea Bermudez, R. A. Sá Ferreira, L. D. Carlos, D.
Ostrovskii and J. Rocha, Chem. Mater., 16(13) (2004) 2530
[32] M. Fernandes, M. C. Gonçalves, V. de Zea Bermudez, A. Charas, J. Morgado, R.
A. Sá Ferreira and L. D. Carlos, J. Alloys & Compds, 451 (2008) 201
[33] P. Rigaud, Ph.D. Thesis, University of Grenoble, France, 1980
[34] J. F. Le Nest, Ph.D. Thesis, University of Grenoble, France, 1985
LIST OF FIGURE CAPTIONS
Figure 1. Physical appearance of a di-urethanesil sample
Figure 2. X-ray diffraction patterns of selected di-urethanesils: (a) d-Ut(300)nLiCF3SO3
and (b) d-Ut(600 nLiCF3SO3
Figure 3. TGA curves of selected di-urethanesils: (a) d-Ut(300)nLiCF3SO3 and (b) dUt(600)nLiCF3SO3
Figure 4. DSC thermograms of selected di-urethanesils: (a) d-Ut(300)nLiCF3SO3 and
(b) d-Ut(600)nLiCF3SO3
Figure
5.
Arrhenius
conductivity plot
of
selected
di-urethanesils:
(a)
d-
Ut(300)nLiCF3SO3 and (b) d-Ut(600)nLiCF3SO3
Figure 6. Isotherms of the ionic conductivity versus composition of selected diurethanesils: (a) d-Ut(300)nLiCF3SO3 and (b) d-Ut(600)nLiCF3SO3. Note: the lines
drawn are just guides for the eyes.
15
Figure 7. Room temperature cyclic voltamogram of the d-Ut(600)1LiCF3SO3 diurethanesil (1st cycle, sweep rate = 10 mV s-1) obtained with a stainless steel working
electrode and lithium counter and reference electrodes.
Table 1. Relevant details of the synthetic procedure of the d-Ut(300)nLiCF3SO3 and dUt(600)nLiCF3SO3 di-urethanesils
Scheme 1. Schematic representation of the non-doped di-urethanesil matrices: (a) dUt(300) and (b) d-Ut(600) [10]
Figure 1. M. C. Gonçalves et al., Ionics
16
n
0
Intensity (a. u.)
1
3
5
10
40
100

10
20
30
40
50
60
70
80
2\gf(q) (degree)
Figure 2. M. C. Gonçalves et al., Ionics
n
1
3
5
10
20
0
10
20
30
40
2 (degree)
50
60
70
17
100
90
Weight loss (wt%)
80
70
60
50
40
30
20
10
0
50
100
150
200
250
300
350
400
450
500
550
600
T (ºC)
(a)
n

100
100
40
20
10
5
1
90
Weight loss (%)
80
70
60
50
40
30
20
10
0
50
100
150
200
250
300
350
400
450
T(ºC)
(b)
Figure 3. M. C. Gonçalves et al., Ionics
500
550
600
650
650
18
n
1
3
500
5
10
20
endo
Heat Flow (mW/g)
exo
0
40
100

0
50
100
150
200
250
300
T (ºC)
Figure 4. M. C. Gonçalves et al., Ionics
n
3
5
10
20
40
100

0
50
100
150
T (ºC)
200
250
300
19
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
20
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.