- Current research aims to improve battery technologies by developing solid polymer electrolytes with higher lithium ion conductivity than conventional liquid electrolytes for applications such as electric vehicles and renewable energy storage. - Previous studies showed increasing salt concentration in a polymer matrix initially increases ionic conductivity but then decreases at higher concentrations. Two models of ion transport reveal deviations from ideal behavior. - This work analyzes the relationship between ion transport and lithium salt concentration in a copolymer electrolyte using broadband dielectric spectroscopy. Preliminary results show a concentration of around 10% lithium salt yields the highest conductivity. Further variations of polymer composition are proposed to optimize conductivity.

1. RESEARCH POSTER PRESENTATION DESIGN © 2012
www.PosterPresentations.com
Ø Current technological advancements create a much larger role for
batteries in everyday life
Ø Portable and sustainable batteries are required to advance renewable
energy technologies,as well as electric vehicles and home energy
storage
INTRODUCTION
MATERIALSAND METHODS
CONCLUSIONS
Ø Conductivity increases as a function of salt concentration due to
increase in ion concentration. But then it drops at higher concentration
due to increase in TG and slowing down of polymer dynamics.
Ø Though it is evident that conductivity generally increases as a function
of salt concentration, further work is needed to define the optimal ion
concentration and polymer structure.
Ø Electron Polarization and Random Barrier models examine separate
regions of BDS measurement to find ion diffusivity
Ø These models have several assumptions which require farther
verification. As a result, they provide contradictory results.
REFERENCES
1. Y. Wang et al., Polymer 55, 4067 (2014).
2. J. C. Dyre, J. Appl. Phys. 64, 2456 (1988).
3. Y. Want et al., Phys. Rev. E 87, 042308 (2013).
4. Kremer F, SchönhalsA (Eds) (2003) Broadband dielectric
spectroscopy. Springer-Verlag Berlin Heidelberg GmbH, ISBN 978-3-
642- 62809-2,DOI 10.1007/978-3-642-56120-7
5. H. Wagner, R. Richert, J. Phys. Chem. B 103 (1999) 4071
ACKNOWLEDGEMENTS
1Department of Chemistry, University of Tennessee, Knoxville, Tennessee, 37996, United States
2Department of Physics and Astronomy, University of Tennessee, Knoxville, 37996, United States
3Fakultätfür Physik, Technische Universität Dortmund, 44221 Dortmund,Germany
4Chemical Sciences Division, Oak Ridge NationalLaboratory, Oak Ridge, Tennessee 37831, United States
Presented by Weston Bell1, Eric W. Stacy,2 Fei Fan,1 Catalin Gainaru,1,3 Tomonori Saito4 and
Alexei Sokolov1,4
Investigation of Carbonate-Based Copolymer Electrolytes for
Decoupled Li-Ion Conductivity
Broadband Dielectric Spectroscopy
VC-co-DEGMEMEA Copolymer
Fig. 4. The dielectric spectra versus frequencyat different temperatures for TS1-
198 (Li-TFSi) at few selectedtemperatures. There are four different spectra of
this sample: (a) real part of permittivity,(b) imaginarypart of permittivity,(c)
real part of conductivity,and (d) imaginarypart of conductivity.
CONTACTS
Weston Bell
Dr. Sokolov's Group, Department of Chemistry,
The University of Tennesse, Knoxville, TN, 37996, United States
Email: jbell54@vols.utk.edu
Proposed Approach
Motivation
Fig.1. General representationof Dielectric spectra versus frequency.
RESULTS
Ø Low Li conductivity in polymers hinders their broad adoption in current
technologies
Ø Based on previous research [1], present work analyzes the relationship
between ionic transport and the concentration of LiTFSi in a copolymer
matrix
Ø Previous research [1] indicates a limit to the increase in conductivity
based on salt concentration
Ø The Random Barrier Model [2] and Electrode Polarization models [3]
reveal strong deviation of Li ion transport from ideal behavior.
Ø The dielectric spectra was collected in the frequency range of 10-1 – 107
Hz using Novocontrol system which includes an Alpha-A Impedance
Analyzer and Quantro Cryosystem temperature control unit.
Ø These samples were measured using a parallel-plate configuration
dielectric cell made of invar and sapphire which is describe with ref [5].
Separation between the electrodes is 47 micrometers which yielded a
geometrical capacitance of 21 pF
Above: Fig. 2. Polymer TSI-198
Right: Fig. 3. Salt LiTFSi
Ø Sample 11% wt. VC and 89% wt. DEGMEMEA with glass transition
temperature of 243 K
Fig. 7. Diffusivityspectra versus 1000/T of sample according two our two
models; Electrode Polarization[3] and Random Barrier [2]
Ion Diffusivity
Ø Dyre’s Random Barrier Model – describes ion hopping within
randomly varying energy barriers. It relates the ion diffusion D to the
ion jump length λ and characteristic time of a jump τmax that can be
defined from the conductivity spectra σ(ω), and shown with ref [4].
!!
σ *
(ω)=σ0
iωτmax
ln(1+iωτmax
)
⎡
⎣
⎢
⎤
⎦
⎥
ε*
(ω) = εB +
ΔεEP
1+ iωτEP
Ø Electrode Polarization Model – as ions accumulate near electrodes, an
additional polarization process appears in the dielectric spectra as an
Electrode Polarization effect. It can be analyzed as tan(δ), and D can be
estimated from the amplitude and frequency of tan(δ), and the sample
thickness L, all shown with ref [3].
Assumptions
Ø Cations and anions carry the
same amount of charge
Ø Ions have equal diffusivity
Ø Sample thickness is much
larger than the Debye length
!!
D =
< λ2
>
2τmax
!!
D =
2π fmax
L2
32(tanδ )max
3
Ø The necessity of alternative energy in the face of climate change creates
an opportunity to develop batteries to store excess energy for later use
Ø Use of Solid Polymer Electrolytes (SPE) instead of traditional liquid
electrolytes can substantially improve safety and performance of
batteries, including increase in the energy density
Ø Conductivity of 10-3 S/cm2 at room temperature is required for many
batteries applications. Current SPEs cannot provide so high
conductivity,and fundamental understanding of ionic conductivity in
polymers is required for development of advanced SPE.
Name VC
(mol%)
DEGMEMEA
(mol%)
VC
(wt%)
DEGMEMEA
(Wt%)
TG
(˚C)
σ
(S/cm2)
TW1-55D 48 52 30 70
TW1-56F 38 62 22 78
TW1-56G 76 24 59 41
TS1-198 21 79 11 89 -30.6
TS2-118 53 47 34 66 -21
Table 1. Future work based on varying concentrations of VC and DEGMEMEA
Diffusivity
Fig. 6. Conductivityspectra versus Tg/T of each sample.
Conductivity for TG/T
Fig. 5. The conductivityspectra versus 1000/T of each sample. The ion transport
of 10% ion concentrationis conductingfaster comparedto the other
concentrations.
Conductivity for 1000/T