Abstract:
Battery chemistries beyond lithium-ion such as sodium-ion batteries (SIBs) are becoming
popular these days due to the limited availability and high cost of lithium raw materials.
Designing suitable electrolytes is of critical importance for the development of SIBs.
PEO10LiClO4 is a very commonly used solid-polymer electrolyte (SPE) in secondary lithium ion batteries. It is quite generally accepted that replacing LiClO4 with NaClO4 in a SPE will
reduce the ambient temperature ionic conductivity, essentially due to the larger size of Na+
compared to that of Li+
. In this work, two SPEs PEO10LiClO4 and PEO10NaClO4, which are
Li+
and Na+
conducting respectively, were synthesized by using standard solvent-casting
method employing acetonitrile (CH3CN) as the solvent and characterized by using
experimental techniques such as EIS, CV, LSV and DC polarization to quantitatively compare
the effect of alkali-cations (Li+
and Na+
) on the electrochemical properties of these SPEs. Both
SPEs showed similar electrochemical properties except the ionic conductivity and the
activation energy values. Li+
and Na+
ion conducting SPEs showed an ambient temperature
ionic conductivity in the order of 10-4
and 10-5 S cm-1
, respectively, whereas the
electrochemical stability window obtained from the LSV and CV studies remained almost
equal (3 V) for both types of SPEs. DC polarization tests on SS/SPE/SS configuration showed
that both SPEs are dominantly ionic conductors with almost equal ionic transference numbers
(tion ~ 0.99) and negligible electronic conductivity. Ionic conductivity vs inverse temperature
followed Arrhenius behavior with activation energies of 0.48 and 0.62 eV (at 𝑇 ‹ 𝑇𝑚 )
respectively for Li+ and Na+
conducting SPEs. Higher activation energy of Na+
conducting
SPE agrees well with its lower conductivity in comparison to its Li+
counterpart.
