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Ternary Poly(ethylene oxide)/Poly(l,l‑lactide) PEO/PLA Blends as High-Temperature Solid Polymer Electrolytes for Lithium Batteries
journal contribution
posted on 2021-11-30, 09:35 authored by Jorge
L. Olmedo-Martínez, Luca Porcarelli, Gregorio Guzmán-González, Itxaso Calafel, Maria Forsyth, David Mecerreyes, Alejandro J. MüllerLithium batteries
are in high demand in different technological
fields. However, the operating temperature is required to be below
70 °C, and this limits their use in applications demanding high-energy
rechargeable batteries that are able to operate at temperatures above
100 °C. Poly(ethylene oxide) (PEO) is, currently, the reference
solid polymer electrolyte (SPE) employed in solid-state lithium batteries.
However, the application of PEO at higher temperatures is restricted
due to the loss of mechanical properties. In this article, we show
that the polymer blending strategy of blending PEO with poly(l,l-lactide) (PLA) allows extending its use in batteries
at high temperatures (100 °C). This improvement is due to the
mechanical reinforcement of PEO solid electrolytes associated with
the presence of PLA crystals. Thus, two solid electrolyte systems
based on PEO/PLA blends with either a LiTFSI salt or a lithium single-ion
polymer (poly(lithium-1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethanesulfonyl)imide),
PLiMTFSI) were investigated and compared. Differential scanning calorimetry
(DSC) results indicate that regardless of the concentration of LiTFSI
or PLiMTFSI in the blend, crystals of PLA are present with melting
peaks at 160–170 °C and the lithium salt distributes preferentially
in the PEO-rich amorphous phases. The ionic conductivity is negatively
affected by the incorporation of PLA in the blends. However, at high
temperatures (>70 °C), ionic conductivities of ∼10–4 S cm–1 were obtained for both systems.
DMTA results showed that PLA addition increases the mechanical properties
of the electrolytes, yielding storage modulus values of ∼106 Pa for the PEO/PLA/LiTFSI blend and ∼107 Pa or higher for the PEO/PLA/PLiMTFSI blend at high temperatures
(100 °C). Finally, both ternary blends were compared in a symmetrical
lithium battery at 100 °C, and the single-ion conducting PEO/PLA/PLiMTFSI
system presented lower overpotentials, which is reflected in a lower
polarization inside the lithium battery.
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rich amorphous phaseslower polarization insidedifferential scanning calorimetrydifferent technological fields70 ° c100 ° cdmta results showedenergy rechargeable batteries7 sup6 suppoly ( lithiumsymmetrical lithium batterypolymer blending strategypoly ( lpla addition increasesapplications demanding highstate lithium batteriesion conducting peol ‑ lactidelithium batteryion polymerternary polyresults indicateblending peolithium single∼ 10operating temperaturenegatively affectedmelting peaksmechanical reinforcementmechanical propertiesionic conductivityhigh demandallows extending