How Does Nanoscale Crystalline Structure Affect Ion
Transport in Solid Polymer Electrolytes?
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Abstract
Polymer
electrolytes have attracted intensive attention due to
their potential applications in all-solid-state lithium batteries.
Ion conduction in this system is generally considered to be confined
in the amorphous polymer/ion phase, where segmental relaxation of
the polymer above glass transition temperature facilitates ion transport.
In this article, we show quantitatively that the effect of polymer
crystallization on ion transport is twofold: structural (tortuosity)
and dynamic (tethered chain confinement). We decouple these two effects
by designing and fabricating a model polymer single crystal electrolyte
system with controlled crystal structure, size, crystallinity, and
orientation. Ion conduction is confined within the chain fold region
and guided by the crystalline lamellae. We show that, at low content,
due to the tortuosity effect, the in-plane conductivity is 2000 times
greater than through-plane one. Contradictory to the general view,
the dynamic effect is negligible at moderate ion contents. Our results
suggest that semicrystalline polymer is a valid system for practical
polymer electrolytes design