Abstract
To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process. Herein, real-time Li-ion transition behavior and transport dynamics in typical poly(vinyl alcohol)/LiClO4 electrolytes under an external EF have been studied by combining time-resolved Fourier transform infrared (FTIR) with two-dimensional correlation FTIR spectroscopy. Results show that no migration of Li-ions has been detected when the time scale of the EF loading is at nanosecond (less than 200 ns). However, for the first time, Li-ions have been found to significantly transfer along the EF direction as the time scale enhances to microsecond order of magnitude and the migration period is less than 10 microseconds. The Li+ migration in the SPEs under an EF is a complicated process including quasi-periodic dissociation and coordination effects between Li-ion carriers and polymeric chains.
Highlights
Results and DiscussionThe intensity of the characteristic peak have been found to alternately increase (9.5–10.0 and 10.7–13.2 μs, positive) and decrease (10.2–10.7 and 13.5–16 μs, negative) with loading time, showing that Li-ions have periodically migrated along the direction of potential reduction by alternately dissociating and coordinating with the macromolecular ligands (lone pairs of the hydroxyl groups), and that the time scale for a critical migration of Li-ions in such poly(vinyl alcohol) (PVA)-LiClO4 electrolyte is at microsecond order of magnitude instead of other time scales (e.g. nanosecond, millisecond, even second)
To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process
Both the ionic transition behavior and the transport dynamics of solid poly(vinyl alcohol) (PVA)/LiClO4 electrolytes are extensively studied for the first time by using a combination of the TR-Fourier transform infrared (FTIR) and 2D-COR FTIR technique under an EF, in which the time after loading the EF is considered as the perturbation (t = 0, nanoseconds, microseconds, and milliseconds)
Summary
The intensity of the characteristic peak have been found to alternately increase (9.5–10.0 and 10.7–13.2 μs, positive) and decrease (10.2–10.7 and 13.5–16 μs, negative) with loading time, showing that Li-ions have periodically migrated along the direction of potential reduction by alternately dissociating and coordinating with the macromolecular ligands (lone pairs of the hydroxyl groups), and that the time scale for a critical migration of Li-ions in such PVA-LiClO4 electrolyte is at microsecond order of magnitude instead of other time scales (e.g. nanosecond, millisecond, even second). The maximum time internal of the peak platform gradually decreases from 2 to 1.4 and to 0.8 μs when the original OH/Li ratio changes from 10/1 to 8/1 and to 6/1
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