Operando Raman Spectroscopy for Evaluating Concentration Changes in Li- and Na-Based Solid Polymer Electrolytes

Abstract

The solid polymer electrolytes (SPEs) can apply to all-solid-sate batteries using various cations as the carrier species. Herein, we performed operando Raman spectroscopy to evaluate the concentration changes with ionic transport in the Li- and Na-based SPEs composed of ether-based host polymer and MN­(SO2CF3)2 (M = Li, Na; MTFSA), with the aim of extracting differences in behavior under electrochemical operation. In the [Li | Li-based SPE | Cu] cell, the integrated intensities of TFSA anions changed near the working electrode (WE) and counter electrode (CE) sides during cyclic voltammetry measurements, revealing changes in the anion concentration. Then, operando Raman spectroscopy was conducted for the [M | Li- or Na-based SPE | M (M = metallic Li or Na)] symmetric cells during chronoamperometry measurements. The cell using Li-based SPE exhibited increasing and decreasing integrated intensities for TFSA at the WE and CE sides, respectively, before reaching a steady state. In contrast, the integrated intensities of TFSA required a longer time to reach a steady state in the Na-based SPE system, suggesting that the solvation/desolvation of Na+ is more difficult during ionic transport. Overall, operando Raman spectroscopy contributed to elucidating the differences in ionic transport properties between Li- and Na-based SPEs during electrochemical processes.

Roles of Hydrogen Bonds in Ionic Conductivity in the LiNO3–Poly(vinyl alcohol) Electrolyte: A Real-Time Raman Spectroscopic Study

“…While these effects can be detrimental to ion conduction, the polymer can facilitate conduction through its segmental motion and above the glass transition temperature. ,, These factors can be studied using Raman spectroscopy from the chemical and structural changes of the molecules. Raman spectroscopy has been used to determine the crystallinity of polymer and salt, , to analyze their solvation shell structure/complexation, , to perform operando analysis to detect changes in ion concentration as well as to monitor the electrode/electrolyte interface . To correlate the properties of the polymer electrolyte with the behavior in electrochemical cells in real time, mock cells with transparent glass covers have been employed for use in Raman spectroscopic characterizations under the same conditions. , …”

In-Situ Raman Spectroscopic Analysis of Factors Improving Discharge Rate Capability of Na-Ion Batteries with FSA-Based Ionic Liquids

“…In a previous study, in-situ Raman spectroscopy was employed to investigate the behavior of batteries using Li and Na electrolytes. 31 By utilizing the relationship between concentration changes and peak shifts in the Raman spectra, the diffusion properties of Na + and Li + were compared in solid polymer electrolytes, which revealed that solvation/desolvation of Na + by TFSA ¹ (TFSA = bis(trifluoromethylsulfonyl)amide) during ionic transport is more difficult than the case of Li + .…”

Interfacial modification of NaCoO2 positive electrodes with inorganic oxides by simple mixing and the effects on all-solid-state Na batteries

“…To enhance safety, there has been increasing interest in all-solidstate batteries that leverage non-ammable and non-volatile solid electrolytes, such as sulde, oxide, and organic polymer materials, as alternatives to organic liquid electrolytes. [10][11][12][13][14][15][16][17] In addition, all-solid-state batteries can be stacked within a single external package without the risk of liquid short-circuiting. This approach is effective for improving both energy density and safety properties.…”