Electrolyte‐Free Spectroscopy and Imaging of Graphite Intercalation

Abstract

Engineering electrode materials for optoelectronic and energy storage applications requires a fundamental understanding of intercalation using spatially‐resolved techniques. However, spectroscopic methods can have limited spatial resolution and low intensity since the signal passes through electrolyte. Here, a device geometry is presented in which the electrolyte is laterally separated from the area probed spectroscopically, so that the signal does not pass through the electrolyte. This geometry enables us to visualize ion transport with optical microscopy and monitor charge transfer with Raman and visible reflectance spectroscopies. In addition, vibrational changes are probed in the mid‐IR, a region previously difficult to access due to electrolyte absorption. This geometry will allow many layered electrodes to be probed in situ using time‐ and spatially‐resolved techniques, including photon and electron spectroscopies.

A transient component of the solid electrolyte interphase in the Li-ion battery

“…6†). 25,26 By comparing the work functions of the thermally lithiated HOPG and the electrochemically cycled one we can conclude that the E WE = 0.01 V sample (point E in Fig. 2) corresponds to the LiC 12 stage, while all other samples correspond to the diluted stage or below.…”

“…In order to overcome this uncertainty and understand the stage of the measured samples, we prepared a Li x C 6 sample by thermal intercalation of metallic Li into HOPG. The sample cleaved using Scotch tape several times exposed fresh surfaces with different coexisting stages distinguished by colors 24,25 and work functions (Fig. 4).…”