Instrumentation for tracking electrochemical reactions by x-ray photoelectron spectroscopy under conventional vacuum conditions

Abstract

A bias application system for tracking electrochemical reactions by x-ray photoelectron spectroscopy (XPS) is constructed using a laboratory-based apparatus. A specialized sample holder and stage with three electrical terminals provide contacts to a potentio-galvanostat on the outside, allowing bias application to an electrochemical device in the analysis chamber under vacuum conditions. The application of a direct current bias voltage to the sample holder is confirmed using metal Au samples. The Au 4f peaks from the Au grounded to the analyzer are identical, while those from the Au insulated from the analyzer shift due to the applied bias voltage. Furthermore, galvanostatic lithiation/delithiation processes and in situ XPS measurements are performed on a Si thin-film electrode after transferring the sample into the XPS apparatus without exposure to open air using a newly developed transfer vessel. After the initial lithiation process, a Li 1s peak containing a lithium-silicide component appears, and the Si 2p peaks shift to a lower binding energy due to the lithiation of the Si electrode. After the subsequent delithiation process, the Si 2p peak from the lithium silicide partially shifts back to a higher binding energy. As a result, in situ XPS measurements of the lithiation/delithiation reactions are successfully performed using the developed system.