Formation of lithiated gold and its use for the preparation of reference electrodes \u2014 an EQCM study

Christopher Behling,Karl J J Mayrhofer,Balázs B Berkes

doi:10.1007/s10008-021-05060-3

Abstract

Lithiated gold wires can be used to build reference electrodes with outstanding potential stabilities over several days and even over the course of one year. These electrodes are well suited for investigations in the context of lithium-ion batteries (LIBs). In this work, a detailed procedure for the preparation of such electrodes with tailored mechanical properties, which can be fitted gastight into electrochemical cells using commercially available fittings, is given. The electrochemical lithiation process is studied using the electrochemical quartz crystal microbalance (EQCM) technique, and the differences in lithiation of wire type and thin film type gold electrodes are discussed. All experiments were carried out with two different electrolytes, namely, a LiPF6 and a lithium bis(trifluoromethane sulfonyl) imide (LiTFSI)-based electrolyte, and we conclude that for a higher lithiation rate and long-term stability, the use of LiTFSI-based electrolyte in the preparation phase is beneficial. The EQCM data provides a better insight in the analysis of film formation processes, like the buildup of the solid electrolyte interphase (SEI) during the lithiation, the rate of deposition of metallic lithium, or additional information on the kinetics of Li-Au alloy formation.

Highlights

Lithium-ion batteries (LIBs) represent the most important achievement among modern electrochemical energy storage devices that fundamentally changed our society through portable electronics and electric vehicles
Preparation and testing of the PEEK embedded lithiated gold wire reference electrodes Based on previous lithiation experiments from the literature [11, 14], 200 μA·cm−2 current density was used to lithiate a gold wire with 250 μm outer diameter
Switching to a lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) based electrolyte, which is widely used for lithiation experiments [14, 20, 21], and trying different current densities only slightly changed the shapes of the E − t curves, and well-pronounced plateaus could not be observed

Summary

Introduction

Lithium-ion batteries (LIBs) represent the most important achievement among modern electrochemical energy storage devices that fundamentally changed our society through portable electronics and electric vehicles. Li reference electrodes that can be used in a huge variety of electrochemical cells to study nonaqueous systems, especially LIBs. The battery electrolytes LiPF6 (1 mol·L−1 in EC:EMC, 3:7 by wt.) and LiTFSI (1 mol·L−1 in EC:EMC, 3:7 by wt.) used for the experiments were bought from E-Lyte Innovations GmbH (Münster, Germany).

Results

Conclusion