Comparison of Lithium Diffusion Coefficient Measurements in Tellurium Electrodes via Different Electrochemical Techniques

Abstract

Both thin (55 μm) composite and thick (350 μm) all active material battery porous electrodes were prepared for estimating the diffusion coefficient of Li+ ( D Li + ) in tellurium (Te) during electrochemical lithiation. Galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were applied to quantify the chemical lithium solid-state diffusion coefficient within the Te active material in the electrodes. Multiple methods of GITT and EIS were assessed. For the composite Te electrodes, the D Li + was on the order of 10−11 cm2 s−1 from both CV and GITT methods, but 10−9 cm2 s−1 from EIS. For the thick tellurium electrodes, both GITT and EIS resulted in lithium diffusion coefficient estimates in the range of 10−11–10−12 cm2 s−1. The general trend across all methods that quantified the diffusion coefficient as a function of lithiation of tellurium was that the D Li + decreased rapidly when the Te material was initially lithiated. The D Li + at the phase transition voltage plateau (∼1.7 V, vs Li/Li+, where both Te and Li2Te were expected) had the lowest D Li + , while the D Li + both before and after the plateau was generally higher. Among all the electrochemical measurements of D Li + , the modified GITT method with modelling the relaxation region resulted in relatively low scatter in the data, provided values as a function of lithiation, and was well suited to thick electrodes with a flat discharge plateau as was the case herein.