Understanding the Impacts of Li Stripping Overpotentials at the Counter Electrode by Three-Electrode Coin Cell Measurements

Abstract

The evaluation of new materials, interfaces, and architectures for battery applications are routinely conducted in two-electrode coin cell experiments, which although convenient, can lead to misrepresentations of the processes occurring in the cell. Few three-electrode coin cell designs have been reported, but those which have involve complex cell assembly, specialized equipment, and/or cell configurations which vary drastically from the standard coin cell environment. Herein, we present a novel, facile three-electrode coin cell design which can be easily assembled with existing coin cell parts and which accurately reproduces the environment of traditional coin cells. Using this design, we systematically investigated the inaccuracies incurred in two-electrode measurements in both symmetric/asymmetric cells and half-cell experiments by galvanostatic charge/discharge, galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. From our investigation, we reveal that lithium metal stripping contributes larger overpotentials than its nucleation/plating processes, a phenomenon which is often misinterpreted in two-electrode cell measurements.

Assessing Coulombic Efficiency in Lithium Metal Anodes

“…This extra capacity is responsible for reducing the observed nucleation overpotential in the ZnO-coated electrode compared to the uncoated Ni electrode. Note that the nucleation overpotential is dominated by the working electrode in the second half-discharge cycle, unlike the first half-cycle, which should account for a true nucleation overpotential of the system, in line with our previous report and the report by Seok et al These results collectively indicate that the origin of the nucleation overpotential is largely overlooked as an indicator of the energy required to form the lithium nucleation, leading to misguided data interpretation.…”

“…Once the plating starts, the counter electrode potential experiences a gradual decrease until a stable state is reached, which appears in the overall potential during the lithium deposition process. The surface area associated with the creation of pits on the surface of lithium metal continues to increase on the counter electrode during the process, resulting in decreasing potential of the counter electrode and overall cell polarization. , It means that the energy necessary to activate lithium stripping at the lithium metal counter electrode is much higher than that necessary for forming nucleation sites on the working electrode. In conclusion, there is no correlation between the nucleation overpotential and the performance of the batteries since the so-called nucleation overpotential simply does not correspond to the effective activation energy for the formation of lithium metal plating nuclei.…”

On the Road to Stable Electrochemical Metal Deposition in Multivalent Batteries

“…Therefore, recent metal anode research is focused on unveiling the dendritic metal growth mechanism and inhibiting dendritic deposition. However, most of the research on deposition/stripping in metal anodes has been focused mainly on Li metal. − Moreover, the few existing studies on the multivalent metal anodes are conducted based on the known dendritic Li growth mechanism, which is not yet fully understood. One major obstacle for multivalent metal anodes mechanism research is that the metal anode battery system in each metal is distinct (Figure ).…”

New Insights into the Behaviour of Commercial Silicon Electrode MaterialsviaEmpirical Fitting of Galvanostatic Charge‐Discharge Curves

“…This shows how the EIS changes depending on the potential, with the spectrum at 0.07 V in particular showing a very large impedance loop due to the Li (CE). [1,24,31] Figure 1c shows an example of one of the C/3 cycles in Figure 1a after baseline subtraction against the potential (vs Li/Li + ). The orange line denotes the fit of Eq.…”