Abstract
This comparative work studies the self-enforcing heterogeneity of lithium deposition and dissolution as the cause for dendrite formation on the lithium metal anode in various liquid organic solvent based electrolytes. In addition, the ongoing lithium corrosion, its rate and thus the passivating quality of the SEI are investigated in self-discharge measurements. The behavior of the lithium anode is characterized in two carbonate-based standard electrolytes, 1 M LiPF6 in EC/DEC (3 : 7) and 1 M LiPF6 in EC/DMC (1 : 1), and in two alternative electrolytes 1 M LiPF6 in TEGDME and 1 M LiTFSI in DMSO, which have been proposed in the literature as promising electrolytes for lithium metal batteries, more specifically for lithium/air batteries. As a result, electrolyte decomposition, SEI and dendrite formation at the lithium electrode as well as their mutual influences are understood in the development of overpotentials, surface resistances and lithium electrode surface morphologies in subsequent lithium deposition and dissolution processes. A general model of different stages of these processes could be elaborated.
Highlights
The lithium metal anode provides a very high capacity and the lowest potential of all metallic anode materials.[1,2,3] it is used in commercial primary lithium metal batteries, but is proposed as an anode material in rechargeable lithium/air[4,5] and lithium/sulfur batteries, which are considered as super-high specific energy accumulators of tomorrow
The positive potentials of the Li working electrode (WE) against the Li/Li+ reference electrode (RE) represent the overpotentials appearing during lithium dissolution, whereas the negative potentials represent the overpotentials during lithium deposition on the WE
This experiment shows that the overpotentials of both the lithium deposition and dissolution processes strongly decrease under repeated cycling
Summary
The lithium metal anode provides a very high capacity and the lowest potential of all metallic anode materials.[1,2,3] it is used in commercial primary lithium metal batteries, but is proposed as an anode material in rechargeable lithium/air[4,5] and lithium/sulfur batteries, which are considered as super-high specific energy accumulators of tomorrow. Apart from the large extent of electrolyte decomposition and SEI film formation in the TEGDME- and DMSO-based electrolytes, the comparison of the results point at a self-enforcing heterogeneity of lithium deposition and dissolution according to the model in Fig. 3a and b in all investigated electrolytes.
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