In Situ X-ray Absorption Spectroscopic Investigation of the Capacity Degradation Mechanism in Mg/S Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 30932498.
- Also identified by DOI 10.1021/acs.nanolett.8b05208.
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Abstract
The Mg/S battery is attractive because of its high theoretical energy density and the abundance of Mg and S on the earth. However, its development is hindered by the lack of understanding to the underlying electrochemical reaction mechanism of its charge-discharge processes. Here, using a unique in situ X-ray absorption spectroscopic tool, we systematically study the reaction pathways of the Mg/S cells in Mg(HMDS)<sub>2</sub>-AlCl<sub>3</sub> electrolyte. We find that the capacity degradation is mainly due to the formation of irreversible discharge products, such as MgS and Mg<sub>3</sub>S<sub>8</sub>, through a direct electrochemical deposition or a chemical disproportionation of intermediate polysulfide. In light of the fundamental understanding, we propose to use TiS<sub>2</sub> as a catalyst to activate the irreversible reaction of low-order MgS <sub>x</sub> and MgS, which results in an increased discharging capacity up to 900 mAh·g<sup>-1</sup> and a longer cycling life.