Abstract
Lithium sulfide-based materials have been considered as potential positive electrodes for the next generation batteries. Lithium sulfide is the fully lithiated form of sulfur, i.e., they share the same high theoretical capacity. However, it has the benefit of already containing lithium, which allows making cells with lithium-free negative electrodes. Lithium sulfide, however, shares with sulfur the polysulfide dissolution drawback upon cycling. One possible solution to this problem is to envelop the active material particles with carbonaceous materials. In this work, we investigate the effect of a nitrogen-rich carbon coating on lithium sulfide particles. The effect of such coating on the surface properties and electrochemistry of lithium sulfide cathodes is investigated in details, in particular, regarding its interaction with fresh vs. aged electrolyte. The polymerization of dioxalane (DOL) due to aging is found to affect the electrochemistry of lithium sulfide and, interestingly, to improve the cycling performance.
Highlights
Lithium-sulfur batteries (LSBs) have attracted much attention in recent years, with the prospect of replacing lithium-ion batteries (LIBs) as energy source for automotive and, especially, flight applications as soon as 2030 (International and Agency, 2018)
Ethylenediamine-embedded lithium sulfide, previously reported by our group (Lodovico et al, 2019), is pyrolized in order to obtain carbon-coated lithium sulfide, with the ethylenediamine molecules serving as the carbon source
The use of this kind of diamine lead to a N-doped carbon coating with C:N weight ratios around 2:1. The effect of such coating on the surface properties and electrochemistry of lithium sulfide cathodes is investigated in details, in particular, regarding its interaction with fresh vs. aged electrolyte
Summary
Lithium-sulfur batteries (LSBs) have attracted much attention in recent years, with the prospect of replacing lithium-ion batteries (LIBs) as energy source for automotive and, especially, flight applications as soon as 2030 (International and Agency, 2018). Carbon coating of sulfur is all but trivial, owing to its low melting point and tendency to sublimate at moderate temperature In these terms, the use of lithium sulfide as cathode active material presents interesting advantages. Ethylenediamine-embedded lithium sulfide, previously reported by our group (Lodovico et al, 2019), is pyrolized in order to obtain carbon-coated lithium sulfide, with the ethylenediamine molecules serving as the carbon source The use of this kind of diamine lead to a N-doped carbon coating with C:N weight ratios around 2:1. The effect of such coating on the surface properties and electrochemistry of lithium sulfide cathodes is investigated in details, in particular, regarding its interaction with fresh vs aged electrolyte. It was found that upon prolonged storage (12+ months) the dioxolane-based electrolyte tends to polymerize, which greatly affects the behavior of Li2S-based cathodes
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