Abstract
Thin layers containing lithium oxide (Li2O), lithium sulfide (Li2S), or lithium selenide (Li2Se) are relevant for many electrochemical processes in lithium-based batteries. As a step toward understanding the electrochemical properties of such layers, this work demonstrates the growth of dense single-phase films by both sputter deposition (for Li2O and Li2S) and thermal evaporation (for Li2S and Li2Se). The dependence of morphology and grain size on the growth conditions is characterized. Reactive deposition is found to be faster and more practical than direct deposition, and both sputtered S8 and heated SnS2 are shown to be viable sulfur precursors for growing sulfides. These results enable the preparation of Li2O, Li2S, and Li2Se films suitable for future electrochemical studies. An initial set of conductivity data from an evaporated Li2S film is also presented.
Highlights
The compounds lithium oxide (Li2O), lithium sulfide (Li2S), and lithium selenide (Li2Se) often form as thin layers in lithium-based batteries
Li2O is a common constituent of the solid-electrolyte interphase (SEI) passivation layer that can arise due to electrolyte reduction at the anode-electrolyte interface
Li2S is a common constituent of SEI layers in solid state batteries containing sulfide electrolytes
Summary
The compounds lithium oxide (Li2O), lithium sulfide (Li2S), and lithium selenide (Li2Se) often form as thin layers in lithium-based batteries. Analogous behavior is seen for lithium selenide in Li-Se battery electrodes, which are being explored for niche applications despite their potentially higher weight and toxicity.8 In all these systems, a rigorous electrochemical treatment of the transport kinetics will surely depend on understanding the behavior of Li2O, Li2S, and Li2Se in nanocrystalline layers. A rigorous electrochemical treatment of the transport kinetics will surely depend on understanding the behavior of Li2O, Li2S, and Li2Se in nanocrystalline layers To develop this understanding, it would be useful to study single-phase films of these materials, isolated from the complexity of a typical multiphase battery electrode. It should even be possible to systematically vary the film morphology, grain size, crystallographic orientation, and/or defect concentrations (at least to some extent) by varying the growth method and conditions The impact of these parameters on the electrochemical properties of Li2O, Li2S, and Li2Se could be assessed. A preliminary version of some of these results was included in the Ph.D. thesis of the first author.
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