Lithium sulfide (Li₂S) is under intense study because it is the insulating discharge product of ultrahigh energy density lithium–sulfur (Li–S) batteries and a candidate cathode material for lithium-metal-free Li–S cells. In this work, we report the fabrication of an apparatus for sputter deposition of Li₂S films ranging in thickness from a few nanometers to several micrometers at rates over 2 nm min^–1. High-temperature annealing of the films is shown to produce crystalline films of high chemical purity Li₂S for the first time. We provide evidence via complementary X-ray photoelectron and Raman spectroscopy that sputter deposition produces a unique sulfide structure composed of polymer-like chains of Li₂S units. The electrochemistry of these films is markedly different from annealed crystalline Li₂S, which is shown to be electrochemically inactive. The full theoretical capacity of the as-deposited sulfide structure could be realized during galvanostatic charge, suggesting a facile, solid-state charge process. Finally, we explore trends in the plasma chemistry that lead to nonstoichiometry and depth inhomogeneity during Li₂S sputter deposition.

中文翻译：

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溅射沉积硫化锂薄膜的化学性质

硫化锂（Li ₂ S）受到了广泛的研究，因为它是超高能量密度锂硫（Li–S）电池的绝缘放电产物，也是无锂金属的Li–S电池的候选阴极材料。在这项工作中，我们报告了以2 nm min ^–1的速率溅射沉积Li ₂ S膜的设备的制造过程，该膜的厚度从几纳米到几微米不等。膜的高温退火被证明是首次产生具有高化学纯度的Li ₂ S的结晶膜。我们通过互补的X射线光电子和拉曼光谱提供了证据，表明溅射沉积产生了独特的硫化物结构，该结构由类似Li ₂的聚合物链组成S个单位。这些膜的电化学与退火的结晶Li ₂ S明显不同，后者显示出电化学惰性。沉积的硫化物结构的全部理论容量可以在恒电流充电过程中实现，这表明了一种简便的固态充电过程。最后，我们探讨了在Li ₂ S溅射沉积过程中导致化学计量不均和深度不均匀性的等离子体化学趋势。