Since Li-ion batteries (LIBs) have been commercialized in the early 1990s, LIBs have become popular power sources for portable electronics due to their high gravimetric and volumetric energy density. Recently, the use of Li-ion batteries has been extended to large scale applications such as electric vehicles (EVs) and energy storage systems. For powering electrical vehicles, LIBs require high gravimetric and volumetric energy density, superior safety, and low cost. To meet these requirements in LIBs, there are several approaches. Among them, the use of S as a cathode material can be a very promising approach because sulfur can achieve 4 ~ 5 times higher energy density than conventional cathode materials such as LiCoO₂ and is abundant and then cheap. However, the use of S needs the source of Li in a cell such as Li-metal or lithiated materials as an anode material. For example, the use of Li metal in Li-S cell is not trivial because of not only serieous safety issues origianted from the dendritic growth of Li but also poor couloumbic efficiency that can require excess amount of Li metal. The excess amount of Li metal under a limited cell volume needs additional sapce for Li metal leading to poor volumetric energy density. This requirement can make a limited utilization of Li-S.

As an alternative approach, Li₂S can be considered as a cathode material for Li-S cell. Li₂S as a cathode can achieve a little lower energy density than S but still higher than the conventional electrode materials. Moreover, the use of Li₂S can extend the choice of anode materials from a graphite to a silicon to Li metal without any limitations because large amount of available lithium ions can be provided from Li₂S. When Li metal as a anode material in the same volume of the Li₂S cell can be used, the required space for Li metal in the Li₂S cell will be decreased compared to Li-S cell because of additional Li can be provided from Li₂S. Less required space for Li metal in the Li₂S cell implies that additional Li₂S in the saved space can be loaded and then volumetric energy density can be increased.

In this talk, we will discuss the use of Li metal as an anode material in Li₂S cell and the factors affecting the nucleation and growth of Li metal on the electrode. Furthermore, we will talk about electrochemical performances of Li₂S full cell at different conditions of Li metal.