Lithium sulfur batteries have been studied intensively because of their potential to create high specific energies that meet accepted targets for mobile and stationary storage. Substantial efforts have been devoted to improve the electron/ion conductivity of the sulfur cathode, to suppress dissolution of polysulfide; and to limit parasitic reactions of polysulfide with lithium. Less consideration has addressed the interface stability of lithium, which is critical for long-term stability of cells that utilize high sulfur loadings and minimal electrolyte volume to maximize overall specific energy. Recent emphasis on all solid-state batteries underscore the important role well-formed interphases must play in achieving high material utilization at practical rates. We prospect that advances towards practical Li-S cells will come from strategies for creating durable interphases on lithium that limit active material and electrolyte loss and which provide greater flexibility in electrolyte design.