In a solid-state lithium-metal/sulfur-based battery cell, barriers to sulfur and polysulfide diffusion are included in or used as an ionically conductive electrolyte in the cathode or separator layers. During operation of the battery, the barrier materials are positioned to either 1) rapidly react with any free sulfur or lithium polysulfide species that are generated, forming stable carbon-sulfur bond(s) and preventing further migration of the sulfur or polysulfide species or 2) prevent the formation and diffusion of elemental sulfur or free lithium polysulfide species. Regardless of the identity of the sulfur/polysulfide species, the sulfur-containing species is prevented from diffusing to the anode and causing capacity fade and higher internal resistance to ion flow.