Lithium metal is among the most sought-after anode chemistries for next-generation electrical energy storage due to its high theoretical capacity (3860mAhg−1) and low reduction potential (− 3.04V vs S.H.E.). To realize its promise, reactive Li anodes must be paired with high-energy conversion cathodes, such as sulfur or oxygen. Chemical and physical instability at both electrodes pose formidable challenges to development of practical lithium metal batteries. These instabilities are compounded by problems with active material loss and anode passivation when Li is paired with conversion cathodes, such as elemental sulfur. Here, we report on design principles and a process for creating artificial solid electrolyte interphases composed of ionic shields that are able to stabilize electrochemical processes at both the anode and cathode of Li-S electrochemical cells. We show that ASEI composed of negatively-charged nanoparticles on Li stabilize deposition of Li at the anode by multiple fundamental mechanisms. A similar concept is used to design interphases composed of positively charged conductive nanoparticles at the cathode and shown to be effective at intercepting dissolved polysulfide anions and for enhancing sulfur reutilization. We combine the two ASEI design strategies to create Li-S cells based on high-loading sulfur cathodes and demonstrate their long-term cycling stability.