Solid-state lithium-ion batteries (SSLIBs) can simultaneously improve both energy density and safety over current state-of-the-art lithium-ion batteries (LIBs). These critical advantages are expected to enable next generation battery-based energy storage for both commercial applications such as consumer devices and transportation and greater utilization of renewable energy technologies. The key component to SSLIBs is the solid-electrolyte, ideally allowing fast ion conduction, possessing electrochemical stability with metallic lithium to enable higher energy density, and exhibiting chemical stability under ambient conditions. Lithium conducting garnets, in particular doped lithium lanthanum zirconate (LLZO) possess all of these advantageous characteristics. While lithium garnets have demonstrated exceptional properties under laboratory conditions, only a few groups have demonstrated a robust, scalable process to integrate them into SSLIBs. Some of the main challenges to incorporating garnets such as LLZO are the relatively high processing temperatures required and brittle nature of devices based on these sintered polycrystalline ceramics. Processing schemes amenable to roll-to-roll type processing such as tape-casting have been demonstrated, but generally require very fine powders to produce thin electrolyte membranes and subsequently low cell resistance. However, lithium garnets are most commonly synthesized via solid-state reactions (SSR), generally requiring high temperatures (> 900 °C), long reaction times (often in excess of 8 h), and concomitant high energy cost. Further, the resultant particle sizes of LLZO synthesized via SSR are relatively large, and fine powders are only obtained after further processing via high energy milling. Molten salt synthesis (MSS) has recently been demonstrated as an alternative strategy to obtain phase-pure crystalline LLZO, with the added benefit of generally shorter reaction times (4 h or less), lower temperatures, and in some cases inherently submicron particle sizes, while maintaining expected high ionic conductivity. Design principles for formation of doped and co-doped LLZO are discussed, wherein salt and reagent composition have direct effects on the formation temperature, particle size, particle size distribution, and electrochemical performance of the as-synthesized material. By engineering inherently fine LLZO powders, a more direct route to practical processing methods such as tape-casting becomes accessible. As such, MSS may prove to be a crucial method to allow LLZO and SSLIBs based on it to transition to a scalable solution for safer, more efficient battery-based energy storage.