All solid-state rechargeable alkali-ion batteries are a safer, potentially more energy dense architecture for energy storage. The crucial enabling component is the non-flammable alkali superionic conductor solid electrolyte, which must possess high alkali ionic conductivity, excellent phase stability, electrochemical and mechanical compatibility with the electrodes, and ideally, stability under ambient air. Despite recent advances, the total number of known alkali superionic conductors remain relatively small, and most have significant compromises. In this talk, we will propose several promising novel alkali superionic conductor solid electrolytes - Li₃Y(PS₄)₂ and Li₅PS₄Cl₂ - identified using an efficiently-tiered first principles screening approach. These candidates are inspired by the observation that many known alkali superionic conductors have analogues in the silver thiophosphate chemical space (e.g., Li₇P₃S₁₁, the Li₆PS₅X argyrodites, etc.). We will also present evidence that these candidates may potentially have a better balance of properties, especially with regards to phase and electrochemical stability, compared to current state-of-the-art superionic conductors such as Li₁₀GeP₂S₁₂, Li_9.54Si_1.74P_1.44S _11.7Cl_0.3 and Li₇P₃S₁₁.