Due to ever‐increasing concern about safety issues in using alkali metal ionic batteries, all solid‐state batteries (ASSBs) have attracted tremendous attention. The foundation to enable high‐performance ASSBs lies in delivering ultra‐fast ionic conductors that are compatible with both alkali anodes and high‐voltage cathodes. Such a challenging task cannot be fulfilled, without solid understanding covering materials stability and properties, interfacial reactions, structural integrity, and electrochemical windows. Here in this work, we will review recent advances on fundamental modeling in the framework of material genome initiative based on the density functional theory (DFT), focusing on solid alkali batteries. Efforts are made in offering a dependable road chart to formulate competitive materials and construct “better” batteries.

Development of non-flammable solid electrolytes is necessary for sodium ion batteries, so that a sustainable battery technology can be extensively exploited for large scale energy storage when safety is of utmost importance.

Even though ultra-fast Li+ ion conductors based on sulfides such as LGPS and Li6PS5Cl have been developed in recent years, rather limited advancement has been made towards developing all-solid-state lithium ion batteries due to serious interface-related problems.

It is very important and yet extremely challenging to develop solid-state electrolytes for safe sodium ion batteries, largely due to sodium ions being significantly larger than lithium ones.

The argyrodite sulfides are getting more and more attractive as highly promising solid-state electrolytes (SSEs) for high-performance all-solid-state batteries (ASSBs), owing to their high ionic conductivity, adequate plasticity, and decent mechanical strength.However, their poor incompatibility with Li metal anode and high voltage cathodes and as well as serious sensitivity to air significantly hinder their practical applications. Herein, we have devised an effective strategy to overcome these challenging shortcomings through modification of chalcogen chemistry under the guidance of theoretical modeling. The resultant Li6.25PS4O1.25Cl0.75 delivered excellent electrochemical compatibility with both pure Li anode and high-voltage LiCoO2 cathode, without detrimental impact upon the superb ionic conductivity of the pristine sulfide. Furthermore, the current SSE also exhibited highly improved stability to oxygen and moisture in air, with further advantage being more insulating to electrons. The remarkably enhanced compatibility with electrodes is attributed to in situ formation of solid anode electrolyte interphase (AEI) and cathode electrolyte interphase (CEI) layers. The formation of in situ AEI enabled ultra-stable Li plating/stripping at a record high current density up to 1 mAh cm -2 in Li|Li6.25PS4O1.25Cl0.75|Li symmetric cells over 1800 hours. The in situ CEI facilitated protection of the SSE from decomposition at elevated voltage. Consequently, the synergistic effect of AEI and CEI helped the LiCoO2|Li6.25PS4O1.25Cl0.75|Li battery cell to achieve markedly better cycling stability than that using the pristine Li6PS5Cl as SSE, at a high areal loading of the active cathode material (4 mg cm -2 ). This work adds a desirable SSE in the argyrodite sulfide family, so that highperformance solid battery cells could even be fabricated in ambient air.