All-Solid-State Lithium Batteries (ASSLBs) are a new generation of lithium batteries that is developed to meet high expectations in terms of safety, stability and high energy density. The liquid electrolyte of conventional Li-ion batteries is replaced in ASSLBs by a safer and more stable solid electrolyte (SE). These solid electrolytes must meet a number of requirements before they can be considered in ASSLBs, including a wide electrochemical stability window, a high ionic conductivity and a negligible electronic conductivity [1]. For a long time, researchers have focused on achieving the highest ionic conductivity possible on these materials, comparable to the one of liquid electrolytes. The ionic conductivity in SEs has been successfully increased by the introduction of defects (doping) and Li_1.3Al_0.3Ti_1.7(PO₄)₃ and Li_1.5Al_0.5Ge_1.5(PO₄)₃ solid electrolytes are both excellent examples of such achievement. However, the formation of defects can also have a significant effect on the SEs electronic conductivity [2],[3],[4]. Increasing the electronic conductivity in solid electrolytes is detrimental to the ASSLBs safety and integrity. Therefore, it is essential to understand the defect chemistry in SEs. Due to their negligible concentration, characterizing point defects is hardly possible using standard characterization techniques, justifying the need for first-principles calculations. In this work, we have investigated the defect chemistry of most common solid electrolytes (Li_xM₂(PO₄)₃ (M = Zr, Ti, Ge, Al), Li₇La₃Zr₂O₁₂, LiLaTi₂O₆, Li₁₀Ge(PS₆)₂, Li₇P₃S₁₁, Li₃PS₄, Li₃PO₄ and LiPO₃). For each SE, we computed the formation energies for intrinsic defects and assessed the dopability limits as a function of the synthesis conditions. We found that the position of the Fermi level and dopability limits depend strongly on lithium and oxygen/sulfur chemical potentials but also on the nature of the solid electrolyte. We advocate that it is imperative to better regulate the synthesis conditions if we want to gain control over the formation of defects in solid electrolytes. The outcoming properties of these materials, such as the ionic and electronic conductivities, depend on it.

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