LAGP belongs to phosphate-based solid electrolytes and, in spite of showing a moderate ionic conductivity compared to other families of solid ionic conductors, it possesses some intrinsic advantages with respect to sulfides and oxides:
* Extremely high chemical stability in humid air; 
* Wide electrochemical stability window;
* Low to negligible electronic conductivity.
One of the main advantages of LAGP is its chemical stability in the presence of oxygen, water vapour, and carbon dioxide, which simplifies the manufacture process preventing the use of a glovebox or protected environments. Unlike sulfide-based solid electrolytes, which react with water releasing poisonous gaseous hydrogen sulfide, and garnet-type lithium lanthanum zirconium oxide (LLZO), which react with water and CO to form passivating layers of LiOH and LiCO, LAGP is practically inert in humid air.
Another important advantage of LAGP is its wide electrochemical stability window, up to 6 V, which allows the use of such electrolyte in contact with high-voltage cathodes, thus enabling high energy densities. However, the stability at very low voltages and against lithium metal is controversial: even if LAGP is more stable than LATP because of the absence of titanium, some literature works report on the reduction of Ge by lithium as well, with formation of Ge and metallic germanium at the electrode-electrolyte interface and dramatic increase of interfacial resistance.
The possible decomposition mechanism of LAGP in contact with metallic lithium is reported in the equation below: