SOLID ELECTROLYTE AND ALL-SOLID CELL CONTAINING SAME

The present invention relates to a solid electrolyte including Li, O, P and a transition metal element. In the solid electrolyte, because the transition metal element T is reduced prior to phosphorus atoms, it is possible to prevent the valence of phosphorus atoms from decreasing. Thereby, the decomposition of the solid electrolyte resulting from the decrease of valence of phosphorus atoms is prevented, and therefore high ion conductivity is retained even in a wet atmosphere.