In an aspect, a solid-state Li-ion battery (SSLB) cell, may comprise an anode electrode comprising an anode electrode surface and an anode active material, a cathode electrode comprising a cathode electrode surface and an cathode active material, and an inorganic, melt-infiltrated, solid state electrolyte (SSE) ionically coupling the anode electrode and the cathode electrode, wherein at least a portion of at least one of the electrode surfaces comprises an interphase layer separating the respective electrode active material from direct contact with the SSE, and wherein the interphase layer comprises two or more metals from the list of: Zr, Al, K, Cs, Fr, Be, Mg, Ca, Sr, Ba, Sc, Y, La or non-La lanthanoids, Ta, Zr, Hf, and Nb.