NOVELTY - The solid-state ion conductor comprises lithium (Li), phosphorus (P), sulfur, and a trivalent or tetravalent metal element including scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rare earth element, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, zinc, cadmium, and mercury. The ion conductor further comprises a cation and an anion.    USE - The solid-state lithium ion conductor is useful in an electrochemical device (claimed) such as a lithium ion secondary battery, a primary battery, an electrochemical capacitor, a fuel cell and a gas sensor that is useful in mobile devices, electric vehicles and home-use or industrial-use storage batteries and as a power source for a mobile electronic appliance.    ADVANTAGE - The solid-state lithium ion conductor has high ion conductivity and less electron conductivity, and reduces electrolyte decomposition in the battery thus enhancing capacity and performance of the battery and preventing leakage of liquid.    DETAILED DESCRIPTION - The solid-state ion conductor comprises lithium (Li), phosphorus (P), and sulfur, and a trivalent or tetravalent metal element including scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rare earth element, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, zinc, cadmium, and mercury. The ion conductor further comprises a cation, an anion, and a mixture of an amorphous material free of a crystalline phase and a crystalline material having a crystalline phase. The metal element is present in an amount of 0.55-4.31 mole%. A molar ratio of Li to P is 2.1-4.6.    DESCRIPTION OF DRAWING(S) - The figure shows a transmission electron microscopic image of a solid-state lithium ion conductor.