A solid ionically conductive composition (e.g., nanoparticles of less than 1 micron or a continuous film) comprising at least one element selected from alkali metal, alkaline earth metal, aluminum, zinc, copper, and silver in combination with at least two elements selected from oxygen, sulfur, silicon, phosphorus, nitrogen, boron, gallium, indium, tin, germanium, arsenic, antimony, bismuth, transition metals, and lanthanides. Also described is a battery comprising an anode, a cathode, and a solid electrolyte (corresponding to the above ionically conductive composition) in contact with or as part of the anode and/or cathode. Further described is a thermal (e.g., plasma-based) method of producing the ionically conductive composition. Further described is a method for using an additive manufacturing (AM) process to produce an object constructed of the ionically conductive composition by use of particles of the ionically conductive composition as a feed material in the AM process.