A method for fabricating intercalated lithium batteries in open air deposits a thin dense layer of amorphous solid-state lithium boride electrolyte directly onto a negative electrode via flame spray pyrolysis. In one embodiment, the negative electrode is attached to a prefabricated positive electrode via hot pressing (embossing), thus forming an intercalated lithium battery. The method significantly improves upon current methods of fabricating thin film solid state batteries by permitting fabrication without the aid of a controlled environment, thereby allowing for significantly cheaper fabrication than prior batch methods.