TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compositions: Metal fluoride is represented by formula MFx (I). Positive electrode material contains 0.5-5 mass% metal fluoride. Water-soluble metal salt is hydrate of lithium nitrate, lithium sulfate, lithium carbonate, lithium acetate, beryllium nitrate, beryllium sulfate, beryllium carbonate, beryllium acetate, sodium nitrate, sodium sulfate, sodium carbonate, sodium acetate, magnesium nitrate, magnesium sulfate, magnesium carbonate, magnesium acetate, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum acetate, potassium nitrate, potassium sulfate, potassium carbonate, potassium acetate, calcium nitrate, calcium sulfate, calcium carbonate, calcium acetate, scandium nitrate, scandium sulfate, scandium carbonate, scandium acetate, titanium nitrate, titanium sulfate, titanium carbonate, titanium acetate, vanadium nitrate, vanadium sulfate, vanadium carbonate, vanadium acetate, chromium nitrate, chromium sulfate, chromium carbonate, chromium acetate, manganese nitrate, manganese sulfate, manganese carbonate, manganese acetate, iron nitrate, iron sulfate, iron carbonate, iron acetate, cobalt nitrate, cobalt sulfate, cobalt carbonate, cobaltous acetate, nickel nitrate, nickel sulfate, nickel carbonate, nickel acetate, copper nitrate, copper sulfate, copper carbonate, copper acetate, zinc nitrate, zinc sulfate, zinc carbonate, zinc acetate, gallium nitrate, gallium sulfate, gallium carbonate, gallium acetate, rubidium nitrate, rubidium sulfate, rubidium carbonate, rubidium acetate, strontium nitrate, strontium sulfate, strontium carbonate, strontium acetate, yttrium nitrate, yttrium sulfate, yttrium carbonate, yttrium acetate, zirconium nitrate, zirconium sulfate, zirconium carbonate, or zirconium acetate. Water-soluble metal salt is aluminum nitrate nonahydrate, aluminum sulfate 18 hydrate, or gallium nitrate hydrate. Fluoride is ammonium fluoride, tetrabutylammonium fluoride hydrate, tetrabutylammonium fluoride trihydrate, or tetramethylammonium fluoride tetrahydrate. Gas is nitrogen or argon gas.M=Li, Be, Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, or Zr; andx=valence of M. Preferred Definitions:    x=3.