The paper presents the results of the studies of thermal properties of nanocrystalline superionic NaxCu1.75S (x=0.1, 0.15, 0.2, 25) compositions, and preliminary results of Na0.1Cu1.75S using as energy stored cathode material in Na-ion half-cell with NaPF 6 electrolyte and Na anode. The compositions contain a few copper sulfide phases: monoclinic chalcocite Cu2S , orthorhombic ...