Ternary sulfur/polyacrylonitrile/Mg_0.6Ni_0.4O composite cathodes for high performance lithium/sulfur batteries

Nanostructured magnesium nickel oxide (Mg_0.6Ni_0.4O) was synthesized by a self-propagating high temperature synthesis method followed by heat treatment. The particles of the resulting oxide were used as additives to prepare the sulfur/polyacrylonitrile/Mg_0.6Ni_0.4O (S/PAN/Mg_0.6Ni_0.4O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg_0.6Ni_0.4O, from smooth bulky particles of S/PAN to rough nanostructured agglomerates with two times the increase in the specific surface area, favouring the reactivity of the composite, and a homogeneous component distribution. Cyclic voltammetry, discharge-charge tests and ac impedance spectroscopy have shown improved conductivity and electrochemical properties of the composite by the addition of Mg _0.6Ni_0.4O, leading to high sulfur utilization and interfacial stabilization in a Li/S cell upon discharge-charge cycling. The cell demonstrated enhanced reversibility, resulting in a discharge capacity of about 1223 mA h g^-1 at the second cycle and retained about 100% of this value over 100 cycles. Furthermore, the S/PAN/Mg_0.6Ni_0.4O composite cathode exhibited a good rate capability with discharge capacities of 887, 710 and 445 mA h g^-1 at 0.5, 0.7 and 1 C, respectively.