Ternary sulfur/polyacrylonitrile/Mg0.6Ni0.4O composite cathodes for high performance lithium/sulfur batteries

Abstract

Nanostructured magnesium nickel oxide (Mg0.6Ni0.4O) 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/Mg0.6Ni0.4O (S/PAN/Mg0.6Ni0.4O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg0.6Ni0.4O, 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 Mg0.6Ni0.4O, 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/Mg0.6Ni0.4O 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.