Effects of nanosized adsorbing material on electrochemical properties of sulfur cathodes for Li/S secondary batteries

In order to prevent polysulfide dissolution into liquid electrolytes and to promote the Li/S redox reaction (16Li + S₈ ↔ Li₂Sn ↔ Li₂S), nanosized Mg_0.6Ni_0.4O, which has the catalytic effect of chemical bond dissociating and is expected to have an adsorbing effect due to the effect of retaining liquid electrolyte of MgO in a Li/iron sulfide secondary battery, was prepared by the sol-gel method as an electrochemically inactive additive for an elemental sulfur cathode for Li/S rechargeable batteries. The Li/S battery using an elemental sulfur cathode with a nanosized Mg_0.6Ni_0.4O added showed the improvement of not only the discharge capacity but also cycle durability (maximum discharge capacity: 1185 mAh/g sulfur, C₅₀/C₁ = 85%). The rate capability of the sulfur cathode was also increased with the addition of the nanosized Mg_0.6Ni_0.4O. From the results, it is confirmed that the nanosized Mg_0.6Ni_0.4O had the polysulfide adsorbing effect and the catalytic effect of promoting Li/S redox reaction. Furthermore, it is found that the nanosized Mg_0.6Ni_0.4O also increased the porosity of the sulfur cathode.