Core-shell Structral Materials Decarated With Transition Matal Nitrides/sulfides For Lithium-sulfur Battery

Lithium-sulfur batteries are expected to be the next generation batteries due to its high capacity and low cost.However,the practical application of lithium-sulfur battery is restricted by shuttle effect of lithium polysulfides(LPSs)intermediates,poor conductivity of sulfur and large volume change during cycling.In this study,hollow carbon sphere decarated with vanadium nitride is synthesized and investigated as the cathode of lithium-sulfur battery.The core-shell structural material provides large inner space for high sulfur content.Vanadium nitride can anchor soluble LPSs because of their strong chemical affinity with LPSs,moreover,the high conductivity of vanadium nitride contributes to lower polarization and faster redox reaction kinetics.Benefit from this unique structure,VN-H-C cathodes filled with 74%sulfur have an initial capacity of 782mAh/g at a current density of 1C and a capacity retention of 445mAh/g after 300 charge/discharge cycle.When the sulfur content is reduced to 62%,the initial capacity is 883 mAh/g at a current density of 1C,and after 300 charge/discharge cycle,there is still a capacity retention of 534 mAh/g.It opens a feasible method to design high-performance cathodes for Lithium-sulfur batteries.Secondly,the(FeNi)S2 was also synthesized and investigated as the cathode of lithium-sulfur battery.The experimental results show that(FeNi)S2 has good initial discharge capacity and capacity retention.Finally,in order to find a low-cost synthetic method of transition metal sulfides,the FeS2 was obtained by the reaction between sulfur and ferric nitrate in formamide solvent,thereby we have explored a cheap,low-toxic,convenient new method for synthesizing transition metal sulfides for lithium-sulfur battery.The new method is beneficial to the commercial application of the lithium sulfur battery.