Spinel-type bimetal sulfides derived from Prussian blue analogues as efficient polysulfides mediators for lithium−sulfur batteries

In this work, spinel-type hollow NiCo2S4 nanocubes are synthesized through a facile route Prussian blue analogue derived as the sulfur host to improve the electrochemical performance of Li-S battery. The synthetic route is shown in the figure above. Besides the high conductivity and catalytic performance of the bimetal sulfide, the NiCo2S4 nanocubes have more specific surface area to react and have more volume to prevent volume expansion. [Display omitted] More and more attentions have been attracted by lithium-sulfur batteries (Li-S), owing to the high energy density for the increasingly advanced energy storage system. While the poor cycling stability, due to the inherent polysulfide shuttle, seriously hampered their practical application. Recently, some polar hosts, like single metal oxides and sulfides, have been employed as hosts to interact with polysulfide intermediates. However, due to the inherent poor electrical conductivity of these polar hosts, a relatively low specific capacity is obtained. Herein, a spinel-type bimetal sulfide NiCo2S4 through a Prussian blue analogue derived methodology is reported as the novel host of polysulfide, which enables high-performance sulfur cathode with high Coulombic efficiency and low capacity decay. Notably, the Li-S battery with NiCo2S4-S composites cathode still maintains a capacity of 667 mAh/g at 0.5 C after 300 cycles, and 399 mAh/g at 1 C after 300 cycles. Even after 300 cycles at the current density of 0.5 C, the capacity decays by 0.138% per cycle at high sulfur loading about 3 mg/cm2. And the capacity decays by 0.026% per cycle after 1000 cycles, when the rate is 1 C. More importantly, the cathode of NiCo2S4-S composite shows the outstanding discharge capacity, owing to its good conduction, high catalytic ability and the strong confinement of polysulfides.