RESUMO
Lithium sulfur batteries (LSBs) have been considered as one of the most promising options for next generation high-performance batteries. However, the heavy shuttle effect and inferior redox conversion during the charge/discharge processes of the batteries have greatly hindered their further applications. In this study, to address these disadvantages of LSBs, Fe/Fe3C/FeN0.0324 heterostructured nanocubes were designed and prepared through high temperature carbonization process using Prussian blue precursor. Then the Fe/Fe3C/FeN0.0324 nanocubes were used to modify the commercial polypropylene (PP) separator, which can greatly catalyze the redox transformation of polysulfides and provide sufficient active sites for chemisorption. As result, the modified separator endowed LSBs with excellent rate capacity and cycle stability, delivering a high-capacity of 1025 mAh/g at 0.5 C with nearly 100% coulombic efficiency. It also displayed a superb cycling performance with a per-cycle capacity attenuation rate of 0.09% after 300 cycles. When the current density increased to 1 C with the S loading of 1.73 mg cm-2, Fe/Fe3C/FeN0.0324-PP separator presented a satisfactory capacity decay rate of 0.05% per cycle after 1000 cycles. Besides, it also presented outstanding electrochemical performance even at high sulfur loading of 4.5 mg cm-2. This work has provided a new avenue for the design of nanomaterials with synergistic effect of catalytic conversion and chemisorption of polysulfides for the promotion of high-performance Li-S batteries.
RESUMO
Lithium-sulfur batteries (LSBs) have aroused great research interest due to their high theoretical capacity and high energy density. To further develop lithium-sulfur batteries, it has become more and more important to put more efforts in promoting the adsorption and rapid catalytic conversion of lithium polysulfides (LiPSs). Herein, Ni/Co bimetallic phosphides were encapsulated into nitrogen-doped dual carbon conductive network (NiCoP@NC) by annealing and phosphorizing Ni-ZIF-67 precursor at high temperature. Due to their numerous co-adsorption/catalytic sites and high conductivity of carbon skeleton, the encapsulated Ni/Co phosphides particles could significantly enhance the anchoring and catalytic conversion of LiPSs and provide ultrafast channels for Li+ transport. When used as a modified separator for LSBs, the cells displayed superior performance with an initial capacity of 1083.4 m Ah g-1 at 0.5 C and outstanding cycle stability with a capacity decay rate of only 0.09% per cycle for 300 cycles. Besides, even at high sulfur loading (3.2 mg cm-2), they still present satisfactory performance. Therefore, this study presents a novel strategy on how to use MOF derived bimetallic phosphides with chemical adsorption and catalytic conversion of polysulfides for high-power advanced lithium-sulfur batteries.