Abstract
• A large-scale synthetic route to obtain core-shell Fe 9 S 10 /Fe 3 O 4 @C heterostructures. • Fe 9 S 10 /Fe 3 O 4 @C can effectively trap LiPS and promote the conversion kinetics. • The Fe 9 S 10 /Fe 3 O 4 heterointerface offers a moderate chemical bonding with LiPS. • The cell with Fe 9 S 10 /Fe 3 O 4 @C interlayer exhibits enhanced rate and cycling capability. The shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish electrocatalysis of polysulfides conversion lead to severe capacity decay and poor rate capability, which is a determining factor for limiting the practical applications of lithium-sulfur (Li-S) batteries. To address such issues, a novel core-shell Fe 9 S 10 /Fe 3 O 4 @C architecture with well-defined heterointerfaces as a multifunctional polysulfides barrier for Li-S batteries is reported here. The spherical Fe 9 S 10 /Fe 3 O 4 @C heterostructure can be prepared by spray-drying technology on a large-scale and followed by a one-pot in-situ carbothermal reaction. With both physical entrapments by carbon shells and strong chemical interaction with Fe 9 S 10 /Fe 3 O 4 heterostructure cores, this constructed dense-packing architecture alleviates the shuttle effect. The mechanisms involved in the Fe 9 S 10 /Fe 3 O 4 @C trapping interlayer are confirmed by both experimental results and density functional theory (DFT) calculations. Moreover, due to its high conductivity and intrinsic catalytic activity, the Fe 9 S 10 /Fe 3 O 4 @C facilitates fast electron/ion transport and greatly improves the conversion of LiPSs. Benefit from the integrated trapping-catalyzing effect, the Li-S cell constructed with a Fe 9 S 10 /Fe 3 O 4 @C interlayer exhibits enhanced cycling stability (a low capacity fading rate of 0.08% per cycle for 500 cycles at 1 C) and outstanding rate performance (660 mAh g −1 at 5 C). Even under a high areal sulfur loading of 3 mg cm −2 , the high discharge capacity and capacity retention ratio can also be obtained. This work offers an insight into the construction of multi-functional heterostructures for high-performance Li-S batteries.
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