Figure 4. SEM and TEM images of NiFe 2 O 4 as host materials sulfur cathodes. a) NiFe 2 O 4 -CNTs hybrid. Reproduced with permission. [49] Copyright 2018, Elsevier. b) Fine S nanoparticles coating CNT/NiFe 2 O 4 .Reproduced with permission. [50] Copyright 2015, American Chemical Society. c) NiFe 2 O 4 hollow spheres. Reproduced with permission. [51] Copyright 2019, American Chemical Society. d) NiFe 2 O 4 nanofibers. Reproduced with permission. [52] Copyright 2018, Springer Nature.

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Lithium−sulfur batteries with high theoretical energy density have emerged as one of the most promising next-generation rechargeable batteries, while their discharge capacity and cycle stability are challenges mainly due to the shuttle effect of polysulfide intermediates. Employing an effective catalyst for the conversion of polysulfides in cathode reactions can promote the reaction kinetics to restrain the shuttle of polysulfides. Here, for the first time, La 2 MoO 6 (LMO) as a catalyst is introduced into sulfur cathodes. To investigate the effect of La 2 MoO 6 , we prepare two different structures of La 2 MoO 6 /carbon nanofiber composites. One is carbon nanofibersupported crystalline La 2 MoO 6 nanoparticles (LMO@CNFs) and the other is amorphous La 2 MoO 6 nanoparticles embedded in carbon nanofibers (LMO-in-CNFs). For sulfur electrodes with ∼73 wt % sulfur loading, LMO@CNFs/S and LMO-in-CNFs/S deliver initial gravimetric capacities of 1493.4 and 1246.7 mA h g −1 , respectively, at a 0.1C rate, obviously higher than that of the control sample CNFs/S. Moreover, LMO@CNFs/S shows much better rate performance than LMO-in-CNFs/S, indicating strongly that La 2 MoO 6 is a highly effective catalyst to promote kinetic conversion of polysulfides.

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