Disclosing synergistically kinetic regulation mechanism of WS2/MoS2/C microspheres to achieve high-efficiency sodium ion storage

Transition metal dichalcogenides (TMDs) are considered as potentially the most promising anodes for sodium-ion batteries, but still suffers from multistep electrochemical processes, resulting in sluggish Na + migration and poor Na + storage capacity in bulk materials. In this work, two kinds of TMDs (WS 2 and MoS 2 ) with similar energy band structures are rationally designed by atomic-scale regulated growth to synthesize porous WS 2 /MoS 2 /Carbon microspheres to disclose their internal kinetics regulation mechanism. It shows that due to the introduction of abundant unsaturated sulfur sites by WS 2 and MoS 2 lattice mismatches, which enhances charge accumulation and serves as active sites to increase the Na + pseudocapacitive storage. Furthermore, a built-in electric field between WS 2 and MoS 2 is formed by the rich heterojunction interfaces, promoting the kinetics of electrochemical transformations of two metallic elements in both WS 2 and MoS 2 . Therefore, the optimized WS 2 /MoS 2 /Carbon provides a discharge specific capacity of 499 mAh g −1 after 500 cycles at 1 A g −1 with a high capacity retention rate of 97.5 %, as well as specific capacity of 435 mAh g −1 after 100 cycles at 0.5 A g −1 with a capacity retention rate of 91 % for WS 2 /MoS 2 /Carbon || Na 3 V 2 (PO 4 ) 3 full cell, which demonstrates satisfactory capacity and outstanding cycling stability.