Constructing hierarchical MoS/WS heterostructures in dual carbon layer for enhanced sodium ions batteries performance.

The escalating global demand for clean energy has spurred substantial interest in sodium-ion batteries (SIBs) as a promising solution for large-scale energy storage systems. However, the insufficient reaction kinetics and considerable volume changes inherent to anode materials present significant hurdles to enhancing the electrochemical performance of SIBs. In this study, hierarchical MoS/WS heterostructures were constructed into dual carbon layers (HC@MoS/WS@NC) and assessed their suitability as anodes for SIBs. The internal hard carbon core (HC) and outer nitrogen-doped carbon shell (NC) effectively anchor MoS/WS, thereby significantly improving its structural stability. Moreover, the conductive carbon components expedite electron transport during charge-discharge processes. Critically, the intelligently engineered interface between MoS and WS modulates the interfacial energy barrier and electric field distribution, promoting faster ion transport rates. Capitalizing on these advantageous features, the HC@MoS/WS@NC nanocomposite exhibits outstanding electrochemical performance when utilized as an anode in SIBs. Specifically, it delivers a high capacity of 415 mAh/g at a current density of 0.2 A/g after 100 cycles. At a larger current density of 2 A/g, it maintains a commendable capacity of 333 mAh/g even after 1000 cycles. Additionally, when integrated into a full battery configuration with a NaV(PO) cathode, the NaV(PO)//HC@MoS/WS@NC full cell delivers a high capacity of 120 mAh/g after 300 cycles at 1 A/g. This work emphasizes the substantial improvement in battery performance that can be attained through the implementation of dual carbon confinement, offering a constructive approach to guide the design and development of next-generation anode materials for SIBs.