Interface ion-exchange strategy of MXene@FeInS hetero-structure for super sodium ion half/full batteries.

Herein, a well-designed hierarchical architecture of bimetallic transition sulfide FeInS nanoparticles anchoring on the TiC MXene flakes has been prepared by cation exchange and subsequent high-temperature sulfidation processes. The introduction of MXene substrate with excellent conductivity not only accelerates the migration rate of Na to achieve fast reaction dynamics but provides abundant deposition sites for the FeInS nanoparticles. In addition, this hierarchical structure of MXene@FeInS can effectively restrain the accumulation of MXene to guarantee the maximized exposure of redox active sites into the electrolyte, and simultaneously relieve the volume expansion in the repeated discharging/charging processes. The MXene@FeInS displays outstanding rate capability (448.2 mAh g at 5 A g) and stable long cycling performance (428.1 mAh g at 2 A g after 200 cycles). Moreover, the Na-InS phase detected by ex-situ XRD and XPS characterization may be regarded as a "buffer" to maintain the stability of the Fe-based components and enhance the reversibility of the electrochemical reaction. This work confirms the practicability of constructing the hierarchical structure bimetallic sulfides with the promising electrochemical performance.