Three-Dimensional (3D) Ordered Macroporous Bimetallic (Mn,Fe) Selenide/Carbon Composite with Heterojunction Interface for High-Performance Sodium Ion Batteries

Transition-metal selenides have captured significantresearch attentionas anode materials for sodium ion batteries (SIBs) due to their hightheoretical specific capacities and excellent electronic conductivity.However, volumetric expansion and inferior cycle life still hindertheir practical application. Herein, a three-dimensional (3D) orderedmacroporous bimetallic (Mn,Fe) selenide modified by a carbon layer(denoted as 3DOM-MnFeSe x @C) compositecontaining a heterojunction interface is fabricated through selenizinga 3D ordered macroporous Mn-based Prussian Blue analogue single crystal.The 3DOM-MnFeSe x @C exhibits hierarchicallyporous architecture with enhanced mass-transfer efficiency; MnSe andFeSe(2) particles are encapsulated into macroporous carbonframework, which can significantly promote the electronic conductivityand maintain the structural integrity. The density functional theorycalculation indicates that the heterojunction interface between MnSeand FeSe2 has been successfully engineered so that Na+ can be readily adsorbed and rapidly converted, thus promotingthe reaction kinetics and extending the cyclic life. As expected,the 3DOM-MnFeSe x @C composite deliversexcellent rate performance (277.6 mA h g(-1) at 10A g(-1)), and prolonged cycling life (191.6 mA h g(-1) even after 1000 cycles at 2 A g(-1)) as a sodium storage anode. The sodium storage mechanism of thecomposite was further investigated by in situ X-ray diffraction andex situ high-resolution transmission electron microscopy characterizationtechniques.

Automated summary

A three-dimensional ordered macroporous bimetallic (Mn, Fe) selenide modified by a carbon layer (3DOM-MnFeSex@C) composite with a heterojunction interface was fabricated through selenizing a 3D ordered macroporous Mn-based Prussian Blue analogue single crystal. The 3DOM-MnFeSex@C exhibited hierarchically porous architecture with enhanced mass-transfer efficiency and superior electronic conductivity, leading to excellent rate performance and extended cycling life as a sodium storage anode for sodium ion batteries.