Designing a Charge-Redistributed Heterostructure as Secondary Battery Anode Displaying High Capacity and Good Temperature Tolerance

Heterostructured materials have been considered promising as sodium-ion (Na-ion) battery anode materials due to adjustable electronic and ionic transport properties, while designing ideal heterostructure systems between single- and binary-metal sulfides has not been established yet. Herein, we present a charge-redistributed heterostructure composed of single- and binary-metal sulfides (CuS/CuFeS₂), which exhibits ultrahigh performance as a Na-ion battery anode material. The as-formed heterojunction is beneficial for accelerating the kinetics of electrochemical reactions based on charge redistribution, which has been demonstrated by density functional theory calculations. In situ Raman spectra and in situ X-ray diffraction spectra demonstrate excellent reversibility during the charge and discharge. When cycling at 1.0 A g^-1, the CuS/CuFeS₂ anode exhibits a high capacity of 520 mAh g^-1 and a Coulombic efficiency of 99.9% after cycling 1000 times. After 3600 cycles at 5 A g^-1, the capacity remains at 403 mAh g^-1. It also displays stable capacities under -10 and 50 °C. The full cell pairing with a Na₃V₂(PO₄)₃ cathode exhibits a good capacity of 445 mAh g^-1. This study provides a simple and general approach to achieve high-performance heterostructures, which could find a broad set of applications for other heterostructured systems and their batteries.