Fabrication of MnSe/SnSe@C heterostructures for high-performance Li/Na storage

Abstract

Tin-based selenides have been widely researched as electrode composites for lithium/sodium storage, ascribed to their relatively large theoretical specific capacity. However, the unsatisfactory electronic conductivity and the collapse of the structure associated with the large volume expansion lead to poor electrochemical performance and hinder their commercial application. Therefore, carbon-encapsulating MnSe/SnSe nanoboxes were designed and successfully prepared by an effortless wet-chemical method and selenization treatment for lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). The MnSe/SnSe@C–M (MSS) nanoboxes exhibited a reversible capacity of 965 mA h g⁻¹ after 240 cycles at 0.2 A g⁻¹ and superior cyclability of 557 mA h g⁻¹ after 900 cycles at 0.5 A g⁻¹ for LIBs. For NIBs, the MnSe/SnSe@C–M nanoboxes also displayed a high capacity of 500 mA h g⁻¹ after 78 cycles at 0.5 A g⁻¹ and good cyclability of 497.2 mA h g⁻¹ after 262 cycles at 2 A g⁻¹. The improved electrochemical performance could be associated with the following reasons: carbon layer can hinder volume change, avoid active material falling off from the copper foil, and further enhance the stability during cycling process. The existence of MnSe/SnSe heterostructures can efficaciously restrain the agglomeration of the element Sn⁰ and improve the reversibility of alloying reaction. The strong electronic coupling of Sn–C and Se–C chemical bonds between the carbon shell and SnSe promote fast electron/ion transport during the cycling process. Motivated by the excellent electrochemical properties of LIBs and NIBs, commercial LiFePO₄ (LFP)/Na₃V₂(PO₄)₃ (NVP) were paired with MnSe/SnSe@C–M to assemble and test its full-cell performance.