Achieving ultrastable cyclability and pseudocapacitive sodium storage in SnSe quantum-dots sheathed in nitrogen doped carbon nanofibers

Abstract

Engineering suitable tin selenide (SnSe) anode for sodium ion batteries (SIBs) with both excellent cycling durability and remarkable rate capability has received enormous attention. The effective regulation of morphology and size has been shown to promote electrochemical performance. The irregular shape and micron size of obtained SnSe by conventional construction methods (high energy ball milling) is detrimental to the anode performance. Herein, SnSe quantum-dots (E-SnSe) and SnSe nanoparticles (B-SnSe) are synthesized by means of a feasible electrospinning technique together with subsequent high-temperature selenylation and high energy ball milling, respectively, and both are examined as anode materials for SIBs. As compared to B-SnSe electrode, the E-SnSe electrode delivers a larger discharge capacity of 268 mAh g−1 after 750 cycles at 2 A g−1 and more remarkable cycling durability over 1500 cycles even at much higher rate of 5 A g−1, which is the best cycling stability reported so far for SnSe-based anodes. The significantly enhanced performance is attributed to unique three-dimensional (3D) conductive carbon network structure of E-SnSe, which could boost rapid electron/sodium ion transport with the remarkable contribution of pseudocapacitance and dramatically improve the structure evolution of SnSe resulted from the conversion and alloying process. Furthermore, the assembled Na3V2(PO4)3@C//E-SnSe full cell shows an output voltage of above 2.0 V, ultralong cycle life of 1500 cycles with a high reversible discharge capacity of about 100 mAh g−1 at 1 A g−1 and superior rate capability with 86.4% capacity retention after 35 cycles, showing the potential application prospects in a large scale energy storage field.