Buffer layer enhanced stability of sodium-ion storage

Se-Se buffer layers are introduced into tin sequences as SnSe2 single crystal to enhance the cycling stability for long-term sodium-ion storage by blazing a trail of self-defence strategy to structural pulverization especially at high current density. Specifically, under half-cell test, the SnSe2 electrodes could yield a high discharge capacity of 345 mAh g(-1) after 300 cycles at 1 A g(-1) and a high discharge capacity of 300 mAh g(-1) after 2100 cycles at 5 A g(-1) with stable coulombic efficiency and no capacity fading. Even with the ultrafast sodium-ion storage at 10 A g(-1), the cycling stability still makes a positive response and a high discharge capacity of 221 mAh g(-1) is demonstrated after 2700 cycles without capacity fading. The full-cell test for the SnSe2 electrodes also demonstrates the superior cycling stability. The flexible and tough Se Se buffer layers are favourable to accommodate the sodium-ion intercalation process, and the autogenous Na2Se layers could confine the structural pulverization of further sodiated tin sequences by the slip along the Na2Se Na5Sn interfaces. (C) 2017 Elsevier B.V. All rights reserved.