Electrochemical-induced surface reconstruction to NiFe-LDHs-based heterostructure as novel positive electrode for supercapacitors with enhanced performance in neutral electrolyte

Layered double hydroxides (LDHs) are promising battery-type electrode materials for hybrid supercapacitors. However, their poor capacity in neutral electrolyte is the primary limitation for the practical application. Herein, we fabricated a kind of novel NiFe-LDHs-based heterostructure as high-performance electrode materials in neutral electrolyte via a high-voltage electrochemical cycling activation (ECA) strategy. During the high-voltage ECA process, NiFe-LDHs surface was in-situ reconstructed into low-crystalline NiOOH phase, and finally evolved to the unique NiFe-LDHs/NiOOH heterostructures. This surface reconstruction process can generate abundant heterogeneous interface so as to increase the active sites for the reversible adsorption and intercalation of cationic ions, accounting for the significantly improved electrochemical performance in neutral electrolyte. When used as the battery-type electrode material in neutral electrolyte (2 M LiNO3 solution), the obtained ECA (1.2 V-50) electrode exhibits an excellent specific capacity (107 mAh g−1 at a current density of 1 A g−1), which is increased by 50 times compared to the Initial-NiFe-LDHs (2.1 mAh g−1 at a current density of 1 A g−1). By coupling with a MoS2/rGO electrode, the assembled ECA (1.2 V-50)//MoS2/rGO hybrid supercapacitor device depicts a high energy density of 48.1 Wh kg−1 at a power density of 432.9 W kg−1 in neutral electrolyte, which is superior to most of the reported hybrid supercapacitors.