Ni 6 Se 5 , an unexplored transition metal chalcogenide of formula M (n+1) X n (2≤n≤8), for high-performance hybrid supercapacitor and Li-ion battery application.

This work reports an in-situ, one-step hydrothermal preparation procedure of a binder-free electrode growth of Ni 6 Se 5 on nickel foam (Ni 6 Se 5 /NF) with a rod-like structure. Ni 6 Se 5 is an enveloped transition metal chalcogenides of formula M (n+1) X n (where 2≤n≤8, M is a transition metal and X is chalcogen) of the nickel selenide family. The Ni 6 Se 5 /NF electrode described here demonstrates an exceptional lifetime of 81% capacitance retention over 20000 cycles and a high specific capacitance of 473.5 Fg -1 at a current density of 4 Ag -1 . The Ni 6 Se 5 /NF/activated carbon asymmetric supercapacitor exhibits a remarkable 97.3 Whkg -1 energy density and a 2325 Wkg -1 power density. Ni 6 Se 5 served as an active electrode material in supercapacitor applications and offered exceptional power density and long cycle life. Ni 6 Se 5 /NF, used as an anode for Li-ion batteries (LIB), has a lithium storage capacity of 939.7 mAhg -1 at 100 mAg -1 current density. Ni 6 Se 5 active electrode material's excellent energy storage capability, which was previously unreported, is particularly beneficial for electrochemical energy storage device applications.