A new potassium dual-ion hybrid supercapacitor based on battery-type Ni(OH) nanotube arrays and pseudocapacitor-type VO-anchored carbon nanotubes electrodes.

Hybrid supercapacitors (HSCs) with the characteristics of high energy density, long cycle life and without altering their power density need to be developed urgently. Herein, a novel dual-ion hybrid supercapacitors (DHSCs) with Ni(OH) nanotube arrays (NTAs) as positive electrode and VO directly grown on freestanding carbon nanotubes (CNTs) as negative electrode is assembled. In charging mechanism of DHSCs, K are inserted into the VO negative while OH react with Ni(OH) positive; during discharge, the K and OH are released from VO negative and Ni(OH) positive, respectively, and return back to the electrolyte, which is quite different from traditional metal ion or alkaline supercapacitors. Because of the merits combining dual-ion mechanism and HSCs, the DHSC displays excellent capacity retention of ∼ 81.4% after 10,000 cycles, high energy density of ∼ 25.4 μWh cm and high power density of ∼ 4.66 mW cm, indicating the potential applications in the further on flexible wearable electronics.