Effects of VIB group elements (Cr, Mo, W) on capacitance of nickel-cobalt hydroxide for supercapacitors

Abstract

Nickel‑cobalt hydroxide is a good candidate for a supercapacitor electrode; however, its poor cycle life and conductivity hinder the application. This work aims to improve electrochemical performance of nickel‑cobalt hydroxide by introducing VIB group elements (Cr, Mo, W). Our investigation focuses on the effects of VIB group elements (Cr, Mo, W) on capacitance of nickel‑cobalt hydroxide by controlling the content of each element. The optimized samples can deliver higher specific capacitance of 2350, 2670 and 1968 F g−1 for Cr-doped nickel‑cobalt hydroxide (NCC), Mo-doped nickel‑cobalt hydroxide (NCM) and W-doped nickel‑cobalt hydroxide (NCW), respectively, compared to pristine nickel‑cobalt hydroxides (NC,1676 F g−1). Moreover, the assemble NCM//YP50 device could achieve a maximum energy density of 47.64 Wh kg−1, higher than NC//YP50 (35.5 Wh kg−1), NCC//YP50 (43.3 Wh kg−1) and NCW//YP50 (41.24 Wh kg−1) devices, with excellent cycle life.