Sulfuration of NiV-layered double hydroxide towards novel supercapacitor electrode with enhanced performance

NiV-LDH as a novel electrode material has rarely been investigated in the energy storage field. Herein, novel ultrathin NiV-LDH was designed and synthesized, which displays high specific capacitance but poor stability. To further improve the stability, NiV-LDH was transformed to the sulfide named NiV-S through an ion exchange reaction (S2− replaces OH−). The obtained NiV-S maintains the ultrathin (5 nm in thickness) and porous structure, and displays higher specific capacitance (2270.4 F g−1 at 2 A g−1), compared to NiV-LDH (1502 F g−1 at 2 A g−1). What is more improtant is that the cycling stability of NiV-S is much higher than NiV-LDH, (91.9% retention after 10,000 cycles for NiV-S vs only 63% retention after 5000 cycles for NiV-LDH). The asymmetric supercapacitor assembled using ultrathin porous NiV-S as the positive electrode and activated carbon (AC) as the negative electrode was found to deliver a maximum energy density of 51 W h kg−1 at a power density of 1600 W kg−1 and 12 kW kg−1 at 23.7 W h kg−1. In addition, 98.5% of the initial capacitance retains after 10,000 continuous cycling.