Formation of fringed carnation-like cobalt manganese fluoride hydroxide assisted by ammonium fluoride for supercapacitor applications

Abstract

The binary transition metal oxides or hydroxides have received significant attention as potential materials in supercapacitor applications owing to their unique characteristics. In this study, a binary cobalt-manganese fluoride hydroxide-CoMn(OH)F is assembled successfully through the crucial assistance of an ammonium fluoride agent in an alkali source of hexamethylenetetramine (HMTA). At a rational design, the CoMn(OH)F with fringed carnation-like morphology obtains a specific capacitance of 541 F g −1 (at a current density of 1 A g −1 ) in a three-electrode system and cycling stability of 84% after 15,000 cycles. Furthermore, an asymmetric device CoMn(OH)F//activated carbon in a two-electrode system not only exhibits a remarkable specific capacitance of 135 F g −1 (at 0.4 A g −1 ), a high energy density of 39 Wh kg −1 , and a power density of 3.65 kW kg −1 but also maintains 91% of the initial capacitance after 10,000 cycling tests. These electrochemical performances demonstrate the considerable potential of the fluoride hydroxide CoMn(OH)F for supercapacitor applications. • CoMn(OH)F was formed via the key role of NH 4 F and the optimal precursor ratio. • CoMn(OH)F had a fringed carnation-like morphology. • Sample obtained synergistic effects of diffusion and capacitive-controlled process. • CoMn(OH)F//AC exhibited energy density 39 Wh kg −1 and power density 3.65 kW kg −1 .