Hierarchical three-dimensional manganese doped cobalt phosphide nanowire decorated nanosheet cluster arrays for high-performance electrochemical pseudocapacitor electrodes.

Ternary metal phosphides with a self-assembled hierarchical nanostructure are promising electrode materials for energy storage and conversion, due to the unique architecture and synergistic effects in bimetallic nanostructures. In this communication, we demonstrate hierarchical Mn-doped cobalt phosphide nanowire decorated nanosheet cluster arrays with robust adhesion on Ni foam (Mn-CoP/NF) as a binder-free electrode for supercapacitors. Such a 3D electrode exhibits boosted areal specific capacitance over that for a single metal counterpart, with the accomplishment of 8.66 F cm-2 capacitance at 1 mA cm-2. Utilizing the Mn-CoP/NF electrode as an anode and an activated carbon (AC) electrode as a cathode, an asymmetric supercapacitor (ASC) of Mn-CoP//AC attains a high area capacitance of 2.05 F cm-2 at 5 mA cm-2 and a high capacitance retention of 88.9% after 4000 cycles. In addition, the assembled ASC shows superior electrochemical performances with a high energy density of 35.21 W h kg-1 at a power density of 193 W kg-1 and of 30.87 W h kg-1 even at 1939 W kg-1.