Facile Electrodeposition of Mn-CoP Nanosheets on Ni Foam as High-Rate and Ultrastable Electrodes for Supercapacitors

As the combined merits of structures and compositions could have a great impact on electrodes, we synthesized manganese-doped cobalt phosphide nanosheets on Ni foam (Mn-CoP/NF) via a facile electrodeposition method. The synergistic effect between Mn and Co ions provides mixed valence states and adjusts the bandgap for accelerating the high redox reaction kinetics and improving the electron mobility and electrical conductivity. Meanwhile, the nanosheet structure provides rich electroactive sites and excellent structural stability for facilitating the electron transfer and resisting structural damage. As expected, the obtained Mn-CoP/NF electrode acquired a superior specific capacity (456 C g–1 at 0.5 A g–1), an excellent rate performance (77.4% capacity retention at 10 A g–1), and an excellent cyclability (89.0% capacity retention after 20,000 cycles). The Mn-CoP/NF//AC asymmetric supercapacitor (ASC) delivers a high energy density (14.82 W h kg–1 at 312 W kg–1) and long-term durability (87.7% capacity retention after 20,000 cycles). Moreover, two ASC devices can be used to light an LED for 6 min, demonstrating ASC’s promising practical applications.