Ultrathin Mn Doped Ni‐MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor

Abstract In this study, we demonstrate that an Mn‐doped ultrathin Ni‐MOF nanosheet array on nickel foam (Mn0.1‐Ni‐MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn0.1‐Ni‐MOF/NF shows an areal capacity of 6.48 C cm−2 (specific capacity C: 1178 C g−1) at 2 mA cm−2 in 6.0 m KOH, outperforming most reported MOF‐based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn0.1‐Ni‐MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg−1 at 143.8 Wkg−1 power density with a capacitance retention of 83.6 % after 5000 cycles.