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

In this study, we demonstrate that an Mn‐doped ultrathin Ni‐MOF nanosheet array on nickel foam (Mn 0.1 ‐Ni‐MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn 0.1 ‐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 Mn 0.1 ‐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.