Ultrathin Ni-MOF nanosheet arrays grown on polyaniline decorated Ni foam as an advanced electrode for asymmetric supercapacitors with high energy density

Abstract

Metal–organic frameworks (MOFs) have emerged as promising electrode materials for supercapacitors (SCs), due to their diverse functionalities and high porosity. However, the applications of MOFs in practical SC devices are restricted by their intrinsic low conductivity and poor stability. Herein, a thin layer of conductive polyaniline (PANI) was decorated on Ni foam (NF) before the growth of Ni-MOF to tackle these issues. PANI not only improves the conductivity but also promotes the formation of Ni-MOF nanosheet arrays and ensures good mechanical adhesion. The as-prepared Ni-MOF/PANI/NF exhibits a high areal capacitance (3626.4 mF cm⁻² at 2 mA cm⁻²) and good rate capacity (71.3% at 50 mA cm⁻²). Moreover, an asymmetric supercapacitor (ASC) device using Ni-MOF/PANI/NF and activated carbon (AC) can deliver a maximum energy density of 45.6 W h kg⁻¹ (850.0 W kg⁻¹) with excellent cycling stability (capacitance retention of 81.6% after 10 000 cycles), outperforming most of the reported pristine MOF-based ASC devices.