Flower-like NiFe layered double hydroxides coated MnO2 for high-performance flexible supercapacitors

- Hierarchical MnO2@NF/NiFe LDHs were prepared.
- High areal capacitance: 4274.4 mF cm−2 at the current density of 5 mA cm−2.
- Excellent cycling stability: 95.6% capacitance retention after 1000 cycles.
- An energy density of 24.6 mWh cm−2 at a power density of 350 mW cm−2.

The flower-like NiFe layered double hydroxides loaded on Ni foam (NF/NiFe LDHs) are synthesized via one-pot hydrothermal method and the synthesized NF/NiFe LDHs are further coated with MnO2 nanosheets (MnO2@NF/NiFe LDHs) through an extra hydrothermal process. The excellent supercapacitor performance of MnO2@NF/NiFe LDH has been observed with a high capacitance of 4274.4 mF cm−2 at 5 mA cm−2 and a capacitance retention of 95.6% after 1000 cycles from a traditional three-electrode system. A low-cost flexible asymmetric supercapacitor has also been designed and fabricated using MnO2@NF/NiFe LDH as anode and active graphene as cathode. The working voltage window of this asymmetric supercapacitor is up to 1.4 V and the asymmetric supercapacitor delivered an energy density of 24.6 mWh cm−2 at 350 mW cm−2. These outstanding supercapacitor performances of the synthesized composite MnO2@NF/NiFe LDHs are attributed to the combination of unique NiFe layered double hydroxides structure and higher conductivity of MnO2 nanosheets.

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