Solid solution-typed defect concept in forming multivalent cations- and oxygen vacancy-filled MnCo₂O_4-z spinel bifunctional electrodes for innovative symmetrical supercapacitor

Oxygen vacancies-filled MnCo2O4-z (MCO) nanosheets prepared by a two-step process with varied NH4F content have been investigated. MCO prepared with NH4F at 10 mmol (MCO-10) shows excellent to be used not only for cathode and anode but also for a symmetric supercapacitor cell (SSC). This MCO-10 electrode as a cathode not only reaches a high specific capacitance (C-s) of 7249 F/g at 1 A/g but also performs a high value of 2515 F/g at 1 A/g as an anode. An enlarged SSC of 5 x 5 cm(2) is developed. One and five light-emitter-diode (LED) bulbs and commercial 100 F supercapacitor devices are tested to authenticate our reported data. The outstanding performance of nonstoichiometric MCO spinel involving the OH- dipole interaction with oxygen vacancies, chemical redox reaction, multiple cationic valence states, and oxygen vacancies-filled defective structure are all connected with the solid solution-typed defect concept to form bifunctional spinel.