Accelerated redox conversion of an advanced Zn//Fe-CoO battery by heteroatom doping.

Herein, Fe-doped CoO (Fe-CoO) was prepared to solve the issues of poor electrical conductivity and the lack of active sites in CoO materials. Due to having similar radius and physical/chemical properties to Co, Fe is an ideal choice for doping CoO, as it can improve intrinsic conductivity without causing severe lattice distortion. Oxygen vacancies are gradually formed as doping reactions occur to maintain electric neutrality. Owing to the merits of oxygen vacancies in CoO, the distribution of the electrons is changed, thus optimizing the material's intrinsic charge/ion states and modifying the band gap by introducing impurity levels. Moreover, the surface area of Fe-CoO is 1.5 times larger than that of the original material. The synergistic effect promotes the electrochemical oxidation reduction reaction and improves the capacitance and cycling stability. Finally, such an advanced Zn//Fe-CoO battery exhibits a discharge-specific capacity of 171.97 mA h g, nearly eight times higher than that of the previous Zn//CoO battery (22.38 mA h g). In addition, the attenuation of the capacity was almost negligible after 9000 cycles.