Synthesis and electrochemical properties of Co-doped $$\hbox {ZnMn}_{2}\hbox {O}_{4}$$ hollow nanospheres

Spinel structure Co-doped $$\hbox {ZnMn}_{{2}}\hbox {O}_{{4}}$$ nanocrystals were successfully synthesized by a hydrothermal method. The effects of Co-doping concentration on the structure and electrochemical properties of the samples were investigated. The experimental results manifest that all samples exhibit a single-phase with a tetragonal structure, and morphologies are regular hollow microspheres. Cyclic voltammetry curves for all samples are similar to a rectangular shape with symmetric nature and no obvious redox peak. Galvanostatic charge–discharge curves were triangular and symmetric. Impedance spectra revealed that $$\hbox {Zn}_{1-x}\hbox {Co}_{{x}}\hbox {Mn}_{{2}}\hbox {O}_{{4}}$$ possess low resistance. Better electrochemical properties of the $$\hbox {ZnMn}_{{2}}\hbox {O}_{{4}}$$ electrode could be obtained when the Co-doping ratio is 0.3. $$\hbox {Zn}_{0.7}\hbox {Co}_{0.3}\hbox {Mn}_{{2}}\hbox {O}_{{4}}$$ exhibits much higher specific capacitance ( $$306\hbox { F g}^{-1}$$ ) at a scan rate of $$5\hbox { mV s}^{-1}$$ , and shows excellent cycling stability and retains 98.2% of its initial capacitance after 1000 cycles. The enhanced capacitive performance in this work can be attributed to the incorporation of Co ions doped into the $$\hbox {ZnMn}_{{2}}\hbox {O}_{{4}}$$ host lattice.