(Co, Mn)(Co, Mn)2O4/CoO/Al8Mn5 three-phase nanoneedle array with crystalline-amorphous interfacial for enhanced capacitance

Introducing oxygen vacancies and dense crystalline-amorphous interfacial appropriately is a rational strategy to obtain high energy density cathode materials for supercapacitors. Herein, we synthesized (Co, Mn)(Co, Mn)2O4/CoO/Al8Mn5 three-phase nanoneedle array via a synchronous heterophase synthetic strategy. The obtained (Co, Mn)(Co, Mn)2O4/CoO/Al8Mn5 with oxygen vacancies and dense crystalline-amorphous interface exhibited outstanding specific capacitance of 1033.51 F g−1 at the current density of 1.0 A g−1 in 1 M KOH electrolyte, and yields 83.7 % capacitance retention after 5000 cycles. The density functional theory (DFT) calculations further reveal that the charge redistribution optimize adsorption energies at the oxygen vacancy interfacial sites. Thus, the preferential adsorption of intermediates is favored at these places. Combining the merits of crystalline and amorphous phases also could improve the cathode conductivity and enhance the concentration of active sites. Consequently, this work demonstrates that the simultaneous design of oxygen vacancies and dense crystal-amorphous interface sites is an effective strategy to develop ultrafast and high-energy pseudocapacitors.