Facile one-step synthesis of agaric-like cobalt–manganese oxide nanosheets for supercapacitor with excellent long-term stability

A facile one-step method is developed to synthesize homogenous agaric-like cobalt–manganese oxide nanosheets with excellent supercapacitive performance in this study. The optimal sample shows morphologies of equiaxed spheres with diameter of 300 ± 30 nm, which consists of agaric-like nanosheets with thickness of approximate 3 nm. The active material is composed of MnO₂ and Co₃O₄ which is identified by the results of high resolution transmission electron microscopy, X-ray diffraction pattern and X-ray photoelectron spectroscopy spectrum. The as-prepared sample owns a high specific capacitance of 683 F g⁻¹ at a scan rate of 5 mV s⁻¹, while the value still retains 64% at a fast scan rate of 100 mV s⁻¹ (436 F g⁻¹). Moreover, the sample exhibits a remarkable long-term durability which can keep 83.5% capacitance retention over 20,000 charge/discharge cycles at a current density of 5 A g⁻¹. These results suggest that the thin agaric-like nanosheets plays an important role in the excellent performance for supercapacitor. The investigation offers a simple way to prepare agaric-like cobalt–manganese oxide which has potential applications in supercapacitors with excellent long-term stability.