MnO@Corncob Carbon Composite Electrode and All-Solid-State Supercapacitor with Improved Electrochemical Performance.

Two corncob-derived carbon electrode materials mainly composed of micropores (activated carbon, AC) and mesopores/macropores (corncob carbon, CC) were prepared and studied after the anodic electrodeposition of MnO. The capacity of the MnO/activated carbon composite (MnO@AC) electrode did not noticeably increase after MnO electrodeposition, while that of the MnO/corncob carbon composite (MnO@CC) electrode increased up to 9 times reaching 4475 mF cm. An asymmetric all-solid-state supercapacitor (ASC) was fabricated using AC as the anode, MnO@CC as the cathode, and polyvinyl alcohol (PVA)/LiCl gel as the electrolyte. An ultrahigh specific capacitance of 3455.6 mF cm at 1 mA cm, a maximum energy density of 1.56 mW h cm, and a long lifetime of 10,000 cycles can be achieved. This work provides insights in understanding the function of MnO in biomass-derived electrode materials, and a green path to prepare an ASC from waste biomass with excellent electrochemical performance.