Cellulose/carbon nanotube/MnO2 composite electrodes with high mass loadings for symmetric supercapacitors

In this study, we used a simple method for the homogeneous deposition of nanostructured manganese dioxide (MnO2) on a regenerated cellulose/functionalized CNT (f-CNT) matrix through the direct redox reaction between potassium permanganate and carbon nanotubes (CNTs) in an acidic medium. Because of the unique porous structures, large surface areas, and excellent conductivities, the cellulose/f-CNT composite film was an excellent substrate for the incorporation of MnO2 nanostructures, forming cellulose/f-CNT/MnO2 composite films. With the synergistic effects from the f-CNTs with excellent conductivity and the MnO2 with high theoretical capacitance, the cellulose/f-CNT/MnO2 composites exhibited outstanding electrochemical performance when employed as freestanding electrodes for supercapacitors. The areal capacitance increased upon increasing the content of MnO2 on the f-CNT/cellulose (7/3, w/w) composite film; the maximal areal capacitance of 7956 mF cm–2 was attained for the cellulose/f-CNT/MnO2-120 composite with a high MnO2 content of 15.93 mg cm–2. The symmetric supercapacitor assembled by employing the cellulose/f-CNT/MnO2-120 composite film exhibited a high capacitance of 1812 mF cm–2, a maximum energy density of 251.66 µW h cm–2, and a maximum power density of 24.85 mW cm–2. The simple, inexpensive, and environmentally benign nature of this synthetic procedure allows it to be scaled up readily for bulk synthesis.