A New High-Current Electrochemical Capacitor Using MnO[sub.2]-Coated Vapor-Grown Carbon Fibers

Composites of MnO[sub.2] nanosheet arrays vertically grown on the surface of vapor-grown carbon fibers (VGCFs) are fabricated by a low-temperature redox reaction between KMnO[sub.4] and the VGCFs. An assembled AC/0.5 M K[sub.2] SO[sub.4] /MnO[sub.2] @VGCF electrochemical capacitor exhibits a higher specific capacitance, as well as a better rate capability, at a fast-current density compared to the capacitor built on hydrothermally prepared, standalone MnO[sub.2] . Electrochemical tests revealed that VGCFs act as a conducting matrix, which effectively improves the conductivity of MnO[sub.2] nanosheets during cycling.