High-performance carbon-based supercapacitors using Al current-collector with conformal carbon coating

Al current-collector with porous surface is coated with a conformal carbon (C) layer via a chemical vapor deposition process in CH4 at 600 °C. X-ray photoelectron spectroscopy analysis indicates that the coating process leads to the replacement of native aluminum oxide with a composite coating consisting of an Al4C3 interfacial layer and a C top layer. Activated C-based supercapacitors employing the resulting C-coated Al current-collectors have exhibited remarkably enhanced high-rate performance, and the enhancement can be attributed to two accounts. Firstly, the current-collector/active-layer interface resistance is reduced due to removal of the insulating oxide layer and improved adhesion of the active-layer on the current-collector. Secondly, the presence of the conducting C layer shortens the effective current conduction distance from the solid-electrolyte interface to the current-collector, leading to reduced charge-transfer resistance within the active-layer. Combining the C-coated Al current-collector with a C fiber active-layer that contains a large mesoporous pore volume (0.4 cm3 g−1) has resulted in high-performance supercapacitors that exhibit, for instance, a cell specific energy of 18 Wh Kg−1 at 25 °C or 7 Wh Kg−1 at −10 °C under a cell specific power of 25 KW Kg−1.