Direct formation of a current collector layer on a partially reduced graphite oxide film using sputter-assisted metal deposition to fabricate high-power micro-supercapacitor electrodes

Abstract

When a reduced graphite oxide (RGO) freestanding film is fabricated on a supercapacitor cell via compression onto a current collector, there are gaps between the film and the current collector, even if the cell is carefully assembled. These gaps can induce increases in the electrical series resistance (ESR) of the cell, resulting in degradation of the cell's electrochemical performance. Here, to effectively reduce the ESR of the supercapacitor, metal sputtering deposition is introduced. This enables the direct formation of the current collector layer on a partially reduced GO (pRGO) film, the model system. Using metal sputtering, a nickel (Ni) layer with a thickness <1 mu m can be created easily on one side of the pRGO film. Good electrical interconnection between the pRGO film and the current collector can be obtained using a Ni layer formed on the pRGO film. The pRGO film sustains its film form with high packing density (similar to 1.31 g cm(-3)). Furthermore, the Ni-sputtered pRGO film with optimized Ni thickness exhibits remarkable enhancement of its electrochemical performance. This includes a superior rate capability and semipermanent cycle life compared with the untreated pRGO film. This is due to the significant decrease in the ESR of the film.