Copper nanoparticles spaced 3D graphene films for binder-free lithium-storing electrodes

Copper nanoparticles (Cu NPs) spaced reduced graphene oxide (rGO) films are fabricated by integrating electrophoresis deposition (EPD) with thermal H-2 annealing. The Cu NPs are formed through thermal aggregation and reduction of Cu(II) ions which are counter cations of GO. By tuning the annealing temperature from 400 to 850 degrees C, the mean diameter of the Cu NPs increases from 35 to 124 nm. Chemical characterizations reveal that the EPD technique may partially remove the O-containing groups of the GO film, while complete removal of the O-containing groups and effective repair of the graphene defects are achieved by thermal H-2 treatment. With the implantation of Cu NPs, the resultant rGO/Cu NP films exhibit high porosity and amazing electric conductivities, enabling their direct use as lithium-ion battery (LIB) electrodes (vs. Li/Li+) without a general current collector, binder, and other additives. This novel LIB has a high charge/discharge capacity (>463 mA h g(-1)), an excellent reversibility, and a high coulombic efficiency (nearly 100%) for 300 cycles at a current density of 0.2 A g(-1). It also exhibits good rate capacity: 849 mA h g(-1)@.0.1 A g(-1), 618 mA h g(-1)@0.2 A g(-1), 516 mA h g(-1)@0.3 A g(-1), and 470 mA h g(-1)@.0.5 A g(-1). Our new technique provides advanced design strategies for high performance LIBs and ultracapacitors, which might be used for mobile phone and electrical vehicles with unprecedented performances.