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

Abstract

Copper nanoparticles (Cu NPs) spaced reduced graphene oxide (rGO) films are fabricated by integrating electrophoresis deposition (EPD) with thermal H₂ 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 °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 H₂ 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.