Cu foam is a porous and stable substrate for electrodes in rechargeable batteries, such as zinc-air batteries. However, dendrite formation and self-corrosion of the anode in such batteries seriously reduce the battery performance. Hence, a new anode material is needed to address the current limitations of the existing materials.
A rGO@Cu foam, which is coated with a layered structure of reduced graphene oxide (rGO), was successfully used as the anode in rechargeable Li-metal batteries. Its rGO layer works as a protective film to inhibit the growth of Li dendrites and promotes uniform Li deposition. The rGO layer also exhibits superior properties in terms of cycling stability and CE as compared with commercial Cu foam and planar Cu foil.
As a result, the rGO@Cu foam anode shows a high cycling Coulombic efficiency as well as a stable SEI over 350 cycles at a current density of 1 mA cm-2. This is due to the extended reduced graphene layer which impedes the local current density and thus effectively controls the growth of Li dendrites.
The rGO@Cu foam exhibits much lower interfacial resistance than that of planar Cu foil, resulting in homogeneous current distribution on its surface. This can suppress the formation of Li dendrites, which is another potential hazard in Li-metal batteries.
The rGO@Cu foam electrode is shown to exhibit higher Coulombic efficiencies than 2D planar Cu foil and 3D commercial Cu foam in the symmetrical cell test at a current density of 1 mA centimeters. Moreover, the rGO@Cu foam electrode shows a high CE of 98.5% for over 350 cycles at a current density of 1.0 mA centimeters.