Abstract
Conventional graphite anodes can hardly intercalate sodium (Na) ions, which poses a serious challenge for developing Na-ion batteries. This study details a novel method that involves single-step laser-based transformation of urea-containing polyimide into an expanded 3D graphene anode, with simultaneous doping of high concentrations of nitrogen (approximate to 13 at%). The versatile nature of this laser-scribing approach enables direct bonding of the 3D graphene anode to the current collectors without the need for binders or conductive additives, which presents a clear advantage over chemical or hydrothermal methods. It is shown that these conductive and expanded 3D graphene structures perform exceptionally well as anodes for Na-ion batteries. Specifically, an initial coulombic efficiency (CE) up to 74% is achieved, which exceeds that of most reported carbonaceous anodes, such as hard carbon and soft carbon. In addition, Na-ion capacity up to 425 mAh g(-1) at 0.1 A g(-1) has been achieved with excellent rate capabilities. Further, a capacity of 148 mAh g(-1) at a current density of 10 A g(-1) is obtained with excellent cycling stability, opening a new direction for the fabrication of 3D graphene anodes directly on current collectors for metal ion battery anodes as well as other potential applications.