Bio-inspired graphene hierarchical structures as high-performance anode materials for Li-ion batteries
|(c,d) SEM images of honeycomb-patterned film prepared from 1 mg/mL of the GO/DODA complex on the silicon wafer; (e) cross-sectional SEM image of the honeycomb-patterned film. Credit: ACS, Yin et al. Click to enlarge.|
A team from Nanyang Technological University (China) has developed a scalable self-assembly strategy to create bio-inspired honeycomb-like hierarchical structures composed of functionalized graphene sheets to work as anodes in lithium-ion batteries.
Reported in a paper in the journal ACS Nano, the resulting electrodes with novel multilevel architectures simultaneously optimize ion transport and capacity, leading to a high performance of reversible capacity of about 1,612 mAh/g for the first process. The reversible capacity of the honeycomb electrodes was about 1,300 mAh/g in the initial 25 cycles and 1,150 mAh/g after 50 cycles.
The team evaluated the electrochemical performance of the honeycomb films in a proof-of-concept experiment using coin cells (2032) with a metallic Li counter electrode.
These results demonstrated that the prepared honeycomb electrodes have an intensive potential as a candidate of anode materials with high reversible capacity, good cycle performance, and high rate discharge/ charge capability.—Yin et al.
|Capacity versus cycle number for the honeycomb film at a current density of 50 mA/g showing charge (square, black) and discharge (circle, red) (the insets is the SEM image). Credit: ACS, Yin et al. Click to enlarge.|
With the honeycomb films, the large contact area between the electrode and electrolyte has advantages in good cycling performance and short path length for Li-transport, enabling the maximization of the potential of graphene for applications in energy storage, the authors noted.
The formed films described in the paper show high conductivity, high porosity, and robust chemical and mechanical stability. Furthermore, the authors report, the process to fabricate such hierarchical structures is facile, low-cost, green, and scalable.
Yin et al. note that there is no limitation for the size of the honeycomb films, which only depended on the volume of the solution and the size of the substrate. The films could be flexible if the substrate could be bent.
We successfully assembled the graphene sheets into bio-inspired honeycomb structures through the control of chemistry and assembly processes...The honeycomb graphene electrode exhibited a large reversible capacity (1150 mAh/g after 50 cycles) and an excellent cyclic performance, highlighting the advantages of bio-inspired hierarchical structures for energy storage applications in high-performance lithium-ion batteries.
Porosity was important for improving the capacity and cycling performance of disordered carbon anode materials, since the porous framework could significantly decrease the diffusion distance of the lithium ions into the disordered graphene layers, which can enhance the charge/discharge rate performance of rechargeable lithium batteries.
Finally, the fabrication process of such hierarchical structured graphene films was simple, low-cost, green, and scalable, which not only provides new opportunities for the rational design and engineering of electrode materials with enhanced performance, but also may find utility in various applications, including biological scaffold, catalysis, and sensors.—Yin et al.
Shengyan Yin, Yanyan Zhang, Junhua Kong, Changji Zou, Chang Ming Li, Xuehong Lu, Jan Ma, Freddy Yin Chiang Boey, Xiaodong Chen (2011) Assembly of Graphene Sheets into Hierarchical Structures for High-Performance Energy Storage. ACS Nano Article ASAP doi: 10.1021/nn2001728