Chemical Routes to Graphene-Based Flexible Electrodes for Electrochemical Energy Storage - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 442

cycling numbers up to 1080 mAh g -1 , 307 F g -1 , 1080 A g -1 , and 10,000 cycles,
respectively, have been reported for prototype devices based on different types of
graphene papers, indicating that graphene-based flexible LIBs and supercapacitors
can indeed compete with many other energy storage devices. At present, there is still
an interesting ongoing development involving the design of flexible graphene-based
energy storage devices, either with or without other active materials. These types of
devices hold great promise for a number of new applications, which are incom-
patible with conventional contemporary battery and supercapacitor technologies.
Although graphene-based flexible electrodes have already become one of the
most promising candidates for bendable or roll-up electrochemical energy storage
devices, the following challenges still remain. First, high-quality graphene nano-
sheets are still required. New techniques have to be developed for producing
graphene nanosheets with highly controlled chemical and physical properties.
Second, the properties and functions of the electrodes depend strongly on their
microstructures. Therefore, the assembly behaviors of graphene sheets and with
other functional building blocks require more intensive investigation to achieve the
precise control. Finally, the applications of graphene-based flexible electrodes are
at their initial stages. They need to be studied systematically from both theoretical
and experimental aspects, for example, although many research works tested the
mechanical stability of different graphene papers, but the performance of graphene
papers built in a flexible device especially with liquid electrolytes after repeat
bending is still mistiness. With the multidisciplinary efforts from chemistry,
physics, and materials science, we believe that many applications of these mate-
rials will become reality in the near future.

Acknowledgments Financial support from the National Natural Science Foundation of China
(grant nos. 50872016, 20973033, and 51125009) and National Natural Science Foundation for
Creative Research Group (grant no. 20921002) is acknowledged.

References

1. Nishide H, Oyaizu K (2008) Materials science—toward flexible batteries. Science

319(5864):737-738
2. Tarascon JM, Armand M (2001) Issues and challenges facing rechargeable lithium batteries.
Nature 414(6861):359-367
3. Feng J, Sun X, Wu C, Peng L, Lin C, Hu S, Yang J, Xie Y (2011) Metallic few-layered VS 2
ultrathin nanosheets: high two-dimensional conductivity for in-plane supercapacitors. J Am
Chem Soc 133(44):17832-17838
4. Nyholm L, Nystrom G, Mihranyan A, Stromme M (2011) Toward flexible polymer and
paper-based energy storage devices. Adv Mater 23(33):3751-3769
5. Liu F, Song S, Xue D, Zhang H (2012) Selective crystallization with preferred lithium-ion
storage capability of inorganic materials. Nanoscale Res Lett 7:149
6. Pushparaj VL, Shaijumon MM, Kumar A, Murugesan S, Ci L, Vajtai R, Linhardt RJ,
Nalamasu O, Ajayan PM (2007) Flexible energy storage devices based on nanocomposite
paper. Proc Natl Acad Sci 104(34):13574-13577