The rapid development of emerging smart power source-integrated electronics with superthinness, flexibility, lightweight and unusual shape diversity has ultimately accelerated the pursuit of new-concept energy storage systems. However, the conventional energy storage systems, such as batteries and supercapacitors, are manufactured by stacking and packaging cell components (two electrodes, separator, current collectors), followed by injection of liquid electrolytes.

As a result, these traditional systems have huge limitations of the fixed shapes, large size, bulk volume and heavy weight. Further, these power sources suffer from the leakage of liquid electrolytes, use of polymer binder, additive, thick separator, two pieces of flexible substrates. Hence, such traditional power sources can't keep pace with the progress of shape-tailored, flexible, smart integrated circuits.

The DICP scientists WU Zhongshuai and BAO Xinhe et al developed a versatile printable technology to fabricate arbitrary-shaped, all graphene-based planar sandwich supercapacitors with outstanding performance, excellent flexibility, superior integration, and applicable scalability. This work has been published online in ACS Nano.

The arbitrary-shaped printable graphene-based planar sandwich supercapacitors (denoted as PG-PSSs) were successfully fabricated on one single substrate. The PG-PSSs were based on a monolithic layer-structured film of electrochemically exfoliated graphene as two electrodes and nanosized graphene oxide as a separator. The PG-PSSs possess designable geometries and multiple functionalities far beyond those attainable by conventional supercapacitor technologies.

The printable technique allows us for the simplified mass production of planar sandwich supercapacitors with arbitrary shape. For instance, the supercapacitors with rectangle, hollow-square, "A" letter, "1" and "2" numbers, circle, and even complicated junction-wire shape were fabricated.

Besides, the diversity of graphene materials provided a platform for constructing monolithic PG-PSSs.

Also, the versatile-shaped PG-PSSs exhibited superior flexibility, very stable performance without capacitance degradation under different bending states. Importantly, the output capacitance of our devices can be easily modulated by covering gel electrolyte on the selected area of the electrode film. In addition, such PG-PSSs can be readily interconnected in parallel and series for designable integrated circuits with high output current and voltage.

Arbitrary shaped supercapacitors (Image by ZHENG Shuanghao and ZHAO Xuejun)

More importantly, this strategy for PG-PSSs is highly reliable and scalable, and compatible for various on-demand high-throughput printing techniques, in particular, high-resolution inkjet printing, 3D printing, and roll-to-roll process. Through further improvement of using advanced materials and electrolytes, our approach can be extended to other 2D materials for massive production of complex-shaped, fully printed PSSs. These PG-PSSs with designable functionalities are universally applicable to versatile-shaped flexible and wearable electronic devices.

The research work was financially supported by Thousand Youth Talents Plan of China, Ministry of Science and Technology of China, National Natural Science Foundation of China, Natural Science Foundation of Liaoning Province and DICP.