Fabrication and characterization of a sandpaper-based flexible energy storage

- Carbon nanotubes prevent stacking of graphene sheets and act as spacers and binders.
- The sandpaper surface provides more electrode/electrolyte contact area.
- The gel electrolyte can prevent contact discontinuity in a supercapacitor.
- Sandpaper-based supercapacitors exhibit excellent flexibility and cycling stability.

In this paper, graphene and carbon nanotubes dispersed in a pectin solution are examined as a precursor for electrode fabrication for supercapacitor applications. The carbon nanotubes not only prevent the stacking of graphene sheets, but also act as spacers and binders. Dropping the hybrid conductive suspension onto sandpaper is found to form a sandpaper-based electrode that improves the specific capacitance of a subsequently fabricated supercapacitor because of its high surface area. In particular, the large contact surface of the sandpaper allows it to absorb more electrolyte ions and increases the number of ions assembled on the electrode surface. For the supercapacitor fabrication, replacing the liquid or solid electrolyte with a gel electrolyte prevents leakage and contact discontinuity. Therefore, a high-performance supercapacitor can be constructed with one separator coated with a gel electrolyte inserted between two fine-sandpaper-based electrodes, which can be assembled into a sandwich structure by hot pressing. Electrochemical analysis shows excellent cycle stability and flexibility of the fine-sandpaper-based supercapacitor. Because of the simple and low-cost assembly of this flexible and lightweight supercapacitor, it has potential applications in many energy storage fields, including wearable electronics and flexible products.

A sandpaper-based supercapacitor was assembled from two graphene/CNTs-coated fine-sandpaper electrodes and a PVA porous separator enclosed with H3PO4/PVA gel electrolyte, then packaged between two PET sheets by hot pressing. The galvanostatic charge/discharge curves obtained at a current of 0.10 mA over about 3000 cycles. The capacitance retention rates remained over 91% after this period, indicating the electrochemical stability of the supercapacitor. Thus, the supercapacitor based on the fine sandpaper electrode has a long lifetime and good cycling stability.191