Printed all-solid flexible microsupercapacitors: Towards the general route for high energy storage devices

A novel method for fabricating all-solid flexible microsupercapacitors (MSCs) was proposed and developed by utilizing screen printing technology. A typical printed MSC is composed of a printed Ag electrode, MnO ₂/onion-like carbon (MnO₂/OLC) as active material and a polyvinyl alcohol:H₃PO₄ (PVA:H₃PO₄) as solid electrolyte. A capacity of 7.04 mF cm^-2 was achieved for the screen printed MnO₂/OLC MSCs at a current density of 20 μA cm^-2. It also showed an excellent cycling stability, with 80% retention of the specific capacity after 1000 cycles. The printed all-solid flexible MSCs exhibited remarkably high mechanical flexibility when the devices were bent to a radius of 3.5 mm. In addition, all-solid MSCs were successfully demonstrated by screen printing technique on various substrates, such as silicon, glass and conventional printing paper. Moreover, the screen printing technique can be extended to other active materials, such as OLC and carbon nanotubes. This method provides a general route for printable all-solid flexible MSCs, which is compatible with the roll-to-roll process for various high performance active materials.