printed solar power with printed all-organic supercaps_demonstrator award at Lopec 2018

Project0-3D: Supercapacitors from nanocellulose

Competence Areas at RISE ICT
0-3D: Supercapacitors from nanocellulose

A flexible and ecofriendly supercapacitor (SC) system based on conductive polymer electrodes.

The SC can be manufactured by a combination of printing, coating and lamination steps. The aim is to produce large area SCs for massive energy storage applications, such as intermediate storage for renewable energy sources as well as to balance the power grid from the fluctuations that these sources produce.

The SC comprises of two electrodes with aluminium current collectors on plastic substrates, protective carbon layers and the active material layer. Between the electrodes, a semi-solid electrolyte paper is laminated and the cells are sealed using an adhesive. The aluminium electrodes are patterned using a method called dry phase patterning. To protect the metal from corrosion, a layer of carbon is screen printed on top of the collector electrodes. The active material, which is a composite of a conductive polymer (PEDOT:PSS) and cellulose fibres, is subsequently coated on the carbon. The electrolyte is composed of a gelled ionic liquid soaked into separator papers.

This type of large area SCs represent an alternative to using batteries in massive energy storage applications. Since the SCs don’t contain any hazardous materials, they are more environmentally friendly than batteries which often contain toxic metals that can leak out. Except for the metal collectors, all materials used are organic and easy to dispose of. Since aluminium is easily recycled, even the collectors could potentially be reused.

Besides cellulose, which forms a porous network onto which the conductive polymer can self-organize, other forest-based products can be integrated into the active material to enhance the capacitors performance. One such material is Lignosulfonate, which is derived from wood. This inexpensive organic molecule can store electrical charge at a high energy density. However, since it is an electrical insulator, it can only be used together with a conductive network such as that which is provided by a conductive polymer.

Target markets and applications

The capacitors could range from really small, all the way to large wind/solar-power balancing circuits. Target audience for the technology is hence the electronics industry, the automotive industry and energy companies.

Looking at Tesla, batteries, renewables, the target market is potentially huge for balancing circuits which are cheap, environmentally friendly and rational to produce, making use of natural earth-surface-level biological products (wood!). Looking at other market segments, we believe small disposable and potentially biodegradable systems may become a very important market overall for printed electronics, in medtech and pharma among others.

Large-scale batteries based on organic electronic polymers and biopolymers from the forest produced using ordinary paper machines is a vision for the newly founded spin-off company Ligna Energy in Sweden, and the proposed demonstrator could be considered an early-stage demonstrator for the entire vision.

Printed electronics as an enabling technology

Printed electronics enables large area and high throughput fabrication which will be necessary if the supercapacitor is to be used to massive energy storage applications where large volumes will be required. We also believe there are alternate scenarios of producing environmentally friendly batteries and/or supercapacitors in use-cases with all-disposable miniature systems.