Unlike batteries, supercapacitors can charge and discharge much more rapidly — a boon for impatient drivers who want to be able to charge their electric cars quickly.
The key to supercap performance is electrodes with a large surface area and high conductivity that are inexpensive to manufacture. Carbon aerogels satisfy the first two requirements but have significant drawbacks. Some are made from phenolic precursors which are inexpensive but not environmentally friendly. Others are made from graphene and carbon nanotube precursors but are costly to manufacture.
Researchers at the University of Science and Technology of China have discovered a new process that is low cost and sustainable using nanocellulose, the primary component of wood pulp that gives strength to the cell walls of trees.
Once extracted in the lab, it forms a stable, highly porous network which when oxidized forms a micro-porous hydrogel of highly oriented cellulose nano-fibrils of uniform width and length.
A lot of tweaking went on in the lab to get things to work just right. Eventually, it was found that heating the hydrogel in the presence of para-toluenesulfonic acid, an organic acid catalyst, lowered the decomposition temperature and yielded a “mechanically stable and porous three dimensional nano-fibrous network” featuring a “large specific surface area and high electrical conductivity.
The chemists have been able to create a low cost, environmentally friendly wood-based carbon aerogel that works well as a binder-free electrode for supercapacitor applications with electro-chemical properties comparable to commercial electrodes currently in use. Now the hard work of transitioning this discovery from the laboratory to commercial viability will begin.