The familiar button battery is the workhorse of small electronics. While it is likely to continue to power our existing watches and calculators for a little while, it has become the limiting factor for many key design points of these devices. Like a shipping container in a world of instant messaging, it has no future. One company, Imprint Energy, has assembled the total assault package which might sound the death knell — a rechargeable, flexible, customizable, and printable battery that is cheaper, safer and more powerful.
The key technology developed by Imprint Energy is a polymer electrolyte that allows zinc-based batteries to be recharged. It prevents the formation of fingers which typically bridge across typical liquid electrolytes over time and make charging impossible. The flexible and customizable zinc anode, electrolyte, and metal oxide cathode of the battery are printed in the form of electrochemical inks. The printing process is similar to old-fashioned silk-screening where material is deposited in a pattern by squeezing it through a mesh over a template. While this screen printing is different from what we tend to think of nowadays as3D printing, the use of inkjets and other technologies are driving new convergent, hybrid techniques.
Platinum works well as a catalyst in hydrogen fuel cells, but it has at least two drawbacks: It is expensive, and it degrades over time. Brown chemists have engineered a cheaper and more durable catalyst using graphene, cobalt, and cobalt-oxide — the best nonplatinum catalyst yet.
The oxygen reduction reaction occurs on the cathode side of a hydrogen fuel cell. Oxygen functions as an electron sink, stripping electrons from hydrogen fuel at the anode and creating the electrical pull that keeps the current running through electrical devices powered by the cell. The reaction requires a catalyst, and platinum is currently the best one, but it’s very expensive and has a very limited supply, and that’s why you don’t see a lot of fuel cell use aside from a few special purposes.
Thus far scientists have been unable to develop a viable alternative. A few researchers have developed new catalysts that reduce the amount of platinum required, but an effective catalyst that uses no platinum at all remains elusive. Lab tests showed that the new graphene-cobalt material was a bit slower than platinum in getting the oxygen reduction reaction started, but once the reaction was going, the new material actually reduced oxygen at a faster pace than platinum. The new catalyst also proved to be more stable, degrading much more slowly than platinum over time. After about 17 hours of testing, the graphene-cobalt catalyst was performing at around 70 percent of its initial capacity. The platinum catalyst the team tested performed at less than 60 percent after the same amount of time.
Cobalt is an abundant metal, readily available at a fraction of what platinum costs. Graphene is a one-atom-thick sheet of carbon atoms arranged in a honeycomb structure. Developed in the last few years, graphene is renowned for its strength, electrical properties, and catalytic potential.