Courtesy Alex WalkerResearchers from Rice University have rethought the battery. Typically, batteries are made up of 5 layers: a positive and negative electrode, each with a metal current collector, and a polymer separator. These layers are manufactured in sheets and then rolled into cylinders. Rice researchers realized that each of these layers were available, or could be created, in sprayable form. They used lithium titanium oxide and lithium cobalt oxide for the anode and cathode, existing metallic paints and carbon nanotube mixtures for the current collectors, and a chemical hodge-podge with a very lengthy name for the separator layer. The result is an ultra thin (a fraction of a millimeter thick) lithium ion battery.
In their first experiment, researchers sprayed each consecutive layer onto nine bathroom tiles, topped with a solar cell. The resulting batteries were able to power 40 LEDs for six hours.
In its current state, this method is too toxic to be used outside a controlled environment, but with a little tweaking, a safe alternative will be found. At that point, any surface could be a battery!
Made from 90 percent cellulose plus carbon nanotubes acting as electrodes, this paper like composite acts either as a battery or as a supercapacitor. No water is needed so this material can function from 100 below zero up to 300 degrees Fahrenheit.
Along with use in small hand held electronics, the paper batteries’ light weight could make them ideal for use in automobiles, aircraft, and even boats. The paper also could be molded into different shapes, such as a car door, which would enable important new engineering innovations.
“Plus, because of the high paper content and lack of toxic chemicals, it’s environmentally safe,” Shaijumon said.
The team has not yet developed a way to inexpensively mass produce the devices. The end goal is to print the paper using a roll-to-roll system similar to how newspapers are printed.
Details of the project are outlined in the paper “Flexible Energy Storage Devices Based on Nanocomposite Paper” published Aug. 13 in the Proceedings of the National Academy of Sciences.
Researchers are turning to nature to develop miniature batteries. In a recent issue of Science, it was reported that an international team of researchers, led by a group at Massachusetts Institute of Technology, has used a virus to build miniature batteries.
The batteries are being built from nanowires constructed from the M13 virus. Researchers modified the M13 virus’ genetic code so its outer coat would bond to certain metals. They incubated the modified virus in a cobalt chloride solution to allow cobalt oxide crystals to form uniformly along its length then sprinkled it with gold to produce electrical effects. Thus, the final nanowires worked as positive battery electrodes.
So why use a virus?
A virus is capable of forming tons of genetically similar copies of itself when grown under appropriate conditions. In the case of the M13 virus, it was harvested (or grown) in a bacteria. The M13 virus, in the bacteria environment, multiplied recreating tons of genetically similar copies of itself. Researchers reported that viruses form orderly layers yielding nanowires.
The researchers reported they have already used viruses to construct semiconductors and magnetic nanowires. Next on the agenda, they are hoping to use viruses to construct batteries ranging from the size of a grain of rice up to the size of a hearing aid battery. That’s pretty tiny!