The days of having to deal with large, bulky batteries may soon be coming to an end: a team of scientists from Rensselaer Polytechnic Institute in Troy, NY, have created a small paper-like battery that could herald a new generation of tiny, cheap and more eco-friendly energy sources. While attempts have been made in the past to build smaller, more flexible batteries — with varying degrees of success — scientists were never able to find an efficient way to combine a battery's different components into a thinner material.
Thinking a paper-like film might prove to be the ideal solution, the scientists created such a material by combining microscopic carbon nanotubes with cellulose dissolved in a liquid salt solution. The result was a film that resembled a piece of paper — white on one side and black with nanotubes on the other. Soaking the cellulose in a lithium hexafluorophosphate solution and covering the white side with lithium metal completed the novel battery — with the carbon nanotubes serving as one electrode and the lithium metal the other, the solution serving as the electrolyte and the cellulose functioning as the spacer.In test trials, the researchers found that each gram of paper could produce about 10 milliamps of current at 2 V. In addition to being completely integrated — unlike other flexible battery prototypes — multiple sheets of the battery could be stacked to increase the overall power. Furthermore, the battery can also function at different temperature extremes — as high as 150°C and as low as -70°C.
The researchers envision it being used in medical devices such as pacemakers and in cell phones, laptops and other consumer technologies. The remaining challenge now is finding a cost-effective way of making the batteries on a large scale.