Paperweight: A battery made from cellulose
Saturday, October 17th, 2009
- Image by miheco via Flickr
A lightweight battery that could be used to identify and track objects
MANY an engineer has dreamed of making a battery as light, thin and flexible as paper. Such a device would dramatically trim the weight and dimensions of whatever it powered. Now Albert Mihranyan of Uppsala University in Sweden and his colleagues have built a battery that is, in essence, made of paper. It is lightweight and slim, and although still unsuitable for everyday use, could be employed to trace products supplied to shops or baggage passing through airports.
Batteries work by electrochemistry. Each contains two electrodes (an anode and a cathode) immersed in an electrolyte. A lithium-ion battery, the sort that powers mobile phones and laptop computers, typically has an anode made of carbon, a cathode made of lithium cobalt oxide and an electrolyte of a lithium salt in an organic solvent. When the battery is being charged, electrons are pumped into the cathode. That forces lithium ions to move away from it and into the anode. When the battery is being used, drawing the current pulls the lithium ions out of the anode and back to the cathode.
The device developed by Dr Mihranyan and his colleagues, which they describe in NanoLetters, is based on cellulose—the material from which paper is made. This is not any old cellulose, though. It is extracted not from trees or cotton, as the cellulose used in paper is, but from algae. Dr Mihranyan used algal cellulose because its fibres are wispier. That gives it a greater surface area and thus allows it to store more electric charge.
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