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April 06, 2006

Nanoscale, nanomaterials: Battery wire self assembled in viruses

By manipulating a few genes inside these viruses, the MIT team was able to coax the organisms to grow and self-assemble into a functional electronic device. The goal of the work, led by MIT Professors Angela Belcher, Paula Hammond and Yet-Ming Chiang, is to create batteries that cram as much electrical energy into as small or lightweight a package as possible. More details at MIT technology review. The viruses collect cobalt oxide and gold. The viruses are negatively charged. They are drawn into a layer between oppositely charged polymers to form thin, flexible sheets. Each virus, and thus the wire, is only 6 nanometers (6 billionths of a meter) in diameter, and 880 nanometers in length. The nanoscale materials supply two to three times the electrical energy for their mass or volume, compared to previous materials. according to wikipedia Specific energy density: 200 Wh/kg,
Volumetric energy density: 530 Wh/L. So three times would be 600Wh/kg and 1590 Wh/L.

They observed reversible capacity ranging from 600 to 750 mAh/g, which is about
twice that of current carbon-based negative electrodes.
The charge and discharge capacities stabilized at 600 mAh/g over 20 cycles. The cell was found to sustain and deliver 94% of its theoretical capacity at a rate of 1.12 C and 65% at a rate of 5.19 C, demonstrating the capability for high cycling rate. We believe that the power of the cell can be further increased by alternating stacks of nanowire monolayers and polymer layers of LPEI and PAA or other polyions. In addition, the
Au-Co3O4 hybrid nanowires should also increase the total capacity.

Other claims have been 300Wh/kg and 900 Wh/l Comparison of battery techhnology in 2004

They created 10-centimetre-long anode sheets. The genetic material added to the viruses can easily be interchanged, the researchers say, so it should be relatively simple to create other electronic components, including a positively charged battery electrode (cathode) using the technique. Belcher is currently investigating how to use viruses to create self-assembling solar cells.

An article that discusses Belcher vision. The battery reached the theoretical capacity for energy density with the material they created

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