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Posted: Jul 12, 2011
Beijing start-up makes nanostructures that could result In cheaper electric car batteries
(Nanowerk News) A Beijing startup called Wuhe is making electrode materials and batteries that could lower the cost of electric vehicles. The company uses nanostructures for battery materials that, like other recent nanostructures, let the materials deliver the large bursts of power needed for acceleration while maintaining energy storage capacity. But the Wuhe advance also makes the materials easier to work with than similar electrode materials, and as a result, it could cut battery-cell manufacturing costs by 10 percent.
Battery packs are the most expensive item on electric cars such as the Tesla Roadster and the Nissan Leaf. The cost either makes electric cars too expensive for most people, or it prompts automakers to use small battery packs, which limits the range of the cars.
To reduce battery costs and improve their performance, Wuhe founder Yu-Guo Guo, a professor of chemistry at the Chinese Academy of Sciences in Beijing, has developed new, low-cost ways to improve the properties of lithium-iron phosphate, one of the leading lithium-ion battery electrode materials, and other promising electrode materials.
Ordinarily, the conductivity of lithium-iron phosphate is too low to be useful. The conductivity can be increased by milling it into extremely fine nanoscale powdersóas companies such as A123 Systems do. Because the particles are small, electrons or lithium ionsóboth of which are necessary to create currentócan move in and out of them quickly. But this powder is difficult to work with, which raises manufacturing costs.
Guo's solution has been to incorporate iron-phosphate nanoparticles, which are easier to pack closely, and are less likely become airborne, but retain high conductivity. He isn't giving precise details, but he says the technology is based on some of his earlier published work. In one example of that work, he embedded the nanoparticles in larger particles made of porous carbon. The carbon conducts electricity well, and the pores host electrolyte materials that conduct lithium ions well.
Guo says the materials are only 10 to 20 percent more expensive to make than bulk lithium-iron phosphate. But they can deliver about twice as much power as the bulk material, and make twice as much of the energy in lithium-iron phosphate available, roughly doubling the energy storage capacity. Per watt-hour, the materials cost the same as other lithium-iron-phosphate electrode materials, he says. But since the material is easier to work with, it will cut the cost of incorporating the materials into battery cells.
Wuhe, which Guo founded at the end of last year, already has the capacity to produce 300 metric tons of electrode material a year, enough for about 30 million standard lithium-ion battery cells. It also makes battery cells, with the first application being electric bicycles. It can currently make enough cells for roughly 500 electric cars a year.
Jeff Dahn, professor of physics and chemistry at Dalhousie University, says that, based on the company's performance figures, the iron-phosphate batteries will be "very useful" and could perform better than the batteries used now in the electric Chevrolet Volt. And he predicts Wuhe will find a market.
Source: Chinese Academy of Sciences
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