Photograph by Jin-Song Hu
Would you choose to walk out the door, buckle your seat belt, and drive away in an electric car? If and when you do, it may be because of Yu-Guo Guo. The innovative nanostructures he has invented could transform the practicality of electric car batteries, making them smaller, more powerful, and less expensive than ever before.
"There is a serious need for sustainable energy sources to power electrical devices," says Guo. "Traditional sources such as fossil fuels cannot satisfy ever growing demands, and the carbon emissions associated with their use raise great environmental concerns."
Electric vehicles (EVs) attempt to answer those environmental concerns. The trick is finding a way to produce a better battery pack, the most important and expensive part of any EV. Batteries powerful enough to push cars long distances are big and heavy, and drive prices out of reach for most consumers. Alternatively, lowering the price by using smaller battery packs means limiting the car's range—another trade-off drivers balk at making.
The low cost and environmentally friendly features of lithium-ion batteries spark interest from automakers, yet lack the capability to quickly charge and effectively power electric vehicles. Guo believes the key to improving performance and lowering costs of those batteries lies in nanoparticles that can quickly absorb and store vast numbers of lithium ions, enhancing capacity and high-rate performance without causing deterioration in the electrode.
The idea of using nanostructures to make batteries isn't brand new, but the novel way Guo applies it means cars can take off fast when you accelerate, without draining energy storage capacity. The nanostructures he has invented at the Chinese Academy of Sciences significantly boost the performance of high-power lithium-ion batteries by enabling a more efficient flow of electric current. He calls them "3-D conducting nanonetworks," a dense network of high-conducting material that lets electrons reach every lithium storage particle for a far more powerful result.
"Compared with traditional lithium-ion batteries, this new high-power technology means batteries can be fully charged in just a few minutes, as quickly and easily as you can fill your car with gas," he says. "The advanced batteries recover more energy when cars stop, deliver more power when cars start, and enable vehicles to run longer."
Guo made it possible by finding a unique way to make a leading electrode material-lithium iron phosphate—easier and less expensive to work with for manufacturers. When milled into powder, lithium iron phosphate is a safer, more stable, better conductor, but the unruly powder flies into the air, making it harder and more expensive to deal with in manufacturing. Guo's approach corrals the particles by embedding them into larger particles made of porous carbon to maximize conductivity of electricity. He has since expanded the concept into other promising electrode materials, including lithium manganese oxide, lithium titanate, and silicon.
His innovation also helps solve the problem of big, heavy battery packs that have plagued the EV industry's ability to produce affordable vehicles. While a little more expensive to produce, his material will likely reduce battery costs per watt-hour since it is easier to incorporate into battery cells and doubles energy storage capacity by making full use of each storage particle. Guo says it's currently being used in electric cars and bikes, and he reports that cells using his solution could power about 3,000 car battery packs this year.
"Nanoscale isn't just small, it's a special kind of small," he explains. To put it into perspective, a nanometer is one billionth of a meter. It's the unit reserved for measuring the very tiniest parts of our world—molecules and atoms—visible only by extremely powerful microscopes. Nanotechnology turns nano-size structures into useful devices. For Guo, those practical applications are most fascinating in the fields of energy conversion and storage.
Life at this nanoscale may be impossible to see, but not to feel. Guo notes, "If you rub your finger along a surface, it's easy to distinguish velvet from steel, or wood from tar, because the different materials exert different forces on your finger. It's easier to slide it across a satin sheet than across warm tar because the tar exerts a stronger force, dragging your finger back. This is the idea behind the scanning force microscope, one of the tools that helped launch the nanoscience revolution. Its tiny mechanical probe gathers information by ‘feeling' the surface of nanoscale matter, allowing it to be imaged, measured, and manipulated."
Can technology based on thinking smaller and smaller rescue a world growing bigger and bigger? With the majority of the planet's seven billion people now living in urban areas, interest in ways to expand the clean green car economy has shifted into high gear. "I am glad to be part of work that can help reduce carbon emissions and use our planet's resources more sustainably," Guo states.
Looking into the future, he predicts that, "Five years from now, the electric vehicle market should be well established. In cities, up to 10 percent of cars could be EVs." His own contributions won't stop with better batteries. "I'm also interested in creating nanostructured materials for advanced energy conversion devices such as fuel cells and solar cells. Soon, I plan to combine a lithium-ion battery with a solar cell to invent a movable energy storage system."
The scale may be nano, but his thinking? It's huge.
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