The electric and hybrid vehicle market, though not yet making waves here in the UK, is burgeoning in the US and is set to explode globally in the coming decades. Currently, the best-selling vehicles, those from Japanese manufacturer Toyota, are powered by custom battery packs made up of nickel-metal hydride cells, while newer rechargeable cars are embracing lithium-ion chemistry.
However, as seen in the vast number of devices that are powered by such cells, including laptops and mobile phones, lithium-ion has its own deficiencies. Cells currently provide vehicles with no more than 100 miles per cycle, and when compared to conventional fuel, they perform poorly on both cost and longevity.
Industry insiders are clear that current lithium-ion chemistry is not the long-term answer for rechargeable and hybrid vehicles and so are working on a range of alternatives.
Research centres across the US have made what they hope are real breakthroughs in battery technology, with some projects allowing for prototype custom battery packs to be tested in electric and hybrid vehicles.
From Solid Energy Systems in Massachusetts, who have created an ‘anode-less’ prototype that has not yet been tested in vehicles, to a graphite copper combination coming out of Colorado State University, cell manufacturers are looking to experiment with various materials to find a chemistry that improves on lithium-ion’s questionable costs and miles per cycle.
Two new lithium-based cells showcasing a similar idea at their cathode are the Massachusetts Institute of Technology’s nanotube electrode cell and the aforementioned copper nanowire cathode cell from Colorado State University.
Both utilise microscopic particles on their cathodes (hollow carbon threads in the former and small copper wires in the latter) in order to increase the transfer and storage of ions. Though both chemistries are still not ready for mainstream use in hybrids and electric vehicles, there is hope that they will leave lithium-ion cells standing in terms of capacity.
Lithium again plays a role in two more future hopefuls: a lithium-air battery from IBM and Lawrence Berkeley National Laboratory’s lithium silicon polymer. The first is known as a ‘breathing battery’, and IBM have used carbon electrodes whose ions react with oxygen without depleting the medium of the electrolyte, allowing for more capacity than lithium-ion chemistry.
By contrast, the lithium silicon polymer combines silicon electrodes with a special coating so that their expansion and contraction does not cause the structural problems that can bedevil components of other cell chemistries.
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