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Lithium-ion battery - Wikipedia, the free encyclopedia
Research claims

In April 2006, a group of scientists at MIT announced a process which uses viruses to form nano-sized wires. These can be used to build ultrathin lithium-ion batteries with three times the normal energy density.[55]

As of June 2006, researchers in France have created nanostructured battery electrodes with several times the energy capacity, by weight and volume, of conventional electrodes.[56]

In the September 2007 issue of Nature, researchers from the University of Waterloo, Canada, reported a new cathode chemistry, in which the hydroxyl group in the iron phosphate cathode was replaced by fluorine. [7] The advantages seem to be two-fold. First, there is less volume change in the cathode over a charge cycle which may improve battery life. Secondly, the chemistry allows the substitution of the lithium in the battery with either sodium or a sodium/lithium mixture (hence their reference to it as an Alkali-Ion battery).

In November 2007, Subaru unveiled their concept G4e electric vehicle with a lithium vanadium oxide-based lithium-ion battery, promising double the energy density of a conventional lithium-ion battery (lithium cobalt oxide and graphite).[8] In the lab, lithium vanadium oxide anodes, paired with lithium cobalt oxide cathodes, have achieved 745Wh/l, nearly three times the volumetric energy density of conventional lithium-ion batteries. [9]

In December 2007, researchers at Stanford University reported creating a lithium-ion nanowire battery with ten times the energy density (amount of energy available by weight) through using silicon nanowires deposited on stainless steel as the anode. The battery takes advantage of the fact that silicon can hold large amounts of lithium, and helps alleviate the longstanding problem of cracking by the small size of the wires. [10] To gain a tenfold improvement in energy density, the cathode would need to be improved as well; however, even just improving the anode could provide "several" times the energy density, according to the team. The team leader, Yi Cui, expects to be able to commercialize the technology in about five years.[11]. Having a large capacitive anode will not increase the capacity of the battery as predicted by the author when the cathode material is far less capacitive than the anode. However, current lithium-ion capacity is mainly limited by the low theoretical capacity (372 mAh g−1) of the graphite in use as the anode material, so improvement could be significant and would then be limited by the cathode material instead.

There are trials with metal hydrides as anode material for lithium-ion batteries. A practical electrode capacity as high as 1480 mAh g−1 has been reported.[57]

In April 2009 a report in New Scientist claimed that Angela Belcher's team at MIT had succeeded in producing the first full virus-based 3-volt lithium-ion battery.[58]

Recent studies performed at SUNY Binghamton by M. S. Whittingham et al. determined that vanadium ions can be incorporated into the iron-containing olivine structure of LiFePO4; a small amount of vanadium (around 5%) enhancing the rate capability of the LiFePO4 olivine cathode material. The resulting compound material had higher electronic and ionic conductivities, and they were of comparable magnitude. The doping reaction kinetics were optimal under reducing atmosphere during the synthesis of the LiFe0.95V0.05PO4 material.[59]

Battery tech has improved sigificantly over the last ten years. Back in 2000, Li-ion AA capacity was less than 1000mAh. Now it's getting on for three times that, with room for more improvement. It took about three years to 'productise' the original Li-ion batteries, so some of these developments should be along shortly - assuming they're cheap enough to mass produce.

Car batteries are a tougher problem because the wider temperature range and higher output currents mean more physical, electrical and chemical stress. Car batteries need to be able to handle freezing starts, and I'm not sure how many can do that yet.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Wed Sep 23rd, 2009 at 04:59:14 AM EST
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